Hello - We are mounting light sensors on a circuit board and these sensors come in a variety of packages (BGA's, QFN's etc) I was trying to determine if there is a standard or spec that addresses the deviation from a "perfect" 90 degree angle of light addressing the sensor's active surface.  Ideally the sensor would be mounted such that direct light addressing the sensor would be at a 90 degree angle to the pcb and subsequently to the sensor itself.  Anyone have any experience or advice?  Thanks in advance.