JP2005057069A - Device for detecting deterioration of semiconductor laser, semiconductor laser device having the same, and process for assembling semiconductor laser module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein it is difficult to estimate and detect deterioration in a semiconductor laser causing a device fault and the stop of facilities while using a semiconductor laser device. <P>SOLUTION: A device for detecting deterioration in the semiconductor laser comprises a power supply 2 for laser drive for driving the semiconductor laser 1, a voltage detection 3 for measuring the drive voltage of the semiconductor laser, calculator 4 for calculating the deterioration level of the semiconductor laser by performing specified computation based on a drive voltage value, and a comparator 5 for comparing the deterioration level with a specified reference value. In the device, the quality of the semiconductor laser is judged according to the result of the comparison section. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor laser deterioration detection apparatus.

  In recent years, semiconductor lasers are widely used from consumer equipment such as CDs, DVDs, and laser printers to industrial equipment such as resin welding and metal welding.

  As a conventional semiconductor laser deterioration detection device, the semiconductor laser is detected by calculating the differential efficiency of the semiconductor laser from the measured drive current and optical output and comparing it with the initial differential efficiency stored in advance. (See, for example, Patent Document 1) A light receiving output of a photodetector detected during product inspection is stored as a standard output, and a semiconductor laser is compared by comparing the light receiving output of the photodetector detected during driving with the standard output. There is one that detects deterioration of the image (for example, see Patent Document 2).

  As described above, most apparatuses detect the deterioration of the semiconductor laser based on the monitor value of the drive current, the monitor value of the optical output, or a combination of both.

  The failure of the semiconductor laser can be caused by an increase rate of drive current in APC control (auto power control) that adjusts to a drive current corresponding to a constant optical output value, or ACC control (auto current control) that maintains a constant drive current. It is common to make a judgment based on the light output fluctuation and the light output decrease rate. FIG. 10 is a diagram illustrating a semiconductor laser failure mode during APC control, and FIG. 11 is an explanatory diagram illustrating a semiconductor laser failure mode during ACC control. Semiconductor laser failures are classified into three types as shown in FIGS.

  The type 1 failure is an initial failure caused by a manufacturing process in which a drive current rapidly increases or a light output decreases with a short time laser output. The main factors are defects in manufacturing the semiconductor laser element such as a surface coating defect of the semiconductor laser element and a crystal defect in the active layer.

  The type 2 failure is one in which a function required during a specified period cannot be performed while a device incorporating a semiconductor laser is in use, resulting in an increase in drive current and a decrease in light output. The main factors are minute defects in the surface coating of the semiconductor laser element, minute solder voids when the semiconductor laser element is mounted on the cooling plate (heat sink), and thermal fatigue of the solder part due to intermittent (pulse) operation of the laser device For example, static electricity or overcurrent is applied to the semiconductor laser element.

  Type 3 failures belong to wear failures, where crystal defects inside the semiconductor laser element gradually increase and laser emission efficiency with respect to current injection gradually decreases.

  Of these three types, failure of the semiconductor laser shown as type 1 is generally removed by screening such as burn-in. Further, the failure of the semiconductor laser of type 3 can be avoided by designing so as to compensate for the required device lifetime of the semiconductor laser device.

  Type 2 failures are a major problem because they are difficult to predict and occur during use of the semiconductor laser device. Therefore, it is very important to detect or predict type 2 failures early.

Furthermore, it is desired to remove a semiconductor laser element that is likely to cause a type 2 failure by screening at the manufacturing stage, together with detection of deterioration of the semiconductor laser during use of the semiconductor laser device. On the other hand, screening is performed for each lot before the semiconductor laser is incorporated into the device, and in some cases, all of them are performed, and the ratio of the equipment and man-hours required for inspection to the product manufacturing cost is large, and cost reduction is required. ing.
JP-A-3-183181 JP 2002-319168 A

  In view of the above-mentioned problems of the conventional technology, the problem to be solved by the present invention is to detect the deterioration of the semiconductor laser with high accuracy and prevent the failure of the semiconductor laser device, and the cost of the screening process in the manufacturing stage. An object of the present invention is to provide an apparatus that can achieve reduction.

  In order to solve the above problems, a semiconductor laser degradation detection apparatus according to the present invention includes a power source that drives a semiconductor laser, a voltage detection unit that measures the drive voltage of the semiconductor laser, and a predetermined value based on the drive voltage value. An operation unit that performs an operation to calculate a deterioration level of the semiconductor laser and a comparison unit that compares the deterioration level with a predetermined reference value are provided. With this configuration, it is possible to determine the deterioration of the semiconductor laser and detect the deteriorated semiconductor laser.

