TWI899305B - Protective film forming sheet and method for producing the same - Google Patents

Abstract

The present invention provides a protective film-forming sheet capable of sufficiently suppressing the suspension of waste material removal and a method for producing the protective film-forming sheet. The protective film-forming sheet of the present invention is a long sheet comprising: a protective film-forming film for forming a protective film; a first release film provided on one surface of the protective film-forming film; and a second release film provided on the other surface of the protective film-forming film. The protective film-forming sheet is characterized in that, when the peeling force when peeling the first release film from the protective film-forming film is set to F1, and the peeling force when peeling the second release film from the protective film-forming film is set to F2, the relationship F1>F2 is satisfied; when the adhesion force of the protective film-forming film to the stainless steel plate is set to F3, the relationship F2/F3≧0.10 is satisfied, and F2 is 30 mN/100 mm or greater.

Description

Protective film forming sheet and method for producing the same

The present invention relates to a protective film-forming sheet and a method for producing the same. In particular, the present invention relates to a protective film-forming sheet having a protective film suitable for use in protecting a workpiece such as a semiconductor wafer or a processed product such as a semiconductor chip obtained by processing the workpiece, and a method for producing the protective film-forming sheet.

In recent years, semiconductor devices have been manufactured using a mounting method known as flip-chip bonding. In this method, a semiconductor chip with a conductive surface with protruding electrodes, such as bumps, is mounted with the conductive surface side of the semiconductor chip flipped upside down (face down) and bonded to a chip mounting portion. As a result, the semiconductor device has a structure in which the backside of the semiconductor chip, where no circuitry is formed, is exposed.

Therefore, to protect semiconductor wafers from shocks during transport and other processes, a hard protective film made of an organic material is often formed on the back side of the semiconductor wafer. This protective film is formed using an uncured resin film (hereinafter referred to as a "protective film-forming film") as a precursor. The protective film-forming film is attached to the back side of the semiconductor wafer and is diced along with the wafer into wafers. Curing the protective film-forming film yields wafers with a protective film on the back side.

Patent Document 1 discloses a three-layer protective film-forming sheet 10. As shown in FIG1 , a protective film-forming film 11 is sandwiched between a first release film 12 and a second release film 13. The protective film-forming film 11 is laminated so as to be releasable from the first release film 12 and the second release film 13. When the peeling force for peeling the first release film 12 from the protective film-forming film 11 is F1, and the peeling force for peeling the second release film 13 from the protective film-forming film 11 is F2, the protective film-forming sheet of Patent Document 1 satisfies the relationship F1 > F2. The protective film-forming sheet 10 is a long strip that is stored and transported in a roll. In some cases, the protective film-forming sheet 10 is pre-punched to a shape roughly identical to the workpiece (a general term for adherends such as semiconductor wafers) before being attached to the workpiece. As shown in Figure 2, in this punched protective film-forming sheet, the protective film-forming film 16, punched to a predetermined closed shape, is sandwiched between two release films (12, 13). Figure 2 shows the state before the unnecessary portion 17 is removed.

The punched protective film-forming sheet is produced by punching the protective film-forming film into a predetermined closed shape using a punch die. The sheet is then used by removing the unnecessary peripheral portions 17 of the second release film 13 and the punched protective film-forming film 16. Specifically, the protective film-forming film 11 and the second release film 13 are completely punched into the predetermined closed shape, while the first release film 12 is not completely punched. The punched protective film-forming sheet is then obtained (Figure 3). This step is referred to as the "punching step." Next, a protective film-forming film 16 with a predetermined closed shape remains on the first release film 12, and the second release film 13 and the surrounding unnecessary portion 17 are removed (Figure 4). The protective film-forming film 16 is then attached to the workpiece. The step of removing the unnecessary portion 17 is called the "waste removal step."

Prior to the waste material removal step, a long strip of adhesive tape 18 is adhered to the second release film in contact with the unnecessary portion 17 and the second release film in contact with the punched protective film-forming film 16. During the waste material removal step, the unnecessary portion 17 can be removed simultaneously with the long strip of adhesive tape 18 and the second release film 13 (i.e., the second release film in contact with the unnecessary portion 17 and the second release film in contact with the punched protective film-forming film 16).

When removing the second release film 13 from the punched protective film-forming film 16, the relationship F1 > F2 is satisfied, making it easier to remove the second release film 13, while reliably leaving the punched protective film-forming film 16 on the first release film 12.

Protective film-forming sheets are required to perform punching processes stably (operational stability). In particular, operational stability is required during the waste material removal step, which removes unnecessary portions after punching the protective film. More specifically, during the waste material removal step, it is required that the waste material removal process not cease due to the inability to continuously remove the unnecessary portions 17 (hereinafter referred to as "waste material removal stoppage").

Prior Art Literature Patent Literature

Patent Document 1: International Publication No. WO2017/145735

The inventors of this invention have diligently studied the causes of waste material removal cessation and have come to the following conclusions.

As shown in Figure 5, after the punching process, the second release film 13 and the unused portion 17 of the protective film-forming film are removed in the waste removal process. The unused portion 17 is finally wound around a waste roller 20 and discarded. The unused portion 17 removed from the first release film is long and continuous. Before reaching the waste roller 20, a tension roller 19 controls the tension on the unused portion 17. These rollers 19 and 20 are typically made of stainless steel.

As the film passes over the tension roller 19, the unused portion 17 (i.e., the unwanted protective film-forming film) comes into contact with the tension roller 19. Because the peeling force F2 between the protective film-forming film 11 and the second release film 13 is set relatively weak, some or all of the protective film-forming film may peel off from the second release film 13 and transfer to the tension roller 19, contaminating it. In such cases, the system must be stopped and the tension roller 19 cleaned.

Furthermore, since the unused portion 17 is in continuous contact with the tension roller 19, if a large amount of protective film residue remains on the tension roller 19, it may cause operational malfunction of the tension roller 19. Furthermore, the residue adhering to the tension roller 19 may fall into the apparatus and contaminate the protective film-forming sheet as a product.

The present invention was made in view of the above-mentioned actual situation, and its object is to provide a protective film-forming sheet that can sufficiently suppress the suspension of waste material removal, and a method for producing the protective film-forming sheet.

The aspects of the present invention are as follows.

(1) A sheet for forming a protective film, which is a long sheet and comprises: a protective film forming film for forming a protective film, a first peeling film provided on one surface of the protective film forming film, and a second peeling film provided on the other surface of the protective film forming film, wherein when the peeling force when the first peeling film is peeled off from the protective film forming film is set to F1, and when the peeling force when the second peeling film is peeled off from the protective film forming film is set to F2, the relationship F1>F2 is satisfied, and when the adhesion force of the protective film forming film to the stainless steel plate is set to F3, the relationship F2/F3≧0.10 is satisfied, and F2 is 30 mN/100 mm or more.

(2) The protective film-forming sheet according to (1), wherein the weight of the epoxy resin that is liquid at room temperature contained in the protective film-forming composition is 12 parts by mass or less, based on the total weight of the protective film-forming composition constituting the protective film-forming film being 100 parts by mass.

(3) The protective film-forming sheet according to (1) or (2), wherein the weight of the filler contained in the protective film-forming composition is less than 55 parts by mass, based on the total weight of the protective film-forming composition constituting the protective film-forming film being 100 parts by mass.

(4) The protective film forming sheet according to any one of (1) to (3), wherein a cut is formed on the protective film forming sheet so that a portion of the protective film forming sheet has a predetermined closed shape when the protective film forming sheet is viewed from above, and the cut penetrates the protective film forming film in the thickness direction of the protective film forming sheet and reaches a portion of the first release film.

(5) A method for producing a punched protective film-forming sheet, comprising the step of forming a cutout in a portion of the protective film-forming sheet described in any one of (1) to (3) above so that the cutout has a predetermined closed shape, wherein the cutout penetrates the protective film-forming film in the thickness direction of the protective film-forming sheet and reaches a portion of the first release film.

According to the present invention, a protective film-forming sheet and a method for producing the same can be provided, which can sufficiently suppress the cessation of waste material removal.

10: For forming a protective film (this embodiment)

11: Protective film forming film

12: First peeling membrane

13: Second peeling membrane

14: Incision

16: Protective film formed by punching process

17: Useless part

18: Long strips of adhesive tape

19: Zhang Liyuan

20: Lift the discarded roller

21: Wafer

22: Cutting blade

30: Chip with protective film

31: Chip

32: Protective film

33: Convex electrode

50:Substrate

Figure 1 is a schematic cross-sectional view of a protective film-forming sheet according to an embodiment.

Figure 2 is a schematic cross-sectional view showing the protective film-forming sheet of the embodiment after punching.

Figure 3 is a schematic perspective view of the protective film-forming sheet after the punching process.

Figure 4 is a schematic perspective view showing the waste removal step.

Figure 5 is a cross-sectional view showing the second peeling film and the useless portion passing through the tension roller.

FIG6 is a schematic cross-sectional view of an example of a wafer having a protective film obtained by converting the protective film-forming film of this embodiment into a protective film.

Figure 7 is a schematic cross-sectional view illustrating the step of attaching the protective film forming sheet of this embodiment to a wafer.

Figure 8 is a schematic cross-sectional view illustrating the singulation step of a wafer with a protective film.

