This invention is related to hybrid circuit chips or silicon substrate circuit flip chips which are soldered to a support structure. Specifically, there is provided a heating means integral with the circuit chip to permit unsoldering a specific chip which is soldered to a support structure to permit soldering a chip to a support structure without adversely affecting a neighboring chip and/or printed electrical conductors on the support structure.
Hybrid circuits usually include a plurality of circuit chips having one or more electrical components. These circuit chips are usually provided with a plurality of bonding pads for soldering to corresponding bonding pads on a glass or ceramic substrate which provide a support structure for the circuit chips. The hybrid circuit substrate or support structure also has a plurality of electrical conductors printed thereon using, typically, thin film or thick film techniques. The electrical conductors provide electrical interconnections between the circuit chips which have been soldered to the support structure.
Many circuit chips are silicon monolithic integrated circuits. This variety of circuit chips has bonding pads on one surface thereof and includes "solder bumps" on the pads. This type of chip is sometimes referred to as a flip chip. The solder bumps are part of the soldering process for soldering the circuit chip to the hybrid circuit support structure as is well known.
Since there is a very high cost in a completely assembled hybrid circuit, it is desirable to be able to repair an assembled hybrid circuit by removing a defective circuit chip and replacing it with an operative unit rather than scrapping the whole hybrid circuit. Prior art techniques for removing circuit chips from hybrid circuits include using a hand soldering iron, and using a rework fixture employing a hydrogen flame as a heating mechanism. These techniques, in many situations, result in irreparable damage to the electrical conductor patterns on the hybrid circuits as well as to adjacent good circuit chips and components. Another technique for removing hybrid circuits is shown in U.S. Pat. No. 3,904,100 in which a fixture is used in repairing hybrid circuits. The fixture includes a mechanism for heating a specific circuit chip to melt the soldering material between the circuit chip and the hybrid circuit substrate and permit removal of the circuit chip without damaging either adjacent circuit components or the conductor pattern on the hybrid circuit substrate. The latter technique for removing hybrid circuits has a disadvantage insofar as being a cumbersome apparatus to operate and requires an undue expense for providing the intended function.