Abd ul-Rahman Lomax wrote:

> At 02:04 PM 9/1/01 -0400, Mike Reagan wrote:
> >I doubt if you will  find a decent board house that is willing to fabricate
> >poygon pours on internal layers.....notice I said "decent"  Talk to some
> >manufacturing engineers to find out why this is frowned upon
>
> I suspect that this is overstated. Fabricators may not want to produce
> copper-heavy layers that are asymmetrical in the stackup, because of
> potential warping.
>
> But using a copper pour in lieu of a negative plane (presumably balanced by
> another copper-heavy layer should not be any additional problem, especially
> if dead pad removal is used with the photoplot.
>
> By the way, I'd really like to know more about the warping allegedly
> produced by asymmetry. Has anyone actually seen this and verified that the
> asymmetry was the problem? I have a little trouble imagining a few mils of
> very ductile copper having enough strength to move the fiberglass around.

I've had some 3-layer boards made by good fabricators, and they came out
quite flat.  I also have had conventional 4-layer boards with pretty well
balanced power/ground inner planes that came out literally looking like
Pringle's potato chips!  Well, maybe I exaggerate just a little, but these
boards
were so severely warped that if you set them on a table, two edges would stick
up about 2"!  later, we started having real problems with their boards, such
that
they would fail after soldering, or as much as 4 years later!  We had to scrap
pretty much everything they made!  So, obviously not a high quality shop with
tight
control over their processes.

Jon

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* To post a message: mailto:[EMAIL PROTECTED]
*
* To leave this list visit:
* http://www.techservinc.com/protelusers/leave.html
*
* Contact the list manager:
* mailto:[EMAIL PROTECTED]
*
* Forum Guidelines Rules:
* http://www.techservinc.com/protelusers/forumrules.html
*
* Browse or Search previous postings:
* http://www.mail-archive.com/proteledaforum@techservinc.com
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Reply via email to