JP2740590B2 - Thermoconductive adhesive film - Google Patents

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 conductivity and heat resistance and can be used by thermocompression bonding.

[0002]

2. Description of the Related Art Heretofore, some heat-resistant thermocompression-bondable film adhesives have been known. For example, JP-A 1-2822
No. 83, polyamide-imide or polyamide hot melt adhesive, JP-A-58-157190, a method of manufacturing a flexible printed circuit board with a polyimide-based adhesive, JP-A-62-235382 and JP-A-62-235383 describes a thermosetting polyimide film adhesive. However, polyamide-based or polyamide-imide-based resins have the disadvantage that the water absorption is increased due to the hydrophilic nature of the amide group, and there is a limit to using them as adhesives for electronics applications requiring reliability. . In addition, the standard conditions for thermocompression bonding of film adhesives described in other publications are 275 ° C, 50 kgf / cm ² , and 30 minutes, which require electronic components sensitive to heat and pressure and mass productivity. However, it was not necessarily advantageous as a film adhesive for various uses.

On the other hand, conventionally used epoxy resins,
Adhesives such as phenolic and acrylic are relatively low temperature,
Although it has the advantage that it can be thermocompression bonded at a low pressure, it has to be provided with a somewhat long curing time because it is a thermosetting type. Although a thermoplastic resin is often used as a hot-melt adhesive, it has a disadvantage of poor heat resistance.

On the other hand, Au-Si eutectic has conventionally been used for joining a semiconductor chip such as an IC or an LSI to a lead frame. However, since Au is expensive, conductive resin paste has recently become the mainstream. It has become As this kind of conductive resin paste, JP-A-55-25482 or 52-107036
As disclosed in Japanese Patent Application Laid-Open Publication No. H10-209, a silver paste in which an epoxy resin is generally used as a binder and silver powder is mixed with the binder has been mainly used because of good workability and adhesiveness. However, such a paste-like adhesive cannot control the thickness without strictly controlling the amount of application, there is creeping up of the paste on the chip side surface, and it cannot be uniformly applied to the surface-processed lead frame. There is a problem, and a film adhesive having conductivity and heat resistance has been desired as a method for solving these problems.

[0005]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies to obtain a conductive film adhesive having excellent heat resistance and capable of thermocompression bonding at a low temperature, a low pressure and in a short time. It has been found that an adhesive formed into a film by dispersing a necessary amount of a conductive filler in polyimide siloxane having a structure can achieve the above-mentioned target, and the present invention has been completed. It is an object of the present invention to provide a film adhesive having both conductivity, heat resistance and workability of thermocompression bonding.

[0006]

According to the present invention, there is provided the following formula (1):
A mole of the acid-terminated silicone compound A represented by (2)

[0007]

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And 4,4′-O as another acid dianhydride component
Xydiphthalic dianhydride and / or 3,3 ', 4,4'-benzofu
Acid component consisting of B mol of enonetetracarboxylic dianhydride
(However, 0.09 ≦ A / (A + B) ≦ 0.33) and the expression
C mole of diaminosilicone compound represented by (3)

[0009]

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[0010] 1,3-bis (3-
Aminophenoxy) benzene and / or 2,4-diaminot
Amine component consisting of D moles of ruene (provided that 0.4 ≦ C /
(C + D) ≦ 0.7) and ( A + B) / (C + D)
Reaction is carried out in the range of 0.8 to 1.2, and at least 80% or more of polyimide imide is imidized, and a conductive filler of 50 to 900 wt% with respect to polyimide siloxane is used. is there.

The acid dianhydride used in the present invention is
Acid-terminated silicone compound , 4,4'-oxydiphthalic acid
Water (hereinafter abbreviated as ODPA) and 3,3 ', 4,4'-benzophene
Non-tetracarboxylic dianhydride (hereinafter abbreviated as BTDA)
It is.

The acid-terminated silicone compound used in the present invention is a phthalic anhydride represented by the following formula (1):
Terminal silicone compound or Nagic represented by formula (2)
It is an acid anhydride terminated silicone compound.

[0013]

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The diamine component used in the present invention is a diaminosilicone compound represented by the formula (3) and other diamine components. Other diamines are 1,3-bis (3-
Aminophenoxy) benzene and / or 2,4-diaminot
Ruen.

