Mounting technology also plays a role in the functionality of a phototransistor.
• Surface mount technology (SMT) adds components to a printed circuit board (PCB) by soldering component leads or terminals to the top surface of the board. Typically, the PCB pad is coated with a paste-like formulation of solder and flux. Elevated temperatures, usually from an infrared oven, melt the paste and solder the component leads to the PCB pads.
• Through hole technology (THT), another commonly used mounting style, mounts components by inserting component leads through holes in the board and then soldering the leads in place on the opposite side of the board. In terms of features, some phototransistors include a cutoff filter that blocks visible light. Others have an anti-reflective coating to improve light detection. Devices with a rounded dome lens instead of a flat lens are also available.