MAC08BT1(2000) 데이터 시트보기 (PDF) - ON Semiconductor

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MAC08BT1
(Rev.:2000)

Sensitive Gate Triacs

ON Semiconductor 

MAC08BT1, MAC08MT1

INFORMATION FOR USING THE SOT-223 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 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.

0.15

3.8

0.079

2.0

0.091

2.3

0.091

2.3

0.079

2.0

0.059

1.5

0.059

1.5

0.059

1.5

SOT-223

0.248

6.3

inches

mm

SOT-223 POWER DISSIPATION

The power dissipation of the SOT-223 is a function of the

MT2 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 TJ(max), the maximum rated junction

temperature of the die, RθJA, the thermal resistance from

the device junction to ambient, and the operating

temperature, TA. Using the values provided on the data

sheet for the SOT-223 package, PD can be calculated as

follows:

PD =

TJ(max) – TA

RθJA

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 TA of 25°C,

one can calculate the power dissipation of the device which

in this case is 550 milliwatts.

PD = 110°C – 25°C = 550 milliwatts

156°C/W

The 156°C/W for the SOT-223 package assumes the use

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 MT2 pad. By increasing the area of

the MT2 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 RθJA versus MT2 pad area is

shown in Figure 3.

Another alternative would be to use a ceramic substrate

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.

SOLDER STENCIL GUIDELINES

Prior to placing surface mount components onto a printed

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

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.

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