Abstract:
A method for managing an assembling process of an electrical product. The electrical product at least includes a substrate with a semiconductor component mounted thereon and a power supply circuit. In the method, during assembly of the electrical product, a potential difference between two points on electric wires or signal wires electrically connected with an impedance element, which is inside the electrical product, interposed therebetween is constantly measured. Also, in the method, if a change that exceeds a predetermined threshold value, based on which electrostatic discharge noise and a normal potential range are distinguished from each other, occurs in the potential difference between the two points, measurement data on the potential difference between the two points is recorded and a mark for indicating that the electrical product was affected by electrostatic discharge is provided to the electrical product.

Description:
FIELD 
       [0001]    The present invention relates to a method for managing an assembling process of an electrical product. 
       BACKGROUND 
       [0002]    In order to prevent work with a charged tool or human hands when assembling an electrical product in which a substrate including a semiconductor component (semiconductor device) (such as an IC, an LSI and a transistor), a storage apparatus, or the like, are combined, clothes or the like which remove and prevent static electricity is used. However, during assembly, an electrical product does not always have the same potential as that of the tool or a person, and there is a possibility that static electricity is accidentally discharged. The following literatures describe detection of static electricity discharge. 
         [0003]    JP 10-12691 A discloses a technique of detecting an electromagnetic wave or discharge light of static electricity discharge due to a peeling charge generated on a substrate and detecting damage related to the static electricity discharge during manufacturing process of an electronic device (for example, a thin-film transistor liquid crystal display). 
         [0004]    JP 2009-515171 A discloses a technique of using a voltage measuring circuit connected between a ground and a circuit substrate via a resistance to measure discharge of static electricity generated when an assembling tool is brought into contact with the circuit substrate and to thereby monitor ESD exposure of the circuit substrate. 
       CITATION LIST 
     Patent literature 
       [0005]    [PTL 1] JP 10-12691 A 
         [0006]    [PTL 2] JP 2009-515171 A 
       SUMMARY 
     Technical Problem 
       [0007]    While, with the above-described related art, it is possible to detect that static electricity discharge occurs at an object, it is not possible to judge whether the static electricity discharge affects the object to a level wherein the quality is affected. Therefore, there is a case where even an object whose quality is not affected is regarded as a disqualified product, which may degrade a yield accordingly. 
         [0008]    The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for managing assembling process of an electrical product which is capable of identifying and managing an electrical product affected by static electricity discharge with high accuracy. 
       Solution to Problem 
       [0009]    To achieve the above-described object, an embodiment of the present invention is a method for managing an assembling process of an electrical product including at least a substrate on which a semiconductor component is mounted and a power supply circuit, the method including always measuring a potential difference between two points on electrical lines or signal lines electrically connected across an impedance element inside the electrical product while the electrical product is assembled, and recording measurement data of the potential difference between the two points when change exceeding a predetermined threshold for distinguishing between static electricity discharge noise and a normal potential range occurs in the potential difference between the two points, and providing a marker for identifying that the electrical product is affected by static electricity discharge to the electrical product. 
       Advantageous Effects of Invention 
       [0010]    According to the embodiment of the present invention, by always measuring a potential difference between two points on electrical lines or signal lines electrically connected across an impedance element inside an electrical product and monitoring whether or not change exceeding a predetermined threshold occurs in the potential difference between the two points while the electrical product is assembled, it is possible to identify and manage an electrical product affected by static electricity discharge with high accuracy. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a diagram for explaining an apparatus configuration according to Embodiment 1 of the present invention. 
           [0012]      FIG. 2  is a diagram for explaining electrical connection between a semiconductor component  5  and static electricity measuring equipment  9  in Embodiment 1. 
           [0013]      FIG. 3  is a flowchart for explaining a method for managing an assembling process of an electrical product  2  in Embodiment 1. 
           [0014]      FIG. 4  is a diagram for explaining one modified example of Embodiment 1. 
           [0015]      FIG. 5  is a diagram for explaining one modified example of Embodiment 1. 
           [0016]      FIG. 6  is a diagram for explaining an apparatus configuration according to Embodiment 2 of the present invention. 
           [0017]      FIG. 7  is a diagram for explaining electrical connection between the semiconductor component  5  and the static electricity measuring equipment  9  in Embodiment 2. 
           [0018]      FIG. 8  is a flowchart for explaining a method for managing an assembling process of the electrical product  2  in Embodiment 2. 
           [0019]      FIG. 9  is a diagram for explaining one modified example of Embodiment 2. 
