Inspection method

An inspection system is provided, which applies a forward or reverse voltage on a light-emitting device and measures a current thereof respectively before and after temperature rise, and determines whether the device fails according to the fact whether a current difference before and after the temperature rise is larger than a failure current determination value. Alternatively, the inspection system adopts a current applying device to apply a forward and reverse current on a light-emitting device and measures a voltage difference thereof respectively before and after temperature rise, and determines whether the device fails according to the fact whether a difference of the voltage differences before and after the temperature rise is larger than a failure voltage determination value. Alternatively, the inspection system adopts a predetermined inspecting step and a rapid inspecting step respectively to determine whether a light-emitting device fails. An inspection method for the inspection system is also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 100100062, filed Jan. 3, 2011. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

TECHNICAL FIELD

The disclosure relates to an inspection method, and more particularly to an inspection method for inspecting a die quality of a light-emitting device.

BACKGROUND

The quality and lifespan testing method of the light-emitting diode (LED) has become a hot topic discussed worldwide in recent years. Among others, the Illuminating Engineering Society of North America (IESNA) completed a method for measuring lumen maintenance of LED light sources (LM-80-08) in September 2008 and proposed a set of specifications for the lifespan testing method of the LED device, array and module.

According to the content of the specifications, the lifespan testing of the LED consumes a lot of resources and time, so the manufacturers normally screen the early decaying samples by performing the quality verification and short-term aging testing according to the basic factory specification. However, currently, there is no rapid inspection method for reducing and even omitting the shot-term aging testing step and time before the outgoing of the LED device, thus causing the increase of the manufacturing process and cost. Therefore, it is in need of an online rapid inspection mechanism and method to design and construct a highly efficient measuring platform to provide significant benefits for improving the quality and reliability of the domestic LEDs.

SUMMARY

The disclosure provides an inspection method applied to inspect a die quality of at least one light-emitting device. The inspection method at least includes the following steps. A voltage is applied on the at least one light-emitting device at a first temperature. A first current of the at least one light-emitting device under the applied voltage is measured at the first temperature. The at least one light-emitting device is heated from a first temperature to a second temperature. Then, a voltage is applied on the at least one light-emitting device at the second temperature. A second current of the at least one light-emitting device under the applied voltage is measured at the second temperature. It is determined whether a difference between the second current and the first current is larger than a failure current determination value, and if the difference between the second current and the first current is larger than the failure current determination value, the at least one light-emitting device is determined to be a failed device.

The disclosure also another provides an inspection method applied to inspect a die quality of at least one light-emitting device. The inspection method at least includes the following steps. A forward current and a reverse current are applied on the at least one light-emitting device respectively at different time at a first temperature by a current applying device. A first forward voltage and a first reverse voltage of the at least one light-emitting device respectively under the forward current and the reverse current are measured at different time at the first temperature, in which a difference between the first forward voltage and the first reverse voltage is defined as a first voltage difference. The at least one light-emitting device is heated from the first temperature to a second temperature. Then, the forward current and the reverse current are applied on the at least one light-emitting device respectively at different time at the second temperature by the current applying device. A second forward voltage and a second reverse voltage of the at least one light-emitting device respectively under the forward current and the reverse current are measured at different time at the second temperature, in which a difference between the second forward voltage and the second reverse voltage is defined as a second voltage difference. It is determined whether a difference between the second voltage difference and the first voltage difference is larger than a failure voltage determination value, and if the difference between the second voltage difference and the first voltage difference is larger than the failure voltage determination value, the at least one light-emitting device is determined to be a failed device.

The disclosure further another provides an inspection method, which at least includes the following steps. An unfailed die and a failed die are provided. A predetermined inspection pulse current is applied on the unfailed die and the failed die respectively in a predetermined inspection time to obtain a current to voltage relation for distinguishing the unfailed die and the failed die, and a pulse damage current is defined when a current to voltage relation of the unfailed die and the failed die under the predetermined inspection pulse current is deviated from a linear relation. A failure voltage determination value is defined according to the measured current to voltage relation. A rapid inspection pulse current is applied on a die of at least one light-emitting device in a rapid inspection time, in which the rapid inspection pulse current is smaller than the pulse damage current. A voltage of the at least one light-emitting device is measured when the rapid inspection pulse current is applied thereon. It is determined that the at least one light-emitting device is a failed device when the voltage value is larger than the failure voltage determination value.

