Colleen,
While the Td is important there are other factors at work which my
be more important than if you select 350 or 340 Td. The curves for weight
loss vs temperature for the two materials, at your actual processing
temperature are probably more important.
Considering your boards are that many layers and I don't know the thickness
of the boards, I would also look at the Tg, the T260 (or T288), the Z-axis
CTE and making sure the material is CAF resistant.
Z-axis CTE above the Tg can be critical depending on your boards' thickness.
Regards,
LS
-----Original Message-----
From: Salvaggi, Colleen [mailto:[log in to unmask]]
Sent: Monday, October 09, 2006 10:57 AM
To: [log in to unmask]
Subject: Td in PCB's for lead free assemblies
All,
=20
We currently design boards that are 8 to 14 layers, double sided
assemblies, with both thru hole and SMT. With the number of assembly
cycles that these boards are heated up at is it better to use PCB
materials rated with a Td of 350 or would a Td of 340 work just as well?
Our fabrication shop would like us to relax from 350 to 340.
=20
Thanks,
=20
Colleen=20
=20
=20
Colleen Salvaggi C.I.D.+
Principal PCB Designer
Cantata Technology, Inc.=20
(formerly Brooktrout Technology)
410 First Avenue
Needham, MA 02494
p 781/433-9448
f 781/449-3171
Visit our website at www.Cantata.com <http://www.cantata.com/> =20
[log in to unmask]
=20
----------------------------------------------------------------------------
---Leadfee Mail List provided as a service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Leadfree
To temporarily stop/(start) delivery of Leadree for vacation breaks send:
SET Leadfree NOMAIL/(MAIL)
Search previous postings at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=3D4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
----------------------------------------------------------------------------
---
THIS EMAIL AND ANY ATTACHED FILES ARE CONFIDENTIAL AND MAY BE LEGALLY
PRIVILEGED. If you are not the addressee, any disclosure, reproduction,
copying, distribution or other dissemination or use of this communication is
strictly prohibited. If you have received this transmission in error, please
notify the sender immediately and delete this email. It is the policy of ACR
Electronics, Inc. that no legally binding statements, representations or
commitments (collectively statements) may be made by email. Any such
statements must be confirmed either by facsimile transmission or by postal
mail before they will have legal effect. The sender of this email is not
authorised to commit the company in any way and the addressee is hereby
notified of that fact.
-------------------------------------------------------------------------------Leadfee Mail List provided as a service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Leadfree
To temporarily stop/(start) delivery of Leadree for vacation breaks send: SET Leadfree NOMAIL/(MAIL)
Search previous postings 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 847-615-7100 ext.2815
-------------------------------------------------------------------------------
|
