NTMD2C02R2
http://onsemi.com
10
INFORMATION FOR USING THE SOIC−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
SOIC−8 POWER DISSIPATION
The power dissipation of the SOIC−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
determined by T
J(max)
, the maximum rated junction
temperature of the die, R
JA
, the thermal resistance from
the device junction to ambient; and the operating
temperature, T
A
. Using the values provided on the data
sheet for the SOIC−8 package, P
D
can be calculated as
follows:
P
D
=
T
J(max)
− T
A
R
JA
The values for the equation are found in the maximum
ratings table on the data sheet. Substituting these values
into the equation for an ambient temperature T
A
of 25°C,
one can calculate the power dissipation of the device which
in this case is 2.0 Watts.
P
D
=
150°C − 25°C
62.5°C/W
= 2.0 Watts
The 62.5°C/W for the SOIC−8 package assumes the
recommended footprint on a glass epoxy printed circuit
board to achieve a power dissipation of 2.0 Watts using the
footprint shown. Another alternative would be to use a
ceramic substrate or an aluminum core board such as
Thermal Cladt. Using board material such as Thermal
Cladt, 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.
