JP2008260845A - Thermosetting adhesive sheet for sealing - Google Patents

Abstract

The present invention provides a thermosetting adhesive sheet for sealing which can easily and efficiently seal a hollow device.
A sealing thermosetting adhesive sheet used for sealing a chip type device with a connecting electrode portion (bump) mounted on a printed circuit board. And as said thermosetting type adhesive sheet for sealing, the tensile elasticity modulus in 80 degreeC before thermosetting is 5 * 10 < ⁵ > -5 * 10 < ⁷ > Pa, and the tensile elasticity modulus in 150 degreeC after thermosetting is It has the physical property which is 5.5 * 10 < ⁷ > -1 * 10 < ⁹ > Pa.
[Selection] Figure 1

Description

  The present invention relates to a thermosetting adhesive sheet used for sealing a chip-type device, and more specifically, a device whose surface needs to be hollow, such as a surface acoustic wave device (SAW device). The present invention relates to a thermosetting adhesive sheet used for sealing so-called hollow devices such as quartz devices, high-frequency devices, and acceleration sensors.

  Conventionally, sealing of chip-type devices such as semiconductor elements and electronic components has been performed by transfer molding using a powdered epoxy resin composition, potting, dispensing, printing using a liquid epoxy resin composition or silicone resin. It has been done by law. However, in such a sealing method, there is a problem that an expensive molding machine is required or a sealing resin adheres to other than necessary portions, and a cheaper and simpler sealing method is desired. It was.

  In particular, in the sealing of a device that needs to have a hollow surface, it is difficult to suppress the inflow of the sealing material to the active surface directly under the device by the dispensing method using the conventional liquid sealing material, A dam is provided on the chip or the substrate to control the inflow of the sealing material (see, for example, Patent Documents 1 to 3). Even in such a technique, it is difficult to completely control the flow of the liquid sealing material, which causes a decrease in yield. In addition, it has been a factor that hinders downsizing and cost reduction of devices.

In order to solve such a problem, for example, a method of sealing a hollow device using a sealing film laminate has been proposed (see Patent Document 4).
JP 2004-64732 A JP 2004-56296 A JP 2005-39331 A JP 2004-327623 A

  However, in sealing a hollow type device using the sealing film laminate, it is difficult to completely control the inflow of the sealing resin into the hollow part because the elastic modulus after curing is low, From the perspective of solving the problem, it was hard to say that it was satisfactory enough.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a thermosetting adhesive sheet for sealing that can easily seal a hollow type device with a high yield.

In order to achieve the above object, the sealing thermosetting adhesive sheet of the present invention is a sealing thermosetting adhesive sheet used for sealing a chip-type device mounted on a substrate. The tensile elastic modulus at 80 ° C. before thermosetting is 5 × 10 ^{5 to} 5 × 10 ⁷ Pa, and the tensile elastic modulus at 150 ° C. after thermosetting is 5.5 × 10 ⁷ to 1 × 10 ⁹ Pa. It has a configuration of being.

In order to achieve the above object, the present inventors have repeatedly studied the physical properties of a thermosetting adhesive sheet used as a sealing material. As a result, as a thermosetting adhesive sheet, the tensile modulus at 80 ° C. before thermosetting is 5 × 10 ^{5 to} 5 × 10 ⁷ Pa, and the tensile modulus at 150 ° C. after thermosetting is 5.5 × 10. ^When a sheet having physical properties set to ⁷ to 1 × 10 ⁹ Pa is used, since a suitable viscoelasticity is provided at the time of sealing a chip-type device, it is on a substrate using a thermosetting adhesive sheet. The inventors have found that the intrusion of the resin into the lower part of the chip type device is suppressed at the time of sealing the chip type device, and have reached the present invention.

As described above, the thermosetting adhesive sheet for sealing of the present invention is used for sealing a chip-type device mounted on a substrate, and has a tensile elastic modulus at 80 ° C. before thermosetting of 5 × 10 ^5. in ~5 × 10 ⁷ Pa, and a tensile modulus at 0.99 ° C. after thermal curing is ^{5.5 × 10 7 ~1 × 10 9} Pa. For this reason, when sealing a chip-type device mounted on a substrate, intrusion into the lower portion of the chip-type device is suppressed, and a hollow portion between the substrate and the chip-type device is formed and held. Become. Therefore, in resin sealing using this sealing thermosetting adhesive sheet, it is possible to perform resin sealing simply and with good yield.

