Fast development of electronic technology leads to instant improvement in terms of computational speed, computational frequency and integrity of electronic products. Besides, with the volume of electronic products shrinking, volumetric power density is becoming increasingly high. In addition, the development orientation of thickness, lightness and miniature all make electronic components feature increasing calorific value of unit volume. With the upgrading of electronic products, their reliability is badly influenced as a result of fast increasing density of heat flow in PCBs. According to 10 degree principles, each time temperature rises by 10 Degrees Celsius, part of parameters of some components will decrease by a half. Based on a research, 55% of electronic devices are damaged because the temperature bypasses rated value of components. Therefore, reasonable component layout and PCB thermal dissipation has been the main elements engineers must consider.