MMSZ5221BT1, MMSZ4678T1, MMSZ2V4T1 Series
INFORMATION FOR USING THE SOD-123 SURFACE MOUNT PACKAGE
MINIMUM RECOMMENDED FOOTPRINTS FOR
0.91
0.036
SURFACE MOUNT 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.
1.22
0.048
The minimum recommended footprint for the SOD-123 is
shown at the right.
The SOD-123 package can be used on existing surface
mount boards which have been designed for the leadless 34
package style. The footprint compatibility makes conversion
from leadless 34 to SOD-123 straightforward.
2.36
0.093
4.19
mm
inches
0.165
Figure 11. Minimum Recommended Footprint
SOD-123 POWER DISSIPATION
The power dissipation of the SOD-123 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 by
ratings table on the data sheet. Substituting these values into
the equation for an ambient temperature T of 25°C, one can
A
calculate the power dissipation of the device which in this case
is 0.37 watts.
T
R
, the maximum rated junction temperature of the die,
, the thermal resistance from the device junction to
J(max)
θJA
150°C – 25°C
P
=
= 0.37 watts
D
ambient; and the operating temperature, T . Using the values
provided on the data sheet for the SOD-123 package, P can
D
be calculated as follows:
340°C/W
A
The 340°C/W for the SOD-123 package assumes using
recommended footprint shown on FR-4 glass epoxy printed
circuit board. Another alternative is to use a ceramic substrate
or an aluminum core board such as Thermal Clad . By using
an aluminum core board material such as Thermal Clad, the
power dissipation can be doubled using the same footprint.
T
– T
A
J(max)
P
=
D
R
θJA
The values for the equation are found in the maximum
GENERAL 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.
Motorola TVS/Zener Device Data
500 mW Leadless (SOD-123) Data Sheet
7-152
MOTOROLA [ MOTOROLA ]
