Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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  #1   Report Post  
Jeffrey Lindemuth
 
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Default How do tell a liquid from a solid?

First just to make sure we are talking the same language, the
following is copied directly for Indium Corp of America's
(www.indium.com) application note Soldering 101


Basic Solder Metallurgy

As heat is gradually applied to solder, the temperature rises until
the alloy's solidus is reached. The solidus is the highest temperature
at which an alloy is completely solid. At temperatures just above the
solidus the solder is a mixture of liquid and solid component
(analogous to snow mixed with water). As the temperature is further
increased, the liquidus is reached. The liquidus is the lowest
temperature at which the alloy is completely molten. The solder
remains in the fully liquid or molten state at temperatures above the
liquidus. Upon removal of the heat source, the cycle is reversed, i.e.
the solder physical form changes from completely liquid to
liquid+solid to completely solid. Graphs that plot temperature vs.
composition are known as phase diagrams and are widely used to
determine the phases and intermetallic compositions of solder at a
given temperature. The range between the solidus and liquidus is known
as the plastic region or zone of the solder. If the solder joint is
mechanically disturbed while the assembly is cooling through the
plastic region, the solder crystal structure can be disrupted,
resulting in a high electrical resistance. Such solder joints with
high electrical resistance are referred to "cold solder joints" and
are undesirable. To avoid this problem, it is best to elect a solder
that has a narrow plastic range, one with less than ten degrees C.
There are some solder alloys that have no plastic region (liquidus =
solidus) and these solder alloys are known as eutectic alloys. As heat
is applied to a eutectic alloy, the solder passes directly from solid
to liquid instantaneously at the eutectic melting point of the solder.



My comments follow:

First, I must applaude the effert of both Tom and the other poster to
take an experimental approach to the problem and try and understand
the differences between the "book values" for solder melting point and
the observation that in practice it requires higher applied
temperature to melt solder.

One problem with the types of measurements described by Tom and the
poster from the other group is temperature gradients. That is the
temperature of the solder is not the same as the temperature of the
thermometer. For instance, taking a hot soldering iron at a
temperature and touching a piece of solder. The heat immediately flows
down the solder. This is due to the high thermal conductivity of the
solder. This keeps the solder at a lower temperature than the tip and
also lowers the temperature of the tip. The heater in the may not have
enough power to restore the temperature of the tip. Even if it does it
will take some time for the temperature to come back to its steady
state value. Hence it is necessary to have the tip at a higher
temperature than the liquidus temperature for the solder to melt.

Even in the experiment Tom describes, the heat loss from the toaster
oven was large. These heat losses also means gradients will exist and
the solder is not at the same temperature as the thermometer. Phase
diagrams for solder, or any material for that matter, require very
careful control experiments to accuractely determine the temperature
of the material and to ensure all of the material at the same
temperature. At least nearly so.



Regards

Jeff Lindemuth


"Tom Quackenbush" wrote in message
...
Specifically, how do you know when a lead alloy has reached it's
liquidus temperature?

On another newsgroup, a poster mentioned that the solder attaching
his LED to the PCB melted, therefore he knew that the temperature

must
have reached 720 degrees F. I responded, asking what kind of solder

he
was using, since 60/40 melts somewhere around 370 deg. F.

I know what the published values for the melting points of various
solders are, bear with me.

Original poster then says, I just measured it, my 60/40 solder

melts
at 600 deg. F., what temperature does yours melt at and I don't want
to know what the charts say, I want to know what you measure.

Ok, I've got nothing better to do tonight and how can hard this

be?
I've got the ingredients - various lead solders, toaster oven,

decent
thermometer.

Problem #1 - my little toaster oven doesn't't like to reach 380.

deg
F., let alone the 450 deg indicated on its dial. OK, I don't really
trust dials like that anyway.

Problem #2 - The big one. How do you know when your lead alloy
melts? What are the visual indications?


Here's a copy of the results that I posted on the other newsgroup
(references to the other poster are removed):

My sample melts at 600 degrees Farenheit. Yours? Dunno. Do the
test. But let's skip the bull****. Do the ****ing test and tell

me
what you come back with. Don't give me a spec sheet result. Give

me
a Real World result.


