Abstract: The present work focuses on the thermal contact resistance (TCR) at the interface between the cooling board and the chassis rail in the enclosed rugged computer (ERC). Two types of connecting structures (3J and 5J structures) used in the ERC are studied using the finite element method (FEM) analysis software. Firstly， the contact pressure distribution and TCR distribution at the interface between the cooling board and the chassis rail are both studied. It is found that the TCR in 5J structure is much smaller than that in 3J structure. Secondly， the influences of bolt torque and surface roughness on the TCR of 5J structure are studied. The results show that TCR decreases with increasing bolt torque or decreasing surface roughness. However， a high bolt torque would result in a high contact pressure what may lower the service life of electronic devices. Further analysis shows that low stiffness of the chassis rail results in an inhomogeneous contact that leads to an inhomogeneous TCR distribution and high average TCR. Based on these findings， an optimization on the chassis rail is carried out to reduce both the average TCR and the contact pressure successfully. Moreover， the results show that the decrease in average TCR induced by the above optimization can be enhanced by increasing bolt torque or decreasing surface roughness.

Key words: enclosed rugged computer, thermal contact resistance, finite element, optimization