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Anti-Bowing Solder Fixture

IP.com Disclosure Number: IPCOM000118781D
Original Publication Date: 1997-Jul-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Isaacs, PD: AUTHOR [+2]

Abstract

Disclosed is a design for wave-solder fixtures which hold the connectors and printed circuit boards in a counter-bow situation so that when the boards cool to room temperature, the bow in the assembly is neutralized to zero or near zero.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 71% of the total text.

Anti-Bowing Solder Fixture

      Disclosed is a design for wave-solder fixtures which hold the
connectors and printed circuit boards in a counter-bow situation so
that when the boards cool to room temperature, the bow in the
assembly is neutralized to zero or near zero.

      In order to meet the thin side-wall requirements of higher
density connectors, connector manufacturers are using Liquid Crystal
Polymer (LCP) as a plastic of choice.  LCP has extremely good
characteristics for thin profile molded parts.  LCP has a coefficient
of thermal expansion around 4-5 ppm/Degree C.  When this is put
through a wave-solder process, the printed circuit board, which has a
coefficient of thermal expansion (Cte) of 18-24 ppm / degree C., gets
approximately 215 - 260 degrees C.  The connector attains a
temperature of 70 - 100 degrees C.  Both the Cte mismatch and the
delta T. create a situation where when everything cools back to room
temperature, the printed circuit board contracts more than the
connector and creates a significant bow in the assembly.  The
anti-bow solder fixture corrects the bow in the printed circuit
boards.  The wave-solder fixtures hold the connectors and printed
circuit boards in a counter bow situation such that when the boards
cool to room temperature the bow in the assembly is neutralized to
zero or near zero.  Done properly, when the bowing is neutralized,
the stress on the solder joints is neutralized as well.  So the
process provides both a...