JPH05331444A - Film adhesive capable of heat bonding at low temperature - Google Patents

Abstract

PURPOSE:To obtain a film adhesive, composed of a specific polyimide resin, bondable at low temperatures in a short time, excellent in heat resistance, bonding operation efficiency, dimensional accuracy and reliability and useful as a semiconductor packaging materials, etc. CONSTITUTION:The film adhesive is composed of a polyimide resin, obtained by reacting (A) an acid component composed of (a) mol ethylene glycol bistrimellitic dianhydride and (b) mol other tetracarboxylic dianhydrides with (B) an amine component composed of (c) mol alpha,omega-bis(3-aminopropyl) polydimethylsiloxane, (d) mol 1,3-bis-(3-aminophenoxy)benzene and (e) mol other diamines at ratios of >=0.6{(a)/[(a)+(b)]}, 0.05<={(c)/[(c)+(d)+(e)]}<=0.6, 0.6<={[(c)+(d)]/[(c)+(d)+(e)]} and 0.900<={[(a)+(b)]/[(c)+(d)+(e)]}<=1.06 and carrying out the imide cyclization and having <=350 deg.C glass transition temperature. Furthermore, this adhesive is applied to one or both surfaces of a heat- resistant film substrate to afford the film adhesive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film adhesive which has excellent heat resistance and is suitable for use in electronics, and particularly suitable as a semiconductor mounting material for a silicon substrate and a metal, and which can be bonded at a low temperature in a short time. ..

[0002]

2. Description of the Related Art In recent years, semiconductor chips have become larger due to higher functionality and larger capacity, while the size of elements has been required to maintain the same external shape as in the past due to the demand for miniaturization of electronic equipment. Several new mounting methods have been proposed for high density and high density mounting of semiconductor chips. This new mounting method has two structures, COL (chip on lead) for mounting a chip on a lead frame without a die pad and LOC (lead on chip) for mounting a lead on the chip. In the conventional method, the chip area is too large to secure the area of the inner lead, but
In these methods, the semiconductor chip and the lead frame are bonded by the double-sided adhesive tape, and the package can be housed in the same external shape as the conventional one, despite the increase in the chip area due to the large capacity. Furthermore, advantages such as rationalization of in-chip wiring and wire bonding and speeding up of signals by shortening wiring can be mentioned.

In a semiconductor device having a COL or LOC structure, a semiconductor chip and a lead frame are fixed by an adhesive. This adhesive is required to have excellent adhesive strength such that the interface does not peel off when absorbing moisture, and the interface does not peel off when subjected to thermal stress such as during reflow soldering or temperature cycle. In addition, it is not preferable that a large amount of volatile components are generated during heat-bonding because it contaminates the work environment and leads. Further, considering mass productivity, it is desired that the bonding be possible in the shortest possible time. Conventionally, paste-like adhesives and heat-resistant substrates coated with adhesives have been used for these applications. Epoxy resin-based, acrylic resin-based, and rubber-phenol resin-based thermosetting resins are used as adhesives, but there are many ionic impurities, heat curing requires high temperature and long time, and productivity is poor. It is hard to say that the above requirements are satisfied, such as a large amount of volatile components during curing and high hygroscopicity, and no satisfactory material is found.

On the other hand, some heat-resistant thermocompression-bondable film adhesives are known, and, for example, JP-A-1-
282283 discloses a polyamide-imide-based or polyamide-based hot-melt adhesive, and JP-A-58-157190 discloses a hot-melt adhesive.
A method for manufacturing a flexible printed circuit board using a polyimide adhesive, JP-A-62-235382, JP-A-62-235383 and JP-A-2-15663, describes a thermosetting polyimide film adhesive. Has been done. However, polyamide-based and polyamide-imide-based resins have a drawback that the water absorption rate becomes large due to the hydrophilicity of the amide group, and there is a limit in using them as adhesives for electronic applications requiring reliability. .. In addition, thermosetting polyimide film adhesives have a thermocompression bonding condition of 275 ° C and 50 kgf / cm.
² , Electronic components that are sensitive to heat, pressure, water, etc., such as needing to be cured for 30 minutes or a semi-cured state at high temperature for a long time, and condensation water being generated during curing In addition, it cannot be said to be sufficient as a film adhesive for applications requiring mass productivity. For these reasons, the development of highly reliable adhesives suitable for new mounting forms is required.

