Thank you all for your information.
Now, next:
Opens in BGA on Immersion silver.
MICROvoids detected by X-ray on : free pads, ordinary smt joints, BGA solder 
joints (ball to circuit pad location).
BGA rework?
BGA replacement?
SCRAP??????
I fear that the story begins to be similar to the black pad nightmare with 
immersion gold.....
Gaby
----- Original Message ----- 
From: "Dennis Fritz" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, January 28, 2008 8:17 PM
Subject: Re: [TN] Microvoids immersion silver


>I will try to answer each question as you ask them.
>
> In a message dated 1/28/2008 12:32:15 P.M. Eastern Standard Time,
> [log in to unmask] writes:
>
> Dear  Netters,
> Is there a preferred process for immersion silver finish in order  to
> minimize microvoids?
> Immersion silver vendors have a preferred way for fabricators to operate 
> the
> immersion silver line to minimize/prevent microvoids.  Please  understand
> there are more effects than just the immersion silver bath itself.
>
>
> How  do you choose the preferred immersion silver PCB supplier?
> Your board supplier is very interactive in the performance of immersion
> silver boards.  The best plating solution, run poorly by a fabricator can 
> give
> problems and vice versa.  Obtain boards from more than one fabricator  and 
> from
> various bath suppliers.  Probably, the bath vendor has an opinion,  from
> process audits, how each fabricator is obeying the process information in 
> the data
> sheets.  See what works best with your solder paste and wave  solder.
> Wetting balance, dip-and-look, solder spread are all tests that  indicate 
> good
> performance.
>
>
> Which test for bare boards could give the best  information?
> IPC J-standard 003 for board solderability should be a guide for your
> operation.  Do you use international IEC standards?
>
>
> Should I perform a print and reflow test for each batch, followed  by 
> x-ray?
> The print/reflow test is a good idea, with controlled conditions. However, 
> I
> don't think you will see microvoids with X-ray.  You probably need cross
> sectioning to see microvoids.
>
>
> Which tests are the suppliers performing?
> By suppliers, do you mean board fabricators or plating chemistry 
> suppliers?
> This is not a one stop shop. The board shop should be  running process
> controls on their microetch for roughness and silver  immersion plating 
> bath.  The
> plating rate and final thickness are  recommended by the bath supplier, 
> and
> should be obeyed in fabrication. Both shop  and supplier may be running 
> assembly
> simulation and then cross sectioning to see  if there are any microvoids.
>
>
> Thanks,
> Gaby
>
> Dennis Fritz
> MacDermid, Inc.
>
>
>
> **************Start the year off right.  Easy ways to stay in shape.
> http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489
>
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