[Boatanchors] Kester 88

Tue Sep 27 12:50:39 EDT 2011

Eutectic solder e.g. 63/37 will not age,crystalize or, ....  The reason that 
non-eutectic solder fails is the lead and tin components solidify at 
different temperatures causing a jillion molecular connections whereas 
Eutectic components solidify at the same temperature resulting in one 
massive connection.  You will notice that Eutectic does not puddle but 
becomes solid very quickly.  The puddling effect of non-eutectic solder is a 
result of one element becoming solid while the other remains liquid ---  
slowly solidifying creating one connection at a time.  A good example is if 
60/40, non-eutectic solder is used in a high power high current amplifier 
design, the joint will begin to fail after about 10 years.  The process is 
slow but it will eventually fail.  What happens?  The jillion individual 
molecular connections that occur when using non-eutectic solder fail one at 
a time causing the resistance of the connection to increase, further loading 
those that remain.  The result will be a joint composed of burnt individual 
connections that as a whole appear to be crystalized.  Use 63/37 and 
whatever core you please --- it will outlast you.

Eutectic solder comes in a dozen different variations, some with other 
elements.  Some have very high tin content.  Don't be terrorized by the 
notion that high tin concentrations will result in massive parasitic tin 
whiskers reaching out to every electrical outlet, bed spring, or sleeping 
pet, bent on extinguishing all life on earth.  Think it through.  Tin 
whiskers are so thin that a few micro amps will vaporize them.  A human hair 
is 1000 times as thick.  They only grow to less than a centimeter.  Now if 
your boat anchor cannot rid itself of one of these creatures with a simple 
cough should one occur, it's probably using super high impedance close 
spaced solid state devices like PCB FET`s which can be vulnerable.

Tin whiskers, Palladium depletion, silver migration etc. are a problem but 
not one that I would expect or have found in a boat anchor.

Kindest regards Jim K9AXN

------------------------------

Message: 2
Date: Mon, 26 Sep 2011 13:15:19 -0600
From: Robert Moses <rhmoses at earthlink.net>
Subject: Re: [Boatanchors] Kester 88
To: Boatanchors at mailman.qth.net
Message-ID: <4E80CF47.50305 at earthlink.net>
Content-Type: text/plain; charset=us-ascii; format=flowed

Materials tend to segregate into like with like over time. In a solid
matrix the matrix tends to prevent this from actually happening. In
addition eutectic mixtures are especially stable and so this is the real
reason that eutectic solder is so favored in spite of the high tin
content and thus high cost. If vibration takes place with solder that is
warmed to the point of partial melting then the solder joint will
crystalize and start acting intermitent or as a diode instead of as a
conductor. Again, eutectic mixtures fare better since they tend not to
seperate. The prefered tin lead solder is about 63% tin and 37% lead
mixture that has been saturated with copper. (The copper reduces the
tendency to disolve copper soldering iron tips.) If the flux ages and
degrades then the solder will fail to wet the joint and the work will
usually fail early. (Solder that has 50% or more lead is popular due to
the fact that it does not have a sharp melting point and so can be
worked over a fairly wide temperature range. Plumbers like that. It also
costs less.) When soldering it is critical that all electrical surfaces
be heated to the solder melting point and that they be clean so that the
solder will wet them (Flux is VERY helpful here.) And, finally, that the
work be kept in a fixed position with absolutely NO movement as the
solder cools and freezes. For electrical work use only a non-corrosive
flux since an acid flux will eat through the wires fairly quickly and if
under insulation the breaks can be quite frustrating to locate. Do this
and use the right amount of solder in each joint and you will not have
bad solder joints. It is very tedious and critical to get it right (in
all regards: temperature of all soldered surfaces, clean surfaces, no
movement while cooling) if you want good quality.

Richard Knoppow wrote:

>----- Original Message ----- 
>From: "J. Forster" <jfor at quikus.com>
>To: <WA5CAB at cs.com>
>Cc: <boatanchors at mailman.qth.net>
>Sent: Wednesday, September 14, 2011 2:44 PM
>Subject: Re: [Boatanchors] Kester 88
>
>
>
>
>>I doubt it.
>>
>>Lead is pretty darn non-reactive. It's on windows that are
>>nearly 1000
>>years old. It is also used to line chemical tanks and for
>>process piping.
>>
>>IMO, it's from somewhere in an irrational gevernment spec
>>or other...
>>probably from the assumption everything must have a shelf
>>life. Like
>>Teflon tubing.
>>
>>Best,
>>
>>-John
>>
>>
>
>     Somewhere there must be an explanation of what exactly
>happens to solder when it ages. I note that an earlier post
>states that the shelf life of solid wire solder is
>substantially longer than cored solder. So, is it the flux
>core itself or a reacation of the metals with the core?
>This must be based on research of some sort. Does old solder
>make bad joints? What about soldered joints, do they also
>age? I think they do because we have all encountered bad
>solder joints. Usually this is blamed on poor soldering
>technique but perhaps that is not always the cause. I know
>that vibration can cause solder joints to crystalize with
>time. All the answers must lie in the technical literature
>somewhere.
>     BTW, solder is also sold in ingots for use in solder
>pots, how does this compare with wire solder for aging?
>     I am another that thought that solder was forever. I
>guess nothing is forever.
>
>
>--
>Richard Knoppow
>Los Angeles
>WB6KBL
>dickburk at ix.netcom.com
>
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