Yep, as a matter of fact, they're all done.

----- Original Message -----
From: "John Burke" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, October 19, 2006 1:19 PM
Subject: Re: [TN] Oxidized PCBs


> Oh,
>
> I see you found a faster way!!
>
> John
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
> Sent: Thursday, October 19, 2006 10:05 AM
> To: [log in to unmask]
> Subject: Re: [TN] Oxidized PCBs
>
> Rich,
>
> Rich,
>
> Sorry I just got to this email.
>
> I believe I have a way for you to recover them economically providing that
> NO COMPONENTS HAVE BEEN LOADED on the reverse side.
>
> If this is the case, cut a stainless steel stencil say 6 mils thick for
> the
> component pads.
>
> Align the stencil to the board pads using a frame which you are going to
> make cheaply at your local tooling house to hold the loaded board in a
> nest
> and hold the stencil frame.
>
> Then you are going to use an airbrasive micro blaster loaded with
> something
> like coconut shell to remove the oxide. The stencil will mask the board
> material and so only the solderable areas will get the treatment.
>
> You will then clean the assembly thoroughy agitating in DI water, followed
> immediately by a rinse in IPA which will remove any residual water.
>
> Then you are going to assemble them the same day.
>
> Have fun
>
> Any other method I believe may involve you in field failure which would be
> far more expensive potentially than scapping the boards
>
> If you need any clarification call me please any time after 08-30 AM
> pacific
> time on my mobile.
>
> 408 515 4992
>
> Kind regards,
>
> John
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of JaMi Smith
> Sent: Wednesday, October 18, 2006 9:04 PM
> To: [log in to unmask]
> Subject: Re: [TN] Oxidized PCBs
>
> I am going way out on a limb here, so please save the boo's and hiss's.
>
> 1. How much assembly is done on the other side? Anything that can be
> striped
> off without too much loss and without damage?
>
> 2. How much, if any, assembly is done on the affected side?
>
> 3. Can you liberally hand flux the problem areas / side with something
> like
> good old Kester 1544 Flux and do good scrub with an trimmed down acid
> brush,
> and then do a hot air reflow, followed by a good cleaning, and then try
> and
> start from scratch with paste on that side?
>
> Whatever you do, you are probably going to have to spend some rework money
> on this to get 170 units done, so the things to ask are what can be saved,
> and at what cost, and how much rework for each board is needed.
>
> You say that you have $600 tied up in each board at present. Where is that
> money? Is it in a few parts that could be pulled and used on another
> assembly? Is it in the board?
>
> I am looking at this as a "rework" problem, since even though the boards
> have never been finished, it appears that you are going to have to handle
> it
> in the same way. I am assuming that you do not have a rework department of
> your own, but you might consider setting one up, since the money you will
> spend on equipment may well be much much less than what you are about to
> lose. Another solution would be to look into someone who does rework.
>
> May just be time to looking into buying something like a "Chipmaster" from
> A.P.E., or something similar either from them or another vendor, assuming
> you have a good tech that can operate it.
>
> Time is also a big question . . . do you have any?
>
> JaMi
>
>
> ----- Original Message -----
> From: "Rich Wolbert" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Wednesday, October 18, 2006 6:31 AM
> Subject: [TN] Oxidized PCBs
>
>
>> OK, I know you guys are probably going to shake your head on this one,
>> but
>> I have to ask. We have a double sided fine pitch SMT assembly and we
>> decided to go to white tin for the pad material. Here's where the problem
>> comes in, we ran one side and when we started process the other side we
>> found counterfeit chips. We stopped production for two weeks until the
>> correct parts came in. When we tried to run the boards again, the PCB's
>> oxidized so badly over the two weeks that we can not get the solder to
>> wet. Any suggestions, other than scrapping the 170 assemblies at $600 a
>> piece?
>>
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