Good afternoon,

I have a peculiar problem I could use some thoughts or theories on:

1)      4 layer flex

2)      All layers 100 micron lines and spaces

3)      Part is electrically tested 3 times at 250 volts - passes

4)      Part goes into a damp heat chamber at 85/85 for 48 hours. Chamber is
turned off and part sits in chamber for approx. 4 hours

5)      Part is taken out of the chamber and allowed to cool for 4 hours (
it is not dried)

6)      Part is tested at 5 volts and very low current for approx. 10
milliseconds and a short measuring 800 ohms to 1.2 megohms develops across 2
tracks always on the inner layers in a small random spot

7)      Failure rate is approx. 2%

8)      SEM/EDX analysis of the failed area shows almost always the same
thing every time - Ca, P, Cl, Fe

9)      The above elements are inclusions/contaminants in the  glue layer in
other words they are in the raw material as received - confirmed by SEM/EDX
and Ion chromatography both by me and by supplier

10)   The Ca and P are used by the manufacturer in the mfg. process. The Fe
and Cl do not show up in scans outside of the failed area.

11)   Size of inclusions/contaminants are in the 5 to 20 micron range

So my question is how does a test of this low a voltage cause this kind of
failure?

Any thoughts /theories are welcome.

 

Regards Steve Kelly

 

Steve Kelly

(416) 750-8433 (work)

(416) 750-0016 (fax)

(416) 577-8433 (cell)

 


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