In an electronic product there always are some weak points (flaws) such as insufficient solder joints or bonded joints in a semiconductor, which can be the cause of an equipment failure during early field operation. Before delivery to customer these flaws can be transformed into permanent faults, the faults located and the electronic unit repaired and delivered as a strong unit. This is done by a method called Reliability Stress Screening, RSS. By use of this method the reliability of an electronic equipment in the initial time of field operation is improved. As the cause of the weak point is disclosed and corrective action is taken, this also results in reliability growth of the product.