Browse Prior Art Database

In Situ Flux for Tin Bismuth Solder Reflow Rework

IP.com Disclosure Number: IPCOM000079996D
Original Publication Date: 1973-Oct-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Peter, AE: AUTHOR

Abstract

In the rework of wire-bond sites using tin-bismuth solder, normal fluxes cannot be used because flux removal is difficult due to the large quantity of delicate wires normally on or near a printed-circuit board.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 1

In Situ Flux for Tin Bismuth Solder Reflow Rework

In the rework of wire-bond sites using tin-bismuth solder, normal fluxes cannot be used because flux removal is difficult due to the large quantity of delicate wires normally on or near a printed-circuit board.

In the event a printed-circuit board has to be reworked, it is sometimes necessary to add solder to effect joining of a wire to a wire site. Usually both the solder and the rework site are oxidized and require a flux to insure proper reflow of the solder when heated. Due to the delicate nature and the large quantity of wires in the assembly, the cleaning of flux residues provides an exposure for damage to other components or wires associated with the printed-circuit board.

To overcome these difficulties, the wire used in the assembly work is insulated with a multiple pass, cured polyurethane compound. This compound, when applied to the solder and rework sites, provides the necessary deoxidation to allow the solder and the residual site solder to become homogeneous, and effect a bond of the new wire to the wire site. After all rework has been completed, the assembly is then baked at 50 degrees C for approximately 1 hour to solidify the liquid polyurethane on the rework wire sites.

1