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Inert Fluorocarbon Rework Method

IP.com Disclosure Number: IPCOM000035183D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Hagstrom, RA: AUTHOR

Abstract

Connectors are commonly soldered into printed circuit boards with vapor phase soldering using fluorocarbon liquids. This type of soldering is used when pins plated with precious metals are required, but wave soldering processing cannot be used. Also, rework must not affect the precious metal plating.

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Inert Fluorocarbon Rework Method

Connectors are commonly soldered into printed circuit boards with vapor phase soldering using fluorocarbon liquids. This type of soldering is used when pins plated with precious metals are required, but wave soldering processing cannot be used. Also, rework must not affect the precious metal plating.

This operation is "messy" at best and requires frequent replacement of the oil. In addition, the epoxy resin of the printed circuit board is softened where it is not protected.

It has been discovered, according to the present method, that the use of a high boiling point inert fluorocarbon liquid, instead of the soldering oil, eliminates the resin softening problem. Such an inert fluorocarbon liquid is available commercially from 3M under the tradename FC71 or GladenLS260. An additional advantage of the use of such inert fluorocarbon liquid is that the board comes out clean, the operation is not messy and the fluid never needs to be changed.

The high cost of the inert fluorocarbon liquid requires redesign of the rework operation, so that all fumes generated are collected, condensed and recycled. Coils to chill the fluorocarbon fumes must be about 140 degrees F to ensure that the fluorocarbon is chilled and that no water vapor condenses. A device, such as shown in the figure, is quite satisfactory for this purpose.

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