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Method to wirebond to small passivation openings

IP.com Disclosure Number: IPCOM000006382D
Publication Date: 2001-Dec-28
Document File: 4 page(s) / 60K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to wirebond to small passivation openings. Benefits include improved carrying capability.

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Method to wirebond to small passivation openings

Disclosed is a method to wirebond to small passivation openings. Benefits include improved carrying capability.

Background

              Fine-pitch bond pads and the trend to 0.13-µm and 0.10-µm silicon technology require smaller bond pad openings. Small pad openings require small ball diameters and precision wirebonders. For example, a 35/70-µm staggered pitch has a bond pad opening of 52 µm. The maximum wire diameter allowed for this opening by conventional wirebonding methods is 25 µm and a maximum wire length of 4500 µm. If a larger diameter wire is used, the bonding tool could damage the passivation layer near the bond pad edge.

              Stitch-on-ball wirebonding utilizes conventional gold wire bonders to create a double bonded pad. This technique is used in die-to-die bonding and bonding ceramic (highly loaded with glass) substrates with cleaner capillaries and a more reliable laminate substrate.

              Thermosonic gold ball bonders are the most widely available (greater than 80%).

              Gold wedge bonders with rotary heads are in use for high-end microprocessors but are approximately 25% lower in throughput compared to thermosonic bonders. Gold wedge bonders also have a limited installed base. 

Description

              The disclosed method uses a two-step wirebonding process to create a bonded ball bump on a bond pad and a second bond on top of the wirebond bump.

              When the stitch-on-ball technique is used (see Figure 1), 25-µm wire is used to create the first ball. Then, a reverse stitch bond is performed using 30-µm wire. The entire ball is on the pad within a 51-µm passivation opening...