  The semiconductor laser device of the present invention includes the semiconductor laser deterioration detection device in order to solve the above-described problems. With this configuration, it is possible to detect deterioration of the semiconductor laser in use and prevent a failure of the semiconductor laser device.

  Furthermore, the semiconductor laser module assembling process of the present invention includes the semiconductor laser deterioration detecting device in order to solve the above-described problems. With this configuration, the quality of the semiconductor laser is judged during product inspection in the manufacturing process of the semiconductor laser module, and the selected good products are screened to detect the deterioration of the semiconductor laser, thereby further ensuring the reliability of the semiconductor laser. Reduced man-hours for the screening process.

  As described above, the present invention estimates the degree of deterioration from the driving voltage of a semiconductor and compares it with a reference value to detect the deterioration of the semiconductor laser. The cost of the screening process at the stage can also be reduced.

  Since the object of the present invention can be achieved by using the structure described in each claim as the main part of the embodiment, the details of one embodiment corresponding to each claim will be described below in Table 1 and FIGS. The embodiment will be described with reference to FIG. 9 together with the effect.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a semiconductor laser deterioration detecting apparatus corresponding to the first aspect of the present invention. In FIG. 1, a configuration that also serves as an operation will be described. A semiconductor laser 1 has a light emitting diode, and emits laser light when power is supplied to a connection terminal. The laser driving power source 2 supplies power to the semiconductor laser 1 to drive the semiconductor laser 1. The voltage detector 3 detects the voltage being driven from the connection terminal of the semiconductor laser 1 and outputs it as a voltage value.

  The calculation unit 4 calculates a deterioration level representing the degree of deterioration of the semiconductor laser 1 using the driving voltage of the semiconductor laser 1 measured by the voltage detection unit 3. The comparison unit 5 compares a predetermined predetermined degradation level as a reference with the degradation level of the semiconductor laser 1 obtained by the calculation unit 4, determines the degradation level of the semiconductor laser 1, and outputs a pass / fail result It is.

  As described above, the invention according to the present embodiment determines the deterioration of the semiconductor laser in accordance with the time-dependent change or transient change of the driving voltage of the semiconductor laser. Due to the nature of voltage measurement, special sensors, adjustments or It is possible to easily and reliably detect the deterioration of the semiconductor laser without requiring maintenance or the like.

  In addition, since there is no need for an optical sensor (for example, a photodiode) that monitors the light output that has been used in the conventional semiconductor laser deterioration detection device, the accompanying lenses, adjustment mechanism, etc., the manufacturing cost of the semiconductor laser device is reduced There is also a big effect in the conversion

(Embodiment 2)
The present embodiment relates to a semiconductor laser deterioration detection apparatus corresponding to the invention described in claim 2. In addition, in this Embodiment, detailed description is abbreviate | omitted about the place which has the structure and effect similar to Embodiment 1, and it demonstrates centering on a different part.

  FIG. 2 is a diagram showing a change with time in optical output when the semiconductor laser is operated. The semiconductor laser used in this embodiment is a high-power type in which light emission spots are arrayed, and cooling of the semiconductor laser element is kept constant by water cooling. The driving condition of the semiconductor laser in this embodiment is a pulse operation in which the laser is turned on for 1 second and the laser is turned off for 1 second. As shown in FIG. 2, under the driving conditions of the present embodiment, the semiconductor laser stopped emitting light in about 1200 hours, resulting in a failure.

  FIG. 3 is a diagram showing the result shown in FIG. 2 as a change with time of the driving voltage in the semiconductor laser. The change with time of the drive voltage shown in FIG. 3 is a plot of the average voltage in a predetermined section when the semiconductor laser is ON. As is apparent from FIG. 3, the leakage current of the junction layer gradually increases with the deterioration of the semiconductor laser, so that the drive voltage gradually decreases. That is, the deterioration of the semiconductor laser can be detected by monitoring the amount of decrease in the drive voltage over time.

Therefore, in the present embodiment, the comparison unit 5 in FIG. 1 uses the decrease amount of 10 mV of the drive voltage as a reference value for determining that the semiconductor laser has deteriorated, and the reference value, the drive voltage V ₀ in the initial state of the semiconductor laser, and the semiconductor laser The calculation unit 4 obtains the difference of the driving voltage V ₁ during use as the deterioration level of the semiconductor laser 1, and the comparison unit 5 sequentially compares the reference value and the deterioration level while using the laser, and the deterioration level increases from the reference value. Therefore, it is determined that the semiconductor laser has deteriorated.

