Well you have to be commended on your Okie x-section. You did pretty good
with limited equipment. I agree that you did not hit the exact center of
the hole, but the interesting part of the section is not the hole, it is the
surface pad. You hit the surface pad just fine.
I believe that these are capped vias. I think you will find that there has
been a secondary plating cycle to cap the via. I think the plated through
via (PTV) was filled, and then there was a secondary electroless and
electrolytic copper plating process to make the cap. Note that the solder
did not flow into the hole.
Lets see if the "professional microsection" bears out my suppositions on
this construction.
Good job.
Paul Reid
PWB Interconnect Solutions
-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]]
Sent: Tuesday, September 13, 2005 5:44 PM
To: [log in to unmask]
Subject: Re: [TN] raised vias...I did a "Okie" cross-section
Hi All!
I have a local shop here do a lot of cross-sections for us, but I couldn't
take
the board over to them until tommorrow. But I was so curious to take a look
at the bumps, or "raised vias", I decided to do what I could, to see what I
could.
We're not set-up to do cross-sections here (that may change in the future),
but I took a dremel tool and got close to where I wanted to look, then
started
using finer and finer grit wheels. Then I used an exacto knife and
carefully
scraped material away until I was able to see how things looked at the
raised vias. This was done under a microscope, and I mean it was done
carefully.
I know it's not as good looking as what a real cross section would look
like,
but it does give an idea of how things look. Go to:
http://www.stevezeva.homestead.com and look at "Okie Cross-section".
I still don't know why I have the bumps...they look like they're solid
copper.
Kind regards,
-Steve Gregory-
Senior Process Engineer
LaBarge Incorporated
Tulsa, Oklahoma
(918) 459-2285
(918) 459-2350 FAX
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