MIL- STD-883F 2004 TEST METHOD STANDARD MICROCIRCUITS - 第69页

MIL-STD-883F METHOD 1012.1 4 November 1980 5 3.2.3. 1 Switc hing techni ques for measur ing T J(Avg) . The fol lowing s ymbols s hall apply f or the pur pose of t hese measurement s: I M - - - - - - - - - - - - - - - - M…

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MIL-STD-883F
METHOD 1012.1
4 November 1980
4
The following data shall be recorded for this test condition:
a. Peak or average junction temperature, T
J(Peak)
or T
J(Avg)
.
b. Case or mounting surface temperature (usually 60°C ±0.5°C T
C
, T
M
).
c. Power dissipation, P
D(Package)
, in the package.
d. Reference temperature measuring point.
e. Mounting arrangement.
f. Half power "spot" size of the IR microscope.
g. Thickness of the emissivity control coating (for T
J(Avg)
measurements only).
h. Minimum width or length of the junction measured (for T
J(Avg)
measurements only).
3.2.3 Indirect measurements of junction temperature for the determination of R
θJR
. The purpose of the test is to measure
the thermal resistance of integrated circuits by using particular semiconductor elements on the chip to indicate the device
junction temperature.
In order to obtain a realistic estimate of the operating average junction temperature, T
J(Avg)
, the whole chip or chips in the
package should be powered in order to provide the proper internal temperature distribution. For other purposes though (see
section 3.2.1), the junction element being sensed need only be powered. During measurement of the junction temperature
the chip heating current shall be switched off while the junction calibration current remains stable. It is assumed that the
calibration current will not affect the circuit operation; if so, then the calibration current must be switched on as the power is
switched off.
The temperature sensitive device parameter is used as an indicator of an average junction temperature of the
semiconductor element for calculations of thermal resistance. The measured junction temperature is indicative of the
temperature only in the immediate vicinity of the element used to sense the temperature. Thus, if the junction element being
sensed is also dissipating power with a uniform heating current distribution, then T
J(Avg)
≈ T
J(Peak)
for that particular junction
element. If the current distribution is not uniform then T
J(Avg )
is measured. If the junction element being sensed is in the
immediate vicinity of the element dissipating power then T
J(Region)
will be measured. The heating power does not have to be
switched off when T
J(Region)
is measured.
The temperature sensitive electrical parameters generally used to indirectly measure the junction temperature are the
forward voltage of diodes, and the emitter-base and the collector-base voltages of bipolar transistors. Other appropriate
temperature sensitive parameters may be used for indirectly measuring junction temperature for fabrication technologies
that do not lend themselves to sensing the active junction voltages. For example, the substrate diode(s) in junction-isolated
monolithic integrated circuits can be used as the temperature sensitive parameter for measurements of T
J(Region)
. In this
particular case though, the heating power has to be switched off at the same time that the substrate diode is forward biased.
MIL-STD-883F
METHOD 1012.1
4 November 1980
5
3.2.3.1 Switching techniques for measuring T
J(Avg)
. The following symbols shall apply for the purpose of these
measurements:
I
M
- - - - - - - - - - - - - - - - Measuring current in milliamperes.
V
MD
- - - - - - - - - - - - - - - Value of temperature-sensitive parameter in millivolts, measured at I
M
, and
corresponding to the temperature of the junction heated by P
D
.
T
MC
- - - - - - - - - - - - - - - Calibration temperature in °C, measured at the reference point.
V
MC
- - - - - - - - - - - - - - - Value of temperature-sensitive parameter in millivolts, measured at I
M
and specific
value of T
MC
.
The measurement of T
J(Avg)
using junction forward voltage as the TSP is made in the following manner:
Step 1 - Measurement of the temperature coefficient of the TSP (calibration)
.
The coefficient of the temperature sensitive parameter is generated by measuring the TSP as a function of the reference
point temperature, for a specified constant measuring current, I
M
, and collector voltage, by externally heating the device
under test in an oven or on a temperature controlled heat sink. The reference point temperature range used during
calibration shall encompass the temperature range encountered in the power application test (see step 2). The measuring
current is generally chosen such that the TSP decreases linearly with increasing temperature over the range of interest and
that negligible internal heating occurs during the measuring interval. A measuring current ranging from 0.05 to 5 mA is
generally used, depending on the rating and operating conditions of the device under test, for measuring the TSP. The
value of the TSP temperature coefficient, V
MC
/T
MC
, for the particular measuring current and collector voltage used in the
test, is calculated from the calibration curve, V
MC
versus T
MC
.
Step 2 - Power application test
.
The power application test is performed in two parts. For both portions of the test, the reference point temperature is held
constant at a preset value. The first measurement to be made is that of the temperature sensitive parameter, i.e., V
MC
,
under operating conditions with the measuring current, I
M
, and the collector voltage used during the calibration procedure.
