JP2721445B2 - Film adhesive for electronics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, while semiconductor chips have been increased in size due to higher functions and larger capacities, the package size has been required to maintain the same external shape as in the past due to restrictions on printed circuit design and the like. Several new mounting methods have been proposed for high-density semiconductor chips and high-density mounting. In this new mounting method, COL (chip-on-chip) that mounts the chip on a lead frame without die pad
There are two structures: a lead) and a LOC (lead-on-chip) on which a lead is mounted on a chip. In the conventional method, the chip area is too large to secure the area of the inner lead.However, in these methods, the semiconductor chip and the lead frame are bonded with double-sided adhesive tape, and despite the increase in chip area due to large capacity, the same outer shape as the conventional one Package. Further, advantages such as rationalization of wiring in the chip and wire bonding and speeding up of signals by shortening the wiring can be achieved.

In a semiconductor device having a COL or LOC structure, a semiconductor chip and a lead frame are fixed by an adhesive. The 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 cycling. Also, the fact that there are many volatile components at the time of heat bonding,
It is not preferable because the working environment and the lead are contaminated. Further, in consideration of mass productivity, it is desired that bonding can be performed in as short a time as possible. Conventionally, for these uses, a paste-like adhesive or a heat-resistant base material coated with an adhesive has been used. Epoxy resin, acrylic resin, or rubber-phenol resin thermosetting resin is used as the adhesive, but it contains many ionic impurities, requires high temperature and long time for heat curing, and has poor productivity. It is hard to say that the above requirements are satisfied, such as a large amount of volatile matter during curing and high hygroscopicity, and no satisfactory material has been found.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made as a result of intensive studies to obtain a film adhesive excellent in heat resistance which can be bonded in a short time at a low temperature, and as a result, a film obtained by applying a specific polyimide resin to a heat resistant film. The present inventors have found that an adhesive solves the above-mentioned problems, and have reached the present invention.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a heat-resistant resin film which is obtained by coating a resin having a polyimide bond having a glass transition temperature of 350 ° C. or less on one or both surfaces of a heat-resistant resin film. Film adhesive.

The resin having a polyimide bond forming the adhesive layer is composed of a mole of 4,4'-oxydiphthalic dianhydride (formula (1), hereinafter abbreviated as ODPA) and b mole of another tetracarboxylic dianhydride. Acid component, α, ω-bis (3-aminopropyl) polydimethylsiloxane (Formula (2), hereinafter abbreviated as APPS) c
Mol, 1,3-bis (3-aminophenoxy) benzene (formula
(3) (hereinafter abbreviated as APB) a polyimide resin containing d mole and e mole of other diamine as an amine component (where b and b)
e may each be 0) .

[0007]

Embedded image

Other tetracarboxylic dianhydrides usable in the present invention include, for example, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3', 4,4 ' -Benzophenonetetracarboxylic dianhydride (BTDA), 1,2,4,
5-benzenetetracarboxylic dianhydride (PMDA), 2,
Tetracarboxylic dianhydrides such as 2'-bis (4- (3,4-dicarboxyphenylcarboxy) phenyl) propane dianhydride, and dicarboxylic anhydrides such as phthalic anhydride as molecular weight regulators. Can be.

Other diamines usable in the present invention include, for example, 1,4-bis (3-aminophenoxy) benzene,
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 (3,3'-DDE), 3,4 '
-Diaminodiphenyl ether (3,4'-DDE), 4,4'-
Diaminodiphenylsulfone (4,4'-DDS), 3,3'-
Diaminodiphenylsulfone (3,3'-DDS), 2,2-
Bis-4-aminophenylhexafluoropropane (BA
PF), 2,2-bis-4-aminophenoxyphenylhexafluoropropane (BAPPF), bis-4- (4-aminophenoxy) phenylsulfone (BAPS), bis-4- (3
-Aminophenoxy) phenylsulfone (BAPS
M), 4,4'-diaminobenzanilide (DABAN),
m-phenylenediamine, p-phenylenediamine, 4,4 '
Diamines such as -diaminodiphenylmethane (DDM).

