Motorola Small–Signal Transistors, FETs and Diodes Device Data
BAV74LT1
INFORMATION FOR USING THE SOT–23 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.
0.037
0.95
0.037
0.95
0.079
2.0
0.035
0.9
0.031
0.8
inches
mm
SOT–23
SOT–23 POWER DISSIPATION
The power dissipation of the SOT–23 is a function of the
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, R
θJA
, 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–23 package,
PD can be calculated as follows:
PD =
TJ(max) – TA
R
θJA
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.
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 225 milliwatts.
PD =
150°C – 25°C
556°C/W
= 225 milliwatts
The 556°C/W for the SOT–23 package assumes the use
of the recommended footprint on a glass epoxy printed circuit
board to achieve a power dissipation of 225 milliwatts. There
are other alternatives to achieving higher power dissipation
from the SOT–23 package. 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.
Motorola Small–Signal Transistors, FETs and Diodes Device Data
3
BAV74LT1
PACKAGE DIMENSIONS
A
L
3
B S
1
2
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH.
3. MAXIMUM LEAD THICKNESS INCLUDES LEAD
FINISH THICKNESS. MINIMUM LEAD THICKNESS
IS THE MINIMUM THICKNESS OF BASE
MATERIAL.
INCHES
MIN
MAX
0.1102 0.1197
0.0472 0.0551
0.0350 0.0440
0.0150 0.0200
0.0701 0.0807
0.0005 0.0040
0.0034 0.0070
0.0180 0.0236
0.0350 0.0401
0.0830 0.0984
0.0177 0.0236
MILLIMETERS
MIN
MAX
2.80
3.04
1.20
1.40
0.89
1.11
0.37
0.50
1.78
2.04
0.013
0.100
0.085
0.177
0.45
0.60
0.89
1.02
2.10
2.50
0.45
0.60
V
G
C
D
H
K
J
DIM
A
B
C
D
G
H
J
K
L
S
V
CASE 318–08
ISSUE AE
SOT–23 (TO–236AB)
STYLE 9:
PIN 1. ANODE
2. ANODE
3. CATHODE
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the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit, and
specifically disclaims any and all liability, including without limitation consequential or incidental damages. “Typical” parameters which may be provided in Motorola
data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals”
must be validated for each customer application by customer’s technical experts. Motorola does not convey any license under its patent rights nor the rights of
others. Motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other
applications intended to support or sustain life, or for any other application in which the failure of the Motorola product could create a situation where personal injury
or death may occur. Should Buyer purchase or use Motorola products for any such unintended or unauthorized application, Buyer shall indemnify and hold Motorola
and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees
arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that
Motorola was negligent regarding the design or manufacture of the part. Motorola and
are registered trademarks of Motorola, Inc. Motorola, Inc. is an Equal
Opportunity/Affirmative Action Employer.
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