CN103323793A - A LED light source accelerated life testing system and method - Google Patents

Abstract

The invention relates to an LED light source service life accelerated test system and a method, wherein the system comprises a sample grouping device, a first junction temperature test device, a heating device, a second junction temperature test device, a service life measuring and calculating device and a heating test device. The invention accelerates the failure to find the potential defects by improving the working temperature stress of the driving power supply under the condition of keeping the failure mechanism of the driving power supply unchanged, deduces the service life of the driving power supply under the normal temperature stress level according to an accelerated service life test model in the attritor acceleration theory and the introduced confidence coefficient, and leads the product to be mature on the design and process at a much higher speed than the traditional design and test, thereby shortening the total time of the development process, putting the product on the market early, seizing the market share, realizing the rapid maturation of the product design and process and lowering the product development and production cost.

Description

A LED light source accelerated life testing system and method

technical field

The present invention relates to a system and method for accelerated life testing, more specifically, to a system and method for accelerated life testing of LED light sources.

Background technique

With the rapid development of science and technology, lighting electricity accounts for an increasing proportion of the total electricity consumption of the society. Improving lighting efficiency and saving energy have become important means to alleviate the shortage of electricity. Semiconductor LEDs are known as "green energy" and are also As one of the green and environmentally friendly energy sources, it is not only energy-saving and environmentally friendly, but also has the advantages of long life and high luminous efficiency. Of course, LED is also widely concerned in various industries, so the life of LED is of course an important indicator to measure its quality, but the traditional LED The light source life test method is to do a long-term life test under normal use until the LED is damaged or the luminous flux is seriously attenuated below 50%. The life of a normal LED can reach tens of thousands of hours. This test is inefficient and increases the product development cycle. And waste a lot of manpower and material resources.

Contents of the invention

The technical problem to be solved by the present invention is to provide a LED light source accelerated life testing system and method for the above defects of the prior art.

The technical solution adopted by the present invention to solve the technical problem is: to construct a LED light source accelerated life testing system, including

A sample grouping device, which is used to equally divide N samples into multiple groups, and set one of the multiple groups as a routine group, and the remaining groups as a control group;

The first junction temperature testing device is used to test the junction temperature of the conventional group of samples at normal temperature;

A heating device, used to heat each of the control groups;

The second junction temperature testing device is used to test the junction temperature of each control group sample in a heated state;

A life-span calculation device, used to calculate the confidence level and the LED life-span of each control group under heating conditions;

The heating test device obtains the lifespan of the LED light source at normal temperature based on the confidence calculated by the measuring and calculating device and the LED lifespan of each control group in a heated state.

In the LED light source accelerated life testing system of the present invention, the heating temperature of each of the control groups by the heating device is lower than the junction temperature of the conventional group of samples at normal temperature.

The LED light source accelerated life testing system according to the present invention, wherein, the life measuring device includes

Confidence measurement module, used to calculate confidence;

The life-span calculation module is used to calculate the LED life-span of each control group under the heating state.

In the LED light source accelerated life testing system of the present invention, the number N of samples is greater than or equal to 15.

Another technical solution adopted by the present invention to solve the technical problem is to propose a method for testing the accelerated life of an LED light source, which includes the following steps:

S100. Divide the N samples into multiple groups, and set one of the multiple groups as a routine group, and the remaining groups as a control group;

S200. Test the junction temperature of the conventional group samples at normal temperature;

S300, warming each of the control groups respectively;

S400. Test the junction temperature of each control group sample in a heated state

S500, calculating the confidence level, and the lifespan value of each control group under the heating state;

S600. Obtain the lifetime of the LED light source at normal temperature based on the confidence and the lifetime values of each of the control groups in a heated state.

In the accelerated life testing method of the LED light source of the present invention, the heating temperature of each of the control groups is lower than the junction temperature of the conventional group of samples at normal temperature.

The LED light source accelerated life testing method of the present invention, wherein, the junction temperature of the conventional group of samples at room temperature satisfies:

T _j =T _c +W×R _jc +273,

Where T _c is the temperature of the LED light source at room temperature, R _jc is the thermal resistance coefficient of the LED light source, W = conduction voltage × operating current.

