Browse Prior Art Database

Thin Film Substrate for Wire Bonding

IP.com Disclosure Number: IPCOM000099942D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 76K

Publishing Venue

IBM

Related People

Gedney, RW: AUTHOR [+2]

Abstract

Disclosed is a process for applying nickel/gold pads to the thin film wiring on a ceramic substrate. This provides for the mounting of semiconductor devices with wire bond interconnections to the substrate.

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Thin Film Substrate for Wire Bonding

       Disclosed is a process for applying nickel/gold pads to
the thin film wiring on a ceramic substrate.  This provides for the
mounting of semiconductor devices with wire bond interconnections to
the substrate.

      A chip carrier consisting of a thin film wiring layer on a
(high) alumina ceramic substrate normally consists of a metal
sandwich of chrome-copper-chrome, where the bottom chrome provides
adhesion to the ceramic, the copper provides low resistance
interconnection, and the top chrome passivates and protects the
copper surface.  The usual process for solder ball flip-chip
interconnection is to first form the wiring pattern and then open a
pattern in the top chrome for soldering.  At this point in the
process, however, all lines are not interconnected, making additional
metal layers through electroplating impossible.

      The alternative process described here solves this problem.
The ceramic substrate 1 (Fig. 1) is metallized (Fig. 2) with a
blanket of metal 2 (chrome-copper-chrome), as described above.  Metal
deposited in the holes 3 is removed by applying a photoresist (not
shown) to the metallized surface; exposing the entire surface with a
collimated light source; developing; etching followed by stripping
the resist (Fig. 3).  A photoresist is applied and exposed in the
areas 4 where wire bond pads are desired by the particular circuit
pattern (Fig. 4).  The patterns 5 on the four sides of the sub...