Re: [Flexradio] RoHS & Tin Whiskers

[Eric Ellison]

Gang

Wiskers! A lil off topic, but sometimes fun!

Yup. Doesn't matter where you are 'investigating'. I worked 27 years as a
field research biologist for several major chemical companies, getting
efficacy, rate of disappearance of parent and metabolites, etc for EPA.

Ask a few questions of the govt reviewer of a product registration about
sampling technique, and he gives an answer which indicates that he thinks
peanuts grow above ground on bushes!

How do you respond to that when he is god and you have a 200 million market
at stake? Really NOT too funny! Sampling methodology WAS worked out
diplomatically in the end!

Now I work around Arsenic Trioxide and Chromium. (go figure). Green has
shifted the 60 year old perfect track record of Chromated Copper Arsonate
out of the market to youse guys falling through your your rotted deck and
killing yourself.

Bob you gotta silence me! (smile) Or point me to a blog!

Eric2










-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Bob Tracy
Sent: Tuesday, May 02, 2006 2:00 PM
To: [EMAIL PROTECTED]; Bill Guyger; [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]; FlexRadio@flex-radio.biz
Subject: Re: [Flexradio] RoHS & Tin Whiskers

I just can't resist...

"Nothing is too good for the taxpayer and that's usually what he gets."

Bob, K5KDN

-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of [EMAIL PROTECTED]
Sent: Tuesday, May 02, 2006 12:08 PM
To: Bill Guyger; [EMAIL PROTECTED]
Cc: FlexRadio@flex-radio.biz; [EMAIL PROTECTED]
Subject: Re: [Flexradio] RoHS & Tin Whiskers


Well,.. we found out one thing: That is: all the brightest computer sutdents
at college that that now write programs for Flex radio, played hookie from
Chemistry Class!!

Most heavey metals at that end of the Periodic table are in fact VERY
posionious, with the exception of Gold. But you come in contact with them
every day in your life and handle these compounds all the time. For example
Chromium is a deadly poision, but it is 16% of the knife and "stainless
steel fork" that you ate breakfast with this morning.  But it did not seem
to hurt you. The reason is that the the metal was not in a *chemical form"
that was water soluable, therfore entry into your body was not possible.
However, if the chemical is "compounded" in the correct salt or other form,
it will most certainly  do you great harm. It's sort of a chemistry "magic
trick", but you have to be careful how far you push it.

As to regulation of chemistry by governments, well, don't get me started
there. It's 99 % politics, and 1% chemistry. Just enough chenistry thrown in
there to mank it sound to the general public like it is all "justified" and
in their best interests. One of their big games is to lower the threshhold
of "permissible levels" so low that it allows them to play any sort of
"hokus-pokus" they want with the numbers and therefore their dept budgets to
pursue "the great evils".  For example, In Souther California, there is an
agency that is sending teams of testers from their dept all over to "test"
water wells for "perchlorates". They do not even specify what perchlorate
they are after (Potassium, Sodium, etc..).. they just got the idea that
"percholorate in any form are "evil" and must be stamped out. They have the
regulatory power to shut down city water wells, and have already closed many
of them.  They  list as the threshold is 1/2 part per billion. That is the
equivilant of tossing 1/4 tsp of perchlorate into the average family
swimming pool (abt 20,000 gallons).. FYI perchlorates are naturally occuring
and very similiar to ordinary table salt. You can mix a tablespoon or two in
a glass of water and drink it down, it is harmless. Of course, if you did
that,  you  might have the runs for a day, but you would otherwise be OK.
The whole thing is a sham, but heh, it's YOUR GOVERNMENT AT WORK !!!

-Dan K6KDK




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Re: [Flexradio] RoHS & Tin Whiskers

[Bob Tracy]

I just can't resist...

"Nothing is too good for the taxpayer and that's usually what he gets."

Bob, K5KDN

-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of [EMAIL PROTECTED]
Sent: Tuesday, May 02, 2006 12:08 PM
To: Bill Guyger; [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]
Subject: Re: [Flexradio] RoHS & Tin Whiskers


Well,.. we found out one thing: That is: all the brightest computer sutdents
at college that that now write programs for Flex radio, played hookie from
Chemistry Class!!