In view of the above, according to the embodiments of the disclosure, the inspection system adopts the voltage applying device to respectively apply the forward or reverse voltage on the light-emitting device before and after the temperature rise and measures the current thereof, and determines whether the device fails according to the fact whether the current difference before and after the temperature rise is larger than the failure current determination value. Alternatively, the inspection system adopts the current applying device to respectively apply the forward and reverse current on the light-emitting device before and after the temperature rise and measures the voltage difference thereof before and after the temperature rise, and determines whether the device fails according to the fact whether the difference between the voltage differences before and after the temperature rise is larger than the failure voltage determination value. Alternatively, the inspection system adopts the predetermined inspecting step and the rapid inspecting step respectively to determine whether the light-emitting device fails. The disclosure further provides the inspection method applicable for the inspection system.

Several exemplary embodiments accompanied with figures are described in detail below to further describe the invention in details.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

The First Embodiment

FIG. 1is a schematic view illustrating electrical connection of an inspection system according to a first embodiment of the disclosure,FIG. 2is a relation diagram illustrating a voltage output by a voltage applying device and a current measured by a current inspection device for a light-emitting device inFIG. 1respectively relative to time, andFIG. 3AandFIG. 3Bare current to voltage curve diagrams of inspecting a die quality by using the inspection system inFIG. 1respectively. Referring toFIG. 1, the inspection system100of this embodiment is capable of determining the die quality of at least one light-emitting device101in a short time (e.g., several minutes), thereby reducing the manufacturing cost and time of the product. For example, generally, in the testing of the die quality of the light-emitting device, a 1000-hour continuous probing measurement experiment is performed, and if the die after undergoing the 1000-hour continuous probing measurement experiment still maintains a certain luminance, the light-emitting device is determined to be a normal device; otherwise, the light-emitting device is determined to be a failed device. Besides, currently, a rapid inspection method includes performing a 72-hour accelerated aging experiment to find out the failed device after the 1000 hours; however, the inspection time of this method is still too long.

In view of the above, this embodiment provides the inspection system100for rapidly inspecting the die quality of the light-emitting device101. The inspection system100includes a voltage applying device110, a current inspection device120, a heating device130and a control unit140, as shown inFIG. 1. The voltage applying device120is electrically connected to the at least one light-emitting device101and applies a voltage on the at least one light-emitting device101. The current inspection device120is electrically connected to the at least one light-emitting device101and measures a current generated by the light-emitting device101under the voltage applied by the voltage applying device110. In this embodiment, the voltage applying device110is, for example, a voltage source for applying the voltage on the light-emitting device101, and the current inspection device120is, for example, a current meter for measuring the current generated by the light-emitting device101under the applied voltage. The voltage applied by the voltage applying device110is a forward voltage and/or a reverse voltage. In addition, the current meter of this embodiment is a rapid and high-resolution current meter, in which the current resolution should be smaller than 1 nA and smaller than 1 pA, so as to achieve an inspection accuracy.

In this embodiment, if the voltage applied by the voltage applying device110on the light-emitting device101is the forward voltage, the current inspection device120measures the forward current correspondingly; on the contrary, if the voltage applied by the voltage applying device110on the light-emitting device101is the reverse voltage, the current inspection device120measures the reverse current correspondingly. In this embodiment, the voltage may be a pulse voltage or a direct current (DC) voltage, and a time period in which the voltage applying device110applies the voltage on the at least one light-emitting device101is defined as a voltage sustaining time td1. In addition, a time period in which the current inspection device120measures the current of the at least one light-emitting device101is defined as a current measuring time td2, and the current measuring time td2is smaller than or equal to the voltage sustaining time td1, as shown inFIG. 2. In this embodiment, the voltage sustaining time td1should be smaller than 100 μs and between 10 μs to 50 μs, so as to avoid causing the thermal effect and influencing the measurement result.

The heating device130is used for heating the at least one light-emitting device101from a first temperature T1to a second temperature T2. When the at least one light-emitting device101is at the first temperature T1, the current, generated by the at least one light-emitting device101under the voltage applied by the voltage applying device110, measured by the current inspection device120is defined as a first current; while when the at least one light-emitting device101is at the second temperature T2, the current, generated by the at least one light-emitting device101under the voltage applied by the voltage applying device110, measured by the current inspection device120is defined as a second current. In this embodiment, the second temperature T2falls within a range of 70° C. to 400° C., and falls within a range of 100° C. to 300° C. to avoid damage to the die.