Figure 9 is a schematic cross-sectional view illustrating the step of placing a chip with a protective film on a substrate.

First, let's explain the main terms used in this manual.

The workpiece is a plate-shaped object to be processed, attached to the protective film formed in this embodiment. Examples of the workpiece include wafers and panels. Specifically, semiconductor wafers and semiconductor panels are examples. Examples of processed products of the workpiece include chips obtained by singulating a wafer. Specifically, semiconductor chips obtained by singulating a semiconductor wafer are examples. In this case, the protective film is formed on the backside of the wafer and chip.

The "front" of a workpiece such as a wafer refers to the side where circuits and protruding electrodes such as bumps are formed, while the "back" refers to the side where circuits and electrodes (such as protruding electrodes such as bumps) are not formed.

In this specification, for example, "(meth)acrylate" is used as a term to refer to both "acrylate" and "methacrylate," and the same applies to other similar terms.

A peelable film is a film that supports the protective film in a releasable manner. The film has no specific thickness limit and is used in the same manner as a sheet.

The mass ratios in the descriptions of protective film-forming compositions and release agent layer compositions are based on the active ingredients (solid components) and do not include solvents unless otherwise specified.

The present invention is described below based on specific implementation aspects.

(1. Protective film forming film)

As shown in Figures 1 and 3 , the protective film-forming sheet 10 of this embodiment is a long sheet comprising a protective film-forming film 11, a first release film 12 disposed on one surface of the protective film-forming film 11, and a second release film 13 disposed on the other surface. The protective film-forming sheet 10 is typically wound into a roll.

The protective film forming film 11 is adhered to a workpiece and formed into a protective film, thereby forming a protective film for protecting the workpiece or a processed product of the workpiece.

"Protecting" means rendering the protective film-forming film 11 sufficiently durable to protect a workpiece or a workpiece-based product. Specifically, when the protective film-forming film of this embodiment is curable, "Protecting" means converting the uncured protective film-forming film into a cured product. In other words, the protective film-forming film that has undergone protective filming is a cured product of the protective film-forming film and is distinct from the protective film-forming film.

After overlaying a workpiece on the curable protective film-forming film, the protective film-forming film is cured. This allows the protective film to be firmly bonded to the workpiece, resulting in a durable protective film.

When the protective film-forming film 11 does not contain a curable component and is used in an uncured state, the protective film-forming film of this embodiment is converted into a protective film when it is attached to a workpiece. In other words, the protective film can also be the same as the protective film-forming film.

When high protective performance is not required, the protective film-forming film does not need to be cured, so the protective film-forming film can be non-curing.

In this embodiment, the protective film-forming film is preferably curable. Therefore, the protective film is preferably a cured product. Examples of cured products include heat-cured products and energy-ray-cured products. In this embodiment, the protective film is more preferably a heat-cured product.

Furthermore, the protective film-forming film preferably has adhesive properties at room temperature (23°C) or preferably exhibits adhesive properties when heated. This allows the workpiece and the protective film-forming film to be adhered together when they are superimposed. This allows for secure positioning before the protective film-forming film is cured.

The protective film-forming film may consist of a single layer or a plurality of layers, two or more. When the protective film-forming film has multiple layers, these multiple layers may be identical or different, and the combination of layers constituting these multiple layers is not particularly limited.

In this embodiment, the protective film-forming film is preferably a single layer. If the protective film-forming film is composed of multiple layers, there is a risk of interlayer delamination due to differences in thermal expansion between layers during steps where temperature fluctuations occur (during reflow processing or when the device is used). A single layer can reduce this risk.

The thickness of the protective film-forming film is not particularly limited, but is preferably 100 μm or less, more preferably 70 μm or less, more preferably 45 μm or less, and particularly preferably 30 μm or less. When the thickness of the protective film-forming film is within this range, the adhesive force F3 (described later) tends to be reduced. Furthermore, the thickness of the protective film-forming film is preferably 5 μm or greater, more preferably 10 μm or greater, and more preferably 15 μm or greater. When the thickness of the protective film-forming film is within this range, the protective performance of the resulting protective film is improved.

The thickness of a protective film-forming film refers to the thickness of the entire protective film-forming film. For example, the thickness of a protective film-forming film composed of multiple layers refers to the total thickness of all layers constituting the protective film-forming film.

The following describes a protective film formed on a wafer, which is a workpiece. Specifically, the protective film formed by converting the protective film-forming film of this embodiment into a protective film is described using a wafer 30 with a protective film as shown in FIG6 .

As shown in Figure 6, the protective film wafer 30 has a protective film 32 formed on the back side of the wafer 31 (the upper side in Figure 6), and a protruding electrode 33 formed on the front side of the wafer 31 (the lower side in Figure 6).

Chip 31 has circuitry formed on its surface, and protruding electrodes 33 are formed on this surface to electrically connect to the circuitry. Chip 30, with a protective film, is positioned so that the surface with protruding electrodes 33 faces the chip mounting substrate. Then, through a predetermined heat treatment (reflow process), protruding electrodes 33 are electrically and mechanically connected to the substrate, allowing for mounting. Examples of protruding electrodes 33 include bumps and pillar electrodes.

(1.1 Peeling properties of protective film-forming films)

In this embodiment, when the peeling force when peeling the first peeling film 12 from the protective film forming film 11 is set to F1, and when the peeling force when peeling the second peeling film from the protective film forming film is set to F2, the relationship of F1>F2 is satisfied, preferably the relationship of F1>1.2×F2 is satisfied, more preferably the relationship of F1>1.5×F2 is satisfied, and even more preferably the relationship of F1>2×F2 is satisfied. If the peeling force F1 and the peeling force F2 satisfy the above relationship, the second peeling film can be easily removed from the punched protective film-forming film 16, and the punched protective film-forming film 16 can be reliably retained on the first peeling film 12. Therefore, the first peeling film 12 is a heavy peeling film with a strong peeling force, and the second peeling film 13 is a light peeling film with a weak peeling force. There is no particular upper limit for the peeling force F1, but in relation to the peeling force F2, it is preferably F1 < 10 × F2, more preferably F1 < 7 × F2, more preferably F1 < 5 × F2, and particularly preferably F1 < 3.5 × F2. When the peeling force F1 and the peeling force F2 satisfy this relationship, the unnecessary portion 17 can be easily removed from the first peeling film. Furthermore, F2 is preferably 30 mN/100 mm or greater, preferably 36 mN/100 mm or greater, more preferably 42 mN/100 mm or greater, further preferably 50 mN/100 mm or greater, and particularly preferably 60 mN/100 mm or greater.

In this embodiment, when the adhesion of the protective film-forming film to the stainless steel plate is set to F3, F2/F3 ≥ 0.10, preferably F2/F3 ≥ 0.15, more preferably F2/F3 ≥ 0.20, and even more preferably F2/F3 ≥ 0.30 are satisfied. By ensuring that F2 and F3 satisfy this relationship, when the second release film 13 and the unnecessary portion 17 are wound, even if the unnecessary portion 17 (i.e., the unnecessary protective film-forming film) contacts the stainless steel tension roller, the protective film-forming film will not remain attached to the tension roller, allowing the second release film 13 and the unnecessary portion 17 to be wound. There's no specific upper limit for F2/F3, but if F2 is too large, the secondary release film may not be removed smoothly when using a protective film. Therefore, F2/F3 ≤ 1.2 is preferred, F2/F3 ≤ 0.8 is more preferred, F2/F3 ≤ 0.6 is even more preferred, and F2/F3 ≤ 0.5 is particularly preferred.

The peeling force F1 is preferably 50 mN/100 mm or greater, more preferably 70 mN/100 mm or greater, even more preferably 90 mN/100 mm or greater, even more preferably 110 mN/100 mm or greater, and particularly preferably 130 mN/100 mm or greater. By keeping F1 within this range, unintended peeling of the protective film-forming film 11 and the first peeling film 12 can be suppressed.

Furthermore, the adhesion force F3 is preferably 500mN/100mm or less, more preferably 400mN/100mm or less, more preferably 350mN/100mm or less, and particularly preferably 300mN/100mm or less. By keeping F3 within this range, it is possible to prevent the unwanted portion 17 (i.e., unnecessary protective film-forming film) from remaining attached to the tension roller. The adhesion force F3 is preferably 40mN/100mm or greater, more preferably 80mN/100mm or greater, and even more preferably 120mN/100mm or greater. If F3 is too low, adhesion to the workpiece may be excessively reduced. When measuring the adhesion force F3 of the protective film-forming sheet to the stainless steel plate, the adhesion was measured approximately two minutes after the protective film-forming sheet was attached to the stainless steel plate. This is because the protective film-forming sheet is suspended from the time the second release film 13 and the unused portion 17 of the protective film-forming sheet are lifted up in the waste removal step until they are finally wound onto the waste roller. The unused portion is in contact with the tension roller for approximately two minutes.

(1.2 Protective Film Forming Composition)

The composition of the protective film-forming film is not particularly limited as long as the protective film-forming film possesses the aforementioned physical properties. In this embodiment, the composition constituting the protective film-forming film (protective film-forming film composition) is preferably a resin composition containing at least a polymer component (A), a curable component (B), and a filler (E). The polymer component is considered to be a component formed by a polymerization reaction of a polymerizable compound. Furthermore, the curable component is a component capable of undergoing a curing (polymerization) reaction. Furthermore, the polymerization reaction in the present invention also includes a condensation polymerization reaction.

