MBV109T1 Datasheet, PDF (3/8 Pages) ON Semiconductor – Silicon Epicap Diodes

MBV109T1 MMBV109LT1 MV209
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.
0.025
0.65
0.025
0.65
0.037
0.95
0.037
0.95
0.035
0.9
0.075
1.9
0.028
0.7
SC–70/SOT–323
inches
mm
0.035
0.9
0.079
2.0
0.031
0.8
SOT–23
inches
mm
POWER DISSIPATION FOR A SURFACE MOUNT DEVICE
The power dissipation for a surface mount device is a function
The 556°C/W for the SOT–23 assumes the use of the
of the pad size. These can vary from the minimum pad size for recommended footprint on a glass epoxy printed circuit
soldering to the pad size given for maximum power dissipation. board to achieve a power dissipation of 225 milliwatts.
Power dissipation for a surface mount device is determined by There are other alternatives to achieving higher power
T_J(max), the maximum rated junction temperature of the die,
R_θJA, the thermal resistance from the device junction to
ambient; and the operating temperature, T_A. Using the values
dissipation from the surface mount packages. One is to
increase the area of the drain/collector pad. By increasing
the area of the drain/collector pad, the power dissipation can
provided on the data sheet, P_D can be calculated as follows.
P_D =
T_J(max) – T_A
R_θJA
The values for the equation are found in the maximum ratings
be increased. Although the power dissipation can almost be
doubled with this method, area is taken up on the printed
circuit board which can defeat the purpose of using surface
mount technology.
table on the data sheet. Substituting these values into the
Another alternative would be to use a ceramic substrate or
equation for an ambient temperature T_A of 25°C, one can
calculate the power dissipation of the device. For example, for
an aluminum core board such as Thermal Clad™. Using a
board material such as Thermal Clad, an aluminum core
a SOT–23 device, P_D is calculated as follows.
P_D =
150°C – 25°C
556°C/W
= 225 milliwatts
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 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.
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