Virtual Validation of Automotive Electronic Products for Climatic Test Conditions

In modern automobiles a complex network of electronic sensors and controls is being integrated for increased comfort, convenience, and safety. All of these needs to be designed for the stringent environmental condition requirements. Environmental tests used for validation of product primarily consists of combination of Vibration load, Temperature and Humidity. Failures induced by vibration Load and temperature cycling are fairly well understood and often simulation can help design team to understand weakness in design and evaluate design options to mitigate it. However, Humidity and temperature (cyclic or constant) are critical as well referred as Climatic tests. The purpose of climatic tests are to assess the ability of a product to operate reliably under condensing conditions. Unlike other environmental test where there are visual clues of something broken, these test could lead to failure without any visual clues. Failures are intermittent in nature as they are driven (among other things) by presence of water on Printed Circuit Board (PCB). With moisture or water present on board they might malfunction but fault will disappear with evaporation of water. Examples of these failures are presence of dendrites due to Electrochemical migration (ECM), aqueous corrosion or sudden malfunction of intermittent nature. These are primarily resolved after actual validation test and almost no simulation is performed for up-front prediction of possible design issues. Hence there is a fundamental need to understand simulation of climatic test and predicting the regions of condensation on PCB. The objective of this paper is to demonstrate simulation methodology to predict the moisture condensation on PCB during combined temperature humidity test. The scope of the study focuses on qualitative correlation of the simulation predicted condensation location and experimentally observed results to build confidence in the simulation approach. The design sensitivity study also has been conducted to investigate the variation in response due to change in environmental and design conditions like device power numbers, device switch on and off frequency, Thermal cycling ramp rate and ambient humidity.