Furthermore, components contained in the polymer component may also be curable components. In this embodiment, when the protective film-forming composition contains such components that are both polymer components and curable components, the protective film-forming composition is considered to contain both a polymer component and a curable component.

(1.2.1 Polymer Components)

The polymer component (A) imparts film-forming properties to the protective film-forming film and provides it with appropriate adhesiveness, allowing it to adhere reliably and evenly to the workpiece. The weight-average molecular weight of the polymer component is generally in the range of 50,000 to 2,000,000, preferably 100,000 to 1,500,000, and particularly preferably 200,000 to 1,000,000. If the weight-average molecular weight is too low, the peeling force of the peeling film and the adhesion to the stainless steel plate tend to increase. On the other hand, if the weight-average molecular weight is too high, compatibility with other components decreases, hindering uniform film formation. As such a polymer component, for example, acrylic resin, urethane resin, phenoxy resin, silicone resin, saturated polyester resin, etc. can be used, and acrylic resin is particularly preferably used.

In this specification, unless otherwise specified, "weight-average molecular weight" refers to the polystyrene-equivalent value measured by gel permeation chromatography (GPC). This method can be performed, for example, using a high-speed GPC apparatus "HLC-8120GPC" manufactured by TOSOH Corporation, connected in sequence to high-speed columns "TSK Gel Column H _XL -H,""TSK Gel GMH _XL ," and "TSK Gel G2000 H _XL " (all manufactured by TOSOH Corporation), with a column temperature of 40°C and a liquid feed rate of 1.0 mL/min, using a differential refractometer as a detector.

Examples of acrylic resins include (meth)acrylate copolymers composed of a (meth)acrylate monomer and a structural unit derived from a (meth)acrylic acid derivative. Preferred (meth)acrylate monomers include alkyl (meth)acrylates having an alkyl group with 1 to 18 carbon atoms, specifically methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate. Examples of (meth)acrylic acid derivatives include (meth)acrylic acid, glycidyl (meth)acrylate, and hydroxyethyl (meth)acrylate.

In this embodiment, glycidyl methacrylate or the like is preferably used to introduce glycidyl groups into the acrylic resin. The glycidyl-introduced acrylic resin improves compatibility with the epoxy resin (described later as a thermosetting component), resulting in a higher glass transition temperature (Tg) of the protective film after curing, and improved heat resistance. Furthermore, in this embodiment, hydroxyl groups are preferably introduced into the acrylic resin using hydroxyethyl acrylate or the like to control adhesion or adhesive properties to the workpiece.

The glass transition temperature of the acrylic resin is preferably -70°C to 40°C, more preferably -35°C to 35°C, even more preferably -20°C to 30°C, even more preferably -10°C to 25°C, and particularly preferably -5°C to 20°C. By setting the glass transition temperature of the acrylic resin within this range, the protective film formation and the fluidity of the protective film during heating can be suppressed, thereby facilitating the formation of a smooth protective film. If the glass transition temperature is too low, the peeling force of the peeling film and the adhesion to the stainless steel plate tend to increase. If the glass transition temperature is too high, compatibility with other components deteriorates, resulting in impaired uniform film formation and an excessive decrease in the peeling force F2 of the second peeling film.

When an acrylic resin has m types of structural units (m is an integer greater than or equal to 2), the glass transition temperature (Tg) of the acrylic resin can be calculated as follows. Specifically, the m types of monomers that derive the structural units in the acrylic resin are assigned a non-repeating number from 1 to m and named "monomer m." The glass transition temperature (Tg) of the acrylic resin can be calculated using the Fox equation shown below.

Wherein, Tg is the glass transition temperature of the acrylic resin, m is an integer greater than or equal to 2, Tgk is the glass transition temperature of the homopolymer of monomer m, Wk is the mass fraction of structural unit m derived from monomer m in the acrylic resin, and Wk satisfies the following formula.

In the formula, m and Wk are the same as above.

As Tgk, values listed in the Polymer Data Handbook, Adhesion Handbook, or Polymer Handbook can be used. For example, the Tgk of methyl acrylate homopolymer is 10°C, the Tgk of n-butyl acrylate homopolymer is -54°C, the Tgk of methyl methacrylate homopolymer is 105°C, the Tgk of 2-hydroxyethyl acrylate homopolymer is -15°C, the Tgk of glycidyl methacrylate homopolymer is 41°C, and the Tgk of 2-ethylhexyl acrylate is -70°C.

The polymer component content is preferably 5 to 80 parts by mass, more preferably 8 to 70 parts by mass, even more preferably 10 to 60 parts by mass, even more preferably 12 to 55 parts by mass, even more preferably 14 to 50 parts by mass, and particularly preferably 15 to 45 parts by mass, based on the total weight of the protective film-forming composition per 100 parts by mass. By keeping the polymer component content within this range, the amount of low-molecular-weight components that enhance the release film's release strength and adhesion to stainless steel sheets can be appropriately limited, thereby facilitating material design for the protective film-forming composition.

(1.2.2 Thermosetting Components)

The curable component (B) cures the protective film-forming film, forming a hard protective film. The curable component can be a thermosetting component, an energy-ray curable component, or a mixture thereof. The protective film-forming film of this embodiment, when cured by energy ray irradiation, contains fillers and colorants, which will be described later, resulting in reduced light transmittance. Therefore, for example, when the protective film-forming film is thick, energy-ray curing tends to be insufficient.

On the other hand, even when the thickness of a thermosetting protective film is increased, it can be fully cured by heating, thus forming a protective film with high protective performance. Furthermore, by using conventional heating equipment such as a heating oven, multiple protective film layers can be heated and cured at once.

Therefore, in this embodiment, the curable component is preferably thermosetting. In other words, the protective film-forming film of this embodiment is preferably thermosetting.

Whether a protective film-forming film is thermosetting can be determined as follows. First, a protective film-forming film at room temperature (23°C) is heated to a temperature higher than room temperature and then cooled back to room temperature, thereby forming a heated and cooled protective film-forming film. Next, at the same temperature, the hardness of the heated and cooled protective film-forming film is compared with the hardness of the unheated protective film-forming film. If the heated and cooled protective film-forming film is harder, the protective film-forming film is determined to be thermosetting.

Preferred thermosetting components include epoxy resins, thermosetting polyimide resins, unsaturated polyester resins, and mixtures of these resins. Thermosetting polyimide resins are a general term for low-molecular-weight, low-viscosity monomers or precursor polymers that form polyimide resins by thermal curing. Non-limiting examples of thermosetting polyimide resins are described in the Journal of the Fiber Society, "Fibers and Industry," Vol. 50, No. 3 (1994), pp. 106-118.

Epoxy resins, as thermosetting components, have the property of forming a three-dimensional network when heated, forming a strong coating. Various known epoxy resins can be used as such. In this embodiment, the molecular weight (formula weight) of the epoxy resin is preferably 300 to less than 50,000, 300 to less than 10,000, 300 to less than 5,000, or 300 to less than 3,000. Furthermore, the epoxy equivalent weight of the epoxy resin is preferably 50 to 5,000 g/eq, more preferably 100 to 2,000 g/eq, and even more preferably 150 to 1,000 g/eq.

Specific examples of such epoxy resins include glycidyl ethers of phenols such as bisphenol A, bisphenol F, resorcinol, phenol novolak, and cresol novolak; glycidyl ethers of alcohols such as butanediol, polyethylene glycol, and polypropylene glycol; glycidyl ethers of carboxylic acids such as phthalic acid, isophthalic acid, and tetrahydrophthalic acid; and glycidyl substituted aniline isocyanurate. Glycidyl or alkylglycidyl epoxy resins formed by active hydrogen bonded to nitrogen atoms, such as isocyanurate; so-called alicyclic epoxy resins, which have epoxy groups introduced by oxidizing carbon-carbon double bonds within the molecule, such as vinylcyclohexanediepoxide, 3,4-epoxycyclohexylmethyl-3,4-dicyclohexanecarboxylate, and 2-(3,4-epoxy)cyclohexyl-5,5-spiro(3,4-epoxy)cyclohexane-m-dioxane. In addition, epoxy resins having biphenyl skeletons, dicyclohexadiene skeletons, naphthalene skeletons, and the like can also be used.

Among these epoxy resins, when using epoxy resins that are liquid at room temperature (23°C), the weight of the epoxy resin that is liquid at room temperature is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 1 to 11 parts by mass, per 100 parts by mass of the total weight of the protective film-forming composition. A large amount of such a liquid epoxy resin tends to increase the peeling force when peeling the film from the protective film-forming film and the adhesion to the stainless steel plate.

Examples of epoxy resins that are liquid at room temperature (23°C) (liquid epoxy resins) include glycidyl ether of bisphenol A (bisphenol A-type epoxy resin), glycidyl ether of bisphenol F (bisphenol F-type epoxy resin), phenol novolac-type epoxy resins, naphthalene-type epoxy resins, ethylene glycol-type epoxy resins, and glycidylamine-type epoxy resins, which have smaller molecular weights.

