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Micro Solder Balls and Vias bridging Issue

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VB

#73624

Micro Solder Balls and Vias bridging Issue | 2 March, 2015

Hi We are using Universal carrier for a 2 sided PCB, where the bottom side goes for hand solder the switches after wave. Our issue is, we are getting micro solder balls all over PCB bottom after wave, whereas we got numerous vias, which also turns to be a issue when it goes for Flying probe testing. Solder balls all over PCB's bottom on all via's creates big issue which is highlighted by customers as Red. Please suggest us the Wave parameters as I have tried almost all options. Ans also please suggest best option for via's solder fills issue too. Via's are not tented. Thanks

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#73625

Micro Solder Balls and Vias bridging Issue | 3 March, 2015

I would presume you reflow the top of the board first. Use tented vias. As you have worked out, vias have surface tension, which sucks the solder up the hole during reflow of the bottom of the board.

Good luck!

regards sarason

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VB

#73626

Micro Solder Balls and Vias bridging Issue | 3 March, 2015

Hi

I also forgot to mention, top side is reflowed first at SMT. Tenting vias is good option. we are looking into it. Can you please also suggest any solution to avoid solder balls at bottom side in other places than vias.

Thanks

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#73632

Micro Solder Balls and Vias bridging Issue | 3 March, 2015

A couple of things that have helped me with solder ball issues at wave in the past:

1. Flux. Insure good flux coverage on the bottom of the board.

2. Preheat. Insure that the board is sufficiently preheated for the wave operation. Since you're using a carrier, also insure that the carrier is appropriately heated. A large temperature differential between the carrier and the board could be affecting your quality.

3. Air knife. If your wave machine is equipped with an air-knife, it can help in removing the loose/excess solder.

4. Dross. Make sure that your solder pot is well de-drossed, but, not completely de-drossed. Leaving a minimal amount of dross in the pot will help with minimizing the amount of dross that is generated during operations.

5. Tented vias, as already mentioned, will help with your issues with vias.

Cheers, ..rob

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