Stand-Off Stitch Auxiliary Wires for Improved Wire Bond Reliability

Whether it is for a critical biomedical device, the latest spacecraft or military weapon system or just your new big screen TV at home, the security and reliability of the wire bonding interconnect is of up-most importance.

In pursuit to improve wire bond reliability, our engineers have adjusted wire dopants to enhance crystal structure in the Heat Affected Zone, allowing for various loop modes on the wire. These adjusted wire dopants also reduce the likelihood of the formation of intermetallic contaminants. This improved wire bond reliability solution has:

• Increased pull strength of the stich bond
• Improved failure mode from destructive pull tests – more mid-span and neck breaks than tail breaks, even with poor materials
• Enhanced bond strength after high temperature burn in

The integrity of a wire bond interconnect is significantly improved through the proper use of Auxiliary Wires—Security Wires, Security Bumps, or Stand-Off Stitch (a.k.a. Stitch on Bump). Stand-Off Stitch (SOS) has many more applications and side benefits that could be incorporated into a circuit design for better wire strength properties, fewer interconnects (die-to-die bonding or chain bonding) and lower loops.

Goodrich, a renowned global supplier of systems and services to the aerospace and defense industries, has achieved a considerable increase in their wire bonding quality with Palomar Technologies’ Stand-Off-Stich bonding process:

1. Higher destructive pull test values after 125C burn
2. Increase in the percent of failures as Code 2 (break above the ball) and Code3 (mid-span break in the wire) in destructive pull test—this shows that the failure mode during destructive pull test is in the bulk properties of the wire and not the bond interface
3. Improvement in wire bond reliability when wire bonding gold bonds on aluminum pads