MMFT107T1

http://onsemi.com

5

0.8 Watts

1.25 Watts*

1.5 Watts

A, Area (square inches)

0.0

0.2

0.4

0.6

0.8

1.0

160

140

120

100

80

Figure 9. Thermal Resistance versus Collector

Pad Area for the SOT-223 Package (Typical)

Board Material = 0.0625″

G10/FR4, 2 oz Copper

TA = 25°C

*Mounted on the DPAK footprint

°

Another alternative would be to use a ceramic substrate

or an aluminum core board such as Thermal Clad

t. Using

a board material such as Thermal Clad, an aluminum core

board, the power dissipation can be doubled using the same

footprint.

SOLDER STENCIL GUIDELINES

Prior to placing surface mount components onto a printed

circuit board, solder paste must be applied to the pads. A

solder stencil is required to screen the optimum amount of

solder paste onto the footprint. The stencil is made of brass

or stainless steel with a typical thickness of 0.008 inches.

The stencil opening size for the SOT-223 package should

be the same as the pad size on the printed circuit board, i.e.,

a 1:1 registration.

SOLDERING PRECAUTIONS

The melting temperature of solder is higher than the rated

temperature of the device. When the entire device is heated

to a high temperature, failure to complete soldering within

a short time could result in device failure. Therefore, the

following items should always be observed in order to

minimize the thermal stress to which the devices are

subjected.

• Always preheat the device.

• The delta temperature between the preheat and

soldering should be 100

°C or less.*

• When preheating and soldering, the temperature of the

leads and the case must not exceed the maximum

temperature ratings as shown on the data sheet. When

using infrared heating with the reflow soldering

method, the difference should be a maximum of 10

°C.

• The soldering temperature and time should not exceed

260

°C for more than 10 seconds.

• When shifting from preheating to soldering, the

maximum temperature gradient should be 5

°C or less.

• After soldering has been completed, the device should

be allowed to cool naturally for at least three minutes.

Gradual cooling should be used as the use of forced

cooling will increase the temperature gradient and

result in latent failure due to mechanical stress.

• Mechanical stress or shock should not be applied

during cooling

* Soldering a device without preheating can cause

excessive thermal shock and stress which can result in

damage to the device.