Most heavey metals at that end of the Periodic table are in fact VERY
posionious, with the exception of Gold. But you come in contact with them
every day in your life and handle these compounds all the time. For example
Chromium is a deadly poision, but it is 16% of the knife and "stainless
steel fork" that you ate breakfast with this morning.  But it did not seem
to hurt you. The reason is that the the metal was not in a *chemical form"
that was water soluable, therfore entry into your body was not possible.
However, if the chemical is "compounded" in the correct salt or other form,
it will most certainly  do you great harm. It's sort of a chemistry "magic
trick", but you have to be careful how far you push it.

As to regulation of chemistry by governments, well, don't get me started
there. It's 99 % politics, and 1% chemistry. Just enough chenistry thrown in
there to mank it sound to the general public like it is all "justified" and
in their best interests. One of their big games is to lower the threshhold
of "permissible levels" so low that it allows them to play any sort of
"hokus-pokus" they want with the numbers and therefore their dept budgets to
pursue "the great evils".  For example, In Souther California, there is an
agency that is sending teams of testers from their dept all over to "test"
water wells for "perchlorates". They do not even specify what perchlorate
they are after (Potassium, Sodium, etc..).. they just got the idea that
"percholorate in any form are "evil" and must be stamped out. They have the
regulatory power to shut down city water wells, and have already closed many
of them.  They  list as the threshold is 1/2 part per billion. That is the
equivilant of tossing 1/4 tsp of perchlorate into the average family
swimming pool (abt 20,000 gallons).. FYI perchlorates are naturally occuring
and very similiar to ordinary table salt. You can mix a tablespoon or two in
a glass of water and drink it down, it is harmless. Of course, if you did
that,  you  might have the runs for a day, but you would otherwise be OK.
The whole thing is a sham, but heh, it's YOUR GOVERNMENT AT WORK !!!

-Dan K6KDK




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Re: [Flexradio] RoHS & Tin Whiskers

[k6kdk]

Well,.. we found out one thing: That is: all the brightest computer sutdents
at college that that now write programs for Flex radio, played hookie from
Chemistry Class!!

Most heavey metals at that end of the Periodic table are in fact VERY
posionious, with the exception of Gold. But you come in contact with them
every day in your life and handle these compounds all the time. For example
Chromium is a deadly poision, but it is 16% of the knife and "stainless
steel fork" that you ate breakfast with this morning.  But it did not seem
to hurt you. The reason is that the the metal was not in a *chemical form"
that was water soluable, therfore entry into your body was not possible.
However, if the chemical is "compounded" in the correct salt or other form,
it will most certainly  do you great harm. It's sort of a chemistry "magic
trick", but you have to be careful how far you push it.

As to regulation of chemistry by governments, well, don't get me started
there. It's 99 % politics, and 1% chemistry. Just enough chenistry thrown in
there to mank it sound to the general public like it is all "justified" and
in their best interests. One of their big games is to lower the threshhold
of "permissible levels" so low that it allows them to play any sort of
"hokus-pokus" they want with the numbers and therefore their dept budgets to
pursue "the great evils".  For example, In Souther California, there is an
agency that is sending teams of testers from their dept all over to "test"
water wells for "perchlorates". They do not even specify what perchlorate
they are after (Potassium, Sodium, etc..).. they just got the idea that
"percholorate in any form are "evil" and must be stamped out. They have the
regulatory power to shut down city water wells, and have already closed many
of them.  They  list as the threshold is 1/2 part per billion. That is the
equivilant of tossing 1/4 tsp of perchlorate into the average family
swimming pool (abt 20,000 gallons).. FYI perchlorates are naturally occuring
and very similiar to ordinary table salt. You can mix a tablespoon or two in
a glass of water and drink it down, it is harmless. Of course, if you did
that,  you  might have the runs for a day, but you would otherwise be OK.
The whole thing is a sham, but heh, it's YOUR GOVERNMENT AT WORK !!!

