JP2008116281A - Ic tester calibrating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an IC tester calibrating method which assures a traceability of a tester system while shortening a calibration period. <P>SOLUTION: An accuracy diagnosing step S30 is carried out, wherein an IC tester having a plurality of pins is diagnosed whether the IC tester has its specification accuracy, based on whether each pin outputs an output value belonging to a specification band ranging from a specification lower-limit value to a specification upper-limit value. Then, in a high accuracy diagnosing step (step S40) which is carried out if a prescribed condition is satisfied during an operation of the IC tester, a diagnosis is carried out whether the IC tester has its specification accuracy for respective pins, based on whether each pin of the IC tester outputs an output value which belongs to a decision band being narrower than the specification band and ranging from a lower-limit decision value to a upper-limit decision value. In a step S42, a calibration is automatically applied to only pins diagnosed not to meet the specification accuracy in the high accuracy diagnosing step S40. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an IC tester calibration method that ensures traceability of an IC tester.

  IC (Integrated Circuit) tester, which is a kind of electronic measuring instrument, regulates its accuracy with accuracy specifications. However, since there is no mechanism to guarantee accuracy, the instructions cannot be trusted, so the concept of traceability is a national standard. Is set as According to JIS (Japanese Industrial Standard), traceability is: “Standard machines or measuring instruments are calibrated one after another by higher-level measurement standards, and a path leading to national and international standards is established (JIS Z 8103) ". The traceability of an electronic measuring instrument such as an IC tester is generally a chain of national standard (specific standard) -calibration organization-manufacturer standard-practical measuring instrument.

  An IC tester that is strong against all disturbances and can be used continuously without any maintenance once it is calibrated is ultimately desirable, but it is difficult to completely eliminate the deterioration in accuracy due to the influence of disturbances. Therefore, the measuring instrument manufacturer regularly calibrates on-site measuring instruments used in-house with its own standard equipment, and periodically takes the standard equipment to a calibration organization recognized by the national government for calibration.

  However, forcing the user to perform periodic calibration that needs to be performed after the operation of the IC tester is stopped causes stress on the user, so that, for example, Patent Documents 1 and 2 (Japanese Patent Laid-Open No. 10-227837) have been conventionally used. As described in Japanese Patent Laid-Open No. 2004-163194, the IC tester system itself has an automatic calibration function for automatically performing calibration. According to this, the user does not need to perform periodic calibration by himself / herself, does not need to be aware that the calibration is performed, and is less likely to feel stress.

Conventionally, automatic calibration is executed, for example, when any of the following conditions (1) to (3) is satisfied, thereby ensuring the traceability of the IC tester.
(1) A certain period of time (for example, 30 minutes) has elapsed since system startup (2) A certain period of time (recommended 24 hours) has elapsed since the last calibration (3) A predetermined temperature change (recommended ± 3 ° C) since the last calibration )
Japanese Patent Laid-Open No. 10-227837 JP 2004-163194 A

  However, even with automatic calibration, the system cannot be operated during calibration. FIG. 6 is a diagram showing the ratio of the operation time and the automatic calibration time in the actual system operation time of one day when the conventional automatic calibration is performed. As shown in FIG. 6, the operation time: automatic calibration time = 47: 1, and the system cannot be operated for a considerably long time spent for the automatic calibration.

  Even if only the output current / voltage value of the tester pin is used as a calibration item, automatic calibration will take longer in the future due to an increase in signal frequency and other calibration items and an increase in the number of pins itself. It is expected that.

  In addition, IC testers operating near power sources are more susceptible to electromagnetic waves than other IC testers, and IC testers operating in specific locations due to air convection in the plant or system are affected by temperature changes. In the future, it may be easily disturbed. In response to such disturbance, there is a possibility that an additional condition for executing automatic calibration for eliminating the influence of the disturbance may be imposed in addition to the conventional automatic calibration execution under simple timing conditions. As a result, automatic calibration is performed more frequently, and the time spent for automatic calibration in one day is likely to increase.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention has an object to ensure the traceability of an IC tester system while reducing or not significantly increasing the time for automatic calibration.

