JPH0790244A - Electrically conductive adhesive sheet - Google Patents

Abstract

PURPOSE:To obtain the sheet excellent in resistance to moisture and hydrolysis, causing no warpage or cracking of semiconductor chips applied therewith, by releasably setting on a substrate film an adhesive essentially comprising each specific polyimide resin and high-molecular weight rubber and electrically conductive powder. CONSTITUTION:The objective electrically conductive adhesive sheet can be obtained by setting on a substrate film an adhesive essentially comprising (A) a polyimide resin of formula I [R<1> is tetravalent organic acid residue, a biphenyl ether tetracarboxylic acid of formula II accounts for >=50mol% of the total acid components constituting R<1>; R<2> is divalent diamine residue, a diamine compound of formula III (X is CH2, O, etc.) accounts for 50-99mol% of the total diamine components constituting R<2> and a diaminosiloxane of formula IV (R<3> and R<4> are each divalent organic group; R<5>-R<8> are each 1-6C hydrocarbon; n is 0-12) 50-1mol%], (B) a high-molecular weight rubber >=10000 in weight- average molecular weight and (C) electrically conductive powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for assembly of semiconductor devices, etc., and is free from warpage and voids of semiconductor chips, and is coated with an adhesive suitable for large-sized semiconductor chips and surface mounting. The present invention relates to a conductive adhesive sheet that can be transferred to the body.

[0002]

2. Description of the Related Art ICs and Ls are mounted on a predetermined portion of a lead frame.
The process of connecting semiconductor chips such as SI is one of the important processes that affect the long-term reliability of the device. Conventionally, as this connection method, the silicon surface of the semiconductor chip is pressed and pressure-bonded to the gold-plated surface on the lead frame.
The Si eutectic method was the mainstream. However, in recent years, the soaring price of precious metals, especially gold, has triggered Au in resin-sealed semiconductor devices.
The transition from the -Si eutectic method to a method using solder, a method using a conductive paste, etc. has been made rapidly.

However, although the method using solder has been partially put into practical use, it has been pointed out that solder or solder balls scatter and adhere to electrodes or the like, which causes corrosion breakage. On the other hand, in the method using a conductive paste, an epoxy resin mixed with silver powder is usually used, and it has been partially put into practical use. However, in terms of reliability, it should be more satisfactory than the Au-Si eutectic method. I couldn't get the kimono. The method of using the absolutely conductive paste has advantages such as excellent heat resistance as compared with the solder method, but on the other hand, since the resin and the curing agent are not prepared for bonding semiconductor chips, generation of voids, moisture resistance and resistance Inferior in hydrolyzability, it promotes corrosion of aluminum electrodes and often causes disconnection failure. The reliability of the device is Au-S.
i It was inferior to the eutectic method. In recent years, IC and LS
With the increase in the size of semiconductor chips such as I and LEDs, chip cracks are generated and the adhesive strength is reduced, resulting in a decrease in the reliability of the device.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks and is excellent in moisture resistance, hydrolysis resistance and adhesiveness, less warpage of semiconductor chips, voids and It is an object of the present invention to provide a highly reliable conductive adhesive sheet which is free from chip cracks and is compatible with large-sized semiconductor chips and surface mounting.

[0005]

As a result of earnest studies to achieve the above object, the present inventor has found that the adhesive described below can achieve the above object, and completed the present invention.

