[tinwhiskers] Re: ACE Develops Lead Tinning Syste m

  • From: "Mark Vaughan" <mark@xxxxxxxxxx>
  • To: <tinwhiskers@xxxxxxxxxxxxx>
  • Date: Mon, 9 Jun 2008 08:21:56 +0100

Werner

I'm curious about your statement item 1

'(1) Ag, the main substitute for Pb, readily leaches in base landfills, and
produces toxic bactericides'

Silver certainly works as a good bactericide, though I wasn't aware it being
associated with the term toxic.

It's commonly used in cooling towers and swimming pools as a bactericide
where a few ppm's will kill virtually all present bacteria and chlorine or
Bromine levels which are the main bactericide can be dropped to the legal
minimum of 0.5ppm.

In small quantities in the blood it is also beneficial to aid the immune
system. 

The world health foundation do have a maximum ppm level for silver in
drinking water, but I'm not aware of any issues where it has been considered
toxic, other than perhaps around silver processing plants.

As far as I'm aware silver as a bactericide also only kills single cell
organisms like bacteria and has no effect on large cellular structures, thus
it's good for bacteria but doesn't harm people. I suppose in some areas
there must be good single celled organisms as well as bad ones, but no
bactericide is discriminatory and are used in much higher strengths through
conventional drainage systems and by the volumes they are used potentially
much more damaging than silver.

 

I'm on your side regarding the lead ban, just not sure of the integrity of
your statement regarding silver. I'm not an expert regarding the use of
silver as a bactericide but I have been involved with several companies that
use it for such, and have designed electronics for them. Several of these
companies had quite eminent bio chemists behind them, who I believe would
also be surprised at your comment.

Brining this into some possible reality, I'm also surprised enough lead
leaches from a general mixed household waste landfill site to form any
concentration where it could be considered dangerous. We used it for water
pipes for enough years without seeing many problems.

 

Regs Mark

 

Dr. Mark Vaughan Ph'D., B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd., reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH UK.

Phone/Fax 44 (0) 1872 561288

RSGB DRM111 (Cornwall)

  _____  

From: tinwhiskers-bounce@xxxxxxxxxxxxx
[mailto:tinwhiskers-bounce@xxxxxxxxxxxxx] On Behalf Of Engelmaier@xxxxxxx
Sent: 08 June 2008 20:39
To: tinwhiskers@xxxxxxxxxxxxx; salag@xxxxxxxxxxx
Subject: [tinwhiskers] Re: ACE Develops Lead Tinning Syste m

 

Hi Bob,
Well, we are on the same side on the Pb-ban of RoHS. Just so you get any
idea, the second slide of my workshop 'Pb-Free Soldering Processes-Survival,
Quality, Reliability' reads as follows:
POSITION STATEMENT
The Pb-ban under RoHS is damaging to the environment, because:
(1) Ag, the main substitute for Pb, readily leaches in base landfills, and
produces toxic bactericides;
(2) Pb in solder is not an environmental hazard, because it requires an
acidic environment to leach in a landfill when landfills are base;
(3) Because of the much higher Liquidus temperatures for the substitute SAC
solders, significantly more energy is required in production, assembly and
moisture bake-out;
(4) Because of the reduced yields due to SJ brittle failure, PCB and
component damage, more electronic product needs to be scrapped;
(5) No solution as yet has been found for the tin whisker problem under the
RoHS Pb-ban;
(6) The unnecessary costs so far have been estimated at $38,000,000,000 to
date and $3,700,000,000 annually.

Even IPC-D-279 was written way before RoHS [July 1996]. I had no vote on
RoHS either, and I strongly criticized the IPC when they jumped on the
bandwagon when they thought it was environmentally responsible, and some of
us knew better.

Well Sony does not have a well-established reliability history; the
exploding batteries nade the headlines because of the fires, however, many
more of their laptops are failing because of fractured solder joints. There
is a whole cottage industry out there repairing Sony laptops as well as
others.

If you have pre-RoHS electronics, be very reluctant to replace it with "RoHS
compliant"-no guarantees there.

The problem with electronics is that it has gotten much more functional,
much smaller, much more densely packed-all of which gave the industry a
headache even without RoHS. That RoHS-monkeywrench just makes things much
worse [just think of the much higher processing temperatures]. 

Since 1973, the electronics content of cars has gone from zero to about 30%
[in value], and in terms of reliability issues from zero to about 80%.

I always use the "Emperor's New Clothes" fable as an analog to the RoHS
Pb-ban. 

It was not just the Hubble, but also the Magellan and the Galileo that
were/are affected by fractured solder joints. I was consulting with JPL on
these issues-what actually happened was that the NASA test requirements [on
the actual flight hardware, mind you] was the equivalent of driving a car
into a stone wall prior to selling it-they consummed 60% of the solder joint
life, on average. The basic design was perfect, but the test requirements
were mindless stemming from a total lack of understanding of solder
creep-fatigue behavior. You need also keep in mind, solder joints do not
give dead opens when they fracture but intermittents during transient
loading conditions [change in temperature, reorienting of antennas, etc.].
A little history:
January 28, 1986-Challenger shuttle disaster delays launch of Magellan and
Galileo spacecraft .
Prior to launch from Space Shuttle Atlantis on May 4 and October 16, 1989,
for the Magellan and Galileo spacecraft respectively, SJ fractures found in
electronics of both, and manually (!) resoldered.
April 24, 1990 launch of Hubble Telescope from Discovery. Besides the much
vaunted optics problem, the Hubble Telescope , also had electronic failures.
December 1993-1st Servicing Mission to Hubble Telescope by Space Shuttle
Endeavour. SJ fractures found in electronics returned.

Reliability issues can only be tackeled one at a the time-it is the
metallurgists [I am a ME] that need to tackle the tin whisker problem, but
do not hold your breath. As you pointed out, we had tin whisker problems
prior to RoHS, just not as many and as prominent. The industry need to
address this issue from the component side, read: JEDEC. However, the
component manufacturers have a long history of having a 'throw it over the
wall' attitude.

Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Cell: 386-316-5904
E-mail: Engelmaier@xxxxxxx, Website: www.engelmaier.com



**************
Get trade secrets for amazing burgers. Watch "Cooking with Tyler Florence"
on AOL Food.
(http://food.aol.com/tyler-florence?video=4?&NCID=aolfod00030000000002)

Other related posts: