09

Outgassing Outgassing
is still a common problem associated with wave and hand soldering. Basically when a board is soldered any moisture in the board close to the hole is heated and turned to vapour. If there is either thin plating or voids in the plating gassing can come through the plated hole wall. If solder is present in the hole this will produce voids in the solder as it solidifies. The voids may appear as small holes in the surface of the joint, as shown in the example, or much larger cavities. Having the correct copper plating thickness in the through holes is the key. A minimum of 25um of copper should be present on the surface of the hole walls. A test procedure is available from EPS on our Web Site www.bobwillis.co.uk or alternatively a test procedure is available with examples of good and bad holes under test on video tape.