[log in to unmask] wrote:

> Yeah, but European's don't work in ounces. They use liters and grams and
> meters. Of the folks I've talked with over there, some had a vague idea
> that sometimes oz per sq.foot was used to specify copper thickness, most
> just looked at me funny (maybe that had nothing to do with that...).
>
> I like the KISS rule. But I'm operating in an enviornment where you call a
> 'fire' a 'severe thermal incident'. And where... never mind, I don't wanna
> get started.
>
> Thanks for the input,
> -Chris
>
> ======
> Board shops talk in ounces and we should also. I spec finished and min hole
> plate.
> Board shop figures out its on comp process to achieve product. IPC doesn't
> pay for the boards, we do.
> The more open it is for different fabrication processes the better (lower
> cost). A good design rule
> most have forgotten is the KISS rule. "Keep it Simple Stupid"
>
> Randy Jackson
> Design Center Manager
> DFW Test Inc.
> Phone (972) 231-1094
> Fax (972) 231-1895
>
> "This e-mail message is intended only for the use of the named
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Hi Chris,

We design for both ESA & NASA among others and in many cases have to resort to 2oz tracking
for our power boards.  The following spec was created after discussions with each of our
board manufacturers:

Metallization.
The base copper thickness for the outer layers shall be 18microns.

Plating.
Copper:  The minimum purity shall be 99%.  For a board specified as 35um copper, the
additional thickness on the surface pattern shall be 25 to 45 microns.  For a board specified
as 70um copper, the additional thickness on the surface pattern shall be 52 to 72 microns.
The copper thickness in the plated-through holes shall not be less than 25 microns.  After
solder levelling, a minimum thickness of 1 micron is allowable.  The minimum thickness after
levelling shall be 8 microns in the centre area of the conductor or hole.

This seems to work well for us.

Hope it helps.

David Hill
Mullard Space Science Laboratory
Holmbury St.Mary
Dorking
UK

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