AMD provides the diameter of a land pad on the package side. This information is required prior to the start of the board layout so the board pads can be designed to match the component-side land geometry. The typical values of these land pads are described in This Figure and summarized in Table: BGA Package Design Rules . PCB pad size is based on the BGA ball size. Typical requirements for the PCB pad size are 80-120% of ball size however, given a large package size and to prevent solder bridging, a pad size closer to 80% of the ball size is recommended. For AMD BGA packages, non-solder mask defined (NSMD) pads on the board are suggested to allow a clearance between the land metal (diameter L) and the solder mask opening (diameter M) as shown in This Figure .
An example of an NSMD PCB pad solder joint is shown in This Figure . The space between the NSMD pad and the solder mask, as well as the actual signal trace widths, depends on the capability of the PCB vendor. The cost of the PCB is higher when the line width and spaces are smaller.
RECOMMENDED: AMD recommends not mixing PCB pad isolated via-in-pad plated over (VIPPO) and non-VIPPO design styles because they can cause hot tear defects that are related to localized Z-direction thermal expansion coefficient mismatch between VIPPO and non-VIPPO vias. A VIPPO via expands less than a non-VIPPO via.
RECOMMENDED: For packages that include land-side capacitors (LSCs), such as the FSVA3824 or FSVB3824, the region underneath the LSCs should be covered by solder mask.
