MIL-STD-883E METHOD 1012.1

MIL-STD-883E

METHOD 1012.1

4 November 1980

1

METHOD 1012.1

THERMAL CHARACTERISTICS

1. PURPOSE. The purpose of this test is to determine the thermal characteristics of microelectronic devices. This includes

junction temperature, thermal resistance, case and mounting temperature and thermal response time of the microelectronic

devices.

c. Junction temperature, T

, in °C. The term is used to denote the temperature of the semiconductor junction in the

is the peak temperature of an operating junction element in which the current distribution is nonuniform, T

d. Thermal resistance, junction to specified reference point, R

, in °C/W. The thermal resistance of the microcircuit is

D

.

e. Power dissipation, P

D

, in seconds, is the time required to reach 90 percent of the final value of junction

g. Temperature sensitive parameter, TSP, is the temperature dependent electrical characteristic of the junction-under

2. APPARATUS. The apparatus required for these tests shall include the following as applicable to the specified test

MIL-STD-883E

METHOD 1012.1

4 November 1980

2

c. Suitable electrical equipment as required to provide controlled levels of conditioning power and to make the specified

d. Infrared microradiometer capable of measuring radiation in the 1 to 6 micrometer range and having the ability to detect

NOTE: May be a scanning IR microradiometer.

determined from a thermocouple peened into the underside of the adapter-near the package.

The adapter also contains the socket or other electrical interconnection scheme. In the case of the flat pack adapter heat sink,

the package is dropped into a special slotted printed circuit board (PCB) to register the leads with runs on the PCB; toggle

clamps then provide a pressure contact between the package leads and the PCB runs. Dual-in-line and axial lead packages plug

into a regular socket.

The thermal probe assembly is shown on figure 1012-1b. In practice, the pressure adjustment cap is adjusted so the disk at the

probe tip contacts the bottom surface of the package (chip carrier) with a predetermined force. A silicone grease (about 25-50

mm thick) is used at this interface to provide a reliable thermal contact.

3. PROCEDURE.

3.1 Direct measurement of reference point temperature, T

within the package by more than a few percent.

3.1.1 Case temperature, T

. The microelectronic device under test shall be mounted on a temperature controlled heat sink so

that the case temperature can be held at the specified value. A thermocouple shall be attached as near as possible to the center

of the bottom of the device case directly under the chip or substrate. A conducting epoxy may be used for this purpose. In

general, for ambient cooled devices, the case temperature should be measured at the spot with the highest temperature. The

thermocouple leads should be electrically insulated up to the welded thermocouple bead. The thermocouple bead should be in

direct mechanical contact with the case of the microelectronic device under test.

3.1.2 Mounting surface temperature, T

MIL-STD-883E

METHOD 1012.1

4 November 1980

3

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.

3.2.1 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

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

JR

. 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

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.