The reaction between the acid dianhydride and the diamine in the present invention can be carried out by a known method. One of the acid dianhydride component and the diamine component is dissolved or suspended in an organic solvent in advance, and the other component is gradually added in a state of powder, liquid or dissolved in an organic solvent. Since the reaction is exothermic, the reaction is preferably carried out while cooling and keeping the temperature of the reaction system near room temperature.

The molar ratio (A + B) / (C + D) between the acid dianhydride component and the diamine component is preferably in the vicinity of an equivalent, particularly in the range of 0.8 to 1.2. If either one is too large, the molecular weight does not increase, and the heat resistance and mechanical properties deteriorate, which is not preferable. After reacting at around room temperature to synthesize polyamic acid, imidization can be carried out by a known method such as heating or using an acetic anhydride / pyridine-based catalyst. It is desirable that the imidization ratio is at least 80% or more. When the imidation ratio is lower than 80%, imidization proceeds during the subsequent film formation and thermocompression bonding to generate moisture, which causes voids and lowers the adhesive strength, which is not preferable.

The value of A / (A + B) is 0.09 or more and 0.3
3 or less, and the value of C / (C + D) is
It is necessary to be 0.4 or more and 0.7 or less. A /
The value of (A + B) is less than 0.09 or C / (C + D)
If the value is less than 0.4, the heat fusibility decreases,
A thermocompression bonding condition of at least 300 ° C. or more or 50 kgf / cm ² or more is required, which is not preferable in terms of mass productivity.
Also, the value of A / (A + B) exceeds 0.33, or
When the value of C / (C + D) exceeds 0.7, the heat fusibility is high.
It is too unfavorable in terms of mass productivity. A / (A
+ B) is 0.09 or more and 0.33 or less and C / (C
+ D) is 0.4 ° C. or more and 0.7 or less, 250 ° C.
At the following temperature and under a pressure of 20 kgf / cm ² or less.
Thermocompression bonding can be performed in a short time of less than one minute, and good adhesive strength can be achieved.

[0018]

The organic solvent used in the present invention is not particularly limited, but may be a single solvent or a mixed solvent of two or more solvents as long as it can be uniformly dissolved. Typical solvents of this type are N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylformamide, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethylsulfoxide, Hexamethylphosphoamide, N-methyl
-2-pyrrolidone, pyridine, dimethyl sulfone, tetramethyl sulfone, dimethyltetramethylene sulfone, γ
-Butyrolactone, diglyme, tetrahydrofuran,
There are methylene chloride, dioxane, cyclohexanone, and the like, and a poor solvent can be used as a volatilization regulator, a film smoothing agent, and the like as long as the solvent can be uniformly dissolved.

The conductive filler used in the present invention is not particularly limited, but examples of usually preferably used conductive fillers include gold, silver, copper, nickel, and aluminum. These can be used alone or as a mixture. Usually, the amount of such conductive filler is 50 to 900% based on the resin.
It is preferable to use it. If it is less than 50% by weight, the resulting film-like adhesive layer does not exhibit electrical conductivity, and if it exceeds 900% by weight, the amount of resin serving as a binder decreases, and thus it is not preferable because sufficient adhesive strength cannot be obtained. The shape is not particularly limited, and may be, for example, flakes, dendrites, spheres, and the like, and one or a mixture of two or more of these metal powders may be used. Although the particle size is not particularly limited, the average particle size is preferably 50 μm or less in consideration of the thickness of the final adhesive layer, workability, and the like.

The method of using the thermocompression-bondable conductive film adhesive of the present invention is not particularly limited, but usually, a well-known imidized varnish is prepared by adding a conductive filler to a known dispersion. After three-roll, ball mill, crusher, etc. that are uniformly dispersed in a device and made into a paste, the material is applied to a substrate having excellent release properties such as Teflon,
The solvent is volatilized by heat treatment to form a film, and the film is peeled from the substrate to obtain a conductive film. After being sandwiched between the adherends, thermocompression bonding is performed. Or after pre-coating on the adherend, after heat treatment to sufficiently evaporate the solvent,
Thermocompression bonding can also be performed together with one adherend.

