Datasheet
PowerPAD DESIGN CONSIDERATIONS PowerPAD PCB LAYOUT CONSIDERATIONS
DIE
Side View (a)
DIE
End View (b)
Thermal
Pad
Bottom View (c)
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
THS4504
THS4505
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......................................................................................................................................................... SLOS363D – AUGUST 2002 – REVISED MAY 2008
1. Prepare the PCB with a top side etch pattern as
The THS4500 family is available in a
shown in Figure 90 . There should be etch for the
thermally-enhanced PowerPAD family of packages.
leads as well as etch for the thermal pad.
These packages are constructed using a downset
leadframe upon which the die is mounted [see
2. Place five holes in the area of the thermal pad.
Figure 89 (a) and Figure 89 (b)]. This arrangement
These holes should be 13 mils in diameter. Keep
results in the lead frame being exposed as a thermal
them small so that solder wicking through the
pad on the underside of the package [see
holes is not a problem during reflow.
Figure 89 (c)]. Because this thermal pad has direct
3. Additional vias may be placed anywhere along
thermal contact with the die, excellent thermal
the thermal plane outside of the thermal pad
performance can be achieved by providing a good
area. This helps dissipate the heat generated by
thermal path away from the thermal pad.
the THS4500 family IC. These additional vias
may be larger than the 13-mil diameter vias
The PowerPAD package allows for both assembly
directly under the thermal pad. They can be
and thermal management in one manufacturing
larger because they are not in the thermal pad
operation. During the surface-mount solder operation
area to be soldered so that wicking is not a
(when the leads are being soldered), the thermal pad
problem.
can also be soldered to a copper area underneath the
package. Through the use of thermal paths within this
4. Connect all holes to the internal ground plane.
copper area, heat can be conducted away from the
5. When connecting these holes to the ground
package into either a ground plane or other heat
plane, do not use the typical web or spoke via
dissipating device.
connection methodology. Web connections have
a high thermal resistance connection that is
The PowerPAD package represents a breakthrough
useful for slowing the heat transfer during
in combining the small area and ease of assembly of
soldering operations. This makes the soldering of
surface mount with the, heretofore, awkward
vias that have plane connections easier. In this
mechanical methods of heatsinking.
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.
6. The top-side solder mask should leave the
terminals of the package and the thermal pad
area with its five holes exposed. The bottom-side
Figure 89. Views of Thermally Enhanced Package
solder mask should cover the five holes of the
thermal pad area. This prevents solder from
Although there are many ways to properly heatsink
being pulled away from the thermal pad area
the PowerPAD package, the following steps illustrate
during the reflow process.
the recommended approach.
7. Apply solder paste to the exposed thermal pad
area and all of the IC terminals.
8. With these preparatory steps in place, the IC is
simply placed in position and run through the
solder reflow operation as any standard
surface-mount component. This results in a part
that is properly installed.
Figure 90. View of Thermally Enhanced Package
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