OPA454 Datasheet, PDF (23/36 Pages) Texas Instruments – High-Voltage (100V), High-Current (50mA) OPERATIONAL AMPLIFIERS, G = 1 Stable

OPA454
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BOTTOM-SIDE 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 should 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 should be 13 mils 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
SBOS391 – DECEMBER 2007
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 should
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 should leave the
terminals of the package and the thermal pad
area exposed. The bottom-side solder mask
should 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.
Copyright © 2007, Texas Instruments Incorporated
Product Folder Link(s): OPA454
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