JPH1030083A - Electrically insulating and heat-resistant adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive for lead frames, capable of directly carrying out screen printing onto a lead frame and curing and bonding. SOLUTION: The adhesive prints a composition comprising 100 pts.wt. epoxy resin and 5-40 pts.wt. elastomer having reactivity with epoxy group onto the lead part of a lead frame or prints the composition onto a releasable film in a prescribed form and carries out heat transfer of the printed composition to lead part of the lead frame and cures the composition to form a lead fixing frame. This adhesive is obtained by adding 3-20 pts.wt. imidazole, 3-60 pts.wt. fumed silica and 20-300 pts.wt. solvent to 100 pts.wt. epoxy resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame adhesive which can be directly screen-printed on a lead frame and cured and adhered.

[0002]

2. Description of the Related Art A lead frame has a base (tab) on which an IC element is mounted at a central portion, and a plurality of leads extending around the base toward the mounting base. The semiconductor device (IC package) includes an inner lead that is wire-bonded to a corresponding electrode on the mounted IC element and an outer lead that is an external terminal of the semiconductor device (IC package). Recently, the width of the lead of the lead frame has been reduced with the increase in the number of pins. for that reason,
When separating the lead frames, during transportation, and during wire bonding, the lead frame is distorted,
Usually, the leads are fixed with a flexible material between the leads because the leads are likely to cause damage due to fluttering or to increase defects during bonding due to fluctuations in the lead positions. Conventionally, for fixing between leads,
After punching a film of polyimide or the like coated with an adhesive into a predetermined shape using a mold, and thermocompression bonding the surface coated with the adhesive so as to connect a large number of leads of a lead frame,
Heat curing was performed, and the leads were fixed with a flexible polyimide film via an adhesive. However, in this method, the cost of the mold affects the cost, and most of the adhesive-backed film remaining after being punched into a predetermined shape is discarded unused, resulting in poor economic efficiency and effective use of resources. Was not planned.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and it is possible to print an adhesive directly on a necessary portion directly without using a polyimide film and to cure the adhesive to form a lead fixing frame. An object of the present invention is to provide a screen printing adhesive for fixing a lead frame, which has excellent heat resistance and insulation properties, and further has excellent impact resistance during transportation due to its excellent flexibility.

[0004]

Means for Solving the Problems After extensive research, the present inventor added a rubber component to a lead frame adhesive to directly print the adhesive without using a film such as a polyimide, and to obtain a cured product. It has been found that a lead fixing frame having high flexibility can be obtained, and the present invention has been completed.

That is, 100 parts by weight of an epoxy resin and an elastomer 5 having reactivity to an epoxy group
A composition containing ４０40 parts by weight is printed on a lead portion of a lead frame, or is printed in a predetermined shape on a release film, and is thermally transferred to the lead portion of the lead frame and cured to form a lead fixing frame. The present invention further provides an adhesive wherein 3 to 20 parts by weight of imidazole, 3 to 60 parts by weight of fumed silica, and 20 to 300 parts by weight of a solvent are added to 100 parts by weight of the epoxy resin in the adhesive. As the reactive elastomer, carboxy-modified acrylonitrile-butadiene rubber is preferable.

The epoxy resin used in the present invention includes 1
Any one may be used as long as it has two or more epoxy groups in the molecule, and one kind or two or more kinds are used without any particular limitation. Specifically, glycidyl ether type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, linear fat Examples include various polyfunctional epoxy resins such as an aromatic epoxy resin, an alicyclic epoxy resin, a heterocyclic epoxy resin, and a halogenated epoxy resin. Among the above epoxy resins, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolak type epoxy resin and cresol novolak type epoxy resin are preferably used.

As the reactive elastomer, one or two rubber components having a functional group reactive with an epoxy group can be used.
The rubber component is not particularly limited as long as it is a rubber component having at least one kind and having a functional group reactive with an epoxy group. Examples of the rubber component include carboxy-modified, aminated, epoxidized, and hydroxylated natural rubber (NR), Isoprene rubber (IR), butadiene rubber (BR), styrene / butadiene copolymer rubber (SBR), butyl rubber (IIR, Cl-IIR,
(Br-IIR), chloroprene rubber (CR), ethylene / propylene (diene monomer) copolymer rubber (EP
M, EPDM), acrylonitrile-butadiene rubber (NBR), chlorinated polyethylene rubber (CM), chlorosulfonated polyethylene rubber (CSM), acrylic rubber (ACM, ANM), epichlorohydrin rubber (CO,
ECO), ethylene / acrylate copolymer rubber (AEM), ethylene / vinyl acetate / acrylate terpolymer rubber (ER), hydrogenated acrylonitrile /
Rubbers such as butadiene copolymer rubber (HNBR) can be mentioned. Among the above rubber components, carboxy-modified acrylonitrile / butadiene rubber and the like are preferably used.

