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Chip Salvage/Rework Procedure

IP.com Disclosure Number: IPCOM000083880D
Original Publication Date: 1975-Aug-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Herdzik, RJ: AUTHOR [+3]

Abstract

Semiconductor chips may be salvaged from defective substrates by removing the chips while the solder, which connects the chip to the substrate, is molten. This will insure minimal damage to both chip and substrate for rework/repair, and eliminate the type of damage induced by mechanically pulling, tearing or shearing chips off the substrates.

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Chip Salvage/Rework Procedure

Semiconductor chips may be salvaged from defective substrates by removing the chips while the solder, which connects the chip to the substrate, is molten. This will insure minimal damage to both chip and substrate for rework/repair, and eliminate the type of damage induced by mechanically pulling, tearing or shearing chips off the substrates.

Removing the chip while the solder is molten can be accomplished by modifying existing procedures for "stretching" the solder joints, to insure sufficient "lift" so that there is separation. One technique readily adaptable to automation and applicable to all currently available substrate types is the bridge-flux technique.

A drop of liquid 1, such as flux, which will wet the silicon chip surface, is placed upon the chip 2 as shown in Fig. 1. A bridge 3 is placed over the chip 2 so that it also is wetted by the flux 1. The structure is placed in a furnace and the temperature is increased until the solder 4, which connects the chip 2 to the substrate 5, is liquid. The solder joint is stretched to the breaking point by the evaporation of the liquid 1, which draws the chip 2 to the bridge 3. The result of the process is shown in Fig. 2.

A second technique would be to insert shims 6 under two sides of the chip, as shown in Fig. 3, The shims 6 act as bimetallic springs and upon heating bow up, thereby raising the chip 2 and separating the solder joint 4 as shown in Fig. 4. The liquid 1 would still be...