Browse Prior Art Database

Chip Retention Scheme

IP.com Disclosure Number: IPCOM000119889D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Bickford, HR: AUTHOR [+2]

Abstract

In Josephson technology, packaging generally requires that an array of circuit chips be attached to a chip carrier substrate using liquid mercury contacts. The contacts afford physical retention of the chips to the carriers as a result of the high surface tension of the mercury, even at room temperatures. However, for ease of handling of the populated carrier, it is desirable to provide additional retention support. A retention plate for this purpose is shown in Figs. 1 and 2.

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Chip Retention Scheme

      In Josephson technology, packaging generally requires
that an array of circuit chips be attached to a chip carrier
substrate using liquid mercury contacts.  The contacts afford
physical retention of the chips to the carriers as a result of the
high surface tension of the mercury, even at room temperatures.
However, for ease of handling of the populated carrier, it is
desirable to provide additional retention support.  A retention plate
for this purpose is shown in Figs. 1 and 2.

      Due to the close packing of chips and to the pitch of the
mercury contacts, retention of the chips must be positive and the
retention plate must be accurately placed. In Fig. 1, the chip
carrier 10 has a plurality of circuit chips 12 which are attached
thereto by the liquid mercury contacts 14.  A silicon retention plate
16, having pyramidal- shaped openings 18 therein, provides access for
circuit chip cooling.  Since plate 16 is fabricated from silicon, it
is thermally matched to the carrier substrate, which is also silicon.
The openings 18 are obtained by photolithographic processing and
anisotropic etching of (100) silicon substrates from one side to form
partial pyramids.  The dimensions and tolerances of the retention
surfaces are precisely controlled, and latitude is provided for
variations in mercury contact height.

      Fig. 2A is a top view of the retention plate 16, while Fig. 2B
is a cross section of the plate.  The dashed line in Fig...