SOT-223 POWER DISSIPATION
The power dissipation of the SOT-223 is afunction of the culate the power dissipation of the device which in this case is
collector pad size. This can vary from the minimum pad size 1.5 watts.
for soldering to the pad size given for maximum power dissipa-
tion. Power dissipation for asurface mount device is deter- pD =150°C –25°C =1,5 watts
mined by TJ(m~), the maximum rated junction temperature 83.3”CW
of the die, ReJA, the thermal resistance from the device junc-
tion to ambient; and the operating temperature, TA. Using the The 83.3°C~ assumes the recommended collecl~r pad
values provided on the data sheet, PD can be calculated as fol- area of 965 mi12 on a glass epoxy printed circuit?@@@ to
lows. achieve apower dissipation of 1.5 watts. If spa~~$~f~a pre-
TJ(max) –TA mium, amore realistic approach is to use the.Q,+~~&at aPD
pD =of 800 milliwatts using the footprint shown,. $~}$~w alternative
ReJA would be to use aceramic substrate ,pP+,~~+#Uminum core
The values for the equation are found in the maximum rat- board such as Thermal Clad. Using ~,@#r@material such as
ings table on the data sheet. Substituting these values into the ~\‘‘$?t:
Thermal CladTM,an aluminum cord%oa~, the power dissipa-
equation for an ambient temperature TA of 25°C, one can cal- tion can be doubled using the saTe’’Mtprint.
.:?>*..~:..
‘$,.,i,.$,\;y*
i~).... .k~..,.
is Y.\,,+
,..<.)$.,,
MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNT#~;&PPLICATIONS
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‘%:av”~
The melting temperatq@’)&$~6@er is higher than the rated ence in temperatures of the case and the leads shall be
temperature of the de~ce’$wfhe entire device is heated to aAl O°C or less.
high temperature; th~~~,brp failure to complete soldering with- ●The soldering temperature and time shall not exceed 260°C
in ashoti time at ~“~~#’mperature can adversely affect the
following char&&~t!cs: heat resistance and humidity resis- for more than 10 seconds.
tance whic~c~wwsult in device failure. Therefore the follow- .When shiting from preheating to soldering, the maximum
ing item,~+~h~Q,d’always be observed in order to minimize the temperature gradient shall be 5°C or less.
ther~,@~$~r,@sto which the devices are subjected. ●After soldering has been completed, the device should be
..
.~{;\,..2$::,,,.F;.. allowed to cool naturally for three minutes or more. Gradual
,q~,~~ti~yspreheat the device cooling should be used as the use of forced cooling will
$RI@&delta temperature between the preheat and soldering increase the temperature gradient and result in latent
1..,
should be 10O°C or less* mechanical stress.
.When preheating and soldering, the temperature of the .Mechanical stress or shock should not be applied during
leads and the case must not exceed the maximum temper- cooling.
ature ratings as shown on the data sheet. When using *Soldering adevice without preheating can cause excessivethermal
infrared heating with the reflow soldering method, the differ- shock and stress which can result in damage to the device.
PZTA63T1 ●PZTA63T3 MOTOROLA,
PZTA64T1 ●PZTA64T3 3