A method for correcting channel brightness differences in LED multi-pin testing machines

Abstract

The present invention provides a method for correcting channel brightness differences of an LED multi-pin tester, comprising step S1, constructing a two-dimensional coordinate system; step S2, determining a grain unit; step S3, testing grain brightness; and step S4, correcting grain brightness. Specifically, a correction coefficient K is used to correct the brightness difference of grain channels in each grain unit. The present invention can correct the MAP distribution of LED epitaxial wafer brightness with periodic alternating row interval changes to a naturally transitioned MAP, which conforms to the growth characteristics of the epitaxial wafer and ensures the accuracy of the final test results, thereby solving the problem of multi-pin brightness channel differences in a multi-pin tester and avoiding the occurrence of multi-channel brightness deviations.

Description

Technical Field

[0001] The invention relates to the field of testing the brightness of LED crystal particles, and in particular to a method for correcting brightness differences of channels of an LED multi-pin testing machine. Background Art

[0002] LED multi-pin tester is a device that uses multiple probes to test multiple die at the same time. Compared with the traditional single-pin tester, it has the advantages of large capacity and high efficiency. For example, when testing, a 4-pin tester tests 4 dies arranged from top to bottom in parallel. Its test capacity is theoretically 4 times that of a single-pin tester. Therefore, 4-pin testers have been widely used in LED chip factories.

[0003] The 4-pin tester tests 4 crystals at the same time, and the same light receiving head receives the light source measured by the four channels where the 4 pins are located. Due to the constant wear of the probes of each channel during the test, the deviation caused by the operator's debugging of the probe position from the standard range, and the lack of stability of the machine test, the brightness of each channel received by the light receiving head will change by different amplitudes, which will cause the test brightness of each channel to deviate from the brightness at the beginning of the file calibration, and the deviation of each channel is inconsistent, and eventually there will be a problem of excessive brightness deviation between channels, that is, the brightness distribution of each row of crystals is inconsistent with the actual. For example, in the brightness test results, it can be clearly found in the MAP that there is a regular "fault" phenomenon in the brightness, that is, the row intervals of different colors in the MAP change periodically, which is inconsistent with the characteristics of the LED epitaxial wafer. There is a test regularity, which is an abnormality in the test, and the "fault" in some areas changes every 4 rows, which matches the number of 4 channels. The brightness of each channel changes periodically every time it changes a row, that is, the multi-pin brightness channel difference is abnormal.

[0004] The characteristic of LED epitaxial wafers is that the brightness and wavelength of each crystal grain are basically consistent in a small area (the area includes the area covered by 4 crystal grains of all sizes in the market in parallel), and the brightness distribution of LED epitaxial wafers naturally increases or decreases from the inside to the outside or from the top to the bottom, that is, the change between different colors in MAP is a gradual transition. Therefore, the actual test results of the 4-pin tester are inconsistent with the characteristics of the epitaxial wafer, that is, the problem of multi-pin brightness channel difference in the industry is abnormal.

[0005] Various existing multi-pin testers all have the problem of multi-pin brightness channel differences to varying degrees, which in turn affects the accuracy of testing the brightness of LED chips. Summary of the invention

[0006] The purpose of the present invention is to provide a method for correcting the brightness difference of channels of LED multi-pin testers, which is used to solve the problem of abnormal brightness channel differences of multi-pin testers, so as to improve the accuracy of testing the brightness of LED grains and avoid the situation of multi-channel brightness deviation. The specific technical scheme is as follows:

[0007] A method for correcting channel brightness differences of an LED multi-pin tester comprises the following steps:

[0008] Step S1: Construct a two-dimensional coordinate system

[0009] Before testing, the LED epitaxial wafer is scanned by an LED multi-pin tester, and a two-dimensional coordinate system is constructed based on the scanning results to calculate the coordinate position of each grain on the LED epitaxial wafer;

[0010] Step S2: Determine the grain unit

[0011] The LED multi-pin tester includes n groups of parallel-connected probes, wherein the value n is a natural number greater than or equal to 2;

