JP6632618B2 - Conductive paste for mounting - Google Patents

Description

  The present invention relates to a conductive paste for mounting, and more particularly, to a conductive paste for mounting suitable for a flip chip mounting method.

  As electronic devices have become lighter and thinner, there has been a demand for smaller and thinner chips. However, when chips are made thinner, there is a problem in that chips are deformed by heat during mounting. Therefore, there is a demand for a technology that enables mounting at a low temperature.

  As a technology enabling mounting at a low temperature, for example, a flip chip mounting method using a microcapsule in which a conductive filler is coated with an insulating material as disclosed in Patent Document 1 is disclosed. The flip-chip mounting method is a mounting technique in which a small amount of conductive paste applied on a transfer table is adhered to a bump (electrode portion) of a semiconductor element by transfer and fixed to a printed circuit board. However, the flip chip mounting method disclosed in Patent Document 1 is a method in which a resin is attached to bumps by dipping, and then microcapsules are attached by dipping, and has a problem that the operation is complicated and the efficiency is low. Therefore, a technique for efficiently attaching a conductive paste to bumps is required.

  Further, with the miniaturization of chips, the size of bumps and the pitch between bumps have been further miniaturized. Therefore, when transferring the conductive paste by dipping, it is difficult to transfer an appropriate amount of the conductive paste for mounting on the fine bumps of the miniaturized chip, and the reliability of the bonding portion is reduced. Is required.

JP-A-9-246326

  The present invention has been made in view of the above, is a mounting conductive paste that can be mounted at a low temperature, and that can ensure the reliability of the junction between the miniaturized chip and the substrate, In particular, it is an object of the present invention to provide a mounting conductive paste suitable for a flip chip mounting method.

The conductive paste for mounting according to the present invention, in order to solve the above problems, 10 to 50 parts by mass of a solid epoxy resin, 10 to 40 parts by mass of an acrylate monomer, and 100 parts by mass of a resin component whose balance is a liquid epoxy resin. to, 0.5 to 30 parts by weight of the curing agent, a conductive filler in a proportion of 400 to 1200 parts by weight, the solid epoxy resin, bisphenol a type epoxy resin, trisphenolmethane type epoxy resin, and phenol novolac One or two or more types selected from the group consisting of type epoxy resins .

As the liquid-like epoxy resin can be used bisphenol A type epoxy resin, bisphenol F type epoxy resin, glycidyl amine-based epoxy resin, and one or more selected from the group consisting of glycidyl ether type epoxy resin.

  As the curing agent, one or more selected from the group consisting of imidazole, imidazole derivatives, and modified amines can be used.

  As the conductive filler, one or more selected from the group consisting of gold, silver, and copper can be used.

  ADVANTAGE OF THE INVENTION According to the conductive paste for mounting of this invention, mounting at low temperature is possible and it can improve the adhesiveness of the joining part of recent finer chip and board | substrate, conductivity, and its reliability. it can. Therefore, it is possible to cope with further downsizing and thinning of the chip.

It is a schematic cross section showing the state where the conductive paste for mounting was transferred to the bump of the chip by dipping. It is an enlarged view of the printed wiring board showing the conductivity evaluation pattern.

  Hereinafter, embodiments of the present invention will be described more specifically.

  The conductive paste for mounting according to the present embodiment contains 10 to 50 parts by mass of a solid epoxy resin, 10 to 40 parts by mass of an acrylate monomer, and 100 parts by mass of a resin component whose balance is a liquid epoxy resin. 0.5 to 30 parts by mass and a conductive filler in a ratio of 400 to 1200 parts by mass.

  Here, the “solid epoxy resin” refers to an epoxy resin that is solid at normal temperature (25 ° C.). The solid epoxy resin contains an epoxy group in the molecule, and is not particularly limited as long as it is solid at ordinary temperature. Specific examples thereof include a bisphenol A epoxy resin, a trisphenolmethane epoxy resin, and a phenol novolak epoxy resin. Epoxy resins and the like can be mentioned. One type of solid epoxy resin can be used alone, or two or more types can be blended and used.

  The compounding amount of the solid epoxy resin is 10 to 50 parts by mass, preferably 15 to 40 parts by mass, and more preferably 20 to 40 parts by mass. When the amount is 10 parts by mass or more, sufficient adhesiveness and conductivity between the chip and the substrate can be obtained. When the amount is 50 parts by mass or less, the viscosity of the conductive paste does not become too high, and the chip can be mounted without being in close contact with the transfer table during transfer.

  As the acrylate monomer, those having one or more reactive groups represented by the following structural formula (I) in the molecule can be used.

式（Ｉ）中、ＲはＨ又はアルキル基を示し、アルキル基の炭素数は特に限定されないが、通常は１〜３個である。

In the formula (I), R represents H or an alkyl group, and the number of carbon atoms of the alkyl group is not particularly limited, but is usually 1 to 3.

