Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

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Lead Free De-Wetting...

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Lead Free De-Wetting... | 25 April, 2008

Our company has run into an issue with de-wetting of lead free components. Our profile is dead on with paste manufacturers specs. We have had this issue with both gold immersed, and hot air leveled boards. We have tried three different solder paste manufacturers. At first it looked like contamination as the solder seemed to ball up to the part leads. But after washing the PCB's, cleaning with Isopropyl and then finally changing board types (Gold to silver)we have seen the same results. As we have reworked the boards with Weller forced hot air guns the results seem to improve. A few seconds under the guns seem to allow the solder to properly reflow. In the oven profile, I have tried increasing the heat, decreasing the heat, increase/decrease time exposed to heat, and the time the solder is actually in the liquidus state. Currently we have our board manufacturer testing samples for solderability. We have run lead free for quite a long time now, including boards from the same lot we are seeing this issue with now and never had a problem. The issue seemed to just appear from no where. Thank you in advance for any and all help and/or feedback.

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Lead Free De-Wetting... | 28 April, 2008

Here's a crude wettability test.

Take a PCB - both types of finish - print them, and reflow with no components using your standard profile. Observe the wetting spread and flow of the solder paste.

This rules in/out that it's PCB solderability.

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Lead Free De-Wetting... | 28 April, 2008

Thanks, I will give it a try this afternoon.

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