  And as the said thermosetting adhesive sheet for sealing, the said tensile elasticity modulus was controlled to the predetermined value as it was formed in the sheet form using the epoxy resin composition containing the below-mentioned AE component. Things are easily obtained.

  Further, when the content of the inorganic filler as the D component is set to a ratio of 60 to 80% by weight of the entire epoxy resin composition, the thermosetting adhesive for sealing in which the tensile elastic modulus is controlled to a predetermined value. A sheet is easily obtained.

  Further, when a quaternary phosphonium salt compound is used as the curing accelerator as the E component, a sealing thermosetting adhesive sheet in which the tensile elastic modulus is controlled to a predetermined value can be easily obtained.

  Next, embodiments of the present invention will be described in detail.

  The thermosetting adhesive sheet for sealing of the present invention has a specific tensile elastic modulus before and after curing. For example, an epoxy resin (A component), a phenol resin (B component), an elastomer (C component), an inorganic material It is obtained by forming into a sheet using an epoxy resin composition containing a filler (D component) and a curing accelerator (E component).

  The epoxy resin (component A) is not particularly limited. For example, dicyclopentadiene type epoxy resin, cresol novolac type epoxy resin, phenol novolac type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin. Various epoxy resins such as biphenyl type epoxy resin and trishydroxyphenylmethane type epoxy resin can be used. These epoxy resins may be used alone or in combination of two or more. Among these, from the viewpoint of flexibility before curing and securing strength after curing, a combined system of trishydroxyphenylmethane type epoxy resin and bisphenol A type epoxy resin is preferable.

  The phenol resin (component B) is not particularly limited as long as it causes a curing reaction with the epoxy resin (component A). For example, dicyclopentadiene type phenol resin, phenol novolac resin , Cresol novolac resin, phenol aralkyl resin and the like are used. These phenolic resins may be used alone or in combination of two or more. And as said phenol resin, it is preferable to use a hydroxyl equivalent of 70-250 and a softening point of 50-110 degreeC, and a phenol novolak resin is used suitably from a viewpoint that hardening reactivity is high especially.

  And the compounding ratio of the said epoxy resin (A component) and a phenol resin (B component) is generally in a phenol resin (B component) with respect to 1 equivalent of epoxy groups in an epoxy resin (A component). It is preferable to blend so that the total number of hydroxyl groups is 0.7 to 1.5 equivalents. More preferably, it is 0.9-1.2 equivalent.

  The elastomer (C component) used together with the A component and the B component imparts flexibility and flexibility to the epoxy resin composition, and the structure is particularly limited as long as such an effect is exhibited. Although it is not a thing, the following rubbery polymers are mention | raise | lifted, for example. That is, examples include various acrylic ester copolymers such as polyacrylic acid esters, polymers made of butadiene rubber, styrene-butadiene rubber (SBR), ethylene-vinyl acetate copolymer (EVA), isoprene rubber, acrylonitrile rubber, and the like. These may be used alone or in combination of two or more.

  The content of the elastomer (component C) is preferably set in the range of 15 to 70% by weight in the total organic components of the epoxy resin composition from the viewpoint of imparting flexibility and flexibility. Preferably, it is 30 to 60% by weight in the total organic components. That is, when the content of the elastomer (component C) is less than the lower limit, it becomes difficult to impart desired flexibility and flexibility, and the handling workability tends to be reduced as an adhesive sheet. If the upper limit is exceeded, the elastic modulus after curing is lowered, and the strength of the molded product tends to be insufficient.

  It does not specifically limit as an inorganic filler (D component) used with the said AC component, Various conventionally well-known fillers are used. Examples thereof include quartz glass powder, talc, silica powder (such as fused silica powder and crystalline silica powder), alumina powder, aluminum nitride, and silicon nitride powder. These may be used alone or in combination of two or more. Among them, the silica powder is preferably used from the viewpoint that the linear expansion coefficient of the obtained cured product can be reduced, and among the silica powders, the use of the fused silica powder is particularly preferable from the viewpoint of high filling property and high fluidity. preferable. Examples of the fused silica powder include spherical fused silica powder and crushed fused silica powder. From the viewpoint of fluidity, it is particularly preferable to use a spherical fused silica powder. Among them, it is preferable to use those having an average particle diameter in the range of 0.2 to 30 μm, and particularly preferable to use those in the range of 0.5 to 15 μm. The average particle diameter can be derived by, for example, using a sample arbitrarily extracted from the population and measuring it using a laser diffraction / scattering particle size distribution measuring apparatus.

