Junction temperature testing method and system for laser diode chip

Abstract

The invention discloses a junction temperature test method and system for a laser diode chip, and the method comprises the following steps: obtaining the resistance values of a thermistor and the temperatures of a temperature sensor recorded at different temperature nodes, and obtaining a plurality of groups of test data; performing polynomial fitting on the obtained multiple groups of test data to obtain polynomials of different orders of the resistance parameters relative to the temperature; comparing the obtained polynomials in a set temperature interval, and selecting a polynomial coefficient with the best goodness of fit and a corresponding polynomial formula; and calculating a corresponding inverse function according to a polynomial formula, substituting the inverse function into the resistance value of the thermistor, and calculating the junction temperature of the laser diode chip. In the packaging process, the high-precision thermistor is arranged near the LD chip in advance, the junction temperature testing method is matched, it is ensured that the temperature is measured under the small environmental influence, and the testing temperature is closer to the actual junction temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic device testing, and particularly to a method and system for testing the junction temperature of a laser diode chip. Background Art

[0002] The chip junction temperature refers to the temperature of the PN junction region inside a semiconductor device. Especially in optoelectronic devices such as laser diodes (LDs), the junction temperature is one of the important parameters affecting the device performance and reliability. An excessively high junction temperature may lead to a decline in device performance, a shortening of the lifespan, or even damage. Therefore, accurate measurement and aging are the keys to ensuring its long-term reliability.

[0003] A high junction temperature will accelerate the aging of semiconductor materials, resulting in a shortened device lifespan. Especially for optoelectronic devices such as LDs and EMLs, too high a junction temperature will accelerate the failure process and significantly reduce the device reliability. Therefore, aging the chip at an accurate junction temperature can effectively eliminate early failure products without causing overstress damage to the LD.

[0004] With the wide application of optoelectronic devices, the junction temperature testing technology is also constantly developing. Currently, the testing methods are mainly divided into two categories: direct and indirect measurement: The direct measurement method, such as infrared imaging, directly obtains the temperature distribution on the chip surface, but is sensitive to the environment and materials, and the equipment is expensive, suitable for laboratory use.

[0005] The indirect measurement method, such as the wavelength drift method, detects the thermal resistance by inferring the wavelength related to temperature, then calculates the total power using voltage and current, and then subtracts the luminous power. This method also requires relatively expensive and complex equipment and is suitable for laboratory use. Summary of the Invention

[0006] The present invention aims to at least solve one of the technical problems existing in the prior art, and proposes a method and system for testing the junction temperature of a laser diode chip.

[0007] The technical solution of the present invention is realized as follows: The present invention provides a method for testing the junction temperature of a laser diode chip, including the following steps: Obtain the resistance values of the thermistor and the temperature of the temperature sensor recorded at different temperature nodes to obtain multiple groups of test data; Perform polynomial fitting on the obtained multiple groups of test data to obtain polynomials of different orders of resistance parameters with respect to temperature; Compare the obtained polynomials in a set temperature range, and select the polynomial coefficients and the corresponding polynomial formula with the best goodness of fit; Calculate the corresponding inverse function according to the polynomial formula, substitute the resistance value of the thermistor, and calculate the junction temperature of the laser diode chip.

[0008] Further, perform polynomial fitting on the obtained multiple sets of test data to obtain polynomials of different orders of the resistance parameter with respect to temperature, specifically including: Perform polynomial fitting on the obtained multiple sets of test data using the least squares method to obtain an Mth-order polynomial of the resistance parameter with respect to temperature; Convert the Mth-order polynomial into the standard function form of the least squares method ; Using the least squares method with respect to the condition that the partial derivative is 0, calculate the corresponding coefficient values in the polynomial of the resistance parameter with respect to temperature of the order; Repeat the above steps until polynomials of different orders are obtained.

[0009] Further, the resistance parameter obtained in step S2 with respect to temperature of the order polynomial is: , where , are polynomial coefficients.

[0010] Further, the standard function form of the least squares method is:

[0011] where , is a positive integer, are polynomial coefficients, is a polynomial with respect to , is the temperature corresponding to the rd temperature node, is the resistance value of the thermistor corresponding to the th temperature node.

