HK1059501B - Method for manufacturing semiconductor device and heat-resistant pressure-sensitive adhesive tape for use therein - Google Patents

Description

Method of manufacturing semiconductor device and heat-resistant pressure-sensitive adhesive tape used therein

Technical Field

The present invention relates to a method of manufacturing a semiconductor device using a metal lead frame (lead frame) to which a heat-resistant pressure-sensitive adhesive tape is attached, and to a heat-resistant pressure-sensitive adhesive tape used in such a method.

Background

In recent years, LSI packaging technology has been focused on Chip Size packaging (CSP-Chip Size/scalepack) processes. Such processes typically include Quad Flat no-Lead packages (QFN-Quad Flat no-Lead packages) with Lead terminals disposed inside the Package. This is a particularly attractive form in terms of miniaturization and high integration density. In recent years, a particularly attractive method of manufacturing QFNs involves systematically arranging a plurality of QFN chips on individual die pads (die pads) within a package pattern area of a leadframe; sealing each chip with a sealing resin in a die cavity (die cavity) at a certain timing, and cutting the main body of the sealing body into a plurality of divided QFN structures. This method can significantly improve productivity per area of the lead frame.

In such a QFN process including the step of simultaneously sealing a plurality of semiconductor chips, the injection molding die clamps only an outer portion of the resin sealing region beyond the package pattern region. Therefore, the pressure from the injection mold holding the outer lead surface may not be sufficient in the package pattern area, particularly in the central area thereof. Thus, it may be very difficult to prevent the sealing resin from leaking into the outer lead side faces, and the QFN terminals and the like may be covered with undesired resin.

Faced with this problem, during QFN, a pressure sensitive adhesive tape may be attached to the outer lead side of the leadframe. Such a process obtains a sealing effect, which can be effective in particular in preventing the resin from leaking to the external lead side in the resin sealing step, in accordance with the self-adhesive (covering) property of the pressure sensitive adhesive tape.

In such a process, it is fundamentally difficult to attach the heat-resistant pressure-sensitive adhesive tape after the step of mounting the semiconductor chip on the lead frame or after the step of wiring connection during the handling process. Thus, in a preferred manner, the heat-resistant pressure-sensitive adhesive tape is attached to the outer pad surface of the lead frame at an early stage and then held during the step of mounting the semiconductor chip and the step of wiring connection of mounting before resin sealing. Thus, the heat-resistant pressure-sensitive adhesive tape should not only prevent leakage of the sealing resin but also satisfy all the required characteristics such as high heat resistance in the face of the process of mounting the semiconductor chip and not hinder elaborate operations in the adhering step.

If higher adhesiveness is emphasized in order to prevent resin leakage, a general heat-resistant pressure-sensitive adhesive layer may be selected. However, such a general heat-resistant pressure-sensitive adhesive tape may hinder wiring connection due to high elasticity of such a pressure-sensitive adhesive layer. In this case, functions required in a series of processes may be contradicted and difficult to be satisfied at the same time.

In order to solve these problems, the process of the semiconductor device proposed by each of the inventors employs a heat-resistant pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer with a thickness of 10 μm or less (Japanese patent application No.2001-020395, unpublished at the priority date of the present application). According to this process, a series of steps including wiring connection can be carried out without resin sealing.

Currently, the number of packages arranged per lead frame has been increased in terms of productivity. Therefore, not only the packages themselves are made finer, but also the number of arrangements has been increased so that more packages can be sealed in one sealing portion. Therefore, the above-described heat-resistant pressure-sensitive adhesive tape having a relatively thin adhesive layer for reducing the liner may have difficulty in equalizing sufficient sealing characteristics and other characteristics, and thus the basic object of preventing resin leakage cannot be suitably achieved.

Disclosure of Invention

Accordingly, an object of the present invention is to provide a method of manufacturing a semiconductor device in which heat-resistant pressure sensitive adhesive tape can appropriately prevent resin leakage in a sealing step for forming the latest fine type QFN, particularly in a process of simultaneously sealing many packages in a large matrix pattern, and the adhesive tape attached is difficult to cause troubles in a series of manufacturing steps. A heat resistant pressure sensitive adhesive tape for use in such a method is also provided.

The inventors have made intensive studies on physical properties, materials, thickness and other properties of the heat-resistant pressure-sensitive adhesive tape, and have found that the above object can be achieved by using a heat-resistant pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer having a specific thickness, made of an acrylic resin, and having an appropriate high-temperature memory elastic modulus. Based on this finding, the present invention has been completed.