-Dan K6KDK




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[EMAIL PROTECTED]
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Re: [Flexradio] RoHS & Tin Whiskers

[Bill Guyger]

e high reliability user.
> > "
> >
> > There is a wealth of information on the tin whiskers problem at 
> the NASA URL
> > I listed. I won't repeat it here, but I would suggest that those, 
> (I suggest
> > anyone who buys consumer electronics should be), who are 
> interested read the
> > information at the URL and resources suggested.
> >
> > To simply say it has existed, does not resolve the believed increase of tin
> > whiskers due to the use tin plated only components and the use of no-lead
> > solder.
> >
> > Another posting by Ahti Aintila to the reflected has suggested an
> > alternative, but if the components are tin plated only, then the formation
> > of tin whiskers will occur. The NASA WEB site does not propose a sure fire
> > solution and in fact, exceptions are made for mission critical systems to
> > meet RoHS by the EU.
> >
> > Obviously, the removal of lead is a good thing, but the introduction of a
> > new problem without a known solution is short sighted.
> >
> > I discussed RoHS with a US distributor representative expressing 
> my concerns
> > of product reliability. His response was products are obsolete in a few
> > years anyhow. My response is I really wouldn't like to replace a 
> $3000 piece
> > of consumer electronics equipment in 2 years or less.
> >
> > I have discussed this with manufacturers also. They are concerned with the
> > shelve life of products, as tin whiskers are a result of time, not
> > environment. In fact, one has mentioned changing his warrantee to reflect
> > time from factory shipment.
> >
> > Although goods sold in the US do not currently require no-lead components,
> > the EU RoHS requirements are rippling into the distribution chains.
> >
> > Regardless, tin whiskers appear to be a real problem that is being sweep
> > under the rug in the rush to no-lead solutions.
> >
> > 73,
> > Bill Bordy
> > NJ1H
> >
> >
> >
> > -Original Message-
> > From: Jim Lux [mailto:[EMAIL PROTECTED] 
> > Sent: Monday, May 01, 2006 1:40 PM
> > To: William Bordy; 'Lyle Johnson'
> > Cc: 'FlexRadio'
> > Subject: RE: [Flexradio] RoHS & Tin Whiskers was Re: July 1
> >
> > At 09:28 AM 5/1/2006, William Bordy wrote:
> > >I have been following the RoHS requirements and one issue I see rarely
> > >discussed is the "Tin Whiskers" issue. For those that are not 
> familiar with
> > >it please see the following WEB site:
> > >
> > >http://nepp.nasa.gov/WHISKER/background/index.htm 
> > >
> > >It appears that with the switch to no-lead that the reliability of the
> > >equipment will be substantially reduced.
> >
> > Problems with tin whiskers have been around a lot longer than RoHS (perhaps
> > as far back as WW II?). It presents a problem with reliability of equipment
> > designed for low cost production, with no budget for re-engineering, sure.
> > But for the rest, it's not so clear.
> >
> >
> >
> > >This appears to be what happens
> > >when politics drive science.
> >
> > No science involved here. Lead has been known as a toxin for centuries.
> > It's just that society, as a whole, has decided that it's worth reducing
> > the amount being discarded, much as they've decided that the societal costs
> > of air pollution or persistent pesticides were greater than the cost of
> > reducing it.  In general, reducing waste in any form has a long term
> > benefit because it provides more efficient resource utilization: in the
> > sense that more of the value goes into the eventual product use, as opposed
> > to being discarded during manufacturing or at product EOL.
> >
> > Not so much politics, but the race to the bottom for low cost production,
> > driven by the capital market's expectations of short term returns on
> > investment.
> >
> > In the long run, we DO benefit, even if we suffer from short term
> > fixes.  Consider, for instance, emissions controls on cars.  The "quick
> > fixes" of the 70s were pretty lame.  Today, however, cars are more
> > efficient, less expensive (in constant dollars), and last a lot longer, and
> > run a lot better (because of electronic engine controls). Back in the 60s &
> > 70s, a car that lasted more than 100k miles was unusual, and a car that
> > went 200k miles was something special (remember a print ad campaign about a
> > VW or Toyota that had 250+k miles... the distance to the moon).  Today,
> >

Re: [Flexradio] RoHS & Tin Whiskers

[Ahti Aintila]

ng sweep
under the rug in the rush to no-lead solutions.

73,
Bill Bordy
NJ1H



-Original Message-
From: Jim Lux [mailto:[EMAIL PROTECTED]
Sent: Monday, May 01, 2006 1:40 PM
To: William Bordy; 'Lyle Johnson'
Cc: 'FlexRadio'
Subject: RE: [Flexradio] RoHS & Tin Whiskers was Re: July 1

At 09:28 AM 5/1/2006, William Bordy wrote:
>I have been following the RoHS requirements and one issue I see rarely
>discussed is the "Tin Whiskers" issue. For those that are not familiar with
>it please see the following WEB site:
>
>http://nepp.nasa.gov/WHISKER/background/index.htm
>
>It appears that with the switch to no-lead that the reliability of the
>equipment will be substantially reduced.

