Browse Prior Art Database

Stacked Flex Cable with Thermally Matched SMT Connectors

IP.com Disclosure Number: IPCOM000110966D
Original Publication Date: 1994-Jan-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Caulfield, T: AUTHOR [+6]

Abstract

As flex cabling becomes a more accepted way to interconnect MCMs (MultiChip Modules) made from ceramic and glass ceramic it is necessary to design these cables in a narrow form factor to allow the large number of I/Os to be accommodated on the carrier perimeter. It is also imperative to design cable ends with materials similar to the substrate materials that will allow a single cable to be removed and replaced due to a defect or EC. The cable described here will allow for these requirements to be met while retaining flexibility and the proper impedance values.

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Stacked Flex Cable with Thermally Matched SMT Connectors

      As flex cabling becomes a more accepted way to interconnect
MCMs (MultiChip Modules) made from ceramic and glass ceramic it is
necessary to design these cables in a narrow form factor to allow the
large number of I/Os to be accommodated on the carrier perimeter.  It
is also imperative to design cable ends with materials similar to the
substrate materials that will allow a single cable to be removed and
replaced due to a defect or EC.  The cable described here will allow
for these requirements to be met while retaining flexibility and the
proper impedance values.

      To describe the cable components that are proposed here, it
should be noted that the flex system will be a subtractive process
due to the relaxed line width and spacing ground rules.  The
invention can be practiced also with an additive process.  To
describe the flex, assume a metal thickness of 18 um for both signal
and ground and 63 um for the polyimide and adhesive insulating
layers.  Cable length will be determined by the interconnection needs
of the system and also from the limitations of the exposure system
necessary to define the metal conductors.  The signal line widths for
the above thickness's will be 50 um on a pitch of 150 um to yield a
cable with a desired 50-ohm impedance.  The conductors will be copper
with a top surface metallurgy of variable thickness gold that will be
dictated by the bonding process used to attach...