In the above embodiment, the deterioration level of the semiconductor laser is determined by the change of the drive voltage itself, but the present invention is not limited to this. That is, FIG. 4 is a diagram rearranging the drive voltage V ₀ as 100% with respect to the change over time of the drive voltage shown in FIG. If the reference value for determining that the semiconductor laser 1 has deteriorated is 0.6%, the same semiconductor laser deterioration detection as described in FIG. 3 can be performed. Since semiconductor lasers have individual differences depending on lots and the like, the deterioration determination using the ratio shown in FIG. 4 can be used more generally.

In addition, the numerical values shown in the present embodiment are merely described for the purpose of describing the examples, and do not limit the present invention, and are determined according to the semiconductor laser to be used and the driving conditions.

(Embodiment 3)
The present embodiment relates to a semiconductor laser deterioration detection apparatus corresponding to the invention described in claim 3. In addition, in this Embodiment, detailed description is abbreviate | omitted about the place which has the structure and effect similar to Embodiment 1, and it demonstrates centering on a different part.

  FIG. 5 is a diagram showing the change over time in the drive voltage of the same semiconductor laser as in FIG. In FIG. 5, the rate of change of the drive voltage with time in section A is −10 mV per 1000 hours, and the rate of decrease in section B in the vicinity of 1200 hours when the semiconductor laser has failed increases to −30 mV per 1000 hours.

  Therefore, in this embodiment, the rate of change with time of the drive voltage of the semiconductor laser 1 is obtained as the deterioration level of the semiconductor laser by the calculation unit 4 in FIG. 1, and the comparison unit 5 compares it with a predetermined reference value to obtain the reference value. The deterioration of the semiconductor laser is detected by determining that the decrease rate of the drive voltage is larger than that. For example, if the deterioration reference value is set to −25 mV per 1000 hours, the semiconductor laser failure can be detected in the section B before the semiconductor laser fails as shown in FIG.

  It should be noted that the numerical values shown in the present embodiment are described only for the purpose of explaining the examples and do not limit the present invention, and are determined according to the semiconductor laser to be used and the driving conditions.

(Embodiment 4)
The present embodiment relates to a semiconductor laser deterioration detection apparatus corresponding to the invention described in claim 4. In addition, in this Embodiment, detailed description is abbreviate | omitted about the place which has the structure and effect similar to Embodiment 1, and it demonstrates centering on a different part.

  FIG. 6 is a diagram showing a transient change of the drive voltage in the vicinity of the start of irradiation of the semiconductor laser. As shown in FIG. 6, the transient change in the driving voltage takes a peak immediately after the start of irradiation of the semiconductor laser and becomes stable thereafter. In FIG. 6, the drive voltage peak is represented as 100% for the voltage display on the vertical axis. This change characteristic of the driving voltage reflects the deterioration of the semiconductor laser element or the solder mounting state of the element, and when the deterioration progresses or there is a mounting failure, the amount of decrease from the peak value increases.

The drive voltage waveform A indicated by the solid line in FIG. 6 is a normal semiconductor laser, and the voltage drop amount V _A after 30 ms from the peak of the drive voltage was 0.83%. On the other hand, the drive voltage waveform B indicated by the wavy line is a semiconductor laser having microvoids in solder mounting, and the voltage drop V _B after 30 ms from the peak of the drive voltage was 1.02%.

  Therefore, in the present embodiment, the amount of decrease from the peak value of the driving voltage measured immediately after the start of semiconductor laser irradiation by the calculation unit 4 in FIG. 1 is obtained as the deterioration level of the semiconductor laser, and the comparison unit 5 determines a predetermined reference. The deterioration of the semiconductor laser is detected by comparing with the value and determining that the amount of decrease in the drive voltage is larger than the reference value.

In the present embodiment, as shown in FIG. 6, the reference value V _ref for determining the deterioration of the semiconductor laser is 1.0%. Thereby, it is possible to detect the deterioration of the semiconductor laser indicated by the drive voltage waveform B and to determine whether the semiconductor laser is good or bad.

  In the case where a minute void is generated in the mounting solder portion of the semiconductor laser, the failure due to the type 2 shown in FIG. 10 and FIG. 11 may be caused. It is valid. Furthermore, according to the present invention, it is possible to sort non-defective semiconductor lasers in a shorter time than screening that has been performed so far.

