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Solder Balls and Humidity

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#51530

Solder Balls and Humidity | 23 August, 2007

I want to get a collective opinion from the forum... I was always under the impression that Humidity at SMT can be a disaster and can cause solder balls... But what about at the Wave/Selective solder? If every board or almost every board has solder balls, could this be attributed to humidity? What kind of level of solder balls will you see do to humidity?

Feed back would be greatly appreciated.

Thanks

GRICS

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#51531

Solder Balls and Humidity | 23 August, 2007

Water soluable fluxes are quite hydroscopic. If you keep RH below 50 percent, solder balling caused by humidity should be minimized.

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#51535

Solder Balls and Humidity | 24 August, 2007

Solder balls with wave soldering can have different causes. The two most important are the solderresist and the flux. I have similar problems, after changes the flux type 90% off all solderballs are gone.

KR,

Joris Groot koerkamp

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#51537

Solder Balls and Humidity | 24 August, 2007

I agree with Joris. But to add to his comment, the type of finish also has a direct affect to your wave solder process. Going from a gloss finish to a matte finish may help a lot.

As for humidity affecting your wave - I doubt it. I use a water soluable flux and have no issues with solder balling.

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#51539

Solder Balls and Humidity | 24 August, 2007

What about when using noclean and alcohol based fluxes? Could humidity still cause issues?

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#51540

Solder Balls and Humidity | 24 August, 2007

I would say no, unless your machine is in extremeconditions. You may want to check your flux / preheat out as well. If you are leaving a lot of flux on the board at wave, it may be boiling - which can cause solder balls.

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#51579

Solder Balls and Humidity | 28 August, 2007

This is what I was thinking, but I am being beat up pretty badly by the selective solder. Ambient temperature is anywhere in the the neighborhood of 76 - 80 degrees F. I am not sure of the RH, but I wouldn't think that would be my issue...

One of our process guys noticed an increase in solder balls on hotter, more humid days, but we are talking solder balls on EVERY board.

Flux deposition is fairly low, around 40% mixture flux:air, and preheat is around 85C. Boards are FR4 material. At times we are seeing bridging as well.

I am wondering if our nozzle speed is to fast along with preheat temps possibly too low...

Another reason I do not believe it to be humidity related would be due to the PbFree process that we can run through our selective. Correct me if I am wrong, but wouldnt a Nitrogen atmosphere remove any humidity? We see solder balls equally as bad.

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