  Specific examples of the acrylate monomer include, but are not particularly limited to, isoamyl acrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, bisphenol A diglycidyl ether acrylic acid adduct, ethylene glycol dimethacrylate, -Hydroxy-3-acryloyloxypropyl methacrylate, diethylene glycol dimethacrylate and the like.

  In addition, two or more acrylate monomers can be used in combination.

  The total amount of the acrylate monomer is 10 to 40 parts by mass, preferably 15 to 35 parts by mass, more preferably 20 to 30 parts by mass.

  Next, “liquid epoxy resin” refers to an epoxy resin that is liquid at normal temperature (25 ° C.). The liquid epoxy resin contains an epoxy group in the molecule and is not particularly limited as long as it is liquid at normal temperature. Specific examples thereof include bisphenol A epoxy resin, bisphenol F epoxy resin, and glycidylamine epoxy resin. Resins and glycidyl ether epoxy resins. One type of liquid epoxy resin can be used alone, or two or more types can be blended and used.

  The compounding amount of the liquid epoxy resin is determined so that the resin component is 100 parts by mass in consideration of the compounding amounts of the solid epoxy resin and the acrylate monomer.

  The curing agent used in the present invention is not particularly limited, but imidazole-based curing agents such as imidazole and imidazole derivatives, or modified amines are preferably used. Specific examples of the imidazole-based curing agent include imidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecyl And imidazole and 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine. Specific examples of the modified amine include epoxy adducts of various polyamines, Mannich reactants, Michael reactants, thiourea reactants, and the like.

  The compounding amount of the curing agent is 0.5 to 30 parts by mass, preferably 1 to 20 parts by mass, more preferably 3 to 15 parts by mass with respect to 100 parts by mass of the resin component. When the amount is 0.5 parts by mass or more, sufficient curing for obtaining adhesiveness and conductivity can be obtained, and when the amount is 30 parts by mass or less, a pot life can be ensured within a range that does not impair workability.

  The conductive filler used in the present invention is preferably one kind or two or more kinds selected from gold, silver, and copper, and the shape and the production method are not limited. In addition to metal powders composed of a single metal, metal powders composed of two or more alloys, and powders obtained by coating these metal powders with other metals can be used. Preferred examples include silver-coated copper powder. Is mentioned. The particle size of the conductive filler is not particularly limited, but the average particle size is preferably 0.5 μm to 20 μm.

  The amount of the conductive filler is 400 to 1200 parts by mass, preferably 500 to 1000 parts by mass, and more preferably 600 to 800 parts by mass with respect to 100 parts by mass of the resin component. When it is 400 parts by mass or more, sufficient conductivity is obtained. When the amount is less than 1200 parts by mass, the viscosity does not become too high, and an appropriate amount of the conductive paste for mounting can be transferred at the time of transfer, and the chip can be mounted without being in close contact with the transfer table at the time of transfer. Is possible.

  The conductive paste for mounting of the present invention can be obtained by blending the above-mentioned components in predetermined amounts and mixing them sufficiently. In addition, additives that have been conventionally added to the same type of conductive paste can be added to the mounting conductive paste of the present invention within a range not departing from the object of the present invention.

  The conductive paste for mounting obtained as described above can be suitably used for a flip chip mounting method, and since it has a solid epoxy resin, the viscosity at a low temperature is high, and the mounting at a low temperature is possible. And it can respond to thinning. That is, in the flip chip mounting method, when the conductive paste for mounting is transferred to the bump of the chip by dipping, the conductive paste does not adhere to the transfer table, and is suitable for mounting on the fine bumps of the miniaturized chip. An appropriate amount of the conductive paste for mounting can be transferred. Therefore, it is possible to improve the adhesiveness and conductivity of the fine joint between the chip and the substrate and the reliability thereof.

  Examples of the present invention will be described below, but the present invention is not limited by the following examples. In addition, the compounding amount shown below is based on mass unless otherwise specified.

  According to the composition shown in Table 1 below, a solid epoxy resin, a liquid epoxy resin, an acrylate monomer, a curing agent, and a silver-coated copper powder were mixed to prepare a conductive paste for mounting.

  The obtained conductive paste for mounting is thinly applied on a transfer table (not shown), and the bumps 2 of the chip 1 are dipped into the conductive paste. As shown in FIG. Transferred to The chip 1 was mounted on a substrate, heated at 80 ° C. for 60 minutes, further heated at 160 ° C. for 60 minutes, and cured to obtain a mounting substrate.

  The details of each component in Table 1 and the details of the substrate, chip, and flip chip bonder used for evaluation are as follows.