           [0020]      FIG. 10  is a diagram for explaining an example where a potential difference between two points on signal lines is measured in Embodiment 3. 
           [0021]      FIG. 11  is a diagram for explaining one modified example of Embodiment 1. 
           [0022]      FIG. 12  is a diagram for explaining one modified example of Embodiment 1. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0023]    Embodiments of the present invention will be described in detail below with reference to the drawings. It should be noted that the same reference numerals are assigned to elements common in the drawings, and explanation thereof will be omitted. 
       Embodiment 1 
       [0024]      FIG. 1  is a diagram for explaining an apparatus configuration according to Embodiment 1 of the present invention. 
         [0025]    An apparatus illustrated in  FIG. 1  includes a workbench  1 . An electrical product  2  is placed on the workbench  1 . The electrical product  2  includes at least a substrate  3  and a power supply circuit  4 . A semiconductor component (a semiconductor device)  5  is mounted on the substrate  3 . The substrate  3  and the power supply circuit  4  are mounted on the electrical product  2  using a tool  6 . 
         [0026]    The semiconductor component  5  is electrically connected to the power supply circuit  4  using electrical lines  7  via the substrate  3 . Further, the electrical lines  7  are connected to static electricity measuring equipment  9  via a terminal  8 . The static electricity measuring equipment  9  is connected to a computer  10 . 
         [0027]    While the electrical product  2  is assembled, the static electricity measuring equipment  9  always measures a potential difference between two points on the electrical lines  7  electrically connected across an impedance element (semiconductor component  5 ) inside the electrical product  2 . It should be noted that a measurement period is preferably equal to or less than 100 ns. 
         [0028]    Further, when change exceeding a predetermined threshold for distinguishing between static electricity discharge noise and a normal potential range occurs in the above-described potential difference between the two points, the static electricity measuring equipment  9  transmits measurement data of the above-described potential difference between the two points to the computer  10 . It should be noted that the above-described threshold is an index indicating static electricity discharge which can affect quality, and is set in advance based on an experimental result or a simulation result. As one example, when a rated voltage of the semiconductor component is 5.5 V, the threshold is set at 7 V. 
         [0029]    The computer  10  includes a memory including, for example, a ROM, a RAM, or the like, an input/output interface for inputting/outputting various kinds of information, and a processor which is capable of executing various kinds of arithmetic processing based on the various kinds of information. The computer  10  receives and records the measurement data transmitted from the static electricity measuring equipment  9  and provides a marker for identifying that the electrical product  2  is affected by static electricity discharge to the electrical product  2 . Specifically, the computer  10  adds a marker to the measurement data. The computer  10  has a screen as an output interface and displays the measurement data to which the marker is added on the screen. Further, the computer  10  has a communication connector for connecting to external equipment as an output interface and externally transmits the measurement data via the communication connector. 
         [0030]      FIG. 2  is a diagram for explaining electrical connection between the semiconductor component  5  and the static electricity measuring equipment  9  in Embodiment 1. The electrical lines  7  illustrated in  FIG. 1  includes two electrical lines  71  and  72  illustrated in  FIG. 2 . The two electrical lines  71  and  72  connect the power supply circuit  4  (power supply apparatus in  FIG. 2 ) and the semiconductor component  5 . The static electricity measuring equipment  9  is connected to one point on the electrical line  71  and one point on the electrical line  72 . The static electricity measuring equipment  9  measures a potential difference between the two electrical lines  71  and  72 . 
         [0031]    (Flowchart) 
         [0032]      FIG. 3  is a flowchart for explaining a method for managing an assembling process of the electrical product  2  in Embodiment 1. Routine illustrated in  FIG. 3  is executed every time assembly of the electrical product  2  is started. 
         [0033]    In step S 101 , a worker connects the electrical lines  7  and the static electricity measuring equipment  9 . Specifically, the worker connects the two electrical lines  71  and  72  to the static electricity measuring equipment  9 . It should be noted that the worker is not limited to a human and may be mechanical equipment having a robot arm, or the like. 
         [0034]    In step S 102 , the worker determines whether or not an assembling process of the electrical product  2  is completed. When the assembling process is not completed, processing in step S 103  is executed. 
         [0035]    In step S 103 , the static electricity measuring equipment  9  measures a potential difference between the two electrical lines  71  and  72 . 
