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December 2014

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From:
Mike Fenner <[log in to unmask]>
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Date:
Sat, 13 Dec 2014 19:07:37 +0000
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My experience of Rogers High Frequency substrates is limited to my time in
laser cutting some time ago now. We found them "dimensionally variable"
would be a polite way of expressing it. Each board had to be manually and
somewhat arbitrarily aligned to features before processing. I think this
variability is attributable to the unstructured felt like construction (as
opposed to the fixed weave pattern in conventional FR4). I seem to recall
also they were moisture sensitive.
So I don't think its just ENIG - its just anything.
Hope this little snippet helps.


-- 
Regards 
 
Mike 
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: Friday, December 12, 2014 1:19 PM
To: [log in to unmask]
Subject: [TN] ENIG causes shrinking?

One of our suppliers sent us a batch of boards that have a feature
registration shift. The laminate is Rodgers RO4003.  Has anyone ever heard
of the ENIG process causing this kind of shrinkage?

		" We measured all the panels after etching on the X-ray
machine for scale and shift using 4 etched targets on four corners of the
panel. After these 4 targets are measured top and bottom simultaneously,
program calculates shrink, stretch and top to bottom registration.

		For the last batch of panels processed we tried dialing in
the scale factors on LDI to get the pad features to nominal. we couldn't get
it to nominal but were slightly short about .3 mils per inch in both X and Y
from nominal. By doing the math it was determined it will still be within
spec.  All these measurements were done after etch before ENIG finish.

		After the panels came back we didn't measure them, went
straight to rout and shipped to RDIS.

		Since the boards are still failing for TPD after all these
precautions, Only other variable is the material shrinkage after ENIG
process. 
		We had few panels of part numbers that were not laser cut
yet after ENIG. All these panels were measured after etch before sending it
out to ENIG and they were slightly long about .3 mil per inch. I then
measured the same panels (after ENIG) today late evening  and they were
right at nominal which means they shrunk by about .3 mil per inch during
ENIG process.

		The batch of boards that you have failing for TPD tolerance,
were short by about .3 mil per inch before going to ENIG and shrunk
additional .3 mil per inch after ENIG. They were about .6 mil per inch
shorter than nominal. The board length at about 5 inches in the long
dimension makes it about 3 mil short in long axis and .5 mil in short axis
there by failing the TPD tolerances."

  


Guy Ramsey | R&D Interconnect Solutions | Process Manager |
[log in to unmask] | Mobile:  610-349-2519 | Office: 610-443-2299 | 
1660 East Race Street  | Allentown, PA 18109 USA | www.rdis.com



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