We continue our discussion of solder reflow methods.
As the name suggests, quartz plate preheaters have thick quartz plates in which the heating elements are embedded via pockets or slots. The heating and cooling rates are very fast compared to other preheaters – up to 93°C per minute. Because these elements get so hot so quickly, they do not require a secondary cleaning step. Any flux that drips down onto the plate will burn off. Like Hot Plate preheaters, the quartz plate can be arranged in sections parallel to the conveyor so that they can accommodate a variety of board designs.
The fast heating and cooling rates require a sophisticated control system which makes it more expensive than the alternatives. A word of caution – if this plate is left unattended it can overheat resulting in irreparable damage to the preheater. The quartz plate is also sensitive to abuse, such as a PWB falling onto the surface, or careless handling. More complex (multi-layer, high thermal mass) assemblies need adequate heating, which in other systems would require a very long preheat. It is unlikely that such a system is going to be built into a wave solder machine.
My next post will be covering Quartz Tube Preheaters.