The tin used for etching resist is not compatible with a final finish.
As an electrolytic finish this tin readily oxidizes and has very poor
wetting characteristics - even though most will advertise excellent
solderability characteristics.  Immersion tin systems can be used as an
etch resist, but the survivability of these finishes to the final
resting place as a solderable finish is remote.  

We use Shipley Ronastan EC and it works well for our applications.

Jeffrey Bush
Director, Quality Assurance and Technical Support

VERMONT CIRCUITS INCORPORATED
  76 Technology Drive - POB 1890
    Brattleboro, Vermont 05302
      Voice: 802.257.4571.21 Fax: 802.257.0011
           http://www.vtcircuits.com
 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Fineline Circuits,
Inc
Sent: Friday, October 14, 2005 10:20 AM
To: [log in to unmask]
Subject: [TN] Electrolytic Tin Plating

Hi Technetters:
Now that Leadfree is here or close to, we would like to change the
electrolytic tinlead plating tank to electrolytic tin tank.
I would like to know if the other fab houses have done this and if so
which
vendors tin chemistry has a wider window of operation. Are they seeing
any
tin whiskers/sliver problems etc..especially if the boards are stored
for
few months.
Also it is my understanding that you can mask over this plated tin since
it
does not flow. In this case you can totally avoid stripping the tin and
tin
levelling.
We currently do offer other finishes including electroless tin ,
immersion
nickel/gold, silver....
If there are other consideration in making this change I would
appreciate
your input.
Franklin, like you I would like to see more fab houses participating but
I
would like to remain with technet.
Thanks

Sona Sitapara
Fineline Circuits Inc.

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