[0012] The total number of rows of grains arranged in the vertical axis direction of the two-dimensional coordinate system of the LED epitaxial wafer is recorded as H, and each row of grains is parallel to the horizontal axis direction of the two-dimensional coordinate system;

[0013] If H is an integer multiple of the value n, then H is divided into p grain units in turn, and each grain unit contains n rows of grains;

[0014] If H is an integer multiple of the value n with a remainder, H is divided into p+1 crystal units in sequence, wherein each crystal unit in the first p crystal units contains n rows of crystals; the p+1th crystal unit contains Hp*n rows of crystals;

[0015] Step S3: Testing the brightness of grains

[0016] In the first p grain units, starting from the first grain unit, n groups of probes in the LED multi-pin tester are used to perform brightness tests on each row of grains in each grain unit along the horizontal axis direction of the two-dimensional coordinate system until the pth grain unit is tested;

[0017] In the p+1th die unit, the brightness of each row of the Hp*n rows of dies is tested along the horizontal axis direction of the two-dimensional coordinate system using a corresponding number of probes in an LED multi-needle tester;

[0018] Step S4: Correcting grain brightness

[0019] The correction coefficient K is used to correct the brightness difference of the grain channels in each grain unit.

[0020] In some implementation schemes, in step S4, n-1 correction coefficients K are correspondingly determined in each grain unit, and the steps for determining the correction coefficients K are as follows:

[0021] Step S4.1: Determine the standard channel and the control channel

[0022] A row of grains is randomly determined in each grain unit as a standard channel, which is recorded as B0; and the remaining rows of grains in the grain unit are used as control channels, wherein the rows of grains in the control channel are recorded as B1, B2, B3, ... and Bn-1 respectively;

[0023] Step S4.2: Calculate the average value of the brightness of each row of grains in the standard channel and the control channel

[0024] In the standard channel, calculate the average value LOP0 of the brightness of each grain in row B0;

[0025] In the control channel, the average brightness LOP1 of each grain in row B1 is calculated; the average brightness LOP2 of each grain in row B2 is calculated; the average brightness LOP3 of each grain in row B3 is calculated; and so on, until the average brightness LOPn-1 of each grain in row Bn-1 is calculated;

[0026] Step S4.3: Calculate the correction coefficient K

[0027] In the control channel, the correction coefficient corresponding to row B1 is K1=LOP0 / LOP1; the correction coefficient corresponding to row B2 is K2=LOP0 / LOP2; the correction coefficient corresponding to row B3 is K3=LOP0 / LOP3; and so on, until the correction coefficient corresponding to row Bn-1 is calculated to be Kn-1=LOP0 / LOPn-1.

[0028] In some embodiments, in step S4, the process of correcting the grain brightness using the correction coefficient K is as follows:

[0029] Step S4.4: Correct the brightness difference of the grain channels in each grain unit

[0030] In each grain unit, the average value LOP0 of the brightness of each grain in row B0 of the standard channel is taken as the brightness basis, and the brightness of each row of grains in the control channel is corrected by the correction coefficient K; specifically, the brightness of the grain channel in row B1 is K1*LOP1; the brightness of the grain channel in row B2 is K2*LOP2; the brightness of the grain channel in row B3 is K3*LOP3; and so on, until the brightness of the grain channel in row Bn-1 is calculated to be Kn-1*LOPn-1.

[0031] In some implementation schemes, the testing direction of the LED multi-pin testing machine is reciprocating in the forward direction and the reverse direction along the horizontal axis of the two-dimensional coordinate system.

[0032] In some embodiments, when the test direction of the LED multi-pin tester alternates between the positive direction and the reverse direction of the horizontal axis of the two-dimensional coordinate system, the n groups of probes in the LED multi-pin tester move along the vertical axis of the two-dimensional coordinate system to the next die unit test.

[0033] In some embodiments, each set of probes in the LED multi-pin tester includes two probes. When testing the brightness of a die, the two probes in each set of probes contact the positive electrode and the negative electrode of the die respectively.

