CN101776727B - A method for measuring the working junction temperature and thermal resistance of electronic components in a vacuum environment - Google Patents

Abstract

The invention discloses a method for measuring working junction temperature and thermal resistance of an electronic component by utilizing a vacuum environment, which relates to the field of electronic component measurement, and comprises the following steps of: putting a measured component in a vacuum system, wherein the vacuum system is connected with external devices, and the external devices comprise an A/D acquisition board, a computer, a power supply and a heating power supply; placing a temperature-sensitive resistor A near the heat source source, which is the active area of the measured component; enabling a temperature-sensitive resistor B to contact with one surface of a heating sheet and the other surface of the heating sheet to contact with the bottom which is the heat dissipation endpoint of the measured component; acquiring the time t1 required for establishing the temperature gradient from the active area to the heat dissipation endpoint; and acquiring the time t2 acquired for establishing the temperature gradient from the heat dissipation endpoint to the active area; the power applied to the measured component is P, and the making time is t1+t2; when the temperature-sensitive resistors A and B tends to a steady state value, the temperature is the temperature of the measured component in normal work, and the working temperature rise and the thermal resistance of the measured component can be obtained. The method has no demand on the packaging forms semiconductor devices or function modules and belongs to a non-destructive test.

Description

A method for measuring the working junction temperature and thermal resistance of electronic components in a vacuum environment

technical field

The invention relates to the production measurement of electronic devices, as well as the fields of research and development.

Background technique

When electronic components or functional modules are working, the heat concentration in the active area and the temperature rise are the key factors affecting their characteristics, reliability and life. Due to the small area of the active region, it is difficult to measure its operating temperature. Commonly used methods include infrared temperature measurement, electrical parameter method, liquid crystal display and luminescent spectrum shift method, etc. Infrared temperature measurement method and liquid crystal display method can measure the temperature distribution on the surface of the chip, which may cause damage to the packaging of the device. The luminescence spectrum shift method measures temperature, and the device under test must have luminescence characteristics, which is not suitable for microelectronic devices that do not emit light. The electrical parameter method can conveniently and quickly measure the temperature rise in the active area of the device, but for most devices, the temperature-sensitive parameters that can be extracted are very limited, and some devices must be equipped with expensive special test circuits and equipment.

This method utilizes under the vacuum adiabatic environment, by collecting the temperature rising curve (positive direction) of the two ends on the heat dissipation path when the electronic components or functional modules are working normally, and collecting and measuring the temperature of the two ends again after the heat dissipation end of the device is heated by equal power. The temperature rise curve (reverse) respectively obtains the heating time required for the device to reach a stable temperature distribution under the condition of applying equal power heating in the forward and reverse directions of the device, that is, respectively obtains the heating heat during the establishment of the steady-state operating temperature gradient of the device. From this, the temperature of the electronic components under normal working conditions can be measured.

The technology can be widely applied to electronic components and functional modules in any packaging form, the measurement method is simple and accurate, and it is suitable for the production measurement of electronic devices, as well as the research and development fields.

Contents of the invention

The main purpose of the present invention is: the temperature rise of the active area is an important parameter to determine the service life and reliability of the electronic components when they work normally. The invention provides a method for measuring the working temperature rise of semiconductor devices by accurately measuring the heat required for the process of establishing a steady-state temperature gradient in a vacuum environment.

The working principle of the present invention

Electronic components usually consist of a die, heat sink, solder and case. In the atmospheric environment, heat is generated by the active area of the device, flows through the heat sink, and dissipates to the surrounding environment. When the heat generated in the active area is equal to the dissipated heat, after a period of time, the temperature distribution on the device reaches a stable state, forming a temperature distribution from the heat source to the shell from high to low. After the device power is turned on, the schematic diagram of the transient process of temperature rise in the active area is shown in Figure 1. Curves 1 and 2 in the figure are respectively the temperature transient rise curves when the electronic components work normally and when the heat source is located at the bottom of the heat sink of the device. Since the thermal resistance between the two terminals of the semiconductor device is constant, the temperature rise to reach a steady state is constant, but the time required is different.

