I would not recommend mask over ENIG due to issues with entrapment of
contaminated and possible performance issues in duty cycle.  Early
acrylated LPI had issues with chemical resistance to gold baths,
particularly electrolytic gold and suppliers began producing toughened
materials to resist attach.  I have not heard of this issue in several
years - what type of mask do they use?  

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: Stephen Gregory [mailto:[log in to unmask]] 
Sent: Wednesday, May 11, 2005 9:33 AM
To: [log in to unmask]
Subject: [TN] LPI adhesion on ENIG vs. copper...

Mornin' all you 'Netters!

Gotta question. We're getting a board quoted to buy, and the shop has
come back for some relief on some notes on the drawing that state:

Process Notes:

1. Plate all exposed areas with Electroless Immersion Gold
Nickel 100 microinches thk., Gold 2-10 microinches thk. min.

2. Apply LPI soldermask over bare copper (SMOBC)
Color: Green
Conform to IPC-SM-840, Class H Current rev.
Resizing of soldermask pad clearances may be
required due to suppliers choice of material and/or
process. soldermask clearance for vias to be .004 larger than drill
hole.

The fab house is asking to plate the whole board with ENIG, and then
apply
the soldermask because they say that the ENIG process after applying the
LPI
will make the mask look ugly.

I know the ENIG process can be tough on soldermasks, but I thought that
problem
has already been worked out...

I gues my real question is; is the adhesion of LPI over ENIG any worse
or
better than
SMOBC?

My gut feel is to tell the fab house to comply with the notes on the
drawing, I really
don't want to ask our customer if the fab house can deviate from the
notes
on the
drawing. But on the other hand, I don't want to get a raggedy looking
board
from
them if they don't have their ENIG processes in control...

Kind regards,

-Steve Gregory-
Senior Process Engineer
LaBarge Incorporated
Tulsa, Oklahoma
(918) 459-2285
(918) 459-2350 FAX
__________________________________________________________________
This message may contain information that is privileged and confidential
to
LaBarge, Inc.  It is for use only by the individual or entity named
above.
If you are not the intended recipient, you may not copy, use or deliver
this message to anyone.  In such event, you should destroy the message
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Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
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