[Amps] current threads about silver solder and resoldering

[Angel Vilaseca]

Yes, this is what I call an interesting thread!

73

Angel HB9SLV

Le 02.09.2012 21:30, Roger (K8RI) a écrit :
> On 9/2/2012 12:15 PM, Manfred Mornhinweg wrote:
>> Bill,
>>
>>> I recalled that the ratios of lead and tin atoms had to be an integer
>>> to for the lowest melting point.
>>
>> But that's not right either! I hate to be so overly teacherish in this
>> thread, but facts remain facts!
>
> I don't know about the others, but I appreciate jogging this old memory
>
> 73
>
> Roger (K8RI)
>
>
>>
>> In all possible compositions of tin-lead alloys, only one single ratio
>> is eutectic. Exact ratios of atoms such as 1:1, 2:1, 1:2, are NOT
>> eutectic, and fully melt at a higher temperature than the eutectic mix.
>>
>> Have a look at these two web pages for more detailed information, or
>> google for phase diagrams of tin lead solders or other alloys.
>>
>> http://www.ami.ac.uk/courses/topics/0244_tsm/index.html
>>
>> http://spaceflight.esa.int/impress/text/education/Solidification/Phase_Diagrams.html 
>>
>>
>>
>> Note that the eutectic point of tin-lead is given as 61.9/38.1, rather
>> than the conventional 63/37. That's why there is so much 60/40 solder
>> around. The 63/37 solder is only marginally better. The reason to use
>> 63/37 rather than 61.9/38.1 is in the inability to make an absolutely
>> homogeneous alloy, and the fact that the pasty phase is shorter if the
>> mix deviates from the eutectic point toward the tin side, then if it
>> does toward the lead side. So, if the tolerance of an alloy happens to
>> be 2%, it's likely that a nominal 63/37 mix will statistically end up
>> having a shorter pasty range than a nominal 61.9/38.1 mix.
>>
>> Manfred
>>
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>
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