Tin Whiskers

[Llew]

Using lead-free solder causes tin whiskersto form on circuit boards and components. Pure tin-plated components also cause the whiskers to form over time -

_http://nepp.nasa.gov/WHISKER/photos/index.html

Tin/lead solder is now banned for sale in Europe because of damage to the environment (for instance Maplin only have the lead-free solder now). Lead-free solder needs a greater melting point to solder effectively, which can damage the components you are using it on. Luckily I have enough of the old stuff for my projects.

Not sure if equipment manufactured in the Asia have to use lead-free, but apparently baffling faults in PC motherboards etc. could be put down to the whisker effect.

In 1998 the failure of the Galaxy IV satellite was diagnosed as being caused by the dreaded whiskers.

Llew

 

[PaulR]

Much more of a hobbyist than you Llew but I've also a small supply of 60/40 to see me through to senility.

It's still available at radio rallies fortunately but who knows for how long?

 

[2cvbloke]

Maybe that's why Meths and a toothbrush works on some laptop motherboards when they conk out... .

 

[meldrew]

I read about this in a copy of today's Guardian left on my
train home from work. My solder is now over 50 years old
but in short supply!

 

[Channel Hopper]

If you are not dead yet, I wonder why the stuff is now banned.

 

[Llew]

LOL, I worked at Pye TV for a few years, and my first job was flow-soldering PCB boards by dipping them in a bath brim-full of solder, which we replenished frequently by melting in sticks of 60/40.

Boards were first covered with flux (using a decorator's paint brush).

No temperature control of the solder that I remember - we sometimes over-baked the board!

Failure rate was about 10%. Main problems -

Aforementioned over-baking, destroying the print

Solder too cool - large clumps of solder all over the print

Inadvertently dipping the board too far in - solder all over the component side (!)

Plenty of noxious fumes about, no health'n'safety issues back then. I seem to have survived the experience, despite doing it eight hours a day for a few weeks

Later a revolving arm driven by a motor was produced, with the boards clamped to holders. This was a little more precise regarding getting the boards to skim the bath correctly; still some failures due to incorrect temperature. It had a fume extractor of sorts, don't think there was a fan though.


Llew

 

[Channel Hopper]

Ah, forgot to mention brain damage earlier.

Thanks for the reminder Llew. ;)