Interesting viewpoint.
Have to say that I cannot completely agree with the last sentence "I think
there will be few changes required, other than surface finish and
de-composition temp"
In a lot of cases the unit will have to go through a complete proto build
with verification od design intent, it may be a small change but sure can be
a lot of work!!
Most modern high speed designs are working with controlled impedance traces.
Changing the material, means you have to change the stackup, change the
stackup you have to run prototypes to verify signal integrity and original
design intent. If you have one or two boards this may not be an issue.
If you have several hundred designs it will be very draining on the design
and signal integrity group.
Me.......... I believe the theory that Werner Engelmaier proposed that lead
free is al al-Queida plot to destroy Western
civilization by sapping our resources.
John.................8-)
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]]On Behalf Of Richard B.
Smith/AT-Austin/3M/US
Sent: Thursday, November 04, 2004 12:58 PM
To: [log in to unmask]
Subject: Re: [LF] Lead Free and Tin/Lead Combined
Greetings:
My thoughts on PCB compatibility between LF and Pb process:
For changing to LF on current PCB, change to higher decomposition
temperature in the laminate material (330 to 350 C). That will make the PCB
handle the temperatures better for rework too.
I would do that before changing any other layout features on the board and
run some to confirm your current design rules. In some cases you may need
to move vias farther away from pads and component bodys,
Other design changes may be required for pad lay-out, PTH via keep-outs and
thermals depending upon the density of the PCB, and the thermal capacity of
your reflow equipment.
For the most part If the PCB lay- out is done to generally accpted standard
design guidelines, I think there will be few changes required, other than
surface finish and de-composition temp..
Rick Smith
3M Austin
MA/NY DDave
<[log in to unmask]
> To
Sent by: Leadfree [log in to unmask]
<[log in to unmask] cc
>
Subject
Re: [LF] Lead Free and Tin/Lead
11/04/2004 01:07 Combined
PM
Please respond to
"(Leadfree
Electronics
Assembly Forum)"
<[log in to unmask]
>; Please respond
to
MA/NY DDave
<[log in to unmask]
>
Hi Dacia, IPC LF Listservers,
Firstly,
I agree with what AIM's DavidS wrote, since long before DavidS has shown
his experience to us in the Boston area, I have seen similar
microstructures of metal or phase separation that fit the same pattern.
Metals Handbooks by ASM are also a good resource as is the ASM society.
Will it fail, when-what-where, I will leave to my/our failure gurus like
Werner our man Englemair, and Guenter, NPL too,
<Another question:
From my research, I have gathered that current PCBs used for the standard
tin/lead process may or may not be acceptable for lead free processing.
Items to consider when evaluating whether or not these boards are
acceptable
for use include board complexity, rework potential, single vs. double
sided,
etc. The only way to determine acceptability is through process
evaluation.
Is this a correct assumption? Or am I way off the mark here?
YES, you are right.
It all depends on the thermal effects you will reach in the soldering
process and the withstand effects of the materials.
Yours in Engineering, Dave
Y i Engr, MA/NY DDave
----------------------------------------------------------------------------
---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
----------------------------------------------------------------------------
---
----------------------------------------------------------------------------
---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
----------------------------------------------------------------------------
---
-------------------------------------------------------------------------------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
-------------------------------------------------------------------------------
|
