OPA454_16 Datasheet, PDF (34/47 Pages) Texas Instruments – High-Voltage (100-V), High-Current (50-mA) Operational Amplifiers

OPA454
SBOS391B – DECEMBER 2007 – REVISED MARCH 2016
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Layout Guidelines (continued)
12.1.2 PowerPAD Layout Guidelines
The PowerPAD package allows for both assembly and thermal management in one manufacturing operation.
During the surface-mount solder operation (when the leads 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 can be conducted away from the package into either a ground plane or other heat-dissipating device.
Soldering the PowerPAD to the PCB is always required, even with applications that have low power dissipation.
Follow these steps to attach the device to the PCB:
1. The PowerPAD must be connected to the most negative supply voltage on the device, V–.
2. Prepare the PCB with a top-side etch pattern. There must be etching for the leads as well as etch for the
thermal pad.
3. Use of thermal vias improves heat dissipation, but are not required. The thermal pad can connect to the PCB
using an area equal to the pad size with no vias, but externally connected to V–.
4. Place recommended holes in the area of the thermal pad. Recommended thermal land size and thermal via
patterns for the SO-8 DDA package are shown in the thermal land pattern mechanical drawing appended at
the end of this document. These holes must be 13 mils (.013 in, or 0.3302 mm) in diameter. Keep them
small, so that solder wicking through the holes is not a problem during reflow. The minimum recommended
number of holes for the SO-8 PowerPAD package is five.
5. Additional vias may be placed anywhere along the thermal plane outside of the thermal pad area. These vias
help dissipate the heat generated by the OPA454 IC. These additional vias may be larger than the 13-mil
diameter vias directly under the thermal pad. They can be larger because they are not in the thermal pad
area to be soldered; thus, wicking is not a problem.
6. Connect all holes to the internal power plane of the correct voltage potential (V–).
7. When connecting these holes to the plane, do not use the typical web or spoke via 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 holes under the
OPA454 PowerPAD 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 terminals of the package and the thermal pad area exposed. The
bottom-side solder mask must cover the holes 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 IC terminals.
10. With these preparatory steps in place, the PowerPAD IC is simply placed in position and run through the
solder reflow operation as any standard surface-mount component. This preparation results in a properly
installed part.
For detailed information on the PowerPAD package, including thermal modeling considerations and repair
procedures, see technical brief SLMA002 PowerPAD Thermally-Enhanced Package, available for download at
www.ti.com.
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