Coplanarity study on ball grid array packaging

We describe a stereoscopic measurement method to study the coplanarity of s older balls on a ball grid array (BGA) packaging. The optical system consis ts of two long-focal-length lenses and a two-channel digital image grabber. The proposed technique uses image recognition and digital correlation, whi ch simplify the calculation procedure. The computation requires only a few seconds to calculate the height of a few hundred balls. The technique is su itable for in situ measurement in BGA manufacturing. (C) 2001 Society of Ph oto-Optical Instrumentation Engineers.