JPH10130594A - Heat resistant bonding sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat resistant bonding sheet manifesting low coefficient of water absorption, low dielectric characteristics excellent in mechanical strength, processing characteristics, adhesive properties, dimensional stability, suitable for high density mounting, etc., by using a specific polymide film as a base film. SOLUTION: This sheet uses the polyminde film as a base film obtained by establishing a heat resistant adhesive layer comprising a thermoplastic polyimide copolymer obtained by cyclodehydration of the compounds expressed by formula II (R5 , R6 are each a divalent organic group; R7 is a quadrivalent organic group; 1<=p; 0<=q), on one or both surfaces of a heat resistant base film such as polyimide film, etc., obtained by cyclodehydration of a copolymide acid expressed by formula I (R1 , R2 are each a divalent organic group; R3 is a quadrivalent organic group; 1<=1; 0<=m), having 15ppm <= of coefficient of hygroscopic expansion. The heat resistant base film is preferably a polyimide film having 4-25ppm <= of coefficient of heat expansion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant bonding sheet, and more particularly, to a base film used for a film or a tape which requires heat resistance for fixing or insulating electronic parts and electronic circuit boards. And a heat-resistant bonding sheet having a three-layer structure in which adhesive layers are provided on both surfaces of the heat-resistant bonding sheet. Particularly, it is used for die pad bonding of a flexible printed circuit board (hereinafter, abbreviated as FPC) or a semiconductor element, or COL (Chip on Lead) or LOC.
The present invention relates to a heat-resistant bonding sheet that can be suitably used as a mounting material for (Lead on Chip) and the like.

[0002]

2. Description of the Related Art In recent years, electronic devices have become more sophisticated and more sophisticated.
With miniaturization progressing, there has been a demand for miniaturization and weight reduction of electronic components used accordingly. For this reason, a semiconductor element packaging method and a wiring material or a wiring component for mounting the same are required to have higher density, higher function and higher performance. In particular, semiconductor packages, COL and LOC packages, MCMs (Mu
There is a need for an insulating adhesive material exhibiting good adhesive properties that can be suitably used as a high-density mounting material such as an lti chip module), a printed wiring board material such as a multilayer FPC, and an aerospace material.

In general, an epoxy resin or an acrylic resin is used as an insulating adhesive material used for electronic parts and electronic materials because it can be processed at a low temperature (200 ° C. or lower) and is easy to handle. In many cases, these adhesive materials are also used for bonding a lead frame and an element when manufacturing a semiconductor element.

[0004] However, these adhesive materials are easy to handle at low temperatures, but have a problem of poor heat resistance at high temperatures. In addition, there is also a problem that the manufacturing process is complicated because the usage form is used in the form of a solution. Furthermore, since bonding requires a long curing time and a gas is generated at the time of curing, for example, when used for bonding a lead frame and a semiconductor element, the element surface is contaminated by the gas, and the lead frame and the element are bonded. There is also a problem that the adhesiveness is deteriorated and the product yield is deteriorated. Therefore, especially for high-density packaging materials such as when manufacturing semiconductor elements, there is a strong demand for a further high-performance adhesive material.

As an adhesive meeting such demands, polyimide having high heat resistance and mechanical strength and excellent electrical properties is promising due to its excellent properties. However, in general, polyimide is almost insoluble or infusible in a ring-closed state, and is used as an organic insulating material for a base film for FPC or TAB, but has hardly been applied as an adhesive.

For this reason, there have recently been proposed examples of polyimides which can be used as adhesives, for example, Japanese Patent Application Laid-Open No. Hei 2-138789 discloses 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride. Using an adhesive film obtained from a resin composition obtained by mixing an aromatic polyimide obtained from a product and an aromatic diamine and a polymaleimide, a method for producing an FPC in which a base material such as a polyimide film is bonded to a copper foil has been proposed. I have. Also, Japanese Patent Application Laid-Open No. 5-1792
No. 24 and Japanese Patent Application Laid-Open No. 5-112768 propose various types of thermoplastic polyimide adhesive materials which can be heated and pressed.

[0007]

However, these polyimide-based adhesive materials improve the melt fluidity of polyimide and can be used as an adhesive, but require a high temperature and a long time for adhesion. There was a problem in workability. In addition, there is also a problem that electric characteristics are easily deteriorated after moisture is easily absorbed.

Accordingly, the present inventors have solved the above-mentioned problems, and have excellent heat resistance, workability, and adhesiveness while exhibiting sufficient mechanical strength, and exhibit particularly low water absorption and low dielectric properties. As a result of intensive studies for the purpose of providing a heat-resistant bonding sheet having excellent properties such as excellent dimensional stability, the present invention has been achieved.

[0009]

Means for Solving the Problems As a result of intensive studies to achieve this object, a heat-resistant bonding sheet having a heat-resistant adhesive layer provided on one or both sides of a heat-resistant base film has been developed. Reached.

That is, the gist of the heat-resistant bonding sheet according to the present invention is that a heat-resistant adhesive layer is provided on one or both sides of a heat-resistant base film, and a polyimide film having a coefficient of hygroscopic expansion of 15 ppm or less is used. Film.

Further, the heat-resistant base film is made of a polyimide film having a coefficient of thermal expansion of 4 to 25 ppm.

Further, the heat-resistant base film comprises a polyimide film having a water absorption of 1.5% or less.

