Analysis of PCB Variations for Impedance Control

Abstract: Ericsson is a world-leading provider of telecommunications equipment and related services to mobile and fixed network operators globally. Over 1,000 networks in more than 175 countries utilize Ericsson’s network equipment and 40 percent of all mobile calls are made through their systems. Ericsson is one of the few companies worldwide that can offer end-to-end solutions for all major mobile communication standards. Tons of PCB is needed in this industry. With more complex hardware designs the need for efficient ways of controlling the impedance in our boards is increasing. Higher data rates and frequencies require better control of the PCB and understanding of the variations in the manufacturing of the PCB. The thesis goal is to study and research on how we can use cheaper PCB materials and handle the variations of these cheap PCB materials. This can be achieved with sorting out the spreading when it comes to conductor width & thickness, dielectric constant & thickness. One more area to explore is the variations of the dielectric constant due to glass cloth. How could statistical methods be used when looking at the variations of the material properties? Mathematica and Advanced Design System (ADS) were used to perform statistical analysis. The result of the thesis can help PCB designer to choose materials more wisely and provide advice to suppliers if they can achieve high quality products.