We describe a stereoscopic measurement method to study the coplanarity of solder balls on a ball grid array (BGA) packaging. The optical system consists of two long-focal-length lenses and a two- channel digital image grabber. The proposed technique uses image recognition and digital correlation, which simplify the calculation procedure. The computation requires only a few seconds to calculate the height of a few hundred balls. The technique is suitable for in situ measurement in BGA manufacturing.