Browse Prior Art Database

Solid State Expanding Alloys for Chip Thermal Connection

IP.com Disclosure Number: IPCOM000087518D
Original Publication Date: 1977-Feb-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Koopman, NG: AUTHOR [+2]

Abstract

The figure illustrates a package which will remove heat from the back of contacts-down mounted chip 10 on substrate 11 via solder bump 12, to a liquid or air cooled heat sink 13.

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Solid State Expanding Alloys for Chip Thermal Connection

The figure illustrates a package which will remove heat from the back of contacts-down mounted chip 10 on substrate 11 via solder bump 12, to a liquid or air cooled heat sink 13.

Tolerances may be very critical to ensure sufficient heat flow if normal solders are used for this backside bump.

If a solder 13, which expands on freezing, is used to solder the back of the chip 10 to the heat sink 13, much larger chip and substrate variations can be tolerated. Some solders can be used which expand in the solid state. These solders may also be useful to take up these tolerances and keep the solder reflow pads 14 in compression. Pins 15 are input/output electrical connections to the package. Specific examples of solder compositions which expand are: 57 Bi 43 Sn (expands during solidification) 12.6 Bi 47.5 Pb 39.9 Sn (expands in solid state) 58.0 Bi 42.0 Sn (expands in solid state).

Another class of alloys which expand upon hardening are gallium alloys, especially GaSmCu, GaAu and GaNi.

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