[Boatanchors] Kester 88

Robert Moses rhmoses at earthlink.net
Mon Sep 26 15:15:19 EDT 2011


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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