FEXT Reduction Using Mushroom Structures Thickened Soldermask for DDR5 PCBs

Far-end crosstalk (FEXT) between adjacent signal lines is one of the most critical factors affecting signal integrity (SI) in double data rate 5 (DDR5) printed circuit boards (PCBs). In this paper, a new method for FEXT reduction, based on mushroom structures thickened soldermask (MSTS) for coupled signal lines, is proposed and investigated. From the simulated S-parameters results, FEXT of this proposed method can be suppressed among a very wide frequency range. Additionally, the FEXT is decreased more than 25dB around the main frequency of DDR5, compared with the traditional signal routing. Finally, both frequency and time domains results show that our proposed method could significantly improve the performance of SI and dramatically reduce FEXT for DDR5 system designs.