Investigation on Bonding Wire Short Caused by Vibration and Its Solution for High-Density Packaged ICs

A high-density packaged integrated circuit (IC) was found to be permanently abnormal due to its bonding wire short when the spacecraft equipment in which it was used was subjected to a mechanical shock. The IC is packaged in CPGA391 with an outline size of 47 $\text {mm} \times 47$ mm and has up to 492 internal bonding wires. Through the experiments, we found that the bonding wire short was caused by the collision between the two adjacent bonding wires when the IC was subjected to mechanical vibration. As the internal layout of the IC package cavity could not be further adjusted due to its functional requirements, a vacuum coating process was proposed for the bonding wire. The Parylene-N thin film was deposited on the surface of the bonding wire to form an insulating layer. It can improve the mechanical strength of the bonding wire and change the natural frequency of the bonding wire, which then makes the vibration amplitude of the bonding wire not too large and does not cause a collision of adjacent bonding wires. Some tests were carried out to verify the method, and the results show that it solves the problem of the bonding wire short under the condition of mechanical vibrations.