JP2006245287A - Inspection method of possibility of degradation failure occurrence in on-vehicle laser diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection method for removing a product with high probability that a degradation failure will occur in a stage before shipping. <P>SOLUTION: Time calculated from a life characteristic of a laser diode, a temperature confirmed from the life characteristic of the laser diode, and an inspection temperature which is set in a product operation guarantee temperature, are substituted for a formula of a mean failure interval. Inspection time is calculated corresponding to the inspection temperature which is set in the production operation guarantee temperature. An acceleration condition is set, and laser light emission from the laser diode is continued for inspection time after an acceleration condition is set, in a state where the laser diode is maintained in the inspection temperature after the acceleration condition is set. It is inspected whether a difference between a current value before inspection of current required for laser light mission just after the laser diode starts laser light emission, and a current value after inspection of current required for laser light emission just before laser light emission is terminated, is within a prescribed range where a regulated production operation can be guaranteed from the characteristic of the laser diode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for inspecting the possibility of a deterioration failure of an in-vehicle laser diode used in, for example, an in-vehicle DVD player.

As an example of a method for manufacturing a laser diode, for example, there is one shown in Patent Document 1 below.
JP 2003-229633 A

  In this type of laser diode, the current value of the current required for the laser diode to emit laser light in a room temperature environment is measured, and the measured current value is defined by the characteristics of the laser diode. Whether or not an initial failure has occurred has been examined by determining whether or not it is within a prescribed range that can guarantee the above.

  By the way, assuming an in-vehicle laser diode used in an in-vehicle DVD player, for example, it is in-vehicle, so compared to an in-vehicle one, vibration is applied or it is left at a high temperature for a long time. Because of the harsh environment, it is necessary to inspect for degradation failures. However, in the past, there is no effective method for inspecting the possibility of occurrence of deterioration failure, and therefore it is not possible to determine the possibility of occurrence of deterioration failure at the stage before product shipment, thus ensuring sufficient quality. It was difficult.

  The present invention has been made in view of the above-described circumstances, and the object thereof is to ensure that sufficient quality can be eliminated at the stage prior to product shipment of products that are likely to cause degradation failures. It is an object of the present invention to provide a method for inspecting the possibility of occurrence of a deterioration failure in a vehicle-mounted laser diode.

  According to the first aspect of the present invention, the time calculated from the life characteristics of the in-vehicle laser diode, the temperature confirmed from the life characteristics of the in-vehicle laser diode, and the inspection temperature set to the product operation guarantee temperature are averaged. A first procedure for calculating an inspection time corresponding to the inspection temperature set as the product operation guarantee temperature by substituting into the formula of the interval, and from the in-vehicle laser diode while maintaining the in-vehicle laser diode at the inspection temperature. A second procedure for continuing laser emission over the inspection time, and a third procedure for measuring a current value of a current necessary for laser emission immediately after the vehicle-mounted laser diode starts laser emission as a pre-inspection current value; A fourth procedure for measuring a current value of a current necessary for laser light emission immediately before the on-vehicle laser diode finishes laser light emission as a post-inspection current value; A fifth procedure for calculating a difference between the pre-inspection current value and the post-inspection current value as a current value change amount, and guaranteeing a product operation in which the current value change amount is defined by the characteristics of the in-vehicle laser diode. And a sixth procedure for determining whether or not it is within the specified range to be obtained, and inspecting the possibility of the occurrence of a deterioration failure.

  As a result, the current value before the inspection of the current required for laser emission immediately after the on-vehicle laser diode starts laser emission and the current required for laser emission immediately before the end of laser emission at the stage before product shipment. Since it is possible to determine whether or not the difference from the current value after the inspection is within a specified range that can guarantee the product operation, it is possible to determine the deterioration failure, so there is a high possibility that the deterioration failure will occur. Products can be eliminated at the stage before product shipment, and sufficient quality can be ensured.

  According to the second aspect of the invention, for the purpose of shortening the inspection time, the inspection temperature set as the product operation guarantee temperature in the first procedure is set as the inspection temperature before the acceleration condition setting and the first The inspection time calculated in step 1 is set as the inspection time before setting the acceleration conditions, and the time shorter than the inspection time before setting the acceleration conditions is set as the inspection time after setting the acceleration conditions, and the relationship between the inspection time and the inspection temperature. The temperature corresponding to the inspection time after setting the acceleration condition is calculated as the inspection temperature after setting the acceleration condition, and the inspection time after setting the acceleration condition and the inspection temperature after setting the acceleration condition are calculated as described above. The second procedure to the sixth procedure are executed.