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention As a result of intensive studies to obtain a film adhesive having excellent heat resistance, which can be bonded at a low temperature in a short time, the present invention has revealed that a film adhesive using a polyimide resin having a specific structure is used. The inventors have found that the above problems can be solved and arrived at the present invention.

[0006]

According to the present invention, the acid component is ethylene glycol bistrimellitic acid dianhydride a mol and another tetracarboxylic acid dianhydride b mol, and the amine component is α,
ω-bis (3-aminopropyl) polydimethylsiloxane c
Mol, 1,3-bis (3-aminophenoxy) benzene d mol and other diamine e mol, a / (a + b) ≧
0.6, 0.05 ≤ c / (c + d + e) ≤ 0.6, 0.6 ≤ (c +
d) / (c + d + e), and 0.900 ≦ (a + b) / (c
+ D + e) A film adhesive made of a polyimide resin having a glass transition temperature of 350 ° C. or lower, which is obtained by reacting both components at a ratio of 1.06 and imide ring closure.

In the present invention, ethylene glycol bistrimellitic dianhydride (hereinafter abbreviated as EGTA) used to obtain a polyimide resin forming an adhesive is represented by the formula (1), α, ω-bis (3-aminopropyl). Polydimethylsiloxane (hereinafter abbreviated as APPS) is represented by the formula (2), 1,3-bis.
(3-Aminophenoxy) benzene (hereinafter abbreviated as APB) is represented by the formula (3).

[0008]

[Chemical 1]

[Chemical 2]

[Chemical 3]

Other tetracarboxylic dianhydrides that can be used in the present invention include, for example, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3', 4,4 '. -Benzophenone tetracarboxylic dianhydride (BTDA), 1,2,4,
5-benzenetetracarboxylic dianhydride, 2,2'-bis (4-
Examples thereof include tetracarboxylic dianhydrides such as (3,4-dicarboxyphenyl) phenyl) propane dianhydride, and further dicarboxylic acid anhydrides such as phthalic anhydride (PA) as a molecular weight modifier.

Other diamines that can be used in the present invention include, for example, 1,4-bis (3-aminophenoxy) benzene, 1,4
3-bis (4-aminophenoxy) benzene, 2,2-bis (4- (4-
Aminophenoxy) phenyl) propane (BAPP),
4,4'-diaminodiphenyl ether (4,4'-DDE), 3,
3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone (4,4'-DDS), 3,3'-diaminodiphenyl sulfone, 2,2-bis-4-aminophenyl Hexafluoropropane (BAPF), 2,2-bis-4-aminophenoxyphenylhexafluoropropane (BAPPF), bis-4- (4-
Aminophenoxy) phenyl sulfone (BAPS),
Bis-4- (3-aminophenoxy) phenyl sulfone (B
APSM), 4,4′-diaminobenzanilide, m-phenylenediamine, p-phenylenediamine, 4,4′-diaminodiphenylmethane, and diamines such as 2,4-diaminotoluene.

In the present invention, a tetracarboxylic acid component,
The molar ratio of each of the diamine components is such that EGTA, which is an essential component of tetracarboxylic acid, is a / (a + b) ≧ 0.6, and APPS, which is an essential component of diamine, is 0.05 ≦ c / (c + d).
+ E) ≦ 0.6, APB is 0.6 ≦ (c + d) / (c + d
+ E) ≦ 0.9. When the molar ratio is not within the above range, the heat resistance is remarkably inferior, the glass transition temperature is extremely high, the adhesion workability is poor, and the solubility in an organic solvent is lowered, which is not preferable. In particular, when the amount of EGTA, which is an essential component, is less than 60 mol% of the acid component, the glass transition temperature of the obtained polyimide resin becomes high, and the workability for bonding becomes extremely poor. 60 mol% of APPS
If it exceeds, the glass transition temperature will be lowered and the heat resistance will be remarkably deteriorated. Also, APPS is 5 mol%
In the following, after imidization, a phenomenon such as unfavorability due to poor solubility in an organic solvent becomes remarkable, which is not suitable for the purpose of the present invention. The APPS used in the present invention preferably has an n value in the formula (2) of 6 to 10 and an average molecular weight of 600 to 1000 from the viewpoint of glass transition temperature, adhesiveness and heat resistance.

