A Discussion on the Methods of Thermal Cycling and Power Cycling for Reliability Prediction of Solder Joints of Electronic Components

The increasing use of embedded electronics in aerospace and automotive vehicles increases the designers' concern regarding the reliability of the components as well as the reliability of their interconnections. The discussion about the most appropriate method for assessing the reliability of solder joints for a given application is an ever-present theme in the literature. Several methods of prediction have been developed for assessing the reliability of solder joints. The standard method established by the industries for assessing reliability of solder joints is the thermal cycling. However, when the thermal distributions in real applications are studied, particularly in some electronic components used in on-board electronics of space systems, the thermal cycling does not represent what actually happens in practice in the packaging. The aim of this article is to discuss the methods of thermal cycling; and power cycling for reliability prediction of solder joints of electronic components. With the power cycling you can: 1) simulate more closely the actual conditions; 2) accelerate a cycle of application when applying energy to the component, increasing junction temperature; and decreasing the junction temperature when removing energy from the component. With the thermal cycling, the solder joints and the printed circuit board are almost at the same temperature in an isothermal situation at any moment and thermal gradients within the packaging are often negligible. Fatigue data of solder joints from thermal cycling and power cycling are obtained through networks of monitoring components of type "daisy-chain" with the aid of high-speed event detectors. Both profiles are obtained and compared in the Weibull graphs. Failure data results obtained from the literature have shown that the thermal cycling in general is conservative compared with the power cycling. In addition, according to the literature, power cycling simulates better the gradients of temperature found in the packages of components in actual applications. On components of type PBGA, solder joint characteristic life was 45% longer in power cycling.