WATER SOLUBLE PRESSURE SENSITIVE ADHESIVE FOR FINE SOLDER BALL REPLACEMENT

摘要

[PROBLEMS] A solder ball mounter is used in mounting solder balls on a printed board. Fine solder balls having a particle diameter of not more than 0.2 mm have a small self-weight and, thus, upon the generation of static electricity, necessary solder balls are also disadvantageously dropped by air spraying or impact. Further, solder balls, which have been once dropped, have a small self-weight and are disadvantageously again deposited by generated static electricity to an adsorption head. [MEANS FOR SOLVING PROBLEMS] A process is used in which solder balls are placed in a bulk form on a mask such as a metal mask and are scraped out with a squeegee such as polyurethane to drop the solder balls through holes of the mask opened at the same position as an electrode in a module substrate to fix the balls with a pressure sensitive adhesive coated onto the module substrate, whereby redeposition of the solder balls onto the mask is avoided. The pressure sensitive adhesive used in this process has a molecular weight of not less than 200, a viscosity of not less than 5000 mPa s, and an adhesive strength of 50 to 300 gf. Suitable pressure sensitive adhesives are pressure sensitive adhesive materials selected from highly viscous liquid materials, i.e., ethylene oxide-polyoxyethylene copolymer nonionic active agents, ethylene oxide-propylene oxide condensation added ethylenediamines, or water soluble urethane oligomers, or systems produced by mixing water soluble resins, i.e., PVA ethylene oxide adducts, ether polymers, or vinylpyrrolidone-vinyl acetate copolymers, with a liquid material.