#23 CONTROLLING PRINTED CIRCUIT BOARD PREHEAT DURING WAVE SOLDERING

The IRt/c is an excellent solution to the problem of heater control for PC board preheat. IRt/c’s work particularly well in this process, since both the heating and measuring occur right at the surface, where the solder must flow. The IRt/c reading is unaffected by reflections from the heater, since the spectral response of the 6-14 micron IRt/c lens filters out any shorter wavelengths of the radiant heater energy.

The IRt/c may be mounted in between ceramic heaters, or in the shroud or reflector of the radiant heater, such that it can see in between the elements. Select the IRt/c model with the field-of-view required to see past the elements to the PC boards. Care should be taken in mounting the IRt/c in such a way as to keep its temperature below 200°F (93°C) and to keep the lens clean. The IRt/c.3x is the preferred model for this application because of its small physical size and built-in air purge. It can function in temperatures to 250°F (121°C) when the air purge system is used. For still narrower fields of view, the IRt/c.5 and IRt/c.10 with 5:1 and 10:1 FOV respectively are very popular.

Download this Tech Note as PDF