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Date: | Tue, 9 Jan 1996 10:32:44 PST |
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On Mon, 8 Jan 1996 00:46:18 -0800 Steve Allen wrote:
> From: Steve Allen <[log in to unmask]>
> Date: Mon, 8 Jan 1996 00:46:18 -0800
> Subject: plated Tin/Lead adhesion
> To: [log in to unmask]
>
> Concerning I.R. reflowed plated Tin/Lead on single and double sided
> PCB's.
> What can cause poor adhesion of the reflowed Tin/Lead to the plated
> copper pad?
> Our plating process is : acid copper/h2o rinse /fluorboric
> dip/fluorboric Tin/lead plating/ etch/ I.R. reflow.
> The "problem" is only seen on one or two panels in a particular lot,
> and comes and goes, sometimes with months in between occurances!
> Sometimes its detected by a random tape test at pre-mask
> inspection...sometimes, "unfortunatly" it's found after the customer
> has assembled the PCB. The solder joints appear to flow very well, but
> will seperate from the copper if pressure is applied the component
> lead.
> No copper is attached to the solder joint that has lifted.
> The copper pad below is usually somewhat oxidized.
> We have explored many possible causes, including excessive hold time
> between steps, etc.
> I would appreciate any thoughts on this, if anyone has some ideas...?
>
Steve: There have been many good responses to your question on
plating adhesion however the piece of information here that I keep
coming back to is how intermitent and selective(1-2panels)the
problem is.I would suspect somthing more like a bad rack or anode
more than a general chemistry problem.
Two questions: Is the Sn/Pb thickness lower on the defective boards
found in house? What is the appearance of the fused Sn/Pb on these
boards?
If you want to discuss this further please feel free to give me
a call.We do a LOT of IR fused Sn/Pb electroplate.
Regards
Michael Barmuta
Staff Engineer
Fluke Corp.
(206)356-6076
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