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Wave Solder Flux Automatic Feed System

IP.com Disclosure Number: IPCOM000044778D
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Cheng, JC: AUTHOR [+2]

Abstract

The figure shows the wave solder flux automatic feed system. A flux reservoir 2 feeds liquid flux through a valve 4 over the line 6 by gravity to the flux pot 8. The flux from line 6 is controlled to flow into the flux pot 8 by means of the float valve 9. Modules whose pins are to be tinned by means of reflowing the solder on their surface must have a fluxing material added to remove the accumulation of oxides and other debris. The modules pass along the path 10 above the flux pot 8 and a foaming device 12 creates a foamed medium for the flux in the flux pot 8 which comes into contact with the pins on the modules passing along the path 10.

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Wave Solder Flux Automatic Feed System

The figure shows the wave solder flux automatic feed system. A flux reservoir 2 feeds liquid flux through a valve 4 over the line 6 by gravity to the flux pot 8. The flux from line 6 is controlled to flow into the flux pot 8 by means of the float valve 9. Modules whose pins are to be tinned by means of reflowing the solder on their surface must have a fluxing material added to remove the accumulation of oxides and other debris. The modules pass along the path 10 above the flux pot 8 and a foaming device 12 creates a foamed medium for the flux in the flux pot 8 which comes into contact with the pins on the modules passing along the path 10.

As the modules pass along the path 10, they accumulate flux and over a period of time, the level of the flux in the flux pot 8 goes down. This condition is sensed by the float valve 9 which then admits additional flux from the line 6 from the reservoir 2, so as to maintain a relatively constant level of flux in the flux pot
8.

In addition, the foaming action in the flux pot and the general exposure of the surface of the flux in the flux pot to the ambient air causes the more volatile constituents in the flux to evaporate. One of the volatile constituents in the flux is isopropyl alcohol (IPA). An additional mechanism is provided to replenish the lost isopropyl alcohol in the flux so as to maintain a relatively constant composition for the flux in the flux pot.

To this end, an additional circulating loop consisting of the pipe 14, the beaker 22 and the return pipe 23 allows additional isopropyl alcohol to be added to the flux when needed. This is accomplished as follows: Flux from the flux pot 8 is conducted out on the line 14 through the pump 20 to the beaker 22. In beaker 22 there is a hydrometer 24 which measures the relative specific gravity of the flux pumped from the flux pot 8 into the beaker 22. A photocell 26 is positioned proximate to the hydrometer 24, for reading the hydrometer scale and providing an electrical output to the fluid control valves 28 and 16.

Isopropyl alcohol, the volatile constituent in the flux, is contained in the reservoir 30. The reservoir 30 feeds the isopropyl alcohol through the valve 32 and the pipe 34 to the valve 28. When the photocell 26 detects that the hydrometer reading indicates a relatively higher specific gravity for the flux in the beaker...