[0034] The application of the technical solution of the present invention has at least the following beneficial effects:

[0035] (1) The method for correcting the channel brightness difference of the LED multi-pin tester described in the present invention first constructs a two-dimensional coordinate system for the LED epitaxial wafer; secondly, determines the grain unit; then, tests the grain brightness; finally, uses the correction coefficient K to correct the grain channel brightness difference in each grain unit, so that the MAP distribution of the LED epitaxial wafer brightness that changes in a periodic alternating row interval is corrected to a naturally transitioned MAP, which conforms to the growth characteristics of the epitaxial wafer and ensures the accuracy of the final test results, thereby solving the problem of multi-pin brightness channel differences in the multi-pin tester and avoiding the occurrence of multi-channel brightness deviations.

[0036] (2) The test direction of the LED multi-pin tester used in the present invention is to reciprocate in the forward direction and the reverse direction along the horizontal axis of the two-dimensional coordinate system, which is convenient for saving test time and improving test efficiency.

[0037] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0039] Figure 1 This is a test schematic diagram of an LED multi-pin tester in Embodiment 1 of the present invention (only four die units are shown in the figure);

[0040] Figure 2 is a MAP diagram of the LED epitaxial wafer in Example 1;

[0041] Figure 3 This is a MAP diagram of the LED epitaxial wafer in Comparative Example 1;

[0042] Among them, 1. grain, 2. test direction. DETAILED DESCRIPTION

[0043] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0044] Embodiment 1:

[0045] See also Figure 1 , a method for correcting the brightness difference of channels of an LED multi-pin test machine, comprising the following steps:

[0046] Step S1: Construct a two-dimensional coordinate system

[0047] Before testing, the LED epitaxial wafer is scanned by an LED multi-pin tester, and a two-dimensional coordinate system is constructed based on the scanning results to calculate the coordinate position of each crystal grain 1 on the LED epitaxial wafer. This is convenient for the subsequent "sorting" process to accurately pick out each crystal grain required for the finished product according to the coordinates, and it is also convenient to locate the crystal grains with abnormal brightness.

[0048] Step S2: Determine the grain unit

[0049] The LED multi-pin tester includes n groups of parallel-connected probes, wherein the value n is 4;

[0050] The total number of rows of grains arranged in the vertical axis direction of the LED epitaxial wafer in the two-dimensional coordinate system is recorded as H (because the chip wafer size is fixed to 4 inches and the length and width of the grains are determined according to the design, the value H = the diameter of the chip wafer / the width of the grain), and each row of grains is parallel to the horizontal axis direction of the two-dimensional coordinate system;

[0051] If H is an integer multiple of 4, then H is divided into p grain units in turn, and each grain unit contains n rows of grains;

[0052] If H is an integer multiple of 4 with a remainder, H is divided into p+1 crystal units in sequence, wherein each of the first p crystal units contains 4 rows of crystals; the p+1th crystal unit contains H-4p rows of crystals;

[0053] Step S3: Testing grain brightness

[0054] In the first p die units, starting from the first die unit, four groups of probes in the LED multi-pin tester are used to perform brightness tests on each row of die in each die unit along the horizontal axis direction of the two-dimensional coordinate system (i.e., one group of probes tests one row of die), until the pth die unit is tested;

[0055] In the p+1th die unit, the brightness of each row of the H-4p rows of dies is tested along the horizontal axis direction of the two-dimensional coordinate system using a corresponding number of probes in an LED multi-needle tester;

[0056] Step S4: Correcting grain brightness

[0057] The correction coefficient K is used to correct the brightness difference of the grain channels in each grain unit.

