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Rigid adhesive underfill preform, as for a flip-chip device

  • US 6,399,178 B1
  • Filed: 06/22/1999
  • Issued: 06/04/2002
  • Est. Priority Date: 07/20/1998
  • Status: Expired due to Fees
First Claim
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1. A rigid adhesive underfill preform for adhesively attaching an electronic device to a substrate having a pattern of contact sites thereon corresponding to a pattern of contacts of the electronic device, and to include solder bumps, said rigid adhesive underfill preform comprising:

  • a layer of adhesive material having a pattern of holes therethrough corresponding to the pattern of contact sites of the substrate, said layer of adhesive material having a thickness substantially similar to a height of the solder bumps, and wherein said adhesive material is rigid when cured and has a flow index greater than about 1.2 at a temperature T and a pressure P, wherein the flow index is the ratio of the area covered by the adhesive material after curing at a temperature T and a pressure P to the area of the adhesive material before curing.

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