Let me begin by saying that I don't doubt the published figures

for
the melting points of lead alloys. But, as you say, seeing is
believing, and I believe that personal observation is always

valuable
(in more ways than one - you may find an error in the accepted

values,
or you may learn something that your predecessors already learned).

OK, then. All degrees are Fahrenheit.

I simultaneously tested two samples each of 50/50 (solid, ~ .125
dia )and 60/40 rosin core (~.0625 dia.). One piece of each was laid
flat, one piece of each was bent into the shape of a coiled snake,
ready to strike (I'm thinking that it may be easier to detect

"slump"
in the vertical section).

I'm using my toaster oven for heating. The solder pieces are
resting on a piece of cast iron (about 3/16" thick) which rests on

an
aluminum tray. The surface of the cast iron is a combination of
grease and burnt grease(carbon). I fashioned a cap from heavy

aluminum
foil to shield the whole shebang from the upper heating element.

I'm using a Fluke 16 to measure the temperature. The thermocouple
is clipped to the center of the cast iron piece.

It took about 30 min to raise the temperature to 350 deg. From

350
degrees the temperature was increasing at (_very_ rough

approximation)
1 degree per 10 seconds. At 370 deg., the temperature was increasing
at less than 1 deg. per minute. At about 372 deg., I plugged the

gaps
around the glass door with aluminum foil, and the temperature began
increasing at a tolerable rate (roughly 1 degree in 30 seconds),

until
it reached another plateau at about 381 degrees. BTW, the

temperature
dial on my toaster oven goes up to 450 degrees, then broil. Even at
the "broil" setting, I'm unable to reach 390 degrees in this thing.

The results? Somewhat inconclusive:
(I've decided not to follow your example and won't bother listing
temperatures where nothing changed)

Deg. F.

364 - 60/40 Vertical sample begins to slump
366 - 60/40 Vertical sample collapsed (vertical portion fell

across
horizontal portion)
368 - 50/50 Vertical sample slumped and collapsed (vertical

portion
did not fall across the horizontal portion)
369 - 60/40 Vertical - where the vertical portion fell across the
horizontal portion, the intersection has now fused into a smooth
lump.
371 - All undisturbed portions of samples (both 50/50 and 60/40)
have developed a sheen and appear distorted (elliptical rather than
circular cross-section).
377 - 50/50 samples clearly deformed & flowing downhill. 60/40
appears much as it did at 371 degrees.
382 - I think my toaster oven has peaked out. Solder samples

appear
the same as at 377 degrees.

After waiting 45 minutes of steady 381 to 382 deg. temperatures I
stopped the experiment. I opened the oven door and dragged a steak
knife through all the samples. The effect was similar to that as

when
you drag your finger through molten candle wax - liquid, but
solidifying very quickly.

Conclusions:

1. Passed solidus temperature for both alloys at 368 degrees.
References claim solidus temperature is 361 degrees. I assume that

the
discrepancy lies in my crude setup.

2. I've realized that I'm not sure how to identify when the alloy

has
reached its liquidus temperature. The cylinders (solder clippings)
never pooled into a ball, but does that mean that they didn't reach
their liquidus temperature or that they _did_ reach their liquidus
temperature and surface tension caused them to retain an

approximation
of their original shape (anyone that has soldered knows something of
the effects of surface tension on solder).

3. An oven that reach 500 degrees would be nice.

R,
Tom Q.

p.s. I'll be asking on r.c.m for advice.



  #2   Report Post  
ATP
 
Posts: n/a
Default How do tell a liquid from a solid?

Tom Quackenbush wrote:
Specifically, how do you know when a lead alloy has reached it's
liquidus temperature?

On another newsgroup, a poster mentioned that the solder attaching
his LED to the PCB melted, therefore he knew that the temperature must
have reached 720 degrees F. I responded, asking what kind of solder he
was using, since 60/40 melts somewhere around 370 deg. F.

I know what the published values for the melting points of various
solders are, bear with me.

Original poster then says, I just measured it, my 60/40 solder melts
at 600 deg. F., what temperature does yours melt at and I don't want
to know what the charts say, I want to know what you measure.

Ok, I've got nothing better to do tonight and how can hard this be?
I've got the ingredients - various lead solders, toaster oven, decent
thermometer.

