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Leaded Water Soluble recommendation needed

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Leaded Water Soluble recommendation needed | 29 May, 2013

Would like opinions on which brand of leaded water soluble solder has the longest print life.

we're currently using Alpha WS-809. Each board goes through the printer every 15 minutes or so, and we wind up re-printing most boards as the solder isn't filling the pads. We wipe with solvent and vacuum after each print, so we're not sure why the paste isn't getting through the smaller footprints other than the solder is drying out.

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Leaded Water Soluble recommendation needed | 30 May, 2013

I like AIM solder paste, personally. But, much like asking which pick and place machine is best on this board, you're likely to get as many opinions as there are paste manufacturers.

I just took a look at Alpha's datasheet for this product, and it seems like a standard paste. It's got a shelf life of 2 weeks at room temperature, as do a lot of other pastes. Given this, I wouldn't expect significant drying in 15 minute cycle times.

A couple of things to check: 1. The operating environment like for the stencil printing? Temp/Humidity/air flow. 2. Temperature of the paste at the beginning of operations (warmed up to room temp per vendor recommendations?). 3. Aperture design of stencil. 4. Age/storage conditions of the solder paste. 5. Appropriate sphere size for aperture design/application.

It might be worth getting the paste rep/application engineers involved in helping you diagnose the root cause of your issue. They have the most knowledge about the paste product you're using, and can analyze your process with their product to determine the causes and potential solutions.

Cheers, ..rob

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Leaded Water Soluble recommendation needed | 15 August, 2013

Hi, I'm using WS-820 by Alpha metals and works good, but you must take in consideration the humidity and temperature that you have in your facility, In the process that we're following we left the board printed during 2 hrs and works ok (no pop up effect during the reflow process) and if the printer is idle during 10-15 min there are no issues. note: our stencils are laser cut.

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