I would like a copy of your paper.
Al Cash
Northrop Grumman ESSS-DSD
M/S H- 6185
600 HIcks Rd.
Rolling Meadows, Il 60008
E-mail: [log in to unmask] <mailto:[log in to unmask]>
Tel: 847-259-9600 X-6764
-----Original Message-----
From: David Suraski [mailto:[log in to unmask]]
Sent: Thursday, May 31, 2001 12:04 PM
To: [log in to unmask]
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 <http://www.aimsolder.com>
----- Original Message -----
From: Romm, Doug <mailto:[log in to unmask]>
To: [log in to unmask] <mailto:[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]
<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
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