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Nonaligned Solder Transfer Decal

IP.com Disclosure Number: IPCOM000086870D
Original Publication Date: 1976-Nov-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Herdzik, RJ: AUTHOR [+2]

Abstract

The present technique allows tinning of the pad areas, that is, locations where semiconductor chips are to be placed, of the multilayer ceramic (MLC) substrate ro enhance shelf-life, improve wettability, yet avoid the high cost of chip alignment.

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Nonaligned Solder Transfer Decal

The present technique allows tinning of the pad areas, that is, locations where semiconductor chips are to be placed, of the multilayer ceramic (MLC) substrate ro enhance shelf-life, improve wettability, yet avoid the high cost of chip alignment.

This method utilizes the chip decal system for transfer of solder, but the solder dots are deposited all over the surface of the chip, typically about 0.1 mil thick. The resulting appearance is similar to the dots in newsprint. The MLC substrate is fluxed in a conventional manner to accommodate a chip. Next, the decal chip is placed over the pad area of the substrate. Only coverage, not registration, is required. This package is then passed through a furnace at 350 degrees C to melt the 90Pb/ 10Sn solder pads on the decal chip. They then transfer to the pad areas of the substrate. The package is then given the conventional substrate clean process after chip-join. The decal chip falls off leaving the pad areas coated with 90Pb/10Sn solder ready to be conventionally chip-joined with the chip designed to complete the circuit.

An alternate to the use of chip decals is to use flexible substrate materials. Examples of useful flexible materials are anodized aluminum foil, polyimide film, MYLAR*, TEFLON* film or polycarbonate film. These film materials are coated with 0.3 to 0.5 mil of solder either with or without a mask depending on the complexity of the tinning to be performed. The solder on t...