The heat-resistant base film is represented by the following general formula (1):

[0014]

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(Wherein, R ₁ is a divalent organic group, R ₂ is a divalent organic group, R ₃ is a tetravalent organic group. L and m are integers, and 1 ≦ l, 0 ≦ m) is obtained from a polyimide film obtained by dehydrating and ring-closing a polyamic acid copolymer represented by the following formula:

Further, when the heat-resistant base film is such that R ₁ in the general formula (1) is

[0017]

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[0018] is at least one divalent organic group selected from, wherein R _{4 is, CH 3 -, Cl-, Br-} , F-,
CH ₃ O—, and R ₂ is

[0019]

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[0020] In one or more kinds of divalent organic groups represented, it is R _3, of 12

[0021]

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And a polyimide film obtained by dehydrating and ring-closing a polyamic acid copolymer which is one or more tetravalent organic groups represented by the formula:

The heat-resistant adhesive layer has a water absorption of 1.
0% or less, and the dielectric constant is 3.0 or less.

The heat-resistant adhesive layer is represented by the following general formula (2):

[0025]

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(Where R ₅ is a divalent organic group, R
₆ represents a divalent organic group, and R ₇ represents a tetravalent organic group.
p and q are integers and satisfy 1 ≦ p and 0 ≦ q. ) Is a thermoplastic polyimide copolymer obtained by dehydration ring closure.

Further, when the heat-resistant adhesive layer is such that R ₅ in the general formula (2) is

[0028]

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[0029] is at least one divalent organic group selected from, R ₆ is, of 15

[0030]

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[0031] In one or more kinds of the divalent organic group represented, R ₇ is of 16

[0032]

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This is a thermoplastic polyimide copolymer obtained by dehydrating and ring-closing a polyamic acid copolymer which is one or more tetravalent organic groups represented by the formula:

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the heat-resistant bonding sheet according to the present invention will be specifically described together with a method for producing the same.

As an example of the heat-resistant bonding sheet according to the present invention, a bonding sheet 10 having a three-layer structure in which adhesive layers are provided on both surfaces of a base film is shown in FIG.
As shown in the figure, on both sides of the heat-resistant base film 12,
Heat resistant adhesive layers 14 and 16 are provided and formed.

The heat-resistant base film is preferably a polyimide film having a higher glass transition temperature than the adhesive layer, more preferably the polyimide film has a coefficient of hygroscopic expansion of 15 ppm or less. The coefficient of thermal expansion of the film is 4 or more 2
It is preferably at most 5 ppm. Further, the water absorption is preferably 1.5% or less.

In the case where the water absorption is 1.5% or less, in the case of manufacturing a semiconductor device, when a chip is packaged, generation of water vapor is small and reflow crack does not occur. When the coefficient of hygroscopic expansion is 15 ppm or less, the dimensional change due to water absorption is small, and the reliability in packaging is improved. Further, the coefficient of thermal expansion is 4 to
The reason for setting it to 25 ppm is that the coefficient of thermal expansion of the chip is 4 ppm.
And the coefficient of thermal expansion of the metal to be connected is about 20 ppm.

Specifically, as the base film 12, a compound represented by the general formula (1)

[0040]

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(Wherein, R ₁ is a divalent organic group, R ₂ is a divalent organic group, R ₃ is a tetravalent organic group. L and m are integers, and 1 ≦ l, Satisfying 0 ≦ m) is preferably a polyimide copolymer obtained by dehydration and ring closure.

The heat-resistant adhesive layers 14 and 16 are both made of a heat-resistant adhesive, and are not particularly limited to different types of adhesives or the same type of adhesive. However, each of the adhesive layers is particularly preferably a thermoplastic polyimide, and more preferably has a water absorption of 1.0% or less and a dielectric constant of 3.0 or less.

Specifically, each of the heat-resistant adhesive layers 14 and 16 has the general formula (2):

[0044]

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(Where R ₅ is a divalent organic group, R
₆ represents a divalent organic group, and R ₇ represents a tetravalent organic group.
p and q are integers and satisfy 1 ≦ p and 0 ≦ q. )).

First, a polyimide film made of a polyimide copolymer, which will be a base film of the heat-resistant bonding sheet according to the present invention, will be described.

This polyimide film is obtained by dehydrating and ring-closing a polyamic acid copolymer as a precursor. The polyamic acid copolymer solution is obtained by using an acid anhydride and a diamine component in substantially equimolar amounts and polymerizing in an organic polar solvent. First, a method for producing a polyamic acid copolymer solution will be described.

First, in an atmosphere of an inert gas such as argon or nitrogen, the general formula (3) H ₂ N—R ₂ —NH ₂ (3) (wherein R ₂ represents a divalent organic group) One or two types of diamines are dissolved in an organic solvent or dispersed in a slurry. This solution was added to the general formula (4)

[0049]

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(Wherein R ₁ represents a divalent organic group) and at least one aromatic diester dianhydride represented by the general formula (5):

[0051]

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Wherein a mixture of at least one tetracarboxylic dianhydride represented by the formula (wherein R ₃ represents a tetravalent organic group) is added in a solid state or in an organic solvent solution,
By reacting, a solution of the polyamide copolymer is obtained. The reaction temperature at this time is −20 to 100 ° C., particularly 6 ° C.
0 ° C. or lower is preferred. The reaction time is 30 minutes to 12 hours.

In this reaction, conversely, a diamine may be added to a solution of the mixture of the acid dianhydride components in the form of a solution or slurry of a solid or organic solvent of diamine. In addition, they may be mixed and reacted at the same time, and the mixing order of the acid anhydride component and the diamine component is not limited.

The polyamic acid produced as described above is preferably dissolved in the organic polar solvent in an amount of 5 to 40% by weight, preferably 10 to 30% by weight, from the viewpoint of handling.

In such a reaction, the ratio of the acid anhydride component is determined by the ratio between the aromatic diester dianhydride represented by the general formula (4) and the tetracarboxylic dianhydride represented by the general formula (5). It is preferred to use such that the molar ratio is in the range of 10/90 to 100/0.

