Application Note AN917

VISHAY SILICONIX
www.vishay.com
Power MOSFETs
Application Note AN917
Dual-Channel LITTLE FOOT ® 6-Pin SC-70 MOSFET Copper Leadframe Version
Recommended Pad Pattern and Thermal Performance 175 °C Rated Part
INTRODUCTION
The new dual 6-pin SC-70 package with a copper leadframe
enables improved on-resistance values and enhanced
thermal performance as compared to the existing 3-pin and
6-pin packages with Alloy 42 leadframes. These devices are
intended for small to medium load applications where a
miniaturized package is required. Devices in this package
come in a range of on-resistance values, in n-channel and
p-channel versions. This technical note discusses pin-outs,
package outlines, pad patterns, evaluation board layout,
and thermal performance for the dual-channel version.
87 (mil)
26 (mil)
6
5
4
96 (mil)
71 (mil)
48 (mil)
23 (mil)
PIN-OUT
Figure 1 shows the pin-out description and pin 1
identification for the dual-channel SC-70 device in the 6-pin
configuration. Both n-and p-channel devices are available in
this package – the drawing example below illustrates the
p-channel device.
61 (mil)
1
2
3
0.0 (mil)
8 (mil)
26 (mil)
SOT-363
SC-70 (6-LEADS)
16 (mil)
S1
1
6
D1
G1
2
5
G2
D2
3
4
S2
Top View
Fig. 1
For package dimensions see outline drawing SC-70
(6-Leads) (www.vishay.com/doc?71154)
See Application Note 826, Recommended Minimum Pad
Patterns With Outline Drawing Access for Vishay Siliconix
MOSFETs, (www.vishay.com/doc?72286) for the SC-70
6-pin basic pad layout and dimensions. This pad pattern is
sufficient for the low-power applications for which this
package is intended. Increasing the drain pad pattern
(figure 2) yields a reduction in thermal resistance and is a
preferred footprint.
Revision: 15-Apr-13
EVALUATION BOARD FOR THE DUAL-CHANNEL
SC70-6
The 6-pin SC-70 evaluation board (EVB) shown in figure 3
measures 0.6 in. by 0.5 in. The copper pad traces are the
same as described in the previous section, Basic Pad
Patterns. The board allows for examination from the outer
pins to the 6-pin DIP connections, permitting test sockets to
be used in evaluation testing.
The thermal performance of the dual 6-pin SC-70 has been
measured on the EVB, comparing both the copper and Alloy
42 leadframes. This test was then repeated using the
1-inch2 PCB with dual-side copper coating.
A helpful way of displaying the thermal performance of the
6-pin SC-70 dual copper leadframe is to compare it to the
traditional Alloy 42 version.
Document Number: 75130
1
For technical questions, contact: [email protected]
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
APPLICATION NOTE
BASIC PAD PATTERNS
Fig. 2 SC-70 (6 leads) Dual
Application Note AN917
www.vishay.com
Vishay Siliconix
Dual-Channel LITTLE FOOT® 6-Pin SC-70 MOSFET Copper Leadframe Version
Recommended Pad Pattern and Thermal Performance 175 °C Rated Part
Front of Board SC70-6
Back of Board SC70-6
S1
D1
G1
G2
D2
S2
vishay.com
SC70−6 DUAL
Fig. 3
THERMAL PERFORMANCE
COOPER LEADFRAME
Junction-to-Foot Thermal Resistance
(the Package Performance)
ROOM AMBIENT 25 °C
Thermal performance for the dual SC-70 6-pin package is
measured as junction-to-foot thermal resistance, in which
the “foot” is the drain lead of the device as it connects with
the body. The junction-to-foot thermal resistance for this
device is typically 80 °C/W, with a maximum thermal
resistance of approximately 100 °C/W. This data compares
favorably with another compact, dual-channel package
- the dual TSOP-6 - which features a typical thermal
resistance of 75 °C/W and a maximum of 90 °C/W.
Power Dissipation for 175 °C Rated Part
The typical RJA for the dual-channel 6-pin SC-70 with a
copper leadframe is 224 °C/W steady-state, compared to
413 °C/W for the Alloy 42 version. All figures are based on
the 1-inch2 FR4 test board. The following example shows
how the thermal resistance impacts power dissipation
for the dual 6-pin SC-70 package at varying ambient
temperatures.
Alloy 42 Leadframe
ALLOY 42 LEADFRAME
APPLICATION NOTE
ROOM AMBIENT 25 °C
PD
T J(max.) - TA
R
JA
T J(max.) - TA
R
JA
PD
T J(max.) - TA
R
JA
PD
175 °C - 25 °C
224 °C/W
PD
175 °C - 60 °C
224 °C/W
PD
669 mW
PD
513 mW
Although they are intended for low-power applications,
devices in the 6-pin SC-70 dual-channel configuration will
handle power dissipation in excess of 0.5 W.
TESTING
To further aid the comparison of copper and Alloy 42
leadframes, Figures 4 and 5 illustrate the dual-channel 6-pin
SC-70 thermal performance on two different board sizes
and pad patterns. The measured steady-state values of
RJA for the dual 6-pin SC-70 with varying leadframes are as
follows:
LITTLE FOOT 6-PIN SC-70
ELEVATED AMBIENT 60 °C
PD
T J(max.) - TA
R
JA
PD
175 °C - 25 °C
413 °C/W
PD
175 °C - 60 °C
413 °C/W
PD
363 mW
PD
278 mW
Revision: 15-Apr-13
PD
ELEVATED AMBIENT 60 °C
1) Minimum recommended pad
pattern on the EVB board (see fig. 3).
1-inch2
2) Industry standard
PCB
with maximum copper both sides.
ALLOY 42
COPPER
518 °C/W
344 °C/W
413 °C/W
224 °C/W
The results indicate that designers can reduce thermal
resistance (JA) by 34 % simply by using the copper
leadframe device as opposed to the Alloy 42 version. In this
example, a 174 °C/W reduction was achieved without an
increase in board area. If an increase in board size is
feasible, a further 120 °C/W reduction can be obtained by
utilizing a 1-inch2. PCB area.
Document Number: 75130
2
For technical questions, contact: [email protected]
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
Application Note AN917
www.vishay.com
Vishay Siliconix
Dual-Channel LITTLE FOOT® 6-Pin SC-70 MOSFET Copper Leadframe Version
Recommended Pad Pattern and Thermal Performance 175 °C Rated Part
Dual:
Sx19xxEDH or Sx19xxEEH
Compl.:
Sx15xxEDH or Sx15xxEEH
500
500
400
400
Thermal Resistance (°C/W)
Thermal Resistance (°C/W)
The dual copper leadframe versions have the following
suffix:
300
Alloy 42
200
Copper
100
300
Alloy
42
200
100
Copper
0
0
10-5
10-4
10-3
10-2
10-1
1
10
100
1000
Time (s)
APPLICATION NOTE
Fig. 4 Dual SC70-6 Thermal Performance on EVB
Revision: 15-Apr-13
10-5
10-4
10-3
10-2
10-1
1
10
100
1000
Time (s)
Fig. 5 Dual SC70-6 Comparison on 1-inch2 PCB
Document Number: 75130
3
For technical questions, contact: [email protected]
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000