That is, the present invention provides (A) a polyimide resin represented by the following general formula:

[0007]

[Chemical 5] (A) R ¹ in the general formula of the polyimide resin is 4
Showing a divalent organic acid residue, 50 mol% or more of all the acid components constituting R ¹ is a biphenyl ether tetracarboxylic acid represented by the following general formula,

[0008]

[Chemical 6] (B) R ² in the general formula of the polyimide resin is 2
A diamine residue having a valence of 50 to 99 mol% of all the diamine components constituting (b-1) R ² is a diamine compound represented by the following general formula:

[0009]

[Chemical 7] (However, in the formula, X is —CH ₂ —, —O—, —C (CH ₃ ) _{2
-, - SO 2 -, -} C (CF 3) 2 - represents a) (b-2)
50 to 1 mol% of all diamine components constituting R ²
Is a diaminosiloxane represented by the following general formula:

[0010]

[Chemical 8] (However, in the formula, R ³ and R ⁴ are divalent organic groups, R ^{5 to} R 4
⁸ represents a hydrocarbon having 1 to 6 carbon atoms, and n represents a positive integer of 0 or 12), and (B) a high molecular weight rubber having a weight average molecular weight of 10,000 or more (C) a conductive powder. It is a conductive adhesive sheet characterized in that a conductive adhesive as an essential component is removably fixed on a support film.

The present invention will be described in detail below.

The (A) polyimide resin used in the present invention has the above-mentioned general formula 5, and has (a) an acid component and (b)
It is obtained by reacting with a diamine component.

As the (a) acid component used in the polyimide resin, the biphenyl ether tetracarboxylic acid component represented by the above general formula 6 can be used. Specific examples of the biphenyl ether tetracarboxylic acid component include 3,4,3 ′, 4′-biphenyl ether tetracarboxylic acid, 2,3,3 ′, 4′-biphenyl ether tetracarboxylic acid, or acids thereof. An anhydride, a lower alkyl ester, etc. are mentioned, These can be used individually or in mixture. It is desirable to use the biphenyl ether tetracarboxylic acid component in an amount of 50 mol% or more of the total acid component. If it is less than 50 mol%, the acid resistance is poor and it is not preferable.

Acid components other than biphenyl ether tetracarboxylic acid include, for example, pyromellitic acid, 3,3 ',
4,4'-biphenyltetracarboxylic acid, 2,3,3 ', 4'-
Biphenyl tetracarboxylic acid, 3,3 ', 4,4'-benzophenone tetracarboxylic acid, 2,3,3', 4'-benzophenone tetracarboxylic acid, 1,4,5,8-naphthalene tetracarboxylic acid, 2, 3,6,7-Naphthalenetetracarboxylic acid, 1,2,5,6-
Naphthalenetetracarboxylic acid, 3,4,9,10-tetracarboxyphenylene, 3,3 ', 4,4'-biphenylmethanetetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl)
Propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,3 ', 4,4'-diphenylsulfone tetracarboxylic acid, 2,2-bis ([4- (3,4- Examples thereof include anhydrides such as dicarboxyphenoxy) phenyl] hexafluoropropane and lower alkyl esters, which can be used alone or in combination with the above-mentioned biphenyl ether tetracarboxylic acid.

As the (b) diamine component used in the polyimide resin, the (b-1) diamine compound and the (b-2) diaminosiloxane are used together in a fixed ratio.

Specific examples of the (b-1) diamine compound include 2,2-bis [4- (4-aminophenoxy) phenyl] propane and 2,2-bis [4- (4-aminophenoxy). ) Phenyl] hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] ether, 2,2-
Bis [4- (4-aminophenoxy) phenyl] methane, 2,
2-bis [4- (4-aminophenoxy) phenyl] sulfone and the like can be mentioned, and these can be used alone or in combination. This diamine compound and the below-mentioned diaminosiloxane are used together in a fixed ratio.

As the (b-2) diaminosiloxane, one having the above general formula 8 is used. Specific examples of the compound include bis (γ-aminopropyl) tetramethyldisiloxane, bis (4-aminobutyl) tetramethyldisiloxane, bis (γ-aminopropyl) tetraphenyldisiloxane, 1,4-bis ( (γ-aminopropyldimethylsilyl) benzene and the like can be used, and these can be used alone or in combination.