The LED light source accelerated life test method according to the present invention, wherein, the junction temperature of the control group sample in the heated state satisfies:

T _D =T _CD +W×R _jc +273,

Wherein, T _CD is the temperature of the LED light source of the control group in the heated state, R _jc is the thermal resistance coefficient of the LED light source, W=conducting voltage×operating current.

The LED light source accelerated life test method of the present invention, wherein, the life value of each control group under the heating state satisfies

${\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; mou</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; In</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; In</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; )</span>}$

Wherein, P _t =P ₀ ×0.7, P ₀ is the initial luminous flux of the control group, and t is the power-on working time of the control group at this temperature point.

The LED light source accelerated life testing method of the present invention, wherein, the number of samples N is 15, 5 of which are set as the conventional group, and the remaining 10 are equally divided into two groups and set as the control group, then the confidence

${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; In</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; mou</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; mou</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}}$

The life value of the LED light source at room temperature

${\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span>\frac{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}{\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 25</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ]</span>$

in, T _mou1 and T _mou2 are the junction temperatures of the two control groups in the heated state, respectively, and T _j is the junction temperature of the conventional group samples at normal temperature.

Implementing the LED light source accelerated life testing system and method of the present invention has the following beneficial effects: under the condition that the failure mechanism of the driving power supply remains unchanged, the method accelerates the failure to find its potential defects by increasing its working temperature stress, and According to the accelerated life test model in the Alfred acceleration theory and the introduction of confidence, it is inferred that its life under normal temperature stress level is much faster than the traditional design and test to make the product mature in design and process, thus shortening the life of the product. The total time of the development process can be put on the market as soon as possible, and the market share can be seized. The product design and process mature quickly, and the product development and production costs are lower.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

Fig. 1 is a flow chart of an accelerated life testing method for an LED light source according to the present invention.

Detailed ways

In a preferred embodiment of the present invention, the LED light source accelerated life testing system includes a sample grouping device, a first junction temperature testing device, a heating device, a second junction temperature testing device, a measuring device and a heating testing device.

The sample grouping device divides the N samples into multiple groups, and sets one of the multiple groups as a routine group, and the rest of the groups as a control group. The distinction between the routine group and the control group can be achieved using some conventional methods, such as marking. The samples described in this embodiment are LED light sources.

The first junction temperature testing device is used to test the junction temperature of the conventional group of samples, which is achieved by heating the aluminum substrate of the sample with a thermocouple, where the junction temperature refers to the actual semiconductor chip (wafer, bare chip) in the electronic device The maximum temperature, which is usually higher than the case temperature and device surface temperature. The purpose of testing the junction temperature of the conventional group of samples is to select the test temperature for the next accelerated test, and the test temperature should not be higher than the junction temperature of the sample at normal temperature.

The heating device heats the samples of each control group, so that the samples of each control group work at a temperature higher than normal temperature for a certain period of time.

The second junction temperature testing device is used to test the junction temperature of each control group sample in a heated state;

The calculation device calculates the lifespan of the LEDs of each control group in the heating state, and then calculates the value of the confidence level according to the LED lifespan value of the samples of each control group in the heating state, and the confidence level is also called activation energy.

The heating test device further obtains the lifespan of the LED light source at normal temperature based on the confidence calculated by the above-mentioned measuring device and the LED lifespan of each control group sample in a heated state.

It is worth noting that the temperature at which the above-mentioned heating device heats the samples of each control group is higher than normal temperature and at the same time lower than the junction temperature of the samples of the conventional group at normal temperature.

Preferably, the above calculation device may further include a life calculation module for calculating the LED life of each control group sample in a heated state, and a confidence calculation module for calculating the confidence. And in order to improve the accuracy of the test and further reduce the test time, the number N of the above test samples should be greater than or equal to 15.

