James and Paul, thanks for the feedback. That's exactly what I needed to
know.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Paulus, Jim
Sent: Friday, August 06, 2004 10:46 AM
To: [log in to unmask]
Subject: Re: [TN] Laminate for Lead-free assembly


Eddie.
Yes, plan on using FR4's that are designated as lead-free compatible.
Typical 170C Tg FR4's don't have the intrinsic thermal performance needed --
they were formulated to satisfy the need for lower Z-CTE in high layer
count, thicker boards. But they come up short on thermal stability.
Two tests help to define suitable laminates:  the "6x test" and "Td".

6x is the IPC-6012 structural integrity testing, except the thermal stress
(solder float) is done 6 times instead of 1x (the coupon is floated on 288C
solder 6 times with a stabilization period between floats). Still a lot of
unstandardized variables in the test methodology, however.  Most
conventional FR4's are okay with 1x to 3x, and may go 6x if the solder temp
is 260C.  But few will consistently hold up after 6x at 288C.

Td is Thermal Decomposition Temp.  Sample is subjected to a programmed temp
ramp in a Thermogravimetric Analyzer. At the temp that the sample loses 5%
of mass is defined as the Td.  FR4's of 130-140Tg run around 290-300C;
160-170Tg run around 280-290C (see the problem?);  FR4's formulated for
lead-free etc will run 330-340C.  Note: testing has shown that these FR4's
also perform better for CAF than the other flavors.

jim


---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------