TECHNET Archives

June 2006

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, James <[log in to unmask]>
Date:
Mon, 5 Jun 2006 12:39:26 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (70 lines)
 Harvey Miller (fab file online) Writes:
> The Swatch Group Is Going Back To Lead Solder - Is This the Shape of
Things to Come? 
> 
> The major Swiss, major world watchmaker, with nearly $4B sales, one
quarter of world watch production, diligently did the lead-free R&D for
2 years, went into lead-free production 13 months in advance of the RoHS
deadline, and then met disaster. Tin whiskers got them; they were
shorting circuits both in the quartz crystal resonator and fine pitch
electronic systems. Now the Swatch Group is applying for an exemption
from RoHS so they can go back to lead. 
> 
> Between you and me, I'll bet that if we could get into one of their
180 factories we'd see good old 63-37-- that is, 37% lead-being used
right now. The  "Requested Exemption"  came from the legal department,
16 pages in the English language edition, complete with tin whisker
pictures, and you know that the Technical Adaptation Committee, set up
by the European parliament> '> s Environmental Commission to shepherd
the transition to lead-free, etc., will advise granting the exemption.
The Swatch Group even tentatively offered to consider using the 90% tin
alloy which is allowed under RoHS. 
> 
> The critical dimension at which tin whisker shorting became a
production- line- stopping problem was 0.8mm, that is, 32 mils-it might
as have been a meter in electronic interconnections these days. So the
Swatch Group has given us a preview of what we will see en masse. For
those who escape tin whiskers, lead-free solder has some other treats in
store. There are Kirkendall voids-they create open circuits as copper
diffuses into tin without lead alloyed, leaving voids behind. There are
Conductive Anodic Filaments, leakage paths in the PCB, a mechanism
accelerated by the high processing temperatures of lead-free. Dongkai
Shangguan of Flextronics has put a book together describing these
lead-free solder problems and more: Lead-free Solder Interconnect
Reliability (Hardcover), Dongkai Shangguan (Editor), Publisher : ASM
International Copyright Year : 2005 Number of Pages : 350. 
> 
> The Requested Exemption from the Swatch Group has pictures of tin
whiskers. They used 99.5Sn 0.5Cu, no Ag, so not the SAC alloy, which
also contains silver. But the EU Commission dare not mandate them to use
Ag. The tin-copper alloy is generally used for wave soldering and
lead-free HASL. Besides, they know Ag is a biocide. Mine silver and you
usually get lots more lead. I think that the exemption will be granted
for the following reasons. 
> 1. It comes from the company's legal department and if the Swatch
Group is forced to stop making watches...I don't think I have to go on,
because that is almost the way they put it. 
> 
> 2. The Environmental Commission has a lot on its plate-constructive
initiatives. Why risk egg on its face? Why fight in court or in the
court of public opinion for an ecologically, environmentally damaging
ban on lead in solder? Stavros Dimas, the Environmental Commissioner,
has already acknowledged that lead-free will require greatly increased
energy. 
> 
> 3. WEEE, Waste from Electrical and Electronic Equipment already
mandates recycling populated printed circuit boards, somewhat as
lead-acid batteries are recycled now. So the ban on electronic lead was
always over-kill. 
> 

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts 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
-----------------------------------------------------

ATOM RSS1 RSS2