Problems with tin whiskers have been around a lot longer than RoHS (perhaps
as far back as WW II?). It presents a problem with reliability of equipment
designed for low cost production, with no budget for re-engineering, sure.
But for the rest, it's not so clear.



>This appears to be what happens
>when politics drive science.

No science involved here. Lead has been known as a toxin for centuries.
It's just that society, as a whole, has decided that it's worth reducing
the amount being discarded, much as they've decided that the societal costs
of air pollution or persistent pesticides were greater than the cost of
reducing it.  In general, reducing waste in any form has a long term
benefit because it provides more efficient resource utilization: in the
sense that more of the value goes into the eventual product use, as opposed
to being discarded during manufacturing or at product EOL.

Not so much politics, but the race to the bottom for low cost production,
driven by the capital market's expectations of short term returns on
investment.

In the long run, we DO benefit, even if we suffer from short term
fixes.  Consider, for instance, emissions controls on cars.  The "quick
fixes" of the 70s were pretty lame.  Today, however, cars are more
efficient, less expensive (in constant dollars), and last a lot longer, and
run a lot better (because of electronic engine controls). Back in the 60s &
70s, a car that lasted more than 100k miles was unusual, and a car that
went 200k miles was something special (remember a print ad campaign about a
VW or Toyota that had 250+k miles... the distance to the moon).  Today,
there's lots and lots of cars with more than 100,000 miles running just
fine.  And, what about muffler replacement (unleaded gas required reducing
the sulfur in gasoline, which in turn reduced the amount of sulfuric acid
that accumulated in the muffler.. further, the requirement that exhaust
systems not leak for 50,000 miles prompted improvements in design to make
them last longer)


>73,
>Bill Bordy
>NJ1H

James Lux, P.E.
Spacecraft Radio Frequency Subsystems Group
Flight Communications Systems Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875

Re: [Flexradio] RoHS & Tin Whiskers

[Jim Lux]

At 02:59 PM 5/1/2006, William Bordy wrote:

>>Problems with tin whiskers have been around a lot longer than RoHS
>>(perhaps
>>as far back as WW II?). It presents a problem with reliability of
>>equipment
>>designed for low cost production, with no budget for re-engineering, sure.

>>But for the rest, it's not so clear.

Yes, as the listed WEB explains, tin whiskers have been around a lot longer
than RoHS. But, as the below excerpt from the WEB site,
http://nepp.nasa.gov/WHISKER/background/index.htm ,  explains, it is
believed that no-lead solders will increase the risk of tin whiskers.

"
There is a wealth of information on the tin whiskers problem at the NASA URL
I listed. I won't repeat it here, but I would suggest that those, (I suggest
anyone who buys consumer electronics should be), who are interested read the
information at the URL and resources suggested.

To simply say it has existed, does not resolve the believed increase of tin
whiskers due to the use tin plated only components and the use of no-lead
solder.


Indeed. It IS a problem, but only for pure tin (and pure zinc).  The pure 
tin thing was a "quick fix", that, as you note, has been thoroughly 
discredited as a solution.




Obviously, the removal of lead is a good thing, but the introduction of a
new problem without a known solution is short sighted.


There are known solutions, they're just not as cheap as tin/lead, nor is 
there decades of experience with them.  Most manufacturers, being fairly 
short term bottom line oriented would prefer to keep things the way they 
are, rather than spend NRE money on redoing the process engineering and RE 
money on more expensive substrates and/or solder.


There IS an exemption for the tiny amount of lead used inside the 
semiconductor package.


The exemption for "mission critical" isn't forever, either. I believe it 
expires in 2010.  Besides, the space industry is so tiny, compared to the 
commercial industry, that we in the space biz have to figure out how to use 
what's commercially available, since they're not going to run two different 
production lines.  The same is true, in the longer run, with military 
stuff.  Their volumes are higher, so they have a bit more clout.




