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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Immersion Tin

celiav

#3543

Immersion Tin | 12 July, 2000

I have 2 contract manufacturers who have recently switched to immersion tin and both are experiencing problems. One supplier is having problems reflowing the solder in the oven, while the other is having insufficient hole fill at wave solder. Both have complained about having a difficult time hand soldering. Any recommendations?

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Mark Charlton

#3544

Re: Immersion Tin | 12 July, 2000

We just went through a difficult time processing SMT immersion white tins PCA's and found the following: 1. FAB vendor had a degraded tin solution resulting in improper plating thickness 2. FAB vendor was not using the proper cleaning process

Get someone that knows the process to audit the FAB vendors process. Once they clean up their process, you should have good results.

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#3545

Re: Immersion Tin | 12 July, 2000

Celiav: Mark is probably spot-on on his comments about a board fab problem. It is weird that you have similar problems from two suppliers though.

Recommendations are: � Get rid of any bird brain contractor that installs processes that affect your product quality without notifying you and demonstrating the control, effectiveness, and effectivity of the new / changed process. � Assuming you have to clean-up this mess before you can get rid of those jerks, steps to better understanding the situation are: - Determine why your suppliers are not performing incoming solderability testing on these boards to demonstrate their suppliers� process control. It seems particularly coocoo that they don�t know these boards will not solder until they get so far down-stream. - Establish the appropriateness and compatibility of the solder and flux used by your suppliers with the solderability protection on the boards. - Understand the process controls used by the board fabricator(s). Since immersion tin, like HASL, is not a plating process (something that fabs understand), it requires process control unlike their plating controls. - Two companies [ie, Dexter, Florida CirTech (Omicron)] license immersion tin technology to fabricators. Get the appropriate licenser involved. It will be difficult to determine who is less please about this: you or them.

Finally, it�s fairly disturbing that your suppliers are so technically inept that you are forced into assisting them in solving this problem. I assume, availability of technical skills is among the reasons that you decided to use an out-side supplier.

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celiav

#3546

Re: Immersion Tin | 14 July, 2000

Thanks, for the input. Any recommendations on books or articles on immersion tin and any process related issues?

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#3547

Re: Immersion Tin | 14 July, 2000

Celia: Ubet. Sorry about the ranting. (It comes with the territory.)

I don�t recall any peer reviewed stuff, but I seem to remember a couple of articles on white tin in "SMT" "Circuits Assembly" Magazine (er suppin� like that), but it was probably written by an employee of or a shill for either Dexter or Florida CirTech (Omicron). Just call those cats. [While yer at it, tell the Florida CirTech dudes [er dudettes] yud like some of their flux. Last I remember, it�s pretty cool.]

Yanno, I just thought of something. Actually, I�m always thinking of things, but this one (1) can be reprinted here and (2) actually might be on topic ...

I believe that the white tin stuff is glued-down with an OSP. There has been several threads on SMTnet on THAT junk, but we�re all bored whining about the vagaries of applying OSP, how it bears up under multiple heat cycles, and all that. [Actually now that I mention it, that sounds like a more interesting thread than some of the dregs we�ve been talking about lately.] Anywho, check it out in the archives.

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