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Continuous Foam Flux Dispenser for Water Soluble Flux

IP.com Disclosure Number: IPCOM000081205D
Original Publication Date: 1974-Apr-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Ballard, RH: AUTHOR [+3]

Abstract

In automated circuit board soldering line processes, fluxes are used to clean the circuit boards prior to the application of solder in a flow or wave-soldering type of operation. It has been found that the percentage of bad solder joints is directly related to the quality and evenness of application of flux. A fluxer assembly has previously been utilized in which an air stone generates a froth of flux, which is applied in a continuous contact bath against the surface of circuit boards that are to be cleaned. However, volatile solvents used with the flux have been found to evaporate, thereby changing the specific gravity of the flux solution and producing a negative effect on the quality of finished solder work.

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Continuous Foam Flux Dispenser for Water Soluble Flux

In automated circuit board soldering line processes, fluxes are used to clean the circuit boards prior to the application of solder in a flow or wave-soldering type of operation. It has been found that the percentage of bad solder joints is directly related to the quality and evenness of application of flux. A fluxer assembly has previously been utilized in which an air stone generates a froth of flux, which is applied in a continuous contact bath against the surface of circuit boards that are to be cleaned. However, volatile solvents used with the flux have been found to evaporate, thereby changing the specific gravity of the flux solution and producing a negative effect on the quality of finished solder work. The buildup of reaction products which collect in the flux basin also has an injurious effect on the quality of the finished work. A solution to these problems which greatly increases the yield of good circuit boards from the soldering operation has been developed, as shown in Fig. 1.

In Fig. 1 a trough 1 contains, for example, water soluble flux in solution 2. The flux is foamed by air under pressure being fed into a porous stone 3 which is immersed in solution 2 inside of trough 1. The low-pressure air hose connection to stone 3 is not shown for the sake of clarity. Stone 3 sits on two supports 4 inside of a foam chimney 5 which carries a flexible skirt 6 on its top edge.

Skirt 6 provides even distribution of foam to the underside of circuit boards passing through the foam at the top of chimney 5. Skirt 6 is also serrated to permit protrusions from the bottom of circuit boards, such as components leads, to pass through the skirt.

The remainder of trough 1, since it would expose the solution to:= the open air, is covered as much as possible such as by cover 7 to reduce the amount of liquid flux exposed to the air. It has been found that due to the evaporation that occurs, that the specific gravity of the solution is constantly changing. In order to detect the state of the constantly changing specific gravity, the specific gravity is constantly monitored by a hygrometer tube 10 which is attached in communication via port 11 with the fluid in tr...