Scanning Electron Inspection System for Solder Pads
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
Some C-4 solder pads are being produced with insufficient solder so chips must be inspected to cull these faults. Current and proposed inspection practice, which utilizes optical images of the chip, is vexed by extraneous surface effects which scatter or reflect light and confuse the analysis of the pad area. Here, the atomic spectrum of the pad elements is excited and only this light is allowed to affect the analysis. In Fig. 1, a chip is shown with solder pads 9. Due to obstructions in lithographic masks or to inadvertent removal of deposited solder with mask or to other causes, some of the C-4 solder pads 9 on chips 10 are being fabricated with insufficient solder. Human inspection with an optical microscope is regarded as inadequate and wasteful.