Browse Prior Art Database

Floating Backbond Mounting for a Chip Device

IP.com Disclosure Number: IPCOM000079621D
Original Publication Date: 1973-Aug-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 22K

Publishing Venue

IBM

Related People

VanVestrout, VD: AUTHOR

Abstract

A floating backbond mounting for a chip device is made by using a low-melt solder alloy, Which melts at approximately 47'C (116'F). A metalized silicon chip 10 is backbonded to the substrate 11 with a low-melt solder 12 and the chip-to-substrate interconnections are made by conventional decal or wire bonding. The chip 10 is located in a well 13 of the substrate 11 which contains the low-melt solder 12. An encapsulation preform 14 is placed over the chip 10 and is adhesively joined to the substrate 11 forming a seal 15, such that the molten solder will not flow out of the well 13.

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Floating Backbond Mounting for a Chip Device

A floating backbond mounting for a chip device is made by using a low-melt solder alloy, Which melts at approximately 47'C (116'F). A metalized silicon chip 10 is backbonded to the substrate 11 with a low-melt solder 12 and the chip-to- substrate interconnections are made by conventional decal or wire bonding. The chip 10 is located in a well 13 of the substrate 11 which contains the low-melt solder 12. An encapsulation preform 14 is placed over the chip 10 and is adhesively joined to the substrate 11 forming a seal 15, such that the molten solder will not flow out of the well 13.

Chip junction temperatures vary between 65 degrees C and 125 degrees C. Consequently, the temperature of the backbond can vary between 40 degrees C and 100 degrees C, depending upon the materials and design of the package configuration. The heat from the chip 10 will be sufficient to melt the solder 12 in the well 13, but it will be contained within the encapsulation preform 14. The molten solder surface tension and the chip-to-substrate interconnections will hold the chip 10 in place. The molten solder will not transfer the stresses caused by thermal expansion mismatch and, therefore, the connections will not be overstressed. The molten solder will maintain a good metallurgical contact between the chip and substrate, providing for maximum heat conduction.

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