Various additives can be added to the polyimide siloxane, which is the base resin of the adhesive of the present invention, if necessary. For example, a surface smoothing agent when applied to a substrate, a leveling agent for increasing wettability, various surfactants, a silane coupling agent, and various crosslinking agents for increasing the heat resistance of the adhesive after thermocompression bonding. Additive.
These additives can be used in an amount that does not impair the properties of the film adhesive.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

[0024]

【Example】

Example 1 A four-necked separable flask equipped with a thermometer, a stirrer, a material inlet, and a dry nitrogen gas inlet tube was charged with 1,
3-bis (3-aminophenoxy) benzene (APB) 17.54
g (0.06 mol), diaminosilicone compound 3 of the following formula
3.67 g (0.04 mol)

[0025]

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Was added to 300 g of N-methyl-2-pyrrolidone (NM
P) and dissolved in 4,4'-oxydiphthalic dianhydride (O
DPA) 24.82 g (0.08 mol), acid-terminated silicone compound of the following formula 20.40 g (0.02 mol)

[0027]

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Was gradually added as a solid over 30 minutes, and then stirring was continued for 2 hours. During this time, a dry nitrogen gas was supplied, and the system was cooled in an ice bath before adding the acid anhydride, and the system was kept at 20 ° C. throughout the reaction.

Next, 60 g of xylene was added to the system,
Remove the dry nitrogen inlet tube, replace with a Dean starch reflux condenser, remove the ice bath and heat in an oil bath to raise the temperature of the system. Heating was continued while removing the water generated by the imidation out of the system by azeotropic distillation with toluene,
The reaction was terminated 5 hours after imidation was carried out at 0 to 160 ° C and no more water was generated. The polyimide varnish was added dropwise to 30 liters of methanol with stirring over 1 hour to precipitate the resin, and only the solid content was recovered by filtration, followed by drying in a vacuum dryer at 120 ° C. under reduced pressure for 5 hours. I let it. FT of the polyimide siloxane thus obtained
-IR spectrum was measured, and the imidation ratio was determined from the absorption based on the amide bond before imidization appearing at 1650 cm ^-1 and the absorption based on the imide ring appearing at 1780 cm ^-1 , which was 100%
It was found to be imidized.

This polyimide siloxane is dissolved in diethylene glycol dimethyl ether (diglyme),
The concentration was adjusted to 10%. Silver powder having an average particle size of 3 μm was added to the varnish so as to be 400 wt% with respect to the polyimidesiloxane, and uniformly dispersed using a three-roll mill to obtain a paste. This paste is cast on a polished Teflon plate using an applicator, and dried in a dryer.
The solvent was volatilized by heating at 120 ° C. for 5 hours, and peeled off from the Teflon substrate to form a film having a thickness of 25 μm. From this film, cut out a 3mm x 3.5mm square size, sandwiched between a copper lead frame and a 3mm x 3.5mm square silicon chip, and applied a 500g load on a 250 ° C hot plate ( About 4.76kgf / cm ² ), 10
After thermocompression bonding in seconds, cooled to room temperature and measured the shear strength with a push-pull gauge, the silicon chip was broken at a value of 10 kgf or more, and it was so strong that accurate shear strength could not be obtained. Was. Next, the same adhesive sample was placed on a hot plate at 260 ° C. for 10 seconds, and the shear strength was measured. As a result, a strength of 2.0 kgf was obtained. The mode of failure was cohesive failure, and a part of the film remained on both the lead frame and the chip. No void was observed in the film. When the volume resistivity of this film was measured, it was 1 × 10 ⁻⁴ [Ω-cm], and it was confirmed that the film had excellent conductivity.

Example 2 As an acid anhydride component, 10.56 g (0.01 mol) of an acid-terminated silicone compound represented by the following formula:

[0032]

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ODPA 18.61 g (0.06 mol), 3,3 ', 4,4'
-Benzophenonetetracarboxylic dianhydride (BTD
A) 12.89 g (0.04 mol) and 58.92 g (0.07 mol) of a diaminosilicone compound represented by the following formula as a diamine component:

[0034]

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3.67 g (0.03 mol) of 2,4-diaminotoluene
Polyimide siloxane was obtained in the same manner as in Example 1 except that was used, and the imidation ratio was measured.
%Met.

This resin was dissolved in a one-to-one mixed solvent of diglyme and butyl cellosolve acetate (BCA).
Adjusted to 15%. Silver powder and nickel powder having an average particle size of 3 μm were added to the varnish in an amount of 300% by weight,
wt%, and uniformly dispersed using a three-roll mill to obtain a paste. This paste was cast on a Teflon plate whose surface was polished using an applicator, and after being heated at 120 ° C. for 5 hours to evaporate the solvent in a dryer, the film was peeled off from the Teflon substrate to form a 25 μm thick film. Created. Cut out a 3 mm x 3.5 mm square from this film, sandwich it between a copper lead frame and a 3 mm x 3.5 mm square silicon chip, and apply a 500 g load on a 250 ° C hot plate for 10 seconds did. When the shear strength was measured at room temperature, the silicon chip was broken at 10 kgf or more. Next, the same adhesive sample was placed on a hot plate at 260 ° C. for 10 seconds to measure the shear strength.
It was 0 kgf. No voids were observed on the adhesive film surface. When the volume resistivity of this film was measured, it was 1.5 × 10 ⁻⁴ [Ω-cm], and it was confirmed that the film was conductive.

