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 ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________