         [0036]    In step S 104 , the static electricity measuring equipment  9  determines whether or not the potential difference measured in step S 103  is smaller than a threshold. As described above, the threshold is a predetermined value for distinguishing between static electricity discharge noise and a normal potential range and is set in advance. 
         [0037]    When the determination conditions in step S 104  are satisfied, static electricity discharge which affects quality of the electrical product  2  does not occur, and processing from step S 102  is continued. When it is determined in step S 102  that the assembling process of the electrical product  2  is completed, this routine is finished. 
         [0038]    When the determination conditions in step S 104  are not satisfied, the measurement data of the potential difference measured in step S 103  is recorded in the computer  10  (step S 105 ). Specifically, the static electricity measuring equipment  9  transmits the measurement data to the computer  10 , and the computer  10  stores the received measurement data. 
         [0039]    In step S 106 , the computer  10  provides a marker to the measurement data. The marker is a marker for identifying that the electrical product  2  is affected by static electricity discharge. 
         [0040]    In step S 107 , the computer  10  displays the measurement data to which the marker is added, on the screen. Further, the computer  10  externally transmits the measurement data via the communication connector. Through these processing, the worker can know that static electricity discharge which can affect quality occurs at a half-finished product which is being manufactured. 
         [0041]    In step S 108 , the worker removes the half-finished product at which static electricity discharge which can affect quality occurs. After the processing in step S 108 , this routine is finished. 
         [0042]    As described above, according to the method for managing the assembling process of the electrical product according to Embodiment 1, by always measuring the potential difference between the two points on the electrical lines  7  electrically connected across the impedance element inside the electrical product and monitoring whether or not change exceeding the predetermined threshold occurs in the potential difference between the two points while the electrical product is assembled, it is possible to identify and manage an electrical product affected by static electricity discharge with high accuracy. Further, according to the method for managing the assembling process of the electrical product according to Embodiment 1, when static electricity discharge which can affect quality of a half-finished product which is being manufactured occurs, it is possible to immediately remove the half-finished product which is being assembled. 
         [0043]    (Modified example) 
         [0044]    A modified example of the above-described Embodiment 1 will be described.  FIG. 4  is a diagram for explaining one modified example of Embodiment 1. The configuration in  FIG. 4  is the same as the configuration in  FIG. 2  except that connectors  71   a  and  72   b  are provided. The connector  71   a  is connected on one point on the electrical line  71 , and the connector  72   b  is connected on one point on the electrical line  72 . The static electricity measuring equipment  9  is connected to the connectors  71   a  and  72   b.  Because the connectors  71   a  and  72   b  for measuring a potential difference are provided on two points which are measurement points, attachment of the static electricity measuring equipment  9  becomes easy, which improves management efficiency of the assembling process of the electrical product  2 . 
         [0045]      FIG. 5  is a diagram for explaining one modified example of Embodiment 1. The configuration in  FIG. 5  is the same as the configuration in  FIG. 1  except that the static electricity measuring equipment  9  has a radio communication function for transmitting measurement data, and radio communication equipment  11  is added. The radio communication equipment  11  receives the measurement data transmitted from the static electricity measuring equipment  9  and transmits the measurement data to the computer  10 . In this manner, it is also possible to employ a configuration where the static electricity measuring equipment  9  is wirelessly connected to the computer  10 . 
         [0046]      FIG. 11  is a diagram for explaining one modified example of Embodiment 1. In the configuration illustrated in  FIG. 11 , the static electricity measuring equipment  9  is provided for each workbench, and each static electricity measuring equipment  9  is connected to a common wired transmission path  12 . The wired transmission path  12  is connected to the computer  10 . Each static electricity measuring equipment  9  transmits the measurement data to the computer  10  via the wired transmission path  12 . In this manner, it is also possible to employ a configuration where a plurality of static electricity measuring equipment  9  are connected in a wired manner to one computer  10 . This point will also apply to the following embodiments. 
         [0047]      FIG. 12  is a diagram for explaining one modified example of Embodiment 1. In the configuration illustrated in  FIG. 12 , the static electricity measuring equipment  9  is provided for each workbench, and each piece of static electricity measuring equipment  9  has a radio communication function. Radio communication equipment  13  receives the measurement data transmitted from each piece of static electricity measuring equipment  9  and transmits the measurement data to the computer  10 . In this manner, it is also possible to employ a configuration where multiple pieces of static electricity measuring equipment  9  are wirelessly connected to one computer  10 . This point will also apply to the following embodiments. 
       Embodiment 2 
       [0048]    Embodiment 2 of the present invention will be described next with reference to  FIG. 6  to  FIG. 9 . 