The microelectronic device under test shall then be operated with heating power (P
D
) intermittently applied at greater than or
equal to 99 percent duty factor. The temperature- sensitive parameter V
MD
shall be measured during the interval between
heating pulses (<
100 µs) with constant measuring current, I
M
, and the collector voltage that was applied during the
calibration procedure (see step 1).
Because some semiconductor element cooling occurs between the time that the heating power is removed and the time that
the temperature-sensitive parameter is measured, V
MD
may have to be extrapolated back to the time where the heating
power was terminated by using the following mathematical expression which is valid for the first 100 µs of cooling:
V
MD
(t = 0) = V
MD1
+ V
MD2
- V
MD1
t
1
1/2
t
1
1/2
- t
2
1/2
Where:
V
MD
(t = 0) = TSP, in millivolts, extrapolated to the time at which
the heating power is terminated,
t = Delay time, in microseconds, after heating power is terminated,
V
MD1
= TSP, in millivolts, at time t = t
1
, and
V
MD2
= TSP, in millivolts, at time t = t
2
< t
1
.
MIL-STD-883F
METHOD 1012.1
4 November 1980
6
If V
MD
(t) versus t
1/2
is plotted on linear graph paper for the first 100 µs of cooling, the generated curve will be a straight line
except during the initial portion where nonthermal switching transients dominate. The time t
2
is the minimum time at which
the TSP can be measured as determined from the linear portion of the V
MD
(t) versus t
1/2
cooling curve. Time t
1
should be at
least equal to t
2
+ 25 µs but less than 100 µs. The delay time before the TSP can be measured ranges from 1 to 50 µs for
most microelectronic devices. This extrapolation procedure is valid for semiconductor (junction) sensing elements >
0.2 mm
(8 mils) in diameter over the delay time range of interest (1 to 50 µs).
When the error in the calculated thermal resistance caused by using V
MD2
instead of the extrapolated value V
MD
(t = 0)
exceeds 5 percent, the extrapolated value of V
MD
shall be used for calculating the average junction temperature.
The heating power, P
D
, shall be chosen such that the calculated junction-to- reference point temperature difference as
measured at V
MD2
is greater than or equal to 20°C. The values of V
MD
, V
MC
, and P
D
are recorded during the power
application test.
The following data shall be recorded for these test conditions:
a. Temperature sensitive electrical parameters (V
F
, V
EB
(emitter-only switching), V
EB
(emitter and collector
switching), V
CB
, V
F(subst)
, or other appropriate TSP).
b. Average junction temperature, T
J(Avg)
, is calculated from the equation:
∆V
MC
- 1
T
J(AVG)
= T
R
+ (V
MD
- V
MC
),
∆T
MC
where: T
R
= T
C
or T
M
c. Case or mounting surface temperature, T
C
or T
M
, (usually 60° ±0.5°C).
d. Power dissipation, P
D
where P
D
= P
D(Package)
or P
D(Element)
.
e. Mounting arrangement.
3.2.3.2 Typical test circuits for indirect measurements of T
J(Avg)
. The circuit on figure 1012-3 can be used to sense V
F
,
V
EB
(emitter-only switches), V
EB
(emitter and collector switching), and V
CB
. The circuit is configured for heating power to be
applied only to the junction element being sensed P
D(Element)
for illustration purposes only.
The circuit on figure 1012-3 is controlled by a clock pulse with a pulse width less than or equal to 100 µs and repetition rate
less than or equal to 66.7 Hz. When the voltage level of the clock pulse is zero, the transistor Q1 is off and transistor Q2 is
on, and the emitter current through the device under test (DUT) is the sum of the constant heating current and the constant
measuring current. Biasing transistor Q1 on, shunts the heating current to ground and effectively reverse biases the diode
D1. The sample-and-hold unit is triggered when the heating current is removed and is used to monitor the TSP of the device
under test. During calibration, switch S4 is open.
The circuit on figure 1012-4 can be used to sense the forward voltage of the substrate diode of a junction isolated integrated
circuit. In this test circuit the microelectronic device under test is represented by a single transistor operated in a
common-emitter configuration. The substrate diode D
SUBST
is shown connected between the collector (most positive
terminal) and the emitter (most negative terminal) of the integrated circuit under test. The type of circuitry needed to
interrupt the heating power will depend on the complexity of the integrated circuit being tested.
The circuit on figure 1012-4 is controlled by a clock pulse with a pulse width less than or equal to 100 µs and repetition rate
less than or equal to 66.7 Hz. When the voltage level of the clock pulse is zero, transistor Q1 being off and transistor Q2 on,
the device under test is dissipating heating power. Biasing transistor Q1 on and Q2 off, interrupts the heating power and
forward biases the substrate diode. The sample-and-hold unit is triggered when the heating current is removed and is used
to monitor the substrate diode forward voltage. During calibration, switch S1 is open.