AN1294
Application note
PowerSO-10RF: the first true RF power SMD package
Introduction
During the last years, as the size of electronic components has decreased and their
reliability increased, there has been a need across the board for various surface-mounted
components. The PowerSO-10RF is not just a new package, it is a new concept in a small
outline plastic package for RF power applications. Such applications have a great need for
surface-mount device (SMD) packages but, up until now, the available bipolar technology did
not allow for such types of package.
The main advantages of this new RF plastic package are excellent thermal performance,
high power capability, high power density and suitability for all reflow soldering methods.
The purpose of this application note is to demonstrate that the PowerSO-10RF is the perfect
solution for the new RF power LDMOS products recently introduced by STMicroelectronics.
November 2009
Doc ID 7604 Rev 3
1/20
www.st.com
Contents
AN1294
Contents
1
2
RF Power package requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
What is the PowerSO-10RF? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1
2.2
Brief overview of the PowerSO-10RF technology . . . . . . . . . . . . . . . . . . . 6
Delivery information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3
Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1
3.2
Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Segments and applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4
5
6
LDMOS in PowerSO-10RF/typical RF performances . . . . . . . . . . . . . . . 9
Quality and reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Soldering method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1
6.2
6.3
6.4
6.5
Vapor phase reflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Infrared heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Soldering paste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.3.1
Applying the soldering paste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Placement of parts and drying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Avoiding stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7
8
9
10
Mounting recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Thermal resistance and maximum power dissipation capability . . . . 17
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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Doc ID 7604 Rev 3
AN1294
List of tables
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Features and benefits of the PowerSO-10RF. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Description of reliability tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Thermal resistance and maximum power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Doc ID 7604 Rev 3
3/20
List of figures
AN1294
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
LDMOS structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
PowerSO-10RF package construction (JEDEC MO-184 standard) . . . . . . . . . . . . . . . . . . . 6
PowerSO-10RF straight and formed lead versions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
PD57045S-E in PowerSO-10RF versus SD57045-01 in ceramic package . . . . . . . . . . . . . 9
Power gain versus output power/ceramic vs. plastic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Power gain versus output power/straight leads vs. formed leads. . . . . . . . . . . . . . . . . . . . 10
Recommended heat profile/reflow soldering for PSO10RF lead-free. . . . . . . . . . . . . . . . . 14
PowerSO-10RF recommended pad layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
PowerSO-10RF recommended pad layout with via holes . . . . . . . . . . . . . . . . . . . . . . . . . 16
Mounting on copper base plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
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Doc ID 7604 Rev 3
AN1294
RF Power package requirements
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.
Doc ID 7604 Rev 3
5/20
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