Preheating an assembly prior to selective soldering is important for many assemblies to ensure good soldering results. Preheating must be strictly controlled so that each assembly reaches the specified preheat temperature at a controlled and linear ramp rate. Vitronics Soltec’s mySelective 6748 offers a closed-loop preheater management feature that actively and precisely controls board preheating dwell time and temperature to ensure board-to-board repeatability and optimized process control. It keeps cycle time to the minimum required to reach the correct temperature, thus minimizing overall processing/heating time for the board and minimizing the potential for oxidation and other negative effects of extended thermal processing.
The system uses a non-contact temperature measurement method, an infrared temperature sensor, to gather real-time data from the board while it is being heated, for constant feedback. The system controls the power of the heating lamps based on sensor readings so that each board sees a controlled, linear temperature increase (profile) to the user-specific setpoint value. The user can also program the system to sense temperature at a specific place on the board. In operation, boards that are cycled into the preheater station(s) are heated to setpoint before they are automatically indexed to the next preheat station or picked up by the robot arm to be soldered in the soldering station.
The system controls both the power to the heater lamps as well as the dwell time of the board in the preheater. Each and every product reaches the same required end temperature before the next action is begun. Most importantly, the system ensures a straight or linear ramp profile for maximum process control and minimized thermal stress.
EPP Europe 529
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