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September 2023


Destructive Wirebond Testing: Advancing Development and Production Processes


By William Boyce, Engineering Manager, SMART Microsystems


assembling semiconductor packages. Astoundingly, wirebonding forms over 15 trillion interconnects annually. However, this interconnect method has


W


long posed challenges for process and manu- facturing engineers. The development process involves extensive effort, including destructive pull and shear testing, along with multifactorial design of experiments. Once the process is ready for manufacturing, the responsibility falls on the manu- facturing engineering teams to main- tain process integrity within specified parameters, which often necessitates further destructive testing.


Destructive Testing Ironically, destructive testing


only applies to a fraction of the bonds tested, as only the untested bonds are shipped to customers. This raises a question: How does wire bonding con- tinue to be a robust process, enabling the creation of low cost and dependable elec- trical interconnects for microelectronic com- ponents and mechanical package assemblies?


Wirebond pull test configuration.


size, materials, and loop geometry, the focus shifts to creating a strong and high quality weld between the wire and the base metal,


irebonding stands out as the most cost-effective and flexible intercon- nect technology, widely utilized in


One possible answer lies in the imple-


mentation of a rigorous statistical process control method. Wire bonding is a process that involves the joining of two metals through the application of force and vibra- tion. It requires meticulous engineering and development efforts. Once the design phase is complete, including the selection of wire


known as the bond foot. Destructive shear testing emerges as the


most effective means to determine the strength and proper formation of the weld joint. This testing method involves using a blade to completely shear through the wire bond foot, measuring the force required to break the welded joint. Careful examination of the failure


Bond Heel


mode and the remnants left behind after shearing is conducted. By analyz- ing the maximum shear value obtained, one can assess the overall strength and establish objective data points for fur- ther analysis and statistical process methods. Evaluating the remnants pro- vides insights into potential weakness- es in the weld and suggests ways to enhance the wire bond weld. In the process of developing wire


bonding, destructive shear testing remains an invaluable tool. After achieving an optimized wire bond weld within the designated process window through shear testing, the focus shifts to optimizing the wire loop formation. This optimization is typically carried


out through destructive wire bond pull test- ing. The bonding wire comes with a certifica-


Continued on next page


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