[Robotgroup] lead free soldering advice

[Leslie Filip]

On May 24, 2007, at 10:01 AM, Def Egge wrote:

> At 01:42  2007-05-24, you wrote:
>> The following message is brought to you by Mr. Poo-Poo:
>>
>> I was talking to an engineer friend who designs circuit boards for a
>> living the other day. He gave me some advice about lead free solder -
>> don't use it. Apparently the lead keeps crystalline "whisker"
>> formations in check. He said the lead free solder starts to corrode
>> immediately after use, and in the process forms microscopic
>> conductive whiskers that grow over time, eventually shorting with
>> other traces. It is for this reason that the US military forbids the
>> use of lead free solder. Apparently they don't want equipment failing
>> in the field. Neither do I. Although in truth I rarely use my
>> equipment these days anyway, much less out in a field.
>>
>> Bye now,
>> Mr. Poo-Poo
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>
>
> How rapidly do these tin whiskers grow?
>
> I understand the continued use of lead-based solders in military and
> satellite applications where mission-critical considerations outweigh
> lead-free considerations.  Certainly, the assured recycling of
> electronic components (the mechanism is left as an exercise to the
> reader) would lessen the probability of exposure to lead, cadmium,
> mercury, etc.
>
> Relatively speaking (compared to the MTBF for individual component
> points-of-failure), how likely are these to be the primary cause of
> consumer-grade electronics failures?  Is the expected useful life of
> your iPod, motherboard, HDTV likely to be affected?
>
>
> All the best....
>
> Mike
>
>
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 From what I heard the corrosion process is unpredictable. Certainly  
it must depend on what specific alloys are being used, the  
application technique, the humidity, the time of day, the price of  
tea in China, and if Joe Blow machine operator was in a good mood or  
not. My guess is that these conductive whiskers would cause  
intermittent problems until they grew enough to become permanent. It  
is also just a guess that the problems probably don't start happening  
until after your warranty expires. Of course, the processes are being  
improved all the time, so I am all for lead free soldering once it is  
reliable.

Mr. Poo-Poo