[0008] The amount of the elastomer to be compounded is 5 to 40 parts by weight, preferably 5 to 20 parts by weight. If the amount is less than 5 parts by weight, the adhesive of the present invention will not have sufficient flexibility, and if it exceeds 40 parts by weight, the insulating properties of the adhesive of the present invention will be reduced.

[0009] By adding a rubber component to the adhesive of the present invention, it is possible to impart appropriate viscosity as a printing ink and flexibility for impact resistance.

The curing agent used in the present invention may be any curing agent that can be used for general epoxy resins, and includes imidazoles,
Polyamide amines, aromatic amines and the like are exemplified,
Particularly preferred are imidazoles. In particular,
2-methylimidazole (2MZ), 2-ethyl-4-
Methylimidazole (2E4MZ), 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine / isocyanuric acid adduct (2MA-O
K), 2-undecyl imidazole (C ₁₁ Z), 2- phenylimidazole (2PZ), 1-benzyl-2-methylimidazole (1B2MZ), 1-cyanoethyl -
2-methylimidazole (2MZ-CN), 2-methylimidazolium isocyanurate (2MZ-OK),
2-phenylimidazolium isocyanurate (2P
Z-OK), 2,4-diamino-6- [2-methylimidazolyl- (1)]-ethyl-S-triazine (2MZ
-AZINE) and 2-phenyl-4-methylimidazole (2P4MZ), among which 2,4-diamino-6- [2'-methylimidazolyl- (1 ')]-
Ethyl-s-triazine / isocyanuric acid adduct is preferred in terms of reactivity and storage stability.

For example, 2MA-OK manufactured by Shikoku Chemicals Co., Ltd.
And other commercially available products.

The content of the curing agent is preferably 3 to 20 parts by weight, particularly preferably 4 to 8 parts by weight based on 100 parts by weight of the epoxy resin. If the content of the curing agent is less than 3 parts by weight,
If the curing agent is insufficient, and if it exceeds 20 parts by weight, the curing agent is excessive, and none of them exhibits sufficient physical properties.

Examples of the thixotropic agent used in the present invention include fatty acid amide waxes, fine powdered silica (fumed silica), and the like, and fumed silica is particularly preferred. When using fumed silica, the particle size is 7 to 100 n.
m, preferably 7 to 30 nm fine particles having few impurities. For example, Al ₂ O ₃ 0.05% by weight or less, Fe ₂ O ₃ 0.001% by weight or less, HCl 0.0
Those having less impurities of 5% by weight or less are preferable. Also,
It may be surface-treated with silicone oil.

As a specific example, A manufactured by Nippon Aerosil Co., Ltd.
Commercial products such as EROSIL 200 can be used.

The content of fumed silica is 3 to 60 parts by weight, especially 5 to 6 parts by weight, per 100 parts by weight of the epoxy resin.
It is preferably 0 parts by weight. When the content of the fumed silica is less than 3 parts by weight, the thixotropy is insufficient, and when it exceeds 60 parts by weight, the viscosity is too high and the handleability is poor. In particular, when a solvent is added, the thixotropic agent can be contained in the adhesive up to 10 to 60 parts by weight, and in that case, the resulting cured product can suppress shrinkage of the shape due to curing.

As the solvent used in the present invention, benzene,
Toluene, xylene, hexane, cyclohexane, acetone, methyl ethyl ketone, methyl isobutyl ketone,
Ethyl acetate, methylene chloride, chloroform, N, N-dimethylformamide, N, N-dimethylacetamide,
Preferable examples include ethylene glycol monomethyl ether, diethylene glycol dibutyl ether, N-methyl-2-pyrrolidone, methanol, and ethanol. Preferably, N-methyl-2-pyrrolidone is used.

