Browse Prior Art Database

New Flex Design for Control of Lead Bending

IP.com Disclosure Number: IPCOM000121835D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 1 page(s) / 47K

Publishing Venue

IBM

Related People

Lanzetta, A: AUTHOR [+2]

Abstract

A flexible foil edge connector of a "flex" is customarily used to interconnect high I/O electronic components where traditaional wire bonding methods become either cumbersome or obsolete. A flex typically consists of long, slender copper leads several mils wide and thick, supported by a flexible backing film, such as Kapton (Dupont), also several mils thick. The process of interconnection often involves joining these leads to matching I/O pads on the electronic components by solder reflow.

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New Flex Design for Control of Lead Bending

      A flexible foil edge connector of a "flex" is customarily used
to interconnect high I/O electronic components where traditaional
wire bonding methods become either cumbersome or obsolete.  A flex
typically consists of long, slender copper leads several mils wide
and thick, supported by a flexible backing film, such as Kapton
(Dupont), also several mils thick.  The process of interconnection
often involves joining these leads to matching I/O pads on the
electronic components by solder reflow.

      Kapton "windows" are often created in the bonding areas in
order to facilitate physical contact between flex leads and I/O pads
and also access to solder by the hot gas used to reflow it.  The
copper leads protrude into the window as cantilevered beams, with one
end held at the Kapton edge. Upon lead bonding and subsequent thermal
cycling, the leads further from the center of the flex have a greater
tendency to bend, and, in extreme cases, can either touch adjacent
leads or crack, leading to failure.

      Disclosed is a new flex design intended to overcome or minimize
this lead bending problem.  This design provides added support of the
leads over the crucial joining areas by either anchoring the lead at
both ends across the Kapton window, or by allowing the lead to be
totally supported by Kapton.  In cases where hot gas access to solder
becomes a problem, Kapton windows can be created between adjacent
leads to...