Hello Edward,
From time to time we also see the same type of defects. It tends to be batch related.
The defects has a resistance from 10 kW to 10 MW.
In microsectioning of the boards I have seen, what looks like a mist of copper around the drilled holes.
I think the mechanism is called "vicking" and is related to drill-parameters.

In the next period of time I will try to registrate the defect and compare it to the drilling-parametre.
I will also check if we have problems with residues in the black oxide.

With best regards
CHEMITALIC A/S

Jan Thuesen


-----Oprindelig meddelelse-----
Fra:    Eltek Ltd. - Process Engineering [SMTP:[log in to unmask]]
Sendt:   5. maj 1998 09.04
Til:    [log in to unmask]
Emne:   [TN] High resistance internal shorts

Hi Technetters !
During the past period we made a lot of improvements in our production to
reduce the scrap due to internal shorts .  At this moment 90% of internal
shorts are " isolation shorts " , it mean high resisitivity .
Some of this shorts were located and we found  unidentificed spots in the
laminates. The spots are located under the conductors ( laminate side ) ,
they  have irregular shapes and are very thin . Such spots are bridging two
adjacent conductors . Such spots are not result of unetched copper since
they are running deep into the laminate ( more than 25 microns ) .
I will appreciate comments on this problem via technet or to my private e-mail .
Best regards


Edward Szpruch
Eltek Ltd - Israel
Tel  972 3 9395050
Fax 972 3 9309581
E-mail :  [log in to unmask]

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