[0012] Further, calculate its corresponding inverse function according to the polynomial formula, specifically including: obtaining the target temperature range and calculating its corresponding inverse function according to the polynomial on the target temperature range.

[0013] Further, obtaining the target temperature range and calculating its corresponding inverse function according to the polynomial on the target temperature range, specifically including: obtaining the target temperature range, performing smoothing processing on the test data within the target temperature range, and calculating its corresponding inverse function according to the polynomial on the smoothed target temperature range.

[0014] Further, obtaining the target temperature range specifically includes: selecting a temperature range containing multiple test data as the target temperature range according to the preset estimated junction temperature value.

[0015] Furthermore, the test data within the target temperature range is smoothed, specifically including: using a convolution smoothing algorithm to smooth the test data within the target temperature range.

[0016] Furthermore, the convolution smoothing algorithm is a Savitzky-Golay convolution smoothing algorithm.

[0017] Furthermore, the thermistor is configured to measure the temperature of the laser diode chip, and the temperature sensor is configured to measure the ambient temperature.

[0018] The present invention also discloses a junction temperature testing system for a laser diode chip, comprising a host, an aging box, a temperature sensor, a thermistor, and an aging board for placing the laser diode chip, wherein the aging board is installed in the aging box, the thermistor is used to measure the temperature of the laser diode chip, the temperature sensor is used to measure the ambient temperature, the host is used to collect the resistance value of the thermistor and the temperature of the temperature sensor, and calculate the junction temperature of the laser diode chip according to the junction temperature testing method described above.

[0019] Furthermore, the laser diode chip is packaged in TO packaging, and the thermistor is placed next to the laser diode chip, so that the thermistor and the laser diode chip are thermally coupled.

[0020] Furthermore, the aging board is provided with a plurality of slots for inserting laser diode chips.

[0021] Compared with the existing technology, the present invention has the following beneficial effects: the present invention provides a junction temperature test method for batch laser diode chips based on thermistors, which has significant technical advantages and practicality compared with the existing chip junction temperature test methods. The existing technology usually only allows wavelength testing of a single LD chip under a single condition to infer the junction temperature. This method is easily affected by changes in the external environment, and the test time of a single TO is long. The present invention places a high-precision thermistor near the LD chip in advance during the packaging process, and cooperates with the junction temperature test method of the present invention to ensure that the temperature is measured under less environmental influences, so that the test temperature is closer to the actual junction temperature; and because the method only involves resistance measurement, the method is easier to implement.

[0022] The present invention, by employing thermistor measurement technology, can simultaneously test the junction temperature of multiple TO-packaged LD chips under the same environmental conditions. By implementing batch testing, the present invention can significantly reduce the test time for a single chip, improving overall test efficiency. Furthermore, batches of TOs can be tested under the same conditions, ensuring the consistency and accuracy of test data and avoiding test errors caused by varying environmental conditions, thereby improving the reliability of test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of a TO-packaged laser diode chip provided by an embodiment of the present invention; Figure 2 Schematic diagram of the structure of a junction temperature testing device for a laser diode chip provided by an embodiment of the present invention; Figure 3 Flowchart of a junction temperature testing method for a laser diode chip provided by an embodiment of the present invention.

[0024] In the drawings, 1 is a heat sink, 2 is a laser diode chip, 3 is a thermistor, 4 is an aging board, and 5 is an aging chamber. Detailed implementation manners