Specifically, the present invention is directed to a method of fabricating a semiconductor device comprising at least the steps of: placing and bonding a plurality of semiconductor chips on respective die pads of a metal lead frame, said lead frame having outer pad side edges with heat resistant pressure sensitive adhesive tape attached thereto; wiring a connecting lead between each terminal of the lead frame and each electrode pad on the semiconductor chip; and cutting the body of the sealing body into a plurality of divided semiconductor devices, whichWherein the heat-resistant pressure-sensitive adhesive tape comprises a base layer made of a polyimide resin and a pressure-sensitive adhesive layer having a thickness of 1 to 20 μm, which is made of a polyacrylate plastic resin and has a thickness of 1.0X 10 at 200 ℃⁵Pa, memory elastic modulus. The physical properties including the memory elastic modulus are specifically determined in the present invention by the following method.

According to the present invention, the heat-resistant pressure-sensitive adhesive tape having a polyimide resin base layer has high heat resistance and, in addition, has a linear thermal expansion coefficient close to that of the metal lead frame. Therefore, such an adhesive tape is difficult to warp or peel off upon thermal expansion. Such an adhesive tape can maintain a high sealing effect, and thus can appropriately prevent leakage of resin at the sealing step. In addition, the polyimide resin base layer can provide good workability as well as good workability. The pressure-sensitive adhesive layer has a suitable high-temperature memory elastic modulus, and therefore, even at a relatively large thickness of about 20 μm, it can always maintain a suitable gasket effect. In the step of bonding with such an attached heat-resistant pressure-sensitive adhesive tape, the loss of bonding energy can be made small, and wiring connection can be carried out well in a more reliable manner. In the latest fine QFN type process, particularly a large matrix pattern type having a large number of packages sealed at the same time, the sealing material must produce a sufficient encapsulation effect to properly prevent resin leakage at the injection molding step. In this regard, the pressure-sensitive adhesive layer must have a suitable thickness of 1 μm or more. Therefore, the acrylic pressure-sensitive adhesive layer having a thickness of 1 to 20 μm in the present invention can provide a suitable thickness in addition to a suitable memory elastic modulus. Therefore, in the manufacturing process of a semiconductor device of the present invention, in the sealing step using the heat-resistant pressure-sensitive adhesive tape, the resin leakage can be appropriately prevented, and moreover, the attached adhesive tape is less likely to cause trouble in a series of steps.

The present invention is also directed to a heat-resistant pressure sensitive adhesive tape used in such a method of manufacturing a semiconductor device, comprising: a base layer made of polyimide resin, and a pressure-sensitive adhesive layer having a thickness of 1 to 20 μm and made of acrylicOlefinic acid resin, and has a molecular weight of 1.0X 10 at 200 deg.C⁵Pa, memory elastic modulus.

The present invention is also directed to a method of using the heat resistant pressure sensitive adhesive tape of the present invention, comprising the steps of: attaching the heat resistant pressure sensitive adhesive tape to the outer pad side edge of the metal lead frame; and using the lead frame to form a semiconductor device including a semiconductor chip and a sealing resin; wherein the semiconductor chip is sealed from one side. Wherein the heat resistant pressure sensitive adhesive tape comprises: a base layer made of a polyimide resin, and a pressure-sensitive adhesive layer having a thickness of 1 to 20 μm, which is made of an acrylic resin and has a thickness of 1.0X 10 at 200 ℃⁵Pa, memory elastic modulus.

According to the present invention, if the heat-resistant pressure-sensitive adhesive tape is heated at 200 ℃ for one hour while being adhered to a stainless steel plate, the adhesive strength of the heat-resistant pressure-sensitive adhesive tape, preferably having a width of 19mm, will preferably be 5.0 newtons or less. In this case, the adhesive strength required to prevent the resin leakage in the sealing step can be secured, and after the sealing step, such an adhesive tape can be easily peeled off without causing damage to the sealing resin.

Drawings

FIGS. 1(a) -1(e) are schematic views showing an example of a process for manufacturing a semiconductor device according to the present invention;

fig. 2(a) -2(c) show an example of a lead frame used in the present invention, in which fig. 2(a) is a front view, fig. 2(b) is an enlarged schematic view of a main part, and fig. 2(c) is a sectional view showing a structure after a resin sealing step;

FIG. 3 is a longitudinal sectional view showing an example of the resin sealing step of the present invention.