When using a thermosetting component as the curing component (B), it is preferred to use a curing agent (C) as an auxiliary agent. As a curing agent for epoxy resins, a heat-activated latent epoxy curing agent is preferred. A heat-activated latent epoxy curing agent is a type of curing agent that is difficult to react with epoxy resins at room temperature (23°C) but becomes activated by heating to a certain temperature, allowing it to react with the epoxy resin. Methods for activating heat-activated latent epoxy resin curing agents include generating active species (anions and cations) through a chemical reaction involving heating; stably dispersing the curing agent in the epoxy resin at room temperature but becoming compatible with the epoxy resin, dissolving it, and initiating the curing reaction at elevated temperatures; utilizing molecular sieve-encapsulated curing agents that dissolve at elevated temperatures to initiate the curing reaction; and microencapsulation methods.

Among the methods exemplified above, the preferred method is one in which the material is stably dispersed in the epoxy resin at room temperature but becomes compatible with the epoxy resin, dissolves, and initiates a curing reaction at high temperatures.

Specific examples of heat-activated latent epoxy resin curing agents include various onium salts, dibasic acid dihydrazide compounds, dicyandiamide, amine adduct curing agents, and high-melting-point active hydrogen compounds such as imidazole compounds. These heat-activated latent epoxy resin curing agents may be used alone or in combination of two or more. In this embodiment, dicyandiamide is particularly preferred.

Furthermore, phenolic resins are also preferred as curing agents for epoxy resins. Condensates of phenols such as alkylphenols, polyphenols, and naphthols with aldehydes and the like can be used without particular limitation. Specifically, phenol novolac resins, o-cresol novolac resins, p-cresol novolac resins, t-butylphenol novolac resins, dicyclopentadiene cresol resins, poly(p-vinylphenol) novolac resins, bisphenol A novolac resins, or modified versions thereof can be used.

The phenolic hydroxyl groups in these phenolic resins can readily undergo an addition reaction with the epoxy groups in the aforementioned epoxy resins upon heating, thereby forming a cured product with high impact resistance.

The content of the curing agent (C) is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, even more preferably 0.2 to 15 parts by mass, and particularly preferably 0.3 to 10 parts by mass per 100 parts by mass of the epoxy resin. By setting the curing agent (C) content within this range, the network structure of the protective film becomes dense, facilitating the performance of the protective film in protecting the workpiece.

When dicyandiamide is used as the curing agent (C), it is preferred to use a curing accelerator (D) simultaneously. Preferred curing accelerators include imidazoles (imidazoles in which one or more hydrogen atoms are replaced by groups other than hydrogen atoms), such as 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole. Among these, 2-phenyl-4-methyl-5-hydroxymethylimidazole is particularly preferred.

The content of the curing accelerator is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, even more preferably 0.2 to 15 parts by mass, and particularly preferably 0.3 to 10 parts by mass, per 100 parts by mass of the epoxy resin. By setting the content of the curing accelerator (D) within this range, the network structure of the protective film becomes dense, thereby easily achieving the performance required to protect the workpiece as a protective film.

The combined content of the thermosetting component and curing agent is preferably 3-80 parts by mass, more preferably 5-60 parts by mass, even more preferably 7-50 parts by mass, even more preferably 9-40 parts by mass, and particularly preferably 10-30 parts by mass, per 100 parts by mass of the total weight of the protective film-forming composition. When the thermosetting component and curing agent are mixed in this ratio, the composition exhibits moderate adhesion before curing, allowing for stable application. Furthermore, after curing, the performance of the protective film is readily achieved.

Using low-molecular-weight compounds as thermosetting components and curing agents can increase the viscosity of the protective film, which in turn increases the peeling force of the release film and the adhesion to the stainless steel sheet. Therefore, it is preferable to select the type and amount of thermosetting components and curing agents within the above range to maintain an appropriate viscosity.

(1.2.3 Energy-ray curable components)

When the curable component (B) is an energy-ray curable component, the energy-ray curable component is preferably uncured, preferably has adhesive properties, and more preferably has both uncured and adhesive properties.

Energy-ray-curable components are components that cure by irradiation with energy rays and are used to impart film-forming properties and flexibility to the protective film.

As the energy-ray-curable component, for example, a compound having an energy-ray-curable group is preferably used. Examples of such compounds include well-known energy-ray-curable components.

Using low-molecular-weight compounds as radiation-curable components can increase the viscosity of the protective film, which in turn increases the peeling force of the release film and the adhesion to the stainless steel plate. Therefore, it is preferable to select the type and amount of radiation-curable components to maintain an appropriate viscosity.

(1.2.4 Filling Materials)

By incorporating a filler (E) into the protective film-forming film, the thermal expansion coefficient of the resulting protective film can be easily adjusted. By aligning this thermal expansion coefficient with that of the workpiece, the bonding reliability of the package formed using the protective film-forming film is further improved. Furthermore, by incorporating a filler (E) into the protective film-forming film, a hard protective film is obtained, further reducing the moisture absorption rate of the protective film, thereby further improving the bonding reliability of the package.

The filler (E) may be either an organic filler or an inorganic filler, but is preferably an inorganic filler from the perspective of shape stability at high temperatures.

Preferred inorganic fillers include powders of silica, alumina, talc, calcium carbonate, red iron oxide, silicon carbide, and boron nitride; beads obtained by sphericalizing these inorganic fillers; surface-modified products of these inorganic fillers; single-crystal fibers of these inorganic fillers; and glass fibers. Among these, silica and surface-modified silica are preferred. Surface-modified silica is preferably surface-modified using a coupling agent, more preferably using a silane coupling agent.

The average particle size of the filler is preferably 0.02 to 10 μm , more preferably 0.05 to 5 μm , and particularly preferably 0.10 to 3 μm .

By setting the average particle size of the filler to the above value, the workability of the protective film-forming composition becomes better. As a result, the quality of the protective film-forming composition and the protective film-forming film is easily stabilized.

Unless otherwise specified, the "average particle size" in this specification refers to the particle size at the 50% cumulative value (D50) in the particle size distribution curve obtained by laser diffraction scattering.

The upper limit of the filler content, based on the total weight of the protective film-forming film composition being 100 parts by mass, is preferably less than 80 parts by mass, more preferably less than 70 parts by mass, even more preferably less than 60 parts by mass, and particularly preferably less than 55 parts by mass. The lower limit is preferably 15 parts by mass or greater, more preferably 30 parts by mass or greater, even more preferably 40 parts by mass or greater, and particularly preferably 45 parts by mass or greater.

By setting the filler content to the above values, it is easier to control the peeling force of the release film and the adhesion to the stainless steel plate within an appropriate range. If the filler content is too low, the viscosity of the protective film-forming film increases, excessively increasing the peeling force and adhesion to the stainless steel plate. On the other hand, if the filler content is too high, the conformability of the protective film-forming film may decrease, causing the film to bend on a tension roll, making it difficult to maintain its shape. The protective film-forming film is prone to peeling or residues may remain on the roll.

Furthermore, the protective film-forming film preferably contains two or more fillers. In other words, the filler (E) is preferably a mixture of two or more fillers. "Containing two or more fillers" may include two or more fillers made of different materials or having two or more fillers with different average particle sizes.

In this embodiment, it is preferred to include two or more fillers with different average particle sizes. By including fillers with different average particle sizes in the protective film-forming film, it is easier to place the smaller filler within the gaps between the larger filler. As a result, the aforementioned effects can be achieved, and the adhesion between the protective film-forming films can be easily adjusted to within the aforementioned range.

When two or more fillers with different average particle sizes are included, the average particle size of the filler with the largest average particle size is preferably 1.5 to 100 times the average particle size of the filler with the smallest average particle size, more preferably 2 to 20 times, and even more preferably 3 to 18 times.

In addition, by observing the cross-section of the protective film or protective film-forming film, it can be confirmed whether the protective film or protective film-forming film contains two or more fillers with different average particle sizes.

(1.2.5 Coupling Agents)

The protective film-forming film preferably contains a coupling agent (F). This coupling agent not only improves the heat resistance of the protective film after curing, but also enhances the adhesion between the protective film and the workpiece and its water resistance (resistance to moisture and heat). Silane coupling agents are preferred due to their versatility and cost advantages.

Examples of the silane coupling agent include γ -glycidoxypropyltrimethoxysilane, γ -glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ- (methacryloyloxypropyl)trimethoxysilane, γ -aminopropyltrimethoxysilane, N-6-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-6-(aminoethyl)-γ-aminopropylmethyldiethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ -ureidopropyltriethoxysilane, γ -butylpropyltrimethoxysilane, γ- -propylmethyldimethoxysilane, bis(3-triethoxysilylpropyl)tetrasulfide, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriacetoxysilane, imidazole silane, etc. These silane coupling agents may be used alone or in combination of two or more.

When the total weight of the protective film-forming composition is 100 parts by mass, the content of the coupling agent is preferably 0.01 to 20 parts by mass, 0.1 to 10 parts by mass, 0.2 to 5 parts by mass, or 0.3 to 3 parts by mass.

(1.2.6 Colorants)

The protective film-forming film preferably contains a colorant (G). This shields the backside of the workpiece, such as a wafer, from electromagnetic waves generated within electronic devices, thus reducing malfunctions of the workpiece. Furthermore, any residual protective film-forming film adhering to the tension roll can be immediately detected with the naked eye.

