Datasheet

PowerPAD LAYOUT GUIDELINES
OPA454
www.ti.com ....................................................................................................................................... SBOS391A – DECEMBER 2007 – REVISED DECEMBER 2008
area to be soldered; thus, wicking is not a
problem.
The PowerPAD package allows for both assembly
6. Connect all holes to the internal power plane of
and thermal management in one manufacturing
the correct voltage potential (V – ).
operation. During the surface-mount solder operation
(when the leads are being soldered), the thermal pad 7. When connecting these holes to the plane, do not
must be soldered to a copper area underneath the use the typical web or spoke via connection
package. Through the use of thermal paths within this methodology. Web connections have a high
copper area, heat can be conducted away from the thermal resistance connection that is useful for
package into either a ground plane or other slowing the heat transfer during soldering
heat-dissipating device. Soldering the PowerPAD to operations, making the soldering of vias that have
the PCB is always required, even with applications plane connections easier. In this application,
that have low power dissipation. Follow these steps however, low thermal resistance is desired for the
to attach the device to the PCB: most efficient heat transfer. Therefore, the holes
under the OPA454 PowerPAD package should
1. The PowerPAD must be connected to the most
make the connections to the internal plane with a
negative supply voltage on the device, V – .
complete connection around the entire
2. Prepare the PCB with a top-side etch pattern.
circumference of the plated-through hole.
There should be etching for the leads as well as
8. The top-side solder mask should leave the
etch for the thermal pad.
terminals of the package and the thermal pad
3. Use of thermal vias improves heat dissipation,
area exposed. The bottom-side solder mask
but are not required. The thermal pad can
should cover the holes of the thermal pad area.
connect to the PCB using an area equal to the
This masking prevents solder from being pulled
pad size with no vias, but externally connected to
away from the thermal pad area during the reflow
V – .
process.
4. Place recommended holes in the area of the
9. Apply solder paste to the exposed thermal pad
thermal pad. Recommended thermal land size
area and all of the IC terminals.
and thermal via patterns for the SO-8 DDA
10. With these preparatory steps in place, the
package are shown in the thermal land pattern
PowerPAD IC is simply placed in position and run
mechanical drawing appended at the end of this
through the solder reflow operation as any
document. These holes should be 13 mils
standard surface-mount component. This
(.013in, or 0.3302mm) in diameter. Keep them
preparation results in a properly installed part.
small, so that solder wicking through the holes is
not a problem during reflow. The minimum
For detailed information on the PowerPAD package,
recommended number of holes for the SO-8
including thermal modeling considerations and repair
PowerPAD package is five.
procedures, see technical brief SLMA002 PowerPAD
5. Additional vias may be placed anywhere along Thermally-Enhanced Package, available for download
the thermal plane outside of the thermal pad at www.ti.com .
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
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