Hi Roger,
One of the reasons I mentioned substrates are fragile above 1" square, is for
exactly the reasons you mentioned, they are susceptible to micro-cracking (and
not on the scribelines!!). We used 3-3/4" x 4-1/2" x .020" thick laserscribed
snapstrates for most production, and after much study found the culprit to be
two problems, improper laser scribing (we implemented rigid incoming quality
controls on this) and micro-cracking due to profile stress, i.e, too quick on
the ramp up or cool. After these two fixes all of our cracking scrap went away.
Hope we are not scaring you Rick, processing on ceramic really is an easy
process if set-up correctly. Regards.
Jeff Hempton
United Technology Electronic Controls
______________________________ Forward Header __________________________________
Subject: Re: [TN] SMT Assembly on Ceramic substrate?
Author: Roger Massey-G14195 <[log in to unmask]> at Internet
Date: 10/28/98 2:41 PM
Rick,
Similar to Jeff I started life in ceramic substrate assmebly, and
found it to be a pretty robust and generally forgiving system. I
would disagree that anything bigger than a 1 inch square sub is
awkward, I used to work with 2x2 most of the time. Due to the fact
that ceramics are pretty darn hard to melt, there is a massive range
of solders available, but avoid going over 400C as damage to bare die
can be a problem.
One thing to watch for is when snapping substrates, even though
they are usually laser scribed 1/3 of the way through, they can snap
randomly, and dont always follow the scribe line, follow the
technique you use when tiling the bathroom, start at the edge of the
tile, and let the crack propigate along the scribe, laying an alumina
sub flat with a solid edge under the scribe line is fatal, and will
result with a big pile of scrap.
Good Luck
Roger Massey
Materials Technologist
Motorola UK
[log in to unmask]
______________________________ Reply Separator _________________________________
Subject: [TN] SMT Assembly on Ceramic substrate?
Author: "TechNet E-Mail Forum." <[log in to unmask]> at #email
Date: 27/10/98 09:07
Hi,
One of our customers has asked us to look at assembling smt components on
ceramic substrate for them. This is a process that we have no experience
with. If anyone can offer information regarding this process, things to
watch for, etc. it would be greatly appreciated.
TIA
Rick Thompson
Ventura Electronics Assembly
2665A Park Center Dr.
Simi Valley, CA 93065
[log in to unmask]
(805) 584-9858 voice
(805) 584-1529 fax
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