Hi All!
Thinking about things further, even though I don't have absolute published
lab data to share, I don't think there's any difference between the solder joint
reliabilty between a concave and convex chip resistor termination. After all,
neither styles provide for any compliance at all. Neither style can be
compared to a "Leaded" component whatsoever.
The solder joints are formed based on the solderable terminations available
to each style. The convex style has quite a bit of area for solder to wet to,
and why it is so sensitive to placement and solder volumes...any slight
variance in those aspects create defects that have to be reworked.
The concave style has clearly defined terminations that are separated by
non-solderable material that will allow slight placement variables and
self-center, or slight solder volume variables and avoid bridging, and still reflow to a
sound, defect free joint.
The part drawings that I've seen, have shown that the terminations are
slightly different than the LCCC castellations from the past...similar, but just a
bit different.
On the ones that I've seen, the solderable termination extends for a bit
outside the "Half-moon" shape of the castellation, which will add more volume to
the joints than maybe old castellated joints would enjoy...maybe I'm wrong
about that.
I see LCCC's still being used in assemblies that we build here...high-rel
stuff at that. Pin count doesn't ever exceed 32-pins, but from my view, LCCC's
with castellated terminations are still being used quite regularly.
I can't imagine that something as so small as a 1206 chip resistor network
would suffer from any solder joint reliabilty issues due to CTE mis-matches
between the substrate and the part...no matter was the substrate material was.
-Steve Gregory-
Hi Werner!
What I was referring to was exactly that...the terminations look like the
kind that are on LCCC's. But with the small size of these chip resistor networks,
does the same kind of solder joint reliability problems apply that large
LCCC's had?
-Steve Gregory-
Hi Siegfried,
Sounds like you are talking about a component reminiscent of the 'old'
castellated leadless ceramic chip carrier--if so, you will revisit the solder
joint
reliability problems experienced in the early 80's.
What is the size of these arrays?
Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com
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