Detailed Description

Specific embodiments of the present invention will be described below with reference to the accompanying drawings. Referring to fig. 1(a) -1(e), one example of a process of manufacturing a semiconductor device of the present invention is described as follows.

As shown in fig. 1(a) -1(e), the method of manufacturing a semiconductor device of the present invention comprises the steps of: mounting the semiconductor chip 15; wiring with a connection line 16; to seal the body 21 of the sealing body with the seal 17 and cut.

Referring to fig. 1(a) and 1(b), the mounting step includes bonding the semiconductor chips 15 to the die pads 11c of the lead frame 10, wherein the heat-resistant pressure-sensitive adhesive tape 20 is attached to the outer pad side edges (lower side of each drawing) of the lead frame 10.

The lead frame 10 is made of, for example, a metal such as copper, and has a formed QFN terminal pattern. The electrical contact portions of the lead frame 10 may be coated or plated with a metal, such as silver, nickel, palladium, or gold. The thickness of the lead frame 10 is typically 100-300 μm. But the thin portion formed by partial etching or the like does not have such a thickness.

The lead frame 10 preferably has a plurality of QFN patterns systematically arranged so as to be easily separated in a later cutting step. For example, referring to fig. 2(a) and 2(b), the structure of the leadframe 10 has a plurality of two-dimensional matrix patterns, referred to as matrices QFN or MAP-QFN, which is one preferred leadframe structure. In terms of productivity, in recent years, the number of packages per lead frame arrangement has increased. Therefore, not only the package representation has been made finer, but also the number of arrangements has been significantly increased, so that more packages can be sealed in one sealing portion.

Referring to fig. 2(a) and (b), the lead frame 10 has a plurality of package pattern regions 11. In each region 11, a plurality of QFN package patterns in which a plurality of terminal portions 11b are arranged around each of the adjacent openings 11a are systematically arranged. For a general QFN, each package pattern (corresponding to each lattice region in fig. 2 (a)) includes a plurality of terminal portions 11b arranged around an opening 11a, one outer lead surface on the lower side of each terminal, a die pad 11c disposed at the center of the opening 11a, and a die bar 11d supporting the die pad 11c from the four corners of the opening 11 a.

It is preferable that at least the heat-resistant pressure-sensitive adhesive tape is attached outside the package pattern area 11, and the attached area preferably includes the outer periphery of the area to be sealed in the resin. Near the side edges, the lead frame 10 typically has a plurality of lead pin holes 13 for positioning during the resin sealing step. Therefore, it is preferable to attach the adhesive tape 20 to a region not including each hole 13. A plurality of resin sealing regions are arranged in the longitudinal direction of the lead frame 10. Then, the pressure sensitive adhesive tape 20 is preferably attached so as to extend continuously over the plurality of resin sealing regions.

On the lead frame 10, a plurality of semiconductor chips 15, which are silicon wafers, each of which has a semiconductor integrated circuit formed thereon, are mounted. A plurality of mounting areas, each referred to as a die pad 11c, are provided on the lead frame 10 for holding respective semiconductor chips 15. The step of bonding (fixing) each semiconductor chip 15 to each die pad 11c can be carried out by any method, for example, by using a conductive paste 19, an adhesive tape, an adhesive, or the like. In the case of bonding using a conductive paste, a heat-curable adhesive, or the like, heat treatment is usually performed at a temperature of 150 to 200 ℃ for 30 to 90 minutes.

Referring to fig. 1(c), the wiring step includes electrically connecting connection lines 16 between an end portion of each terminal portion 11b (each inner lead) of the lead frame 10 and each electrode pad 15a of each semiconductor chip 15. For example, the connecting wires 16 are gold wires or aluminum wires. The bonding of the wiring is generally achieved by using ultrasonic oscillation energy and contact bonding energy in combination in a heated state at a temperature of 120 to 250 ℃. In this step, the surface of the heat-resistant pressure sensitive adhesive tape 20 attached to the lead frame 10 may be vacuum-sucked to be held on the thermal part (block) in a sucking manner.