As the colorant (G), for example, known colorants such as inorganic pigments, organic pigments, and organic dyes can be used. In the present embodiment, inorganic pigments are preferred.

Examples of inorganic pigments include carbon black, cobalt-based pigments, iron-based pigments, chromium-based pigments, titanium-based pigments, vanadium-based pigments, zirconium-based pigments, molybdenum-based pigments, ruthenium-based pigments, platinum-based pigments, ITO (indium tin oxide)-based pigments, and ATO (antimony tin oxide)-based pigments. Among these, carbon black is particularly preferred. Carbon black can block electromagnetic waves over a wide wavelength range.

The amount of the colorant (especially carbon black) blended in the protective film-forming film varies depending on the thickness of the protective film-forming film. For example, when the thickness of the protective film-forming film is 20 μm , the content of the colorant is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and even more preferably 0.05 to 4 parts by mass, based on 100 parts by mass of the total weight of the protective film-forming film composition.

The average particle size of the colorant (especially carbon black) is preferably 1-500 nm, particularly preferably 3-100 nm, and even more preferably 5-50 nm. If the average particle size of the colorant is within this range, it is easier to control the light transmittance within the desired range.

(1.2.7 Other additives)

The protective film-forming composition may contain other additives such as a photopolymerization initiator, a crosslinking agent, a plasticizer, an antistatic agent, an antioxidant, a dopant absorber, a thickener, and a release agent, as long as the effects of the present invention are not impaired.

In this embodiment, the stripping agent content is preferably less than 0.00099 parts by mass based on 100 parts by mass of the total weight of the protective film-forming composition. Excessive stripping agent content tends to reduce the reliability of adhesion between the protective film and the workpiece. Examples of stripping agents include alkyd stripping agents, silicone stripping agents, fluorine stripping agents, unsaturated polyester stripping agents, polyolefin stripping agents, and wax stripping agents.

(1.2.8 Controlling the peeling and adhesion forces of the protective film)

As described above, this embodiment is characterized by controlling the peeling force F1 when peeling the first peeling film 12 from the protective film-forming film 11, the peeling force F2 when peeling the second peeling film 13 from the protective film-forming film 11, and the adhesion force F3 of the protective film-forming film 11 to the stainless steel plate within specified ranges. As described above, these unique peeling characteristics can be controlled by the types and blending amounts of the components that make up the protective film-forming film.

If the weight-average molecular weight of the polymer component (A) is low, the peeling force tends to increase. If the glass transition temperature of the polymer component (A) is low, the peeling force tends to increase. Furthermore, if low-molecular-weight compounds are used as the curable component (B), curing agent (C), curing accelerator (D), or energy-ray-curable component, the peeling force tends to increase. If the amount of filler (E) blended is high, the peeling force tends to decrease.

The peeling force can also be controlled by partially curing the protective film-forming layer. For example, by partially curing the curable component (B), the peeling force can be reduced.

Furthermore, the peeling forces F1 and F2 can also be controlled by the peeling process of the first peeling film 12 and the second peeling film 13 . This will be described later.

(2. Sheet for forming protective film)

As shown in Figure 1, before use, the protective film-forming film is rolled up and stored in a three-layer structure consisting of a protective film-forming film 11 sandwiched between two release films (a first release film 12 and a second release film 13). The release films are peeled off when the protective film-forming film is used.

The protective film-forming sheet is long and is stored and transported in a roll. Other known protective film-forming sheets are those in which the protective film-forming film is pre-punched to a shape roughly identical to the workpiece. The punched protective film-forming film 16 of this punched protective film-forming sheet, punched to a predetermined closed shape, is sandwiched between two release films (12, 13) (Figure 2).

The first and second release films can be composed of a single substrate (monolayer) or two or more substrate layers. To control release properties, the substrate surface can be subjected to a release treatment. Specifically, the substrate surface can be modified, or a layer made of a different material can be formed on the substrate surface. In this embodiment, the first and second release films preferably comprise a substrate and a release agent layer. The release agent layer facilitates control of the physical properties of the surfaces of the first and second release films where the release agent layer is formed. In this embodiment, a coating containing the release agent composition described below is applied to one surface of a substrate, and the coating is dried and cured to form a release agent layer. This produces a first release film and a second release film.

(2.1 First peeling film 12)

The thickness of the first peeling film 12 is not particularly limited, but is preferably 30 to 100 μm , more preferably 40 to 80 μm , and even more preferably 45 to 70 μm .

By setting the lower limit of the thickness of the first release film 12 to the above value, it is possible to prevent the cutter from penetrating and severing the first release film 12 when the protective film-forming film 11 is cut using the cutter. Furthermore, after the protective film-forming sheet 10 is unwound and the protective film-forming film 11 is cut, the protective film-forming sheet 10 passes over rollers such as guide rollers within the apparatus before being transported to the next step. However, by setting the upper limit of the thickness of the first release film 12 to the above value, it is possible to prevent the protective film-forming film 11 from peeling off the first release film 12.

The thickness of the first release film 12 refers to the thickness of the entire first release film. For example, the thickness of a first release film composed of multiple layers refers to the total thickness of all layers constituting the first release film.

Examples of the base material for the first release film 12 include resin films and paper. Examples of resins for the resin film include polyethylene terephthalate, polyethylene, polypropylene, polybutylene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymers, polybutylene terephthalate, polyurethane, ethylene-vinyl acetate copolymers, polymer resins, ethylene (meth)acrylic acid copolymers, polystyrene, polycarbonate, fluororesins, low-density polyethylene, linear low-density polyethylene, and triacetyl cellulose. Examples of paper include premium paper, coated paper, glassine paper, and laminated paper. These base materials may be used singly or in combination. Among them, polyethylene terephthalate film is preferred due to its low cost and high rigidity.

At least one surface of the first release film 12 (the surface overlapping the protective film-forming film 11) can be stripped using a stripper layer composition. The thickness of the stripper layer is preferably 30 nm to 200 nm, more preferably 50 nm to 180 nm.

The surface elastic modulus (23°C) of the surface of the first release film 12 in contact with the protective film-forming film 11 is preferably 17 MPa or less, more preferably 14 MPa or less, even more preferably 13 MPa or less, and particularly preferably 12 MPa or less. The surface elastic modulus is an indicator of the ease with which a surface deforms. By setting the surface elastic modulus of the surface of the first release film 12 in contact with the protective film-forming film 11 within the above range, it is possible to suppress the occurrence of lifting (approximately 1 to 4 mm) between the protective film-forming film 11 and the first release film 12 when the punch is pressed and then pulled up during the punching process. This is believed to be due to the relatively soft surface of the first release film 12. Even under the compression of the die and the pressure during its release, the surface of the first release film follows the deformation of the protective film-forming film. By suppressing the occurrence of lifting, defects in the waste material removal step can be further reduced. There is no specific lower limit for the surface elastic modulus of the surface of the first release film 12 that contacts the protective film-forming film 11. However, if the surface elastic modulus is too low, the peeling force may increase. Therefore, it is preferably 3 MPa or higher, more preferably 4 MPa or higher, and particularly preferably 5 MPa or higher.

The surface elastic modulus of the surface of the first release film 12 in contact with the protective film-forming film 11 at 23°C can be measured using an atomic force microscope equipped with a cantilever. Specifically, the surface of the first release film 12 in contact with the protective film-forming film 11 is subjected to compression and tension by the cantilever to obtain a force curve. The obtained force curve is then fitted using the JKR theory to determine the elastic modulus, which is used as the surface elastic modulus of the present invention. The specific measurement method will be described in detail in the Examples below.

The first release film 12 can be easily obtained by performing a release treatment on one surface of the substrate. Preferred release agents for the release layer include, for example, alkyd release agents, silicone release agents, fluorine release agents, unsaturated polyester release agents, polyolefin release agents, and wax release agents. Silicone release agents are preferred, and a release agent containing a silicone release agent and a heavy-duty release additive is particularly preferred.

As a silicone release agent, a silicone release agent containing silicone having a basic skeleton of dimethyl polysiloxane can be used.

The silicone can be any of addition-reaction type, condensation-reaction type, or energy-ray-curable types such as UV-curable and electron-beam-curable, but addition-reaction type silicones are preferred. Addition-reaction type silicones offer high reactivity and excellent productivity. Compared to condensation-reaction type silicones, they also have advantages such as minimal post-production variation in peeling force and no curing shrinkage.

Specific examples of addition-reactive silicones include organopolysiloxanes having two or more alkenyl groups with 2 to 10 carbon atoms, such as vinyl, allyl, propenyl, and hexenyl, at the molecular ends and/or in the side chains. From the perspective of reducing the surface elastic modulus, it is preferable that the number of alkenyl groups in addition-reactive silicones is small.

When the total weight of the stripping agent composition (excluding the catalyst described below) is 100 parts by mass, the content of siloxane composed of dimethylpolysiloxane is preferably less than 100 parts by mass, more preferably less than 90 parts by mass, even more preferably less than 80 parts by mass, and particularly preferably less than 70 parts by mass.

When using this type of addition-reaction silane, it is preferred to use a crosslinking agent and a catalyst simultaneously.

Examples of crosslinking agents include organopolysiloxanes having at least two silicon atoms bonded to hydrogen atoms in one molecule. From the perspective of reducing the surface elastic modulus, the crosslinking agent content in the stripping agent composition is preferably low.

