David please,
send to me a soft copy.
Best regards and many thanks.
Vittorio Sirtori
Material Engineer
Packaging Technology Development
Dpt :476 - Tel : +39 039-639 5253 - Fax : +39 039-639 5015
Celestica Italia srl - Via Lecco 61 - 20059 Vimercate (MI) Italy
e-mail [log in to unmask]" target="_blank">http:[log in to unmask]
David Suraski <[log in to unmask]>@IPC.ORG> on 05/31/2001 07:04:24 PM
Please respond to "Leadfree Electronics Assembly E-Mail Forum."
<[log in to unmask]>; Please respond to David Suraski
<[log in to unmask]>
Sent by: Leadfree <[log in to unmask]>
To: [log in to unmask]
cc:
Subject: Re: [LF] What is lead free...
I agree with Doug that the approach of utilizing a lead-free alloy with
tin/lead coated parts as a first step in lead-free processing is being
considered/taken by many. Unfortunately, this is an approach that could have
negative results for some assemblies.
Unfortunately, in the past the presence of lead in lead-free alloys has been
presumed to be acceptable. The logic behind this often was that tin and lead
are soluble in a lead-free system. However, what has been overlooked is that
the intermetallic crystalline structures in lead-free systems are not soluble
and will precipitate at lead boundaries. Thus, when using a lead-free alloy to
solder to Sn/Pb coated component leads, Pb can actually create voids in the
solder joint that can result in joint failure.
To avoid problems related to this, the most prudent course of action is to
eliminate/reduce the lead-free transition period to as short as possible. In
other words, when a company implements a lead-free solder alloy, it should also
implement lead-free component terminations and circuit board coatings. If
these above guidelines are not followed, the reliability of the solder joint is
risked.
We've just completed a paper discussing the dynamics of this and showing
real-world examples of failures caused by lead contamination of lead-free
solders. This will be presented a Nepcon East/SMTA Boston this June, but if
anyone would like to receive a copy of the paper before hand I'll be happy to
send one along at your request.
PS- I'm not advertising here, nor am I suggesting that anyone SHOULD go
lead-free- just offering some research to the community!
Best regards,
David Suraski
AIM
T: 800-CALL-AIM / 401-463-5605, F: 401-463-0203
www.aimsolder.com
----- Original Message -----
From: Romm, Doug
To: [log in to unmask]
Sent: Thursday, May 31, 2001 12:36 PM
Subject: Re: [LF] What is lead free...
Greg,
You will probably get different inputs but here's mine.
Many OEMs are stating that they will implement 'lead-free' in a staggered
approach. The order of priority will be
First: solder materials
Second: printed circuit board finishes
Third: components
This is based on the % contribution of SnPb of each of the subsets (solder, pcb
finishes, components) to the total solder joint (I believe).
This approach is also being reflected in some end users roadmaps which show the
requirement for 'high-temperature' capability of components and pcbs most
immediately and then 'lead-free' as a follow-on step. This timing sequence is
based on the fact that OEMs will convert to lead-free solders first (which may
have a higher reflow temp requirement) and then will follow with lead-free PCBs
and components.
The goal (of those who choose to pure lead-free) is total lead-free in the
entire system, but I believe the staggered approach is being followed by many.
Doug Romm
-----Original Message-----
From: Greg Vance [mailto:[log in to unmask]]
Sent: Thursday, May 31, 2001 10:46 AM
To: [log in to unmask]
Subject: [LF] What is lead free...
Silly question, what defines lead free? Does this imply that there will be
no lead in the assembly or we will use no lead solder, but PCB finish and
some/all of the components may have SnPb plating on them... get my point?
I ask this from the perspective of:
1) printed circuit board finishes
2) components
3) solder materials
Greg Vance
Rockwell Automation
(330)487-6036
---------------------------------------------------------------------------------
Leadfee Mail List provided as a free 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 delivery of Leadree for vacation breaks send: SET Leadfree
NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases >
E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
---------------------------------------------------------------------------------
---------------------------------------------------------------------------------
Leadfee Mail List provided as a free 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 delivery of Leadree for vacation breaks send: SET Leadfree NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------
|
