Datasheet

0.060
0.040
0.075 0.025
0.205
0.010
vias
Pin 1
Top View
0.017
0.035
0.094
0.030
0.013
DIE
Side View (a)
DIE
End View (b)
Thermal
Pad
Bottom View (c)
THS4500
THS4501
SLOS350F –APRIL 2002–REVISED OCTOBER 2011 www.ti.com
the THS4500 family parts directly onto the board.
PowerPAD DESIGN CONSIDERATIONS
The THS4500 family is available in a
thermally-enhanced PowerPAD set of packages.
These packages are constructed using a downset
leadframe upon which the die is mounted [see
Figure 112(a) and Figure 112(b)]. This arrangement
results in the lead frame being exposed as a thermal
pad on the underside of the package [see
Figure 112(c)]. Because this thermal pad has direct
thermal contact with the die, excellent thermal
performance can be achieved by providing a good
thermal path away from the thermal pad.
The PowerPAD package allows for both assembly
Figure 113. PowerPAD PCB Etch and Via Pattern
and thermal management in one manufacturing
operation. During the surface-mount solder operation
(when the leads are being soldered), the thermal pad
PowerPAD PCB LAYOUT CONSIDERATIONS
can also be soldered to a copper area underneath the
package. Through the use of thermal paths within this
1. Prepare the PCB with a top side etch pattern as
copper area, heat can be conducted away from the
shown in Figure 113. There should be etch for
package into either a ground plane or other heat
the leads as well as etch for the thermal pad.
dissipating device.
2. Place five holes in the area of the thermal pad.
These holes should be 13 mils (0.33 mm) in
The PowerPAD package represents a breakthrough
diameter. Keep them small so that solder wicking
in combining the small area and ease of assembly of
through the holes is not a problem during reflow.
surface mount with the, heretofore, awkward
mechanical methods of heatsinking.
3. Additional vias may be placed anywhere along
the thermal plane outside of the thermal pad
area. These holes help dissipate the heat
generated by the THS4500 family 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 area to be soldered so that wicking
is not a problem.
4. Connect all holes to the internal ground plane.
Figure 112. Views of PowerPAD,
5. When connecting these holes to the ground
Thermally-Enhanced Package
plane, do not use the typical web or spoke via
connection methodology. Web connections have
a high thermal resistance connection that is
Although there are many ways to properly heatsink
useful for slowing the heat transfer during
the PowerPAD package, the following steps illustrate
soldering operations. This transfer slowing makes
the recommended approach.
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 THS4500
family PowerPAD package should make their
connection to the internal ground plane with a
complete connection around the entire
circumference of the plated-through hole.
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