Specific examples of crosslinking agents include dimethylhydrosiloxyalkyl-terminated dimethylsiloxane-methylhydrosiloxane copolymer, trimethylhydrosiloxyalkyl-terminated dimethylsiloxane-methylhydrosiloxane copolymer, trimethylhydrosiloxyalkyl-terminated methylhydropolysiloxane, and poly(hydrosilsesquioxane).

Examples of catalysts include microparticles of platinum, microparticles of platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin compounds of chloroplatinic acid, and platinum group metal compounds such as palladium and rhodium.

By using this catalyst, the curing reaction of the stripper layer composition can be carried out more efficiently.

From the perspective of maintaining the surface elastic modulus within the above range and maintaining the peeling force F1 within an appropriate range, the content of the silicone release agent is preferably 30 to 100 parts by mass, more preferably 50 to 100 parts by mass, based on 100 parts by mass of the total weight of the release agent composition (excluding the catalyst).

The heavy-stripping additive is used to increase the peeling force F1 when peeling the first peeling film 12 from the protective film-forming film 11. Examples of heavy-stripping additives include silicone resins, silane coupling agents, and other organic silanes, with silicone resins being preferred.

As the silicone resin, for example, MQ resin is preferably used. It contains an M unit (a monofunctional siloxane unit [ _{R3SiO1 /2} ]) and a Q unit (a tetrafunctional siloxane unit [SiO4 _/2 ]. The three Rs in the M unit each independently represent a hydrogen atom, a hydroxyl group, or an organic group. To facilitate the suppression of siloxane migration, one or more of the three Rs in the M unit are preferably a hydroxyl group or a vinyl group, more preferably a vinyl group. To reduce the surface elastic modulus, the content of the silicone resin (particularly the MQ resin) in the stripper composition is preferably low.

When the total weight of the stripping agent composition (excluding the catalyst) is set to 100 parts by mass, the content of the heavy stripping additive is preferably 0 to 50 parts by mass, more preferably 5 to 45 parts by mass, and particularly preferably 10 to 40 parts by mass.

From the perspective of adjusting viscosity and improving coating properties on substrates, the peeling agent composition is preferably used as a coating agent containing a diluent solvent in addition to the various active ingredients mentioned above. In this specification, "active ingredient" refers to the components contained in the coating agent of the composition, excluding the diluent solvent.

Examples of diluent solvents include aromatic hydrocarbons such as toluene, fatty acid esters such as ethyl acetate, ketones such as methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and heptane. These diluent solvents may be used alone or in combination.

The concentration of the active ingredient (solid content) in the coating containing the peeling agent composition is preferably 0.3-10% by mass, more preferably 0.5-5% by mass, and even more preferably 0.5-3% by mass.

The stripper layer composition may contain additives commonly used in stripper layers, as long as the effects of the present invention are not impaired. Examples of such additives include dyes and dispersants.

(2.2 Second peeling membrane 13)

The thickness of the second release film 13 is not particularly limited. From the perspective of ease of release, it is preferably less than the thickness of the first release film 12, and more preferably thinner than the first release film 12. Therefore, the thickness of the second release film 13 is preferably 10 to 75 μm , more preferably 18 to 60 μm , and even more preferably 24 to 45 μm .

The base material for the second peeling film 13 is the same as that for the first peeling film 12. The peeling agent composition for the second peeling film 13 can be selected from the materials listed for the first peeling film 12, as long as it satisfies the relationship between F1 and F2. The materials listed as heavy-duty peeling additives are preferably present in a lower amount than in the first peeling film 12, or are not included.

Furthermore, by adding silicone oil to the peeling agent composition, the peeling force can be suppressed to a lower level, so silicone oil can also be used to adjust the peeling force.

(2.3 Controlling the Peeling Force of the Peeling Film)

In addition to the composition of the protective film-forming film described above, the peeling forces F1 and F2 can be controlled by the following factors.

． Type of resin material used as the main component of the stripping agent composition (silicon oxide, fluorine, long chain alkyl, etc.)

．Molecular weight of the resin material as the main component of the stripping agent composition

． The crosslinking density of the stripping agent composition (this crosslinking density is also affected by the type of crosslinking agent, its content before the crosslinking reaction, the density of functional groups that react with the crosslinking agent, etc.)

．Additives contained in the stripping agent composition (specifically, low molecular weight substances that are not cross-linked and/or difficult to cross-link)

．Thickness of the stripping agent layer

．Surface roughness of the contact surface between the release agent layer and the protective film forming film

．Thickness of the resin film as the base material

．Temperature when the peeling film and protective film form a film

． Pressure when the peeling film and protective film are bonded together

．The speed of the roller when the peeling film and the protective film are bonded together

(3. Method for Manufacturing a Protective Film-Forming Sheet)

The method for producing the protective film-forming film is not particularly limited. The film can be produced using the aforementioned protective film-forming composition or a composition obtained by diluting the protective film-forming composition with a solvent (a coating agent containing the protective film-forming composition). The coating agent can be prepared by mixing the components constituting the protective film-forming composition using a known method.

The protective film-forming sheet 10 of this embodiment can be obtained by applying the obtained coating agent to the release surface of the first release film 12 using a coating machine such as a roll coater, doctor blade coater, knife roll coater, air knife coater, die coater, rod coater, gravure coater, or curtain coater, and drying the coating agent. The second release film 13 is then laminated on the exposed surface of the protective film-forming film 11. The lamination order is not particularly limited, and the coating agent may be applied to the second release film. Alternatively, a coating agent can be applied to another resin film and dried, and the resulting protective film-forming film can be transferred to the first or second release film. Furthermore, after laminating these films, they can be heated and pressurized using a hot roller or the like. From the perspective of workability during production, a coating agent can be applied to the release surface of the first release film 12 and dried, and then a process release film can be laminated on the exposed surface of the protective film-forming film 11. After this, the process release film can be peeled off and the second release film 13 can be attached.

(4. Method for Manufacturing a Punching Sheet for Forming a Protective Film)

In the protective film-forming sheet 10 of this embodiment, the protective film-forming film 11 is preferably punched into a predetermined shape. Specifically, the protective film-forming sheet is preferably provided with a cutout 14 so that a portion of the protective film-forming sheet 10 has a predetermined closed shape when viewed from above.

This section describes a method for punching a protective film-forming sheet 10 to obtain a protective film-forming film having holes punched into a predetermined closed shape on a first release film 12.

(4.1 Punching Processing Steps)

First, prepare the unpunched protective film-forming sheet 10 shown in Figure 1. Using a punch (not shown), cut slits 14 are made from the side of the protective film-forming sheet 10 with the second release film 13, penetrating through the second release film 13 and the protective film-forming film 11 and reaching a portion of the surface of the first release film 12. Cutting a portion of the surface without completely cutting is called a half-cut. As a result, cuts 14 are formed on a portion of the surface of the protective film-forming sheet 10, forming a predetermined closed shape (see Figures 2 and 3). When the protective film-forming film is transferred to a semiconductor wafer, the predetermined closed shape is roughly the same as the wafer. That is, the cutout 14 is formed to have a shape roughly identical to the shape of the workpiece to which the protective film-forming film 11 is attached, or to the area where the protective film is to be formed. This step is called a "punching step."

The punching step separates the laminated body of the second release film 13 and the protective film-forming film 16, which are punched into a predetermined closed shape, and the laminated body of the second release film 13 and the protective film-forming film 16, which are formed by punching holes into predetermined closed shapes. The laminated body of the second release film 13 and the protective film-forming film 16 is formed at multiple locations along the longitudinal direction of the protective film-forming sheet 10.

(4.2 Waste Removal Step)

As shown in Figure 4, during the waste removal step, the second release film 13 (i.e., the portion of the second release film that is in contact with the unused portion 17 and the portion of the second release film that is in contact with the punched protective film-forming film 16) and the unused portion 17 are removed, leaving the punched protective film-forming film 16 remaining on the first release film 12. At this point, the second release film 13, which has been completely severed by the punching process, is reattached using a long strip of adhesive tape, facilitating removal of the second release film 13. As shown in Figure 5, the removed unused portion 17 passes over a tension roller 19 and is ultimately wound onto a waste roller 20.

According to this embodiment, the peeling forces F1 and F2 and the adhesion force F3 are designed to meet the specified requirements. Therefore, when the second peeling film 13 and the unnecessary portion 17 of the protective film-forming film are wound, even if the side surface of the protective film-forming film contacts the stainless steel tension roller 19, the protective film-forming film will not remain attached to the tension roller 19, allowing the second peeling film 13 and the unnecessary portion 17 of the protective film-forming film to be wound around the waste roller 20.

As a result of the waste material removal step, the protective film-forming film 16 punched into a predetermined closed shape remains on the first release film 12. The exposed protective film-forming film 16 is then attached to a predetermined workpiece.

When removing the second release film from the punched protective film-forming film 16, satisfying the relationship F1 > F2 facilitates removal of the second release film, ensuring that the punched protective film-forming film 16 remains on the first release film 12.

The punched protective film-forming sheet 10 can be rolled into a roll for storage and transportation.

(5. Workpiece Processing Method)

As an example of a method for processing a workpiece using a punched protective film-forming sheet according to this embodiment, a method for manufacturing a package in which a wafer with a protective film attached is placed on a substrate and processed.