I discussed RoHS with a US distributor representative expressing my concerns
of product reliability. His response was products are obsolete in a few
years anyhow. My response is I really wouldn't like to replace a $3000 piece
of consumer electronics equipment in 2 years or less.
Your distributor was right, though.  The vast volume of consumer 
electronics (in a dollars, and pieces basis) is disposable/consumable 
stuff: cellphones, MP3 players, computers, etc.  There's actually 
relatively little volume in the $3K and up range with expected life >3 
years.  For equipment in that range, one can expect that the cost of RoHS 
is a much smaller fraction of the total unit cost, and so, a mfr can afford 
to invest in the needed reengineering to make it work, or, to cover 
warranty returns.  There's also a huge difference between the "design use 
life" for piece of consumer electronics (typically 1-2 yrs) and the actual 
life (which could be much longer).  This is why, for instance, consumer 
computers are much cheaper than "real" server computers (at least, when the 
mfr is taking the risk of failure).  In the consumer market, sell price is 
everything, because most consumers don't factor in the largely speculative 
future costs. In the commercial/industrial/professional market, life cycle 
cost (TCO) is what they buyer looks at, and gear is designed and priced 
accordingly.


This comes up a lot for people building things like server farms or cluster 
computers, where the cost of a failure is known, and includes things like 
the time for the administrator to figure out it's broken, pull it out of 
the rack, the time to rerun the job from a checkpoint, etc. The "all-in" 
cost of a single failed cluster node could be several thousand dollars. 
It's not too hard to figure out how much more you can afford to pay for 
changing the failure rate from 5% in the first year to less than 1%.



I have discussed this with manufacturers also. They are concerned with the
shelve life of products, as tin whiskers are a result of time, not
environment. In fact, one has mentioned changing his warrantee to reflect
time from factory shipment.


This sort of thing is why I think that what you'll see is more of a 
stratification between "throwaway consumer electronics" and 
"commercial/professional electronics".  Where it will get ugly is in that 
"pro-sumer" sort of regime, where people are expecting consumer type 
pricing, but also expect long-lived, durable designs.


Kind of like the difference between an inexpensive imported machine tool at 
Harbor Freight and a watchmaker's lathe from Germany.




Although goods sold in the US do not currently require no-lead components,
the EU RoHS requirements are rippling into the distribution chains.

Reg

Re: [Flexradio] RoHS & Tin Whiskers

[William Bordy]

>>Problems with tin whiskers have been around a lot longer than RoHS
>>(perhaps 
>>as far back as WW II?). It presents a problem with reliability of
>>equipment 
>>designed for low cost production, with no budget for re-engineering, sure.

>>But for the rest, it's not so clear.

Yes, as the listed WEB explains, tin whiskers have been around a lot longer
than RoHS. But, as the below excerpt from the WEB site,
http://nepp.nasa.gov/WHISKER/background/index.htm ,  explains, it is
believed that no-lead solders will increase the risk of tin whiskers. 

"
Why the Recent Attention to Tin Whiskers?
The current worldwide initiative to reduce the use of potentially hazardous
materials such as lead (Pb) is driving the electronics industry to consider
alternatives to the widely used tin-lead alloys used for plating. For
example, the European Union has enacted legislation known as the Restriction
of certain Hazardous Substances (RoHS) and Waste Electrical and Electronic
Equipment (WEEE) Directives which have set June 2006 as deadlines for
electronic equipment suppliers to eliminate most uses of Pb from their
products.  It is widely believed (though reasons remain somewhat of a
mystery) that Pb when alloyed with tin imparts whisker-inhibiting attributes
to the final finish. 

With respect to factors such as solderability, ease of manufacture and
compatibility with existing assembly methods, pure tin plating is seen by
the industry as a potentially simple and cost effective alternative. In
fact, many manufacturers have been offering pure tin plated components as a
standard commercial (and in some cases high reliability) product for years
while others are exploring pure tin alternatives for the very first time.
Many electronics manufacturers have never heard of the phenomenon of tin
whiskers and therefore, may not consider the risks of tin whisker growth
during the validation of new plating systems. 

Continuing reports of tin whisker-induced failures coupled with the lack of
an industry accepted understanding of tin whisker growth factors and/or test
methods to identify whisker-prone products has made a blanket acceptance of
pure tin plating a risky proposition for high reliability systems.  Still,
organizations such as NASA and the DoD may soon be faced with few options
other than pure tin plating since the desires of the commercial market for
environmentally friendly components carry far more weight than the
infinitesimally small market share of the high reliability user.
"

There is a wealth of information on the tin whiskers problem at the NASA URL
I listed. I won't repeat it here, but I would suggest that those, (I suggest
anyone who buys consumer electronics should be), who are interested read the
information at the URL and resources suggested.