I hope this is not the toaster oven you heat up snacks in. You will probably
end up with significant lead contamination.


  #3   Report Post  
Wild Bill
 
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Default How do tell a liquid from a solid?

The obnoxious dude that said the LED lead had separated at 720 is most
likely mistaken.
Regardless of what makes him think so (digital display on his soldering
station or whatever), it's very unlikely.
Component connections on mass produced equipment can fail without any
appreciable heat.

I've got a soldering station analyzer and a thermocouple calibrator, and
these instruments are barely adequate for an accurate analysis of the
proposed scientific test. Many types of thermocouples degrade/derate quickly
when exposed to high temperatures.

A component's leads soldered to copper traces on a resin/glass board will
prove to be individually different. Another factor is if it's a factory
solder, or if it's a generic consumer solder.

I would be certain that a fairly accurate comparison (not an accurate
definitive test) could be accomplished with a thermocouple securely attached
to a soldering iron tip, and having the tip positioned where you could hang
a loop of wire solder on the tip. As you monitor the increasing tip
temperature rise to the point where the solder loop lets go, this temp can
be used to compare it to a different alloy or brand.
The final result will only be a fairly decent comparison.

Soldering iron temperatures are normally much higher than the melting point,
otherwise the iron tip would have to sit on the connection until the
connection equaled the minimal tip temp. This could take a while, depending
upon the thermal mass of the iron, the heat transfer rate (a dry tip doesnt
transfer heat well), the thermal conduction rate/dissipation of the
connection, and finally the solder melting point.

If all of our electronic stuff was soldered at a minimal temp, none of the
connections would be any good, because of the previously mentioned cold or
dry joint connection. Thermal cycling would probably cause the components to
fall of the circuit boards.
Mass production solders for surface mount components are generally pastes
and can be "set" by oven heat.

WB
................

"Tom Quackenbush" wrote in message
...
Specifically, how do you know when a lead alloy has reached it's
liquidus temperature?

On another newsgroup, a poster mentioned that the solder attaching
his LED to the PCB melted, therefore he knew that the temperature must
have reached 720 degrees F. I responded, asking what kind of solder he
was using, since 60/40 melts somewhere around 370 deg. F.



R,
Tom Q.

p.s. I'll be asking on r.c.m for advice.



  #4   Report Post  
ATP
 
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Default How do tell a liquid from a solid?

Tom Quackenbush wrote:
ATP wrote:

Tom Quackenbush wrote:

snip

Ok, I've got nothing better to do tonight and how can hard this
be? I've got the ingredients - various lead solders, toaster oven,
decent thermometer.

I hope this is not the toaster oven you heat up snacks in. You will
probably end up with significant lead contamination.

Better safe than sorry, I'm sure, but how would the lead
contaminate the toaster oven? I was barely able to melt the stuff, let
alone boil it. Are there lead compounds involved that may have
vaporized? Does metallic lead sublimate or evaporate at temperatures
this low (under 400 degrees F.)?

R,
Tom Q.


I'm not an industrial hygienist, or even a dental hygienist, but I can tell
you the thresholds are extremely low, for example 15 ppb in drinking water
IIRC, and lead rubs off very easily, so as you are handling the solder etc.,
some is getting on your toaster oven. May not do you that much harm, but
would not be good for your kids/grandkids.


  #5   Report Post  
Ed Huntress
 
Posts: n/a
Default How do tell a liquid from a solid?

"Tom Quackenbush" wrote in message
...

I may try again, placing the solder samples on a cleaned & fluxed
piece of copper this time. I'll pick up some 63/37 solder to try, as
well. I don't think my toaster oven is capable of reaching the
liquidus temperature of the 50/50 solder, though.


Be aware that if you place the solder on copper, or on any other metal with
which it will amalgamate, and if you heat it slowly, you will wind up with
intermetallic compounds in the solder that will keep raising its melting
temperature as your experiment proceeds.

This is the principle of "transistional" soldering, which is used in some
industries to produce higher-temperature joints than the solder itself would
indicate. Anyone who has de-soldered big joints on copper wire, especially
those that were overheated, has likely encountered this phenomenon.

Ed Huntress





  #6   Report Post  
jim rozen
 
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Default How do tell a liquid from a solid?

