Hey Ted,
It looks like you are about to embark on quite a journey as you
grapple with the RoHS requirements. I wish you well...
I suggest you visit with your favorite assembly engineer and find out
what their PB-free assembly process will require for laminate materials
specifically, Tg, Td, CTE, and CAF resistance. Add the results to all
the other requirements your application requires and look through the
materials listed in IPC-4101B until you find a material or a list of
materials that meet all of the end user's (and the manufactures')
requirements. Once you have a shopping list, check with your favorite
fabrication house for material cost, availability, and any tips they are
willing to offer you.
As a service bureau, we are currently recommending FR-4 in accordance
with IPC-4101B/126 or IPC-4101B/129 for Pb-Free assembly. Our typical
material call-out on a master drawing (fab note) for Pb-Free assembly
may look this:
"PCB LAMINATE MATERIAL SHALL BE SELECTED TO MEET OR EXCEED THE
REQUIREMENTS LISTED FOR IPC-1401B/126/129"
According to IPC-4101B the following material spec sheets describe FR-4
epoxy systems that intended to be suitable for the Pb-Free assembly
process.
/99 /101 /121 /124 /126 /129
Keep in mind that these are only the materials cross-referenced with a
keyword search for "Lead-Free FR-4" and that there are other material
spec sheets that describe materials that would be suitable for the
Pb-Free assembly process such as /26 or some of the polyimides etc...
FYI - There are many different RoHS directives being released by
different governments and entities. They all have similar (but
different) details so be careful when researching your end user
requirements and commercial market requirements. European Union RoHS may
have been the first one but it is not the only one... any more...
Hope this helps to get you started...
Regards,
Patrick Courtade, CID
CAD Manager
7Core Inc
214-347-4274
www.7core.biz
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Klefisch, Ted J
Sent: Monday, August 27, 2007 1:19 PM
To: [log in to unmask]
Subject: [DC] base materials for lead-free PCB's
Hello Designers,
I work for a medical OEM. We will soon be producing RoHS-compliant
PCBA's. I am not sure what exactly to include in the fab notes to
specify the PCB base materials for compatibility with lead-free assembly
temperatures.
For pre-RoHS boards I have included a note on the fab drawing that
specifies "FR4, copper-clad laminates" plus board thickness and UL
rating requirements. Our boards are generally .062" thick and 8-layers
or less. As far as I know, we've always used conventional FR4.
What would you suggest I include in a fab drawing note to assure that
the boards survive the higher assembly temperatures? Is it enough to
specify decomposition temperature alone or should glass transition
temperature also be called out? Td=330C? Tg=150C?
I really appreciate your suggestions and advice.
Thank you.
Ted Klefisch, CID
Covidien
444 McDonnell Blvd.
Hazelwood, MO 63042
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