Selective soldering is the process by which through-hole components are soldered on to a PCB by use of an automated through-hole placement machine. Selective soldering is generally used when there is a high quantity of boards. For prototype projects, it is more time-efficient to manually solder each individual board. Here at Bittele, we use the ERSA Versaflow 375 Global Edition.
The ERSA Versaflow has two methods it can use to solder through-hole parts. The first method is by creating a fountain of solder, a ‘wave’, and the solder nail goes over several through-hole pins at one go. This method is used mostly for connectors which have pins in very close proximity to each other and the solder fountain may not have enough clearance to go to each pin directly. The other method is to solder each through-hole pin individually, this is the most commonly used option as most boards often have their through-hole parts dispersed around the board. Both of these methods may also be used together.
How it works
The first step would be to program the ERSA Versaflow 355 by extracting the centroid files. The centroid files for the through-hole components are extracted from the Gerber files.
The boards are placed on the conveyer belt and then fed into the machine. Prior to soldering, they are covered with flux, mainly to remove the layer of oxidized metal on which the solder will be applied. Secondly, to seal out any remaining air. Preventing further oxidization.
Next, the boards are preheated to about 100 degrees C to activate the flux.
The final step is where the solder fountain will solder each through-hole part on the board.