The current to voltage curves L101and L102inFIG. 3Aare measured when the light-emitting device101are respectively an unfailed die and a failed die at the first temperature (e.g., 300 K) at the forward voltage. It can be seen fromFIG. 3Athat, the current to voltage curves L101and L102cannot be effectively distinguished from each other at the room temperature. Therefore, the inspection device100of this embodiment uses the heating device130to heat the light-emitting device101from the first temperature T1to the second temperature T2. The current to voltage curves L103and L104inFIG. 3Aare then measured when the light-emitting device101are respectively an unfailed die and a failed die at the second temperature (e.g., 400 K) at the forward voltage. In this embodiment, when the voltage applied by the voltage applying device110is the forward voltage, the forward voltage falls within a range between 0 to 3.5 V before the range where the voltage and the current are deviated from a linear relation.

InFIG. 3A, the current difference ΔI1is the difference between measured current values of unfailed die before and after the temperature rise when the voltage is 1.5 V, and ΔI2is the difference between measured current values of failed die before and after the temperature rise when the voltage is 1.5 V. After comparing the current differences ΔI1and ΔI2, it can be found that the current difference ΔI2of the failed die is apparently larger than the current difference ΔI1of the unfailed die. However, according to different categories and sizes of the die, the current difference ΔI2of the failed die is not always apparent under the forward voltage, so that in order to increase the precision of the die quality inspection, the current difference is measured before and after the temperature rise when the reverse voltage is applied, as shown inFIG. 3B, and the relevant descriptions are given below.

The current to voltage curves L105and L106inFIG. 3Bare measured when the light-emitting device101are respectively an unfailed die and a failed die at the first temperature (e.g., 300 K) at the reverse voltage. It can be seen fromFIG. 3Bthat, the current to voltage curves L105and L106cannot be effectively distinguished from each other at the room temperature. Likewise, the heating device130is used to heat the light-emitting device101from the first temperature T1to the second temperature T2. The current to voltage curves L107and L108inFIG. 3Aare then measured when the light-emitting device101are respectively an unfailed die and a failed die at the second temperature (e.g., 400 K) at the reverse voltage. In this embodiment, when the voltage applied by the voltage applying device110is the reverse voltage, the range of the reverse voltage needs to be smaller than a breakdown voltage of the at least one light-emitting device101, in which the breakdown voltage differs in accordance with different device structures.

InFIG. 3B, the current difference ΔI1is the difference between measured current values of unfailed die before and after the temperature rise when the voltage is −5 V, and ΔI2is the difference between measured current values of failed die before and after the temperature rise when the voltage is −5 V. After comparing the current differences ΔI1and ΔI2, it can be found that the current difference ΔI2of the failed die is apparently larger than the current difference ΔI1of the unfailed die.

In view of the above, the user can make statistics respectively on the current differences ΔI1and ΔI2of the unfailed die and the failed die before and after the temperature rise by sampling multiple measure values of unfailed dies and failed dies, so as to obtain a failure current determination value ΔI, in which the applied voltage is the forward voltage or the reverse voltage, and the failure current determination value ΔI changes accordingly. In this embodiment, the failure current determination value is generally increased with the rise of the second temperature T2. That is, a higher temperature may result in more apparent changes of the electrical performance of the failed die at the early stage, thereby obtaining a better distinguishing effect. However, to avoid damage to the die caused by the excessive rise of the temperature in the testing, the second temperature T2is at least smaller than 400° C.

In other words, when the die quality inspection of the light-emitting device101is performed, the voltage (the forward voltage and/or the reverse voltage) is firstly applied on the light-emitting device101, and the corresponding current is measured at the same time. Then, the current to voltage relation of the light-emitting device101after the temperature rise is measured. Afterward, it is determined whether the light-emitting device101is a failed device according to the fact whether the current difference of the light-emitting device101before and after the temperature rise is larger than the failure current determination value ΔI, in which the failed device normally refers to the light-emitting device101that fails to pass the common 1000-hour continuous probing measurement experiment, that is, the device probably has defects like early decaying.

