Modelling of thermocouple geometry variations for improved heat transfer monitoring in smart electronic manufacturing environment

Abstract

In this paper, the effect of different thermocouple constructions on the hot spot temperature are investigated with a modelling approach to achieve more precise soldering profile acquisition and failure analysis at different reflow soldering heat transfer methods. The paper focuses on convection-based reflow and condensation based vapour phase soldering processes and related heat transfer coefficients. Different thermocouple constructions were investigated. The parameters include the ASTM-type (K, T, J), the length of uninsulated wire length, the insulation material (PFA, PVC, PTFE, woven glass-fibre), the insulation thickness and the diameter of the hot-spot. The physical dimensions were obtained with optical microscopy for validation. Finite element analysis was performed. After validation, the results show that most parameter and geometry changes – most significantly, the uninsulated wire end – can result in non-negligible timely differences in 100 ms range between different sensors, pointing to the requirement of sorting and pairing in a symmetric measurement environment. The results can be applied in a modern manufacturing environment and in future process modelling and evaluation tasks.