As the diamine component, it is important to use the above-mentioned (b-1) diamine compound and (b-2) diaminosiloxane together in a fixed ratio. The mixing ratio of these is such that (b-1) diamine compound is based on all diamine components.
50-99 mol%, 50% of (b-2) diaminosiloxane
It is desirable to mix them in a proportion of ~ 1 mol%. When the content of the (b-1) diamine compound is less than 50 mol%, the chemical resistance is lowered, and the (b-2) diaminosiloxane is less than 1 mol%.
If it is less than mol%, the compatibility with the high molecular weight rubber component is poor,
Adhesion to an inorganic film (silicon dioxide film or silicon nitride film) of a semiconductor device or the like is lowered, which is not preferable.

The polyimide resin obtained by reacting the acid component and the diamine component described above may contain the acid component and the diamine component in a block or random manner.

This polyimide resin is a precursor of polyamic acid resin 0.5 g / N-methyl-2-pyrrolidone.
As a 10 ml concentrated solution, the logarithmic viscosity at 30 ° C is 0.2.
It is preferably in the range of to 4.0, more preferably
It is in the range of 0.3 to 2.0. The polyamic acid resin is obtained by subjecting an acid component and a diamine component of approximately equimolar amounts to an addition polymerization reaction in an organic solvent at a reaction temperature of 30 ° C. or lower, preferably 20 ° C. or lower for 3 to 12 hours. Examples of the organic solvent in this polymerization reaction include N, N'-dimethyl sulfoxide, N, N'-dimethylformamide, N, N'-diethylformamide, N, N'-dimethylacetamide,
N, N'-diethylacetamide, N-methyl-2-pyrrolidone, hexamethylenephosphoamide and the like can be mentioned, and these can be used alone or in combination.

(B) Weight average molecular weight 1000 used in the present invention
Examples of the high molecular weight rubber of 0 or more include acrylic rubber,
Various copolymer rubbers such as acrylonitrile-butadiene rubber, modified acrylonitrile-butadiene rubber, and polyvinyl butyral can be used, and these can be used alone or in combination of two or more. When the weight average molecular weight of the high molecular weight rubber is less than 10,000, sufficient flexibility cannot be obtained and wetting is poor, which is not preferable. The blending ratio of the high molecular weight rubber having a weight average molecular weight of 10,000 or more is preferably in the range of 5 to 40% by weight based on the above-mentioned polyimide resin. If the proportion is less than 5% by weight, the adhesion to various substrates is not sufficient, and if it exceeds 40% by weight, the polyimide resin and the rubber component are likely to be separated from each other, which is not preferable. As a method of mixing the high molecular weight rubber with the polyamic acid resin described above, a solution in which a rubber component is previously dissolved in an appropriate solvent can be mixed with the polyamic acid resin solution and stirred to be manufactured.

Examples of the conductive powder (C) used in the present invention include metal powders such as silver powder, copper powder and nickel powder, which are not particularly limited and may have a conductive layer on the surface. The conductive powder can be widely used. These can be used alone or in combination.

The method for producing a conductive adhesive sheet of the present invention comprises:
The ingredients are blended and uniformly kneaded with a three-roll mill or the like to obtain a paste-like material. At this time, if the rubber etc. is solid,
Alternatively, when the viscosity is high in operation, it is also possible to dilute with an organic solvent as necessary, mix the components, and knead uniformly. The paste-like material obtained is evenly coated on a support film and heated to remove the solvent, and the thickness is 5 to 100 μm.
A film-like conductive adhesive sheet can be produced to some extent. The support film used here is not particularly limited as long as it is not adversely affected by the solvent removal step, and examples thereof include a polyethylene film and a polyolefin polymer film, which can be widely used.

