Bill,
I agree. The volcanic reaction is one form of "popcorning", also I have seen many cases of solderball spewing from broken LPI at the PTH. I am a big fan of the plug then LPI method however where folks must use the via for test (.8 BGA) I love the capped via. That is where only vias are drilled and plated then filled. PTH for component mounting (ie connector) are then drilled and plated; this plating covers the existing vias in a copper cap or also known as Via In Pad: VIP. Thanks for the input, it was a great sanity check.
[By the way Bill, did you get the copy of that Flex presentation?]
Brad
----- Original Message -----
From: Brooks,Bill<mailto:[log in to unmask]>
To: [log in to unmask]<mailto:[log in to unmask]>
Sent: Wednesday, March 14, 2007 12:55 PM
Subject: Re: [DC] One sided issue
Let me see if I understand the implied issue...
If they are tenting the vias on one side I would suggest recommending
another more reliable option to your customer.
We plug the vias with soldermask here rather than 'tent' them for a couple
of reasons... one, a single sided or broken tent is a moisture or chemical
trap and can compromise or damage the board or assembly during assembly
processing or even in storage.
Two, from my own experience, we had a batch of tented boards make it into
assembly with compromised tents, (ones that did not completely cover the
holes on either side) and when we ran the boards through re-flow soldering
we observed in inspection a large number of the vias expelling solder balls
and contaminants from the holes as the heated gasses and moisture inside
them expanded rapidly... (Kind of like little volcanoes)...
We avoid the single sided tents for that exact reason...
Plugging the holes completely is much more reliable and we have not had any
problems since.
Does that help at all?
Best regards,
Bill Brooks
PCB Design Engineer, C.I.D.+
Tel: (760)597-1500 Fax: (760)597-1510
Datron World Communications, Inc.
Vista, California
-----Original Message-----
From: Brad Saunders [mailto:[log in to unmask]]
Sent: Tuesday, March 13, 2007 2:02 PM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: [DC] One sided issue
Hello Folks,
What are the reliability thoughts on a PCB configuration as follows: 013 PTH
via ENIG finish (prior to soldermask) with one side without mask and the
other a dryfilm soldermask. The board is approx .080 thick.
Thanks, Brad
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