An etching step is performed on an LEDsubstrate wafer to etch through the LED epitaxial layers entirely around each LED on the substrate wafer to form a gap between each LED on the wafer. With the present invention a compulsory moistening of the blocks with suitably heated water is performed, after which these are made ready for use almost immediately, so that an actual conditioning no longer is necessary or can be reduced considerably. The magnet is disposed between contact pads for first and second circuits, and an electromagnetic source is coupled to the assemblies.