Valerie

I agree with most of your statements with the excepting of the first. Our
experience was that the thickness of the immersion silver coating was
inversely proportional to the size of the feature.

Best regards

Lee

J. L. Parker Ph.D.
JLP Consultants LLC
(804) 779 3389


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Valerie St.Cyr
Sent: Monday, September 12, 2005 12:31 PM
To: [log in to unmask]
Subject: Re: [TN] Immersion Ag

It's my understanding that larger surface features plate up thicker than
smaller surface with immersion silver ...

Testing and real use experience has indicated that thinner is better,
but up to 40 microinches of immersion silver has been routinely
and successfully used.

Raytheon has done extensive studies on this ...

The IPC task team has also done extensive studies, as have others,
and none of them report any silver migration.

I am not aware of any sunken joints on PTHS with immer. silver; another
aspect is the solder itself - has there been any change in the alloy?

Valerie
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RICHARD FUDALEWSKI <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
09/09/2005 03:27 PM
Please respond to TechNet E-Mail Forum; Please respond to RICHARD
FUDALEWSKI


        To:     [log in to unmask]
        cc:
        Subject:        Re: [TN] Immersion Ag
Ted

majority of shops here in Toronto are depositing from 8 to 19 microinches
silver. and of course the smaller the area on the board - the more it will
plate - if you start hitting the 20 plus range - you have a good chance
for
silver migration on the pads...and so on and so on...

you mentioned sunken solder joints on PTH leads - i'd start looking if
there
is enogh copper in the through holes. underplated copper will cause blow
holes when reflowed.

regards

Rich Fudalewski
----- Original Message -----
From: "Ted Kong" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, September 09, 2005 1:58 PM
Subject: [TN] Immersion Ag

> Hi Technetter,
>
> According to the fab shops, the recommended immersion
> Ag thickness ranges from 5-25 micro inches.  My
> quesiton is whether having thicker immersion Ag (let
> say around 20 micro inches)would cause PTh solder
> joint defects?  Will it cause sunken solder joint on
> PTH leads?  If so, what is causing this to happen?
>
> Thanks all in advance.
>
> Regards,
>
> Ted Kong.


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