CN110823532A - Junction temperature test method based on LED relative spectrum along with temperature change - Google Patents

Junction temperature test method based on LED relative spectrum along with temperature change Download PDF

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Publication number
CN110823532A
CN110823532A CN201911294271.1A CN201911294271A CN110823532A CN 110823532 A CN110823532 A CN 110823532A CN 201911294271 A CN201911294271 A CN 201911294271A CN 110823532 A CN110823532 A CN 110823532A
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led
junction temperature
temperature
water washing
method based
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CN201911294271.1A
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郭爽
汪宝
贾晓
王同斌
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Nanyang Institute of Technology
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Nanyang Institute of Technology
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01MTESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02Testing optical properties
    • G01M11/0207Details of measuring devices

Abstract

The invention relates to the technical field of LED junction temperature test methods, in particular to a junction temperature test method based on the temperature change of an LED relative spectrum, which comprises the steps of packaging an LED tube core on a 5mm industrial pure aluminum plate, and carrying out oxidation insulation treatment; the processing steps are as follows: degreasing → cold water washing → alkaline etching → hot water washing + cold water washing surface photochemical treatment + hot water washing → cold water washing + anodic oxidation → water washing; and then fixing an electrode at the cup-shaped groove and welding a lead on the electrode to complete the preparation of the integrated packaging substrate, wherein the junction temperature of the LED is measured by a relative spectral intensity method, the difference between the junction temperature measured by the relative spectral intensity method and the measurement result of a forward voltage drop method is not more than 2 ℃, and the advantage of more accurate junction temperature measurement by the forward voltage drop method is kept. In addition, the relative spectral intensity method is the same as the spectroscopic method, and non-contact measurement is adopted, so that the characteristics of high efficiency and intuition are kept without damaging the lamp structure in spectroscopic measurement.

