Datasheet

DIE
DIE
Thermal
Pad
(a)SideView
(b)EndView
(c)BottomView
68mils 70mils(0,1727cm 0,1778cm)
(viadiameter=13mils(0,03302cm)
´ ´
SingleorDual
OPA1632
www.ti.com SBOS286B –DECEMBER 2003–REVISED JANUARY 2010
PowerPAD DESIGN CONSIDERATIONS 3. Place five holes in the area of the thermal pad.
These holes should be 13mils (0,03302cm) in
The OPA1632 is available in a thermally-enhanced
diameter. Keep them small so that solder wicking
PowerPAD family of packages. These packages are
through the holes is not a problem during reflow.
constructed using a downset leadframe upon which
4. Additional vias may be placed anywhere along
the die is mounted (see Figure 13[a] and
the thermal plane outside of the thermal pad
Figure 13[b]). This arrangement results in the lead
area. These vias help dissipate the heat
frame being exposed as a thermal pad on the
generated by the OPA1632 IC, and may be larger
underside of the package (see Figure 13[c]). Because
than the 13mil diameter vias directly under the
this thermal pad has direct thermal contact with the
thermal pad. They can be larger because they
die, excellent thermal performance can be achieved
are not in the thermal pad area to be soldered so
by providing a good thermal path away from the
that wicking is not a problem.
thermal pad.
5. Connect all holes to the internal ground plane.
6. 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. This makes 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
Figure 13. Views of the Thermally-Enhanced
under the OPA1632 PowerPAD package should
Package
make their connection to the internal plane with a
complete connection around the entire
circumference of the plated-through hole.
The PowerPAD package allows for both assembly
and thermal management in one manufacturing 7. The top-side solder mask should leave the
operation. During the surface-mount solder operation terminals of the package and the thermal pad
(when the leads are being soldered), the thermal pad area with its five holes exposed. The bottom-side
must be soldered to a copper area underneath the solder mask should cover the five holes of the
package. Through the use of thermal paths within this thermal pad area. This prevents solder from
copper area, heat can be conducted away from the being pulled away from the thermal pad area
package into either a ground plane or other during the reflow process.
heat-dissipating device. Soldering the PowerPAD to
8. Apply solder paste to the exposed thermal pad
the printed circuit board (PCB) is always required,
area and all of the IC terminals.
even with applications that have low power
With these preparatory steps in place, the IC is
dissipation. It provides the necessary thermal and
simply placed in position and runs through the
mechanical connection between the lead frame die
solder reflow operation as any standard
pad and the PCB.
surface-mount component. This results in a part
that is properly installed.
PowerPAD PCB LAYOUT CONSIDERATIONS
1. The PowerPAD is electrically isolated from the
silicon and all leads. Connecting the PowerPAD
to any potential voltage between the
power-supply voltages is acceptable, but it is
recommended to tie to ground because it is
generally the largest conductive plane.
2. Prepare the PCB with a top-side etch pattern, as
shown in Figure 14. There should be etch for the
Figure 14. PowerPAD PCB Etch and Via Pattern
leads as well as etch for the thermal pad.
space
Copyright © 2003–2010, Texas Instruments Incorporated 9
Product Folder Link(s): OPA1632