[0025] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] See Figure 3 , an embodiment of the present invention provides a method for testing the junction temperature of a laser diode chip, including the following steps: S1: Obtain the resistance values of the thermistor and the temperatures of the temperature sensor recorded at different temperature nodes, and obtain groups of test data. The test data corresponding to the th temperature node is , , is a positive integer, where is the temperature of the temperature sensor corresponding to the th temperature node, and is the resistance value of the thermistor corresponding to the th temperature node; S2: Perform polynomial fitting on the obtained groups of test data to obtain the resistance parameter as a -order polynomial of temperature . The resistance parameter obtained in step S2 as a -order polynomial of temperature is: , where , are polynomial coefficients. is a sequence of is the resistance value at the corresponding temperature node; S3: Convert the M-order polynomial into the standard function form of the least squares method: ; where, , is a positive integer, is the polynomial coefficient, is with respect to the -th order polynomial; S4: Use the least squares method with respect to the partial derivative being to calculate the corresponding coefficient values in the -th order polynomial of the resistance parameter with respect to temperature ; S5: Repeat steps S2 to S4 until polynomials of different orders are obtained; S6: Compare the obtained polynomials and the fitting curves in the set temperature range, and select the polynomial coefficients with the best goodness of fit and the corresponding preliminary polynomial formula; S7: According to the polynomial formula, calculate its corresponding inverse function , substitute the resistance value of the thermistor when the chip is working normally, and calculate the junction temperature of the laser diode chip.

[0027] By changing the temperature of the aging chamber, obtain the resistance values of the thermistor recorded at different temperature nodes and the temperatures of the temperature sensor, and obtain

[0028] a set of test data. Furthermore, step S7 specifically includes: obtaining the target temperature range, according to the polynomial formula on the target temperature range, calculating its corresponding inverse function

[0029] , substitute the resistance value of the thermistor when the chip is working normally, and calculate the junction temperature of the laser diode chip.

[0030] Furthermore, obtaining the target temperature range and calculating the corresponding inverse function according to the polynomial on the target temperature range specifically includes: obtaining the target temperature range, performing smoothing processing on the test data within the target temperature range, and calculating the corresponding inverse function according to the polynomial on the smoothed target temperature range.

[0031] Further, the convolution smoothing algorithm is the Savitzky-Golay convolution smoothing algorithm.

[0032] Further, obtaining the target temperature range specifically includes: selecting, according to a preset estimated junction temperature value, a temperature range containing multiple test data as the target temperature range.

[0033] When the heat generation of the chip is small and the temperature is relatively accurate, measure multiple temperature points, and roughly estimate the estimated junction temperature value by linearly fitting the temperature points.

[0034] Further, selecting the polynomial coefficients with the best goodness of fit specifically includes: performing a goodness-of-fit test on the fitting polynomial using the chi-square distribution to select the polynomial coefficients with the best goodness of fit.

[0035] Further, for the obtained group of test data, perform polynomial fitting, specifically including: performing polynomial fitting on the obtained group of test data using the least squares method.

[0036] The thermistor is configured to measure the temperature of the laser diode chip, and the temperature sensor is configured to measure the ambient temperature.

[0037] Further, before the step of obtaining the resistance values of the thermistors recorded at different temperature nodes, the following steps are further included: testing the laser diode chip under different temperature conditions, collecting the resistance values of the thermistors and the temperatures of the temperature sensors. The temperature range is roughly estimated by linearly fitting the resistance values of multiple thermistors, the relatively accurate chip temperature is estimated by the polynomial obtained by fitting the resistance values of multiple thermistors, and only the thermistor values can be measured by changing the temperature of the aging oven.

[0038] See Figure 2 , the embodiment of the present invention also discloses a junction temperature testing device for a laser diode chip, including an aging oven, a temperature sensor, and an aging board for placing the laser diode chip, and the aging board is installed in the aging oven. In some embodiments, several (such as 48) chips can be inserted into the aging board. And several aging boards can be installed in the aging oven.

[0039] In some embodiments, the temperature sensor uses a thermocouple. The thermistor measures the temperature near the chip temperature to estimate the junction temperature. The thermocouple measures the ambient temperature.

[0040] See Figure 1 and Figure 2, an embodiment of the present invention also discloses a junction temperature testing system for a laser diode chip, including a host computer, an aging chamber 5, a temperature sensor, a thermistor 3, and an aging board 4 for placing the laser diode chip 2. The aging board is installed inside the aging chamber. The thermistor is used to measure the temperature of the laser diode chip 2. The temperature sensor is used to measure the ambient temperature and transmit the collected temperature to the host computer. The host computer is used to collect the resistance value of the thermistor and calculate the junction temperature of the laser diode chip based on the resistance value of the thermistor and the temperature collected by the temperature sensor.

