Technology Developments for Flexible Circuit Multi-Chip Modules Polyimide flexible circuits have been developed over recent years to accommodate direct attach of unpackaged silicon chips specifically for high performance disk drive applications. This technology now offers advantages and opportunities for MCMs in many other industry sectors. "Chip-on-flex" (CoF) technology was developed in order to position amplifier chips in close proximity to the magnetic heads on the moving actuator arm inside hard disk drives. Chips are attached using ultrasonic aluminium wedge bonding between the silicon and the etched copper tracks on the polyimide flexible circuit. As the number of disks and heads per drive has increased it has become necessary to incorporate multiple amplifier chips onto the circuit essentially producing an MCM with a flexible connection.
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