Julie,

90% of our power supply boards have copper thickness of 2oz/ft^2. In some
occasions we need thicker copper at the expense of the resolution in circuit
width and spacing. We don't see the through-hole plating thickness is an issue
as we fill the vias with solder anyway. To avoid overheating traces, we design
the circuit width to meet IPC-2221 (or IPC-D-275). In some high power density
designs, IMS (insulated metal substrate) are used.

K.K. Chin
Artesyn Technologies
Fremont, CA
http://www.artesyn.com




Julie Dixon <[log in to unmask]> on 11/03/99 07:49:16 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to
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To:   [log in to unmask]
cc:    (bcc: KK Chin)

Subject:  [TN] Power Supply PCB's




Dear Tech Net,

Is there a standard for manufacturing power supply boards? Such as weight of
copper foil for base laminate, amount of copper to be plated on the surface
and
in the plated through holes? Our application is just double-sided PCB's.

Years ago a customer had problems with a power supply board which cooked a
trace. To correct the problem they asked our company to plate their panels
with a minimum of 2 mil in the holes and on the surface. The design is fairly
tough with isolated holes and to get a minimum of 2 we have to plate the
isolated areas up to 3. This causes a myriad of problems with other
processes. Dry film is trapped and practically impossible to remove
completely, thus we have shards- causing shorts ultimately. We have problems
printing the LPI and leaving LPI in the holes.

It seems starting with a base material of 2 oz copper and plating the holes
up to 1 minimum, giving 3+ on the trace would be ample. Starting with 2 oz
and plating up to
2 mil, giving 4+ on the trace makes the boards virtually impossible to
process
effectively. Is it important to have the 2 mil in the hole on a power supply
board?
Or is a problem more likely due to trace thicknesses?

Thanks for your time.
Julie Dixon

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