To simply say it has existed, does not resolve the believed increase of tin
whiskers due to the use tin plated only components and the use of no-lead
solder.

Another posting by Ahti Aintila to the reflected has suggested an
alternative, but if the components are tin plated only, then the formation
of tin whiskers will occur. The NASA WEB site does not propose a sure fire
solution and in fact, exceptions are made for mission critical systems to
meet RoHS by the EU. 

Obviously, the removal of lead is a good thing, but the introduction of a
new problem without a known solution is short sighted. 

I discussed RoHS with a US distributor representative expressing my concerns
of product reliability. His response was products are obsolete in a few
years anyhow. My response is I really wouldn't like to replace a $3000 piece
of consumer electronics equipment in 2 years or less.

I have discussed this with manufacturers also. They are concerned with the
shelve life of products, as tin whiskers are a result of time, not
environment. In fact, one has mentioned changing his warrantee to reflect
time from factory shipment.

Although goods sold in the US do not currently require no-lead components,
the EU RoHS requirements are rippling into the distribution chains.

Regardless, tin whiskers appear to be a real problem that is being sweep
under the rug in the rush to no-lead solutions.

73,
Bill Bordy
NJ1H



-Original Message-
From: Jim Lux [mailto:[EMAIL PROTECTED] 
Sent: Monday, May 01, 2006 1:40 PM
To: William Bordy; 'Lyle Johnson'
Cc: 'FlexRadio'
Subject: RE: [Flexradio] RoHS & Tin Whiskers was Re: July 1

At 09:28 AM 5/1/2006, William Bordy wrote:
>I have been following the RoHS requirements and one issue I see rarely
>discussed is the "Tin Whiskers" issue. For those that are not familiar with
>it please see the following WEB site:
>
>http://nepp.nasa.gov/WHISKER/background/index.htm
>
>It appears that with the switch to no-lead that the reliability of the
>equipment will be substantially reduced.

Problems with tin whiskers have been around a lot longer

Re: [Flexradio] RoHS & Tin Whiskers was Re: July 1

[Ahti Aintila]

Bill,

You are right, at least partially. There is a big risk of tin whiskers
shorting the narrow gaps between the fine pitch lead-free solder
joints, unless the manufacturers know exactly their materials and can
strictly control the process.

There are positive examples since several years when some leading
Japanese manufacturers voluntarily changed over to lead-free assembly
in their consumer electronics. So far no alarming reports.

It is true, higher temperatures put a lot more stress to the material
and components, but that is not the fault of politicians. The industry
itself made wrong decisions when selecting the alloying materials for
the lead-free solders used now generally in the RoHS process. There is
a material and soldering process that would work riskless and even at
much lower temperatures. It is called "Transfusion Bonding" that is
using bismuth instead of lead for alloying the solder joint.

In this process you tinplate the solderpads and componets and then add
a thin layer of bismuth over tin. Reflow at +180 deg C, bismuth starts
to melt already at 139 deg C, it diffuses quickly into the tin forming
a thin alloy layer. All the time bismuth continues its diffusion into
the tin matrix, thus the molten mix becomes very lean Bi-Sn alloy that
forms reliable bonds. Also, as the ally becomes leaner, its melting
temperature increases. Actually, even after the temperature is lowered
the bismuth diffusion continues until the alloying is uniform across
the whole solder joint.

The remelting temperature of resulting bond is very close to the
melting temperature of pure tin, +132 deg C! This about 1% content of
bismuth in the alloy can relax the internal energy of the crystal
structure and prevent tin whisker formation.

Why this process is not used generally in the industry? The answer is,
it was invented 10 years ago in the wrong place and hurted interests
of big international companies that already invested huge amounts of
dollars, yens, pounds, etc in tin-silver-zinc alloys. Seldom the best
technolgy wins, only big money talks.

Those who are interested, may read more in the publications of the
IEEE. Look for Professor Jorma Kivilahti, Helsinki University of
Technology. Unfortunately those articles are not freely available,
unless you are a subscriber of the IEEE publications. I found only one
free article that shortly mentions this method:


73, Ahti OH2RZ


On 01/05/06, William Bordy <[EMAIL PROTECTED]> wrote:

I have been following the RoHS requirements and one issue I see rarely
discussed is the "Tin Whiskers" issue. For those that are not familiar with
it please see the following WEB site:

http://nepp.nasa.gov/WHISKER/background/index.htm

It appears that with the switch to no-lead that the reliability of the
equipment will be substantially reduced. This appears to be what happens
when politics drive science.