The diamine represented by the general formula (3) is preferably used in an equimolar amount to the total amount of the acid anhydride component.

More specifically, the diamine component of the polyimide film used as the base film of the heat-resistant bonding sheet according to the present invention is represented by the following general formula (3): H ₂ NR ₂ —NH ₂ (3) ₂ is chemical formula 21

[0058]

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And a divalent organic group represented by the following formula:

As the acid anhydride used in the method for producing the polyamic acid copolymer, essentially various acid anhydrides can be used. More specifically, from the balance of various properties, general acid anhydrides can be used. Formula (4) 22

[0061]

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Wherein R ₁ is

[0063]

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And an aromatic diester dianhydride selected from the group consisting of a divalent organic group represented by the general formula (5):
Chemistry 24

[0065]

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(Wherein R ₃ is

[0067]

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A tetravalent organic group represented by It is preferred to use a tetracarboxylic dianhydride selected from

The monomer of the acid component used in the present invention may be prepared by reacting trimellitic anhydride dianhydride chloride with phenols in the presence of pyridine in a solvent such as benzene or toluene, or in a solvent having a high boiling point. It can be obtained by a method such as a transesterification reaction between trimellitic anhydride and diacetates.

The organic solvent used in the reaction for producing the aromatic polyamic acid copolymer solution includes, for example, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, N, N-
Examples thereof include formamide solvents such as diethylformamide, and acetamido solvents such as N, N-dimethylacetamide and N, N-diethylacetamide. These can be used alone or as a mixture of two or three or more solvents. Further, it can be used as a mixed solvent with a non-solvent of a polyamic acid copolymer such as acetone, methanol, ethanol, isopropanol, benzenemethyl cellosolve, etc., together with these polar solvents.

By such a reaction, a polyamic acid copolymer solution which is a precursor of the polyimide copolymer suitably used as the heat-resistant base film in the present invention is obtained.

The general formula (1) obtained as described above
The numbers l and m of the block units in the polyamic acid copolymer represented by are each an integer and satisfy 1 ≦ l and 0 ≦ m.

The molecular weight of the polyamic acid copolymer to be produced preferably has a number average molecular weight of 10,000 to 1,000,000 in order to maintain the strength of the polyimide film. If the average molecular weight is less than 10,000, the resulting film becomes brittle, while if it exceeds 1,000,000, the viscosity of the polyamic acid varnish becomes too high and handling becomes unfavorable.

The polyamic acid copolymer solution thus obtained is formed into a film,
Alternatively, a film made of a polyimide copolymer used as a heat-resistant base film in the present invention is obtained by chemically dehydrating and ring-closing (imidizing).

For example, in the method of chemically dehydrating and cyclizing, a dehydrating agent having a stoichiometric amount or more and a catalytic amount of a tertiary amine are added to a solution of the polyamic acid copolymer, and a support plate, PET Etc., into a film form by casting or coating on a support such as an organic film, drum or endless belt,
A film having self-supporting properties is obtained by evaporating the organic solvent. The evaporation of the organic solvent is preferably performed at a temperature of 150 ° C. or less for about 5 to 90 minutes. Then, it is peeled off from the support and the ends are fixed. Then about 100 ° C
Imidization by gradually heating to ~ 500 ° C,
After cooling, it is removed from this to obtain a polyimide film.

The dehydrating agent mentioned here includes, for example, fatty acid dianhydride such as acetic anhydride, aromatic acid dianhydride and the like. Examples of the catalyst include aliphatic amines such as triethylamine, aromatic amines such as dimethylaniline, and heterocyclic tertiary amines such as pyridine, picoline and isoquinoline.

In the thermal dehydration ring closure method, first, a solution of the above-mentioned polyamic acid copolymer is placed on a support plate or PET.
The film is cast or coated on a support such as an organic film such as a drum or an endless belt to form a film, and treated in the same manner as in the case of chemical dehydration.

When the method of thermally imidizing is compared with the method of chemically imidizing, the polyimide film obtained by the chemical method has excellent elongation, and has high mechanical strength. In addition, there are advantages in that mechanical properties such as a decrease in thermal expansion coefficient are improved, and that imidization can be performed in a shorter time by a chemical method. In addition, it is also possible to use both the method of thermally imidizing and the method of chemically imidizing together.

Further, imidization is performed while heating and drying to obtain a polyimide film comprising a polyimide copolymer. The heating temperature is preferably in the range of 110 ° C to 550 ° C. The heating temperature at the time of heating is not particularly limited, but it is preferable that heating is performed gradually so that the maximum temperature becomes the above-mentioned temperature. The heating time varies depending on the film thickness and the maximum temperature, but is generally preferably in the range of 10 seconds to 10 minutes after the maximum temperature is reached. When heating and drying / imidizing the self-supporting film, the self-supporting film is peeled off from the support, and the end portion is fixed in this state, so that a copolymer having a small linear expansion coefficient can be formed. can get.

By thermally / chemically imidizing the aromatic polyamic acid copolymer in this manner, an aromatic polyimide copolymer film to be a base film of the heat-resistant bonding sheet according to the present invention is obtained. Can be

It is well known that polyimide is equivalent to polyisoimide, but it is also possible to improve the solvent solubility by selecting an isoimide structure. In order to obtain a polyisoimide copolymer, the above-mentioned chemical ring closing agent is replaced with dicyclohexylcarbondiimide (DC
After replacing with a diimide such as C) and / or a carboxylic dianhydride such as trifluoroacetic acid, the same reaction as in the production of this polyimide may be performed.

The polyimide film to be a base film of the obtained heat-resistant bonding sheet according to the present invention is:
It has excellent adhesion, low water absorption and low dielectric properties.