Description

Junction temperature test method based on LED relative spectrum along with temperature change
Technical Field
The invention relates to the technical field of LED junction temperature test methods, in particular to a junction temperature test method based on the change of an LED relative spectrum along with temperature.
Background
The led (light emitting diode) has many advantages of small size, long life, high brightness, energy saving, environmental protection, etc., and is considered as the most potential fourth generation illumination light source, and has been widely applied in the fields of signal indication, display, general illumination, etc. The self-photocolor characteristics of the LED are closely related to the temperature, and the luminous efficiency of the LED is reduced and the service life of the LED is shortened along with the increase of junction temperature. Therefore, the method has important significance for rapidly, scientifically and conveniently measuring the junction temperature of the LED, particularly the junction temperature of the packaged LED module.
The LED junction temperature detection method recommended by the national standard is a forward voltage method, and in addition, relevant scholars have also developed methods such as a peak wavelength method, a valley wavelength method, a radiation intensity method, a blue-white ratio method, and the like. The forward voltage method is considered as the most accurate method for measuring the junction temperature of the LED, but for the finished LED lamp, due to the limitation of the material of the lamp housing, it is generally difficult to measure the voltage drop at a pin of a certain LED lamp, which results in many limitations on the application of the forward voltage method. A peak wavelength method is proposed to determine the junction temperature of the LED, and the effective life of the LED is predicted by using the correspondence between the peak wavelength and the junction temperature. The method has the advantages of convenience and non-contact, but the drift of the peak wavelength is small, which causes an error which is difficult to avoid, and in addition, the peak wavelength of some LEDs has no linear relation with the junction temperature. The blue-white ratio method is used for measuring junction temperature according to the relation of the blue-white ratio junction temperature of the fluorescent powder conversion type white LED, the method is not applicable to non-fluorescent powder conversion type LEDs, and in addition, for some LEDs, the blue-white ratio and the junction temperature have no linear relation. The valley value method of about 485nm is to measure the junction temperature by adopting the linear relation between the valley value of the fluorescent powder conversion type LED spectrum and the junction temperature, and the precision of the method is higher than that of the peak wavelength method. The radiation intensity method is to determine the junction temperature by a method that the radiation intensity of the LED and the junction temperature are in a linear relation under a certain driving current, but the radiation intensity needs to be accurately measured during the test, and the accurate measurement of the radiation intensity is difficult for some LED finished lamps.
Disclosure of Invention
In order to solve the above problems, the present invention provides a junction temperature test method based on the variation of the relative spectrum of LEDs with temperature.
The technical problem to be solved by the invention is realized by adopting the following technical scheme:
a junction temperature test method based on the variation of the relative spectrum of an LED with temperature, the method comprising the steps of:
(1) the high-power white light LED is packaged on a 5mm high-heat-conduction covering copper ceramic plate, and the process comprises the following steps: crystal expansion and crystal thorn baking → gold wire welding → powder dispensing baking → dispensing baking; the integrated packaging substrate is used for replacing a bracket, an aluminum substrate and a heat sink in the traditional packaging, and the high-heat-conductivity covering copper ceramic plate is formed by sintering a ceramic substrate and a conductive layer at high temperature and high pressure;
(2) connecting a probe of the spectrum analyzer with one side of an integrating sphere instrument, connecting the other side of the integrating sphere instrument with an LED to be tested, connecting the output end of the spectrum analyzer with a computer, connecting the computer with a driving power supply, and connecting the driving power supply with an integrated packaging substrate;
(3) measuring forward voltage, dominant wavelength and spectral intensity of the LED by using a spectrum analyzer; an LC filter circuit is added near a single chip microcomputer chip and is arranged on an integrated packaging substrate close to a single chip microcomputer core, a small current controlled current source is a 1-63mA precision controlled current source which is manufactured by the single chip microcomputer through controlling TL431 through a relay, the single chip microcomputer is isolated from interference on a test part, and power of the whole device is provided by a transformer series connection voltage-stabilized power supply;
(4) the wavelength with the minimum light radiation intensity value is selected as the characteristic wavelength, the light radiation intensity of the characteristic wavelength is increased along with the increase of the junction temperature, and the light radiation intensity of the characteristic wavelength is used for reflecting the change of the junction temperature of the LED.
Further, the constant current in the step (3) drives a current which is 5% less than the rated current of the LED to be tested.
Furthermore, in step (3), the controlled current source adopts a servo power supply, a ferromagnetic shielding case with the thickness of 2mm is additionally arranged outside the power transformer besides the power transformer adopts an R-shaped iron core, in order to reduce the electromagnetic interference of the transformer to the device, an isolation diode is additionally arranged in each of the two power supplies, and in order to further reduce the influence between the two current sources.
Compared with the prior art, the invention has the beneficial effects that: the junction temperature test method based on the LED relative spectrum along with the temperature change adopts a relative spectrum intensity method to measure the junction temperature of the LED, and compares the junction temperature with the junction temperature measured by a forward voltage drop method and a spectrum method which are generally accepted at present; the difference between the junction temperature measured by the relative spectral intensity method and the measurement result of the forward voltage drop method is not more than 2 ℃, and the advantage of more accurate junction temperature measurement of the forward voltage drop method is kept. In addition, because the relative spectral intensity method is the same as the spectroscopic method, the non-contact measurement is adopted, the structure of the lamp is kept from being damaged in the spectroscopic measurement, and the characteristics of high efficiency and intuition are realized.
Drawings
FIG. 1 is a graph of relative spectra at a junction temperature of 60 ℃;
fig. 2 is a graph of relative optical radiation intensity versus junction temperature.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a technical scheme that:
