At the request of the Swedish company Saab-Scania Combitech, TWI's Microtechnology team completed a short time scale investigation of multi-chip modules (MCMs) in just six weeks. The investigation concerned reworking of silicon chips on silicon substrates in alumina packages.
Saab-Scania Combitech was interested in growing industry concern that the economic success of MCMs could be dictated by the capability to replace individual chips which are defective, damaged or misplaced. It would be much too expensive to discard other working chips, substrate and package.
TWI's work in this relatively unknown area involved selection of potential die attach materials, examination of rework techniques, cleaning/surface preparation, die removal/replacement, adhesive characterisation, cleaning/surface preparation, wire bonding, equipment assessment and recommendations for rework equipment.
The Microtechnology team was asked to conduct these trials to demonstrate rework on MCMs with silicon substrates. Also during the allocated period, TWI conducted a technical appraisal of current technology.
It was concluded that there is a potential solution for MCMs in the form of adhesive die attach materials which will make rework possible.
Saab is now benefiting from the information provided by this work and has since built flexible rework equipment for production use.
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