JP2000212531A - Conductive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a conductive adhesive which can easily be peeled, can give high reliability to bonded portions of the and is circuit useful for chip parts, etc., and even whose residues can easily be removed with an ordinary solvent, by compounding an epoxy resin, a curing agent, conductive particles and a saturated copolyester resin as essential components. SOLUTION: This conductive adhesive comprises (A) an epoxy resin such as a phenol type epoxy resin preferably in an amount of 100 pts.wt., (B) a curing agent such as an aliphatic polyamine preferably in an amount of 0.1-30 pts.wt., (C) conductive particles such as silver (alloy) particles preferably in an amount of 30-2,000 pts.wt., and (D) a saturated copolyester resin, for example, obtained by the polycondensation of a dicarboxylic acid component such as terephthalic acid or adipic acid with a diol component such as ethylene glycol or neopentyl glycol preferably in an amount of 30-200 pts.wt., as essential components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive adhesive suitable for use in surface mounting, that is, for bonding chip parts, bonding package ICs, and attaching bare chips. Conductive adhesives are required for high-density mounting, harmful substance regulations, lowering of mounting temperature, weight reduction, etc.
Its interest is increasing.

[0002]

2. Description of the Related Art As a conductive adhesive used for a surface mounting application, a material in which conductive particles are mixed in an epoxy-based thermosetting substance has been well known. In addition, a material in which conductive particles are blended with a styrene-based or urethane-based thermoplastic material is also used.

[0003] In connection with these adhesives, if the electrical connection is poor or the electronic components or circuits become defective after the connection, the electronic components must be replaced, but the electronic components must be replaced with a thermosetting conductive adhesive. The object does not become soft even when heated, but rather hardens, which makes it extremely difficult to remove the electronic component. Normally, the electronic part is forcibly peeled off, the remaining adhesive is removed with a solvent or the like, and then a good product is joined again with a conductive adhesive. Particularly in a mass production process, such difficulty in repair is a serious negative factor in terms of productivity. In the case of a defective solder joint, the solder can be easily removed by heating and sucking, and the component can be removed and replaced.

[0004]

SUMMARY OF THE INVENTION
In other words, when considering heat resistance and moisture resistance, epoxy-based curable adhesives are preferably used because of their excellent properties, but once cured, the adhesive is not easily peeled off even if heated. To remove the residue after peeling,
A method using a special agent such as methylene chloride mixed with an acid is required. However, acids and halides cause corrosion and the like at the rejoined portion, and are not preferable from the viewpoint of connection reliability. On the other hand, conductive adhesives using thermoplastics are easy to peel off by heating and easy to repair with general-purpose solvents, but their heat resistance, that is, reliability as an adhesive, is an epoxy-based thermosetting material. Are inferior to those using. For this reason, repair is difficult, but conductive adhesives based on epoxy-based thermosetting resins have often been used. In view of such a situation, a conductive adhesive which has high reliability of the circuit connection portion, is easily peeled off in the case of repair, and can easily remove the residue with a general-purpose solvent, and is easily repaired has been desired in the past. Was.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, epoxy resin,
By adding a saturated copolyester resin to the conductive adhesive containing the hardener and conductive particles as essential components, it is possible to maintain the connection reliability of the circuit connection part and to easily make the circuit joint part in case of failure. And found that the remaining adhesive could be easily removed, and completed the present invention on the basis of the knowledge. That is, the present invention relates to a conductive adhesive containing an epoxy resin, a curing agent, conductive particles, and a saturated copolymerized polyester resin as essential components.

The saturated copolymerized polyester resin used in the present invention is one kind of linear saturated polyester formed by condensation polymerization of a dicarboxylic acid component and a diol component, and contains at least another dicarboxylic acid component or another diol component. It is obtained by one kind of co-condensation polymerization. Where "saturated"
Means that the aliphatic group consists of a saturated bond. Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, and saturated aliphatic dicarboxylic acids such as adipic acid and sebacic acid. Examples of the diol component include ethylene glycol, 1,4-butanediol, diethylene glycol, neopentyl glycol, and the like. Resins of various properties have been produced by these various combinations and changes in the compounding amount.
Industrially, for example, “Elitel” of Unitika Ltd. is commercially available. Generally, their softening points are between 60 and 170C. When placed in an atmosphere above the softening point, it rapidly changes to a liquid. Also easily soluble in organic solvents,
Dissolves well in general-purpose solvents such as methyl ethyl ketone, ethyl acetate, cellosolve acetate, and cyclohexane. It is also compatible with epoxy resins. It can be said that such properties impart repairability to the cured epoxy resin.

The epoxy resin used in the present invention is a compound having one or more epoxy groups in one molecule, and any commonly known epoxy resin can be applied.
For example, monoglycidyl ethers such as phenylglycidyl ether, epichlorohydrin and bisphenol A
Polyglycidyl ethers of polyhydric phenols such as phenol-type epoxy resins derived from phenol or bisphenol F, epichlorohydrin and phenol novolak resins, and epoxy novolak resins derived from cresol novolak resins are representative examples. In addition, there are polyglycidyl esters of polycarboxylic acids, polyglycidyl ethers of polyhydric alcohols, polyglycidyl compounds of polyamines, and other linear aliphatic epoxides, and these are used alone or in combination of two or more.

