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Polyimide Preform for Polyimide Film Chip Carrier

IP.com Disclosure Number: IPCOM000041185D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Schuessler, PW: AUTHOR

Abstract

Polyimide film chip carriers (PFCC's) are subject to drooping during thermal cycling, thereby causing electrical shorting between the circuit lines of the chip carrier and the edge of the chip connected thereto. Electrical shorting is eliminated by placing a polyimide preform on the chip carrier to insulate the circuit lines thereon from the edge of the chip.

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Polyimide Preform for Polyimide Film Chip Carrier

Polyimide film chip carriers (PFCC's) are subject to drooping during thermal cycling, thereby causing electrical shorting between the circuit lines of the chip carrier and the edge of the chip connected thereto. Electrical shorting is eliminated by placing a polyimide preform on the chip carrier to insulate the circuit lines thereon from the edge of the chip.

The use of a polyimide preform will be described with reference to Fig. 1. Chip 10 is electrically connected to multilayer ceramic (MLC) substrate 30 via chip carrier 20. The electrical pads of the three components are connected by a known joining technique, such as C-4 technology. Electrical pads 11 of chip 10 are connected to inner electrical pads 21 of chip carrier 20, inner electrical pads 21 are connected to outer electrical pads 23 via circuit lines 22, and outer electrical pads 23 are connected to electrical pads 31 of MLC substrate 30. Electrical pads 21 and 23 and circuit lines 22 are all on the underside of chip carrier 20 as shown in Fig. 1. Polyimide preform 40 is applied to chip carrier 20 before the connection of the electrical pads. The length of the internal opening in preform 40 must be smaller than the length of chip edge 12, but larger enough not to interfere with the connection between electrical pads 11 and 23. Preform 40 thus insulates circuit lines 22 from chip edge 12 to prevent shorting during subsequent drooping of chip carrier 20 in...