In the present invention, the ratio of each of the acid component and the amine component is determined by ODPA which is an essential component of tetracarboxylic acid.
Is a / (a + b)> 0.6, A which is an essential component of diamine
PPS is 0.1 <c / (c + d + e) <0.6, APB is 0.6
<(C + d) (c + d + e) <0.9. If the ratio is not within the above range, the heat resistance is extremely poor, or the glass transition temperature is extremely high, the bonding workability is poor, and the solubility in organic solvents is unfavorably reduced. In particular, when the ODPA, which is an essential component, is 60 mol% or less of the acid component, the glass transition temperature of the obtained polyimide resin is increased, and the adhesiveness is remarkably deteriorated. APP
If S exceeds 60 mol%, the glass transition temperature will be lowered and the heat resistance will be remarkably inferior. Also, APPS
If the content is less than 10 mol%, phenomena such as poor solubility in an organic solvent after imidization become remarkable, which is not suitable for the purpose of the present invention.

The APPS used in the present invention preferably has a value of n in the formula (1) of 6 to 10 and an average molecular weight of 600 to 1000 in terms of glass transition temperature, adhesiveness and heat resistance. .

The molar ratio between the acid component and 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 the molecular weight and physical properties of a polymer, in particular, the 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 ratio of the acid component to the amine component is 0.950 <(a + b)
/(C+d+e)<1.02. 0.
When the molecular weight is less than 950, the molecular weight is low and the material is brittle, so that the adhesive strength and the heat resistance are inferior. If it is 1.02 or more, unreacted carboxylic acid is undesirably decarbonated during heating, causing gas generation and foaming. For this reason, the acid amine molar ratio must be in the above range.

The reaction between the tetracarboxylic dianhydride and the diamine is carried out in a polar aprotic solvent by a known method. The aprotic polar solvent is N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMA
C), N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), diglyme, cyclohexanone,
And 1,4-dioxane. 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 when the amount of the nonpolar solvent is 30% by weight or more, the dissolving power of the solvent decreases and polyamic acid is precipitated.

The reaction between the tetracarboxylic dianhydride and the diamine is carried out by dissolving a well-dried diamine component in a solvent that has been purified by dehydration, and adding a well-dried tetracarboxylic acid having a ring closure of 98%, more preferably 99% or more. The reaction is proceeded by adding dianhydride.

The polyamic acid solution thus obtained is subsequently heated and dehydrated and cyclized in an organic solvent to give an imidized polyimide. Since water generated by the imidization reaction hinders the reaction, an organic solvent that is incompatible with water is added to the system and azeotroped to form Dean-Stark.
Discharge out of the system using a pipe or other device. As the organic solvent incompatible with water, the aromatic hydrocarbon is preferable. Solvents such as dichlorobenzene are also known, but it is not preferable that chlorine components be mixed in for use in electronics. Further, use of a compound such as β-picoline or pyridine as a catalyst for the imidization reaction is not hindered.

If the imidation ratio is low, imidization occurs due to heat at the time of bonding, and water is generated, which is not preferable. Therefore, it is necessary that the imidation ratio be at least 95%, more preferably at least 98%. It is. Incidentally, in the case of the NMP / aromatic hydrocarbon system, the reaction is preferably allowed to proceed at a temperature of 150 ° C. or higher.

In the present invention, the obtained polyimide solution may be applied as it is to a heat-resistant film substrate, but the polyimide solution is poured into a poor solvent to reprecipitate the polyimide resin to remove unreacted monomers. Preferably, it is purified. The purified, filtered and dried polyimide resin is again dissolved in an organic solvent to form a varnish. The solvent used at this time may be the same as the reaction solvent, but considering the workability of the coating and drying step, it is preferable to select a solvent having a low boiling point, preferably a boiling point of 200 ° C. or lower. In the present invention, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone and cyclohexanone as ketone solvents are used as solvents at 200 ° C or lower, 1,4-dioxane, tetrahydrofuran, diglyme as ether solvents, and N, N as amide solvents. -Dimethylformamide and N, N-dimethylacetamide. These solvents may be used alone or in combination of two or more. Various additives such as a leveling agent, a leveling agent, and a defoaming agent for improving surface smoothness can be added to the polyimide varnish as needed. In addition, an aromatic hydrocarbon-based solvent can be used within a range in which the solvent is uniformly dissolved in order to adjust the evaporation rate of the solvent.

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

The coating and drying of the varnish on the substrate film can be performed by using a device combining a hot air drying oven and a roll coater. After applying the polyimide resin varnish, it is guided to a hot air drying oven and dried at a temperature and air volume sufficient to evaporate the solvent of the polyimide resin varnish.