         [0049]    In the above-described Embodiment 1, in order to measure the potential difference between the two points on the electrical lines electrically connected across the impedance element (semiconductor component), a potential difference between two points of the power supply circuit  4  and the semiconductor component  5  on the electrical lines  7  is measured. However, the points where the potential difference is measured are not limited to these. In Embodiment 2, a potential difference between terminals of a plug of the power supply circuit  4  is measured. 
         [0050]      FIG. 6  is a diagram for explaining an apparatus configuration according to Embodiment 2 of the present invention. 
         [0051]    An apparatus illustrated in  FIG. 6  includes the workbench  1 . The electrical product  2  is placed on the workbench  1 . The electrical product  2  includes at least the substrate  3  and the power supply circuit  4 . The semiconductor component  5  is mounted on the substrate  3 . The substrate  3  and the power supply circuit  4  are mounted on the electrical product  2  using the tool  6 . 
         [0052]    The power supply circuit  4  and the semiconductor component  5  are electrically connected using the electrical lines  7  via the substrate  3 . Further, the electrical lines  7  are electrically connected to electrical lines  20  inside the power supply circuit  4 . The electrical lines  20  have a plug  21 . The plug  21  is connected to a terminal  8 . Therefore, the electrical lines  20  are connected to the static electricity measuring equipment  9  via the terminal  8 . The static electricity measuring equipment  9  is connected to the computer  10 . 
         [0053]    The static electricity measuring equipment  9  always measures a potential difference between two points on the electrical lines  20  electrically connected across the impedance element (semiconductor component  5 ) inside the electrical product  2  while the electrical product  2  is assembled. It should be noted that a measurement period is preferably equal to or less than 100 ns. 
         [0054]    Further, when change exceeding a predetermined threshold for distinguishing between static electricity discharge noise and a normal potential range occurs in the above-described potential difference between the two points, the static electricity measuring equipment  9  transmits measurement data of the above-described potential difference between the two points to the computer  10 . It should be noted that the above-described threshold is an index indicating static electricity discharge which can affect quality and is set in advance based on an experimental result or a simulation result. 
         [0055]    Since the computer  10  is as described in Embodiment 1, description thereof will be omitted. 
         [0056]      FIG. 7  is a diagram for explaining electrical connection between the semiconductor component  5  and the static electricity measuring equipment  9  in Embodiment 2. The electrical lines  20  illustrated in  FIG. 6  includes two electrical lines  73  and  74  illustrated in  FIG. 7 . The two electrical lines  73  and  74  connect the power supply circuit  4  and the plug  21 . The static electricity measuring equipment  9  is connected to one point on the electrical line  73  and one point on the electrical line  74 . The static electricity measuring equipment  9  measures a potential difference between the two electrical lines  73  and  74 . 
         [0057]    (Flowchart) 
         [0058]      FIG. 8  is a flowchart for explaining a method for managing assembling process of the electrical product  2  in Embodiment 2. Routine illustrated in  FIG. 8  is executed every time the electrical product  2  is assembled. This routine is the same as the routine illustrated in  FIG. 3  except that step S 101  is replaced with step S 201 , step S 103  is replaced with step S 203 , and step S 104  is replaced with step S 204 . In the following description, in  FIG. 8 , the same reference numerals will be assigned to the same steps as the steps illustrated in  FIG. 3 . 
         [0059]    In step S 201 , the worker connects the electrical lines  20  and the static electricity measuring equipment  9 . Specifically, the worker connects the two electrical lines  73  and  74  to the static electricity measuring equipment  9 . It should be noted that the worker is not limited to a human, and may be mechanical equipment having a robot arm, or the like. 
         [0060]    In step S 102 , the worker determines whether or not assembling process of the electrical product  2  is completed. When the assembling process is not completed, the processing in step  5203  is executed. 
         [0061]    In step S 203 , the static electricity measuring equipment  9  measures a potential difference between the two electrical lines  73  and  74 . 
         [0062]    In step S 204 , the static electricity measuring equipment  9  determines whether or not the potential difference measured in step S 203  is smaller than a threshold. The threshold is a predetermined value for distinguishing between static electricity discharge noise and a normal potential range and is set in advance. 
         [0063]    When the determination conditions in step S 204  are satisfied, static electricity discharge which affects quality of the electrical product  2  does not occur, and the processing from step S 102  is continued. When it is determined in step S 102  that the assembling process of the electrical product  2  is completed, this routine is finished. 