Referring to fig. 1(d), the sealing step includes sealing the semiconductor chip 15 in the sealing resin 17 from one side. A sealing step is performed to protect the semiconductor chip mounted on the lead frame 10 and the connection lines 16. In the sealing step, a sealing resin 17, such as an epoxy resin, is typically molded into the die. In this case, referring to fig. 3, the sealing step is generally carried out using a die unit 18 composed of an upper die 18a and a lower die 18b each having a plurality of cavities, in which a plurality of portions are simultaneously sealed in a sealing resin 17. For example, the resin sealing is performed at a heating temperature of 180 ℃ at 170 ℃ and 180 ℃ for several minutes, and then the molding process is performed for several hours. In a preferred manner, the heat resistant pressure sensitive adhesive tape 20 is peeled off prior to the demolding process.

Referring to fig. 1(e), the dicing step includes dicing the main body 21 of the sealing body into individual semiconductor devices 21 a. In the cutting step, a rotary cutting blade such as a dicing saw is generally employed to cut each of the cutting points 17a of the sealing resin 17.

According to the present invention, the heat-resistant pressure-sensitive adhesive tape 20 used in the above-mentioned processes comprises: a base layer made of polyimide resin; and a pressure-sensitive adhesive layer having a thickness of 1 to 20 μm, made of an acrylic resin, and having a thickness of 1.0X 10 at 200 deg.C⁵Pa, memory elastic modulus. The heat-resistant pressure sensitive adhesive tape 20 is attached to the lead frame 10 in advance and then heated in the above-described processes. For example, in the step of die bonding the semiconductor chip 15, the heat treatment is generally carried out at a temperature of about 150 ℃ to about 200 ℃ for about 30 to 90 minutes. In the wiring connection step, if a large number of semiconductor devices are formed using one lead frame, bonding of all the semiconductor devices is to be completed, for example, at a temperature of about 120 ℃ to about 250 ℃, each lead frame may take 1 hour or more. The resin sealing step also requires the use of a temperature at which the resin is sufficiently melted. Such a temperature may be about 175 ℃. In this case, therefore, the heat resistant pressure sensitive adhesive tape must satisfy a required heat resistance grade.

As described above, the lead frame 10 to which the heat-resistant pressure-sensitive adhesive tape is to be attached is made of a metal such as copper, and therefore its coefficient of linear expansion is generally about 1.8X 10^-5-1.9×10^-5and/K. If the coefficient of linear expansion of the lead frame is significant and the lead frame is to be attached theretoThe heat-resistant pressure sensitive adhesive tape 20 is different, and when both are heated in an adhered state, deformation caused by the difference between the thermal expansions of both may cause warpage or peeling of the adhesive tape. Therefore, it is preferable that the coefficient of linear expansion of the base layer of the heat-resistant pressure sensitive adhesive tape is made close to that of the lead frame material.

For example, the material of such a base layer has a coefficient of linear expansion of about 1.5X 10^-5-2.8×10^-5A/K polyimide resin which can have high processability and high workability. Such materials are preferably used in the present invention. The coefficient of linear expansion herein is a value determined by thermo-mechanical analysis (TMA) according to ASTM D696.

Examples of such a film made of polyimide resin include Kapton^®(Du Pont-Toray Co., Ltd.), Utilix (trade name) (Ube Industries, Ltd.), and Apical^®(Kaneka Corporation), etc.

The thickness of the base layer of the heat-resistant pressure-sensitive adhesive tape 20 is preferably 10 to 100 μm from the viewpoint of preventing breakage or cracks and having good workability.

The adhesive layer of the heat-resistant pressure-sensitive adhesive tape 20 should have a certain degree of elasticity in terms of pressure-sensitive adhesive function. However, if the adhesive layer as a whole is too soft, the lead frame to which the pressure sensitive adhesive tape is attached may not be sufficiently fixed due to the elastic force of the pressure sensitive adhesive layer in the connection step of the connection lines. As a result, the contact bonding energy of the pressing can be reduced, and a failure may occur in the bonding step.

According to the present invention, in order to avoid the failure of such bonding, a sufficient adhesive strength is secured to prevent the resin leakage in the sealing step, or to secure the performance different from each other, the memory elastic modulus of the pressure-sensitive adhesive layer should be 1.0X 10⁵Pa or more, preferably 5.0X 10⁵Pa or more, and a thickness of 1 to 20 μm, preferably 5 to 15 μm. Such a pressure-sensitive adhesive layer as a whole can maintain a light gasket property, so that wiring connection can be suitably achieved in a more reliable manner.Such a pressure-sensitive adhesive layer having an appropriate thickness can give sufficient sealing performance in the sealing step. The memory elastic modulus herein is a shear memory elastic modulus determined by a viscoelastic spectrometer under conditions of 1Hz and a temperature rise rate of 5 ℃/min.

