The Boc Group, Inc.

Colin John Precious

Neeraj Saxena

Paul Francis Stratton

Raymund Thomas

A furnace, for instance a reflow soldering oven, in which oxygen concentration is either directly or inferentially sensed within central processing and either one or both of the inlet and outlet sections of the furnace. Signals generated by these sensors are processed in a PID controller to generate a control signal to control the flow rate of inerting gas into the central processing section, thereby to at least inhibit ingress of air into the central processing section. The PID controller is programmed such that its integral error term is set equal to a time average of the oxygen concentrations of the central processing section less an oxygen concentration set point desired for the central processing section. The proportional and differential error terms are set equal to a time average of the concentrations of the central processing section and one or both of the inlet and outlet sections of the furnace less the oxygen concentration set point.

Furnace having regulated flow rate of inerting gas

A soldering apparatus includes a conveyor adapted to carry assembled circuit boards through a soldering chamber. A wave of solder is created in the chamber. The chamber has a curtain at its entrance and a curtain at its exit. Gas distributors are located within the chamber and are able to introduce nitrogen into the chamber in order to create a non-oxidizing atmosphere in the vicinity of the wave. In operation, the wave of solder wets connecting points between the components and the board to form permanent joints on solidification of the solder. The bottom edge of the curtain is of a shape complementary to the front elevation of the assembled circuit boards to be soldered and is arranged such that the circuit boards just pass thereunder without making contact with it.

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Rotherham, United Kingdom

Colin John Precious