Recommended Pad Pattern and Thermal Performance 175 °C Rated Part

Application Note AN917

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Vishay Siliconix

Revision: 15-Apr-13

2

Document Number: 75130

THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT

Fig. 3

THERMAL PERFORMANCE

Junction-to-Foot Thermal Resistance

(the Package Performance)

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

how the thermal resistance impacts power dissipation

for the dual 6-pin SC-70 package at varying ambient

temperatures.

Alloy 42 Leadframe

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



follows:

The results indicate that designers can reduce thermal

resistance (



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

6

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SC70−6 DUAL

vishay.com

ALLOY 42 LEADFRAME

ROOM AMBIENT 25 °C

ELEVATED AMBIENT 60 °C

P

D

T

R

JA

P

D

175 °C - 25 °C

413 °C/W

P

D

363 mW

T

175 °C - 60 °C

413 °C/W

P

D

R

JA

P

D

P

D

278 mW

COOPER LEADFRAME

ROOM AMBIENT 25 °C

ELEVATED AMBIENT 60 °C

LITTLE FOOT 6-PIN SC-70

ALLOY 42

COPPER

1) Minimum recommended pad

pattern on the EVB board (see fig. 3).

518 °C/W

344 °C/W

with maximum copper both sides.

413 °C/W

224 °C/W

P

D

T

R

JA

P

D

175 °C - 25 °C

224 °C/W

P

D

669 mW

T

175 °C - 60 °C

224 °C/W

P

D

R

JA

P

D

P

D

513 mW