In addition, the control unit140is electrically connected to the voltage applying device110and the current inspection device120, and used for controlling the voltage applied by the voltage applying device110and recording the first current and the second current measured by the current inspection device120before and after the temperature rise. In this embodiment, if the difference between the second current and the first current of the inspected light-emitting device101is larger than the failure current determination value, the control unit140determines that the light-emitting device101is a failed device.

The voltage applying device110and the current inspection device120of this embodiment may be a Source Measure Unit (SMU) instrument that integrates the voltage applying device110and the current inspection device120, such as the product of Keithley 236. In this embodiment, the SMU instrument is capable of synchronously outputting and measuring the voltage or current, that is, integrating the voltage source and the current meter, and the implementing circuit is as shown inFIG. 3C. In other words, the instrument that integrates the voltage applying device110and the current inspection device120may be used for outputting or measurement in automatic testing.

The control unit140of this embodiment is the LabVIEW software added to the Keithley 236. The control unit140is used for controlling the voltage applying device110and the current inspection device120. The instrument that integrates the voltage applying device110and the current inspection device120is taken as an example, and this instrument normally has a connection port like GPIB, USB, IEEE1394, MODBUS, serial port or parallel port for the user to operate and read the measurement values through the control unit140. That is, in a computer host, the LabVIEW software enables the user to control the instrument to supply the voltage or the current through the operations of the computer host and read the values detected by the instrument.

In other embodiments, the voltage applying device110and the current inspection device120are also separated independent electronic devices, that is, the voltage applying device110may be merely the voltage source and the current inspection device120may be merely the current meter.

Besides, the inspection system100of this embodiment may different implementing methods by using different heating devices, such as the inspection systems100ato100eas shown inFIG. 4AtoFIG. 4E, and the relevant descriptions are given below.

In the inspection system100aofFIG. 4A, the heating device130is, for example, a heating platform130afor heating the light-emitting device101from the first temperature T1to the second temperature T2, in which the heating platform is, for example, a TE-Cooler or Hot-plate. In addition, in the inspection system100bofFIG. 4B, the heating device130is, for example, an oven130bfor heating the light-emitting device101from the first temperature T1to the second temperature T2, in which the light-emitting device101is placed in the oven130b.

In the inspection system100cofFIG. 4C, the heating device130is, for example, a microwave device130cfor heating the light-emitting device101from the first temperature T1to the second temperature T2, in which the microwave device130cmay emit a microwave W1for raising the temperature of the light-emitting device101. In addition, in the inspection system100dofFIG. 4D, the heating device130is, for example, a power supply device130dfor heating the light-emitting device101from the first temperature T1to the second temperature T2, in which the power supply device130duses the current to heat the light-emitting device101.

In the inspection system100eofFIG. 4E, the heating device130is, for example, a laser device130efor heating the light-emitting device101from the first temperature T1to the second temperature T2, in which the laser device130eis applied to provide a laser beam L1on the light-emitting device101, for heating the light-emitting device101from the first temperature T1to the second temperature T2. In this embodiment, the wavelength range of the laser beam L1is larger than or equal to the main light-emitting wavelength of at least one light-emitting device101, and thus the energy of the laser beam L1is mostly converted into the energy for heating the light-emitting device101.

In the inspection systems100ato100eofFIG. 4AtoFIG. 4E, the control unit140is, for example, a computer. The computer is electrically connected to the voltage applying device110and the current inspection device120, and controls the voltage output by the voltage applying device110and records the current inspected by the current inspection device120. To realize automatic inspection, the control unit140is also optionally electrically connected to the heating device130(e.g., the computer), and thus the voltage applying device110, the current inspection device120and the heating device130may be directly controlled by operating the computer, thereby achieving the purpose of automatic inspection. The inspection systems100ato100ecapable of automatically inspecting the die quality as shown inFIG. 4AtoFIG. 4Eare exemplary, and are not intended to limit the scope of the disclosure.

In view of the above description, this embodiment also provides an inspection method applied to inspect a die quality of at least one light-emitting device.

