How my electronics should be oriented: A thermal point of view study to understand the impact of orientation on internal air temperature

Abstract

Modern day electronics work in varied thermal conditions. The increase in demand of electronics, has led to miniaturization, use of plastic housing and more applications from the existing electronics in the market. The model for analysis consists of multi-layered Cu-FR4 Printed Circuit Board (PCB) with a power dissipation of 10 W (Volumetric distribution in PCB). The PCB is further enclosed in a housing. Representative internal air temperatures are estimated for evaluating thermal performance of housing in different studies. The dimensions of housings used for these studies are similar to that of typical automotive electronics. In the first study, an evaluation is carried out to understand the effect of orientation of metallic electronic housings w.r.t. incident airflow. Metallic housings are usually provided with heatsink and fins and the same are considered in our model. It is observed that the internal air temperature of the housing is minimum when the airflow is aligned in the direction of length of fins. It is also observed that an equally favorable orientation is when the airflow is directed on top of fins. Another study is done to evaluate the effect of orientation of metallic and plastic housings w.r.t. gravity in case of natural convection airflow. Unlike metallic housing, plastic housings are usually devoid of fins and heatsinks. For both metallic and plastic housings, it is observed that the internal air temperature is minimum when the plane of the housing is vertical. Moreover, for metallic housings best orientation is when fins are aligned vertically. In addition, a study to evaluate the effect of orientation of plastic housing w.r.t. incoming solar radiation in case of natural convection airflow is done. It is observed that internal air temperature is minimum when the plane of the housing is vertical. All these observations are made from steady state thermal simulations carried out using FloTHERMTM. The ambient is considered to be similar to any electronics mounted in an automotive. In addition, all the three modes of heat transfer i.e. conduction, convection and radiation are considered. This study will help forming guidelines for any design engineer, who wishes to choose an optimum orientation of housing, taking into account thermal performance of electronics.