Wirebonds for munitions applications: Effects of dynamic shock, vibration, and spin

The use of microelectronics in munitions applications has been growing with the development of advanced smart weapons. For applications such as guided projectiles that are fired from a rifled cannon, the microelectronics in the shell will experience extremely high acceleration forces, vibration forces, and rotational forces during the launch and flight phases of the projectile. This study evaluates how un-encapsulated wirebonds behave when subjected to these kinds of severe environmental conditions. Fine pitch wirebonds of varying length and height were bonded on a test substrate in a microcircuit package. The package was then subjected to forces up to 28,000 G level (peak) along an axis that would either tend to push the wires down or to one side. Vibrational and rotational forces were also applied to the package. Following high-G testing, microscopic visual inspection and X-ray imaging was conducted to detect any wire damage or deformation. Destructive wire bond pull test was utilized to reveal any wire or interface weakening that occurred due to high-G forces. As expected, most long length wires were severely damaged at the higher-G level exposures and the shorter wires were less deformed. When properly oriented, even long length wires can withstand high-G levels. Vibration testing appears to weaken some wirebonds.