The amount of the solvent to be added is 20 to 300 parts by weight, preferably 100 parts by weight, per 100 parts by weight of the epoxy resin.
２００200 parts by weight. If the amount is less than 20 parts by weight, the viscosity is too high, and if it exceeds 300 parts by weight, the viscosity is too low, and in any case, fluidity suitable as a printing ink cannot be obtained.

To the adhesive of the present invention, in addition to the above-mentioned essential components, additives such as a plasticizer, a curing assistant, an antioxidant, a filler and a coloring agent are added as long as the effects of the present invention are not impaired. You may.

The adhesive of the present invention can be produced by sufficiently kneading an epoxy resin, a reactive elastomer, a curing agent, a thixotropic agent, a solvent, and if necessary, other additives.

The adhesive of the present invention has a viscosity of 10,000 to 1,000,000 mPa ·
s, preferably having a viscosity of 50,000 to 500,000 mPa · s,
Further, since it has an appropriate thixotropic property, it can be used for printing as it is.

As a printing method, screen printing, transfer printing and the like are preferable, and screen printing is particularly preferable. This is because it is necessary to print the adhesive to a thickness of about 20 to 200 μm. Specific examples of screen printing include planar printing by mechanical printing, electrostatic screen printing, and printing using a rotary printing machine. Flat printing is performed by a cantilever frame method, a table slide method, a work slide method, a turret method, or the like.

The shape of the lead frame using the adhesive of the present invention is not particularly limited. For example, a lead frame 10 for a semiconductor device as shown in FIG. 1 is exemplified.
Here, the lead frame 10 is
Frame portion 14 having tabs and pad portion 18 having tabs 34
And a lead portion 16 having an inner lead 24, an outer lead 26, and a connecting portion 28,
Usually, it is formed by processing a thin metal plate by pressing or etching.

A rectangular tab 34 is disposed at the center of the outer frame portion 14. The four corners of the tab 34 are connected and supported by the tip of a tab lead 32, and a pad portion 18 for disposing a semiconductor element is provided. Is formed.

An inner lead 24, an outer lead 26 and a connecting portion 28 are provided between the pad portion 18 and the outer frame portion 14.
Are formed. The lead portion 16 has a plurality of inner leads 24 radially extending in the direction of the outer frame portion 14 around the tab 34 in order to connect the lead frame 10 and the semiconductor element arranged on the pad portion 18. It is connected to the lead 26. The inner edges of the outer leads 26 are connected to each other by a connecting portion 28, and a plurality of outer leads 26 extend from the connecting portion 28 toward the outer frame 14 in a direction perpendicular to each side of the tab 34. Are located.

The adhesive is printed directly on the inner leads 24 of the lead frame 10 by the printing method described above. Copper, 42 alloy alloy,
Copper alloys, Kovar, Fe-Ni alloys and the like can be used.

Although the printing may be performed directly on the lead frame, the adhesive of the present invention is first printed on a release film,
Adhere the semi-cured adhesive on the lead frame,
After the thermal transfer, only the film may be peeled off.

In this way, the adhesive of the present invention is printed on the inner lead as shown in FIG. 1, and the thickness after curing is preferably printed to 20 to 100 μm. Printing the adhesive to this thickness is appropriate to maintain the lead-to-lead spacing. The shape of the lead fixing frame formed by curing the printed adhesive changes in accordance with the lead frame to be adhered to the adhesive.

The printed adhesive can be cured by heating. The heating temperature is preferably from 100 to 250C.

The screen printing adhesive for fixing a lead frame of the present invention is also useful for bonding between metal plates other than the lead frame. For example, it can be suitably used for bonding electronic components such as chips, substrates, and heat sinks.

As described above, the adhesive of the present invention can be directly applied by screen printing, so that the amount of the adhesive used can be reduced. In addition, since the adhesive itself has sufficient flexibility, polyimide can be used. There is no need to use such films. In addition, it has excellent printability, heat resistance, and insulation properties, and has excellent impact resistance due to its excellent flexibility. It also prevents flapping of leads during transportation and wire bonding, and generates defects during bonding. Can be suppressed.

[0031]

EXAMPLES The present invention will be described below in detail with reference to examples, but the scope of the present invention is not limited by these examples. (Examples 1 to 3 and Comparative Examples 1 to 4) The components shown in Table 1 below were sufficiently kneaded to obtain an adhesive. Physical properties of the obtained adhesive were measured according to the following criteria. The results are shown in Table 1 below.