  As a result, by inspecting according to the inspection time after setting the acceleration condition, which is shorter than the inspection time before setting the acceleration condition, the inspection time (laser emission continues more than when inspecting according to the inspection time before setting the acceleration condition) The total inspection period required to ship the product can be shortened.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a functional block diagram showing the electrical configuration of an in-vehicle DVD player that can be mounted on a vehicle. The in-vehicle DVD player 1 includes a signal processing IC 2, a driver IC 3, a front end processor (FEP) 4, a spindle motor 5, a turntable 6, an optical pickup 7, and a stepping motor 8. The signal processing IC 2 functions as a normal computer, and is configured by providing a bus line for connecting a CPU, RAM, ROM, and I / O. Further, the signal processing IC 2 performs data transfer with the host (navigator ECU) 9 in accordance with the “ATAPI” standard which is one of the data transfer system standards.

  When a control command is input from the signal processing IC 2, the driver IC 2 controls operations of the spindle motor 5, the optical pickup 7, and the stepping motor 8 based on the input control command. When a control command is input from the driver IC 2, the spindle motor 5 integrates the disk 10 and the turntable 6 based on the input control command if the disk 10 is mounted on the turntable 6. And rotating according to a predetermined rotation speed. When a control command is input from the driver IC 2, the stepping motor 8 changes the position (laser irradiation position) of the optical pickup 7 with respect to the disk 10 based on the input control command. The optical pickup 7 has a laser diode (LD) 11 (vehicle-mounted laser diode in the present invention) inside, and emits a laser from the laser diode 11 when a control command is input from the driver IC 2.

  In this case, the laser emitted from the laser diode 11 is emitted from the objective lens 13 after the irradiation angle is changed by the reflecting plate 12 and irradiated onto the disk 10. When the laser emitted from the laser diode 11 is irradiated onto the disk 10 in this way, the data recorded on the disk 10 is read as an optical signal, and the optical signal is received by the laser diode 11. Later, the signal is converted into an analog signal by the front end processor 4, converted from an analog signal to a digital signal by the signal processing IC 2, and transferred to the host 9.

Here, a method for inspecting the possibility of the deterioration failure of the laser diode 11 will be described with reference to FIG.
First, the product operation guarantee temperature is set as the inspection temperature (T2) before the acceleration condition is set (step S1), and the time (t1) calculated from the life characteristics of the laser diode 11 is confirmed from the life characteristics of the laser diode 11. The inspection temperature (T1) and the inspection temperature (T2) before setting the acceleration condition are substituted into the following average failure interval (MTTF) formula, and the inspection time corresponding to the inspection temperature of the product operation guarantee temperature is inspected before the acceleration condition is set. Calculated as time (t2) (step S2). Here, the product operation guarantee temperature is a maximum temperature that guarantees normal operation of the product, and is, for example, “85 ° C.”.

t2 / t1 = exp [(1 / T2-1 / T1) * (Ea / K)]
Ea = 2.54
K = 8.62 * 10 ⁻⁵
Next, it is determined how many times the inspection time is to be increased with respect to the lifetime characteristics of the laser diode 11 (an acceleration multiple is determined). That is, a time shorter than the inspection time (t2) before the acceleration condition setting calculated in this way is set as the inspection time (t2 ′) after the acceleration condition setting (step S3), and the inspection time and the inspection temperature are set. From the relationship, the inspection temperature (T2 ′) after setting the acceleration condition corresponding to the inspection time (t2 ′) after setting the acceleration condition is calculated (step S4). In this case, the inspection time (t2 ′) after setting the acceleration condition is the time for actually emitting the laser from the laser diode 11.

  Next, for example, by leaving the in-vehicle DVD player 1 under the inspection temperature (T2 ′) after setting the acceleration condition, the laser diode 11 is maintained at the inspection temperature (T2 ′) after setting the acceleration condition (step S5). Laser light emission from the laser diode 11 is started (aging is started) (step S6). At this time, the current value of the current necessary for laser light emission immediately after the laser diode 11 starts laser light emission is measured as the pre-inspection current value (I1) (step S7).

  Next, after the inspection time (t2 ′) after the acceleration conditions are set after the laser emission from the laser diode 11 is started (“YES” in step S8), immediately before the laser diode 11 finishes the laser emission. The current value of the current necessary for laser emission is measured as a post-inspection current value (I2) (step S9), and the laser emission from the laser diode 11 is terminated (aging is terminated) (step S10).

  Next, the difference between the pre-inspection current value (I1) and the post-inspection current value (I2) is calculated as a current value change amount (ΔI) (step S11), and the calculated current value change amount (ΔI) is the laser diode 11 It is determined whether or not the product operation is within a specified range that can guarantee the product operation defined from the characteristics (step S12). If the amount of change in current value (ΔI) is within a specified range that can guarantee the product operation specified from the characteristics of the laser diode 11 (“YES” in step S12), there is a possibility that a degradation failure will occur. On the other hand, the current value change amount (ΔI) is not within the specified range that can guarantee the product operation specified from the characteristics of the laser diode 11 (if it is out of the specified range). ("NO" in step S12), it is determined that there is a high possibility that a degradation failure will occur (step S14).

