Rich,
To emphasize Jorge's first point: As small the component is, as sensitive it
is to layout problems, regardless of specific problems of manufacturer,
product line or production batch.
Take a good look into the PCB design: Are the connections to the component's
pads symmetrical? Isn't one pad connected to massive conductor or layer,
while the other one is not? Aren't the conductors connected to the pads in
opposite directions, causing the component to rotate during the reflow?
We've experienced such layout problems, and PCB revision solved them.
Regards
Ofer Cohen
Quality Assurance Manager
Seabridge Ltd.
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Wednesday, March 19, 2003 23:12
To: [log in to unmask]
Subject: Re: [TN] Panasonic Film Chip Capacitors and SMT Reflow
Rich,
Once in a while there is always somebody having problems with these
components. Personally I've ran into problems with Panasonic plastic film
caps a couple of times, the first time almost three years ago. The problems
you are experimenting are very typical, I'd check four things:
1. Make sure the foot print matches what's recommended by Panasonic. These
components are very light weight and tend to tombstone if foot print is not
appropriate.
2. If I remember two to three years ago Panasonic released an "X" version
of the component. This is suppose to be improved for SMT operation/Reflow
process. You should look into it, maybe that by itself resolves your
problem.
3. The version "B" of the plastic film caps. seem to have some sort of
contamination on the leads that causes tombstoning. This contamination is
either the dielectric bleeding out or a resin. The bottom line is whatever
Panasonic did, the "X" version seems to solder better.
4. And the last recommendation. I'd implement a soak oven profile, that way
you let the board reach a thermal equilibrium before liquiduos and thus
eliminate/diminish the tombstoning or solder opens. We actually use this
type of profile when we have tombstoning concerns.
Hope this information is useful,
Jorge Rodriguez
Process Engineer
Varian Electronics Manufacturing
E-mail: [log in to unmask]
-----Original Message-----
From: Rich Lasko [mailto:[log in to unmask]]
Sent: Wednesday, March 19, 2003 1:51 PM
To: [log in to unmask]
Subject: [TN] Panasonic Film Chip Capacitors and SMT Reflow
Good afternoon everyone,
I am currently reviewing a tombstoning problem that we are having with the
capacitors listed below. We are seeing this problem on two separate
electronic assemblies but only with this component style. We place 40 caps
per array and approx. 3 - 5 of them tombstone. Both assemblies go through
the SMT process and they both are using a Panasonic ECH-U1H152JB5 and
ECH-U1C153JB5 film capacitors. The placement of the capacitors pre-reflow
is centered correctly between the pads. But of course post reflow -
tombstone!
Any thoughts, ideas, or experiences with this part would be helpful.
Thanks in advance for your help.
Rich Lasko
Badger Electronics
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