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Fine Pitch Attachment Process Using a Polyimide-Solder Preform

IP.com Disclosure Number: IPCOM000100903D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Adams, L: AUTHOR [+3]

Abstract

A method is described for bonding very fine pitch components so as to eliminate the need for a panel solder application process and its associated concerns, such as solder height and uniformity variations, and to decrease the degree of planarity needed in the bonding system, thus improving yield.

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Fine Pitch Attachment Process Using a Polyimide-Solder Preform

       A method is described for bonding very fine pitch
components so as to eliminate the need for a panel solder application
process and its associated concerns, such as solder height and
uniformity variations, and to decrease the degree of planarity needed
in the bonding system, thus improving yield.

      Referring to Fig. 1, the bonding process proceeds as follows:
The pads (1) are fluxed if necessary, and the component leads (2) are
placed on top of the pads, with the solder preform (3, 4) on top of
the leads.  A heated thermode (5) is then applied to the top of the
solder preform.  Under the proper conditions of temperature and
pressure, enough heat will transfer through the polyimide to reflow
the solder.  Capillary action will then cause the molten solder to
flow along the lead-pad interface (Fig. 2). The thermode is then
removed, and a strong solder joint has been formed.  The solder
"heel" fillet is shown in Fig. 2. Finally, the polyimide (4) is
peeled away.  Since the polyimide will not degrade at the bonding
temperature, the solder preform carrier can be recycled many times.

      Fig. 3 shows a proposed solder-preform carrier.  The center
hole (6) would vary in size depending on the component's size.  The
preform frame is shown as (7).