We've done extensive studies on our lead free modules, including
extended thermal cycling in high humidity environments. To my knowledge
there have been no incidences of tin whiskers.
Andy K.
Sychip Inc
Office (972) 202 8852
-----Original Message-----
From: Barbara Burcham [mailto:[log in to unmask]]
Sent: Wednesday, June 16, 2004 2:50 PM
To: (Designers Council Forum); Kowalewski, Andy
Subject: RE: [DC] Lead free processes and the impact to your PCB
manufactu ring and assembly
Are you seeing any signs of 'tin whiskers' or on assemblies in the
field?
Barbara J. Burcham, C.I.D.
Fairfield Industries, Inc
281-275-7687
[log in to unmask]
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Kowalewski, Andy
Sent: Wednesday, June 16, 2004 1:27 PM
To: [log in to unmask]
Subject: Re: [DC] Lead free processes and the impact to your PCB
manufactu ring and assembly
Every design we do now is lead free because of international markets,
and let me share some of my observations:
We haven't changed pad sizes, initially because our designs are so small
we couldn't. After a lot of environmental testing, pad sizes the way
they are for PbSn is good for lead free also, at least for our boards.
Haven't found any differences in lead free RF characteristics. Again our
very small designs are swamped by other issues and the very short RF
traces are not affected by the small changes caused by lead free
solders, if any.
One of the biggest factors is that lead free solder doesn't flow
anything like leaded solder when reflowed. It stays where its put, and
just melts. As a result, we have managed to do away with solder mask
altogether under our flip chips for better underfill flow, and we get no
short circuits even with 50um (2 mil) traces and spaces pad-to-trace.
Solder mask registration was a showstopper for our tight designs with
leaded solder, because the solder mask registration tolerance meant we
had to keep traces at least 100u (4 mil) away from pad edges, with a 50u
(2 mil) pad-to-mask opening. Now we have a lot more room to manouver. As
well, the solder doesn't wick down the entry traces at all.
Another big issue is the Tg of the laminate because of the higher reflow
temperature, usually 260 degrees C. We use BT cores and high Tg RCC
foils - that gives us some latitude as our modules get two reflow passes
in assembly and another one when mounted on a cutomer's motherboard. So
far it's working well.
Initially component supply was a problem but that's almost gone away for
what we do. In fact some components aren't available in anything but
lead free metalization. We did have some problems a while ago with
reflow soldering some components with tin/lead solder - component
fabricators had changed the metalization to lead free without notice and
reflow profiles needed tweaking.
Andy K.
Sychip Inc
Office (972) 202 8852
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
George Patrick
Sent: Wednesday, June 16, 2004 1:05 PM
To: [log in to unmask]
Subject: Re: [DC] Lead free processes and the impact to your PCB
manufactu ring and assembly
We are finding real problems with parts procurement, and have found that
roadmaps of some of our parts suppliers is to phase out lead terminated
parts fairly rapidly. We also don't know the impact yet, but are
watching
the situation since some of the termination chemistries are not very
compatible with the normal PbSn chemistries.
The main issue we have found is the higher soldering temperature. We
don't
have enough data yet to verify reliability problems due to the changes
in
solder fillets, but it is a possibility pad sizes will have to increase
because of it, and because of the centering and tombstoning that is more
prevalent. We have also found some differences in electrical
characteristics of High-frequency RF boards that have necessitated
changes
in circuit values and re-layout of critical circuits, mainly in areas
free
of soldermask.
My information is second hand, I am not on the core team so I don't have
details.
A LOT of designers have their collective heads in the sand about this.
When
the PNW chapter polled for what members and associates wanted to hear
about
this year, lead-free was last or second-from-last thing on the list.
--
George Patrick
Tektronix, Inc.
Central Engineering, PCB Design Group
P.O. Box 500, M/S 39-512
Beaverton, OR 97077-0001
Phone: 503-627-5272 Fax: 503-627-5587
http://www.tektronix.com http://www.pcb-designer.com
It's my opinion, not Tektronix'
-----Original Message-----
From: Brooks,Bill [mailto:[log in to unmask]]
Sent: Wednesday, June 16, 2004 10:11
To: [log in to unmask]
Subject: [DC] Lead free processes and the impact to your PCB
manufacturing
and assembly
Yesterday I was reading the cover article in Electronic Design on
"Managing Product Obsolescence" page 47 by Ron Schneiderman and it
alarmed
me so that I fired off an e-mail to my boss in engineering and the heads
of
the company manufacturing group. It seems we can't ignore the changes in
the
industry or procrastinate and keep using tin/lead solder if the
component
manufacturers are going all lead free... (unless the components they
make
are compatible with both processes.) That I have not looked into as yet,
but
I can assure you, I will be learning more about the lead free process
and
what the potential impacts will be on our ability to produce our
products.
Until now, I have been sitting on the sidelines listening in
occasionally to
issues on the lead free debate... I didn't think it would affect us
directly, but now it looks like I am forced to really pay attention to
it
because it will most likely affect us all.
I would be grateful if you have had experience with the lead free
manufacturing process and its impacts at your company and would like to
know
how you dealt with it... I want to capture a list of potential needed
adjustments to our processes and designs that we should be looking into
changing and help to get us on that path so we can prevent any potential
manufacturing/rework issues in advance.
Here's what I wrote:
-------------------------------
Greetings -
There has been much discussion in the IPC and in the electronics
manufacturing news circuit on the 'lead free' mandate that the E.U.
authored
years back... We will be seeing the effects of it coming to a head in
the
very near future, if it has not already begun to affect us by now.
If electronics parts manufacturers are moving to lead free compatible
components at the rates suggested in the news we are in for more parts
obsolescence issues and in larger quantities than we have seen before.
Ref
Electronic Design magazine cover article "Managing Product Obsolescence"
June 7,th 2004.
We would be prudent to study the impact of lead free technology on our
compliment of components and make sure we head off this potential design
and
manufacturing procurement bottleneck before it rears its ugly head in
the
middle of production of a large order. (I would suspect that there has
already discussion about this at higher levels... )
Even if we say that we might be exempt from using lead free processes in
our
products as I have heard some military suppliers say, we may find that
we
cannot get the parts that would work with a tin/lead soldering process
after
a few years... They are going to decline out of demand and that will
drive
them into obsolescence. The only people with lead process parts in stock
will be the scalpers and higher priced component brokers. I would expect
there to be exceptions to the rule but we need to identify the potential
problems before they get to be problems.
PCNalert, a company that monitors and reports on parts obsolescence
issues,
is receiving 50 parts obsolescence notices a day now. That trend will
most
likely get worse before it gets better.
If we do decide to go lead free in our processes we will need equipment
that
can support the soldering temp profiles and higher temp materials will
be
required for boards. This may also affect the footprint patterns for
many
parts as well. I'm sure there will be other impacts, supplies of lead
free
solder for rework, higher temp soldering irons, fluxes with different
chemistries, potential safety issues, training to deal with newer
technologies... the list may be long...
The deadline for compliance with the E.U. hazardous substance mandate is
2006. We will probably see common lead containing components drop off
in
availability before then as the lead free counterparts are becoming more
and
more available.
I just wanted to bring it to your attention if you had not thought of
the
potential impacts on your department or specific activities here at
Datron.
Best regards,
Bill Brooks
PCB Design Engineer , C.I.D., C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
http://pcbwizards.com
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