MJB42C ON Semiconductor, MJB42C Datasheet - Page 5

• Manufacturer Part Number: MJB42C
• Description: Complementary Silicon Plastic Power Transistors
• Manufacturer: ON Semiconductor

total design. The footprint for the semiconductor packages
must be the correct size to ensure proper solder connection
function of the Collector pad size. These 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 T
maximum rated junction temperature of the die, R
thermal resistance from the device junction to ambient, and
the operating temperature, T
on the data sheet, P
ratings table on the data sheet. Substituting these values
into the equation for an ambient temperature T
one can calculate the power dissipation of the device. For a
D
the recommended footprint on a glass epoxy printed circuit
board to achieve a power dissipation of 2.5 Watts. There are
other alternatives to achieving higher power dissipation
from the surface mount packages. One is to increase the
area of the Collector pad. By increasing the area of the
collection pad, the power dissipation can be increased.
2
Surface mount board layout is a critical portion of the
The power dissipation for a surface mount device is a
The values for the equation are found in the maximum
The 50 C/W for the D
PAK device, P
INFORMATION FOR USING THE D
P
D
P
D
= 150 C – 25 C
D
RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS
D
is calculated as follows.
=
can be calculated as follows:
50 C/W
2
T
PAK package assumes the use of
J(max)
POWER DISSIPATION FOR A SURFACE MOUNT DEVICE
A
R
. Using the values provided
JA
– T
= 2.5 Watts
A
MJB41C (NPN), MJB42C (PNP)
J(max)
A
of 25 C,
http://onsemi.com
JA
, the
, the
2
5
PAK SURFACE MOUNT PACKAGE
interface between the board and the package. With the
correct pad geometry, the packages will self align when
subjected to a solder reflow process.
Although one can almost double the power dissipation with
this method, one will be giving up area on the printed
circuit board which can defeat the purpose of using surface
mount technology. For example, a graph of R
Collector pad area is shown in Figure 14.
or an aluminum core board such as Thermal Clad . Using a
board material such as Thermal Clad, an aluminum core
board, the power dissipation can be doubled using the same
footprint.
Figure 14. Thermal Resistance versus Collector Pad
Another alternative would be to use a ceramic substrate
Area for the D
2
inches
mm
PAK Package (Typical)
JA
versus