In article , Ed Huntress
says...

Be aware that if you place the solder on copper, or on any other metal with
which it will amalgamate, and if you heat it slowly, you will wind up with
intermetallic compounds in the solder that will keep raising its melting
temperature as your experiment proceeds.


Err, not *always*. Try to solder some gold wire
with lead/tin solder, Ed! You might be suprised
at the result.



Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

  #7   Report Post  
Ed Huntress
 
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Default How do tell a liquid from a solid?

"jim rozen" wrote in message
...
In article , Ed

Huntress
says...

Be aware that if you place the solder on copper, or on any other metal

with
which it will amalgamate, and if you heat it slowly, you will wind up

with
intermetallic compounds in the solder that will keep raising its melting
temperature as your experiment proceeds.


Err, not *always*. Try to solder some gold wire
with lead/tin solder, Ed! You might be suprised
at the result.


I'm not likely ever to encounter gold wire in my soldering experiences. g
Try it with some copper water tubing that was a bit overheated when the
original joint was made, and almost everyone is surprised. It can be a b*tch
to pull apart; it squeeks from the friction of the hard intermetallics; and
it just may freeze up on you and refuse to come apart until you nearly melt
the parent metal.

Most common metals that solder can wet will alloy to some degree with the
solder. The result is a tutti-fruiti mess of intermetallic compounds. They
embrittle the joint in many cases; they lead to unpredictable freezing and
crystalization; and they can either strengthen or weaken the joint depending
on what's mixed and at what temperatures. Usually, the result is bad. But
the phenomenon can be carefully engineered to produce a stronger,
higher-temperature joint, when it's done intentionally.

The extreme example of this actually is a brazing technique, in which a
small percentage of bismuth is added to what actually is a parent-metal
alloy, and the joint is soaked at a slowly increasing temperature. The end
result is a joint that melts at the same temperature as the parent metal.

Anyway, the most common way most of us run into this is when we try to
disassemble old soldered copper or brass plumbing. It can be very surprising
if the original joint was overheated.

Ed Huntress



  #8   Report Post  
jim rozen
 
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Default How do tell a liquid from a solid?

In article , Ed Huntress
says...

I'm not likely ever to encounter gold wire in my soldering experiences. g


Gold and lead form an intermetallic with a much lower
melting point than either of the two parent metals.
So as one begins to add in a bit of solder into the
joint, the gold wire simply sucks into the melt.

For making small connections with fine gold wires,
indium is a good solder to use. A new iron tip is
a must though!

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

  #10   Report Post  
Don Young
 
Posts: n/a
Default How do tell a liquid from a solid?

I am not sure just how it might be accomplished, but I think the best
experiment would be to melt or freeze a decent size sample with a
thermocouple imbedded and a recording indicator. I think there would be a
temperature "knee" or plateau to define the phase changes.

Don Young

"Tom Quackenbush" wrote in message
...
Specifically, how do you know when a lead alloy has reached it's
liquidus temperature?

On another newsgroup, a poster mentioned that the solder attaching
his LED to the PCB melted, therefore he knew that the temperature must
have reached 720 degrees F. I responded, asking what kind of solder he
was using, since 60/40 melts somewhere around 370 deg. F.

I know what the published values for the melting points of various
solders are, bear with me.

Original poster then says, I just measured it, my 60/40 solder melts
at 600 deg. F., what temperature does yours melt at and I don't want
to know what the charts say, I want to know what you measure.

Ok, I've got nothing better to do tonight and how can hard this be?
I've got the ingredients - various lead solders, toaster oven, decent
thermometer.

Problem #1 - my little toaster oven doesn't't like to reach 380. deg
F., let alone the 450 deg indicated on its dial. OK, I don't really
trust dials like that anyway.

Problem #2 - The big one. How do you know when your lead alloy
melts? What are the visual indications?


Here's a copy of the results that I posted on the other newsgroup
(references to the other poster are removed):

My sample melts at 600 degrees Farenheit. Yours? Dunno. Do the
test. But let's skip the bull****. Do the ****ing test and tell me
what you come back with. Don't give me a spec sheet result. Give me
a Real World result.