(Example 3 and Comparative Examples 1 to 4) Except for the composition of the polyimide siloxane, the imidization time, the type of the conductive filler, and the amount added, the same procedure as in Example 1 was carried out, and the results shown in Table 1 were obtained. Was.

[0038]

[Table 1]

As shown in Examples 1 and 2 and Example 3 in Table 1, the acid-terminated silicone compound was used in proportion to the number of moles of the acid component.
0.09 to 0.33 in total, diaminosilicone
The compound is 0.4 or more in terms of the mole number of the amine component.
7 or less, and the molar ratio between the acid anhydride and the diamine is 0.8 to 1.2.
, And a polyimide filler having an imidization ratio of 80% or more is used.
250wt%, uniformly dispersed at 0wt%
Strong bonding strength can be obtained at a relatively low temperature of 5 ° C or less and a relatively low pressure of 5 kgf / cm ² or less under a short thermocompression bonding condition of 10 seconds or less, and 1 kgf or more even at a high temperature of 260 ° C. Had an adhesive strength of In addition, all the obtained adhesive films have a volume resistivity of 1 × 10 ⁻³ [Ω-c
m] or less, and had good conductivity.

On the other hand, acid-terminated silicone as in Comparative Example 1
If the compound is less than 0.09 in terms of moles of the acid component
Or more than 0.33, diaminosilicone compound
Is less than 0.4 in mole ratio of amine component
If it exceeds or exceeds 0.7, sufficient adhesive strength cannot be obtained under the thermocompression bonding conditions of 250 ° C., 5 kgf / cm ² and 10 seconds. As in Comparative Example 2, the amount of conductive filler added was 50
If the amount is less than wt%, sufficient conductivity cannot be obtained. Conversely, as in Comparative Example 3, when the added amount of the filler exceeded 900% by weight, the relative amount of the resin as the adhesive component decreased, and sufficient adhesive strength could not be obtained. As in Comparative Example 4, when the equivalent ratio of the reaction between the acid dianhydride and the diamine was extremely shifted to one side, the molecular weight of the resin did not increase, and sufficient adhesive strength could not be obtained. When the imidation ratio is less than 80% as in Comparative Example 5, voids are generated on the film surface after thermocompression bonding, and thus sufficient adhesive strength cannot be obtained. As described above, good results could not be obtained except under the conditions of the present invention.

[0041]

The film adhesive that can be thermocompression-bonded according to the present invention is excellent in adhesion to metals such as copper and silicon, and ceramics, and is sufficient not only at room temperature but also at a solder melting temperature of 260 ° C. It has excellent adhesive strength and excellent heat resistance. The adhesive layer had sufficient conductivity. In addition, it is possible to obtain a conductive film adhesive which is unconventional and is advantageous in terms of mass productivity which can be thermocompression-bonded at low temperature, low pressure and in a short time.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-234031 (JP, A) JP-A-62-48784 (JP, A) JP-A-59-64685 (JP, A) 501215 (JP, A)

Claims (1)

(57) [Claims] 1. A mole of an acid-terminated silicone compound represented by the formula (1) or (2) and other acid dianhydride components :
4,4'-oxydiphthalic dianhydride and / or 3,3 ', 4,4'-
Benzophenonetetracarboxylic dianhydride B mole
Acid component (however, 0.09 ≦ A / (A + B) ≦ 0.3
3) and 1,3-bis (3-amino) as C moles of the diaminosilicone compound represented by the formula (3) and other diamine components.
Phenoxy) benzene and / or 2,4-diaminotoluene
Amine component consisting of D moles (provided that 0.4 ≦ C / (C +
D) ≦ 0.7) , and ( A + B) / (C + D) is 0.8 to
A thermocompression-bondable conductive film adhesive comprising a polyimide siloxane which is reacted in the range of 1.2 and at least 80% of which is imidized, and 50 to 900% by weight of a conductive filler with respect to the polyimide siloxane. Embedded image Embedded image