         [0064]    When the determination conditions in step  5204  are not satisfied, the measurement data of the potential difference measured in step S 203  is recorded (step S 105 ). Specifically, the static electricity measuring equipment  9  transmits the measurement data to the computer  10 , and the computer  10  stores the received measurement data. 
         [0065]    In step S 106 , the computer  10  provides a marker to the measurement data. The marker is a marker for identifying that the electrical product  2  is affected by static electricity discharge. 
         [0066]    In step S 107 , the computer  10  displays the measurement data to which the marker is provided, on the screen. Further, the computer  10  externally transmits the measurement data via the communication connector. Through the processing, the worker can know that static electricity discharge which can affect quality occurs at a half-finished product which is being manufactured. 
         [0067]    In step S 108 , the worker removes a half-finished product at which static electricity discharge which can affect quality occurs. After the processing in step S 108 , this routine is finished. 
         [0068]    As described above, according to the method for managing the assembling process of the electrical product according to Embodiment 2, by always measuring the potential difference between the two points on the electrical lines  20  electrically connected across the impedance element inside the electrical product and monitoring whether or not change exceeding the predetermined threshold occurs in the potential difference between the two points while the electrical product is assembled, it is possible to identify and manage an electrical product affected by static electricity discharge with high accuracy. Further, according to the method for managing the assembling process of the electrical product according to Embodiment 2, when static electricity discharge which can affect quality occurs at a half-finished product which is being manufactured, it is possible to immediately remove the half-finished product which is being assembled. 
         [0069]    (Modified example) 
         [0070]    A modified example of the above-described Embodiment 2 will be described.  FIG. 9  is a diagram for explaining one modified example of Embodiment 2. The configuration in  FIG. 9  is the same as the configuration in  FIG. 6  except that the static electricity measuring equipment  9  has a radio communication function for transmitting measurement data, and the radio communication equipment  11  is added. The radio communication equipment  11  receives the measurement data transmitted from the static electricity measuring equipment  9  and transmits the measurement data to the computer  10 . In this manner, it is also possible to employ a configuration where the static electricity measuring equipment  9  and the computer  10  are wirelessly connected. 
       Embodiment 3 
       [0071]    Embodiment 3 of the present invention will be described next with reference to  FIG. 10 . In Embodiments 1 and 2, the potential difference between the two points on the electrical lines is measured. However, it is also possible to measure a potential difference between two points on signal lines by utilizing connectors for signal test provided on the signal lines. 
         [0072]      FIG. 10  is a diagram for explaining an example where a potential difference between two points on signal lines is measured in Embodiment 3. The electrical product  2  includes the substrate  3  and a power supply circuit. On the substrate  3 , an impedance element such as a semiconductor component and a memory is disposed. The static electricity measuring equipment  9  is connected to connectors  81  and  82  for signal test provided on the signal lines. The static electricity measuring equipment  9  always measures a potential difference between two points (connectors  81  and  82  for signal test) on the signal lines across the impedance element while the electrical product  2  is assembled. When change exceeding a predetermined threshold for distinguishing between static electricity discharge noise and a normal potential range occurs in the above-described potential difference between the two points, the static electricity measuring equipment  9  transmits measurement data of the above-described potential difference between the two points to the computer  10 . It should be noted that the above-described threshold is an index indicating static electricity discharge which can affect quality and is set in advance based on an experimental result or a simulation result. Because the computer  10  is as described in the above-described Embodiment 1, detailed explanation thereof will be omitted. The computer  10  records the measurement data transmitted from the static electricity measuring equipment  9  and provides a marker for identifying that the electrical product  2  is affected by static electricity discharge to the electrical product  2 . 
       REFERENCE SIGNS LIST 
       [0073]      1  Workbench 
         [0074]      2  Electrical product 
         [0075]      3  Substrate 
         [0076]      4  Power supply circuit 
         [0077]      5  Semiconductor component 
         [0078]      6  Tool 
         [0079]      7  Electrical lines 
         [0080]      8  Terminal 
         [0081]      9  Static electricity measuring equipment 
         [0082]      10  Computer 
         [0083]      11 ,  13  Radio communication equipment 
         [0084]      12  Wired transmission path 
         [0085]      20  Electrical lines 
         [0086]      21  Plug 
         [0087]      71 ,  72 ,  73 ,  74  Electrical line 
         [0088]      71   a,    72   b  Connector 
         [0089]      81 ,  82  Connector for signal test