  Through the series of inspections described above, products that are unlikely to cause degradation failures can be separated from those that are likely to cause degradation failures, and degradation failures may occur when products are shipped. Therefore, it is possible to eliminate products with a high value, and it is possible to ship only products that are less likely to cause deterioration failures.

  As described above, according to the present embodiment, the time (t1) calculated from the lifetime characteristics of the laser diode 11, the temperature (T1) confirmed from the lifetime characteristics of the laser diode 11, and the product operation guaranteed temperature are set. The inspection temperature (T2) is substituted into the average failure interval equation, the inspection time (t2) corresponding to the inspection temperature (T2) set as the product operation guarantee temperature is calculated, the acceleration condition is set, and the laser diode 11 Is maintained at the inspection temperature (T2 ′) after setting the acceleration condition, and laser light emission from the laser diode 11 is continued for the inspection time (t2 ′) after setting the acceleration condition, and immediately after the laser diode 11 starts laser light emission. The difference between the current value (I1) before inspection of the current necessary for laser emission at the current and the current value (I2) after inspection of the current necessary for laser emission immediately before the end of laser emission It is determined whether or not the current value change amount (ΔI) is within the specified range that can guarantee the product operation specified from the characteristics of the laser diode 11, and the possibility of the occurrence of the deterioration failure is inspected. did.

  Thereby, in the stage before product shipment, the current value (I1) before inspection of the current necessary for laser light emission immediately after the laser diode 11 starts laser light emission and the laser light emission just before the laser light emission is finished. Deterioration failure occurs because it is possible to determine whether or not the difference from the current value (I2) after the current inspection is within a specified range in which product operation can be guaranteed, and the possibility of deterioration failure occurs. Products that are likely to be removed can be eliminated at the stage before product shipment, and sufficient quality can be ensured.

  In this case, the acceleration condition is set for the purpose of shortening the inspection time, and the inspection is performed according to the inspection time (t2 ') after the acceleration condition is set. Compared with the case of inspecting according to (t2), the inspection time (time for continuing laser emission) can be shortened, and the entire inspection period required until product shipment can be shortened.

The present invention is not limited to the above-described embodiment, and can be modified or expanded as follows.
If there is a sufficient margin in the inspection period, the inspection may be performed according to the inspection time (t2) before setting the acceleration condition without setting the acceleration condition.

The figure which shows one Embodiment of this invention and shows the procedure of a test | inspection Functional block diagram showing the electrical configuration of the in-vehicle DVD player

Explanation of symbols

In the drawings, reference numeral 11 denotes a laser diode (vehicle-mounted laser diode).

Claims (2)

Substitute the time calculated from the life characteristics of the in-vehicle laser diode, the temperature confirmed from the life characteristics of the in-vehicle laser diode, and the inspection temperature set as the product operation guarantee temperature into the formula for the average failure interval, and the product operation guarantee temperature A first procedure for calculating an inspection time corresponding to the inspection temperature set in
A second procedure for continuing laser emission from the in-vehicle laser diode over the inspection time while maintaining the in-vehicle laser diode at the inspection temperature;
A third procedure for measuring a current value of a current necessary for laser light emission immediately after the vehicle-mounted laser diode starts laser light emission as a pre-inspection current value;
A fourth procedure for measuring a current value of a current necessary for laser emission just before the in-vehicle laser diode finishes laser emission as a post-inspection current value;
A fifth procedure for calculating a difference between the pre-inspection current value and the post-inspection current value as a current value change amount;
Performing a sixth procedure for determining whether the amount of change in the current value is within a specified range that can guarantee the product operation specified from the characteristics of the in-vehicle laser diode;
A method for inspecting the possibility of occurrence of deterioration failure in an in-vehicle laser diode, characterized by inspecting the possibility of occurrence of deterioration failure. For the purpose of shortening the inspection time, the inspection temperature set as the product operation guarantee temperature in the first procedure is set as the inspection temperature before setting the acceleration condition, and the inspection time calculated in the first procedure is accelerated. Set the inspection time before setting the conditions, and set the time shorter than the inspection time before setting the acceleration conditions as the inspection time after setting the acceleration conditions, and correspond to the inspection time after setting the acceleration conditions from the relationship between the inspection time and the inspection temperature. The temperature is calculated as the inspection temperature after setting the acceleration condition, and the sixth procedure to the sixth step are performed using the set inspection time after setting the acceleration condition and the calculated inspection temperature after setting the acceleration condition. 2. The inspection method for the possibility of deterioration failure in an in-vehicle laser diode according to claim 1, wherein the procedure is executed.

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