a junction temperature test method based on the variation of the relative spectrum of an LED with temperature, the method comprising the steps of:
(1) the high-power white light LED is packaged on a 5mm high-heat-conduction covering copper ceramic plate, and the process comprises the following steps: crystal expansion and crystal thorn baking → gold wire welding → powder dispensing baking → dispensing baking; the integrated packaging substrate is used for replacing a bracket, an aluminum substrate and a heat sink in the traditional packaging, and the high-heat-conductivity covering copper ceramic plate is formed by sintering a ceramic substrate and a conductive layer at high temperature and high pressure;
(3) connecting a probe of the spectrum analyzer with one side of an integrating sphere instrument, connecting the other side of the integrating sphere instrument with an LED to be tested, connecting the output end of the spectrum analyzer with a computer, connecting the computer with a driving power supply, and connecting the driving power supply with an integrated packaging substrate;
(4) measuring forward voltage, dominant wavelength and spectral intensity of the LED by using a spectrum analyzer, and measuring and controlling the temperature of the integrated packaging substrate by using a self-made temperature control system with a semiconductor heater so as to control initial junction temperature, namely the junction temperature measured at the moment of starting power-on; after the LED tube core and the integrated packaging substrate realize thermal balance, applying 340mA constant current drive to a device to be tested and simultaneously measuring initial voltage, initial dominant wavelength and initial spectrum intensity; at the moment of starting measurement, the self-heating effect of the LED driving current on the tested device is very small and can be ignored, and the thermal resistance of the integrated packaging substrate is low, so that the LED junction temperature can be considered to be consistent with the balance temperature of the integrated packaging substrate. After the driving current is self-heated and balanced, respectively measuring the forward voltage, the dominant wavelength and the spectral intensity of the tested device; an LC filter circuit is added near a single chip microcomputer chip and is arranged on an integrated packaging substrate close to a single chip microcomputer core, a small current controlled current source is a 1-63mA precision controlled current source which is manufactured by the single chip microcomputer through controlling TL431 through a relay, the single chip microcomputer is isolated from interference on a test part, and power of the whole device is provided by a transformer series connection voltage-stabilized power supply;
(5) the wavelength with the minimum light radiation intensity value is selected as the characteristic wavelength, the light radiation intensity of the characteristic wavelength is increased along with the increase of the junction temperature, and the light radiation intensity of the characteristic wavelength is used for reflecting the change of the junction temperature of the LED.
And (4) driving the current which is 5% less than the rated current of the LED to be tested by the constant current in the step (3).
The controlled current source adopts a servo power supply, a ferromagnetic shielding cover with the thickness of 2mm is additionally arranged outside the power transformer besides the power transformer adopts an R-shaped iron core, in order to reduce the electromagnetic interference of the transformer to the device, the two power supplies are respectively and additionally provided with an isolation diode, and in order to further reduce the influence between the two current sources.
When the temperature changes, the forbidden band width of the LED chip, the forbidden band width of the fluorescent powder and the position of the energy level in the forbidden band are all influenced by the temperature, and the influence of the temperature on the forbidden band width causes the light-emitting spectrum of the blue LED chip to change, so that the photoluminescence spectrum of the fluorescent powder also changes. This allows the intensity of each wavelength in the overall radiation spectrum to vary with temperature. There are wavelengths in the LED spectrum where the intensity varies significantly (characteristic wavelengths) which are correlated with junction temperature variations, which can theoretically be reflected by the variation in intensity of the characteristic wavelengths.
The PMS-50 spectral analysis system is used for measuring the forward voltage, the dominant wavelength and the spectral intensity of the LED, and a self-made temperature control system with a semiconductor heater is used for measuring and controlling the temperature of the integrated packaging substrate so as to control the initial junction temperature (the junction temperature measured at the moment of starting power-on is called the initial junction temperature). After the LED die and the integrated package substrate are thermally balanced, 340mA constant current is applied to the device under test, and the initial voltage, the initial dominant wavelength, and the initial spectral intensity are measured at the same time (the data measured at the moment of starting power-on is referred to as the initial forward voltage, the initial dominant wavelength, and the initial spectral intensity at the initial junction temperature). At the moment of starting measurement, the self-heating effect of the LED driving current on the tested device is very small and can be ignored, and the heat resistance of the integrated packaging substrate is low, so that the LED junction temperature and the balance temperature of the integrated packaging substrate can be considered to be consistent. After the driving current is self-heated and balanced, the forward voltage, dominant wavelength and spectral intensity of the device to be tested are measured respectively.
As shown in fig. 1, as the junction temperature changes, the areas where the radiation intensity changes most significantly are at wavelengths of 485nm and 550nm, where the light radiation intensity has a minimum at the wavelength of 485nm and a maximum at 550 nm; the light radiation intensity at the minimum value has the characteristic of linear increase along with the change of the junction temperature, and the light radiation intensity at the maximum value also has obvious change along with the change of the junction temperature, so the linear characteristic of the change of the light radiation intensity at the minimum value is more obvious; the intensity of the light radiation at the characteristic wavelength can be used to reflect the variation of the junction temperature of the LED.
As shown in fig. 2, the wavelength with the minimum light radiation intensity is selected as the characteristic wavelength, the light radiation intensity of the characteristic wavelength increases with the increase of the junction temperature, and the light radiation intensity of the characteristic wavelength is used to reflect the change of the junction temperature of the LED.
While the invention has been described above with reference to an embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the various features of the embodiments disclosed herein may be used in any combination, provided that there is no structural conflict, and the combinations are not exhaustively described in this specification merely for the sake of brevity and conservation of resources. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (3)

