System for chip joining by short wavelength radiation

Abstract

Defective chips are removed from a substrate package. The package is cleaned. Replacement chips with solder bearing elements are replaced in the position(s) of the defective chip(s). Silicon chips are less damaged by heating with light wavelengths substantially shorter than infrared radiation, when the radiation is directed upon the upper chip surface and the lower chip surface carries circuitry and solder balls. Radiation is absorbed by the upper chip surface and converted there directly to heat, protecting the circuitry below. An argon-ion laser beam confined to a given chip is directed upon the upper surface of the chip to be soldered in place. A thin laser beam can be scanned under computer control across a chip to heat the areas of a chip above solder balls. Automatic temperature control of the chip can be provided by a heat detector or chip condition detector and a program controller in a feedback loop controlling laser power.