Universal Speeds Up Flip-Chip-on-Flexible Assembly
Universal Instruments Corp. has designed an advanced assembly line that can assemble over 2000 flip chips per hour on flexible circuits.
The substrate is a thin flexible circuit that is normally processed in a carrier with eight to 12 circuits. Each comprises a 3 to 5 mm sq. pre-amplifier chip, five to 10 discretes and a connector.
An optimized line consists of a screen printer to apply solder paste, a chipshooter to pick-and-place the chip capacitors and the connector, a flip-chip placement machine with integrated dip fluxing and a reflow oven. For applications with high capacitor counts, two chipshooters would be required.
Universal’s chip placement platform configurations incorporate the company’s Variable Reluctance Motor (VRM) linear motors, featuring dual drives and one-micron linear encoders. Said to provide high accuracy and high speed, and enables the machines to be used in clean room environments. VRM technology is also at the heart of the 30-spindle rotary Lightning head – a chip placement solution that is smaller than mechanical turret heads typically deployed to place small discrete components. In addition, a four-spindle Pressure Enhanced (PE) head is used to place challenging components that demand higher accuracy. The PE head is used in conjunction with the Magellan camera – a high resolution digital Upward Looking Camera (ULC).
For the equipment designers, a major technical barrier was accurately imaging the component. The development project identified a need for a lighting module that integrates both blue and red LEDs to handle the wide spectrum of materials, such as polyimide, copper, etc. The team also redesigned the dip fluxing unit to be able to gang dip several components concurrently by adopting a linear versus a rotary mechanism..
The optimal tact time for the line is 20 to 25 sec. A twin-beam GSM Genesis platform equipped with two Lightning heads handles the discretes and the connectors. A second platform machine featuring a linear motor positioning system and a four spindle head combined with the Magellan ULC places all the flip chips to an accuracy of +/-9 microns at +/-3 sigma. Both machines are certified UL, CE, SEMI S2 and SEMI S8.
Universal Instruments Corp., www.uic.com
