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Improved Reliability of Reworked Cards

IP.com Disclosure Number: IPCOM000085635D
Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Adams, RF: AUTHOR [+4]

Abstract

The technique described relates to printed-circuit cards which have both pins for making connections through removable electrical connectors and tabs where components or connectors can be soldered to the card. The pins have a palladium-tin coating and they are soldered into holes in the card. The tabs are widened areas of circuit lines which have an immersion tin surface to facilitate soldering.

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Improved Reliability of Reworked Cards

The technique described relates to printed-circuit cards which have both pins for making connections through removable electrical connectors and tabs where components or connectors can be soldered to the card. The pins have a palladium-tin coating and they are soldered into holes in the card. The tabs are widened areas of circuit lines which have an immersion tin surface to facilitate soldering.

It is sometimes necessary to rework printed-circuit cards because of errors that occur during the manufacturing process, or because of changed engineering requirements. During this rework operation, the card is heated to melt or reflow the solder which connects the pins to the board. When the board is heated to reflow the solder around the pins, the heat degrades the immersion tin surface on the tabs. Either a high percentage of the reworked cards must be discarded, or an additional immersion tin operation must be provided to restore the tabs to a solderable condition. It has been found that if an additional immersion step is provided, the surface of the pins become contaminated thereby lowering the reliability.

The contamination of the pins can be prevented, thereby increasing the reliability of the final board if, during the solder reflow operation, the pins are covered. The pins can be covered utilizing the same type of connector into which the pins normally plug. The connector used as a cover can be filled with a plastic material...