A Solder Joint Crack - Characteristic Impedance Model Based on Transmission Line Theory

A solder joint crack - characteristic impedance model has been established in this paper. Under high frequency operational condition, signal integrity is important to the reliability of electronic products. Solder joint crack will change the characteristic impedance of transmission channel, and then will affect the signal integrity. So establishing the model of solder joint crack and characteristic impedance could connect solder joint crack with signal distortion together. It is meaningful to determining the failure threshold of the solder joint, so as to achieve the purpose of health monitoring and preventive maintenance. In this paper, the transmission line theory and reflection parameter have been analyzed. And then the physical model of damaged solder joint has been simplified. On these bases, the transmission line electrical model of the solder joint has been established. After that, the characteristic impedance of the damaged solder joint is deduced and the model of solder joint crack - characteristic impedance is obtained. In this process, both skin effect and parasitic effect have been considered. At last, the application process of this model is given. Moreover, this model is verified by experimental data and the result shows that the model is effective and the mean error is fewer.