  In order to solve the above-described problem, an IC tester calibration method according to the present invention provides an output value belonging to a standard width in which each pin of an IC tester having a plurality of pins has a range from a standard lower limit value to a standard upper limit value. An accuracy diagnosis process for diagnosing whether the IC tester has the standard accuracy depending on whether it is output or not, and a high-accuracy diagnosis process executed when a predetermined condition is satisfied during operation of the IC tester The IC tester has the standard accuracy depending on whether or not each pin of the IC tester outputs an output value belonging to a judgment range having a range narrower than the standard range from the lower limit judgment value to the upper limit judgment value. A high-accuracy diagnosis step for diagnosing whether or not each pin and a calibration step for calibrating only the pin diagnosed as having no standard accuracy in the high-accuracy diagnosis step.

  In the above-mentioned calibration process, based on the latest and past one or more output values obtained in the high-accuracy diagnosis process, the output value in the next high-accuracy diagnosis process is expected to not belong to the judgment range May also be calibrated.

  The predetermined condition described above may be any of the following. That is, either a certain time has elapsed since the start of the IC tester, a certain time has elapsed since the previous calibration process, or a predetermined temperature change has occurred since the previous calibration process.

  According to the present invention, by limiting the pins to be calibrated among the pins of the tester module, the traceability of the IC tester system can be ensured without reducing or greatly increasing the calibration time.

  Embodiments of an IC tester according to the present invention will now be described in detail with reference to the accompanying drawings. In the figure, elements not directly related to the present invention are not shown. Similar elements are denoted by the same reference numerals.

  FIG. 1 is a block diagram showing an example of a tester system to which an IC tester calibration method according to the present invention is applied. The tester system 10 includes a plurality of IC tester modules 12A, 12B, and 12C and a tester controller 14 that controls them, all of which are connected via a bus 16. Each IC tester module 12A, 12B, 12C has a plurality of pins, and the number thereof may be 768 pins, for example. Although only three IC tester modules are shown in FIG. 1 for simplification of illustration, it goes without saying that there may be more than this.

  Each of the IC tester modules 12A, 12B, and 12C includes control units 20A, 20B, and 20C having timekeeping functions, memories 22A, 22B, and 22C, and temperature sensors 24A, 24B, and 24C. Each process of accuracy diagnosis, high-accuracy diagnosis and automatic calibration is performed. These steps may be performed by the tester controller 14. Details of these steps will be described later with reference to FIG.

  FIG. 2 is a flowchart showing an embodiment of the IC tester calibration method according to the present invention performed by the control units 20A, 20B, and 20C shown in FIG. Since the calibration methods of the IC tester modules 12A, 12B, and 12C are the same, the IC tester calibration method performed by the control unit 20A, the memory 22A, and the temperature sensor 24A for the IC tester module 12A will be described below.

  When the tester system 10 is activated, the control unit 20A first performs an initial calibration (step S30) of the IC tester module 12A, and stores calibration data including calibration contents in the memory 22A to ensure traceability.

  FIG. 3A is a diagram showing the standard width WS used in the accuracy diagnosis (step S32 in FIG. 2) performed next by the control unit 20A. In the accuracy diagnosis step S32, the control unit 20A determines that each pin of the IC tester module 12A has an output value belonging to the standard width WS having a range from the standard lower limit value SL to the standard upper limit value SU shown in FIG. Whether or not the IC tester module 12A has the standard accuracy is diagnosed on a pin-by-pin basis. The standard width WS includes the most ideal standard value S at the center thereof. The output value (diagnosis data) as a result of this diagnosis is also stored in the memory 22A by the control unit 20A to ensure traceability.