The heat-resistant pressure sensitive adhesive tape is peeled off at any stage after the sealing step. If the adhesive strength of the pressure sensitive adhesive tape is too strong, it is difficult to achieve such peeling, and in some cases, the molded resin may be peeled off or broken due to the peeling stress of the adhesive tape. Therefore, a pressure-sensitive adhesive layer having a stronger adhesive strength than necessary for preventing the overflow of the sealing resin is not preferred. In this regard, after being heated at 200 ℃ for 1 hour while being adhered to the stainless steel sheet, the pressure sensitive adhesive tape having a width of 19mm has a bonding strength of preferably 5.0N or less, and particularly preferably 2.0N or less, as measured by JIS Z0237.

A preferred example of the pressure-sensitive adhesive layer having the above-described physical properties is an acrylic pressure-sensitive adhesive layer, which can easily provide a suitable memory elastic modulus and a suitable adhesive strength. For example, such a binder comprises an acrylic copolymer formed by copolymerizing monomers containing at least an alkyl (meth) acrylate. Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, (2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, and dodecyl (meth) acrylate.

The acrylic pressure-sensitive adhesive layer having heat resistance may comprise an acrylic polymer formed by copolymerizing a mixture of monomers of an imide group-containing alkyl (meth) acrylate and an alkyl (meth) acrylate.

Each of these acrylic pressure sensitive adhesives contains a suitable crosslinking agent. Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, and chelate crosslinking agents. The amount of the crosslinking agent is not particularly limited, but it is preferable to add the crosslinking agent in such an amount as to produce sufficient crosslinking for the purpose of achieving the desired elastic modulus. For example, such an amount is preferably 0.1 to 15 parts by weight per 100 parts by weight of the acrylic polymer; more preferably 1.0 to 10 parts by weight.

In the present invention, the memory elastic modulus at 200 ℃ can be adjusted within a desired region by adding a relatively large amount of the crosslinking agent. In addition, for the purpose of adjusting the memory elastic modulus, the kind of a crosslinking agent, the kind of the monomer, the crosslinking ratio, or the molecular weight of a material may be changed; or a filler may be added.

The acrylic binder may comprise any other components. Examples of any of the other components include various kinds such as plasticizers, fillers, pigments, dyes, antioxidants, antistatic agents, and the like. The acrylic pressure-sensitive adhesive described above has relatively high heat resistance and can easily provide a suitable memory elastic modulus and a suitable adhesive strength, and therefore, it is preferably used in the present invention. In addition, if necessary, recoating including primer pretreatment of the pressure-sensitive adhesive layer or back treatment of the base material may be carried out.

As described above, the heat-resistant pressure-sensitive adhesive tape used in the method of the present invention comprises a base layer and an acrylic pressure-sensitive adhesive layer. Such a heat-resistant pressure-sensitive adhesive tape can be attached to the lead frame in any case. Various apparatuses and methods for thermal laminators, hot rolls, pressure rolls can be used in the step of attaching the heat resistant pressure sensitive adhesive tape. Generally, a method using a pressing roller is widely used to attach the adhesive tape to the lead frame.

Examples of the invention

The following examples particularly illustrate the features and effects of the present invention.

Example 1

A polyimide film (Kapton) having a thickness of 25 μm was formed^®100H，Du Pont-Toray Co.，Ltd.) as a base layer material. The linear expansion coefficient of the polyimide film was about 2.6X 10^-5-2.8×10^-5K, as measured by a temperature ramp rate of 10 ℃/min between 100 ℃ and 200 ℃. An acrylic copolymer comprising 100 parts by weight of a butyl methacrylate monomer and 5 parts by weight of a methacrylic acid monomer was used. To 100 parts by weight of this copolymer, 2 parts by weight of an epoxy crosslinking agent (Tetrad-C, Mitsubishi Gas Chemical Company, Inc.) was added to form an acrylic pressure-sensitive adhesive layer. A pressure-sensitive adhesive tape comprising a base material and an acrylic pressure-sensitive adhesive layer formed on the base material to form the pressure-sensitive adhesive tape and having a thickness of 10 μm. The pressure sensitive adhesive tape has a thickness of 9.0X 10 at 200 deg.C⁵Pa, as measured in shear memory elasticity mode from parallel plates having a sample size of 7.9mm φ by ARES (Rheometric Scientific F.E.Ltd.) at 1Hz and a temperature ramp rate of 5 ℃/min. The heat-resistant pressure sensitive adhesive tape was heated at 200 ℃ for 1 hour while being adhered to a stainless steel sheet. The adhesive tape was then tested for adhesive strength according to JISZ 0237. The bond strength measured for the adhesive tape having a width of 19mm was 0.3 newton.