The inspection method at least includes the following steps. The above-mentioned voltage is applied on the light-emitting device101at the first temperature T1. A first current generated by the light-emitting device101under the applied voltage is measured at the first temperature T1. The heating light-emitting device101is heated from the first temperature T1to the second temperature T2. Then, a voltage is applied on the light-emitting device101at the second temperature T2. A second current generated by the light-emitting device101under the applied voltage is measured at the second temperature T2. If the difference between the second current and the first current is larger than the failure current determination value ΔI, the light-emitting device101is determined to be a failed device.

In this inspection method, the light-emitting device101may be heated by using an oven, a laser device, a microwave device, a heating platform or by a current as described above. In this embodiment, when the light-emitting device101is heated by using the oven, the light-emitting device101is heated from the first temperature T1to the second temperature T2through hot air convection or a high temperature bulb.

The Second Embodiment

FIG. 5is a schematic view illustrating electrical connection of an inspection system according to a second embodiment of the disclosure,FIG. 6Ais a relation diagram illustrating a current output by a current applying device and a voltage measured by a voltage inspection device for a light-emitting device inFIG. 5respectively relative to time, andFIG. 7is a current to voltage curve diagram of inspecting a die quality by using the inspection system inFIG. 5. Referring toFIG. 5, the inspection system200of this embodiment may also determine the die quality of the at least one light-emitting device101in a short time (e.g., several minutes), thereby reducing the manufacturing cost and time of the product.

This embodiment provides the inspection system200for rapidly inspecting the die quality of the light-emitting device101. The inspection system200includes a current applying device210, a voltage inspection device220, a heating device230and a control unit240, as shown inFIG. 5. The current applying device210is electrically connected to the at least one light-emitting device101, and applies a forward current and a reverse current on the light-emitting device101respectively at different time. The voltage inspection device220is electrically connected to the light-emitting device101, and measures a forward voltage and a reverse voltage respectively generated by the light-emitting device101under the forward current and the reverse current applied by the current applying device210. In this embodiment, the current applying device210is, for example, a current source for applying the current on the light-emitting device101, and the voltage inspection device220is, for example, a voltmeter for measuring the voltage generated by the light-emitting device101under the applied current, in which the current applied by the current applying device210is the forward current and the reverse current.

In this embodiment, if the current applied by the current applying device210on the light-emitting device101is the forward current, the voltage inspection device220measures the forward voltage correspondingly; on the contrary, if the current applied by the current applying device210on the light-emitting device101is the reverse current, the voltage inspection device220measures the reverse voltage correspondingly. In this embodiment, the forward current and the reverse current are respectively a transient current, and the time in which the current applying device210respectively applies the forward current and the reverse current on the light-emitting device101may be respectively defined as a forward current sustaining time td1and a reverse current sustaining time td3, as shown inFIG. 6A. In this embodiment, the forward current sustaining time td1and the reverse current sustaining time td3are between 10 μs to 50 μs, to avoid causing the thermal effect and influencing the measurement result. In addition, an interval between the forward current sustaining time td1and the reverse current sustaining time td3is defined as an interval time td2, in which the interval time td2is 1 msec to 10 msec, as shown inFIG. 6A.

In addition, the heating device230is used for heating the light-emitting device101from the first temperature T1to the second temperature T2. When the light-emitting device101is at the first temperature T1, the voltage inspection device220measures a first forward voltage FV1and a first reverse voltage RV1respectively generated by the light-emitting device101under the forward current and the reverse current applied by the current applying device210, and a difference between the first forward voltage FV1and the first reverse voltage RV1is defined as a first voltage difference ΔV1. When the light-emitting device101is at the second temperature T2, the voltage inspection device220measures a second forward voltage FV2and a second reverse voltage RV2respectively generated by the light-emitting device101under the forward current and the reverse current applied by the current applying device210, and a difference between the second forward voltage FV2and the second reverse voltage RV2is defined as a second voltage difference ΔV2. In this embodiment, the second temperature T2falls within a range of 70° C. to 400° C., and falls within a range of 100° C. to 300° C. to avoid damage to the die.

In this embodiment, the time period in which the voltage inspection device220measures the first forward voltage FV1or the second forward voltage FV2of the light-emitting device101is defined as a first voltage measuring time td4, and the first voltage measuring time td4is smaller than or equal to the forward current sustaining time td1. Besides, the time period in which the voltage inspection device220measures the first reverse voltage RV1or the second reverse voltage RV2of the light-emitting device101is defined as a second voltage measuring time td5, and the second voltage measuring time is smaller than or equal to the reverse current sustaining time, as shown inFIG. 6A.

