I want to make solder balls with a diameter around 2 mm for electromigration testing. Before this I used a POP mold to make 6 mm solder balls but I cannot use POP mold to make 2 mm solder balls. The size of the ball is not accurate with sharp edges and so on. Is there any other way to make solder balls rather than using a mold?
There is the way of slowly dripping the liquid into a bowl of liquid nitrogen. But I dont know if you can get the required size.
You can do this by starting with solder wire and cutting to length to accurately provide for the volume of your 2 mm dia. solder ball. For example, cut 1 mm dia wire to 5.3 mm lengths to get the correct solder volume. Spheroidize the rods by dropping them in a column of high temperature oil with the top section above the melting point and the remainder below. You may need a film of flux on the top of the oil to prevent oxides from distorting the shape. The ball will form as the solder melts and then cools in free fall through the viscous liquid.
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