  After the above-described accuracy diagnosis step S32, the IC tester module 12A starts operation (step S34). Here, it is determined whether or not the initial calibration is performed by the user's manual operation (step S36), but this may be performed by the user's own judgment when some circumstances arise.

  The operation of the IC tester module 12A (step 34) is continued until a predetermined condition is satisfied (step S38). Here, the predetermined condition may be any of the following. That is, a certain time (for example, 30 minutes) has elapsed since the start of the tester system 10, a certain time (recommended 24 hours) has elapsed since the previous automatic calibration (step S42 described later), or the temperature sensor 24A has It is possible to detect that a predetermined temperature change (recommended ± 3 ° C.) has been detected from automatic calibration.

(First embodiment of IC tester calibration method)
When the predetermined condition is satisfied in step S38, the control unit 20A performs the high accuracy diagnosis step S40. FIG. 3B is a diagram illustrating an example of a diagnostic method in the high accuracy diagnostic step S40 of FIG. In this step S40, depending on whether or not each pin of the IC tester module 12A outputs an output value belonging to the determination width WD having a range narrower than the standard width WS from the lower limit determination value DL to the upper limit determination value DU, Whether or not the IC tester module 12A has the standard accuracy is diagnosed for each pin. Similarly to the standard width WS, the determination width WD includes the most ideal standard value S at the center.

  The controller 20A automatically calibrates only the pins diagnosed as having no standard accuracy (diagnostic fail) in the high-accuracy diagnostic step S40 described above (step S42). When there are a plurality of items (output current value, output voltage value, etc.) to be calibrated, this automatic calibration may be performed only for the items that have been diagnosed as fail.

  Thus, according to the present invention, the pin / item to be calibrated is selected in the high-accuracy diagnostic step S40, and it is not necessary to automatically calibrate all the pins / all the items. This is a stricter determination criterion in which the determination width WD of FIG. 3B used in the high accuracy diagnosis step S40 is narrower than the standard width WS of FIG. 3A used in normal accuracy diagnosis. This is because a pin / item that has passed the high-accuracy diagnosis using the determination width WD may be determined to have standard accuracy without performing automatic calibration.

  FIG. 5 is a flowchart showing a calibration method which is a comparative example with the present embodiment. Hereinafter, only differences from FIG. 2 will be described with reference to FIG. FIG. 5 does not include the high-accuracy diagnosis step S40 in FIG. 2, and if a certain condition is satisfied, automatic calibration is performed for all pins / all items (step S44). Therefore, in the above-described embodiment of the present invention, the number of pins / number of items for which automatic calibration is performed is reduced and the time spent for automatic calibration is reduced as compared with the calibration method shown in FIG. 5 as a comparative example. Benefits are gained.

  On the other hand, in FIG. 2 which is an embodiment of the present invention, a high-accuracy diagnostic step S40 not shown in FIG. 5 which is a comparative example is performed. However, when comparing the time required for automatic calibration and the time required for accuracy diagnosis, automatic calibration: accuracy diagnosis = 30: 1, and the time required for accuracy diagnosis is overwhelmingly shorter. This is because in calibration, the number of measurements is increased and averaged in order to reduce the influence of noise, so that it takes a much longer time than the diagnosis time. Therefore, even if the time spent in the high accuracy diagnostic step S40 performed in FIG. 2 and the time spent in the automatic calibration step S42 performed for the limited pins / items are added, all the pins performed in FIG. / It is much shorter than the time spent in the automatic calibration step S44 for all items.

(Second Embodiment of IC Tester Calibration Method)
The high accuracy diagnostic step S40 performed by the control unit 20A when a predetermined condition is satisfied in step S38 of FIG. 2 may be performed by the following method. FIG. 4 is a diagram showing another example of the diagnostic method in the high-accuracy diagnostic step S40 of FIG. The determination width WD used in this diagnosis may be the same as that shown in FIG. In the automatic calibration step S42, the control unit 20A first automatically calibrates items / pins whose output value has deviated from the determination width WD and became a diagnostic failure, as described with reference to FIG.