Let me begin by saying that I don't doubt the published figures for
the melting points of lead alloys. But, as you say, seeing is
believing, and I believe that personal observation is always valuable
(in more ways than one - you may find an error in the accepted values,
or you may learn something that your predecessors already learned).

OK, then. All degrees are Fahrenheit.

I simultaneously tested two samples each of 50/50 (solid, ~ .125
dia )and 60/40 rosin core (~.0625 dia.). One piece of each was laid
flat, one piece of each was bent into the shape of a coiled snake,
ready to strike (I'm thinking that it may be easier to detect "slump"
in the vertical section).

I'm using my toaster oven for heating. The solder pieces are
resting on a piece of cast iron (about 3/16" thick) which rests on an
aluminum tray. The surface of the cast iron is a combination of
grease and burnt grease(carbon). I fashioned a cap from heavy aluminum
foil to shield the whole shebang from the upper heating element.

I'm using a Fluke 16 to measure the temperature. The thermocouple
is clipped to the center of the cast iron piece.

It took about 30 min to raise the temperature to 350 deg. From 350
degrees the temperature was increasing at (_very_ rough approximation)
1 degree per 10 seconds. At 370 deg., the temperature was increasing
at less than 1 deg. per minute. At about 372 deg., I plugged the gaps
around the glass door with aluminum foil, and the temperature began
increasing at a tolerable rate (roughly 1 degree in 30 seconds), until
it reached another plateau at about 381 degrees. BTW, the temperature
dial on my toaster oven goes up to 450 degrees, then broil. Even at
the "broil" setting, I'm unable to reach 390 degrees in this thing.

The results? Somewhat inconclusive:
(I've decided not to follow your example and won't bother listing
temperatures where nothing changed)

Deg. F.

364 - 60/40 Vertical sample begins to slump
366 - 60/40 Vertical sample collapsed (vertical portion fell across
horizontal portion)
368 - 50/50 Vertical sample slumped and collapsed (vertical portion
did not fall across the horizontal portion)
369 - 60/40 Vertical - where the vertical portion fell across the
horizontal portion, the intersection has now fused into a smooth
lump.
371 - All undisturbed portions of samples (both 50/50 and 60/40)
have developed a sheen and appear distorted (elliptical rather than
circular cross-section).
377 - 50/50 samples clearly deformed & flowing downhill. 60/40
appears much as it did at 371 degrees.
382 - I think my toaster oven has peaked out. Solder samples appear
the same as at 377 degrees.

After waiting 45 minutes of steady 381 to 382 deg. temperatures I
stopped the experiment. I opened the oven door and dragged a steak
knife through all the samples. The effect was similar to that as when
you drag your finger through molten candle wax - liquid, but
solidifying very quickly.

Conclusions:

1. Passed solidus temperature for both alloys at 368 degrees.
References claim solidus temperature is 361 degrees. I assume that the
discrepancy lies in my crude setup.

2. I've realized that I'm not sure how to identify when the alloy has
reached its liquidus temperature. The cylinders (solder clippings)
never pooled into a ball, but does that mean that they didn't reach
their liquidus temperature or that they _did_ reach their liquidus
temperature and surface tension caused them to retain an approximation
of their original shape (anyone that has soldered knows something of
the effects of surface tension on solder).

3. An oven that reach 500 degrees would be nice.

R,
Tom Q.

p.s. I'll be asking on r.c.m for advice.





  #11   Report Post  
ERich10983
 
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Default How do tell a liquid from a solid?

Just a thought. You are trying to apply the heat externally and measuring the
air temperature surrounding the solder sample.

Since the solder is a thick wire, how about just attaching a thermocouple to
the solder piece with an insulating pad under it and then running current
through the solder section to heat it up. A low voltage transformer with a
variac on the primary could control the temperature.

Ideally, you would measure the temperature with a non-contact optical
thermometer.

Earle Rich
Mont Vernon, NH
  #12   Report Post  
Spehro Pefhany
 
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Default How do tell a liquid from a solid?

On Sun, 21 Dec 2003 09:19:43 -0500, the renowned Tom Quackenbush
wrote:

Don Young wrote:

I am not sure just how it might be accomplished, but I think the best
experiment would be to melt or freeze a decent size sample with a
thermocouple imbedded and a recording indicator. I think there would be a
temperature "knee" or plateau to define the phase changes.


