Seems to me there is a UL regulation on silver and circuit boards.? I know the immersion silver had to satisfy UL of no dendritic growth.? Anyone on TechNet quote fluent UL?

Denny Fritz


-----Original Message-----
From: John Burke <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, Jul 15, 2009 1:50 pm
Subject: Re: [TN] Silver epoxy



Exposed PWB

John Burke
(408) 515 4992
-----Original Message-----
From: Steven Creswick [mailto:[log in to unmask]] 
Sent: Wednesday, July 15, 2009 10:29 AM
To: 'TechNet E-Mail Forum'; John Burke
Subject: RE: [TN] Silver epoxy

John,

We did do not experience electro-migration problems in a hybrid or
multi-chip module so long as long-term hermeticity was maintained - to keep
the moisture out.

From my perspective, PEMs - plastic encapsulated modules do not possess
long-term hermeticity characteristics [am sure to ignite a firestorm with
that], but they certainly do well in the short-term, and under reasonable
environmental challenges.  They delay the ingress of moisture - do they
delay it long enough for your application is the question.  Optically clear
molding compounds tend to be worse because - 1) there are no expansion
modifiers present [dah!, it's clear], 2) they just don't have the ruggedness
of the filled versions ...

Therefore, whatever you do to delay the ingress will be to your benefit.
Paralyene, some of the new hydrophobic plasma coatings, careful selection
and processing [storage, handling, molding and post-cure] of the mold
compounds, plating on the lead-frame or PWB.

Depends on your requirements....  just a matter of time & voltage, it would
seem.


You did not really say whether your application was over-molded, exposed
PWB, etc...

Steve



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: Wednesday, July 15, 2009 1:09 PM
To: [log in to unmask]
Subject: [TN] Silver epoxy

 

Many years back (too many) I was working on silver epoxy connected hybrids
for high reliability applications.

 

I seem to recall that silver migration is a definite issue. Does anyone have
any rules for mitigating this risk such as design clearances between pads
etc?

 

Best regards,

 

 

John Burke

Director of Operations

 



http://www.optichron.com

4221 Technology Drive

Fremont, CA 94538

 

Cell (408) 515 4992

Desk (510) 249 5233

Main (510) 249 5200 

 


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