The obtained conductive adhesive with a supporting film is
When heated, it improves the release properties between the support film and the conductive adhesive and allows the transfer to the adherend without leaving the adhesive on the support film. To give a specific example, the semiconductor device is a die bonding adhesive on the back surface of the wafer before the dicing process, the conductive adhesive sheet is laminated, hot air oven, heat block, hot air dryer, etc., at 50 ~ 100 ℃. Only the conductive adhesive can be transferred to the backside of the wafer by heating to the temperature for 5 to 60 seconds.
The obtained wafer with conductive adhesive is diced by a normal method, and each dicing semiconductor chip is mounted together with the conductive adhesive on a lead frame in the same manner as a normal assembly process, and the temperature is set to 120 to 200 ° C. It is used after being heated and cured on a heat block for several tens of seconds to several minutes. Further, it can be used by curing in an oven at a temperature of 150 to 200 ° C. for several minutes to several hours.

[0025]

The conductive adhesive sheet of the present invention uses a conductive adhesive containing a specific polyimide resin, a specific synthetic rubber and conductive powder as essential components, and has no warp deformation of a large chip. There is no generation of voids and chip cracks, and good transfer from the support film to the adherend can be achieved.

[0026]

EXAMPLES The present invention will now be described with reference to examples, but the present invention is not limited to these examples.

Example 1 In a flask equipped with a stirrer, a condenser and a nitrogen introducing tube,
2,2-bis [4- (4-aminophenoxy) phenyl] propane 36.9g (0.09mol) and bis (γ-aminopropyl)
2.49 g (0.01 mol) of tetramethyldisiloxane and N-
Methyl-2-pyrrolidone (268.3 g) was added, and 30.38 g (0.098 mol) of 3,3 ′, 4,4′-biphenyl ether tetracarboxylic dianhydride was added at room temperature under a nitrogen atmosphere while paying attention to the rise of the solution temperature. The mixture was added in portions and stirred at room temperature for 12 hours to obtain a polyamic acid resin solution. A part of this polyamic acid resin solution was reprecipitated with methanol, the obtained white polyamic acid resin powder was dissolved with N-methyl-2-pyrrolidone, and
When the logarithmic viscosity at 30 ° C. was measured at a concentration of 5 g / 100 ml, it was 0.95 dl / g. This polyamic acid resin solution
100 parts by weight (80% solution of N-methyl-2-pyrrolidone) and 70% solution of methyl ethyl ketone in Nipol 1072 (manufactured by Zeon Corporation, trade name, molecular weight 500,000) 6 parts by weight and silver powder 78
Parts by weight were mixed and kneaded three times with a three-roll to obtain a conductive adhesive.

This conductive adhesive was cast on a polypropylene film having a thickness of 40 μm and dried and semi-cured at 80 ° C. for 60 minutes to produce a conductive adhesive sheet having an adhesive layer having a thickness of 20 μm. did. Using this conductive adhesive sheet, the conductive adhesive was transferred to the back surface of the silicon wafer on a heat block at 80 ° C. In addition, the silicon wafer with conductive adhesive is fully diced, and the semiconductor chip with conductive adhesive is
A semiconductor device was manufactured by adhesive-curing for 2 minutes at ℃.

Example 2 In a flask equipped with a stirrer, a cooler and a nitrogen introducing tube,
2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane 46.6 g (0.09 mol) and bis (γ-aminopropyl) tetraphenyldisiloxane 4.97 g (
0.01 mol) and 268.3 g of N-methyl-2-pyrrolidone were added, and 15.50 g (0.050 mol of 0.053 mol of 3,3 ', 4,4'-biphenyl ether tetracarboxylic acid dianhydride under nitrogen atmosphere at room temperature.
) And pyromellitic dianhydride (10.46 g (0.048 mol)) are added in portions while paying attention to the increase in solution temperature, and the mixture is added at room temperature to 10
After stirring for a time, a polyamic acid resin solution was obtained. This polyamic acid resin powder was dissolved in N-methyl-2-pyrrolidone to a concentration of 0.5 g / 100 ml, and the logarithmic viscosity at 30 ° C. was measured and found to be 0.88 dl / g. 100 parts by weight of this polyamic acid resin solution (80% solution of N-methyl-2-pyrrolidone) and 70% solution of methyl ethyl ketone JSRN 6328
(Nippon Synthetic Rubber Co., Ltd., trade name, molecular weight 300,000) 12 parts by weight and silver powder 80 parts by weight were mixed and kneaded three times with a three-roll to obtain a conductive adhesive.