That sounds promising.


Yes, I like this method. It will answer the question about the
temperature, but not about what the ideal temperature is for
soldering. Of course, for non-eutectic alloys there will be a range of
temperature. The T/C ideally would be a grounded junction very thin
mineral insulated type with an immersion in the metal of 5-10x the
diameter of the probe. You should be able to get within 1°C.

I think my experiments are at an end for now, but the behavior of
lead/tin alloys between the solidus and liquidus temps remains a
mystery to me. Just what the heck are those Sn and Pb atoms doing?


Here's a cute description from a brazing alloy supplier for that slice
of the phase diagram:

"Just above the solidus temperature, the mixture will be mostly solid
with some liquid phases (like the consistency of snow, but hotter!).
Just below the liquidus temperature, the mixture will be mostly liquid
with some solid phases (like sleet)".

BTW, moving the solder when it is between solidus and liquidus is
where "cold" solder joints come from- that granular dull appearance,
and poor strength. Like moving the jello before it's done..

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
  #13   Report Post  
ERich10983
 
Posts: n/a
Default How do tell a liquid from a solid?


That sounds like it would work. I'd probably end up with a tinned
thermocouple before too long - I'm not sure if, or how, that might
affect the accuracy of subsequent readings.

That is why I recommended an isolating pad between the metal and thermocouple.
Something with good thermal conductivity.

Ideally, you would measure the temperature with a non-contact optical
thermometer.


I'm not very familiar with them. Don't infra-red thermometers have
issues with shiny surfaces? It seems like 300 degree metal with a
rough black surface would emit more IR than the same 300 degree metal
with a polished, silver surface.


The ones I've used from Omega, Ircon and Micron are pretty good, especially at
the low temperatures we are talking about. They are really useful when we got
up to 2200C. Thermocouples really don't last long at that temperature. We were
holding better than 1 degree for long periods of time.

Anyway, ideally, you would have a cavity in the sample and aim the non-contact
thermocouple inside that hole to simulate a black-body target. I never saw any
great difference in temperature readings because of differences in the color or
polish of the metal.

One of the differences in cost of these devices is the optics which allow you
to read to a narrow angle. The tighter angle means a smaller area is read.
Sometimes you want to average over a large area and other times you need spot
readings. Check out the Omega website for details on various options.

Usual disclaimers.

Earle Rich
Mont Vernon, NH
  #14   Report Post  
Eastburn
 
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Default How do tell a liquid from a solid?

At work we have some ''' negative solder ''' - laugh laugh - but what it
is, is simply a stick of other metal that drops the melting temp.

We use it to take a part off side 1 of a two sided pcb with heat coming
from the other or back side. The parts on the bottom don't drop off
since
the temp is much to low, but the amalgam (sp) of the metals drop the
melting point.

I want to say - can't recall - it is bismuth or an alloy of it and
something else.

Martin
--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder
  #15   Report Post  
Eastburn
 
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Default How do tell a liquid from a solid?

Solder that is 63/37 is not normal off the hobby shelf type. -
It should be elsewhere. I think the comment of "Electrical" -
that means rosin flux not acid flux.

Electronics and electrical uses span the range of ratios -
I have some with 5% silver for use with the silver-lead-Tin plate
on ceramic. The silver is used so the solder doesn't pull out
the silver that is making the initial contact to the ceramic.

Martin
--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder


  #16   Report Post  
Don Wilkins
 
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Default How do tell a liquid from a solid?

On Sun, 21 Dec 2003 09:19:43 -0500, Tom Quackenbush
wrote:

,;Don Young wrote:
,;
,;I am not sure just how it might be accomplished, but I think the best
,;experiment would be to melt or freeze a decent size sample with a
,;thermocouple imbedded and a recording indicator. I think there would be a
,;temperature "knee" or plateau to define the phase changes.
,;
,; That sounds promising.
,;
,; I think my experiments are at an end for now, but the behavior of
,;lead/tin alloys between the solidus and liquidus temps remains a
,;mystery to me. Just what the heck are those Sn and Pb atoms doing?
,;
,; Thanks for the response.




