MMSF5P02HD

http://onsemi.com

9

INFORMATION FOR USING THE SO−8 SURFACE MOUNT PACKAGE

MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS

Surface mount board layout is a critical portion of the total

design. The footprint for the semiconductor packages must

be the correct size to ensure proper solder connection

interface between the board and the package. With the

correct pad geometry, the packages will self−align when

subjected to a solder reflow process.

mm

inches

0.060

1.52

0.275

7.0

0.024

0.6

0.050

1.270

0.155

4.0

SO−8 POWER DISSIPATION

The power dissipation of the SO−8 is a function of the

input pad size. This can vary from the minimum pad size

for soldering to the pad size given for maximum power

dissipation. Power dissipation for a surface mount device is

the device junction to ambient; and the operating

follows:

The values for the equation are found in the maximum

ratings table on the data sheet. Substituting these values

one can calculate the power dissipation of the device which

in this case is 1.6 Watts.

150°C − 25°C

80°C/W

= 1.6 Watts

The 80°C/W for the SO−8 package assumes the

recommended footprint on a glass epoxy printed circuit

board to achieve a power dissipation of 1.6 Watts using the

footprint shown. Another alternative would be to use a

ceramic substrate or an aluminum core board such as

Thermal Clad

t. Using board material such as Thermal

Clad, the power dissipation can be doubled using the same

footprint.

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 shall be a maximum of 10°C.

• The soldering temperature and time shall not exceed

260°C for more than 10 seconds.

• When shifting from preheating to soldering, the

maximum temperature gradient shall 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.