[SI-LIST] Re: Cu Thickness
- From: Stuart Brorson <sdb@xxxxxxxxxx>
- To: "Andrew W. Riley III" <drew3rdof3@xxxxxxxxxxx>
- Date: Thu, 19 Jul 2007 06:33:35 -0400 (EDT)
Andrew,
Thanks for your answer. Your points make sense. The point is that 2
oz Cu is inappropriate for fine-pitch boards, particularly for large
boards where the final feature size might vary over the
board's surface due to non-uniform etch rates. Right?
Is there a rule of thumb, like trace/space = 10/10 => OK for 2oz Cu,
but 5/5 => not OK? A similar rule for 1oz Cu?
Cheers,
Stuart
On Wed, 18 Jul 2007, Andrew W. Riley III wrote:
> Stuart,
>
> I do not see board warpage being a factor unless there are extreme
> differences in copper layers of the PCB, or the fab house is not reputable.
>
> Coming from the layout side, I have only had complaints from fab houses WRT
> tolerances and extended reliability at 2oz routing layers. At that time it
> was the customer's request and I was able to talk them down with facts
> supplied or easily researched and sometimes a conference call that included
> an engineer specialized in signal integrity with reliable simulation tools.
>
> In an attempt to make this reply short, my experience has been that
> increasing copper weight was not a favorable consideration in those designs.
> Having the backup of an experienced and proven signal integrity expert on
> call was a factor.
>
> Sometimes you gotta bite the bullet and let the powers that be know it's not
> gonna be free.
>
> Cheers!
> Drew
>
> ----- Original Message -----
> From: "Stuart Brorson" <sdb@xxxxxxxxxx>
> To: "Dagmara Avanindra" <dagmara.avanindra@xxxxxxxxx>
> Cc: "SI LIST" <si-list@xxxxxxxxxxxxx>
> Sent: Wednesday, July 18, 2007 5:22 PM
> Subject: [SI-LIST] Re: Cu Thickness
>
>
>> Dagmara,
>>
>>> I would advise staying away from 2 oz copper thickness, espeacially if
>>> this
>>> is a large board.
>>> I have seen alot of reliability issues related to such a thick metal.
>>
>> I would be interested to hear in more detail about what type of
>> reliability issues you have seen. Is it board warpage?
>>
>> Stuart
>>
>>
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