> We have experienced a random problem with three or four parts relative to rim
> voids.
> 
> In some cases it was part of the lot and in others it was the whole lot. 
> 
> They have been partial, full, top and or bottom. (no consistency) 
> 
> They are typically one to two mils down from the surface copper and one to
> three mils in height. 
> 
> They are not specific to any hole size. 
> 
> We use Dupont APG715 Dry Film, and develop on a Atotech/Chemcut horizontal
> system using Potassium Carbonate.
> 
> I would appreciate any suggestions, as to the cause.
>
--------------------------------------------------------------------------- 
One possibility is that there are oxide stains in the holes. If dry film is left 
too long after lamination it will flow into the hole and coat the inside of the 
rim. If the copper is oxidised then it is likely to form a bond which will not 
develop off. A similar problem occurs with oxide stains on the surface.

If you are experiencing tenting break down this would indicate too long a delay 
after lamination before exposing and developing. Keep the delay to a minimum and 
concentrate on the pre-cleaning prior to lamination. If you use wet brushing, 
try a 5% sulphuric acid dip or spray to remove oxide stains prior to brushing. 

Regards
Paul Gould
Teknacron Circuits Ltd
---------------------------------------------------------------------------
|     EMail [log in to unmask]                                           
---------------------------------------------------------------------------