Viscosity: 0.5 at 25 ° C. using an E-type viscometer.
The viscosity when rotating at rpm was measured. Thixotropic; ratio of viscosity when rotated at 0.5 ° C. and 5 rpm at 25 ° C. (viscosity when rotated at 0.5 rpm / 5 rpm)
(viscosity at m rotations). Flexibility: After applying each adhesive to the polyimide film so that the thickness when dried becomes 20 μm, curing was performed at 200 ° C. for 10 minutes, and the obtained sample was visually evaluated for the degree of bending when twisted. Linear expansion coefficient (TMA): Measured according to JIS K 7197. Surface resistance: After applying each adhesive and removing the solvent, 16
A sample plate having a thickness of 2 mm was formed by press molding at 0 ° C., and the surface resistance was measured under two kinds of conditions. : Measured after leaving for 96 hours in an atmosphere of 20 ° C. and a relative humidity of 60%. : After standing under the conditions of:
Measured after standing for 96 hours in a% atmosphere. Volume resistivity: Measured in the same manner as surface resistivity.

[0033]

[Table 1]

The footnotes in the figure are as follows. 1) Epoxy resin: N865 (manufactured by Dainippon Ink and Chemicals, epoxy equivalent: 195 to 215) 2) Epoxy resin: EPICLON1050 (manufactured by Dainippon Ink and Chemicals, epoxy equivalent: 450 to 500) 3) Epoxy resin: 830 LVP (large) 4) Epoxy resin: 152 (Epoxy equivalent: 172-179, manufactured by Yuka Shell Co.) 5) Carboxy-modified acrylonitrile-butadiene rubber: CTBN 1300 × 13 (BF Goodrich) 6) Acrylonitrile butadiene rubber: Nipol
1041 (manufactured by Zeon Corporation) 7) Phenoxy resin: YP-50 (manufactured by Toto Kasei Co., Ltd.) 8) Fumed silica: AEROSIL 200 (manufactured by Nippon Aerosil Co., Ltd., average primary particle diameter: 12 nm) 9) Imidazole: 2MA-OK ( (Shikoku Chemicals)

From the results shown in Table 1, the adhesive of the present invention is excellent in flexibility by compounding a rubber component, and does not impair insulation by setting the compounding amount of the rubber component in the range of the present invention. It became clear.

[0036]

The adhesive of the present invention can be printed only on a required portion on a lead frame or a release film, so that the amount of the adhesive used is small, and the adhesive itself has sufficient flexibility. Therefore, a flexible film such as a polyimide film is not required, which can contribute to cost reduction. In addition, it has excellent printability, heat resistance and insulation properties, and has excellent shock absorption due to its excellent flexibility. It also prevents lead flapping during transportation and wire bonding, and generates defects during bonding. Can be suppressed.

[Brief description of the drawings]

FIG. 1 shows the adhesive of the present invention printed on a lead frame.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Lead frame 14 Outer frame part 16 Lead part 18 Pad part 20 Adhesive 22 Pilot hole 24 Inner lead 26 Outer lead 28 Connecting part 32 Tab lead 34 Tab

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C08K 3/36 NKX C08K 3/36 NKX C08L 63/00 NJQ C08L 63/00 NJQ

Claims (6)

[Claims] An adhesive for forming a lead fixing frame by printing a composition containing 100 parts by weight of an epoxy resin and 5 to 40 parts by weight of an elastomer having reactivity to an epoxy group on a lead portion of a lead frame. 2. A composition containing 100 parts by weight of an epoxy resin and 5 to 40 parts by weight of an elastomer reactive to an epoxy group is printed in a predetermined shape on a release film, and is thermally transferred to a lead portion of a lead frame. Adhesive that cures and cures to form the lead fixing frame. 3. The method according to claim 1, wherein 100 parts by weight of the epoxy resin is
The adhesive according to claim 1, wherein 3 to 20 parts by weight of imidazole is added. 4. The method according to claim 1, wherein 100 parts by weight of the epoxy resin is
The adhesive according to any one of claims 1 to 3, wherein 3 to 60 parts by weight of fumed silica is added. 5. The adhesive according to claim 1, wherein a solvent is added in an amount of 20 to 300 parts by weight based on 100 parts by weight of the epoxy resin. 6. The reactive elastomer is a carboxy-modified acrylonitrile-butadiene rubber.
The adhesive according to any one of the above.