Hi James,
Given the precarious position PCB laminates have been put into by RoHS, your position is appropriate. Fillers do indeed change properties, most notable thermal expansion, for the better, but may engender unwanted side-effects like higher brittleness or propensity for cohesive delamination.
Before changing from a material that works to a new one, I would strongly recommend a trial-run [with coupons] that can be put through all the manufacturing steps intended for your product.
If you want more information on all of this, I would recommend the White Paper [more details below] I have developed that makes recommendations as to specifying PCBs so they can reliably survive Pb-free assembly processes.
Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
Engelmaier Associates, L.C. developed a White Paper titled: "WHITE PAPER REPORT: Recommendations for PCB FAB Notes and Specifications in Printed Circuit Board Drawings for SnPb and Lead-Free Soldering Assemblies, the Qualification of PCB Shops and Activities to Assure Continued Quality."
As indicated by the title, in this report recommendations are made regarding appropriate specifications and ‘FAB Notes’ on drawings for printed circuit boards (PCBs), general procedures to qualify PCB shops and to assure they would be producing PCBs of good quality, and testing procedures to verify quality and reliability. It contains examples—one for SnPb solder assemblies and one for RoHS-compliant Pb-free solder assemblies—of ‘FAB Notes’ serving as general specifications on PCB drawings being much more specific than IPC-4101C, a basic questionnaire for new PCB shops to be qualified meant as a supplement to IPC-1710, as well as recommendations for ongoing activities to assure that qualified PCB shops maintain the quality of the PCBs produced by them. All the recommendations are fully discussed, carefully researched and referenced.
The cost of the report is $495.-; it will be delivered as a pdf-file immediately upon receipt of a check, money transfer or purchase order. While the price may appear high, all the feedback I have received tells me that my customers think it money well spent.
Updates will be sent automatically and at no additional cost—Version v.09 with some 50 pages and 92 references is currently shipping; and work on update version v.10 has begun.
-----Original Message-----
From: James Liddle <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, Jan 4, 2010 5:51 am
Subject: [TN] PWB Laminate Specification
Hello
I'm looking for feedback with respect to writing a PWB Laminate Specification
that is tight enough to ensure consistent PWA performance and reliability; but
which is also flexible enough to ensure good 'Manufacturability'.
Up until now our Fabricator has used Isola IS410, which is a Phenolic Laminate
without Fillers that conforms to IPC-4101B Specification Sheets 124 and 129.
I'm quite happy to approve alternative manufacturer equivalents which have the
same composition and conform to the same Specification Sheets; ITEQ's IT-180
for example. However, our Fabricator has a preference for a Phenolic Laminate
with Fillers, that conforms to IPC-4101B Specification Sheets 99 and 126.
Am I being overly cautious if I deny their request for change? Can anyone
report any adverse experiences they have had when making this change, that I
should be aware of? Are there any differences in the properties or
characteristics of the two types of Laminates that I should pay particular
attention to?
Thanks
James Liddle
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