  In the automatic calibration step S42, the control unit 20A further performs the next high-accuracy diagnostic step based on the latest and past one or more output values shown in FIGS. 4A and 4B obtained in the high-accuracy diagnostic step S40. When the output value in S40 is predicted and it is predicted that it will not belong to the determination width WD as shown in FIG. 4C, the pin / item for which the output value is expected is automatically Perform calibration. In this embodiment, as shown in FIG. 4, the past output value of FIG. 4 (a) and the latest output value of FIG. 4 (b) are stored in the memory 22A, and drift components (FIG. The difference between the value V2 and the value V1) is predicted, and it is predicted that the output value V3 deviating from the determination width WD as shown in FIG. Then, the pins for which such a diagnostic failure is expected are automatically calibrated before the diagnostic failure occurs to ensure traceability.

  Here, as a prediction method, the next output value may be predicted based on the prediction that the drift component obtained in the past will be generated linearly next time, and the past drift component is as shown in FIG. In addition, the next output value may be predicted based on a non-linear prediction that occurs, for example, exponentially.

  According to the present embodiment, there is an advantage that automatic calibration can be performed early on pins / items that are expected to deviate from the determination width WD. On the other hand, according to the present embodiment, the number of pins for which automatic calibration is performed is increased as compared with the case where automatic calibration is performed for pins / items for which output values that simply deviate from the determination width WD are obtained. Even when compared with the comparative example of FIG. 5, the number of pins / items for which automatic calibration is performed is reduced, and the time spent for automatic calibration can be significantly reduced.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to these embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention is applicable to an IC tester calibration method that ensures traceability of an IC tester.

It is a block diagram which shows an example of the tester system to which the IC tester calibration method by this invention is applied. It is a flowchart which shows embodiment of the IC tester calibration method by this invention performed by the control part shown in FIG. (A) is a figure which shows the standard width | variety used by the precision diagnosis of FIG. 2, (b) is a figure which shows an example of the diagnostic method in the high precision diagnostic step of FIG. It is a figure which shows the other example of the diagnostic method in the high precision diagnostic step of FIG. It is a flowchart which shows the calibration method which is a comparative example with embodiment of this invention. It is a figure which shows the ratio of the working time and automatic calibration time in the actual operation time of the system of one day at the time of performing the conventional automatic calibration.

Explanation of symbols

10 Tester System 12A, 12B, 12C IC Tester Module 14 Tester Controller 16 Bus 20A, 20B, 20C Control Unit 22A, 22B, 22C Memory

Claims (5)

Whether or not the IC tester has the standard accuracy depending on whether or not each pin of the IC tester having a plurality of pins outputs an output value belonging to the standard width having a range from the standard lower limit value to the standard upper limit value. Accuracy diagnosis process for diagnosing pin by pin,
A high-accuracy diagnostic process executed when a predetermined condition is satisfied during operation of the IC tester, wherein each pin of the IC tester is a range narrower than the standard width from a lower limit judgment value to an upper limit judgment value A high-accuracy diagnostic step for diagnosing whether the IC tester has the standard accuracy for each pin depending on whether to output an output value belonging to a determination range having
An IC tester calibration method comprising: a calibration step of performing calibration only for pins diagnosed as having no standard accuracy in the high accuracy diagnostic step.   In the calibration process, based on the latest and past one or more output values obtained in the high-accuracy diagnosis process, it is expected that the output value in the next high-accuracy diagnosis process will not belong to the determination range. The IC tester calibration method according to claim 1, wherein calibration is also performed.   The IC tester calibration method according to claim 1, wherein the predetermined condition is that a predetermined time has elapsed since the IC tester was started.   The IC tester calibration method according to claim 1, wherein the predetermined condition is that a predetermined time has elapsed since a previous calibration process.   3. The IC tester calibration method according to claim 1, wherein the predetermined condition is that a predetermined temperature change has occurred since the previous calibration step.

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