Pete just described key features that are very close to IPC-4101/126. This is one of the newer materials that IPC added to 4101 in the last revision
Another key product feature included in the /126 slash sheet is time to delamination, varying by the test temperature, but a good laminate should be able to pass 30 minutes at 260C before delaminating. A good off-shore supplier will know and understand the IPC specifications.
Matt Byrne
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Pete
Sent: Thursday, November 08, 2012 11:18 AM
To: [log in to unmask]
Subject: Re: [DC] PCB Material for Lead-Free RoHS
Kitty,
If this is s through hole board that will see one excursion through the wave, you can probably get away with the old 140Tg material ina RoHS complaint form.
Tg as a spec is so old school now! Some of the RoHS complaint 170Tg materials actually degrade to 130 and below after the first heating cycle.
You need to also spec Td, and Z axis expansion. And some multifunctional epoxies required to meet these specs can vastly increase the risk of cathode-anode failures (CAF). So specify CAF resistant epoxy, or specify non-dicyandiamide epoxy (this is a common CAF resistant type)
So if your boards will be reflowed, especially if they will see more than one thermal cycle, try these specs:
LAMINATE MATERIAL SHALL BE IN ACCORDANCE WITH IPC-4101, EPOXY-GLASS LAMINATE, NON-DICYANDIAMIDE, NEMA GRADE FR-4, FLAMMABILITY RATING: UL 94V-0.
MINIMUM Tg (DSC) 170
MINIMUM Td (TGA) 330
MAXIMUM Z-AXIS EXPANSION 25C-260C 4% (you can alterrnately specify CTE, expressed as ppm/C)
And perhaps most importantly, if you are buying fabs overseas, make sure you use a good shop, don't just broker the boards. Some have been known to completely ignore your specs and use whatever they can get cheapest. Cheap isn't inexpensive when your yields drop and failures increase due to "cheap" fabs. (Unless you are building "throaway" products)
Pete
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