printed circuit board (PCB)

Using a Disk Mill PULVERISETTE 13 as desired is not possible. The sample contains foils which will pass the smallest gap of the disk mill without getting ground. Small board pieces will smear and scratch between the disks and metal pieces can shorten the durability of bearings when they are not brittle enough.

Especially bigger metal fragments can cause damages when e.g. a Universal Cutting Mill PULVERISETTE 19 will be used for grinding. By using a rotor with indexable knives, damaged knives are easier to replace with such a tool. Neither Disk Mill PULVERISETTE 13 nor Universal Cutting Mill PULVERISETTE 19 are able to grind the sample to < 100 µm as desired.

For this, only a planetary mill is coming into question.

Foil sample has been ground fine. Some (probably fiber-glass reinforced) board pieces are still present after 10 and after 20 minutes of grinding. The size of the board pieces slowly gets reduced. Also the temperature of the grinding bowl use to rises continually. After 10 minutes, the outside of the bowl use to be > 50°C. We aborted grinding after 20 minutes and sieve the complete sample with a test sieve of 710 µm mesh.

Still 6g (~ 2,9%) of sample is too coarse to pass the test sieve. Coarse particles use to be mainly maid of pure metal pieces which became flattened out by the grinding balls.

If steel balls are not able grinding the sample, probably grinding balls made of hardmetal tungsten carbide might be able to.

For this, we used a 250 ml bowl made of tungsten carbide and 6x 30 mm Ø WC grinding balls in this test.

Sample got ground faster, all board particles have been fine ground, but still metal pieces will became flattened out. The achieved fineness is a comparable to result 1 – about 3,2 % of sample remains bigger as 710 µm (determined by sieving with Vibratory Sieve Shaker ANALYSETTE 3 Pro).

Coarse fractions have been packed separately after sieving and use to be attached to the packed sample.