The molar ratio of the acid component to the amine component in the polycondensation reaction is an important factor that determines the molecular weight of the obtained polyimide. It is well known that there is a correlation between polymer molecular weight and physical properties, especially number average molecular weight and mechanical properties,
The larger the number average molecular weight, the better the mechanical properties. Therefore, in order to obtain practically excellent strength as an adhesive, it is necessary to have a high molecular weight to some extent. In the present invention, the equivalent ratio r of the tetracarboxylic acid component and the diamine component is r
Must be in the range 0.900 ≦ (a + b) / (c + d + e) ≦ 1.06. If it is 0.900 or less, the molecular weight is low and the material becomes brittle, so the adhesive strength and heat resistance are poor and it is not suitable. On the other hand, if the acid is excessive, unreacted carboxylic acid is decarbonated during heating and causes gas generation and foaming, which is not preferable. Therefore, the acid amine molar ratio must be within the above range.

The reaction between the tetracarboxylic dianhydride and the diamine is carried out by a known method in an aprotic polar solvent. The aprotic polar solvent is N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMA
C), N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), diglyme, cyclohexanone,
1,4-dioxane and the like. The aprotic polar solvent is
Only one type may be used, or two or more types may be mixed and used. At this time, a non-polar solvent compatible with the aprotic polar solvent may be mixed and used. Aromatic hydrocarbons such as toluene, xylene and solvent naphtha are often used. The proportion of the nonpolar solvent in the mixed solvent is preferably 30% by weight or less. This is because if the amount of the non-polar solvent is 30% by weight or more, the solvent's dissolving power decreases and polyamic acid precipitates.

The reaction between the tetracarboxylic dianhydride and the diamine is carried out by dissolving a well-dried diamine component in a dehydrated and purified solvent and adding a ring-closing ratio of 98%, more preferably 99% or more, to the well-dried tetracarboxylic acid. The dianhydride is added to drive the reaction.

The polyamic acid solution thus obtained is subsequently heated and dehydrated in an organic solvent to form an imidized polyimide. Since the water generated by the imidization reaction interferes with the ring-closing reaction, an organic solvent that is incompatible with water is added to the system to azeotropically evaporate it and use a device such as a Dean-Stark tube to remove it from the system. To discharge. Dichlorobenzene is known as an organic solvent that is incompatible with water, but for electronics use, the aromatic hydrocarbon is preferably used because chlorine components may be mixed therein. In addition, the use of compounds such as β-picoline and pyridine as a catalyst for the imidization reaction is not hindered.

In the present invention, the higher the degree of imide ring closure, the better. If the imidization ratio is low, imidization occurs due to heat during adhesion and water is not generated, which is not preferable, so 95% or more, more preferably 98%. It is desired that the above imidization ratio be achieved.

In the present invention, the obtained polyimide solution may be used as it is, but it is preferable to put the polyimide solution in a poor solvent to reprecipitate and precipitate the polyimide resin to remove unreacted monomers and to purify. The purified, filtered and dried polyimide resin is dissolved again in an organic solvent to form a varnish. The solvent used at this time may be the same as the reaction solvent. In consideration of workability in the coating and drying step, it is also preferable to select a solvent having a low boiling point, preferably a boiling point of 200 ° C or lower. As a solvent at 200 ° C. or lower, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone as a ketone solvent in the present invention,
Examples of the ether solvent include 1,4-dioxane, tetrahydrofuran and diglyme, and examples of the amide solvent include N, N-dimethylformamide and N, N-dimethylacetamide. These solvents may be used alone or 2
It is also possible to use a mixture of two or more species.

If necessary, various additives such as a leveling agent, a leveling agent and a defoaming agent can be added to the polyimide resin varnish. In addition, an aromatic hydrocarbon solvent may be used within the range where it is uniformly dissolved in order to control the evaporation rate of the solvent.

In the present invention, the polyimide resin as a film adhesive is usually obtained by casting or coating a polyimide resin solution (varnish). For example, a release sheet such as a roll, a metal sheet or a polyester sheet. A film is formed on top of it with a flow coater, roll coater, etc., and after heating and drying it is peeled off to form a film adhesive, or a heat-resistant film substrate is used as a support, and a film layer is similarly formed on one or both sides. And a film adhesive together with the support.

The heat-resistant film base material used in the present invention is that the polyimide resin film has a small coefficient of thermal expansion and is excellent in dimensional stability against temperature changes, is flexible and easy to handle, and the adhesive resin of the present invention. It is preferable in that it has excellent adhesion with. Especially glass transition temperature of 350 ℃
The above polyimide resin is excellent in performance as a film adhesive and workability and stability in the step of applying and drying a polyimide resin varnish as an adhesive layer.

