Joseph ,
The measuements were performed on through hole pads , not on ground areas .
Points of measurements were taken based on visual inspection . On some part
of the pad ( 30 degree ) we saw mat spot and the measurement was taken from
this kind of spots . On another spots on the same pad we got higher
thickness and normal ratio tin/lead .
 I would not think , tkat this is result of underneath copper quality ,
since after re-dipping in HAL the " thin " spots are not on the same location .
We do have problem with uniformity of HASL coverage . I am just wondering if
there is logical explaination for such composition of the solder . According
to all theories concerning ICM I would expect to low measurements of tin
concentration on the surface due to tin consumed by ICM and excess of lead
left on the surface .


At 11:59 17/02/99 -0500, you wrote:
>
>
>It would not be at all unexpected to observe a higher relative
>concentration of tin in an area determined to have a  "thin" HAL deposit.
>The XRF is responding to the ratio of tin to lead, and given you are
>approaching the copper/solder interface, and more specifically the
>tin/copper interface, it would be naturally preferential to tin
>concentration.
>
>Sounds like you are within expected conditions, other than the thin solder
>deposits. May I assume they are on larger ground areas? There is a direct
>correlation between deposit thickness and area size under given conditions
>
>Hope this helps!
>
>Joseph Webb
>TET/Halco
>
>
>
>
Edward Szpruch
Eltek Ltd - Israel   Tel :  972 - 3 - 9305050 , Fax : 972 - 3 - 9309581
Sgoola industrial Zone , POB 159 , 49101 Petah Tikva , Israel
e-mail :  [log in to unmask]

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