[0041] Further, the host computer is used to collect the resistance value of the thermistor and the temperature of the temperature sensor, and calculate the junction temperature of the laser diode chip according to the junction temperature testing method as described above.

[0042] The host computer is connected with a display screen, which can display data such as resistance and temperature.

[0043] Further, the laser diode chip and the LD chip are packaged in TO. The thermistor 3 is placed beside the laser diode chip 2 to thermally couple the thermistor with the laser diode chip. The laser diode chip is installed on the heat sink 1.

[0044] Further, the temperature sensor is placed on the aging board 4.

[0045] Further, the aging board is provided with a plurality of slots for the laser diode chip to be inserted.

[0046] TO is powered on in batches through the aging board, and the aging board is powered on in batches through the aging chamber.

[0047] Further, the junction temperature testing system for the laser diode chip of the present invention further includes a power supply and a control unit. The power supply is used to supply power to the testing system. The control unit is connected to the host computer through a communication unit. The control unit is used to collect the signals of the temperature sensor and the thermistor and transmit them to the host computer.

[0048] The specific process of the junction temperature testing of the laser diode chip (i.e., the LD chip) of the present invention includes: Connect the input plug of the power supply to the 220V power supply, and connect the control unit to the PC host through a serial cable; Connect the aging board interface to the corresponding interface of the DC constant voltage source in the order of the connectors; Stick the thermocouples with corresponding numbers of the thermometer to the designated positions of the aging board respectively with high-temperature tape: temperature probes can be installed at multiple same-type temperature measurement points for each corresponding type of temperature measurement point according to actual conditions; Insert the LD chip into the burn-in board and electrically connect the thermistor to the control unit: Refer to the actual package pin definition and insert the two pins corresponding to the LD chip into the corresponding slots on the burn-in board. Then bend the TO-CAN pins corresponding to the high-precision thermistor and pull them out of the burn-in board slot. Connect the wires with pin jacks for electrical connection to the control system. Repeat this step multiple times depending on the number of TO-CANs that need to be measured. Set the pin type and operating current parameters in the host software: On the software's parameter control page, change the pin type to match the actual package pin definition and set the current parameter to the corresponding operating current during burn-in. All parameter measurements are performed on the burn-in board after the chip is packaged into a TO package and powered on. Since high-temperature testing is required, it is performed in a burn-in chamber.

[0049] After the current and temperature are stable, read the resistance and temperature data: Place the aging board in the aging box, and after the readings of each temperature measuring point of the thermometer are stable, use the data test part of the test system to measure, and after the readings are stable, you can read the corresponding resistance value displayed on the host, and record the readings of each temperature measuring point of the thermometer; stop aging, and after the readings of each temperature measuring point of the thermometer are stable, use the data test part of the test system to measure, and after the readings are stable, read the corresponding resistance value displayed on the host, and record the readings of each temperature measuring point of the thermometer; Repeat the above steps to Different temperature nodes Record the corresponding resistance value displayed at this temperature , for the The corresponding test data set is obtained for each temperature node .

[0050] Estimate the junction temperature using the above test data , specifically including: SS1: Use the least squares method to get the test data set Perform polynomial fitting to obtain resistance parameters About temperature of Order polynomial:

[0051] in ; SS2: The order polynomial can be transformed into the scalar function form of the least squares method:

[0052] in ; SS3: Using the least squares method about The condition where the partial derivative is 0 can be used to calculate the parameters Regarding temperature of the corresponding coefficient value in the polynomial of order ; Repeat steps SS1 to SS3 to obtain polynomials of different orders. Compare the obtained polynomials and the fitting curves in a reasonable range, and select the polynomial coefficients with the best goodness of fit and the corresponding preliminary polynomial formula; Judge the predicted value of the junction temperature according to the actual situation, and select a temperature range that includes multiple test data sets ; For the data points within the target temperature range, use the Savitzky-Golay convolution smoothing algorithm to smooth the data within the range, and reduce the noise and sudden fluctuations within the target range while retaining the basic trend of the data; According to the polynomial formula on the smoothed target range, calculate its corresponding inverse function , substitute the observed resistance value displayed by the PC when the chip is working properly, and the corresponding estimated junction temperature can be calculated .