For coating and drying the adhesive varnish on the base film, an apparatus combining a hot air drying furnace with a flow coater or a roll coater can be used. After applying the polyimide resin varnish, the polyimide resin varnish is introduced into a hot air drying oven and dried at a temperature and an air volume sufficient to vaporize the solvent of the polyimide resin varnish.

The method of using the film adhesive of the present invention is not particularly limited, but it can be used as an adhesive tape, for example, by thermocompression bonding with a heat block which is cut into a predetermined shape and heated. ..

[0023]

The film adhesive of the present invention is characterized in that it is obtained by applying a completely imidized polyimide resin having a specific structure, which is soluble in an organic solvent having a low boiling point, to a heat resistant film substrate. The polyimide resin in the adhesive layer can achieve extremely low levels of ionic impurities by being reprecipitated and purified, and the gas generated during heating can be almost completely eliminated by combining it with imidization using a solvent with a low boiling point. You can

Further, although it has excellent heat resistance, it can be bonded at a low temperature in an extremely short time as compared with a thermosetting adhesive which involves a chemical reaction. The dimensional accuracy of the adhesive portion can be improved. Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

[0025]

【Example】

(Example 1) NMP1260 dehydrated and refined in a four-necked flask equipped with a dry nitrogen gas introduction tube, a condenser, a thermometer, and a stirrer.
Add g and stir vigorously for 10 minutes while flowing nitrogen gas. Next, 58.47 g (0.200 mol) of APB and APPS 116.
Add 00g (average molecular weight 870, 0.133mol) and bring the system to 60 ℃.
Heat to stir and stir until uniform. After the solution was homogeneously dissolved, the system was cooled to 5 ° C. in an ice-water bath, 149.20 g (0.364 mol) of EGTA was added in powder form over 15 minutes, and then stirring was continued for 3 hours. During this time, the flask was kept at 5 ° C.

Thereafter, the nitrogen gas introducing pipe and the cooler were removed,
A Dean-Stark tube filled with xylene was attached to the flask, and 140 g of xylene was added to the system. Instead of the oil bath, the system was heated to 200 ° C. and the generated water was removed from the system. After heating for 4 hours, generation of water from the system was not observed. After cooling, this reaction solution was poured into a large amount of methanol to precipitate a polyimide resin. After filtering solids at 80 ° C
It was dried under reduced pressure for 12 hours and the solvent was removed. When the infrared absorption spectrum was measured by the KBr tablet method, an absorption of 5.6 μm derived from the cyclic imide bond was observed, but an absorption of 6.06 μm derived from the amide bond was not observed.
It was confirmed to be 0% imidized. 325.52 g (yield 93%) of the polyimide resin thus obtained was dissolved in cyclohexanone / toluene (90/10 w / w%),
A polyimide resin varnish having a solid content of 30% was prepared.

A 50 μm thick polyimide film (Upilex S, Ube Industries, Ltd.)
Manufactured) and dried in a hot air circulation dryer at 120 ° C for 0.5 hours for 20 hours.
It heat-dried at 0 degreeC for 1 hour. After cooling, the thickness of the film was measured and the thickness of the adhesive layer was calculated to be 20 μm.
The adhesive surface of the obtained film showed no tackiness at room temperature and was tack-free.

This film adhesive was adhered to the surface of the 35 μm electrolytic copper foil having a metallic luster not subjected to black treatment by a hot press having a heat block made of phosphor bronze to prepare a test piece. Adhesion condition is 210 ℃ for 2 seconds by thermocompression bonding and 210 ℃ after releasing the pressure.
Annealed for 30 seconds. The pressure applied to the adhesive surface was 4 kg / cm ^{2 as} a result of calculation from the gauge pressure and the adhesive area. The 180 degree peel strength of this test piece was 1.81 kgf / cm. Also,
The 180 degree peel strength after 168 hours of treatment at 85 ° C and 85%
It was 1.46 kgf / cm, and showed excellent adhesion to copper.
At the fractured surface, the adhesive resin layer was cohesively destroyed and no foaming was observed. It was also found that the polyimide film as the base material also exhibits excellent adhesion. The results including other performances are shown in Table 1. At this time, the molar ratio of acid and amine is a / (a + b) = 1 and c / (c + d + e), respectively.
= 0.45, (c + d) / (c + d + e) = 1.

