Up to now, while automobile electric packages have demanded the high density for small and light products,electric leaks, which have occurred due to condensation, have been a major problem. To prevent any electric leaks,a conformal coating on the electric parts (ex. ECU : Electronic Control Unit ) has been needed, but in general thedesign rules of the conformal coating (ex. Application area) is vague. Therefore, DENSO demands to clarify thedesign rules of conformal coating electric package for higher reliability.To meet the demand, DENSO has developed a condensation simulation method using CAE that can show theoccurrence condition of condensation fast and accurately. In the result, DENSO has been able to get the designrules where to need the conformal coating in the electric package for automobiles.Key words : Condensation simulation, Automobile electric package, Conformal coating, Electric leak