(Embodiment 5)
The present embodiment relates to a semiconductor laser deterioration detection apparatus corresponding to the invention described in claim 5. In addition, in this Embodiment, detailed description is abbreviate | omitted about the place which has the structure and effect similar to Embodiment 1, and it demonstrates centering on a different part.

  FIG. 7 is a diagram showing a transient change of the driving voltage in the vicinity of the start of irradiation of the semiconductor laser, and is the same as FIG. A drive voltage waveform A indicated by a solid line in FIG. 7 is a normal semiconductor laser, and a drive voltage waveform B indicated by a broken line is a semiconductor laser having a mounting failure. As is clear from FIG. 7, the change gradients of both waveforms in the section t are different.

  Therefore, in the present embodiment, the change gradient of the drive voltage waveforms A and B is obtained as the deterioration level of the semiconductor laser by the calculation unit 4 in FIG. 1, and the comparison unit 5 compares it with a reference value determined in advance. In this case, the deterioration of the semiconductor laser is detected by determining that the change gradient is large.

  The following (Table 1) shows detection results of semiconductor laser deterioration at the driving voltage of the semiconductor laser shown in FIG.

  In this embodiment, the reference value for determining semiconductor degradation is set to −0.42% per 10 ms. In the table, the semiconductor laser A corresponds to the drive voltage waveform A in FIG. 7 and the semiconductor laser B corresponds to the drive voltage waveform B in FIG. 7, and the change gradients in the section t are −0.36% and −0.47 per 10 ms, respectively. %. As is clear from the results shown in Table 1, the semiconductor laser B having a larger change gradient than the reference value is determined to have deteriorated.

  As described above, according to the present embodiment, it is possible to determine whether or not a semiconductor laser is good by comparing a change gradient after a peak value of a driving voltage measured immediately after the start of irradiation of the semiconductor laser with a predetermined reference value. Furthermore, according to the present embodiment, it is possible to sort non-defective semiconductor lasers in a shorter time than the screening performed so far.

Further, as described in the fourth embodiment, when a small void is generated in the mounting solder portion of the semiconductor laser, the semiconductor laser type 2 shown in FIGS. 10 and 11 may cause a failure. Use of this embodiment in the manufacturing process is effective for sorting before product shipment.

(Embodiment 6)
The present embodiment relates to a semiconductor laser device corresponding to the sixth aspect of the present invention. In addition, in this Embodiment, detailed description is abbreviate | omitted about the place which has the structure and effect similar to Embodiment 1, and it demonstrates centering on a different part.

  FIG. 8 is a block diagram showing a semiconductor laser device according to the present embodiment. The semiconductor laser 6 is supplied with power by a laser driving power supply 8 and is cooled by a laser cooling device 9 to be usable. The laser cooling device 9 refers to a chiller or a Peltier element in the case of water cooling, and may not require a laser cooling device in the case of natural heat dissipation. The semiconductor laser deterioration detection apparatus 7 is one of those described in the first to fifth embodiments, measures the drive voltage from the connection terminal of the semiconductor laser 6, and detects the semiconductor laser deterioration from the calculation result. When a semiconductor laser deterioration is detected, a warning is output.

  According to the present embodiment, the semiconductor laser device can detect the deterioration of the semiconductor laser in use and prevent a device failure in advance. Further, it is possible to easily and reliably detect the deterioration of the semiconductor laser without requiring special sensors, adjustment or maintenance.

(Embodiment 7)
This embodiment relates to a semiconductor laser module assembling process corresponding to the seventh aspect of the invention. In the present embodiment, detailed description of the same configuration and operational effects as those of the first, second, third, fourth, and fifth embodiments will be omitted, and different points will be mainly described.

  FIG. 9 is a flowchart showing the flow of the semiconductor laser module assembly process of the present invention. The manufactured semiconductor lasers are first selected according to the semiconductor laser pass / fail judgment 1 shown in step (indicated as S in the drawing) 10. In this step, the semiconductor laser deterioration detection device described in the fourth embodiment or the fifth embodiment is used.

  Next, in step 11, the semiconductor laser is selected according to the pass / fail judgment result in step 10, and only good products are advanced to step 12 in the next process. In step 12, the non-defective semiconductor laser is further selected using the semiconductor laser pass / fail judgment 2. This step is generally called a screening inspection process, and the semiconductor laser deterioration detection apparatus described in the second or third embodiment is used.

  In the next step 13, the semiconductor lasers are selected according to the pass / fail judgment result in step 12, and only non-defective products are incorporated into the semiconductor laser module shown in the next step 14. Incorporation into a semiconductor laser module refers to attachment of a lens necessary for light collection, mounting to a laser device, stacking for higher output, and the like. The defective semiconductor lasers selected as good in step 11 and step 13 are removed from the semiconductor laser module assembly process in step 15 respectively.