A heat resistant pressure sensitive adhesive tape was attached to the outer pad side of a copper lead frame, each terminal portion of which was silver plated and had a 4 x 4 matrix of 16-pin side type QFN. Each semiconductor chip was bonded to each die pad portion of the lead frame using an epoxy phenol-based silver paste and fixed by treatment at 180 ℃ for about 1 hour.

The lead frame is then vacuum sucked to the heat resistant pressure sensitive adhesive tape side to be fixed to a thermal part heated at 200 ℃. The peripheral portion of the lead frame is also held by the bent caulking pieces. Then, the semiconductor chips were wire-bonded with gold wires of 25 μm φ (GMG-25, Tanaka precision Metals) in a 115kHz switch (UTC-300Bisuper, Shinkawa Ltd.) under the following conditions. For about 1 hour to complete the binding.

First bonding pressure: 80g of

Ultrasonic intensity in first bonding: 550mW

First bonding time: 10ms

Second bonding pressure: 80g of

Ultrasonic intensity in second bonding: 550mW

First bonding time: 8ms

After that, the semiconductor chip was sealed in an epoxy sealing resin (HC-300, Nitto Denko Corporation) using a mold injection machine (Model-Y-series, TOWA Corporation). The injection molding was carried out under the following conditions: preheat at 175 ℃ for 3 seconds, inject time 12 seconds, and treat time 90 seconds. The pressure sensitive adhesive tape is then peeled off. After the demolding, for the purpose of sufficient treatment, further treatment was carried out at 175 ℃ for about 3 hours, and the body of the sealing body was cut into each QFN type semiconductor device by a diamond wheel dicer.

The resulting QFNs do not suffer from resin overflow and the steps including connecting leads can be smoothly performed without trouble.

Example 2

Each QFN type semiconductor device was formed using the procedure of example 1 except that the pressure-sensitive adhesive layer of the heat-resistant pressure-sensitive adhesive tape was 15 μm in thickness. The resulting QFN has no resin overflow, and the steps including connecting leads can be smoothly carried out without trouble.

Example 3

The procedure of example 1 was used to form a heat resistant pressure sensitive adhesive tape, except that the epoxy crosslinking agent was added in an amount of 0.5 parts by weight. The obtained pressure-sensitive adhesive tape had a memory elastic modulus of 2.0X 10 at 200 deg.C⁵Pa, and after heat treatment at 200 ℃ for the pressure-sensitive adhesive tape having a width of 19mmThe bond strength of (a) is about 2.5 newtons. The pressure sensitive adhesive layer of the adhesive tape has a thickness of about 5 μm. The heat-resistant pressure-sensitive adhesive tape was then attached to the outer pad side of the copper lead frame used in example 1, and the respective semiconductor chips were bonded under the conditions described below. And then vacuum-sucked from the side of the heat-resistant pressure sensitive adhesive tape so as to be fixed to the thermal part at 200 c. The peripheral portion of the lead frame is also held by the bent caulking pieces. The semiconductor chips were then wire bonded with 25 μm φ gold wires (GLD-25, tanaka Precious Metals) in 60kHz connectors (MB-2000, Nippon Avionics Co., Ltd.) under the following conditions. For about 1 hour to complete the binding.

First bonding pressure: 30g of

Ultrasonic intensity in first bonding: 25mW

First bonding time: 100ms

Second bonding pressure: 200g

Ultrasonic intensity in second bonding: 50mW

Second bonding time: 50ms

After that, the semiconductor chip was sealed in an epoxy sealing resin (HC-300, Nitto Denko Corporation) using a mold injection machine (Model-Y-series, TOWA Corporation). The injection molding was carried out under the following conditions: preheating at 175 deg.C for 40 seconds, injection time 11.5 seconds, and treatment time 120 seconds. The pressure sensitive adhesive tape is then peeled off. After the demolding, for the purpose of sufficient treatment, further treatment was carried out at 175 ℃ for about 3 hours, and the body of the sealing body was cut into each QFN type semiconductor device by a diamond wheel dicer.

