MIL- STD-883F 2004 TEST METHOD STANDARD MICROCIRCUITS - 第68页

MIL-STD-883F METHOD 1012.1 4 November 1980 4 The foll owing data s hall be rec orded for this test condit ion: a. Peak or average junct ion temper ature, T J(Peak) or T J(Avg) . b. Case or mounting s urfac e temperatur e…

MIL-STD-883F

METHOD 1012.1

4 November 1980

The thermocouple hole shall be drilled into the mounting base such that the thermocouple lead is directly below the area on

the case of interest. It is recommended that the thermocouple be secured into the mounting base with a thermal conducting

adhesive (or solder) and that particular attention be paid to minimizing air voids around the ball of the thermocouple. A

thermal conducting compound (or adhesive) should be used at the interface of the mounting base and the device under test.

3.2 Thermal resistance, junction to specified reference point, R

θJR

3.2.1 General considerations

. The thermal resistance of a semiconductor device is a measure of the ability of its carrier

or package and mounting technique to provide for heat removal from the semiconductor junction.

The thermal resistance of a microelectronic device can be calculated when the case temperature and power dissipation in

the device, and a measurement of the junction temperature are known. The junction with the greatest power dissipation

density (watts/mm

) shall be selected for measurement since that junction will generally have the highest temperature on the

chip. If the leads to that junction are not accessible and another junction is measured then it cannot be assured that the

highest temperature on the chip will be measured. Direct measurement should be used in this case.

When making the test measurements indicated below, the package shall be considered to have achieved thermal

equilibrium when the measured temperature difference, junction to case, reaches approximately 99 percent of its final value.

The temperature difference at that time will change at a rate less than

d(T

- T

) < 0.03 (T

- T

)

dt t

where t is the time after application of a power dissipation increment. The total time required for stabilization will typically be

less than a minute.

3.2.2 Direct measurement of junction temperature for determination of R

θJR

. The junction temperature of the thermally

limiting element within the semiconductor chip can be measured directly using an infrared microradiometer. The cap or lid

shall first be removed from the package to expose the active chip or device. The cavity shall not be covered with any IR

transparent material unless the chip is extremely large and has an extremely poor heat conduction path to the chip carrier.

The location of the junction to be measured should be referenced to a coordinate system on the chip so it can be relocated

after coating the chip. The active area of the chip shall be coated uniformly with a thin layer (25-50 µm thick) of a known

high emissivity (∈ > 0.8), low thermal conductivity material such as black pigmented lacquer. The package shall then be

placed on a temperature controlled heat sink and the case or mounting surface temperature stabilized at the specified value.

The microelectronic device under test shall then be operated at its rated power dissipation, the infrared microscope

crosshairs focused on the junction and scanned back and forth slightly at that location to maximize the radiance

measurement. That radiance measurement and the chip carrier temperature shall then be recorded. The power to the test

package shall then be turned off and the chip carrier allowed to return to the specified case or mounting surface

temperature. The emissivity of the coating over the junction region shall then be measured and the radiance from the

operating junction region shall be converted to temperature using this emissivity value. (Note that this method assumes the

emissivity of the coating material does not change appreciably with temperature. This assumption shall be valid if the

results are to be accurate and repeatable.)

If the junction to be measured is not specified then the test shall proceed as above except that the IR microscope crosshairs

shall be scanned over the whole active area of the chip to find and maximize the radiance measurement at the highest

temperature junction region.

The minimum width or length of the junction area shall be greater than 5 times the half power diameter of the objective lens

and greater than 5 times the thickness of the coating on the chip surface if this method is used to measure T

J(Peak)

. For

junction element diameters between 5 and 1 times the half power diameter of the IR microscope objective lens, some

average junction temperature T

J(Avg)

, where T

J(Region)

< T

J(Avg)

< T

J(Peak)

, will be measured.

MIL-STD-883F

METHOD 1012.1

4 November 1980

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

, T

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

3.2.3.1 Switching techniques for measuring T

J(Avg)

. The following symbols shall apply for the purpose of these

measurements:

- - - - - - - - - - - - - - - - Measuring current in milliamperes.

- - - - - - - - - - - - - - - Value of temperature-sensitive parameter in millivolts, measured at I

, and

corresponding to the temperature of the junction heated by P

- - - - - - - - - - - - - - - Calibration temperature in °C, measured at the reference point.

- - - - - - - - - - - - - - - Value of temperature-sensitive parameter in millivolts, measured at I

and specific

value of T

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

, 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

, for the particular measuring current and collector voltage used in the

test, is calculated from the calibration curve, V

versus T

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

under operating conditions with the measuring current, I

, and the collector voltage used during the calibration procedure.

The microelectronic device under test shall then be operated with heating power (P

) intermittently applied at greater than or

equal to 99 percent duty factor. The temperature- sensitive parameter V

shall be measured during the interval between

heating pulses (<

100 µs) with constant measuring current, I

, 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

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:

(t = 0) = V

MD1

+ V

MD2

- V

MD1

1/2

- t

1/2

Where:

(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,

MD1

= TSP, in millivolts, at time t = t

, and

MD2

= TSP, in millivolts, at time t = t

< t