Franklin's answer hits close to the center of the bulls eye. One factor to add is too much air agitation in the copper plating tank. I found it hard to believe, but we could make the mousebites appear and disappear by increasing and decreasing the air agitation. Those defects were caused by air bubbles clinging to the edges of the resist. Steve's photos are on the mark for typical extreme examples of mousebites. I've seen them too. The usual root cause in my experience is improper copper plating tank design/agitation followed by resist developing issues.
Don Vischulis
-----Original Message-----
From: Franklin D Asbell <[log in to unmask]>
Sent: Feb 23, 2006 1:55 PM
To: [log in to unmask]
Subject: Re: [TN] Board etching question for you board shops out there.
Looks like mousebites??? Well, we call them mousebites.
There are a couple main causes, both of them cause poor electrolytic
plating, the first being poor resist develop (for a variety of reasons we've
determined) the second being poor agitation during electrolytic plating
allowing bubbles to remain attached to copper edges. I say remain attached
because it is not uncommon to have gas bubbles in solution, these will
attach to trace edges (where resist and copper connect) and if not removed
will act as a plating resist.
Ragged edges down traces can be caused by resist image, develop, and poor
tin (etch resist) plating, the type and severity of ragged appearance may
provide more information in isolating a true location.
Franklin
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Scott Decker
Sent: Thursday, February 23, 2006 1:34 PM
To: [log in to unmask]
Subject: [TN] Board etching question for you board shops out there.
All you board gurus out there, I have a question for you.
What are the reason(s) I see traces that look like a mouse has
nibbled on the copper to etch it, as opposed to acid etching the copper?
I'm looking at some boards that look like the resist was put on by a
drunk with an old marker pen! The vias are not even round and the SMD
lands have ragged edges also. This shop is off my list from here on out
and going to be rebuilding some boards due to minimum trace problems
too, but can anyone tell me what causes the ragged edges like that? I
understand that specs are looking at averages, which means a high and
low end of the spectrum. I think I know who put the low numbers into the
pot. :-(
Thanks for any info.
Scott Decker
AKA: Padmasterson
Broad Reach Engineering CAE
Ph. 480-377-0400 Ext. 34
FAX. 480-968-4597
Tempe, AZ.
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