Moreover, inFIG. 7, the current to voltage curves L201and L202are measured when the light-emitting device101is the failed die respectively at the first temperature (e.g., 25° C.) and the second temperature (e.g., 110° C.), and the current to voltage curves L203and L204are measured when the light-emitting device101is the unfailed die respectively at the first temperature and the second temperature. In the curves L201and L202ofFIG. 7, under the same current (e.g., 1 nA), the voltage differences of the failed die at the first and second temperature are ΔV1and ΔV2respectively, and the voltage differences of the unfailed die at the first and second temperature are ΔV3and ΔV4respectively. Similar to the concept of the first embodiment, a difference of the voltage differences ΔV1−ΔV2of the failed die is apparently larger than a difference of the voltage differences ΔV3−ΔV4of the unfailed die.

Therefore, based on the concept and principle of the first embodiment, likewise, the user may also make statistics respectively on the differences of the voltage differences ΔV1−ΔV2and ΔV3−ΔV4of the unfailed die and the failed die by sampling the measure values of multiple unfailed dies and failed dies, so as to obtain a failure voltage determination value ΔV, in which the failure voltage determination value ΔV changes according to different categories and sizes of the die. In this embodiment, the failure voltage determination value is generally increased with the rise of the second temperature T2. That is, a higher temperature may result in more apparent changes of the electrical performance of the failed die at the early stage, thereby obtaining a better distinguishing effect. However, to avoid damage to the die caused by the excessive rise of the temperature in the testing, the second temperature T2is at least smaller than 400° C.

In other words, when the die quality inspection of the light-emitting device101is performed, the forward current and the reverse current are respectively applied on the light-emitting device101, and the corresponding voltage difference ΔV1is measured at the same time. Then, the current to voltage relation of the measuring light-emitting device101after the temperature rise is measured. Afterward, it is determined whether the light-emitting device101is a failed device according to the fact whether the difference of the voltage differences ΔV1−ΔV2of the light-emitting device101is larger than the failure voltage determination value ΔV, in which the failed device normally refers to the light-emitting device101that fails to pass the common 1000-hour continuous probing measurement experiment, that is, the device probably has defects like early decaying.

The control unit240is electrically connected to the current applying device210and the voltage inspection device220, and used for controlling the forward current and the reverse current applied by the current applying device210and recording the first voltage difference ΔV1and the second voltage difference ΔV2measured by the voltage inspection device220respectively at the first temperature and the second temperature. In this embodiment, if a difference ΔV1−ΔV2between the first voltage difference ΔV1and the second voltage difference ΔV2is larger than the failure voltage determination value ΔV, the control unit240determines that the at least one light-emitting device is a failed device.

Similarly, the current applying device210and the voltage inspection device220of this embodiment may also be an SMU instrument that integrates the current applying device210and the voltage inspection device220, such as the aforementioned product of Keithley 236. In this embodiment, the SMU instrument is capable of synchronously outputting and measuring the voltage or current, that is, integrating the current source and the voltmeter, and the implementing circuit is as shown inFIG. 6B. In other words, the instrument that integrates the current applying device210and the voltage inspection device220may also be used for outputting or measurement in automatic testing.

Similarly, the control unit240of this embodiment is the LabVIEW software added to the Keithley 236. The control unit240is used for controlling the current applying device210and the voltage inspection device220. The instrument that integrates the current applying device210and the voltage inspection device220is taken as an example, and this instrument normally has a connection port like GPIB, USB, IEEE1394, MODBUS, serial port or parallel port for the user to operate and read the measurement values through the control unit240. That is, in a computer host, the LabVIEW software enables the user to control the instrument to supply the voltage or the current through the operations of the computer host and read the values detected by the instrument.

In other embodiments, the integrating current applying device210and the voltage inspection device220are also separated independent electronic devices, that is, the current applying device210may be merely the current source and the voltage inspection device220may be merely the voltmeter.

It should be noted that, the heating device230of this embodiment may, for example, adopt any implementation aspect of the heating device130as described above, so the relevant descriptions will not be given herein again. Besides, the Keithley 236 is, for example, an instrument that integrates the functions of the voltage source, the current source, the voltmeter and the current meter. In other words, the instrument can be directly applied in all the above-mentioned and the following embodiments.