Accordingly, the film comprising the polyimide copolymer thus obtained can be preferably used as the base film of the bonding sheet according to the present invention in the present invention. The bonding sheet can be obtained.

The base film layer of the heat-resistant bonding sheet according to the present invention has a glass transition temperature of 0.1 G
It has a storage elastic modulus of Pa or more. Therefore, in the case of processing near the glass transition temperature, in the case of a base film having a storage elastic modulus at the glass transition temperature of 0.1 GPa or less, the base film itself flows during processing by pressing,
Although there is a problem that it can not serve as a base,
By having a storage elastic modulus of 0.1 GPa or more, there is an effect that deformation due to pressure during processing is almost eliminated.

The film made of the polyimide copolymer obtained as described above can be preferably used as the heat-resistant base film 12 according to the present invention.

Next, a preferred example of the heat-resistant adhesive layers 14 and 16 used in the present invention will be specifically described together with a production method thereof. In particular,
Formula (2) 26

[0087]

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(Where R ₅ is a divalent organic group, R
₆ represents a divalent organic group, and R ₇ represents a tetravalent organic group.
p and q are integers and satisfy 1 ≦ p and 0 ≦ q. ) Is preferably a polyimide copolymer obtained by dehydration ring closure.

More specifically, general formula (6)

[0090]

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(Wherein R ₅ represents a divalent organic group) and diester acid dianhydride represented by the general formula (7):
8

[0092]

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(Wherein R ₇ represents a tetravalent organic group) and an acid component composed of a tetracarboxylic dianhydride represented by the general formula (8): H ₂ N—R ₆ —NH ₂ (8) It is preferable to comprise an aromatic polyimide copolymer obtained by combining one or more diamine compounds represented by the formula (wherein, R ₆ represents a divalent organic group).

Further, in the general formula (6), R ₅ is

[0095]

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Wherein R ₇ is a divalent organic group represented by the general formula (7)

[0097]

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It is preferably a tetravalent organic group represented by the formula:

The aromatic polyimide copolymer serving as a heat-resistant adhesive layer of the heat-resistant bonding sheet according to the present invention is prepared by using an aromatic polyamic acid copolymer solution as a precursor thereof and a polyamic acid copolymer as a precursor thereof. Since the polymer is obtained by dehydration ring closure and exhibits a low water absorption of 1.0% or less,
In the case of manufacturing such a semiconductor element, no reflow crack occurs when the chip is packaged. In addition, since the dielectric constant is 3.0 or less, the electrical reliability is also satisfied. The method for producing the polyamic acid copolymer solution will be described below.

In an atmosphere of an inert gas such as argon or nitrogen, a compound represented by the general formula (8) H ₂ N—R ₆ —NH ₂ (8) (wherein R ₆ represents a divalent organic group). A mole of the diamine compound to be dissolved or diffused in a gas-permeable solvent, and in this solvent, the general formula (6) is set so that a = b + c substantially in the range of b: c = 1: 99 to 100: 0. 3)
1

[0101]

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(Wherein R ₅ represents a divalent organic group), and b mole of an aromatic diester dianhydride represented by the following formula:

[0103]

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(Wherein R ₇ represents a tetravalent organic group) represented by c moles of aromatic tetracarboxylic dianhydride:
It is obtained by adding and reacting in the form of a solution or slurry with a solid or organic solvent. The reaction temperature at this time is -20 ° C to 50 ° C, more preferably -5 ° C.
４０40 ° C. and the reaction time is 30 minutes to 12 hours.

In such a reaction, conversely to the above, a diamine may be added in the form of a solution or slurry of a solid or organic solvent of a diamine to a solution of a mixture of acid dianhydride components.

By specifying these diamine components and acid dianhydride components, it is possible to obtain an appropriate glass transition temperature for the adhesive layer.

Examples of the organic solvent used for the reaction for producing the polyamic acid copolymer solution include sulfoxide solvents such as diamityl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, and N, N-diethyl. Formamide solvents such as formamide, N, N-dimethylacetamide, acetamide solvents such as N, N-diethylacetamide, N-methyl-2-pyrrolidone, pyrrolidone solvents such as N-vinyl-2-pyrrolidone, phenol, o −,
Examples thereof include phenol solvents such as m- or p-cresol, xylenol, halogenated phenol, and catechol, and hexamethylphosphoramide, γ-butyrolactone, and the like. These can be used with only one kind of solvent or a mixed solvent of two or more kinds. Further, it is also possible to use a mixture of aromatic hydrocarbons such as xylene and toluene.

A mixed solvent composed of these polar solvents and a non-solvent of polyamic acid can also be used. As the non-solvent of the polyamic acid, a mixed solvent with a non-solvent of a polyamic acid copolymer such as acetone, methanol, ethanol, isopropanol, benzene, and methyl cellosolve can be used. Further, it is also possible to partially use aromatic hydrocarbons such as xylene and toluene.

As described above, a polyamic acid copolymer solution which is a precursor of the thermoplastic polyimide copolymer suitably used as the heat-resistant adhesive layer is obtained.

It is desirable from the viewpoint of handling that the polyamic acid is dissolved in the above organic solvent in an amount of 5 to 40% by weight, preferably 10 to 30% by weight.

Then, the polyamic acid copolymer solution thus obtained is formed into a film, which is thermally and / or thermally.
Alternatively, a film made of a thermoplastic polyimide copolymer used as a heat-resistant adhesive layer in the present invention is obtained by chemically dehydrating a ring closure (imidization).

