Contactless Chip Tilt Measurement Method and Apparatus
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
The present article describes a contactless method for measuring the tilt of semiconductor chips mounted on a module. As illustrated in Fig. 1, a strong, even, light source, such as provided by a slide projector, is used to illuminate a module containing chips so as to project a reflected image from each chip onto a flat screen. The images may be displaced from a regular array by deviations in regularity of the solder pad vias onto which the chips are mounted. More importantly, however, any tilting of a chip caused by mismounting or damage to the solder pads is detected by aberrations in the image.