APPARATUS FOR SOLDERING PRINTED CIRCUIT BOARDS

A vapor phase soldering apparatus for soldering printed circuit boards (16) having electric components (18) mounted thereon by solder preforms (19), wherein the articles to be soldered are heated with hot vapors of a heat transfer liquid (14) so that the solder provided between the printed circuit boards (16) and the electric components (18) is melted to effect the soldering. The apparatus includes a vessel (11) for containing the heat transfer liquid (14), a heater (12) for vaporizing the heat transfer liquid (14), inlet (23a) and outlet (23b) port means provided in the vessel (11) to allow the introduction and removal of the articles to be soldered, conveying means (17a) to convey the articles into and out of the soldering zone of the vessel (11) via the inlet and outlet port means (23a,23b), cooling means provided in the closure means (21a,21b) for condensing vapors of the heat transfer liquid (14), and control means (24) to control the volume of the vapors of the heat transfer liquid which ascend into the soldering zone.