title: Three-dimensional inline inspection for substrate warpage and ball grid array coplanarity using stereo vision.
abstract: We present a method for full-field 3D measurement of substrate warpage and ball grid array coplanarity, which is suitable for inline back-end inspection and process monitoring. For evaluating the performance of the proposed system, the linearity between our system and a reference confocal microscope is studied by repeating measurements 35 times with a particular substrate sample (38  mm×28.5  mm). The point-to-point correlation coefficient with 1σ between two methods is 0.968±0.002, and the 2σ difference is 25.15±0.20  μm for warpage measurement. 1σ repeatability of the substrate warpage is 4.2 μm. For BGA coplanarity inspection the bump level correlation coefficient is 0.957±0.001 and the 2σ difference is 28.79±0.14  μm. 1σ repeatability of BGA coplanarity is 3.7 μm. Data acquisition takes about 0.2 s for full field measurements.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakazawa
authors.forename: Ayman
authors.initials: A
authors.lastname: Samara