  As described above, according to the present embodiment, it is possible to determine the quality of a semiconductor laser with high accuracy and low cost. The feature of this embodiment is that the pass / fail determination shown in step 10 and step 12 is performed first. That is, according to the semiconductor laser deterioration detection apparatus described in the fourth and fifth embodiments, it is possible to determine the quality in a short time. By performing this before the screening process, a higher-accuracy non-defective product can be obtained. Not only can sorting be performed, but also the cost of the screening process can be reduced.

  The semiconductor laser deterioration detection device of the present invention and the semiconductor laser device and semiconductor laser module assembling process provided with the same can prevent a failure of the semiconductor laser device and reduce the cost of the screening process in the manufacturing stage. The present invention can be applied to semiconductor laser deterioration detection and a semiconductor laser device and semiconductor laser module assembly process.

The block diagram which shows the semiconductor laser degradation detection apparatus in Embodiment 1-5 of this invention The figure which shows the time-dependent change of the optical output of the semiconductor laser degradation detection apparatus in the same Embodiment 2. The figure which shows the time-dependent change of the drive voltage of the semiconductor laser degradation detection apparatus in the same Embodiment 2, and the degradation detection method of a semiconductor laser The figure which shows the other example of the time-dependent change of the drive voltage of the semiconductor laser degradation detection apparatus in the Embodiment 2, and the degradation detection method of a semiconductor laser. The figure which shows the time-dependent change of the drive voltage of the semiconductor laser degradation detection apparatus in the same Embodiment 3, and the degradation detection method of a semiconductor laser The figure which shows the transition change of the drive voltage of the semiconductor laser degradation detection apparatus in the same Embodiment 4, and the degradation detection method of a semiconductor laser The figure which shows the transition change of the drive voltage of the semiconductor laser degradation detection apparatus in the same Embodiment 5, and the degradation detection method of a semiconductor laser Block diagram showing a semiconductor laser device according to a sixth embodiment of the present invention The flowchart which shows the flow of operation | movement of the semiconductor laser module assembly process in Embodiment 7 of this invention. Explanatory drawing showing a semiconductor laser failure mode during APC control Explanatory drawing showing the semiconductor laser failure mode during ACC control

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 6 Semiconductor laser 2, 8 Laser drive power supply 3 Voltage detection part 4 Calculation part 5 Comparison part 7 Semiconductor laser deterioration detection apparatus

Claims (7)

  A semiconductor laser having at least a light emitting diode, a power source for driving the semiconductor laser, a voltage detector for measuring a driving voltage of the semiconductor laser, and performing a predetermined calculation based on the driving voltage value, A semiconductor laser deterioration detection apparatus comprising: an arithmetic unit that calculates a deterioration level; and a comparison unit that compares the deterioration level with a predetermined reference value, and determines whether the semiconductor laser is good or bad based on a result of the comparison unit.   The deterioration level is the difference between the drive voltage at the time of irradiation of the semiconductor laser and the drive voltage measured at the time of new operation or normal operation of the semiconductor laser, and by comparing the deterioration level with a predetermined reference value, 2. The semiconductor laser deterioration detection device according to claim 1, wherein the quality determination is performed.   2. The semiconductor laser deterioration detection apparatus according to claim 1, wherein the deterioration level is a rate of change of the drive voltage with time at the time of irradiation of the semiconductor laser, and the quality of the semiconductor laser is determined by comparing a predetermined reference value with the deterioration level. .   The deterioration level is a reduction amount from the peak value of the drive voltage measured immediately after the start of irradiation of the semiconductor laser, and the quality determination of the semiconductor laser is performed by comparing the deterioration level with a predetermined reference value. The semiconductor laser deterioration detection apparatus as described.   The deterioration level is a change gradient after the peak value of the drive voltage measured immediately after the start of irradiation of the semiconductor laser, and the quality of the semiconductor laser is determined by comparing the predetermined reference value with the deterioration level. The semiconductor laser deterioration detection apparatus as described.   A semiconductor laser device comprising the semiconductor laser deterioration detection device according to claim 1.   4. The semiconductor laser according to claim 2 or 3, wherein the semiconductor laser deterioration detecting device according to claim 4 or 5 is first used to determine whether the semiconductor laser is good or bad, and the good / bad determination is good. A semiconductor laser module assembling step, wherein screening is performed using a deterioration detection apparatus and quality is determined.

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