MBD54–3/4

Surface mount board layout is a critical portion of the

total design. The footprint for the semiconductor packages

must be the correct size to insure proper solder connection

MBD110DWT1 MBD330DWT1 MBD770DWT1

INFORMATION FOR USING THE SOT–363 SURFACE MOUNT PACKAGE

MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS

interface between the board and the package. With the

correct pad geometry, the packages will self align when

subjected to a solder reflow process.

SOT–363

0.5 mm (min)

SOT–363 POWER DISSIPATION

1.9 mm

The power dissipation of the SOT–363 is a function of

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

soldering to a pad size given for maximum power dissipation.

Power dissipation for a surface mount device is determined

values provided on the data sheet for the SOT–363 package,

PD

can be calculated as 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 150 milliwatts.

P

D

=

150°C – 25°C

= 150 milliwatts

833°C/W

The 833°C/W for the SOT–363 package assumes the use

of the recommended footprint on a glass epoxy printed

circuit board to achieve a power dissipation of 150 milliwatts.

There are other alternatives to achieving higher power dis-

sipation from the SOT–363 package. Another alternative

would be to use a ceramic substrate or

an aluminum core board such as Thermal CladE. Using a

board material such as Thermal Clad, an aluminum core

board, 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 com-

plete soldering within a short time could result in de-

vice failure. Therefore, the following items should al-

ways 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 sol-

dering 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 maxi-

mum 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 dur-

ing cooling.

* Soldering a device without preheating can cause ex-

cessive thermal shock and stress which can result in

damage to the device.