THS4021, THS4022

350-MHz LOW-NOISE HIGH-SPEED AMPLIFIERS

SLOS265B – SEPTEMBER 1999 – REVISED FEBRUARY 2000

15

POST OFFICE BOX 655303

APPLICATION INFORMATION

general PowerPAD design considerations (continued)

DIE

Side View (a)

End View (b)

Bottom View (c)

DIE

Thermal

Pad

NOTE A: The thermal pad is electrically isolated from all terminals in the package.

Figure 37. Views of Thermally Enhanced DGN Package

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 38. PowerPAD PCB Etch and Via Pattern

1.

Prepare the PCB with a top side etch pattern as shown in Figure 38. 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 THS402xDGN 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 THS402xDGN 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 THS402xDGN 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.