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Flip Chip Bonded Ground Plane for Ceramic Chip Carriers

IP.com Disclosure Number: IPCOM000053201D
Original Publication Date: 1981-Sep-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Comerford, LD: AUTHOR

Abstract

A ground plane may be attached to a ceramic chip carrier in close proximity to conducting lines to improve high frequency isolation between conducting lines.

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Flip Chip Bonded Ground Plane for Ceramic Chip Carriers

A ground plane may be attached to a ceramic chip carrier in close proximity to conducting lines to improve high frequency isolation between conducting lines.

Referring now to Fig. 1, an attachable ground plane 10 may be made from a thin, two-sided, metallized, dielectric material 12, such as KAPTON* or MYLAR*. The metallization must be of a kind which is readily wettable by solder. In order to use such a film, the metallization 14 on one side of the film 12 must be delineated into a pattern which is the mirror image of the conducting lines 16 on the chip carrier 18. This metallization should be tinned (15). Screened-on solder paste may be used. Holes 20 must also be punched through the film so that the IC chip 22 (attached via solder 24 to conducting lines 16) and other protuberances (such as contact pins 26) on the carrier surface do not prevent the film from coming into intimate contact with the conducting lines.

After the film is prepared, it may be attached to the populated chip carrier by registering the metallization pattern on the film to the pattern on the chip carrier and heating the carrier to the melting point of the solder. If the heat is applied so that the center of the module reaches the solder melting point first, and the melt proceeds outward from the center, then the film will be pulled down to the carrier by the surface tension of the liquid solder (Fig. 2). The radial spread of the melt i...