During the surface-mount solder operation (when the pins are being soldered), the thermal pad must be soldered to a copper area underneath the package. Through the use of thermal paths within this copper area, heat is conducted away from the package into a V− plane. Always solder the thermal pad to the PCB, even with applications that have low power dissipation. Follow these steps to attach the device to the PCB:

1. Connect the thermal pad to the most negative supply voltage on the device, V–.
2. Prepare the PCB with a top-side pattern. There must be patterning for the pins and thermal pad.
3. Thermal vias improve heat dissipation, but are not required.
4. Place recommended vias in the area of the thermal pad. Recommended thermal land size and thermal via patterns for the WSON-12 DNT package are shown in the thermal land pattern mechanical drawing appended at the end of this document. Keep the vias small, so that solder wicking through the vias is not a problem during reflow. Use a 0.2mm size via with a minimum of five connected directly below the thermal pad.
5. Additional vias can be placed anywhere along the thermal plane outside of the thermal pad area. These vias help dissipate the heat generated by the OPA598 device. These additional vias can be larger than the vias directly under the thermal pad because the additional vias are not in the thermal pad area to be soldered; thus wicking is not a problem.
6. Connect all vias to the internal power plane of the correct voltage potential, V–.
7. When connecting these vias to the plane, do not use the typical web or spoke through connection methodology. Web connections have a high thermal resistance connection that is useful for slowing the heat transfer during soldering operations, making the soldering of vias that have plane connections easier. In this application, however, low thermal resistance is desired for the most efficient heat transfer. Therefore, the vias under the OPA598 WSON package must make the connections to the internal plane with a complete connection around the entire circumference of the plated-through hole.
8. The top-side solder mask must leave the pins of the package and the thermal pad area exposed. The bottom-side solder mask must cover the vias of the thermal pad area. This masking prevents solder from being pulled away from the thermal pad area during the reflow process.
9. Apply solder paste to the exposed thermal pad area and all of the device pins.
10. With these preparatory steps in place, simply place the device in position, and run through the solder reflow operation as with any standard surface-mount component.