[Boatanchors] Kester 88

Tue Sep 27 13:16:18 EDT 2011

Jim has one key point, that of whiskers. I agree in 99% of BA's this
is not a problem,
but keep it in mind. There is one documented case of a high current
aviation relay that
failed from them.

http://www.hlinstruments.com/RoHS_articles/davy2002_relay%20failure%20caused%20by%20tin%20whiskers.pdf

-pete

On Tue, Sep 27, 2011 at 9:50 AM, James Liles <james.liles at comcast.net> wrote:
> 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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>
>
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