THS4082 Datasheet, PDF (17/32 Pages) National Semiconductor (TI) – 175 MHz High Speed AMPLIFIERS

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THS4081, THS4082
175ĆMHz LOWĆPOWER HIGHĆSPEED AMPLIFIERS
SLOS274D − DECEMBER 1999 − REVISED JUNE 2001
APPLICATION INFORMATION
general PowerPAD design considerations (continued)
Although there are many ways to properly heatsink this device, the following steps illustrate the recommended
approach.
Thermal pad area (68 mils x 70 mils) with 5 vias
(Via diameter = 13 mils)
Figure 45. PowerPAD PCB Etch and Via Pattern
1. Prepare the PCB with a top side etch pattern as shown in Figure 45. There should be etch for the leads as
well as etch for the thermal pad.
2. Place five holes in the area of the thermal pad. These holes should be 13 mils in diameter. Keep them small
so that solder wicking through the holes is not a problem during reflow.
3. Additional vias may be placed anywhere along the thermal plane outside of the thermal pad area. This helps
dissipate the heat generated by the THS408xDGN 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 wicking is not a problem.
4. Connect all holes to the internal ground plane.
5. When connecting these holes to the ground 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 under the THS408xDGN 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 solder mask should cover the five holes of the thermal pad area. This
prevents solder from being pulled away from the thermal pad area during the reflow process.
7. Apply solder paste to the exposed thermal pad area and all of the IC terminals.
8. With these preparatory steps in place, the THS408xDGN 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.
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