AN1294

RF Power package requirements

Doc ID 7604 Rev 3

5/20

1

RF Power package requirements

The most important requirement in an RF power package is a good heat dissipation

capability. The package must be able to dissipate heat so that the die temperature remains

below a pre-defined maximum temperature, above which damage might occur. Other

important features of a good RF package include low inter-electrode capacitance, low

parasitic inductance, high electrical conductivity, reliability and low cost.

Figure 1.

LDMOS structure

In conventional DMOS or bipolar vertical technology, an electrical insulator (Beryllium oxide

or BeO, which is highly toxic), is required to isolate the drain from the ground. In an LDMOS

structure where both the N+ source and the drain region are on the die surface with a

laterally diffused low resistance P+ sinker connecting the source region to the P+ substrate

and source terminal (Figure 1: LDMOS structure on page 5), this insulator is no longer

needed. This not only means that electrical and thermal performances are greatly improved,

but also that the standard DMOS ceramic package (with BeO) used for 1 W and above

devices can be replaced by a plastic package.