To explain by way of example, in the method of thermal dehydration and ring closure, a solution of the above polyamic acid polymer is placed on a support plate,
An organic film such as PET, cast or coated on a support such as a drum or an endless belt to form a film,
Dry to obtain a self-supporting film. This drying is preferably performed at a temperature of 150 ° C. or less for about 5 to 90 minutes. Next, this is further heated and dried to be imidized while being dried, to obtain a polyimide film made of the aromatic polyimide polymer used in the present invention. Heating temperature is 15
Temperatures in the range 0-350 ° C are preferred. When heating the film having self-supporting properties, it is preferable to peel off the film from the support, fix the end portion in this state, and heat the polymer, since a polymer having a small coefficient of thermal expansion can be obtained.

In the method of chemically dehydrating and cyclizing a ring, a dehydrating agent having a stoichiometric amount or more and a catalytic amount of a tertiary amine are added to the polyamic acid polymer solution, and a method similar to the method of thermally dehydrating is used. , A desired polyimide film can be obtained in a shorter time than in the case of thermal dehydration.

Thus, by thermally and / or chemically imidizing the aromatic polyamic acid copolymer,
An aromatic polyimide copolymer film to be used as an adhesive layer of the polyimide bonding sheet of the present invention is obtained.

The thermoplastic polyimide film obtained by such a method and serving as the adhesive layer of the heat-resistant bonding sheet according to the present invention has both excellent low water absorption and low dielectric properties. That is, such a thermoplastic polyimide film generates little gas when heated, and moreover,
Since the water absorption when immersed in pure water at 20 ° C. for 24 hours has a low value of 1.0% or less, no reflow crack occurs when a chip is packaged in manufacturing such a semiconductor element. . The dielectric constant is also 1MH
Since it exhibits a low dielectric property of not more than 3.0 at z (normal state), it also satisfies electrical reliability, and a heat-resistant bonding sheet of the present invention can provide a semiconductor device having excellent reliability.

The thicknesses of the base film layer and the adhesive layer used herein are not particularly limited, but may be, for example, 12.5 μm (１ ／ mil), 25 μm,
m (1 mil), 50 μm (2 mil), 75 μm (3
mil), 125 μm (5 mil), 175 μm (7 m
il) and the like.

Further, the base film 12 and the adhesive layer 1
In order to improve the adhesive strength between the base film 4 and 16, both surfaces of the base film may be subjected to a surface treatment such as a flame treatment, a corona treatment, an O ₂ plasma treatment, a sputtering treatment, a silane coupling treatment and a metal Na treatment.

The method for producing the heat-resistant bonding sheet according to the present invention is as follows. The same or different films made of the thermoplastic polyimide copolymer obtained above are used on both sides of the base film 12 and heat-resistant adhesive sheets are formed. Agent 1
The thermoplastic polyimide films 4 and 16 may be laminated and thermocompression bonded. Also, the adhesive layer
The thermocompression bonding may be performed only on one side of the heat resistant base film.

The heat-resistant bonding sheet according to the present invention has a difference in glass transition temperature of 10 to 100 ° C. when different types of adhesive layers having different glass transition temperatures are thermocompression bonded to both surfaces of the heat-resistant base film. And a heat-resistant adhesive layer made of a thermoplastic polyimide copolymer having a difference in thermal expansion coefficient of 50 ppm or less. As described above, when the same type of thermoplastic polyimide copolymer having a different composition is used, it is possible to make the linear expansion coefficients of the adhesive layers on both surfaces hardly different, and as a result, the obtained heat resistance When processing using a bonding sheet, handling becomes easy.

Further, the glass transition temperature of the adhesive layers on both sides, that is, the processing temperature is about 5 ° C. or more, especially 10 to 100 ° C.
Since the temperature differs in the range of ° C., each surface can be sequentially processed at different temperatures. At this time, if the temperature difference of the glass transition temperature (Tg) is about 5 ° C. or more, particularly 10 ° C. or more, the temperature condition and the temperature control become easy with the processing. If the temperature difference is too large, the adhesive layer on the low glass transition temperature side is deteriorated by heating when processing into a heat-resistant bonding sheet, so that the temperature is preferably within 100 ° C.

Specifically, for example, when the heat-resistant bonding sheet of the present invention is used as a die-bonding film for bonding a die pad of a lead frame and a semiconductor chip at the time of manufacturing a semiconductor element, the heat-resistant adhesive layer 1
The two types of thermoplastic polyimide films used as 4, 16 have a difference in glass transition temperature of 10 to 1
In the range of 00 ° C., and the difference in thermal expansion coefficient is 50 ppm or less, particularly preferably 20 ppm or less, and further preferably 10 ppm or less.
As long as it is the following, any composition may be used in combination, but preferably, a film obtained using TMEG as an aromatic diester dianhydride and a film obtained using ESDA are used in combination. Good. Specifically, the film obtained using TMEG has a glass transition temperature of 10 to 100 ° C. more than the film obtained using ESDA.
Low, the difference in the coefficient of thermal expansion is less than 10 ppm,
It is preferable to use the film obtained by using MEG as the adhesive layer 14 having a lower glass transition temperature and the film obtained by using ESDA as the adhesive layer 16 having a higher glass transition temperature.

The temperature conditions for thermocompression bonding when producing the bonding sheet according to the present invention are higher than those near the glass transition temperature of the adhesive layer, and when a different kind of film is used, the adhesive layer has Set higher than the higher temperature of the glass transition temperature, basically lower than the glass transition temperature of the base film, and 10 to 100 kgf / cm
^{2. The} condition of thermocompression bonding for about 10 minutes is preferable, but not limited.

After the polyamic acid solution, which is a precursor of the thermoplastic polyimide, is cast on the polyimide film serving as the base film 12 and imidized, the polyamic acid solution is cast on the opposite surface of the base film and imidized. To obtain a bonding sheet. Alternatively, a polyamic acid solution may be simultaneously cast on both surfaces of a polyimide film serving as a base film and imidized. Also,
The imidized polyimide adhesive may be dissolved in a solvent such as DMF, NMP, or the like, and may be directly applied and dried on both surfaces of the polyimide film serving as the base film.