When the electronic components are put into a vacuum system, the heat generated in the active area can only be transferred to the shell through heat conduction due to the interruption of the surrounding heat dissipation path. At this time, the temperature of the active region continues to rise, and the temperature gradient increases. When the heat is conducted to the end of the package shell, the heat no longer has a path to dissipate, the temperature difference between the active area and the end of the shell remains constant, and the overall temperature rises rapidly (when the device temperature is not too high, the radiation can be ignored heat dissipation). If the temperature-measuring temperature-sensitive element is placed in two different positions of the device (one of which is the end of heat dissipation), the temperature rise process at two points is shown in curves 1 and 2 in schematic diagram 2.

When the temperature difference between these two points becomes constant, it is the moment when the temperature gradient from the heat source to the shell is established. Curve 3 in Figure 2 is the measurement curve of the temperature difference between two points. When the components work normally, the active area is the heat source, and the process of establishing a temperature gradient from the active area to the shell is called the forward heating process. The time t1 at which the temperature difference curve begins to be constant is the time required for the establishment of a steady-state temperature rise. The working power P is multiplied by t1, that is, the heat Q1=P*t1 required to establish this temperature gradient.

When the same electric power P is applied to the bottom of the package case by heating the sheet, the bottom is the heating end and the top is the heat dissipation end. Measure the temperature rise process of the two detection points after the power is turned on. When the temperature difference between the two points reaches a constant time t2, the temperature gradient from the bottom of the package to the active area is established. We call this process the reverse heating process. Due to the reciprocity of the thermal resistance at both ends of the device, the temperature difference during the two temperature rises is equal. Generally, the heat capacity at the active region side of the device die is small and the heat capacity at the case side is large. Therefore, the heating power required to achieve the same temperature difference is different, that is, t2>t1, Q2=P*t2, and the required heat is established for the second temperature gradient.

In the forward heating process and the reverse heating process, the temperature spatial distribution from high temperature to low temperature presents a complementary state. That is, after the temperature reaches a steady-state distribution, the temperature spatial distribution curves on the heat dissipation path from the heat source to the substrate appear complementary. See schematic 3. Physically, the area formed by the curve and the position coordinates represents the amount of heat required to establish a steady state distribution. The amount of heat required for forward heating and reverse heating is different, but the sum of the two is the amount of heat required to uniformly reach the temperature of the active region as a whole.

The temperature gradient formed by the forward and reverse heating processes is the same, that is, the thermal resistance is the same. Add the heat required for the establishment of the positive and negative temperature gradients, that is, P*(t1+t2), and inject it into the device. In a vacuum environment, there is no heat loss, and the temperature after the entire system reaches a uniform balance is the normal operation of the device. temperature at the time.

Technical scheme of the present invention is described as follows:

(1) Device under test 2 is placed in a vacuum system 1, and this vacuum system leaves terminal to be connected with external device; External device comprises A/D acquisition board 6, computer 7, power supply 8 and heating power supply 9;

(2) The device under test 2 is connected to the power supply 8 through the terminal post in the vacuum system;

(3) Place a temperature-sensitive resistor A3 near the heat source part of the device under test 2, that is, the active area, and the temperature-sensitive resistor A3 is connected with the A/D acquisition board 6 through a binding post;

(4) Select a heating sheet 4 with known thermal resistance and controllable heating power, and the heating sheet 4 is connected to the heating power supply 9 through the binding post;

(5) Connect another temperature-sensitive resistor B5 to the A/D acquisition board 6 through a binding post, and contact the temperature-sensitive resistor B5 with one side of the heating sheet 4, and the other side of the heating sheet 4 is connected to the bottom of the device under test 2, that is, the heat dissipation terminal touch;

(6) Computer 7 controls power supply 8, A/D acquisition board 6, heating power supply 9; The resistor acquires the temperature on the device under test;

