Browse Prior Art Database

Semiconductor Chip Lift to Improve Interconnection Reliability

IP.com Disclosure Number: IPCOM000082956D
Original Publication Date: 1975-Mar-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Gregor, LV: AUTHOR

Abstract

The reliability of lead-tin or lead-indium solder interconnections in a flip-chip semiconductor structure can be improved, if the height of the joint can be increased. This provides a more columnar and compliant joint to undergo thermal mismatch stresses.

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Semiconductor Chip Lift to Improve Interconnection Reliability

The reliability of lead-tin or lead-indium solder interconnections in a flip-chip semiconductor structure can be improved, if the height of the joint can be increased. This provides a more columnar and compliant joint to undergo thermal mismatch stresses.

The present method provides uniform lifting of a silicon die or "chip" during the time that the solder is liquid, using a ferromagnetic alloy (FE-Ni, Al-Ni-Co, Ni- Cu) on the back side of the chip and a properly designed permanent magnet placed over the chip, to elevate the previously soldered chip to proper height.

Figs. 1 and 2 illustrate one embodiment of the chip lift process, where the glass barrier or dam type of flip-chip structure is used. A ceramic substrate 1 has conductor layers 2 thereon and the chip connection sites prepared by deposit of a nonsolder wetting coating 3 composed typically of glass, as shown, across the conductors 2. The composite is dip coated with solder to form layer 4 upon the conductor layer 2 which are wettable with solder. The chip sites have solder thereon and are isolated from the remaining solder by barriers 3.

A semiconductor chip 5 having solder balls 6 extending therefrom and a ferromagnetic coating 7 upon its back, is placed upon the connection sites. A magnet 8 is placed over the chip 5.

The structure is placed in a furnace where the temperature will allow the solder to be liquid. The solder balls 6 will flow...