Hi Mate,

it worldwide praxis to make copper foil 10% below its weight/thickness.
There reasons are quite simple. Both parties are happy. The Cu maker can
make 10% more in the same time and a customer gets 10% more area. It's a
win/win situation. It's also within IPC standard.

It doesn't work as well for 18µ, since it's more difficult to control. If
your consumtion is large you can ask them to make it exactly 35µ - or
whatever you need.

regards

Jens Behrens



>We are facing a perpetual problem with the supply of copper foil thickness.
>
>The vendors are allway sending material thinner than the standard. This
>cause, after the chemical processes of manufacturing, a copper layer below
>the limit acceptable by the customer.
>
>As an example: The metric equivalent for 2 oz. is 610 grams per sqr m. The
>10% tolerance  allow thickness between 549 and 671 grams.
>
>One of the suppliers admit that he supply material between 550 and 580
>grams (which is -10% to -5%).
>
>The following are quotes from his letter:
>
>"This is common practice, indeed all of our customers use the typical range
> of 550 to 580 grams per sqr m."
>
>"I can assure you that the material produced at the lower substance weight
>perform exellently with no detrimental effect for the reduced substance
>weight".
>
>The same problem exist, as well, in laminates.
>
>Our practice is that the copper weight is usualy better in 0.5 oz but start
>to be marginal on heavier weight.
>
>I will appreciate your practice and comments.
>
>
>Hillel Dzigan - Quality Manager
>Eltek Ltd.
>Phone +972-3-939-5022, Fax +972-3-930-9581
>P.O. Box 159, Petach-Tikva 49101, ISRAEL

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