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Direct application of unpackaged integrated circuit to flexible printed circuit

  • US 5,261,593 A
  • Filed: 08/19/1992
  • Issued: 11/16/1993
  • Est. Priority Date: 08/19/1992
  • Status: Expired due to Term
First Claim
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1. A method for electrically connecting a plurality of flip chips, each flip chip having two or more solder bumps, to a flexible printed circuit substrate having a plurality of contact pads, the method comprising the steps of:

  • providing solder paste on a plurality of active contact pads on the flexible printed circuit substrate, each active pad having a corresponding solder bump on one of the plurality of flip chips, such that the solder paste on each active contact pad is of sufficient volume to facilitate an electrical connection between the active contact pad and the corresponding solder bump;

    placing the chips on the substrate to form an unsoldered chip-substrate assembly, such that the solder paste on each active contact pad is in registration with the corresponding solder bump; and

    heating the chip-substrate assembly as a whole with a heating means which operates by direct infrared radiation of the assembly or by transmission of heat to the assembly from a heated working fluid, such that the solder paste on each active contact pad reflows to form an electrical connection with the corresponding solder bump.

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