BANNOCKBURN, IL -- IPC (ipc.org) has released the B revision of IPC-7351, Generic Requirements for Surface Mount Design and Land Pattern Standard. The revision provides industry consensus guidance on land pattern geometries, as well as surface mount design recommendations for achieving the best solder joints.
A major addition to IPC-7351B, the new padstack naming convention, consists of combinations of letters and numbers that represent the shape or dimensions of lands on different layers of printed boards or documentation. The padstack naming convention enables a designer to convey all variations and dimensions of a padstack, employing it in combination with intelligent land pattern conventions also defined within the standard, according to design rules established in the IPC-2220 design series.
The standard directs users on an appropriate land pattern based on desired component density through the provision of three separate land pattern geometries for each component. The revision introduces land pattern design guidance and rules for new surface mount component families such as electrolytic aluminum capacitors; small outline diode, flat lead; small outline transistor, flat lead, and dual flat no-lead devices.
Several device families, including DPAK, QFP and QFN, often feature thermal pads on the bottom of the packages that...