Likewise, in view of the above, this embodiment also provides an inspection method applied to inspect the die quality of the light-emitting device. The inspection method at least includes the following steps. The forward current and the reverse current are respectively applied on the light-emitting device101at different time at the first temperature T1. The first forward voltage FV1and the first reverse voltage RV1respectively generated by the light-emitting device101under the forward current and the reverse current applied by the current applying device210are measured at different time at the first temperature T1, in which the difference between the first forward voltage FV1and the first reverse voltage RV1is defined as the first voltage difference ΔV1. The light-emitting device101is heated from the first temperature T1to the second temperature T2. The forward current and the reverse current are respectively applied on the light-emitting device101at different time at the second temperature T2. The second forward voltage FV2and the second reverse voltage RV2respectively generated by the light-emitting device101under the forward current and the reverse current applied by the current applying device210are respectively measured at different time at the second temperature T2, in which the difference between the second forward voltage FV2and the second reverse voltage RV2is defined as the second voltage difference ΔV2. It is determined whether the difference ΔV1−ΔV2between the first voltage difference ΔV1and the second voltage difference ΔV2is larger than the failure voltage determination value ΔV, and if the difference ΔV1−ΔV2between the first voltage difference ΔV1and the second voltage difference ΔV2is larger than the failure voltage determination value ΔV, the light-emitting device101is determined to be a failed device.

Likewise, in this inspection method, the method for heating the light-emitting device101may refer to the method disclosed in the first embodiment, and the details will not be repeated herein.

The Third Embodiment

FIG. 8is a schematic view illustrating electrical connection of an inspection system according to a third embodiment of the disclosure, andFIG. 9is a current to voltage curve diagram of inspecting a die quality by using the inspection system in FIG.8. Referring toFIG. 8, the inspection system300of this embodiment also determines the die quality of the at least one light-emitting device101in a short time (e.g., several minutes), thereby reducing the manufacturing cost and time of the product.

This embodiment provides the inspection system300for rapidly inspecting the die quality of the light-emitting device101. The inspection system300includes a pulse current applying device310, a voltage inspection device320and a control unit330. The pulse current applying device310is electrically connected to the light-emitting device101, and respectively sequentially applies a predetermined inspection pulse current in a predetermined inspection time and a rapid inspection pulse current in a rapid inspection time on the light-emitting device101.

The predetermined inspection current is applied on the unfailed die and the failed die of the light-emitting device101respectively in the predetermined inspection time, and thus curves C301and C302as shown inFIG. 9are obtained, in which the curves C301and C302respectively represent the current to voltage relations of the unfailed die and the failed die, and the unfailed die and the failed die of the light-emitting device101may be screened in advance through a long-time time probing measurement procedure. It can be found in the curves C301and C302that, the unfailed die and the failed die can be distinguished when a large current (e.g., a current larger than or equal to a rated operating current (e.g., 0.3 A)) is applied. It should be noted that, the pulse time of applying the predetermined inspection pulse current is smaller than 5 sec, so as to prevent the heat dissipation condition in the testing system from influencing the voltage measurement, and the time length of the pulse current can be adjusted in accordance with different testing samples.

In addition, the voltage inspection device320is electrically connected to the light-emitting device101, and measures the first voltage generated by the light-emitting device101in the predetermined inspection time. InFIG. 9, when the current is larger than 1.5 A, the current to voltage curve is deviated from a linear relation, thus a pulse damage current could be defined. Taken the example ofFIG. 9, the damage current is 1.5 A. The rapid inspection pulse current in the subsequent inspecting steps needs to be smaller than or equal to the pulse damage current.

In the predetermined inspection time, since the predetermined inspection pulse current is applied on the unfailed die and the failed die in advance, the criterion that in which ranges the pulse current is capable of distinguishing the unfailed die and the failed die is obtained. For example, in the curves C301and C302inFIG. 9of this embodiment, the unfailed die and the failed die can be distinguished when the pulse current is larger than or equal to the rated operating current (e.g., 0.3 A) and is smaller than the pulse damage current (e.g., 1.5 A). Therefore, the pulse current ran is from 0.3 A to 1.5 A. The user can make statistics by sampling measure values of multiple unfailed dies and failed dies to obtain the pulse current range, and accordingly defines a failure voltage determination value in the pulse current range.