  It is preferable to set content of the said inorganic filler (D component) in the range of 60 to 80 weight% of the whole epoxy resin composition, Especially preferably, it is 65 to 75 weight%. That is, if the content of the inorganic filler (component D) is less than the lower limit value, the tensile elastic modulus at 150 ° C. after thermosetting tends to be low and it becomes difficult to obtain desired physical properties, which exceeds the upper limit value. This is because the tensile elastic modulus at 80 ° C. before thermosetting tends to be high and it becomes difficult to obtain desired physical properties.

  The curing accelerator (component E) used together with the components A to D is particularly limited as long as it can accelerate the curing reaction between the epoxy resin (component A) and the phenol resin (component B). Instead, various conventionally known curing accelerators can be used, and existing curing accelerators such as phosphorus-based curing accelerators and amine-based curing accelerators can be used, but particularly by using quaternary phosphonium salt compounds. It is preferable because a thermosetting adhesive sheet having excellent room temperature storage property can be obtained. And in use of the thermosetting adhesive sheet for sealing of this invention, it is preferable that it can be preserve | saved for a long time at normal temperature from a viewpoint of workability | operativity and quality stability, and the hardening accelerator (E As the component), for example, tetraphenylphosphonium tetraphenylborate is particularly preferably used.

  The content of the curing accelerator (component E) is preferably set in the range of 0.1 to 10% by weight of the entire epoxy resin composition, more preferably 0.3 to 3% by weight, particularly preferably. Is 0.5 to 2% by weight.

  In the present invention, other additives such as a flame retardant and a pigment such as carbon black can be appropriately blended with the epoxy resin composition as necessary in addition to the components A to E.

  Examples of the flame retardant include organic phosphorus compounds, antimony oxide, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, and the like. These may be used alone or in combination of two or more.

  The thermosetting adhesive sheet for sealing of the present invention can be produced, for example, as follows. First, an epoxy resin composition is prepared by mixing each compounding component, but there is no particular limitation as long as each compounding component is uniformly dispersed and mixed. And each compounding component is melt | dissolved in a solvent etc. as needed, and it forms into a film by varnish coating. Alternatively, a solid resin may be prepared by directly kneading each compounding component with a kneader or the like, and the solid resin thus obtained may be extruded into a sheet to form a film. Especially, the said varnish coating method is used suitably from the point that the sheet | seat of uniform thickness can be obtained simply.

  The production of the thermosetting adhesive sheet for sealing of the present invention by the varnish coating method will be described. That is, the above components A to E and other additives as necessary are mixed as appropriate according to a conventional method, and uniformly dissolved or dispersed in an organic solvent to prepare a varnish. Next, the varnish is applied onto a substrate such as a polyester film and dried, and bonded together with a film such as a polyester film, and the thermosetting adhesive sheet is wound up.

  The organic solvent is not particularly limited, and various conventionally known organic solvents such as methyl ethyl ketone, acetone, dioxane, diethyl ketone, toluene, ethyl acetate and the like can be mentioned. These may be used alone or in combination of two or more. The concentration in the organic solvent is usually preferably in the range of 30 to 60% by weight.

  Although the thickness of the sheet after drying the organic solvent is not particularly limited, it is usually preferably set to 5 to 100 μm, more preferably 20 to 70 μm, from the viewpoint of uniformity of thickness and the amount of residual solvent. is there. The thermosetting adhesive sheet for sealing of the present invention thus obtained may be laminated and used so as to have a desired thickness if necessary. That is, the thermosetting adhesive sheet for sealing of the present invention may be used in a single layer structure or may be used as a laminate formed by laminating two or more layers.

The sealing thermosetting adhesive sheet of the present invention thus obtained must have the following characteristics (x) and (y).
(X) The tensile elastic modulus at 80 ° C. before thermosetting is 5 × 10 ^{5 to} 5 × 10 ⁷ Pa.
(Y) The tensile elastic modulus at 150 ° C. after thermosetting is 5.5 × 10 ⁷ to 1 × 10 ⁹ Pa.

That is, if the tensile modulus at 80 ° C. before thermosetting in the characteristic (x) is less than 5 × 10 ⁵ Pa, the sealing resin easily enters the hollow portion below the chip-type device, and 5 × 10 ⁷ Pa. If it exceeds the upper limit, the adhesiveness between the sealing resin portion and the substrate becomes poor. Further, in the characteristic (y), when the tensile elastic modulus at 150 ° C. after thermosetting is less than 5.5 × 10 ⁷ Pa, the strength tends to be insufficient when formed into a molded product, which exceeds 1 × 10 ⁹ Pa. This is because, during solder reflow or the like, sheet peeling or chip-type device cracks are likely to occur.