・ Solid epoxy resin: Mitsubishi Chemical Corporation “JER157S70”
-Liquid epoxy resin: blend of "EP-4901" (80% by weight) manufactured by ADEKA Corporation and "ED502" (20% by weight) manufactured by ADEKA Corporation-Acrylate monomer: 2-hydroxy-3-acryloyloxypropyl methacrylate Curing agent A (imidazole-based curing agent): 2-ethylimidazole / curing agent B (modified amine): "Fujicure FXR-1030" manufactured by T & K TOKA Corporation
・ Silver coated copper powder: average particle size 3μm, spherical

-Substrate: "WALTS-KIT 01A150P-10" manufactured by Waltz Co., Ltd.
Substrate size: 30.0 mm x 30.0 mm x (0.8 to 1.0 mmt)
Number of pads: 61 × 61 = 3721
Pad pitch: 0.15mm
Pad size: φ0.12mm (SR opening φ0.08mm)
・ Chip: "WALTS-TEG FC150JY (P1)" manufactured by Waltz Co., Ltd.
Number of bumps: 61 × 61 = 3721
Bump pitch: 0.15mm
Bump size: φ0.085mm
Bump material: Sn / Ag3 / Cu0.5
Wafer thickness: 500μm ± 25μm
・ Flip chip bonder: “FCB3 flip chip bonder” manufactured by Panasonic Corporation
Paste transfer conditions: Number of times: once, load: 200N
Mounting condition: Contact load: 400N

  With respect to the obtained mounting board, conductivity evaluation, push strength (shear stress), and change in viscosity after 24 hours were measured by the following methods.

Conductivity evaluation: As shown in FIG. 2, the resistance value after mounting by 240 connected daisy patterns A to E provided at the four corners and the center of the printed wiring board 4 was measured at room temperature (25 ° C.) by a tester (Hioki Electric). The measurement and evaluation were performed using HIOKI3540 HiTESTER (manufactured by Hitachi, Ltd.).

・ Push strength: The chip after mounting and curing is pushed in a horizontal direction (lateral direction) at 20 mm / min using a metal jig, and the maximum load until the chip comes off at room temperature (25 ° C.) It measured using SHIMADZU AUTOGRAPH AGS-X.

Viscosity change after 24 hours: Using a BH type viscometer, the viscosity change after 24 hours at normal temperature (25 ° C.) was determined for the viscosity at rotor No. 7 and 10 rpm.
It should be noted that those excellent in both conductivity and adhesiveness measured by the above-mentioned measuring method can be evaluated as those in which the reliability of the joint between the chip and the substrate could be secured.

  The results are as shown in Table 1. The solid epoxy resin was 10 to 50 parts by mass, the acrylate monomer was 10 to 40 parts by mass, and the balance was 100 parts by mass of the liquid epoxy resin. In Examples 1 to 6 which are conductive pastes for mounting containing a conductive filler at a ratio of 400 to 1200 parts by mass, a sufficient adhesiveness, conductivity and reliability thereof were obtained.

  On the other hand, in Comparative Example 1 in which the solid epoxy resin was less than 10 parts by mass, sufficient adhesion and conductivity between the substrate and the chip could not be obtained, and in Comparative Example 2 in which the solid epoxy resin was more than 50 parts by mass, Since the viscosity of the conductive paste for use was high, the chip adhered to the transfer table during transfer and could not be mounted. In Comparative Example 3 in which the curing agent was less than 0.5 part by mass with respect to 100 parts by mass of the resin component, sufficient adhesion and conductivity were not obtained due to insufficient curing, and Comparative Example 3 in which the curing agent was more than 30 parts by mass. In Nos. 4 and 5, the pot life was shortened, and the workability was impaired. Further, in Comparative Example 6 in which the conductive filler was less than 400 parts by mass with respect to 100 parts by mass of the resin component, sufficient conductivity was not obtained, and in Comparative Example 7 in which the conductive filler was more than 1200 parts by mass, the conductive paste for mounting was Due to its high viscosity, an appropriate amount of the conductive paste for mounting could not be transferred at the time of transfer, and the chip adhered to the transfer table at the time of transfer and could not be mounted.

1 ... Chip 2 ... Solder bump 3 ... Conductive paste 4 for mounting ... Printed wiring board A ... 240 connection daisy pattern Upper left B ... 240 connection daisy pattern Upper right C ... 240 connection daisy pattern Lower left D ... 240 Connected daisy pattern Lower right E ... Center of 240 connected daisy patterns

Claims (4)

10 to 50 parts by mass of the solid epoxy resin, 10 to 40 parts by mass of the acrylate monomer, and the balance is 100 parts by mass of the resin component which is a liquid epoxy resin.
0.5 to 30 parts by mass of the curing agent, 400 to 1200 parts by mass of the conductive filler ,
Wherein the solid epoxy resin is one or more selected from the group consisting of a bisphenol A epoxy resin, a trisphenol methane epoxy resin, and a phenol novolak epoxy resin, paste. The liquid epoxy resin is one or more selected from the group consisting of a bisphenol A epoxy resin, a bisphenol F epoxy resin, a glycidylamine epoxy resin, and a glycidyl ether epoxy resin. The conductive paste for mounting according to claim 1 . Wherein the curing agent, imidazole, imidazole derivatives, and is characterized in that at least one selected from the group consisting of modified amine, mounting a conductive paste according to claim 1 or 2. The conductive filler according to any one of claims 1 to 3 , wherein the conductive filler is at least one selected from the group consisting of gold, silver, and copper. paste.

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