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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Solder Balls

Bill H.

#5111

Solder Balls | 31 January, 2001

Hello all, I am having a problem with solder balls on chip resistors and chip capacitors. I have searched the archives and found some information concerning solder balls but have a couple more questions. 1. What is the realistic industry standard for solder ball size and quantity? 2. Is there any solder paste that is best to reduce solder balls? We use Kester type R244 NC with the alloy of 62/36/AG02 90%. We have played around with oven profile and are at the top limits of Temperature and time above 183 degrees C. Any information would be appreciated.

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Dason C

#5113

Solder Balls | 31 January, 2001

Hi! William, please check the new IPC-A-610 Rev C, para 12.4.10 for the soldeirng anomalies. Most of them may consider as process indicator and not the defect.

The most common method to elimate the solder ball is to reduce the solder volume by reduce the aperture of the stencil, you can also refer to the IPC-7525 for the stencil design. I am using 1/3 home base 6 mil stencil for the chip component.

Also, if you are running 0402 or small and you may required to specify the solder masking material ie. Enplated, etc.

Rgds.

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#5125

Solder Balls | 1 February, 2001

I side (not that we every actually choose sides here) with the other poster re: reducing solder volume. There is a solder manufacturer that advertises regularly in trade mags. that there are

"Absolutely! NONE....NIL....NADA.....mid chip beading/micro solder balling"

with their paste. Email me if you want to know the name...I hesitate to advertise for a product I've never used, so don't wanna post it here.

Regards,

Steve

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David Chapman

#5218

Solder Balls | 13 February, 2001

Bill, I can give you suggestions. First and foremost. Print a board and look under a microscope. Are you printing exactly on the pads? If you print on the mask, no matter how good we got the profile, no matter what paste we would get solder balls. Mostly they are mid chip beads, connected to the chips and resistors. So we did across the board 10% aperture reduction on .006 stencils and got our printing aligned. Humidity plays havoc as well. Now in winter here in Chicago we have 0 balls but come summer be careful.

I have tried 5 different pastes with Aim 293 showing the least balling, but your paste should be ok if you are putting it EXACTLY on the pads. We are using Alpha UP78. Hope this helps Dave C.

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