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

[0021]

The film adhesive of the present invention is obtained by applying a completely imidized polyimide resin having a specific structure, which is soluble in a low-boiling organic solvent, to a heat-resistant film substrate. By reprecipitating and refining the polyimide resin of the adhesive layer, it is possible to achieve extremely low levels of ionic impurities, and use a solvent with a low boiling point to make it imidized, so that gas generated during heating is almost completely eliminated. Can be.

In addition, although it is excellent in heat resistance, it can be bonded in a very short time at a low temperature as compared with a thermosetting adhesive which involves a chemical reaction. The dimensional accuracy of the bonded 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.

[0023]

【Example】

(Example 1) 989 g of dehydrated and purified NMP in a four-necked flask equipped with a dry nitrogen gas inlet tube, a cooler, a thermometer, and a stirrer
And stir vigorously for 10 minutes while flowing nitrogen gas. Next, 1,3-bis (3-aminophenoxy) benzene 58.47
g (0.200 mol) and 116.00 g of α, ω-bis (3-aminopropyl) polydimethylsiloxane (average molecular weight: 870, 0.133 mol) are added, and the system is heated to 60 ° C. and stirred until uniform. After dissolving uniformly, the system was cooled to 5 ° C in an ice water bath, and 4,4'-
81.07 g (0.261 mol) of oxydiphthalic dianhydride and 3,
3 ', 4,4'-biphenyltetracarboxylic dianhydride 19.22 g
(0.065 mol) in the form of a powder was added over 15 minutes, and then stirring was continued for 3 hours. During this time, the flask was kept at 5 ° C.

After that, remove the nitrogen gas inlet pipe and the cooler,
A Dean-Stark tube filled with xylene was attached to the flask, and 109.9 g of xylene was added to the system. The system was heated to 200 ° C. instead of the oil bath, and the generated water was removed from the system. After heating for 4 hours, no water was generated from the system. After cooling, the reaction solution was poured into a large amount of methanol to precipitate a polyimide resin. After filtration of the solid content, 80 ℃
And dried under reduced pressure for 12 hours to remove the solvent. When an infrared absorption spectrum was measured by a KBr tablet method, an absorption of 5.6 μm derived from a cyclic imide bond was recognized, but an absorption of 6.06 μm derived from an amide bond could not be recognized.
It was confirmed that imidation was 0%. 251.56 g (yield 91.55%) of the polyimide resin thus obtained was dissolved in cyclohexanone / toluene (90/10 w / w%) to prepare a polyimide resin varnish of 30% RC.

This polyimide resin varnish was applied to a 50 μm-thick polyimide film (UPILEX S, manufactured by Ube Industries, Ltd.) and dried by heating in a hot air circulating dryer at 120 ° C. for 0.5 hour and at 200 ° C. for 1 hour. After cooling, the thickness of the film was measured, and the thickness of the adhesive layer was calculated to be 19 μm. The adhesive surface of the obtained film showed no tackiness at room temperature and was tack-free.

The film adhesive was adhered to a 35 μm electrolytic copper foil having a non-black surface with a metallic luster by a hot press having a heat block made of phosphor bronze to prepare a test piece. Bonding conditions: 210 ° C for 2 seconds at 210 ° C after releasing pressure
For 10 seconds. The pressure applied to the bonding surface was 4 kg / cm ^{2 as} a result of calculation from the gauge pressure and the bonding area. The 180 degree peel strength of this test piece was 2.81 kgf / cm. Also,
180 degree peel strength after 168 hours treatment under 85 ℃ 85% environment
2.66 kgf / cm, showing excellent adhesion to copper.
In the fractured surface, the adhesive resin layer was cohesively broken and no foaming was observed. It was found that the adhesive strength was excellent even for the polyimide film as the base material. In addition, polyimide resin (Sumiresin Excel CRC manufactured by Sumitomo Bakelite)
-6061P) was examined for adhesion to silicon wafers coated with 2.01kgf / cm and 1.75k, respectively.
gf / cm was obtained. The results including other performances are shown in Table 1.
At this time, the molar ratio of the acid and the amine is a / (a + b), respectively.
= 0.8, c / (c + d + e) = 0.4, (c + d) / (c +
d + e) = 1.

(Examples 2 to 5) In the same manner as in Example 1, a polyimide resin varnish was prepared and applied to a polyimide film to prepare a film adhesive. These performances are the first
It is shown in the table.

