This standard covers the design of printed circuit boards (PCBs) used in the thermal characterization of ball grid array (BGA) and land grid array (LGA) packages. It is intended to be used in conjunction with the JESD51 series of standards that cover the test methods and test environments. JESD51-9 was developed to give a figure-of-merit of thermal performance that allows for accurate comparisons of packages from different suppliers. It can be used to give a first order approximation of system performance and, in conjunction with the other JESD51 PCB standards, allows for comparisons of the various package families.