Abstract: A circuit board for surface mounting by solder flow an electronic component having narrow lead pitches, the board having a first solder leading land having a first side and located on the circuit board adjacent to a land for mounting an electronic component, and a second solder leading land located next to the first solder leading land and opposite the first side of the first solder leading land. A method for flow soldering a surface mounted electronic component on such a circuit board, wherein the second solder leading land is positioned at a rear end of the circuit board against a direction of a movement of the circuit board when the circuit board moves toward a solder flow.

Abstract: A circuit board comprising a first solder leading land 13a disposed next to a mounting land located rearmost in a direction the circuit board moving during flow soldering of an electronic component, and a second solder leading land 13b disposed behind the first solder leading land 13a against the direction. The present invention provides a circuit board which can effectively prevent solder bridges caused by excessive solder accumulated around leads and lands located in the rearmost position while the electronic component is flow soldered at narrow pitches as is represented by a case with QFPIC. The circuit board of the present invention is suitable for use of lead-free solder, thus contributes to an environment protection.

Abstract: In a temperature control system when can be operated as a heat pump, frost deposited onto an outdoor heat exchanger (evaporator) is detected by a change in temperature of the refrigerant which flows into an indoor heat exchanger (condenser), so that a sensor to detect the deposition of the frost need not be attached to the outdoor heat exchanger. The refrigerant temperature is measured at the inlet of the indoor heat exchanger, and the temperature control system is switched to defrosting operation on the basis of this temperature and various elapsed time periods if the actual heat capability of the incoming refrigerant is insufficient, detecting the temperature of the refrigerant on the inlet side of the indoor heat exchanger, namely, by detecting the temeprature at a single position.

Abstract: A trouble detection apparatus for an air conditioner detects overcurrents occurring within a predetermined time period t.sub.2 which is a shortest time period necessary for stabilization of the compressor operation. By counting a number of occurrences of the above-mentioned detections as criteria of actual trouble, the compressor is stopped when the number becomes two or more; thereby unnecessary interruption of operation of the air-conditioner due to electric noise or a simple overload is eliminated.