BCP69T1
INFORMATION FOR USING THE SOT-223 SURFACE MOUNT PACKAGE
POWER DISSIPATION
The power dissipation of the SOT-223 is a function of the
input pad size. These 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 equation for an ambient temperature T of 25°C, one can
calculate the power dissipation of the device which in this
case is 1.5 watts.
A
150°C – 25°C
determined by T , the maximum rated junction
J(max)
PD
=
= 1.5 watts
83.3°C/W
temperature of the die, R , the thermal resistance from the
θJA
device junction to ambient; and the operating temperature,
The 83.3°C/W for the SOT-223 package assumes the
recommended collector pad area of 965 sq. mils on a glass
epoxy printed circuit board to achieve a power dissipation of
1.5 watts. If space is at a premium, a more realistic approach
T . Using the values provided on the data sheet for the
A
SOT-223 package, P can be calculated as follows.
D
TJ(max) – TA
is to use the device at a P of 833 mW using the footprint
PD
=
D
Rθ
JA
shown. Using a board material such as Thermal Clad, a
power dissipation of 1.6 watts can be achieved using the
same footprint.
The values for the equation are found in the maximum
ratings table on the data sheet. Substituting these values into
MOUNTING 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.
• 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.
• Always preheat the device.
• The delta temperature between the preheat and soldering
should be 100°C or less.*
• Mechanical stress or shock should not be applied during
• 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.
cooling
* Soldering a device without preheating can cause
excessive thermal shock and stress which can result in
damage to the device.
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 insure 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.
0.15
3.8
0.079
2.0
0.248
6.3
0.091
2.3
0.091
2.3
0.079
2.0
inches
mm
0.059
1.5
0.059
1.5
0.059
1.5
SOT-223
http://onsemi.com
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