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Wire Bond Pad Sub-Surface Structures for Increased Surface Area and Bond Strength

IP.com Disclosure Number: IPCOM000100718D
Publication Date: 2005-Mar-16
Document File: 3 page(s) / 25K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that increases the wire bond surface area by applying metal over a non-planar patterned wire bond pad surface. Benefits include a solution that is easy to implement and increases wire bond strength.

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Wire Bond Pad Sub-Surface Structures for Increased Surface Area and Bond Strength

Disclosed is a method that increases the wire bond surface area by applying metal over a non-planar patterned wire bond pad surface. Benefits include a solution that is easy to implement and increases wire bond strength.

Background

Currently, low wire bond strength is caused by the following:

§         Using small-diameter bonding wires

§         Using a bond pad that is less than 75um in the x and y directions

§         Using wire bonding temperatures that are less than 180°C

§         Using a bonding force that is less than 25g

This problem is currently solved by switching to specially formulated gold wire bond metal alloys for lower temperature wire bonding, or by using an aluminum wedge bonding method.  Currently, wire bond pads are designed to be flat (see Figure 1) for conventional bonding pads.  When a redistribution layer is used on top of the original bonding pads (see Figure 2), the bonding area is also kept flat.

The problem of bond pad peel-off is partially addressed through the use of specially formulated adhesion promoter chemicals and Argon plasma surface treatments to help the bond pad metal adhere better to the dielectric material that it rests upon. The problem is further solved by increasing the thickness of the bond pad metal, and the use of a titanium adhesion metal layer when aluminum bond pads are used.

General Description

The disclosed method increases the surface area of the bonding pad, while using smaller diameter wires; this has the same effect as using larger diameter wires.

One approach for locking the wire bond in place is shown in Figure 3; the well is created by building up the side walls using a non-conductive layer on either side of the original bond pads. This narrows the dimension of the bond pad in the x and y dimensions. The final metal is then deposited on top.

Anot...