[SI-LIST] FW: radial cracks around thru-holes in Polyimide laminate - root cause
- From: "Salkow, Steven" <steven.salkow@xxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Mon, 06 Dec 2004 16:37:07 -0800
images download here: http://www.bychoice.com/pcb_cracks.zip
We are asking if any of you have seen radial cracks around
thru-holes like those imaged in a microsectional analysis of a 14-layer
PCB (Polyimide laminate, see attached examples). The specimens were
microsectioned in the horizontal plane. In every image, the cracks run
outward (perpendicular) from the hole wall, they are not randomly
directed. The cracks appear to be partially copper filled indicating
they probably existed prior to the Through-hole Plating process. Not all
layers showed cracks and the crack patterns appear different on
different layers (TBR).
The original problem that lead to the microsection was high
impedance shorts to ground (100's of ohms) on two pins of the installed
connector with hole registration the suspected cause. What came back
were images of these radial cracks, no registration problem. No
definitive proof of any crack as cause for any shorting was determined,
but appears leading.
If anyone has seen this before, what is it, what might be the
cause(s)? (process, material, ?)
What are the probable effects of aging (thermal/humdity) on
crack propagation?
Thanks in advance,
Mike Massa/Steve Salkow
Lockheed Martin
3200 Zanker Road
San Jose, CA 95134
steven.salkow@xxxxxxxx
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