[0058] In step S4, three correction coefficients K are correspondingly determined in each grain unit, and the steps for determining the correction coefficient K are as follows:

[0059] Step S4.1: Determine the standard channel and the control channel

[0060] A row of grains is randomly determined in each grain unit as a standard channel, which is recorded as B0; and the remaining rows of grains in the grain unit are used as control channels, wherein the rows of grains in the control channel are recorded as B1, B2 and B3 respectively;

[0061] Step S4.2: Calculate the average value of the brightness of each row of grains in the standard channel and the control channel

[0062] In the standard channel, calculate the average value LOP0 of the brightness of each grain in row B0;

[0063] In the control channel, the average brightness LOP1 of each grain in row B1 is calculated; the average brightness LOP2 of each grain in row B2 is calculated; the average brightness LOP3 of each grain in row B3 is calculated;

[0064] Step S4.3: Calculate the correction coefficient K

[0065] In the control channel, the correction coefficient corresponding to row B1 is K1=LOP0 / LOP1; the correction coefficient corresponding to row B2 is K2=LOP0 / LOP2; and the correction coefficient corresponding to row B3 is K3=LOP0 / LOP3.

[0066] In step S4, the process of correcting the grain brightness using the correction coefficient K is as follows:

[0067] Step S4.4: Correct the brightness difference of the grain channels in each grain unit

[0068] In each grain unit, the average value LOP0 of the brightness of each grain in row B0 of the standard channel is used as the brightness basis, and the brightness of each row of grains in the control channel is corrected by the correction coefficient K; specifically, the brightness of the grain channel in row B1 is K1*LOP1; the brightness of the grain channel in row B2 is K2*LOP2; and the brightness of the grain channel in row B3 is K3*LOP3.

[0069] The test direction 2 of the LED multi-pin tester is to reciprocate in the positive direction and the reverse direction along the horizontal axis direction of the two-dimensional coordinate system, which is convenient for saving test time and improving test efficiency.

[0070] When the test direction of the LED multi-pin tester alternates between the forward direction and the reverse direction of the horizontal axis of the two-dimensional coordinate system, the four groups of probes in the LED multi-pin tester move along the vertical axis of the two-dimensional coordinate system to the next grain unit test to ensure the continuity of the test.

[0071] Each set of probes in the LED multi-pin tester includes two probes. When testing the brightness of the grain, the two probes in each set of probes contact the positive and negative poles of the grain respectively, and output current to the grain at the same time to make it glow and then test the brightness of the grain to ensure the smooth progress of the test.

[0072] Comparative Example 1:

[0073] The difference from the first embodiment is that step S4 is not provided.

[0074] The grain brightness of the LED epitaxial wafer was tested by the test methods of Example 1 and Comparative Example 1, wherein the test results of Example 1 are shown in Figure 2 , the test results of comparative example 1 are shown in Figure 3 .

[0075] Through Figure 2-3 By comparison, it can be seen that the correction method for the channel brightness difference of the LED multi-pin tester described in Example 1 of the present invention is adopted, that is, the correction coefficient K is used to correct the channel brightness difference of each grain unit, so that the brightness of the LED epitaxial wafer presents a MAP distribution with periodic alternating row interval changes (see the MAP distribution in Comparative Example 1). Figure 3 ) is corrected to a natural transition MAP (see Example 1 Figure 2 ), which conforms to the growth characteristics of the epitaxial wafer, ensures the accuracy of the final test results, thereby solving the problem of multi-pin brightness channel differences in the multi-pin tester and avoiding the situation of multi-channel brightness deviation. Therefore, the present invention can also be applied to the data correction needs of the multi-pin tester of the LED chip factory after mass production.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for correcting channel brightness differences of an LED multi-pin tester, characterized in that: The following steps are involved: Step S1: Construct a two-dimensional coordinate system Before testing, the LED epitaxial wafer is scanned by an LED multi-pin tester, and a two-dimensional coordinate system is constructed based on the scanning results to calculate the coordinate position of each grain on the LED epitaxial wafer; Step S2: Determine the grain unit The LED multi-pin tester includes n groups of parallel-connected probes, wherein the value n is a natural number greater than or equal to 2; The total number of rows of grains arranged in the vertical axis direction of the two-dimensional coordinate system of the LED epitaxial wafer is recorded as H, and each row of grains is parallel to the horizontal axis direction of the two-dimensional coordinate system; If H is an integer multiple of the value n, then H is divided into p grain units in turn, and each grain unit contains n rows of grains; If H is an integer multiple of the value n with a remainder, H is divided into p+1 crystal units in sequence, wherein each crystal unit in the first p crystal units contains n rows of crystals; the p+1th crystal unit contains Hp*n rows of crystals; Step S3: Testing grain brightness In the first p grain units, starting from the first grain unit, n groups of probes in the LED multi-pin tester are used to perform brightness tests on each row of grains in each grain unit along the horizontal axis direction of the two-dimensional coordinate system until the pth grain unit is tested; In the p+1th die unit, the brightness of each row of the Hp*n rows of dies is tested along the horizontal axis direction of the two-dimensional coordinate system using a corresponding number of probes in an LED multi-needle tester; Step S4: Correcting grain brightness The correction coefficient K is used to correct the brightness difference of the grain channels in each grain unit.

