Analysis of platinum bond pads on polyimide soft substrate for wire bonding with Au wire using nano-indentation technique

The thermosonic gold wire bonding is a common technology in microelectronics industry for reliable bonding. The bondability of metallisation on soft material like polyimide (PI) is a matter of concern, especially when the bond pads are made of thin coating of platinum material. Nano-indentation technique is commonly used to measure surface properties of thin film coatings, such as Young's modulus and hardness within sub-micron scale. Four different samples were produced by sputtering different thickness of Pt on polyimide substrate to study the behaviour of thickness versus applied load of indentor. The nano-indentation data regarding "load versus displacement" and "hardness versus displacement" for all the four samples were collected and deformation behaviour and mechanical properties of thin film platinum material had been investigated. In this paper, the analysis of platinum pads has been carried out and it was observed that the samples with 300 nm platinum layer on polyimide were bonded well as compared to 100 nm thickness of platinum material.