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BOTTOM-SIDE PowerPAD LAYOUT

OPA454

SBOS391 – DECEMBER 2007

area to be soldered; thus, wicking is not a

GUIDELINES

problem.

6. Connect all holes to the internal power plane of

The PowerPAD package allows for both assembly

the correct voltage potential (V–).

and thermal management in one manufacturing

operation. During the surface-mount solder operation

7. When connecting these holes to the plane, do not

(when the leads are being soldered), the thermal pad

use the typical web or spoke via connection

must be soldered to a copper area underneath the

methodology. Web connections have a high

package. Through the use of thermal paths within this

thermal resistance connection that is useful for

copper area, heat can be conducted away from the

slowing

the

heat

transfer

during

soldering

package

into

either

ground

plane

other

operations, making the soldering of vias that have

heat-dissipating device. Soldering the PowerPAD to

plane connections easier. In this application,

the PCB is always required, even with applications

however, low thermal resistance is desired for the

that have low power dissipation. Follow these steps

most efficient heat transfer. Therefore, the holes

to attach the device to the PCB:

under the OPA454 PowerPAD package should

make the connections to the internal plane with a

1. The PowerPAD must be connected to the most

complete

connection

around

the

entire

negative supply voltage on the device, V–.

circumference of the plated-through hole.

2. Prepare the PCB with a top-side etch pattern.

8. The top-side solder mask should leave the

There should be etching for the leads as well as

terminals of the package and the thermal pad

etch for the thermal pad.

area exposed. The bottom-side solder mask

3. Use of thermal vias improves heat dissipation,

should cover the holes of the thermal pad area.

but are not required. The thermal pad can

This masking prevents solder from being pulled

connect to the PCB using an area equal to the

away from the thermal pad area during the reflow

pad size with no vias, but externally connected to

process.

V–.

9. Apply solder paste to the exposed thermal pad

4. Place recommended holes in the area of the

area and all of the IC terminals.

thermal pad. Recommended thermal land size

10. With these preparatory steps in place, the

and thermal via patterns for the SO-8 DDA

PowerPAD IC is simply placed in position and run

package are shown in the thermal land pattern

through the solder reflow operation as any

mechanical drawing appended at the end of this

standard

surface-mount

component.

This

document. These holes should be 13 mils in

preparation results in a properly installed part.

diameter. Keep them small, so that solder wicking

through the holes is not a problem during reflow.

For detailed information on the PowerPAD package,

The minimum recommended number of holes for

including thermal modeling considerations and repair

the SO-8 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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