Using this conductive adhesive, it was cast on a polypropylene film having a thickness of 40 μm and dried and semi-cured at 80 ° C. for 60 minutes to produce a conductive adhesive sheet having an adhesive layer having a thickness of 20 μm. did. Using this conductive adhesive sheet, the conductive adhesive was transferred to the back surface of the silicon wafer on a heat block at 80 ° C. In addition, the silicon wafer with conductive adhesive is fully diced, and the semiconductor chip with conductive adhesive is
A semiconductor device was manufactured by adhesive-curing for 2 minutes at ℃. Comparative Example 1 A semiconductor device was manufactured by using the conductive adhesive obtained in Example 1 to bond and cure a semiconductor chip and a lead frame in an oven at 200 ° C. for 60 minutes. Comparative Example 2 A semiconductor device was manufactured by using the conductive adhesive obtained in Example 2 to bond and cure a semiconductor chip and a lead frame in an oven at 200 ° C. for 60 minutes.

For these semiconductor devices, the adhesive strength,
The warpage of the semiconductor chip, the presence or absence of voids in the adhesive layer, and the moisture resistance test were conducted. The results are shown in Table 1. The characteristics of the present invention were excellent, and the effects of the present invention could be confirmed.

[0032]

[Table 1] * 1: Silver-plated lead frame (copper, 200 μm)
2 × 2 mm and 4 × 12 mm semiconductor chips were bonded onto the top of the substrate and the shear force was measured using a push-pull gauge at temperatures of 25 ° C. and 350 ° C. * 2: The presence or absence of voids on the back surface of the semiconductor chip was evaluated.
○ mark: No void was generated, × mark: Void was generated. * 3: The surface of the semiconductor chip after wire bonding was measured with a surface roughness meter, and the distance between the center part and the end part of the semiconductor chip was measured. * 4: Measured with a volume resistivity meter.

[0033]

As is apparent from the above description and Table 1, the conductive adhesive sheet of the present invention is excellent in moisture resistance, hydrolysis resistance and adhesiveness, has less warpage of semiconductor chips, and is free from voids and voids. It does not generate chip cracks and is highly reliable for large semiconductor chips and surface mounting.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area C09J 121/00 JEB H01B 1/22 D H01L 21/52 E

Claims (1)

[Claims] 1. A polyimide resin represented by the following general formula (A), wherein: (A) R ¹ in the general formula of the polyimide resin is 4
A divalent organic acid residue is shown, and 50 mol% or more of all the acid components constituting R ¹ is a biphenyl ether tetracarboxylic acid represented by the following general formula: (B) R ² in the general formula of the polyimide resin is 2
A diamine residue having a valence of 50 to 99 mol% of all the diamine components constituting (b-1) R ² is a diamine compound represented by the following general formula: (However, in the formula, X is —CH ₂ —, —O—, —C (CH ₃ ) _{2
-, - SO 2 -, -} C (CF 3) 2 - represents a) (b-2)
50 to 1 mol% of all diamine components constituting R ²
Is a diaminosiloxane represented by the following general formula: (However, in the formula, R ³ and R ⁴ are divalent organic groups, R ^{5 to} R 4
⁸ represents a hydrocarbon having 1 to 6 carbon atoms, n represents 0 or a positive integer of 12 or less), and (B) a high molecular weight rubber having a weight average molecular weight of 10,000 or more (C) conductive powder An electrically conductive adhesive sheet, comprising a support film and an electrically conductive adhesive containing, as an essential component, releasably fixed on the support film.