Further, as still another method for producing the heat-resistant bonding sheet according to the present invention, the above polyamic acid copolymer solution is imidized in a film, lump, powder or other form without limitation, and the resulting solution is subjected to DMF. , NMP, or the like to form a polyimide solution, and then apply the polyimide solution to a base film to dry the solvent. Such a thermoplastic polyimide copolymer,
This is because it shows solubility in a solvent and can be a polyimide solution.

Further, the thermoplastic polyimide copolymer exhibits a melt fluidity by heating. For example, the thermoplastic polyimide copolymer formed into a granular material is heated and melted, and is directly applied on a base film. Thereby, the heat-resistant bonding sheet of the present invention can be obtained.

The bonding sheets produced by these methods are all made of polyimide and can be easily drilled because they can be alkali-etched.
For example, a printed circuit board can be obtained relatively easily by laminating copper foil on both sides of the polyimide bonding sheet according to the present invention, thermocompression bonding, etching the copper foil, and further performing a hole drilling process on the polyimide by alkali etching. Can be

When a different kind of adhesive layer is provided, specifically, for example, when a semiconductor element is manufactured, the heat-resistant bonding sheet of the present invention is used as a die bond film for bonding a die pad of a lead frame and a semiconductor chip. In this case, first, the adhesive layer 14 having a lower glass transition temperature is heat-pressed to a die pad of a lead frame at a temperature higher than that near the glass transition temperature, and temporarily bonded. At this time, since the adhesive layer 16 having a higher glass transition temperature has a difference in processing temperature, the bonding sheet does not adhere to a press or the like. After that, the semiconductor chip is placed on the adhesive layer 16 and heated and pressed at a temperature higher than the glass transition temperature of the adhesive layer 16,
The die pad of the lead frame can be bonded to the semiconductor chip.

Conversely, a release paper or the like is provided on the adhesive layer 14 having the lower glass transition temperature, and the adhesive layer 16 having the higher glass transition temperature is first bonded to the semiconductor chip. Then, the release paper may be peeled off, and the adhesive layer 14 having the lower glass transition temperature may be bonded to the die pad. Accordingly, a high temperature is not applied to the lead frame due to heating at the time of bonding, and the deterioration of the lead frame due to the processing temperature can be prevented.

Alternatively, if the semiconductor chip may be deteriorated at a high temperature, first, the adhesive layer 16 having the higher glass transition temperature is bonded to the die pad, and then the adhesive layer 16 having the lower glass transition temperature is bonded. The adhesive layer 14 and the semiconductor chip may be bonded together.

In the heat-resistant bonding sheet according to the present invention, such a semiconductor element is manufactured because the thermoplastic polyimide film as the adhesive layer hardly generates gas at the time of heating and has a low water absorption. In this case, no reflow crack occurs when the chip is packaged. Further, the semiconductor device has a low dielectric constant and thus satisfies electrical reliability. According to the present invention, a highly reliable semiconductor device can be provided.

Further, the heat-resistant bonding sheet according to the present invention can be made of a multilayer FPC, a rigid-flex substrate material,
It is suitable for new high-density packaging materials such as OL and LOC packages and MCM, and other uses are not particularly limited.

Although the embodiments of the heat-resistant bonding sheet and the method of manufacturing the same according to the present invention have been described above, the present invention is not limited to only these examples.
The present invention can be practiced in various modified, changed, and modified aspects based on the knowledge of those skilled in the art without departing from the spirit thereof.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the examples, ODA is 4,4 ^'- diaminodiphenyl ether, BAPP is ^2,2' - bis (4- (4-aminophenoxy) phenyl) propane,
BAPB is 4,4 ^'- bis (4-aminophenoxy) biphenyl, p-PDA is paraphenylenediamine, PM
DA is pyromellitic anhydride, TMEG is, 3,3 ', ^4,4' -
Ethylene glycol benzoate tetracarboxylic dianhydride, ODPA is oxydiphthalic dianhydride, BTDA
Is benzophenonetetracarboxylic dianhydride, DMF
Represents dimethylformamide.

Further, the coefficient of thermal expansion and the glass transition temperature were measured with a Rigaku TMA 8140 under a nitrogen stream. The coefficient of linear expansion ranges from 100 ° C to 20 ° C.
The value was up to 0 ° C. For water absorption, the film
The weight of the product dried at 50 ° C. for 30 minutes is defined as W ₁ , 2
After immersion in distilled water for 4 hours and wiping off water droplets on the surface, the weight is defined as W ₂ and calculated by the following equation.

Water absorption (%) = (W ₁ −W ₂ ) ÷ W ₁ × 100 The coefficient of hygroscopic expansion is 24 in an environmental tester at 50 ° C. and 30% Rh.
The film is left for a period of time, the film dimensions are measured (L ₁ ). Then, the film is left standing for 24 hours in an environmental tester at 50 ° C. and 80% Rh, and the film dimensions are measured (L ₂ ) and calculated by the following equation. Coefficient of hygroscopic expansion (ppm) = (L ₁ −L ₂ ) {L ₁ } (8
0-30) × 10 ^{6 The} elastic modulus is according to ASTM D882.

First, a production example of an acid component used in the heat-resistant bonding sheet according to the present invention will be described.

