Browse Prior Art Database

Alternative to Interposer for Small Chips in Pfp Package

IP.com Disclosure Number: IPCOM000120501D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 4 page(s) / 95K

Publishing Venue

IBM

Related People

Lepape, B: AUTHOR [+3]

Abstract

According to: 1. risks of shorts between wires when wires become longer than 2.5 mm (wire bonding technique inherent limitation), 2. lead frame etching process limitation to etching width equal to raw material thickness, 3. necessary 100-micron finger width to place a wire with present wire bonding technique, the present state of the art lead frame process shows its limits (notion of maximum number of fingers at minimum pitch versus available space).

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Alternative to Interposer for Small Chips in Pfp Package

      According to:
      1. risks of shorts between wires when wires become longer than
2.5 mm (wire bonding technique inherent limitation),
   2. lead frame etching process limitation to etching width equal to
raw material thickness,
   3. necessary 100-micron finger width to place a wire with present
wire bonding technique, the present state of the art lead frame
process shows its limits (notion of maximum number of fingers at
minimum pitch versus available space).

      Two solutions to overcome the present limitations to increase
the necessary number of fingers in a given space versus technical
constraints described above are proposed.
Solution 1:  Staggered fingers (Figs. 1 and 2).

      By using this method, for a known demand like 208 leads PFP
(Plastic Flat Package) for 7.5 chip image, the inner finger row
allows containing the wire length within 2 mm. The outer finger row
lets the wire length be within 3 mm.

      By having a very good wire loop control of the 2 mm wire long
row, it is expected with a not so wall wire loop control for the 3
mm wire long row, to remain within the wire bonding specifications.
Solution 2:  Thin finger tip (Figs. 3 and 4).

      This solution aims to obviate the problem stated in point 2
above. According to the principle of this solution, using the basic
etching rules, it is possible to decrease the pitch of finger tips
and so to increase the n...