OPA357 Datasheet, PDF (17/23 Pages) Burr-Brown (TI) – 250MHz, Rail-to-Rail I/O, CMOS Operational Amplifier with Shutdown

www.ti.com
PowerPAD THERMALLY ENHANCED
PACKAGE
The OPA357 uses the SO-8 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
techniques.
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 10. This provides an extremely low
thermal resistance (q_JC) path between the die and the
exterior of the package. The thermal pad on the bottom of
the IC is then soldered directly to the PCB, using the PCB
as a heatsink. In addition, plated-through holes (vias)
provide a low thermal resistance heat flow path to the back
side of the PCB.
OPA357
OPA2357
SBOS235C − MARCH 2002− REVISED MAY 2004
PowerPAD ASSEMBLY PROCESS
1. The PowerPAD must be connected to the device’s most
negative supply voltage, which will be ground in
single-supply applications, and V− in split−supply
applications.
2. Prepare the PCB with a top-side etch pattern, as shown
in Figure 11. The exact land design may vary based on the
specific assembly process requirements. There should be
etch for the leads as well as etch for the thermal land.
Thermal Land
(Copper)
Minimum Size
4.8mm x 3.8mm
(189 mils x 150 mils)
OPTIONAL:
Additional 4 vias outside
of thermal pad area but
under the package.
REQUIRED:
Thermal pad area 2.286mm x 2.286mm
(90 mils x 90 mils) with 5 vias
(via diameter = 13 mils)
Leadframe (Copper Alloy)
IC (Silicon)
Die Attach (Epoxy)
Mold Compound (Plastic)
Leadframe Die Pad
Exposed at Base of the Package
(Copper Alloy)
Figure 10. Section View of a PowerPAD Package
Figure 11. 8-Pin PowerPAD PCB Etch and Via
Pattern
3. Place the recommended number of plated-through
holes (or thermal vias) in the area of the thermal pad.
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. The minimum recommended
number of holes for the SO-8 PowerPAD package is 5, as
shown in Figure 11.
4. It is recommended, but not required, to place a small
number of additional holes under the package and outside
the thermal pad area. These holes provide additional heat
paths between the copper thermal land and the ground
plane. They may be larger because they are not in the area
to be soldered, so wicking is not a problem. This is
illustrated in Figure 11.
17