  The tensile elastic modulus at 80 ° C. before the thermosetting and the tensile elastic modulus at 150 ° C. after the thermosetting are respectively measured as follows. That is, the tensile elastic modulus at 80 ° C. before thermosetting is the storage elasticity at 80 ° C. before thermosetting of the thermosetting adhesive sheet for sealing before heat curing using a viscoelasticity measuring device under predetermined conditions. It is obtained by measuring the rate. Similarly, the tensile elastic modulus at 150 ° C. after thermosetting is obtained by storing the thermosetting adhesive sheet for sealing at 80 ° C. before thermosetting under a predetermined condition using a viscoelasticity measuring device after heat curing. It is obtained by measuring the elastic modulus.

  The heat curing conditions for the sealing thermosetting adhesive sheet are generally in the range of 150 to 190 ° C.

  The chip-type device mounted on the substrate using the thermosetting adhesive sheet for sealing of the present invention is sealed, for example, as follows. That is, after a chip-type device is mounted at a predetermined position on the substrate, a sealing thermosetting adhesive sheet is disposed so as to cover the mounted chip-type device, and the sheet is heat-cured under predetermined sealing conditions. As a result, the chip-type device is resin-sealed in a state where the space between the chip-type device and the substrate is held hollow.

  As the sealing conditions, for example, after performing vacuum pressing at a temperature of 80 to 100 ° C. and a pressure of 100 to 500 kPa for 0.5 to 5 minutes, the atmosphere is opened, and the temperature is 150 to 190 ° C. for 30 to 120 minutes. Heating can be mentioned.

  An example of the configuration of the semiconductor device thus obtained will be described. That is, as shown in FIG. 1, in a state where the connection electrode portion (bump) 3 provided in the chip-type device 1 and the connection electrode portion (not shown) provided in the printed circuit board 2 face each other, A chip type device 1 is mounted on the printed circuit board 2. A sealing resin layer 4 is formed on the printed circuit board 2 and sealed with resin so as to cover the chip type device 1 mounted on the printed circuit board 2. The lower part of the chip type device 1 between the chip type device 1 and the printed circuit board 2 is formed in the hollow portion 5.

  In the semiconductor device, the connection electrode portion 3 provided in the chip-type device 1 is formed in a bump shape, but the present invention is not limited to this, and the connection electrode portion provided in the printed circuit board 2 is not limited thereto. May be provided in a bump shape.

  The distance between the gaps (hollow portions 5) between the chip type device 1 and the printed circuit board 2 is appropriately set depending on the size of the connecting electrode portion (bump) 3 and the like, but is generally about 10 to 100 μm. . The distance between the connecting electrode portions (bumps) 3 is generally preferably set to about 150 to 500 μm.

  Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples.

  First, each component shown below was prepared.

[Epoxy resin a]
Trishydroxyphenylmethane type epoxy resin (Nippon Kayaku Co., Ltd., EPPN-501HY)
[Epoxy resin b]
Bisphenol A epoxy resin (Japan Epoxy Resin, Epicoat 828)
[Phenolic resin]
Novolac type phenol resin (Maywa Kasei Co., Ltd., DL-65)
〔acrylic resin〕
Acrylic copolymer (manufactured by Nagase ChemteX Corporation, Teisan Resin SG-P3)
[Curing accelerator a]
Tetraphenylphosphonium tetraphenylborate (manufactured by Hokuko Chemical Co., Ltd., TPP-K)
[Curing accelerator b]
Triphenylphosphine (silica powder)
Spherical fused silica powder with an average particle size of 5.5 μm (manufactured by Denki Kagaku Kogyo Co., Ltd., FB-7SDC)

[Examples 1 to 5, Comparative Examples 1 to 4]
The components shown in Tables 1 and 2 below were dispersed and mixed in the proportions shown in the same table, and 100 parts by weight of an organic solvent (methyl ethyl ketone) was added thereto to prepare a sheet coating varnish.

  Next, the varnish is coated on a polyester film A having a thickness of 50 μm (MRF-50, manufactured by Mitsubishi Chemical Polyester Co., Ltd.) with a comma coater, dried, and then polyester film B having a thickness of 38 μm (manufactured by Mitsubishi Chemical Polyester Co., Ltd.). , MRX-38) to obtain a thermosetting adhesive sheet. Then, the said adhesive sheet was laminated | stacked using the roll laminator, and the 200-micrometer-thick thermosetting type adhesive sheet was produced.