[0028]

[Table 1]

(Comparative Example 1) 1,4-
58.47 g (0.200 mol) of bis (3-aminophenoxy) benzene, 116 g (0.133 mol) of α, ω-bis (3-aminopropyl) polydimethylsiloxane, 1,2,4,5-benzenetetracarboxylic dianhydride A polyamic acid was prepared from 42.75 g (0.196 mol) of the product and 40.54 g (0.131 mol) of 4,4′-oxydiphthalic dianhydride, and further heated to imidate.
As the reaction proceeded, solids precipitated, and a soluble polyimide varnish could not be obtained. At this time, the molar ratios of the acid and the amine are a / (a + b) = 0.5 and c / (c + d, respectively).
+ E) = 0.4 and (c + d) / (c + d + e) = 0.4.

Comparative Example 2 In the same manner as in Example 1, 1,3-bis
58.47 g (0.200 mol) of (3-aminophenoxy) benzene and 86.50 of bis-4- (3-aminophenoxy) phenylsulfone
g (0.200 mol), 7,4,4'-oxydiphthalic dianhydride 72.9
Polyamic acid was prepared from 6 g (0.235 mol) and 46.13 g (0.157 mol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, and imidized by heating. After reprecipitation purification, it was tried to be dissolved in cyclohexanone, but was not dissolved.
Dissolved in P. 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, and 300 ° C. for 0.5 hour. In the evaluation of the adhesiveness to copper, pressure bonding was performed at 210 ° C. for 70 seconds, but the peel strength was 0.04 kgf / cm. At this time, the molar ratio of the acid and the amine is a /
(A + b) = 0.6, c / (c + d + e) = 0, (c + d)
/(C+d+e)=0.5.

Comparative Example 3 In the same manner as in Example 1, 1,3-bis
58.47 g (0.200 mol) of (3-aminophenoxy) benzene and α, ω-bis (3-aminopropyl) polydimethylsiloxane
58.00 g (0.067 mol), 32.43 g (0.105 mol) of 4,4'-oxydiphthalic dianhydride and 50.53 g (0.157 mol) of 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride The acid was prepared 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 condition was 120 ° C.1
Time, 250 ° C., 1.5 hours. In the evaluation of the adhesiveness to copper, pressure bonding was performed at 210 ° C. for 70 seconds, but the peel strength was 0.12 kgf / cm. At this time, the molar ratio of the acid and the amine is a /
(A + b) = 0.4, c / (c + d + e) = 0.25, (c +
d) / (c + d + e) = 1.

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

[0033]

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

Continued on the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical display location H01L 23/50 H01L 23/50 Y

Claims (3)

(57) [Claims] 1. A heat-resistant film substrate having, on one or both sides thereof, an acid component of amol 4,4′-oxydiphthalic dianhydride and b mol of another tetracarboxylic dianhydride, and an amine component of α, ω- It consists of c mole of bis (3-aminopropyl) polydimethylsiloxane, d mole of 1,3-bis (3-aminophenoxy) benzene, and e mole of another diamine (however, b and e are the same).
Each may be 0) , a / (a + b)> 0.6, 0.1
<C / (c + d + e) <0.6, 0.6 <(c + d) / (c +
d + e) and 0.950 <(a + b) / (c + d + e) <
A film adhesive having a polyimide resin layer formed at a ratio of 1.02 and having a glass transition temperature of 350 ° C. or lower. 2. The film adhesive according to claim 1, wherein the heat-resistant film substrate is a polyimide film having a glass transition temperature of 350 ° C. or higher. 3. The acid component is a mole of 4,4'-oxydiphthalic dianhydride and b mole of another tetracarboxylic dianhydride, and the amine component is α, ω-bis (3-aminopropyl) polydimethylsiloxane c. Mol, d-mol of 1,3-bis (3-aminophenoxy) benzene and e-mol of other diamine (provided that b and
e may each be 0) , a / (a + b)>
0.6, 0.1 <c / (c + d + e) <0.6, 0.6 <(c + d)
/ (C + d + e) and 0.950 <(a + b) / (c + d)
+ E) a glass transition temperature of 350 formed at a ratio of <1.02
A method for producing a film adhesive, comprising applying a varnish obtained by dissolving a polyimide resin having a boiling point of 200 ° C. or lower in an organic solvent having a boiling point of 200 ° C. or lower to one or both surfaces of a heat-resistant film substrate and drying.