MCR08B ON, MCR08B Datasheet - Page 7

• Manufacturer Part Number: MCR08B
• Description: SENSITIVE GATE SILICON CONTROLLED RECTIFIERS
• Manufacturer: ON

total design. The footprint for the semiconductor packages
must be the correct size to insure proper solder connection
anode 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 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 SOT-223 package, P D can be calculated as
follows:
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 550 milliwatts.
circuit board, solder paste must be applied to the pads. A
solder stencil is required to screen the optimum amount of
solder paste onto the footprint. The stencil is made of brass
Surface mount board layout is a critical portion of the
The power dissipation of the SOT-223 is a function of the
The values for the equation are found in the maximum
Prior to placing surface mount components onto a printed
P D = 110 C – 25 C = 550 milliwatts
INFORMATION FOR USING THE SOT-223 SURFACE MOUNT PACKAGE
MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS
P D =
156 C/W
T J(max) – T A
R JA
0.079
2.0
SOLDER STENCIL GUIDELINES
SOT-223 POWER DISSIPATION
0.079
2.0
0.059
1.5
MCR08B, MCR08M
http://onsemi.com
0.091
2.3
SOT-223
0.059
0.15
1.5
3.8
7
0.091
2.3
interface between the board and the package. With the
correct pad geometry, the packages will self align when
subjected to a solder reflow process.
of the recommended footprint on a glass epoxy printed
circuit board to achieve a power dissipation of 550
milliwatts. There are other alternatives to achieving higher
power dissipation from the SOT-223 package. One is to
increase the area of the anode pad. By increasing the area of
the anode pad, the power dissipation can be increased.
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. A graph of R JA versus anode pad area
is shown in Figure 3.
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.
or stainless steel with a typical thickness of 0.008 inches.
The stencil opening size for the SOT-223 package should
be the same as the pad size on the printed circuit board, i.e.,
a 1:1 registration.
The 156 C/W for the SOT-223 package assumes the use
Another alternative would be to use a ceramic substrate
0.059
1.5
0.248
inches
mm
6.3