[Tensile modulus]
The tensile modulus of elasticity (tensile modulus at 80 ° C. before thermosetting and tensile modulus at 150 ° C. after thermosetting) of the obtained thermosetting adhesive sheet was measured using a viscoelasticity measuring device RSAII manufactured by Rheometrics. The measurement was made at a measurement frequency of 1 Hz and a heating rate of 5 ° C./min, and the obtained storage elastic modulus value was obtained. The term “after heat curing” refers to after heat curing at a curing condition of 175 ° C.

[Sealing evaluation]
The obtained thermosetting adhesive sheet was placed so as to cover a SAW filter chip (chip thickness: 300 μm, bump height: 50 μm) arrayed and mounted in a matrix on a ceramic substrate, under conditions of a temperature of 100 ° C. and a pressure of 300 kPa. For 1 minute in a vacuum (degree of ultimate vacuum 6.65 × 10 ² Pa). After opening to the atmosphere, the substrate was put into an oven at 175 ° C. for 1 hour to heat and cure the thermosetting adhesive sheet. After that, the package is separated into pieces using a dicing apparatus, the cross section of the obtained chip is observed, the presence or absence of resin intrusion into the hollow portion below the chip, and the sealing formed by the substrate and the thermosetting adhesive sheet. The adhesion with the stop resin portion was observed. And what evaluated the penetration | invasion of the resin to the hollow part of a chip | tip lower part was evaluated as x, and what was not confirmed penetration | invasion was evaluated as (circle). On the other hand, regarding the adhesiveness, the case where the adhesion was sufficient was evaluated as ◯, and the case where the adhesion was insufficient and the chip side surface after dicing had a gap between the resin and the ceramic substrate was evaluated as x.

[Reflow resistance test]
Furthermore, each chip was exposed to 260 ° C. × 10 seconds × 3 solder reflow conditions, and the presence or absence of peeling of the thermosetting adhesive sheet (sealing resin portion) from the substrate was observed. As a result, the case where peeling did not occur was evaluated as ◯, and the case where peeling occurred was evaluated as x.

[Normal temperature storage]
After the obtained thermosetting adhesive sheet was stored at 20 ° C. for 6 months, the tensile elastic modulus before curing at 80 ° C. was measured using a viscoelasticity measuring device RSAII manufactured by Rheometrics in the same manner as described above. As a result, while showing the measured tensile elasticity modulus, the thing whose increase rate was less than 20% of the initial stage was evaluated as ◯, and the one whose increase rate was 20% or more at the initial stage was evaluated as x.

  As a result, the example product satisfying the specific tensile elastic modulus did not penetrate into the lower part of the chip, had sufficient adhesion to the substrate, and did not peel off. In addition, with respect to the storage stability at normal temperature, good results were obtained except for Example 5. In addition, regarding Example 5, since the elastic modulus increases when stored at room temperature, it must be stored in a cold place. On the other hand, the comparative example product that deviates from the specific tensile elastic modulus is inferior to the evaluation of either the penetration of the resin into the lower part of the chip, the adhesion with the substrate, or the occurrence of peeling. there were.

It is sectional drawing which shows typically an example of the semiconductor device formed by sealing using the thermosetting adhesive sheet for sealing of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chip-type device 2 Wiring circuit board 3 Chip-type device connection electrode part (bump)
4 Sealing resin layer 5 Hollow part

Claims (4)

A thermosetting adhesive sheet for sealing used for sealing a chip-type device mounted on a substrate, having a tensile elastic modulus at 80 ° C. before thermosetting of 5 × 10 ^{5 to} 5 × 10 ⁷ Pa. And a thermosetting adhesive sheet for sealing, wherein the tensile elastic modulus at 150 ° C. after thermosetting is 5.5 × 10 ⁷ to 1 × 10 ⁹ Pa. The thermosetting adhesive sheet for sealing according to claim 1, wherein the thermosetting adhesive sheet for sealing is formed into a sheet shape using an epoxy resin composition containing the following components (A) to (E): .
(A) Epoxy resin.
(B) Phenolic resin.
(C) Elastomer.
(D) Inorganic filler.
(E) Curing accelerator.   The thermosetting adhesive sheet for sealing according to claim 2, wherein the content of the inorganic filler as the component (D) is set to a ratio of 60 to 80% by weight of the entire epoxy resin composition.   The thermosetting adhesive sheet for sealing according to claim 2 or 3, wherein the curing accelerator as the component (E) is a quaternary phosphonium salt compound.

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