(7) When the power supply 8 is turned on, the A/D acquisition board is triggered to measure and record the temperature-sensitive resistor A3 and the temperature-sensitive resistor B5 over time. The time t1 required for the temperature gradient from the source region to the heat sink end point;

(8) By inflating the vacuum system, etc., so that the temperature of the device under test does not change, and then heat the sheet 4 through the heating power supply 9, and trigger the A/D acquisition board 6 at the same time, measure and record the temperature-sensitive resistor A3 and the temperature-sensitive resistor In the process of B5 changing with time, by finding the difference between the measured values of the two temperature-sensitive resistors for a constant time t2, it is the time required to establish the temperature gradient from the heat dissipation endpoint to the active area;

(9) Make the temperature of the device under test no longer change by inflating the vacuum system, etc., turn on the power supply of the device under test, apply the power to P, and turn on the time for t1+t2, turn off the power supply, when the temperature sensitive resistor A3 and The temperature-sensitive resistor B5 tends to a constant value, which is the temperature of the device under test when it is working normally. Subtracting the temperature of the device under test before power is added, the operating temperature rise of the device under test can be obtained; due to the thermal resistance of the heating sheet And the heating power is known, subtract the thermal resistance of the heating sheet, that is, the thermal resistance of the actual device under test.

When the time for the device under test to establish a stable temperature gradient is too short, the duty cycle of the applied power can be reduced to reduce the heat that causes the device under test to heat up, so that the time of t1 and t2 can be lengthened to reduce the measurement error;

This method has no requirements on the packaging form of semiconductor devices or functional modules, and is a non-destructive test. Especially for some devices or functional modules that cannot be measured by conventional measuring junction temperature technology, this method can show its applicability and advancedness.

Description of drawings

Figure 1. Schematic diagram of the transient process of temperature rise of electronic components in an atmospheric environment

Figure 2. Schematic diagram of the transient process of temperature rise in a vacuum environment

Figure 3. During the forward and reverse heating process, the complementary temperature distribution state of the device formation

1: The internal temperature rise distribution formed when the device is heated forward (the ambient temperature is 300K)

2: The internal temperature rise distribution formed when the device is heated in reverse (the ambient temperature is 300K)

3: Sum of two curves

Figure 4 Schematic diagram of test structure

1: Vacuum system 2: Device under test 3: Temperature sensitive resistor A 4: Heating sheet 5: Temperature sensitive resistor B; 6: A/D acquisition board 7: Computer 8: Power supply 9: Heating power supply

Figure 5 Example of positive heating time measurement

Figure 6 embodiment reverse heating time measurement

Detailed ways

1. Use a vacuum system 1 that is connected to an external measuring device via internally sealed terminals. The device under test is power VDMOS, normal working voltage V=3.5V, I=1.2A, working power p=V*I=4.2W, working power is controlled by computer;

2. Select two temperature-sensitive resistors. In this embodiment, two 100-ohm platinum resistors are used. One is placed on the upper part of the shell, and the other is placed on the bottom of the heating film. The other end of the film is in contact with the bottom of the shell. The two platinum resistors are connected to the external 1mA current source through the internal terminal. The voltages at both ends of the resistors are respectively connected to the high-speed acquisition board. The heating power of the heating film is connected to the external power supply. When the heating power is applied, the high-speed acquisition board is triggered to collect temperature sensitive data. The voltage across the resistor, that is, the change in temperature with heating time;

3. The acquisition of temperature-sensitive resistor voltage (temperature) changes with time uses a high-speed acquisition board. In order to ensure the measurement accuracy, a 1M sampling rate, 12-bit, dual-channel AC1050 acquisition board is used in this embodiment. The shortest time interval can reach 1 microsecond. In this embodiment, the time interval of collection is 2ms, and the measured data can be saved at any time;

4. Vacuum the test vacuum system to make the vacuum degree reach 1.6×10 ^-3 Pascals. During the measurement, the computer sends instructions to the program-controlled power supply to add power to the VDMOS of the device under test, and at the same time trigger the high-speed acquisition board to measure the change of the temperature-sensitive resistance with time curve, that is, the temperature rise curve. The measurement results are shown in Figure 5;

5. Make a difference to the measured curve, and the moment when the difference reaches a constant value is t1=4 seconds. That is, when heating in the forward direction, the steady-state temperature gradient establishes time t1, and the heating heat Q=P*t1=16.8 joules.