[0053] The present invention provides a relatively convenient and batchable method for testing the junction temperature of a laser diode chip, which can directly test the ambient temperature and the working temperature of the actual chip. In the packaging process of the present invention, a high-precision thermistor is placed near the LD chip in advance to ensure that the temperature is measured under less environmental influence, making the measured temperature closer to the actual junction temperature; and since this method only involves resistance measurement, this method is easier to implement.

[0054] It can be understood that the above embodiments are only exemplary embodiments adopted to illustrate the principle of the present disclosure. However, the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also regarded as the protection scope of the present disclosure.

Claims

1. A method for testing the junction temperature of a laser diode chip, characterized in that, It includes the following steps: Obtain the resistance values of the thermistor and the temperatures of the temperature sensor recorded at different temperature nodes to obtain multiple groups of test data; Perform polynomial fitting on the obtained multiple groups of test data to obtain polynomials of different orders of the resistance parameter with respect to temperature; Compare the obtained polynomials in a set temperature range, and select the polynomial coefficients with the best goodness of fit and the corresponding polynomial formula; Calculate the corresponding inverse function according to the polynomial formula, substitute the resistance value of the thermistor, and calculate the junction temperature of the laser diode chip.

2. The method for testing the junction temperature of a laser diode chip according to claim 1, characterized in that: Perform polynomial fitting on the obtained multiple groups of test data to obtain polynomials of different orders of the resistance parameter with respect to temperature, specifically including: Use the least squares method to perform polynomial fitting on the obtained multiple groups of test data to obtain an M-order polynomial of the resistance parameter with respect to temperature; Convert the M-order polynomial into the standard function form of the least squares method ; Using the least squares method Regarding The corresponding coefficient values in the nth-order polynomial of the resistance parameter with respect to temperature are calculated under the condition that the partial derivative is 0; Repeat the above steps until polynomials of different orders are obtained.

3. The method for testing the junction temperature of a laser diode chip according to claim 1, characterized in that: Calculate the corresponding inverse function according to the polynomial formula, specifically including: obtaining a target temperature range, and calculating the corresponding inverse function according to the polynomial on the target temperature range.

4. The method for testing the junction temperature of a laser diode chip according to claim 3, wherein: Obtain a target temperature range, calculate the corresponding inverse function according to the polynomial on the target temperature range, specifically including: obtaining a target temperature range, performing smoothing processing on the test data within the target temperature range, and calculating the corresponding inverse function according to the polynomial on the smoothed target temperature range.

5. The method for testing the junction temperature of a laser diode chip according to claim 3 or 4, characterized in that: Obtain a target temperature range, specifically including: selecting a temperature range containing multiple test data as the target temperature range according to the preset estimated value of the junction temperature.

6. The method for testing the junction temperature of a laser diode chip according to claim 4, characterized in that: Perform smoothing processing on the test data within the target temperature range, specifically including: using a convolution smoothing algorithm to perform smoothing processing on the test data within the target temperature range.

7. The method for testing the junction temperature of a laser diode chip according to claim 1, characterized in that: The thermistor is configured to measure the temperature of the laser diode chip, and the temperature sensor is configured to measure the ambient temperature.

8. A junction temperature testing system for a laser diode chip, characterized in that: It includes a host, an aging oven, a temperature sensor, a thermistor, and an aging board for placing the laser diode chip. The aging board is installed in the aging oven. The thermistor is used to measure the temperature of the laser diode chip, the temperature sensor is used to measure the ambient temperature, and the host is used to collect the resistance value of the thermistor and the temperature of the temperature sensor, and calculate the junction temperature of the laser diode chip according to the junction temperature test method according to any one of claims 1 to 6.

9. The junction temperature testing system of the laser diode chip according to claim 8, wherein: The laser diode chip uses a TO package, and the thermistor is placed beside the laser diode chip to thermally couple the thermistor with the laser diode chip.

10. The junction temperature test system for a laser diode chip according to claim 8, wherein: The aging board is provided with a plurality of slots for inserting the laser diode chip.

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