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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


REFLOWING WHITE TIN PLATED PADS

GREG DENHAM

#10082

REFLOWING WHITE TIN PLATED PADS | 18 August, 1999

WE ARE CURRENTLY HAVING PROBLEMS REFLOWING BOARDS WITH WHITE TIN PLATING. WE ARE NOT GETTING GOOD WETTING ON THE PADS. WE HAVE CHECKED THE REFLOW PROFILE AND TRIED DIFFERENT PASTE'S. WE THINK THERE MAY BE CONTAMINATION OR OXIDATION ON THE PADS. IS THERE A WAY OF CLEANING THE BOARDS WITH OUT HARMING THEM? ANY IDEA'S OR SUGGESTIONS?

THANKS, GREG DENHAM

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J.J. Thomas

#10083

Re: REFLOWING WHITE TIN PLATED PADS | 18 August, 1999

| WE ARE CURRENTLY HAVING PROBLEMS REFLOWING BOARDS WITH WHITE TIN PLATING. WE ARE NOT GETTING GOOD WETTING ON THE PADS. | WE HAVE CHECKED THE REFLOW PROFILE AND TRIED DIFFERENT PASTE'S. | WE THINK THERE MAY BE CONTAMINATION OR OXIDATION ON THE PADS. | IS THERE A WAY OF CLEANING THE BOARDS WITH OUT HARMING THEM? | ANY IDEA'S OR SUGGESTIONS? | | THANKS, | GREG DENHAM

This is the picture that was to be displayed. |

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Brian

#10084

Re: REFLOWING WHITE TIN PLATED PADS | 18 August, 1999

| WE ARE CURRENTLY HAVING PROBLEMS REFLOWING BOARDS WITH WHITE TIN PLATING. WE ARE NOT GETTING GOOD WETTING ON THE PADS. | WE HAVE CHECKED THE REFLOW PROFILE AND TRIED DIFFERENT PASTE'S. | WE THINK THERE MAY BE CONTAMINATION OR OXIDATION ON THE PADS. | IS THERE A WAY OF CLEANING THE BOARDS WITH OUT HARMING THEM? | ANY IDEA'S OR SUGGESTIONS? | | THANKS, | GREG DENHAM |

Greg

Info is a little sketchy to give a categorical response. What do you mean by white tin plate? I could interpret it either as a pure tin electroplate, possibly c. 10 �m, before etch or a chemical tin dip, possibly 0.1 �m, after etch and stripping. What is under the tin? The photo is a little difficult, also. It could be you have dewetting or it could be, if the tin is reasonably thick, that you are taking it to just about melting point during reflow and the melt is patchy.

I would not be happy with a chemical tin dip. The tin would be too thin and porous to provide any protection and it may have organics co-deposited. Better to leave it as bare copper with an organic solderability coating.

Would be happy to discuss this further if you are able to supply more details.

Brian

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Earl Moon

#10085

Re: REFLOWING WHITE TIN PLATED PADS | 18 August, 1999

| | WE ARE CURRENTLY HAVING PROBLEMS REFLOWING BOARDS WITH WHITE TIN PLATING. WE ARE NOT GETTING GOOD WETTING ON THE PADS. | | WE HAVE CHECKED THE REFLOW PROFILE AND TRIED DIFFERENT PASTE'S. | | WE THINK THERE MAY BE CONTAMINATION OR OXIDATION ON THE PADS. | | IS THERE A WAY OF CLEANING THE BOARDS WITH OUT HARMING THEM? | | ANY IDEA'S OR SUGGESTIONS? | | | | THANKS, | | GREG DENHAM | | This is the picture that was to be displayed. | | | | White tin is an immersion coating analog to any electroless deposition. It differs from regular tin in that it also is composed of an organic chemistry. This, supposedly, provides both a metallic and organically protective solder surface.

If the process is not properly managed, what's new, it will leave an oxide contamination of the surface to be soldered. No amount of post coating with remove the oxide.

However, there is light at the end of a dark tunnel. You can take these boards and have them HASL'd. Of course, the reason you used white tin in the first place was not to be HASL'd by HASL.

Earl Moon

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#10086

Re: REFLOWING WHITE TIN PLATED PADS | 18 August, 1999

| WE ARE CURRENTLY HAVING PROBLEMS REFLOWING BOARDS WITH WHITE TIN PLATING. WE ARE NOT GETTING GOOD WETTING ON THE PADS. | WE HAVE CHECKED THE REFLOW PROFILE AND TRIED DIFFERENT PASTE'S. | WE THINK THERE MAY BE CONTAMINATION OR OXIDATION ON THE PADS. | IS THERE A WAY OF CLEANING THE BOARDS WITH OUT HARMING THEM? | ANY IDEA'S OR SUGGESTIONS? | | THANKS, | GREG DENHAM | Greg:

BOARD FAB QUESTIONS: Whose white tin is it? How long has it been since it was processes at the fab? Have you checked the fabs white tin process controls? How was it stored?

ASSEMBLER QUESTIONS: How was it stored? Great picture, but it's tough to tell much. Are the component leads dewetting also?

MY INCLINATION: Earls' correct ... your fab tripped over his tank.

My2�

Dave F

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Tony Yang

#10087

Re: REFLOWING WHITE TIN PLATED PADS | 18 August, 1999

| WE ARE CURRENTLY HAVING PROBLEMS REFLOWING BOARDS WITH WHITE TIN PLATING. WE ARE NOT GETTING GOOD WETTING ON THE PADS. | WE HAVE CHECKED THE REFLOW PROFILE AND TRIED DIFFERENT PASTE'S. | WE THINK THERE MAY BE CONTAMINATION OR OXIDATION ON THE PADS. | IS THERE A WAY OF CLEANING THE BOARDS WITH OUT HARMING THEM? | ANY IDEA'S OR SUGGESTIONS? | | THANKS, | GREG DENHAM | I assume the this is immersion white tin surface finish. We ran several prototype boards which resulted with fair good solder wetting on surface mount pads. However, we found pin holes on through-hole parts. You may have to check the surface finish process since the thickness of tin would affect the solderability. It is easy to form Cu/Sn intermetallics during storage and thermal cycling if the surface finish process is not well controlled.

Tony Y.

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