At&t Bell Laboratories

At+t Corp.

American Telephone & Telegraph Co., At&t Bell Laboratories

American Telephone and Telegraph, Co.

Leslie A Guth

Douglas W Monroe

James A Mahler

John R Fisher

Linda M Fletcher

Urmi Ray

Jeffrey J Evans

In preparation for removing a protective adherent covercoat from a circuit board that is to be repaired, the surface integrity of the coating is altered (for example, by making incisions therein). Subsequently, the coated circuit board is subjected to supercritical carbon dioxide in a processing chamber. Following this process, the coating is easily lifted from the board.

Method for stripping conformal coatings from circuit boards

A technique is provided for manually performing a soldering operation on an article with a low-solids flux-containing solder to bond an object to the article with a reduced amount of flux residues. The technique is practiced by first manually applying heat to the article and to the object which is in contact therewith, such as by contacting the article and/or object with a heated tip of a soldering pencil, iron or gun. Once the object and article have been heated, a low-solids flux-containing solder is then applied so as to be reflowed upon contact with the heated article and the object in order to bond them together when the solder solidifies. Simultaneously, heated air (i,e., air heated above the ambient temperature) is directed at the article and the object towards the region where the solder is being applied to maintain any flux vapors, which were created upon heating of the solder, in their vaporous state. The heated air prevents condensation, and therefore unwanted deposition, of flux residues on the soldered article.

Soldering method and apparatus

An component or connector lead (12) is soldered to a bare copper metallized area (14) on a circuit board (16) using core solder (26) by manually applying heat from a heated tip (24) to a separate one of the lead and metallized area. As the heat is being applied, a vacuum is drawn in the region where the solder is applied to the lead and/or metallized area to draw off any flux vapors created upon heating of the solder. At the same time, hot air is also directed into the region where the solder is being applied to maintain the flux vapors, created upon heating of the solder, in their vaporous state to facilitate such vapors being drawn off, thereby reducing the amount of flux residues resulting from the soldering operation.

A controlled amount of flux is applied to a circuit board (10) by first directing liquid flux through a nozzle (54) containing means for disintegrating the flux into a very fine fog of tiny flux droplets (62). The fog of flux droplets is injected into a laminar gas stream (52), thereby creating a laminar flux stream which is directed at the circuit board to coat the board with flux. As the flux spray is being directed at the circuit board, the concentration of flux solids on the board is being regulated, typically by controlling the rate of flux pumped into the nozzle.

Growing community of inventors

Newtown, PA, United States of America

Leslie A Guth