Browse Prior Art Database

Barrier Film Applications to PTH Component Rework

IP.com Disclosure Number: IPCOM000101321D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 87K

Publishing Venue

IBM

Related People

Davis, CR: AUTHOR [+2]

Abstract

Component rework is an essential process in an electronic manufacturing environment. The process utilizes a high, thermally conductive, liquid medium, such as solder, which is pumped through a chimney to the component rework site of a card or board. During the direct contact of the fountain solder with the PTH solder, extensive dissolution of copper present in the PTH occurs. Presently, the need to ensure rework capability drives the initial plated copper thickness. However, increasing the copper thickness is limited by throughput and line width tolerance requirements.

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Barrier Film Applications to PTH Component Rework

       Component rework is an essential process in an electronic
manufacturing environment.  The process utilizes a high, thermally
conductive, liquid medium, such as solder, which is pumped through a
chimney to the component rework site of a card or board.  During the
direct contact of the fountain solder with the PTH solder, extensive
dissolution of copper present in the PTH occurs.  Presently, the need
to ensure rework capability drives the initial plated copper
thickness.  However, increasing the copper thickness is limited by
throughput and line width tolerance requirements.

      The disclosed process presents a new method utilizing polymeric
thin films as barrier layers for card and board component rework
processes to address the problem of copper dissolution.  The thin
films, approximately 0.5 - 2 mils thick, are applied directly over
the component rework site by several processes, for instance,
polymeric dispersion, solution, or preformed existing films.  Barrier
films are utilized both for defective component removal and good
component insertion.  The film, having a low surface-free energy, is
poorly wetted by the molten chimney solder during fountain cycling
for component removal/insertion.  This reduces the dynamic
interaction of the solder with the PTH copper, therefore inhibiting
copper dissolution.  In addition, the film does not restrict the
efficient transfer of heat from the fountain sold...