Google "lead tin phase diagram" (with the quotes)

http://www2.umist.ac.uk/material/res...e/pbsndiag.htm

For a nice phase diagram.
  #17   Report Post  
Old Nick
 
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Default How do tell a liquid from a solid?

On Sat, 20 Dec 2003 16:02:10 GMT, "ATP"
wrote something
.......and in reply I say!:

Isn't there far more risk from either taking in the lead through the
skin/cuts, or licking your fingers (rubbing your mouth), or even
simply soldering and inhaling the fumes?

15ppb in drinking water means that you could take in quite a bit over
time.

Better safe than sorry, I'm sure, but how would the lead
contaminate the toaster oven? I was barely able to melt the stuff, let
alone boil it. Are there lead compounds involved that may have
vaporized? Does metallic lead sublimate or evaporate at temperatures
this low (under 400 degrees F.)?

R,
Tom Q.


I'm not an industrial hygienist, or even a dental hygienist, but I can tell
you the thresholds are extremely low, for example 15 ppb in drinking water
IIRC, and lead rubs off very easily, so as you are handling the solder etc.,
some is getting on your toaster oven. May not do you that much harm, but
would not be good for your kids/grandkids.


************************************************** ** sorry
remove ns from my header address to reply via email

I was frightened by the idea of a conspiracy that was
causing it all.
But then I was terrified that maybe there was no plan,
really. Is this unpleasant mess all a mistake?
  #18   Report Post  
jim rozen
 
Posts: n/a
Default How do tell a liquid from a solid?

In article , Old Nick says...

Isn't there far more risk from either taking in the lead through the
skin/cuts, or licking your fingers (rubbing your mouth), or even
simply soldering and inhaling the fumes?


Lead solder had a fairly low vapor pressure. So low
that in practice the dominant form of intake is hand to
mouth.

Anyone who does a great deal of soldering, be it
electronic or plumbing (and DWV systems are still
done with 50/50 IIRC) then they should make it
a hard and fast rule to wash their hands before
eating or drinking anything.

Jim

==================================================
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  #19   Report Post  
Jeff Wisnia
 
Posts: n/a
Default How do tell a liquid from a solid?

Ed Huntress wrote:

snipped

I'm not likely ever to encounter gold wire in my soldering experiences. g
Try it with some copper water tubing that was a bit overheated when the
original joint was made, and almost everyone is surprised. It can be a b*tch
to pull apart; it squeeks from the friction of the hard intermetallics; and
it just may freeze up on you and refuse to come apart until you nearly melt
the parent metal.


Hey thanks Ed! I've experienced that effect with copper plumbing fittings many
times, but never learned what caused it.

Jeff

--
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can keep smiling when things go wrong, you've thought of someone to
place the blame on."



  #20   Report Post  
Jeff Wisnia
 
Posts: n/a
Default How do tell a liquid from a solid?

Tom Quackenbush wrote:

Specifically, how do you know when a lead alloy has reached it's
liquidus temperature?


snipped

p.s. I'll be asking on r.c.m for advice.


************************************************** *************

Thanks for reminding me that on my first job I got chewed out roundly by
the boss who screamed at me in front of the other guys in the lab,

"You klutz, even an asshole can tell the difference between the three
states of matter!"

(Solid, liquid and gas.)

************************************************** ********

Not really a true story, but I couldn't resist...G

Happy New Year guys,

Jeff

--
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can keep smiling when things go wrong, you've thought of someone
to place the blame on."




  #21   Report Post  
Ed Huntress
 
Posts: n/a
Default How do tell a liquid from a solid?

"Jeff Wisnia" wrote in message
...
Ed Huntress wrote:

snipped

I'm not likely ever to encounter gold wire in my soldering experiences.

g
Try it with some copper water tubing that was a bit overheated when the
original joint was made, and almost everyone is surprised. It can be a

b*tch
to pull apart; it squeeks from the friction of the hard intermetallics;

and
it just may freeze up on you and refuse to come apart until you nearly

melt
the parent metal.


Hey thanks Ed! I've experienced that effect with copper plumbing fittings

many
times, but never learned what caused it.


One thing that can help is to start putting tension on the joint as you heat
it. Just when it passes the melting point of the solder, it's most likely to
come apart without trouble. Work fast.

Ed Huntress


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