In another preferred embodiment of the present invention: a LED light source accelerated life testing method is constructed, comprising the following steps:

S100. Divide the N samples into multiple groups, and set one of the multiple groups as a conventional group, and the remaining groups as a control group. In this embodiment, the samples are LED light sources;

S200. Test the junction temperature of the conventional group samples at normal temperature;

S300, respectively heating the samples of the control group;

S400, testing the junction temperature of each control group sample in a heated state;

S500, calculation confidence, and life values of each control group sample under heating state;

S600. Obtain the lifetime of the LED light source at normal temperature based on the confidence and the lifetime values of each of the control samples in a heated state.

It is worth noting that the heating temperatures of the above-mentioned control group samples are all lower than the junction temperature of the conventional group samples at room temperature. And the junction temperature of the conventional group of samples at room temperature satisfies: T _j =T _c +W×R _jc +273, where T _c is the temperature of the LED light source at room temperature, and R _jc is the thermal resistance coefficient of the LED light source, which is usually determined by the LED Provided by the manufacturer of the light source, W = conduction voltage × operating current.

In addition, the LED light source accelerated life test method also includes the step of testing the initial luminous flux of each control group sample. According to the measured initial luminous flux, the following formula can be used to obtain the lifetime value of each control group in the heating state satisfying

${\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; mou</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; In</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; In</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; )</span>}$

Among them, P _t =P ₀ ×0.7, that is, the value of the control sample when the luminous flux decays to 70%, P ₀ is the initial luminous flux of the control sample, and t is the electrification of the control sample at this temperature point operating hours.

The junction temperature of the control sample in the heated state satisfies:

T _D =T _CD +W×R _jc +273,

If, the number of samples N in the preferred embodiment of the present invention is 15, and wherein 5 samples are set as the conventional group, and the remaining 10 are equally divided into two groups and set as the control group, then the degree of confidence can be obtained by the following formula:

${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; In</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; mou</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; mou</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}}$

Furthermore, the lifetime value of the LED light source at room temperature can be calculated by the formula:

$T_a=T\&times;\exp \left[\frac{{\mathrm{E.}}_a}{K\left(\frac{1}{T_j-25}\right)}\right]$ get.

T_mou1与T_mou2分别为两个对照组样品在加温状态下的结温，T_j为常规组样品在常温下的结温。in,

T _mou1 and T _mou2 are the junction temperatures of the two control samples in the heated state, respectively, and T _j is the junction temperature of the routine group samples at room temperature.

The following is an example to explain the above-mentioned LED light source accelerated life test method in more detail:

For the accelerated life test of a certain type of LED light source, 15 LED light source samples were taken and divided into three groups, 1-5# was the normal group, 6-10# and 11-15# were the control group. Among them, the ambient temperature of 6-11# is 114 degrees, and the ambient temperature of 11-15# is 132 degrees. Use 1-5# samples to test the junction temperature of the LED light source at room temperature, and test the attenuation of the luminous flux of the sample at this junction temperature. The actual test result shows that the attenuation rate of the luminous flux of the sample basically has no attenuation. Therefore, the ambient temperature was increased to 114 degrees and 132 degrees to test the samples of the two groups of control groups respectively. It was to test the temperature of the incubator at 114 degrees and 132 degrees respectively by controlling the cloth probe to ensure that the temperature of the incubator was even and balanced. After working for a certain period of time, test its parameters as follows:

In the conventional group, the actual test shows that the luminous flux attenuation rate basically has no attenuation, and the data are as follows:

Increase to the following temperature for testing, and test the temperature of the incubator at 114 degrees and 132 degrees through cloth probes to ensure that the temperature of the incubator is even and balanced. After working in the incubator for a certain period of time, test its parameters as follows:

1. 6-11#, the ambient temperature is 114 degrees, and it has been working for 255 hours without abnormality; the luminous flux test results are as follows:

2. After working for 263 hours at an ambient temperature of 132 degrees, there is no abnormality in the work; the luminous flux test results are as follows:

3. Decay to 70% of the value

Based on the above data, it can be concluded that the service life of the LED light source is 77,000 hours in an environment with a normal temperature of 25 degrees.