Then, in the rapid inspection time, the current applying device210applies a rapid inspection pulse current on the light-emitting device101, and at this time the voltage inspection device320measures the second voltage correspondingly generated by the light-emitting device101, in which the control unit330determines that the light-emitting device101is a failed device when the second voltage is higher than the failure voltage determination value. TakenFIG. 9for example, the pulse current range where the unfailed die and the failed die can be effectively distinguished is between 0.3 A to 1.5 A. When the pulse current of 1.3 A is applied on the light-emitting device, if the corresponding voltage value is higher than the voltage value of the unfailed die applied with the same pulse current, the die is determined to be the failed die. In order to improve the die inspection accuracy of the inspection system300, the current to voltage relations of multiple unfailed dies and failed dies need to be sampled, and thus the failure voltage determination value can be set more precisely. In this embodiment, the rapid inspection pulse current is at least larger than or equal to the rated operating current (e.g., 0.3 A).

The pulse current applying device310and the voltage inspection device320of this embodiment may also adopt the SMU instrument which integrates the pulse current applying device310and the voltage inspection device320. In this embodiment, the SMU instrument is capable of synchronously outputting and measuring the voltage or current. In addition, the instrument that integrates the pulse current applying device310and the voltage inspection device320may be used for outputting or measurement in automatic testing.

Likewise, the control unit330of this embodiment is the LabVIEW software added to Keithley 2430. The control unit330is used for controlling the pulse current applying device310and the voltage inspection device320. The instrument that integrates the pulse current applying device310and the voltage inspection device320is taken as an example, and this instrument normally has a connection port like GPIB, USB, IEEE1394, MODBUS, serial port or parallel port for the user to operate and read the measurement values through the control unit330. That is, in a computer host, the LabVIEW software enables the user to control the instrument to supply the voltage or the current through the operations of the computer host and read the values detected by the instrument.

In other embodiments, the pulse current applying device310and the voltage inspection device320may also be separated independent electronic devices, that is, the pulse current applying device310may be merely the current source and the voltage inspection device320may be merely the voltmeter.

In view of the above, this embodiment also provides an inspection method, which at least includes the following steps. The unfailed die and the failed die are provided. The predetermined inspection pulse current is applied on the unfailed die and the failed die respectively in the predetermined inspection time to obtain the current to voltage relation to distinguish the unfailed die and the failed die, and the pulse damage current is defined when the current to voltage relation of the unfailed die and the failed die under the predetermined inspection pulse current is deviated from a linear relation. The failure voltage determination value is defined according to the current to voltage relation for distinguishing the unfailed die and the failed die obtained in the predetermined inspection time. In the rapid inspection time, the rapid inspection pulse current is applied on the die of the at least one light-emitting device101, in which the rapid inspection pulse current is smaller than the pulse damage current. It is determined whether the light-emitting device is a failed device according to the fact whether the voltage value generated when the rapid inspection pulse current is applied on the die of the light-emitting device101is larger than the failure voltage determination value.

In this embodiment, the inspection method further includes defining the current inspection range according to the current to voltage relation for distinguishing the unfailed die and the failed die obtained in the predetermined inspection time, and the rapid inspection pulse current is in the current inspection range. In this embodiment, the current inspection range falls within a range of 0.3 A to 3 A.

In view of the above, the inspection system and the inspection method of the disclosure at least have the following advantages. The inspection system adopts the voltage applying device to respectively apply the forward or reverse voltage on the light-emitting device before and after the temperature rise and measures the current thereof, and determines whether the device fails according to the fact whether the current difference before and after the temperature rise is larger than the failure current determination value. Alternatively, the inspection system adopts the current applying device to respectively apply the forward and reverse current on the light-emitting device before and after the temperature rise and measures the voltage difference thereof before and after the temperature rise, and determines whether the device fails according to the fact whether the difference between the voltage differences before and after the temperature rise is larger than the failure voltage determination value. Alternatively, the inspection system adopts the predetermined inspecting step and the rapid inspecting step respectively to determine whether the light-emitting device fails. The disclosure further provides the inspection method applicable for the inspection system.