OPA561 datasheet(10/17 Pages) TI1

10 / 17 page

OPA561

SBOS206E − DECEMBER 2001 − REVISED FEBRUARY 2007

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THERMAL RESISTANCE vs

CIRCUIT BOARD COPPER AREA

123

Copper Area (inches2)

OPA561

Surface Mount Package

2oz copper

Figure 5. Thermal Resistance vs Circuit Board

Copper Area

AMPLIFIER MOUNTING

What is PowerPAD?

The OPA561 uses the HTSSOP-20 PowerPAD package,

a thermally enhanced, standard size IC package designed

to eliminate the use of bulky heatsinks and slugs

traditionally used in thermal packages. This package can

be easily mounted using standard PCB assembly tech-

niques, and can be removed and replaced using standard

repair procedures.

The PowerPAD package is designed so that the leadframe

die pad (or thermal pad) is exposed on the bottom of the

IC, as shown in Figure 6. This provides an extremely low

thermal resistance (

qJC ) path between the die and the

exterior of the package. The thermal pad on the bottom of

the IC must be soldered directly to the PCB, using the PCB

as a heatsink. In addition, through the use of thermal vias,

the thermal pad can be directly connected to a ground

plane or special heatsink structure designed into the PCB.

Mold Compound (Epoxy)

Leadframe Die Pad

Exposed atBaseofthe Package

Leadframe (Copper Alloy)

IC (Silicon)

Die Attach (Epoxy)

Figure 6. Section View of a PowerPAD Package

Soldering

the

PowerPAD

the

PCB

always

recommended, even with applications that have low power

dissipation. It provides the necessary connection between

the leadframe die and the PCB. The PowerPAD must be

connected to the most negative supply of the device.

PowerPAD Assembly Process

Prepare the PCB with a top side etch pattern, as

shown in the attached Thermal Land Pattern

mechanical drawing. There should be etch for the

leads as well as etch for the thermal land.

Place the recommended number of holes (or thermal

vias) in the area of the thermal pad as shown on the

attached Land Pattern mechanical. These holes

should be 13 mils in diameter. They are kept small so

that solder wicking through the holes is not a problem

during reflow.

It is recommended, but not required, to place a small

number of the holes under the package and outside

the thermal pad area. These holes provide additional

heat path between the copper land and ground plane

and are 25 mils in diameter. They may be larger

because they are not in the area to be soldered, so

wicking is not a problem.

Connect all holes, including those within the thermal

pad area and outside the pad area, to the internal

ground plane or other internal copper plane.

When connecting these holes to the ground plane, do

not use the typical web or spoke via connection

methodology; see Figure 7. Web connections have a

high thermal resistance connection that is useful for

slowing the heat transfer during soldering operations.

This makes the soldering of vias that have plane

connections easier. However, in this application, low

thermal resistance is desired for the most efficient

heat transfer. Therefore, the holes under the

PowerPAD package should make their connection to

the internal ground plane with a complete connection

around the entire circumference of the plated through

hole.

Web or Spoke Via

Solid Via

NOT RECOMMENDED

RECOMMENDED

Figure 7. Via Connection

Not Recommended for New Designs

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