2. The method for correcting the channel brightness difference of the LED multi-pin tester according to claim 1 is characterized in that: In step S4, n-1 correction coefficients K are correspondingly determined in each grain unit, and the steps for determining the correction coefficients K are as follows: Step S4.1: Determine the standard channel and the control channel A row of grains is randomly determined in each grain unit as a standard channel, which is recorded as B0; and the remaining rows of grains in the grain unit are used as control channels, wherein the rows of grains in the control channel are recorded as B1, B2, B3, ... and Bn-1 respectively; Step S4.2: Calculate the average value of the brightness of each row of grains in the standard channel and the control channel In the standard channel, calculate the average value LOP0 of the brightness of each grain in row B0; In the control channel, the average brightness LOP1 of each grain in row B1 is calculated; the average brightness LOP2 of each grain in row B2 is calculated; the average brightness LOP3 of each grain in row B3 is calculated; and so on, until the average brightness LOPn-1 of each grain in row Bn-1 is calculated; Step S4.3: Calculate the correction coefficient K In the control channel, the correction coefficient corresponding to row B1 is K1=LOP0 / LOP1; the correction coefficient corresponding to row B2 is K2=LOP0 / LOP2; the correction coefficient corresponding to row B3 is K3=LOP0 / LOP3; and so on, until the correction coefficient corresponding to row Bn-1 is calculated to be Kn-1=LOP0 / LOPn-1.

3. The method for correcting the channel brightness difference of the LED multi-pin tester according to claim 2 is characterized in that: In step S4, the process of correcting the grain brightness using the correction coefficient K is as follows: Step S4.4: Correct the brightness difference of the grain channels in each grain unit In each grain unit, the average value LOP0 of the brightness of each grain in row B0 of the standard channel is taken as the brightness basis, and the brightness of each row of grains in the control channel is corrected by the correction coefficient K; specifically, the brightness of the grain channel in row B1 is K1*LOP1; the brightness of the grain channel in row B2 is K2*LOP2; the brightness of the grain channel in row B3 is K3*LOP3; and so on, until the brightness of the grain channel in row Bn-1 is calculated to be Kn-1*LOPn-1.

4. The method for correcting the channel brightness difference of the LED multi-pin tester according to any one of claims 1 to 3, characterized in that: The testing direction of the LED multi-pin testing machine is to reciprocate in the forward direction and the reverse direction along the horizontal axis direction of the two-dimensional coordinate system.

5. The method for correcting the channel brightness difference of the LED multi-pin tester according to claim 4 is characterized in that: When the test direction of the LED multi-pin tester alternates between the positive direction and the reverse direction of the horizontal axis of the two-dimensional coordinate system, the n groups of probes in the LED multi-pin tester move along the vertical axis of the two-dimensional coordinate system to the next die unit test.

6. The method for correcting the channel brightness difference of the LED multi-pin tester according to claim 5, characterized in that: Each group of probes in the LED multi-pin tester includes two probes. When testing the brightness of a crystal grain, the two probes in each group of probes contact the positive electrode and the negative electrode of the crystal grain respectively.

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