[0008] The curing agent of the present invention is not particularly limited as long as it is a usual curing agent for epoxy resin which is cured by reacting with epoxy resin. Aliphatic polyamine, polyaminoamide, aromatic diamine, alicyclic diamine, heterocyclic diamine, 3
There are amine compounds such as secondary amines and imidazoles, acid anhydride compounds, phenols, phenolic resins, mercaptan compounds, hydrazide compounds, dicyandiamide, Lewis acid complex compounds and the like. More specifically, for example,
Diethylenetriamine, triethylenetetramine, meta-xylenediamine, dimer acid polyamide, 4,4'-
Diaminodiphenyl ether, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylmethane, dicyandiamide, 1,6-diaminonaphthalene,
4,4'-diaminobenzophenone, metaphenylenediamine, diaminobenzoic acid, N, N-dimethylpiperazine, tris (dimethylaminomethyl) phenol, 2-
Acid adducts of methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, imidazole compounds and hydroxybenzoic acid,
Phthalic anhydride, tetrahydromethyl phthalic anhydride, bisphenol A, bisphenol F, 4,4'-dihydroxybiphenyl, 3,3 ', 5,5'-tetramethyl-
4,4′-dihydroxybiphenyl, phenol novolak resin, cresol novolak resin, polysulfide, adipic hydrazide, isophthalic hydrazide,
Examples include boron trifluoride / ethylamine complex.
In addition, these curing agents include those in the form of microcapsules covered with a coating of a polymer substance or a metal, and are called latent curing agents. Latent curing agents are used to achieve both long-term storage properties and rapid curing properties. In the present invention, an appropriate one of the aforementioned curing agents is used alone or in combination of two or more.

The conductive particles used in the present invention include:
Conductive metals such as silver, silver alloys, gold, copper, copper alloys, nickel, nickel alloys, tin, tin alloys, and even alumina,
Examples thereof include those in which the surface of an inorganic insulator such as glass or an organic polymer compound such as polyethylene or polystyrene is coated with a conductive substance, carbon, graphite, and the like. The shape of these conductive particles is arbitrary,
It is used by selecting from a spherical shape, a flake shape, a fibrous shape, and the like as necessary.

[0010] To the conductive adhesive of the present invention, a curing accelerator, a solvent, a viscosity modifier, a flexibility-imparting agent, a filler, a coloring agent, and the like may be added as necessary. For example, triphenylphosphine, bis (diphenylphosphino) methane and the like as a curing accelerator, toluene, benzyl alcohol, diethylene glycol monoethylhexyl ether as a solvent, and a hardened castor oil and dibenzylidene sorbitol as a viscosity modifier. Examples of the flexibility-imparting agent include resins, polymer compounds, plasticizers and the like, examples of the filler include aluminum oxide and calcium carbonate, and examples of the colorants include titanium dioxide and carbon black.

The amount of the curing agent relative to the epoxy resin, which is an essential component in the present invention, is an amount sufficient to polymerize the epoxy resin, and is usually 0.1 to 30 parts by weight per 100 parts by weight of the epoxy resin. desirable. The amount of the conductive particles with respect to the epoxy resin is 100
20 to 3000 parts by weight, especially 30 to 20 parts by weight
00 parts by weight is desirable. Further, the amount of the saturated copolymerized polyester resin based on the epoxy resin is preferably 10 to 500 parts by weight, particularly preferably 30 to 200 parts by weight based on 100 parts by weight of the epoxy resin.

The method of preparing the conductive adhesive of the present invention includes:
First, a saturated copolyester resin is added to the epoxy resin, and then heated and dissolved, and then cooled.
Further, if necessary, other additives may be added, preferably kneaded with a three-roll mill, and then conductive particles may be added and kneaded using a three-roll mill or a kneader. Legal may be adopted.

[0013]

EXAMPLES Examples of the present invention will be specifically described below, but these examples do not limit the present invention.

Examples 1 to 5 and Comparative Examples 1 and 2 The compositions shown in Table 1 were kneaded with a composition ratio shown in Table 2 using a three-roll mixer to prepare a conductive adhesive.
The obtained conductive adhesive was cured by the following method, and the physical properties after curing were measured.

(Fixing Strength) A conductive adhesive is printed on a land corresponding to a 2125 chip capacitor through a 150 μm thick metal mask. 2125 on top of this
The chip is mounted by a chip mounter. Then 15
Place in a hot air oven at 0 ° C and heat and cure for 15 minutes. A shear force was applied to the chip at a speed of 23 mm / min, the load at the time of shear failure was read, and the value was taken as the bond strength.

(Specific Resistance) A conductive mold is filled in a frame mold and cured at 150 ° C. for 15 minutes under a pressure of 100 kg / cm to form a plate (10 × 70 × 0.3 mm). Make test specimens. Electrodes are attached to both ends (the distance between the electrodes is 50 mm). Measure the electrical resistance between the electrodes,
Calculate the specific resistance.

(Repairability: chip peeling, residue removal) The chip (2125) is fixed on a circuit land with a conductive adhesive and cured (150 ° C., 30 minutes). The chip peelability was examined using a spot air type SMD rework apparatus. A spot-like hot air (220 to 250 ° C.) is sprayed to the joint, and an operation of removing the chip with vacuum tweezers is performed. Further, an operation of removing the residue after removal with a cotton swab containing methyl ethyl ketone is performed.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

According to the present invention, it is possible to join circuits with excellent connection reliability, and when a failure occurs at the circuit joint, the components are easily peeled off and the residue is easily removed with a general-purpose solvent. An extremely practical conductive adhesive that can be repaired is provided.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J040 EB052 EC021 EC022 EC061 EC062 EC071 EC072 EC091 EC092 EC121 EC122 EC261 EC262 ED041 ED042 ED051 ED052 EG022 HA026 HA036 HA066 HA076 HB35 HB47 HC02 HC08 HC10 HC15 HC03 HC20 KA32 NA20 PA40 PA42

Claims (1)

[Claims] 1. A conductive adhesive comprising an epoxy resin, a curing agent, conductive particles and a saturated copolymerized polyester resin as essential components.