WOW! That is all well and good....but what do you do to acheive controlled
impedence?
Barbara J. Burcham, CID
PCB Designer
Fairfield Industries
Sugar Land, TX 77478
281-275-7687 Work
281-275-7550 Fax
[log in to unmask]
-----Original Message-----
From: Glenn Pelkey [mailto:[log in to unmask]]
Sent: Thursday, February 10, 2000 3:53 PM
To: [log in to unmask]
Subject: Re: [TN] PREPREG AGAIN
Hi all,
I worked for a laminate manufacturer about four years ago. So,
things
may have changed, but here's how we addressed this.
The issues pointed out are correct. There were too many factors in
lamination to get a good, consistent predictor at the PCB fabricator site by
testing at the laminate mfr. When you multiply press type, pressure, heat
profile, board construction, vacuum, load, lag, humidity, age of prepreg,
and
multiply that by the number of customers, it just gets even harder to
specify
a number. This is especially true when you're producing what's considered a
"Standard" product. So, pressed thickness was never specified, but it was
listed with a "Typical" value range. We also performed "Scaled Flow
Thickness" measurements periodically which was mentioned in a previous post.
(PC-TM-650, Method 2.4.38) Sometimes, the results from this test would
provide a starting point or early indicator of performance, but still no
guarantee.
The best bet was for the PCB shop to develop a standard panel which
could be run through the process and the results measured. If you had some
correlation to the other factors mentioned, you'd have a better guess at the
final thickness.
Glenn
P.S. Let me know if you need the internet links to the laminate suppliers.
There used to be a couple listening to the Technet.
Brunker Ed <[log in to unmask]> Wrote:
|
| Sorry guys,
| I'm still wrestling with this one.
| Can you give me the thickness of 1080 X 2 after pressing.
| Can we work through the reasons for two suppliers giving different results
| for the same prepreg bearing in mind that not all manufacturers are in the
| western world.
| Does the pressing process have much impact on finished thickness?
| Are there any standards with which to control prepreg production?
| Regards
| Edward Brunker
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