The resulting QFNs do not suffer from resin overflow and the steps including connecting leads can be smoothly performed without trouble.

Comparative example 1

The base layer, except for the adhesive tape, was a high density polyethylene film (thickness 25 μm, coefficient of linear expansion 15X 10)^-5K) In addition, the procedure of example 1 was employed for the study. Upon heat curing in the step of mounting the semiconductor chip, significant wrinkles and local peeling are generated in the adhesive tape. The adhesive tape cannot fundamentally suppress the overflow of the resin at the injection molding step.

Comparative example 2

The procedure of example 1 was employed for the study except that the pressure-sensitive adhesive tape comprised a pressure-sensitive adhesive layer of a polyester base material and a silicon-based pressure-sensitive adhesive of 50 μm thickness so that the adhesive strength of the pressure-sensitive adhesive tape of 19mm width after heating at 200 ℃ was 7 newtons. As a result, most of the wiring cannot be sufficiently bonded at the second bonding due to cushion of the adhesive tape, and damage of the bonding frequently occurs at the bonding step. When the adhesive tape is peeled off after the sealing step, the lead frame is deformed by stress, and part of the sealing resin is also peeled off.

Comparative example 3

Except that a memory elastic modulus of 1.1X 10 at 200 ℃ is used⁴Pa of the silicon-based pressure-sensitive adhesive, except for forming a pressure-sensitive adhesive layer having a thickness of 30 μm, the procedure of example 1 was employed for the study. In the bonding step, most of the wirings cannot be sufficiently bonded due to cushion of the adhesive tape, and breakage of the bonding frequently occurs.

Claims (6)

1. A method of making a semiconductor device, comprising the steps of:

placing and bonding a plurality of semiconductor chips on respective die pads of a metal lead frame, said lead frame having outer pad side edges with heat resistant pressure sensitive adhesive tape attached thereto;

wiring a connecting lead between each terminal of the lead frame and each electrode pad on the semiconductor chip;

dicing the body of the encapsulant into a plurality of separate semiconductor devices;

cutting the body of the encapsulant into separate individual semiconductor devices, wherein,

the heat-resistant pressure-sensitive adhesive tape comprises a base layer made of a polyimide resin and a pressure-sensitive adhesive layer having a thickness of 1 to 20 μm, made of an acrylic resin, and having a thickness of 1.0X 10 at 200 DEG C⁵Pa, memory elastic modulus.

2. The method of claim 1, wherein if the heat resistant pressure sensitive adhesive tape is heated at 200 ℃ for 1 hour while being adhered to a stainless steel plate, the heat resistant pressure sensitive adhesive tape having a width of 19mm has an adhesive strength of at most 5.0 newtons.

3. A heat resistant pressure sensitive adhesive tape for use in the method of claim 1, comprising:

a base layer made of polyimide resin; and

a pressure-sensitive adhesive layer having a thickness of 1 to 20 μm, which is made of an acrylic resin and has a thickness of 1.0X 10 at 200 DEG C⁵Pa, memory elastic modulus.

4. The adhesive tape as claimed in claim 3, wherein if said heat resistant pressure sensitive adhesive tape is heated at 200 ℃ for 1 hour while being adhered to a stainless steel plate, the adhesive strength of said heat resistant pressure sensitive adhesive tape having a width of 19mm is at most 5.0N.

5. A method of using a heat resistant pressure sensitive adhesive tape comprising the steps of:

attaching the heat resistant pressure sensitive adhesive tape to the outer gasket side edge of the metal lead frame;

forming a semiconductor device with the lead frame, the device including semiconductor chips and a sealing resin in which the semiconductor chips are sealed from one side, wherein

The heat-resistant pressure-sensitive adhesive tape includes a base layer made of a polyimide resin; and a pressure-sensitive adhesive layer having a thickness of 1 to 20 μm, which is made of an acrylic resin and has a thickness of 1.0X 10 at 200 ℃⁵Pa, memory elastic modulus.

6. The method of claim 5, wherein the heat resistant pressure sensitive adhesive tape having a width of 19mm has an adhesive strength of at most 5.0 newtons if the heat resistant pressure sensitive adhesive tape is heated at 200 ℃ for 1 hour while being adhered to a stainless steel plate.