73,
Bill Bordy
NJ1H

-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Lyle Johnson
Sent: Monday, May 01, 2006 10:28 AM
To: Jim Lux
Cc: FlexRadio
Subject: Re: [Flexradio] RoHS was Re: July 1

> Bob, I assume you're talking about RoHS, which bans lead (except in
certain
> very narrow situations, not applicable here)  in electronics.
>
> I don't know much about how Gerald makes the boards for the SDR1000, but I

> wouldn't think that changing to no-lead solder is a big issue...

Actually, it is a big issue.

Turns out that no-lead solder manufacturing processes require more heat,
and normal FR-4 PCBs tend to delaminate, so you must use
high-temperature fiberglass.  This is available, just more expensive --
20% to 50% higher cost per board.

Fewer facilities are available to manufacture assemblies in a RoHS
compliant way, and willing to certify same, so those costs go up.  In
the case of my DSPx, the quotes I have for the raw PCB cost are double
and the assembly costs will more than double what I am currently paying.

The components used in the product must all be RoHS compliant.

And it isn't just about lead.  There are six commonly used substances
that are banned or severely proscribed.  Normal passivation processes
used for aluminum, for example, contain banned substances, so even the
case may be affected.

73,

Lyle KK7P




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Re: [Flexradio] RoHS & Tin Whiskers was Re: July 1

[Jim Lux]

At 09:28 AM 5/1/2006, William Bordy wrote:

I have been following the RoHS requirements and one issue I see rarely
discussed is the "Tin Whiskers" issue. For those that are not familiar with
it please see the following WEB site:

http://nepp.nasa.gov/WHISKER/background/index.htm

It appears that with the switch to no-lead that the reliability of the
equipment will be substantially reduced.


Problems with tin whiskers have been around a lot longer than RoHS (perhaps 
as far back as WW II?). It presents a problem with reliability of equipment 
designed for low cost production, with no budget for re-engineering, sure. 
But for the rest, it's not so clear.





This appears to be what happens
when politics drive science.


No science involved here. Lead has been known as a toxin for centuries. 
It's just that society, as a whole, has decided that it's worth reducing 
the amount being discarded, much as they've decided that the societal costs 
of air pollution or persistent pesticides were greater than the cost of 
reducing it.  In general, reducing waste in any form has a long term 
benefit because it provides more efficient resource utilization: in the 
sense that more of the value goes into the eventual product use, as opposed 
to being discarded during manufacturing or at product EOL.


Not so much politics, but the race to the bottom for low cost production, 
driven by the capital market's expectations of short term returns on 
investment.


In the long run, we DO benefit, even if we suffer from short term 
fixes.  Consider, for instance, emissions controls on cars.  The "quick 
fixes" of the 70s were pretty lame.  Today, however, cars are more 
efficient, less expensive (in constant dollars), and last a lot longer, and 
run a lot better (because of electronic engine controls). Back in the 60s & 
70s, a car that lasted more than 100k miles was unusual, and a car that 
went 200k miles was something special (remember a print ad campaign about a 
VW or Toyota that had 250+k miles... the distance to the moon).  Today, 
there's lots and lots of cars with more than 100,000 miles running just 
fine.  And, what about muffler replacement (unleaded gas required reducing 
the sulfur in gasoline, which in turn reduced the amount of sulfuric acid 
that accumulated in the muffler.. further, the requirement that exhaust 
systems not leak for 50,000 miles prompted improvements in design to make 
them last longer)




73,
Bill Bordy
NJ1H


James Lux, P.E.
Spacecraft Radio Frequency Subsystems Group
Flight Communications Systems Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875

Re: [Flexradio] RoHS & Tin Whiskers was Re: July 1

[William Bordy]

I have been following the RoHS requirements and one issue I see rarely
discussed is the "Tin Whiskers" issue. For those that are not familiar with
it please see the following WEB site:

http://nepp.nasa.gov/WHISKER/background/index.htm

It appears that with the switch to no-lead that the reliability of the
equipment will be substantially reduced. This appears to be what happens
when politics drive science.

73,
Bill Bordy
NJ1H