(Production Example 1) Synthesis of acid component: p-phenylenebis (trimellitic acid monoester anhydride) 510 g of trimellitic anhydride chloride was placed in a 3000 ml three-necked flask equipped with a dropping funnel and a reflux condenser. 2.
4 mol) and 1000 ml of toluene and stirred at about 80 ° C. 132 g (1.2 mol) of hydroquinone was dissolved in 1200 ml of toluene and 240 ml of pyridine.
It is dripped from a dropping funnel into a one-necked flask. After the addition, the mixture was stirred for about 2 hours. After cooling, the precipitate was separated by filtration to obtain a white solid. This white solid was washed with 3 liters of water and dried,
Stir at reflux with acetic anhydride for about 2 hours and filter off. The white solid obtained by filtration was recrystallized from DMF to obtain 380 g of a white solid.

[0138] (Production Example 2) acid component: 4,4 ^'- instead of synthetic hydroquinone biphenylene bis (trimellitic acid monoester acid anhydride), ^4,4' - dihydroxybiphenyl 223.2 g (1.2 mol ) Was obtained in the same manner as in Production Example 1 except that) was used to obtain 400 g of a white solid.

(Production Example 3) Acid component: Synthesis of 1,4-naphthalenebis (trimellitic acid monoester anhydride) Instead of hydroquinone, 192.0 g (1.2 mol) of 1,4-dihydroxynaphthalene was used. Except for using, 380 g of white solid was obtained in the same manner as in Production Example 1.

(Production Example 4) Acid component: 2,2-bis (4-hydroxyphenyl) propanedibenzoate-3,3 ', 4,4'-tetracarboxylic dianhydride (hereinafter referred to as ESDA) Instead of hydroquinone In addition, bisphenol A273.9
450 g of a white solid was obtained in the same manner as in Production Example 1 except that g (1.2 mol) was used.

Next, Examples 1 to 5 show production examples of the polyimide film for the heat-resistant base film used in the heat-resistant bonding sheet according to the present invention.

[0142]

[Example 1] NMP and p-PD were placed in a separable flask.
2 equivalents of A and 1 equivalent of ODA were stirred well at room temperature until the diamine compound was completely dissolved. Next, 2.85 equivalents of p-phenylenebis (trimellitic acid monoester anhydride) shown in Production Example 1 was gradually added as a powder, and then stirred for 40 minutes. Then, 0.15 equivalent of p-phenylenebis (trimellitic acid monoester anhydride) was added to NMP.
, And the mixture was gradually added, and then cooled and stirred for 1 hour to obtain a polyamic acid NMP solution. The amount of NMP used was such that the concentration of charged monomers of diamines and aromatic tetracarboxylic dianhydrides was 18% by weight.

Next, the polyamic acid solution was mixed with acetic anhydride and β-picoline, and cast and coated on a glass plate.
After drying for about 5 minutes, the polyamic acid coating film was peeled off from the glass plate, and the coating film was fixed to a support frame. Thereafter, the coating was performed at about 100 ° C. for about 5 minutes, at about 200 ° C. for about 5 minutes, and at about 300 ° C. for about 5 minutes. After heating for about 5 minutes at about 400 ° C., dehydration and ring-closure drying, a polyimide film of about 50 μm was obtained.

Table 1 shows the physical properties of the obtained polyimide film.
It was shown to.

[0145]

[Table 1]

[0146]

Example 2 A polyamic acid was obtained in the same manner as in Example 1 except that 1 equivalent of BAPP was used instead of ODA, and a polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

[0147]

EXAMPLE 3 Instead of p-phenylenebis (trimellitic acid monoester anhydride), the 4,4
Polyamide acid was obtained in the same manner as in Example 1 except that ^' -biphenylenebis (trimellitic acid monoester acid anhydride) was used, and a polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

[0148]

Example 4 Instead of p-phenylenebis (trimellitic acid monoester acid anhydride), 1,4 shown in Production Example 3 was used.
A polyamic acid was obtained in the same manner as in Example 1 except that naphthalenebis (trimellitic acid monoester acid anhydride) was used, and a polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

[0149]

Example 5 NMP and p-PDA in a separable flask
And 2 equivalents of ODA, and well stirred at room temperature until the diamine compound was completely dissolved. Next, 2 equivalents of p-phenylenebis (trimellitic acid monoester anhydride) shown in Production Example 1 were gradually added in powder form, and the mixture was stirred for 40 minutes. Then, 0.85 equivalent of ODPA was gradually added as a powder, and the mixture was stirred for 40 minutes. 0.15 equivalents of ODPA was dissolved in NMP, added gradually, and then cooled and stirred for 1 hour to obtain a polyamic acid NMP solution. A polyimide film of about 50 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

Hereinafter, Comparative Examples 1 and 2 show comparative examples of the polyimide film for a heat-resistant base film.

[0151]

Comparative Example 1 In the same manner as in Example 1, a 50 μm polyimide film was obtained using PMDA and ODA in equimolar amounts. Table 1 shows the physical properties of the obtained polyimide film.
It was shown to.

[0152]

Comparative Example 2 DMF was placed in a 2-liter separable flask.
And 1 equivalent of ODA, mixed well at room temperature until the diamine compound was completely dissolved, and then stirred while cooling with ice. Next, 2 equivalents of PMDA were added and the mixture was cooled and stirred for 40 minutes. Then, 1 equivalent of p-PDA was dissolved in DMF, gradually added, and then cooled and stirred for 1 hour.
An MF solution was obtained. Baking in the same manner as in Example 1, 50
A μm polyimide film was obtained. Table 1 shows the physical properties of the obtained polyimide film.

Next, Examples 6 and 7 show production examples of a polyimide film used for the heat-resistant adhesive layer of the heat-resistant bonding sheet according to the present invention.