6. Use a ceramic heating sheet with a heating resistor to heat, and at the same time trigger the high-speed acquisition board to measure and record the time-varying process of thermistors 3 and 5, that is, the temperature rise curve during reverse heating. The measurement results are shown in Figure 6;

7. Make a difference to the measured curve, and the time when the difference reaches a constant value is t2=7s, that is, when reverse heating, the steady-state temperature gradient builds up time t2, and the heating heat Q=P*t2=29.4 joules.

8. Add power to the device under test. The power duration is t1+t2. After removing the power, trigger the A/D acquisition board to measure and record the change process of the temperature-sensitive resistor 3 terminal voltage with time. When the voltage no longer changes, the corresponding The temperature of the device is the working junction temperature when the device is working normally in the atmosphere. In this example, the working junction temperature of the device is 9.2K. In this example, the thermal resistance of the heating film is 0.5K/W, so the 2.1 introduced by the heating film is subtracted. K temperature rise, the thermal resistance of the device is (9.2K-2.1K)/4.2W=1.7K/W.

Claims (1)

1. a method of utilizing vacuum environment to measure electronic devices and components working junction temperature and thermal resistance is characterized in that, may further comprise the steps:

(1) measured device is placed a vacuum system, this vacuum system leaves binding post and links to each other with external device (ED); External device (ED) comprises A/D collection plate, computing machine, power supply and heating power supply;

(2) measured device is connected with power supply by binding post in the vacuum system;

(3) partly be that a thermo-sensitive resistor A is placed at the active area place at the thermal source near measured device, thermo-sensitive resistor A is connected with the A/D collection plate by binding post;

(4) select a thermal resistance known, the heating sheet that heating power is controlled, heating sheet is connected with heating power supply by binding post;

(5) another thermo-sensitive resistor B is connected with the A/D collection plate by binding post, and thermo-sensitive resistor B is simultaneously contacted with heating sheet, heating sheet another side and the bottom of the measured device end points that promptly dispels the heat contacts;

(6) computer control power supply, A/D collection plate, heating power supply; The A/D collection plate is gathered thermo-sensitive resistor position temperature over time, and measurement data is preserved, apply electric power at every turn before, obtain temperature on the measured device by thermo-sensitive resistor;

(7) work as energized, trigger simultaneously that the A/D collection plate is measured and record thermo-sensitive resistor A and thermo-sensitive resistor B change procedure in time, the difference by two thermo-sensitive resistor measured values becomes when constant, obtains and establishes the thermograde required time t1 of source region to the heat radiation end points;

(8) no longer change when the measured device temperature, again by the heating heating sheet, trigger the A/D collection plate simultaneously, measure and write down thermo-sensitive resistor A and thermo-sensitive resistor B change procedure in time, by the constant time t2 of difference that asks two thermo-sensitive resistor measured values, be and set up the thermograde required time of heat radiation end points to active area;

(9) no longer change when the measured device temperature, connect the measured device power supply, applying power is P, and be t1+t2 turn-on time, power cutoff, measure and write down thermo-sensitive resistor A terminal voltage change procedure in time, when voltage no longer changed, corresponding temperature was exactly measured device working junction temperature during operate as normal under atmosphere, this temperature be tested during temperature during operate as normal, deduct and add measured device temperature before the power, promptly obtain being measured the work temperature rise of device; Because the thermal resistance and the heating power of heating sheet are known, deduct the heating sheet thermal resistance, promptly get the thermal resistance of actual measured device.

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