The effect of printed circuit board on cooling and EMC of switched mode power supply

EMC and thermal properties of seven FR4, FLEX and IMS based printed circuit boards (PCB) were studied experimentally with a boost type switched mode power supply. Thermal performance of PCBs was measured using a DPACK transistor as test load with boards mounted into metal enclosure. Conducted emissions (150 kHz-30 MHz) were divided into differential and common mode components. For EMI measurements from 30 MHz to 1 GHz an absorbing clamp was used. Thermal resistance of test cases varied from 58.7/spl deg/K/W of 1-layer FR4 to 7.9/spl deg/K/W of 2-layer INIS. The total common mode noise energy of worst ease (1-layer FLEX) was 58.5 times higher than with the best (2-layer IMS). The prices of PCBs in the study varied from 0.38$ (layer FR4) to 2.15$ (2-layer IMS).