The packaging manufacturing method includes at least the following steps 1 to 9.

Step 1: Punching the protective film forming sheet 10

Step 2: Removing the second release film 13 and the useless portion 17 of the protective film-forming film (waste removal step)

Step 3: Winding the removed second release film 13 and the useless portion 17 of the protective film-forming film by means of a tension roller 19.

Step 4: Attaching the punched protective film 16 of the protective film forming sheet 10 to the back side of the wafer.

Step 5: Forming the attached protective film into a protective film

Step 6: Peeling the first peeling film 12 from the protective film or protective film-forming film

Step 7: Singulate the wafer having the protective film or protective film-forming film on the back side to obtain multiple wafers with protective films or protective film-forming films.

Step 8: Placing the chip with the protective film or protective film-forming film on the substrate

Step 9: Heating the wafer with the protective film or protective film-forming film disposed on the substrate and the substrate.

Steps 1 through 3 are as described above. Step 5 can be performed before step 6 or after any of steps 6 through 9. In other words, the step of converting the protective film forming film into a protective film can be performed at any stage after the protective film forming film is attached to the wafer.

With reference to the accompanying drawings, the manufacturing method of the device including steps 1 to 9 above is described.

As shown in Figure 7, the protective film-forming film 16 of the protective film-forming sheet 10 is attached to the back surface of the wafer 21 (step 4). The attached protective film-forming film 16 is then cured to form a protective film 32 (step 5), resulting in a wafer with a protective film. If the protective film-forming film 16 is thermosetting, it can be heated at a predetermined temperature for an appropriate period of time. Alternatively, if the protective film-forming film 16 is energy-ray-curable, an energy-ray-transmitting film can be used as the first release film 12, with the energy rays incident from the side of the first release film 12.

Alternatively, the protective film forming film 16 may be cured after the dicing step described later, or after the wafer with the protective film formed thereon is picked up from the dicing sheet.

Next, the wafer 21 with the protective film is transferred to a known dicing blade 22 and diced, as shown in Figure 8 , to obtain wafers 31 with protective films 32 (chips 30 with protective films) (Step 7). The dicing blade 22 is then expanded in a planar direction as needed, and the chip 30 with the protective film is picked up from the dicing blade 22 using a suction nozzle (not shown).

The picked-up wafer 30 with protective film can be transported to the next step, or it can be temporarily stored on a tray, tape, etc. and transported to the next step after a specified period of time.

As shown in Figure 9, the wafer 30 with protective film, which has been transported to the next step, is moved onto the substrate 50 by the suction nozzle. The terminals on the substrate are released from the suction nozzle and positioned at a position where the protruding electrodes 33, such as bumps, can be connected to the terminals, such as pads (Step 8). At this point, other wafers other than the wafer 30 with protective film can also be mounted on the substrate 50. Therefore, multiple wafers can be mounted on the same substrate.

The chip with the protective film placed at a predetermined location on the substrate is heated (reflow soldering) (step 9). Reflow soldering conditions preferably include a maximum heating temperature of 180-350°C and a reflow time of 2-10 minutes.

During the reflow process, the bump electrodes 33 of the chip 30 with the protective film melt and become electrically and mechanically connected to the terminal portion on the substrate, and the chip 30 with the protective film is mounted on the substrate.

The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments and can be modified in various forms within the scope of the present invention.

Implementation Examples

The present invention is further described below using examples, but the present invention is not limited to these examples.

(Manufacturing of protective film-forming sheet)

[First peeling (repeeling)]

<Exfoliating composition>

Prepare the following raw materials for the exfoliant composition.

．Silicone-based release agent containing organopolysiloxane with vinyl groups and organopolysiloxane with hydrosilyl groups (manufactured by Dow Corning Toray Co., Ltd., BY24-561, solid content: 30% by mass)

Dimethylpolysiloxane (weight average molecular weight: 2000) (manufactured by Shin-Etsu Chemical Co., Ltd., X-62-1387, solid content 100% by mass)

MQ resin with vinyl content (manufactured by Dow Corning Toray Co., Ltd., SD-7292, solid content 71% by mass) as a restripping additive

Platinum (Pt) catalyst (SRX-212, manufactured by Dow Corning Toray Co., Ltd., solid content 100% by mass)

The above raw materials were added to a mixed solvent of toluene and methyl ethyl ketone (toluene/methyl ethyl ketone = 1/1 (mass ratio)) at the blending ratios (solid content conversion) listed in Table 1 to adjust the total solid content to 2% by mass to prepare a coating agent containing a stripping agent composition.

<Manufacturing of the first peeling film>

A coating agent containing a release agent layer composition was applied to a PET film (manufactured by Mitsubishi Chemical Corporation, trade name: DIAFOIL (registered trademark) T-100, thickness: 50 μm) to a film thickness of 0.15 μm after drying. The coating was then heated and dried to form a release agent layer on the PET film, producing a first release film (re-release film).

<Determination of surface elastic modulus>

The surface elastic modulus of the peeling-treated surface of the obtained first peeling film was measured by the following method.

A cantilever made of silicon nitride (MLCT, manufactured by Bruker Corporation, with a tip radius of 20 nm, a resonance frequency of 125 kHz, and a spring constant of 0.6 N/m) was installed on an atomic force microscope (MultiMode 8, manufactured by Bruker Corporation). The first exfoliation film was placed on the microscope. The cantilever pressed and pulled the surface of the exfoliant layer of the first exfoliation film at a pressure of 2 nm and a scanning speed of 10 Hz. This operation was performed at 23°C. The force curves obtained were fitted using the JKR theory to calculate the surface elastic modulus. The surface elastic modulus (SEM) was measured at 4096 points within a 1 μm x 1 μm area on the surface of the release agent layer of the first release film. The average of these values was rounded to one decimal place to obtain the SEM (MPa). The results are shown in Table 1.

[Peel film for process]

A coating agent containing a stripping agent composition was prepared by diluting 33 parts by mass (based on solid content) of a solvent-type silicone stripper containing a vinyl group-containing polysiloxane and an organohydropolysiloxane (trade name "KS-835," solid content: 30% by mass, viscosity: 5000 mPa·s, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 part by mass (based on solid content) of a platinum catalyst (trade name "PL50T," manufactured by Shin-Etsu Chemical Co., Ltd.) with toluene solvent to a solid content concentration of 2.0% by mass.

A coating agent was applied to a 38μm-thick PET film substrate (trade name: DIAFOIL (registered trademark) T-100, manufactured by Mitsubishi Chemical Corporation) to a film thickness of 0.15μm after drying. The film was then dried at 150°C for 30 seconds to obtain a release film for the process.

[Second peeling film (light peeling film)]

Prepare the following peeling membranes A to C.

Peeling film A: SP-PET381130 (38μm thickness) manufactured by Lintec Corporation

Peeling film B: SP-PET381031 (38 μm thickness) manufactured by Lintec Corporation

In addition, the peeling film C was produced in the following manner.

In the same manner as for producing the first release film, a coating agent containing the release agent layer composition at the blending ratio shown in Table 1 was prepared. The coating agent containing the release agent layer composition was applied to a PET film (manufactured by Mitsubishi Chemical Corporation, trade name: DIAFOIL (registered trademark) T-100, thickness: 38 μm ) to a dried film thickness of 0.15 μm . The film was then heated and dried to form a release agent layer on the PET film, producing Release Film C (light release film). In addition, although the release agent layer of Release Film C is the same as that of the first release film, the application conditions are different and the PET film is thinner, resulting in a lighter release than the first release film. Table 3 shows the second release film used in the Examples and Comparative Examples.

[Coating agent containing a protective film-forming composition]

The following ingredients were mixed at the blending ratio (solid content conversion) shown in Table 2, and diluted with methyl ethyl ketone to a solid content concentration of 50% by mass to prepare a coating agent.

(A) Polymer component

(A-1) (Meth)acrylate copolymer (weight-average molecular weight: 400,000, glass transition temperature: -1°C) prepared by copolymerization of 10 parts by mass of n-butyl acrylate, 70 parts by mass of methyl acrylate, 5 parts by mass of glycidyl methacrylate, and 15 parts by mass of 2-hydroxyethyl acrylate.

(A-2) (Meth)acrylate copolymer (weight-average molecular weight: 450,000, glass transition temperature: 2°C) prepared by copolymerizing 10 parts by mass of n-butyl acrylate, 65 parts by mass of methyl acrylate, 12 parts by mass of glycidyl methacrylate, and 13 parts by mass of 2-hydroxyethyl acrylate.