1. A junction temperature test method based on LED relative spectrum variation with temperature is characterized by comprising the following steps:
(1) the high-power white light LED is packaged on a 5mm high-heat-conduction covering copper ceramic plate, and the process comprises the following steps: crystal expansion and crystal thorn baking → gold wire welding → powder dispensing baking → dispensing baking; the integrated packaging substrate is used for replacing a bracket, an aluminum substrate and a heat sink in the traditional packaging, and the high-heat-conductivity covering copper ceramic plate is formed by sintering a ceramic substrate and a conductive layer at high temperature and high pressure;
(2) connecting a probe of the spectrum analyzer with one side of an integrating sphere instrument, connecting the other side of the integrating sphere instrument with an LED to be tested, connecting the output end of the spectrum analyzer with a computer, connecting the computer with a driving power supply, and connecting the driving power supply with an integrated packaging substrate;
(3) measuring forward voltage, dominant wavelength and spectral intensity of the LED by using a spectrum analyzer; an LC filter circuit is added near a single chip microcomputer chip and is arranged on an integrated packaging substrate close to a single chip microcomputer core, a small current controlled current source is a 1-63mA precision controlled current source which is manufactured by the single chip microcomputer through controlling TL431 through a relay, the single chip microcomputer is isolated from interference on a test part, and power of the whole device is provided by a transformer series connection voltage-stabilized power supply;
(4) the wavelength with the minimum light radiation intensity value is selected as the characteristic wavelength, the light radiation intensity of the characteristic wavelength is increased along with the increase of the junction temperature, and the light radiation intensity of the characteristic wavelength is used for reflecting the change of the junction temperature of the LED.
2. A junction temperature test method based on the variation of LED relative spectrum with temperature as claimed in claim 1, wherein: and (4) driving the current which is 5% less than the rated current of the LED to be tested by the constant current in the step (3).
3. A junction temperature test method based on the variation of LED relative spectrum with temperature as claimed in claim 1, wherein: in the step (3), the controlled current source adopts a servo power supply, a ferromagnetic shielding cover with the thickness of 2mm is additionally arranged outside the power transformer besides the power transformer adopts an R-shaped iron core, in order to reduce the electromagnetic interference of the transformer to the device, and an isolation diode is additionally arranged in each of the two power supplies in order to further reduce the influence between the two current sources.
CN201911294271.1A 2019-12-16 2019-12-16 Junction temperature test method based on LED relative spectrum along with temperature change Pending CN110823532A (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113099701A (en) * 2021-04-22 2021-07-09 南阳理工学院 Optical electronic whiteboard heat dissipation device

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JP6021771B2 (en) * 2012-10-09 2016-11-09 Hoya Candeo Optronics株式会社 Light emitting diode junction temperature measuring device, light emitting diode junction temperature measuring method, light emitting diode junction temperature measuring program, and light irradiation device
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113099701A (en) * 2021-04-22 2021-07-09 南阳理工学院 Optical electronic whiteboard heat dissipation device
CN113099701B (en) * 2021-04-22 2023-09-26 南阳理工学院 Optical electronic whiteboard heat abstractor

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