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SEMI G68-0996 © SEMI 1996, 2004 2 7 Interference 7.1 It is recomm ended that an operator who is familiar with the m easuring system and test m ethod conduct t he actual measurement in order to obtain the best result. 7.2…

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1 SEMI G68-0996 © SEMI 1996, 2004
SEMI G68-0996 (Reapproved 1104)
TEST METHOD FOR JUNCTION-TO-CASE THERMAL RESISTANCE
MEASUREMENTS IN AIR ENVIRONMENT FOR SEMICONDUCTOR
PACKAGES
This test method was technically approved by the Global Assembly & Packaging Committee and is the direct
responsibility of the Japanese Packaging Committee. Current edition approved by the Japanese Regional
Standards Committee on July 23, 2004. Initially available at www.semi.org September 2004; to be published
November 2004. Originally published in 1996.
1 Purpose
1.1 The purpose of this test is to determine the thermal
resistance of semiconductor packages using thermal test
chips. This test method deals with junction-to-case
measurements of thermal resistance in air environment.
2 Scope
2.1 The results of this test method are used to obtain
the junction temperature.
2.2 The measurement results are usually different from
the results obtained by testing in the fluid bath
environment described in SEMI G30 and SEMI G43.
2.3 This test method uses SI units.
NOTICE: This standard does not purport to address
safety issues, if any, associated with its use. It is the
responsibility of the users of this standard to establish
appropriate safety and health practices and determine
the applicability of regulatory or other limitations prior
to use.
3 Limitation
3.1 This method applies only to packages whose
surface is wide enough to place a thermocouple.
4 Referenced Standards
4.1 SEMI Standards
SEMI G30 — Test Method for Junction-to-Case
Thermal Resistance Measurements of Ceramic
Packages
SEMI G32 — Guideline for Unencapsulated Thermal
Test Chip
SEMI G38 — Test Method for Still- and Forced-Air
Junction-to-Ambient Thermal Resistance
Measurements of Integrated Circuit Packages
SEMI G42 — Specification for Thermal Test Board
Standardization for Measuring Junction-to-Ambient
Thermal Resistance of Semiconductor Packages
SEMI G43 — Test Method for Junction-to-Case
Thermal Resistance Measurements of Molded Plastic
Packages
NOTICE: Unless otherwise indicated, all documents
cited shall be the latest published versions.
5 Terminology
5.1 Definitions
5.1.1 The following definitions and symbols shall
apply to this test:
5.1.2 case top temperature measured in air
environment, T
t
— in °C, is the temperature at the
specified accessible reference point on the package in
measured in air environment.
NOTE 1: T
C
defined in SEMI G43 is different from T
t
.
5.1.3 junction temperature, T
j
— in °C, is the
temperature of the semiconductor junction on the
microcircuit in which the major part of the heat is
generated.
5.1.4 power dissipation P
H
— in watt, is the heating
power applied to the device causing a junction-to
reference point temperature difference.
5.1.5 thermal resistance measured in air environment,
junction to package surface,
jt
— in °C/watt, is the
temperature difference from the junction to the center
point on the package divided by the power dissipation
P
H
.
6 Summary of Method
6.1 A thermocouple is attached on the surface of the
package on the test board.
6.2 After the chip is heated, the junction temperature is
measured by the diode in the test chip. The surface
temperature is measured in an air environment by the
thermocouple.
6.3 The junction-to-case thermal resistance is
calculated using the case temperature, junction
temperature and power dissipation.
SEMI G68-0996 © SEMI 1996, 2004 2
7 Interference
7.1 It is recommended that an operator who is familiar
with the measuring system and test method conduct the
actual measurement in order to obtain the best result.
7.2 The procedure for attaching the thermocouple
described in Section 12.3 on the test package should be
followed in order to obtain the accurate measurement
result.
8 Apparatus
8.1 Thermocouple
8.1.1 Material — Copper-constantan or equivalent.
8.1.2 Temperature Range — -100 to +300°C.
8.1.3 Wire Size — No larger than AWG size 36.
8.1.4 The Junction — Shall be welded to form a bead
rather than soldered or twisted.
8.1.5 Accuracy — ± 0.5%.
8.2 Suitable Electrical Equipment — As required to
provide controlled levels of conditioning power and to
make the specified measurements.
8.2.1 Resolution — 50 µV and 5 µA.
8.3 Wind Tunnel (as necessary) — See SEMI G38 or
equivalent.
9 Materials
9.1 Test Chip — Referred to in SEMI G32, or
equivalent.
9.2 Test Board — Referred to in SEMI G42, or
equivalent.
9.3 Adhesive — Alpha Cyano-Acrylate.
 Aluminum Foil — 4 mm × 4 mm.
10 Setup
10.1 Warm up the test equipment before
measurements.
11 Calibration
11.1
Calibrate the equipment in accordance with the
operation manual as necessary.
12 Procedure
12.1 Preparation of Test Package
12.1.1 Prepare the semiconductor package in which the
test chip is mounted.
12.2 Assemble the package on the test board using
solder.
12.3 Attach the Thermocouple
12.3.1 Apply adhesive on the center point of the
package.
12.3.2 Place the thermocouple and aluminum foil on
the adhesive and press the aluminum foil using a finger
in order to attach the thermocouple on the package
surface as close as possible.
12.4 Measure the thermal characteristic of the diode of
the test chip.
NOTE 2: It is recommended that the ambient temperature T
a
is measured using the thermocouple.
12.5 Mount the test board in a test socket in a still-air
enclosure or wind tunnel as necessary.
12.6 Heating Chip
12.6.1 Supply power to the chip.
12.6.2 Adjust the measurement equipment to the
measured case temperature T
t
or the measured power
P
H
(package)
.
NOTE 3: The thermal resistance usually depends on the
power dissipation (see Figure 1). The thermal resistance is
variable within a power and stable beyond the power.
12.7 Wait until the thermal characteristic of the diode
is stable.
12.8 Calculate the junction temperature T
j
by the diode
thermal characteristics.
12.9 Measure the case temperature T
t
using the
thermocouple and record the case temperature.
12.10 Record the voltage and the current in order to
obtain the P
H
(package)
.
13 Calculation
13.1 The thermal resistance of the package can be
calculated as follows:
jt
(°C/watt) =
(T
j
— T
t
) / P
H
(package)
14 Report
14.1 The following details shall be reported:
a. Description of package.
b. Description of test board.
c. Power dissipation of test chip.
d. Thermal resistance R
jt
for test condition.
3 SEMI G68-0996 © SEMI 1996, 2004
Figure 1
Dependence of R
jt
on Power Dissipation
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representations as to the suitability of the standard set
forth herein for any particular application. The
determination of the suitability of the standard is solely
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respecting any materials or equipment mentioned
herein. These standards are subject to change without
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