Howard

I presume by 3,5 mil, you mean 0,0035", equivalent to about 80 micrometres. Putting 250
V across this, with or without mask, gives a voltage gradient of about 3000 V/mm which
is HORRENDOUS. A typical acceptable voltage gradient without mask is about 100-150
V/mm, maybe double that with mask, if all the best conditions are united. If your
substrate has absorbed any humidity (and it is likely that it will have done), you will
be pulling apart any ionics in the material. At the best, you will damage it. At the
worst, it will simulate an arc welder. Please don't do it.

Brian

Howard Lin wrote:

> Hi TechNetters,
>
> We do some testing  of  bare board right now.  Can anyone point out what
> different between board with solder mask and without solder mask  on
> electrical testing process? If we apply 250 voltage on 3.5 mil spacing
> pattern , will it damage electrical character? Is there copper migration
> occuring during 250 voltage testing?
>
> Howard Lin
>
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