Steve,

Was the crack merely cosmetic or is there potential for wire damage with
the excess potting compound?

Jim Carlson
Reliability/Quality Engineer
Rockwell Collins





Steve Gregory <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
10/29/2004 05:04 PM
Please respond to TechNet E-Mail Forum; Please respond to SteveZeva


        To:     [log in to unmask]
        cc:
        Subject:        [TN] Cracked Cases on SMT Power Inductors from Coil Craft...


Hi All!

I just discovered a problem with some SMT Coil Craft Power Inductors, it's
their MSS1260 series. The problem is that the cases are cracking. I don't
know if any of you have experienced this, or know anything about this
issue, so I thought I would share what I just learned this afternoon. Take
a look at:

http://www.stevezeva.homestead.com/files/CrackedCoil.jpg

We just discovered these on assembled product..naturally :^(

I called Coil Craft and spoke with their Quality representative, and they
said that they are aware of the issue, and have changed their assembly
processes back on September 16th to address the issue.

The reason that the coil cases were cracking, was because they were
filling the entire cavity between the surface of the winding around the
coil, and the inside surface of the case with potting compound. During
subsequent heating, the expansion of the potting compound would stress the
case and cause it to crack. I was told that inductors made after September
16th would only have potting compound in the
corners to allow for expansion.

So if any of you have any of these sitting around in your stockroom, I
wouldn't use them without inspecting them to see if the cavity is
completely full of potting compound.

-Steve Gregory-

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