[0154]

Example 6 Five equivalents of DMF and BAPP were placed in a separable flask and stirred well at room temperature until the diamine compound was completely dissolved. Next, 4 equivalents of TMEG were gradually added as a powder, followed by stirring for 40 minutes. BTDA (0.85 equivalents) was gradually added as a powder, followed by stirring for 40 minutes. BTDA
Was dissolved in DMP at 0.15 equivalents, gradually added, and then cooled and stirred for 1 hour to obtain a polyamic acid DMP solution.
A polyimide film of about 25 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

[0155]

[Embodiment 7] Instead of TMEG, E shown in Production Example 4 was used.
A polyamic acid was obtained in the same manner as in Example 7 except that SDA was used, and a polyimide film of about 25 μm was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polyimide film.

[0156]

Examples 8 to 14 The adhesive films obtained in Examples 7 to 8 were arranged on both sides of the base film obtained in Examples 1 to 6 in combinations shown in Table 2, and release films were arranged on both sides thereof. Then, it was heat-pressed at 250 ° C. and 20 kgf / cm ² for 10 minutes to obtain a heat-resistant bonding sheet according to the present invention. Table 2 shows the physical properties of this bonding sheet.

[0157]

[Table 2]

Further, copper foil (thickness: 35 μm) was placed on both sides of the obtained bonding sheet.
Heat press was performed for 1 hour under the condition of kgf / cm ² to obtain a double-sided copper-clad laminate.

The obtained double-sided copper-clad laminate was subjected to JIS
The peel strength was measured according to K6481. Table 2 shows the results.

[0160]

Comparative Examples 3 and 4 The adhesive films obtained in Examples 6 and 7 were prepared in the same manner as in Examples 9 and 14, except that the films obtained in Comparative Examples 1 and 2 were used as base films. And the release films were provided on both sides thereof to obtain a bonding sheet and a double-sided copper-clad laminate. The physical properties of the obtained bonding sheet and the peel strength of the double-sided copper-clad laminate were measured in accordance with JIS K6481. Table 2 shows the results.

[0161]

As described above, the heat-resistant bonding sheet according to the present invention has a polyimide film as a base film and adhesive layers provided on both sides of the base film. And the base film is excellent in heat resistance, excellent in adhesiveness, retains a high elastic modulus, is particularly made of an aromatic polyimide copolymer having a low water absorption and a low dielectric constant, and is provided on both sides of the base film. The obtained adhesive layer is made of a polyimide copolymer which is excellent in heat resistance and adhesive, and particularly exhibits low water absorption and low dielectric properties.

Further, since the heat-resistant bonding sheet according to the present invention hardly generates gas when heated and exhibits a low water absorption, it is necessary to use the heat-resistant bonding sheet of the present invention when packaging a semiconductor element, for example. Accordingly, by using the heat-resistant bonding sheet according to the present invention at the time of packaging, it is possible to obtain a package having excellent reliability without generating a package crack. In addition, since it has a low dielectric constant, it has excellent electrical reliability.

Therefore, the heat-resistant bonding sheet according to the present invention is suitable for new high-density mounting applications such as multilayer FPC, rigid-flex substrate materials, COL and LOC packages, and MCM, and other applications are not particularly limited.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional explanatory view showing a heat-resistant bonding sheet according to the present invention.

[Explanation of symbols]

 10; heat-resistant bonding sheet 12; heat-resistant base film 14, 16; adhesive layer

Claims (8)

[Claims] 1. A heat-resistant adhesive layer is provided on one or both sides of a heat-resistant base film, and has a moisture expansion coefficient of 15 ppm.
A heat-resistant bonding sheet comprising the following polyimide film as a base film. 2. The heat-resistant bonding sheet according to claim 1, wherein the heat-resistant base film is made of a polyimide film having a coefficient of thermal expansion of 4 to 25 ppm. 3. The heat-resistant bonding sheet according to claim 1, wherein the heat-resistant base film is made of a polyimide film having a water absorption of 1.5% or less. 4. The heat-resistant base film according to the general formula (1) (Wherein, R ₁ is a divalent organic group, R ₂ is a divalent organic group, R
₃ represents a tetravalent organic group. Also, l and m represent integers,
1 ≦ l and 0 ≦ m are satisfied. The heat-resistant bonding sheet according to any one of claims 1 to 3, comprising a polyimide film obtained by dehydrating and ring-closing the polyamic acid copolymer represented by the formula (1). 5. The heat-resistant base film according to claim 1, wherein R ₁ in the general formula (1) is At least one divalent organic group selected from
₄ is CH ₃ —, Cl—, Br—, F—, CH ₃ O—, and R ₂ is One or more divalent organic groups represented by the formula: wherein R ₃ is 5. A heat-resistant polyimide according to claim 1, comprising a polyimide film obtained by dehydrating and ring-closing a polyamic acid copolymer which is one or more tetravalent organic groups represented by the formula: Bonding sheet. 6. The heat-resistant adhesive layer has a water absorption of 1.0%.
The heat-resistant bonding sheet according to any one of claims 1 to 5, wherein the dielectric constant is 3.0 or less. 7. The heat-resistant adhesive layer according to the general formula (2) (However, R ₅ represents a divalent organic group, R ₆ represents a divalent organic group, and R ₇ represents a tetravalent organic group. P and q represent integers, and 1 ≦ p, 0 ≦ q The heat-resistant bonding sheet according to any one of claims 1 to 6, comprising a thermoplastic polyimide copolymer obtained by dehydration ring closure. 8. The heat-resistant adhesive layer, wherein R ₅ in the general formula (2) is represented by the following formula: One or more divalent organic groups selected from
₆ becomes 7 Wherein R ₇ is at least one divalent organic group represented by the formula: 8. A thermoplastic polyimide copolymer obtained by dehydrating and ring-closing a polyamic acid copolymer which is one or more tetravalent organic groups represented by the formula: The heat-resistant bonding sheet described in 1.