Hi John,

As long as the tin plating on the inner layers is less than 5 microns,
You may be safe but, not is not guaranteed. If the thickness is than
5, the tin will melt during the (reflow) excursions and the bond
strength to the prepregs will collaps to zero. With thicker layers the
solder can be pressed out of the board as globules where the inner
layer sees the cutting sides. Even hole platings can be damaged. So
beware of the tin thickness of inner layers.

Regards,
Peer Langeveld
Consultant Soft Soldering Processes
5502 VH 8  the Netherlands


2006/8/22, John Parsons <[log in to unmask]>:
> We are quoting on a PCB which has some unique, at least to us, manufacturing
> requirements and I was hoping that someone might be able to provide insight
> on some of the challenges we foresee.
>
>
>
> There are many hurdles to clear with this part, two of which are;
>
>
>
> -          This 3 layer PCB must have immersion tin plating on all
> conductors, inner and outer layers.  Does anyone know if the pre-preg will
> successfully bond to the immersion tin plated surfaces?
>
> -          The outer layers of this part will have areas of selective gold
> plating, 50u",plated directly to copper, no nickel interface.  Are we likely
> to see problems with bond between the gold and copper?
>
>
>
> John Parsons
>
>
>
>
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