(B) Curing component (thermosetting component)

(B-1) Bisphenol A-type liquid epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER828, epoxy equivalent weight 184-194 g/eq)

(B-2) Bisphenol A-type liquid epoxy resin dispersed with acrylic rubber particles (manufactured by Nippon Shokubai Co., Ltd., BPA328, epoxy equivalent weight 230 g/eq, acrylic rubber content 20 phr)

(B-3) Dicyclopentadiene epoxy resin (manufactured by DIC Corporation, EPICLON HP-7200HH, softening point 88-98°C, epoxy equivalent weight 255-260 g/eq)

(C) Curing agent: Dicyandiamide (manufactured by Mitsubishi Chemical Corporation, DICY7)

(D) Curing accelerator: 2-phenyl-4,5-dihydroxymethylimidazole (manufactured by Shikoku Chemicals Corporation, Curezol 2PHZ)

(E) Filling materials

(E-1) Epoxy-modified spherical silica filler (manufactured by Admatechs, SC2050MA, average particle size 0.5 μm)

(E-2) Silica filler ("YC100C-MLA" manufactured by Admatechs, average particle size 0.1 μm)

(F) Silane coupling agent: γ -glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM403, methoxy equivalent weight 12.7 mmol/g, molecular weight 236.3)

(G) Colorant: Carbon black (manufactured by Mitsubishi Chemical Corporation, MA600B, average particle size 28 nm)

[Table 2]

A coating agent containing the prepared protective film-forming film composition was applied to the release-treated surface of the first release film and dried at 100°C for 2 minutes to form a 20μm-thick protective film-forming film. The process release film was then attached to the protective film-forming film to form a laminate of first release film/protective film-forming film/process release film. The attachment conditions were a temperature of 60°C, a pressure of 0.4 MPa, and a speed of 1 m/min. The film was then allowed to stand in this state for 48 hours in an environment of 23°C and 50% RH.

Next, the release film for the process is peeled off, and a second release film (any of the above-mentioned A-C) is attached to the exposed protective film-forming film, resulting in a protective film-forming sheet with release films formed on both sides of the protective film-forming film. The attachment conditions are a temperature of 60°C, a pressure of 0.6 MPa, and a speed of 1 m/min. The protective film-forming sheet is then cut to a width of 208 mm and wound into a 50-meter length to form a roll.

The following measurements and evaluations were performed using the obtained protective film-forming sheet.

[Peeling force F1 when peeling the first peeling film from the protective film forming film]

The second release film was peeled from the resulting protective film-forming sheet. The exposed surface of the protective film-forming film was then attached to the high-adhesion surface of 25 μm-thick high-adhesion PET (PET25A-4100, manufactured by TOYOBO Co., Ltd.) using hot lamination (70°C, 1 m/min) to create a laminate sample. The laminate sample was cut into 100 mm wide sections to prepare measurement samples. The back of the first release film of the measurement sample was secured to a rigid support plate using double-sided tape.

Using a universal tensile testing machine (manufactured by Shimadzu Corporation, product name "AUTOGRAPH (registered trademark) AG-IS"), the load applied during the peeling of the protective film-forming film/highly adhesive PET composite (monolayer) from the first peeling film was measured at a peeling angle of 180° and a peeling speed of 1 m/min. The total measured distance was 100 mm, and the average of the measured values over the 80 mm interval (excluding the first and last 10 mm removed) was converted to mN/100 mm to represent the peeling force F1. The results are shown in Table 3.

[Peeling force F2 when peeling the second peeling film from the protective film forming film]

The resulting protective film-forming sheet was cut into 100 mm widths to prepare measurement samples. The back of the first release film of the measurement sample was secured to a rigid support plate using double-sided tape.

Using a universal tensile testing machine (manufactured by Shimadzu Corporation, product name "AUTOGRAPH (registered trademark) AG-IS"), the second peeling film was peeled from the test sample. The load at this point was measured under the same conditions as for measuring F1 above, and this load was defined as the peeling force F2. The results are shown in Table 3.

[Adhesion force between protective film forming film and stainless steel plate F3]

The protective film-forming film was exposed from the protective film-forming sheet in the following manner, and the protective film-forming film was attached to a stainless steel plate, and the adhesive strength was measured.

<Securing the protective film forming film on the adhesive tape>

I. Peel off the second release film from the protective film-forming sheet with a three-layer structure of second release film/protective film-forming film/first release film.

II. At 23°C, adhere an adhesive tape manufactured by Lintec Corporation (product name: PET50PLthin: acrylic adhesive layer/50μm PET substrate) to the exposed protective film-forming film to create a laminate sample of "PET substrate/acrylic adhesive/protective film-forming film/first release film."

III. Cut the laminated sample into thin strips 25 mm wide and 250 mm long.

<Securing the protective film-forming film on the stainless steel plate>

I. Clean a stainless steel plate (SUS304 #600 single-sided 600HL 0.5mm thick × 70mm × 150mm) with toluene and methyl ethyl ketone and dry it.

II. Peel off the first release film from the stack of "PET substrate/acrylic adhesive/protective film-forming film/first release film" to expose the protective film-forming film.

III. Lay the exposed protective film onto a stainless steel plate using a 2kg roller at 23°C.

Allow the adhesive to stand without heating for 2 minutes (±20 seconds) after application, and then measure the adhesive strength using the following method.

Using a universal tensile testing machine (manufactured by Shimadzu Corporation, product name "AUTOGRAPH AG-IS"), the peeling force was measured at a peeling speed of 300 mm/min, a temperature of 23°C, and a peeling angle of 180° over a measuring distance of 70 mm. The average of the measured values over a 50-mm period, covering the first and last 10 mm of the measuring distance, was converted to mN/100 mm to represent the adhesion force F3 of the protective film-forming film to the stainless steel sheet. This value was then used to calculate F2/F3.

[Stability of the waste removal process]

Using a RAD-3600F/12 machine manufactured by Lintec Corporation, with specifications for 200mm wafers, the punch was inserted from the second release film side of a protective film-forming sheet (50mm in length and 208mm in width) to punch the protective film-forming film and the second release film into circular shapes (with an inner diameter of 198mm). The circularly punched protective film-forming film 16 remained on the first release film 12. As shown in FIG4 , the second release film 13 and the unnecessary portion 17 surrounding the circularly punched protective film-forming film 16 were removed (waste removal step). At this point, the punched, completely cut second release film 13 is reattached using a long strip of adhesive tape 18, and then removed. Then, as shown in Figure 5, the removed second release film 13 and the unused portion 17 are finally wound around a waste roller 20 via a tension roller 19.

During the 10m winding of the second peeling film and the unused portion, the number of times the protective film forming film residue adhered to the tension roll was counted and evaluated according to the following criteria. If the protective film forming film residue adhered to the tension roll, the system was stopped (waste removal was stopped) and the tension roll was cleaned by wiping with methyl ethyl ketone.

A: 0 times

B: 1 time

C: 2-3 times

D: 4 or more times

The above results are shown in Table 3.

As shown in Table 3, by designing the peeling forces F1 and F2 between the protective film-forming film and the release film, as well as the adhesion force F3 of the protective film-forming film to the stainless steel plate, to meet the specified requirements, even if the side of the protective film-forming film contacts the stainless steel tension roller when winding the second release film and the unused portion, the protective film-forming film will not remain attached to the roller. This allows the second release film and the unused portion to be stably wound onto the waste roller, eliminating the need to stop waste removal and improving production efficiency.

Industrial Applicability

As described above, the present invention can provide a protective film-forming sheet and a method for producing the same that can sufficiently suppress the cessation of waste material removal.

10: Sheet for forming protective film

11: Protective film forming film

12: First peeling membrane

13: Second peeling membrane

Claims (6)

A sheet for forming a protective film is a long sheet and comprises: a protective film forming film for forming a protective film, a first peeling film provided on one surface of the protective film forming film, and a second peeling film provided on the other surface of the protective film forming film, wherein when the peeling force when the first peeling film is peeled off from the protective film forming film is set to F1 and the peeling force when the second peeling film is peeled off from the protective film forming film is set to F2, the relationship F1>F2 is satisfied, and the peeling force F1>F2 is satisfied. The adhesion of the protective film-forming film to the stainless steel plate, when F3 is defined as F2/F3 ≥ 0.10, satisfies the relationship F2/F3 ≥ 0.10, F2 is 30 mN/100 mm or greater, and F3 is 500 mN/100 mm or less. F1 and F2 are measured under the conditions of a peeling angle of 180° and a peeling speed of 1 m/min, while F3 is measured under the conditions of a peeling speed of 300 mm/min, a temperature of 23°C, and a peeling angle of 180°. The protective film-forming sheet according to claim 1, wherein the weight of the epoxy resin that is liquid at room temperature contained in the protective film-forming composition is 12 parts by mass or less, based on 100 parts by mass of the total weight of the protective film-forming composition constituting the protective film-forming film. The protective film-forming sheet according to claim 1 or 2, wherein the weight of the filler contained in the protective film-forming composition is 15 parts by mass or more and less than 55 parts by mass, based on 100 parts by mass of the total weight of the protective film-forming composition constituting the protective film-forming film. The protective film-forming sheet according to claim 1 or 2, wherein a cut is formed in the protective film-forming sheet so that a portion of the protective film-forming sheet has a predetermined closed shape when viewed from above, and the cut penetrates the protective film-forming film in the thickness direction of the protective film-forming sheet and reaches a portion of the first release film. The protective film-forming sheet according to claim 3, wherein a cut is formed in the protective film-forming sheet so that a portion of the protective film-forming sheet has a predetermined closed shape when viewed from above, and the cut penetrates the protective film-forming film in the thickness direction of the protective film-forming sheet and reaches a portion of the first release film. A method for producing a punched protective film-forming sheet, comprising the step of forming a cutout in a portion of the protective film-forming sheet according to any one of claims 1 to 5 so that the cutout has a predetermined closed shape, the cutout penetrating the protective film-forming film in the thickness direction of the protective film-forming sheet and reaching a portion of the first release film.