Semi-transparent mirror in component placement

The driving force behind the ever-increasing density of components on printed circuit boards (PCBs) is the miniaturisation of handheld equipment for component placement. PCB technology went from Thru Hole to Surface Mount and currently there is a growing presence of components that have the contacts on their blind side, as is the case with Ball Grid Arrays (BGAs). This article describes the design and use of a semi-transparent mirror in component placement for superimposing the image of the contact side of a component with the image of the corresponding tracks on the PCB.