(Examples 2 to 4) In the same manner as in Example 1, a polyimide resin varnish was prepared with the types and proportions of the acid and amine components shown in Table 1 and applied to a polyimide film for film adhesion. The agent was created. These performances are shown in Table 1.

[0030]

[Table 1]

Example 5 The biaxially stretched polyester film was coated with the polyimide resin varnish obtained in Example 1 and heated and dried at 120 ° C. for 30 minutes and 200 ° C. for 1 hour. After cooling, the polyester film was peeled off to obtain a film adhesive. This film showed an excellent adhesive force to the copper foil and was extremely effective in adhering the semiconductor chip and the lead frame.

(Comparative Example 1) In exactly the same manner as in Example 1, AP
58.47 g (0.200 mol) B, 116 g (0.133 mol) APPS, 1,2,4,5-benzenetetracarboxylic dianhydride 42.7
A polyamic acid was prepared from 5 g (0.196 mol) and 40.54 g (0.131 mol) of EGTA and further imidized by heating, but as the reaction proceeded, solids were deposited and a soluble polyimide resin varnish could be obtained. There wasn't. At this time, the molar ratio of acid and amine is a / (a + b) = 0.
5, c / (c + d + e) = 0.4, (c + d) / (c + d
+ E) = 0.4.

(Comparative Example 2) As in Example 1, APB 5
8.47 g (0.200 mol) and BAPSM 86.50 g (0.200 mol), EGTA 72.96 g (0.235 mol) and BPDA 46.1
A polyamic acid was prepared from 3 g (0.157 mol) and further heated to imidize. After reprecipitation purification, it tried to dissolve in cyclohexanone but did not dissolve, but dissolved in NMP. This was applied to a polyimide film in the same manner as in Example 1, but the drying conditions were 120 ° C. for 1 hour, 250 ° C. for 1 hour, 300 ° C. 0.5
It was time. In the evaluation of the adhesiveness to copper, the peel strength was 0.04 kgf / cm when pressure-bonded at 210 ° C. for 70 seconds. At this time, the molar ratio of acid and amine is a / (a + b) =
0.6, c / (c + d + e) = 0, (c + d) / (c + d +
e) = 0.5.

(Comparative Example 3) As in Example 1, APB 5
8.47 g (0.200 mol) and APPS 58.00 g (0.067 mol), EGTA 32.43 g (0.105 mol) and BTDA 50.5
A polyamic acid was prepared from 3 g (0.157 mol) and further heated to imidize. After reprecipitation purification, it was dissolved in DMF. This was applied to a polyimide film in the same manner as in Example 1, but the drying conditions were 120 ° C. for 1 hour and 250 ° C. for 1.5 hours. In the evaluation of the adhesiveness to copper, the peel strength was 0.12 kgf / cm after pressure bonding at 210 ° C. for 70 seconds. Acid at this time,
The amine molar ratios are a / (a + b) = 0.4, c /
(C + d + e) = 0.25, (c + d) / (c + d + e) =
It is 1.

As compared with the examples, when the molar ratio of tetracarboxylic dianhydride and diamine is out of the range of the present invention,
It can be seen that the solubility and adhesive strength of the polyimide resin are significantly reduced.

[0036]

According to the present invention, it is possible to provide a highly reliable film adhesive having both heat resistance and adhesive workability. Particularly, when copper, which is easily oxidized, is used as a lead frame, it can be bonded at a low temperature in a short time, and can be bonded without oxidizing the surface, which is industrially extremely useful as a semiconductor mounting material.

Claims (3)

[Claims] 1. An acid component of ethylene glycol bistrimellitic acid dianhydride a mole and another tetracarboxylic acid dianhydride b mole, and an amine component of α, ω-bis (3-aminopropyl).
Consisting of c moles of polydimethylsiloxane, d moles of 1,3-bis (3-aminophenoxy) benzene and other moles of diamines, a / (a + b) ≧ 0.6, 0.05 ≦ c / (c + d +
e) ≤ 0.6, 0.6 ≤ (c + d) / (c + d + e), and
A film adhesive made of a polyimide resin having a glass transition temperature of 350 ° C. or lower, which is obtained by reacting both components at a ratio of 0.900 ≦ (a + b) / (c + d + e) ≦ 1.06 to cause imide ring closure. 2. A film adhesive in which the adhesive of claim 1 is applied to one or both sides of a heat resistant film substrate. 3. The heat-resistant film substrate is a polyimide film having a glass transition temperature of 350 ° C. or higher.
Film adhesive.