The above-mentioned LED light source accelerated life test method can accelerate the failure to find its potential defects by increasing its working temperature stress under the condition of keeping the failure mechanism of the driving power supply unchanged, and according to the accelerated life test model and Introduce confidence to deduce its life under normal temperature stress level, make the product mature in design and process much faster than traditional design and test, thereby shortening the total time of the development process, so that it can be put on the market as soon as possible and seize the market Share, product design and process mature quickly, product development and production costs are lower.

The above embodiments are only to illustrate the technical conception and characteristics of the present invention. The purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and cannot limit the protection scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the claims of the present invention shall fall within the scope of the claims of the present invention.

Claims (10)

1. A LED light source accelerated life testing system, characterized in that, comprising: A sample grouping device, which is used to equally divide N samples into multiple groups, and set one of the multiple groups as a routine group, and the remaining groups as a control group; The first junction temperature testing device is used to test the junction temperature of the conventional group of samples at normal temperature; A heating device, used to heat each control group sample; The second junction temperature testing device is used to test the junction temperature of each control group sample in a heated state; Lifetime calculation device, used to calculate the confidence level and the LED lifespan of each control group sample under heating state; The heating test device is used to obtain the lifespan of the LED light source at normal temperature based on the confidence calculated by the calculation device and the LED lifespan of each control group sample in a heated state. 2. LED light source accelerated life testing system according to claim 1, is characterized in that, the temperature that described heating device heats to each described control group sample all will be less than the junction temperature of described normal group sample at normal temperature . 3. The LED light source accelerated life testing system according to claim 1, wherein the life measuring device comprises Confidence measurement module, used to calculate confidence; The lifetime calculation module is used to calculate the LED lifetime of each control group sample in a heated state. 4. The LED light source accelerated life testing system according to claim 1, characterized in that the number N of samples is greater than or equal to 15. 5. A LED light source accelerated life testing method, is characterized in that, comprises the following steps: S100. Divide the N samples into multiple groups, and set one of the multiple groups as a routine group, and the remaining groups as a control group; S200. Test the junction temperature of the conventional group samples at normal temperature; S300, respectively heating the samples of the control group; S400. Test the junction temperature of each control group sample in a heated state S500, calculating the confidence level, and the life value of each control group sample under the heating state; S600. Obtain the lifetime of the LED light source at normal temperature based on the confidence and the lifetime values of each of the control samples in a heated state. 6 . The LED light source accelerated life testing method according to claim 5 , wherein the heating temperature of each control group sample is lower than the junction temperature of the conventional group sample at room temperature. 7 . 7. The LED light source accelerated life testing method according to claim 5, wherein the junction temperature of the conventional group of samples at room temperature satisfies: T _j =T _c +W×R _jc +273, Where T _c is the temperature of the LED light source at room temperature, R _jc is the thermal resistance coefficient of the LED light source, W = conduction voltage × operating current. 8. The LED light source accelerated life testing method according to claim 5, characterized in that, the junction temperature of the control group sample in a heated state satisfies: T _D =T _CD +W×R _jc +273, Wherein, T _CD is the temperature of the LED light source of the control group in the heated state, R _jc is the thermal resistance coefficient of the LED light source, W=conducting voltage×operating current. 9. The LED light source accelerated life testing method according to claim 5, wherein the life value of each control group in a heated state satisfies ${\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; mou</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; In</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; In</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; )</span>}$ Wherein, P _t =P ₀ ×0.7, P ₀ is the initial luminous flux of the control group, and t is the power-on working time of the control group at this temperature point. 10. The LED light source accelerated life testing method according to claim 6, wherein the number of samples N is 15, 5 of which are set as the conventional group, and the remaining 10 are equally divided into two groups and set is the control group, then the confidence ${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; In</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; mou</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; mou</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}}$ The life value of the LED light source at room temperature ${\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span>\frac{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}{\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 25</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ]</span>$ in,

T _mou1 and T _mou2 are the lifetime values of the two samples in the control group in a heated state, respectively, and T _j is the junction temperature of the samples in the conventional group at room temperature.

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