I recently visited a factory in China and saw people soldering headphone pins with a soldering device that gave sparks, melting the tin. The soldering iron was hooked up to a device and the pin was also connected with a tool to this device, which has a dimensions of a small coffee table. The input was 220v AC and output 5v DC. There was another meter that said 30. Could this have been the current? What device would be able to reproduce such a spark for soldering? A cheap welding machine?
Edit: Thanks to you all for helping me!
I do not have a picture of the device a saw. It was similar to this device (made for spot welding batteries) only the size of a small coffee table:
They use this to solder wires to jack plugs for headphones with high speeds and reduced energy costs (compared to heat soldering). The process is old but not documented in for example YouTube. However, you can all see it here.
The person in the video is doing it so fast that the tip runs hot. The tip I observed in the factory did not run hot continuously, or the settings (ampere) were lower, or the guy was slower. What I observed was more with a spark of about 5 mm.
I want to simulate this process at home, only one pulse, not multiple sparks like the video. I will therefore start with tinkering around with an old PC power supply 5V 20A or old car battery 12V 40A. Probably going to buy someone a coffee at the university to give me some help with this.