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Filtering Process for Vapor Phase Soldering Equipment

IP.com Disclosure Number: IPCOM000039595D
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 67K

Publishing Venue

IBM

Related People

Klein, KV: AUTHOR [+3]

Abstract

Vapor phase soldering solution must be filtered to remove dissolved and particulate solder flux residues. Failure to filter the solution properly results in degradation of the solution and equipment. A current filtering process used for vapor phase soldering is shown in Fig. 1. Periodically about once per day the solution 10 is drawn from the vapor phase soldering equipment sump 11 and cooled by an outside source 13 of cooling water to drop the temperature from the typical soldering temperature of 420oF to approximately 300oF . This initial cooling allows the solution to be pumped by pump 14 without damage to the pump seals and allows some of the dissolved flux residue to further precipitate.

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Filtering Process for Vapor Phase Soldering Equipment

Vapor phase soldering solution must be filtered to remove dissolved and particulate solder flux residues. Failure to filter the solution properly results in degradation of the solution and equipment. A current filtering process used for vapor phase soldering is shown in Fig. 1. Periodically about once per day the solution 10 is drawn from the vapor phase soldering equipment sump 11 and cooled by an outside source 13 of cooling water to drop the temperature from the typical soldering temperature of 420oF to approximately 300oF . This initial cooling allows the solution to be pumped by pump 14 without damage to the pump seals and allows some of the dissolved flux residue to further precipitate. The cooled solution is then pumped through standard filters 15 to remove the precipitated flux residues and foreign particles, before returning to the vapor phase equipment sump 11. This solution is continuously recirculated in this manner until the solution temperature reaches approximately 125oF which may take about 45 minutes. In this process the cooling of the solder solution in a heat exchanger causes the flux residues to precipitate and build upon the walls of the heat exchanger and piping. Thus periodic maintenance is required for cleaning the lines. Also, fluid circulating in the vapor phase equipment sump mixes the filtered solution with the non-filtered solution, reducing the total amount of flux residue in the sump, but recontaminating the solution that was just filtered. Recirculating filtering processes thus follow the law of diminishing returns and virtually never reach completion. Lastly the filtering operation requires a period of time in which the equipment usage is not available for production.

(Image Omitted)

An improved filtering process is shown in Fig. 2 in which the operational problems associated with the process of Fig. 1 have been eliminated. In the system of Fig. 2, the hot solution drains by gravity periodically through a reserve tank 20 of ambient temperature, filtered solution and into a holding tank 21. The ambient temperature filtered solution is...