Scrap plastic as Blasting Media worth more than copper

Originally Posted by miked

I am interested in how you might envision a process to remove perhaps solder traces so components could be easily removed and processed separately.

Mike when my $500.00 Garmin GPS became intermittent then finally quitting altogether I blamed tin whiskers, apparently I may have been wrong. I lived in rural Manitoba with winters well below freezing, leaving the Garmin inside my truck at all times.



Allotropic transformation

At 13.2 degrees Celsius (about 56 degrees Fahrenheit) and below, pure tin transforms from the silvery, ductile metallic allotrope of β-form white tin to brittle, nonmetallic, α-form grey tin. The transformation is slow to initiate due to a high activation energy but the presence of germanium (or crystal structures of similar form and size) or very low temperatures ~-30 degrees Celsius aids the initiation. There is also a volume increase associated with the phase change. Eventually the α-form decomposes into powder, hence the name tin pest.^[3]
The decomposition will catalyze itself, which is why the reaction speeds up once it starts; the mere presence of tin pest leads to more tin pest. Tin objects at low temperatures will simply disintegrate.


Tin metal when exposed to low temperatures breaks down, the procedure is called Tin Pest, I suspect the Garmin circuits had lead free solder mostly composed of tin which I have come to learn breaks down in the cold. Below are some historical events involving tin.

It looks to be any board soldered with tin will break down when cold, so freezing your boards maybe to easiest method of removing components. Just do not use the home freezer that you store your food in, plenty of old beat up freezers out there that still work.

Possible historical examples

Scott expedition to Antarctica

In 1910 British polar explorer Robert Scott hoped to be the first to reach the South Pole, but was beaten by Norwegian explorer Roald Amundsen. On foot, the expedition trudged through the frozen deserts of the Antarctic, making for caches of food and kerosene deposited on the way in. In early 1912, at the first cache, there was no kerosene; the cans - soldered with tin - were empty. The cause of the empty tins could have been related to tin pest, and some observers blame poor quality soldering, although tin cans over eighty years old have been discovered in Antarctic buildings with the soldering in good condition.

Napoleon's buttons http://everything.explained.today/Tin_pest/

The story is often told of Napoleon's men freezing in the bitter Russian winter, their clothes falling apart as tin pest ate the buttons. Whether failing buttons were indeed a contributing factor in the failure of the invasion remains disputed; critics of the theory point out that the tin used would have been quite impure and thus more tolerant of low temperatures. Laboratory tests provide evidence that the time required for unalloyed tin to develop significant tin pest damage at lowered temperatures is about 18 months, which is more than twice the length of Napoleon's Russian campaign.^[4]
Modern tin pest since adoption of RoHS

With the adoption of the Restriction of Hazardous Substances Directive (RoHS) regulations in Europe and California banning most uses of lead, and similar regulations elsewhere, the problem of tin pest has returned, since some manufacturers now use pure tin, but previously used tin/lead alloys. For example, the leads of some electrical and electronic components are plated with pure tin. In cold environments, this can change to α-modification grey tin, which is not electrically conductive, and fall off the leads. After reheating, it changes back to β-modification white tin, which is electrically conductive, and can cause electrical short circuits and failure of equipment. Such problems can be intermittent as the powdered particles of tin move around. Tin pest can be avoided by alloying with small amounts of electropositive metals or semimetals soluble in tin's solid phase e.g. antimony or bismuth, which prevent the decomposition. Silver, indium, and lead have also been used, but lead is not soluble in tin's solid phase.


The time laps video 1 sec = 1 hour.