JP2011091162A - Inspection method and inspection system for circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To rationally determine whether a circuit board is non-defective by detecting a latent defect of a conductive pattern of the circuit board. <P>SOLUTION: An inspection method includes a first inspection step in which the circuit board to be inspected is held at first test temperature and electric characteristics of the circuit board are measured to rank the circuit board as at least good, no good, or unknown based upon a measurement result; and a second inspection step in which change of electric characteristics of a circuit board ranked as unknown in the first inspection is measured for a predetermined time while the circuit board is held at second test temperature, and the circuit board is ranked as good or no good based upon a measurement result. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a non-defective inspection of a circuit board, and more particularly to an inspection of a circuit board before mounting an electronic component.

  Examples of defective circuit boards used in various electrical equipment include defective bonding such as mouse bites (pattern chipping), laser vias and blind vias, and defective soldering. Such defects often do not appear in a normal temperature environment and are difficult to detect in a normal test. Therefore, conventionally, as a countermeasure, troubles after shipment can be obtained by putting the finished board on which the electronic components are mounted or the finished electronic device to which the board is attached into an environmental testing machine and performing an aging inspection (stress test). The current situation is to prevent as much as possible.

  In the following Patent Document 1, as a technique for detecting a potential defect such as a fine portion (a narrowed portion or a crack) of a circuit board, a test current in which a direct current and an alternating current are superimposed is used as a circuit under test. It is described that the second harmonic of the test current caused by the temperature cycle of heating and cooling by Joule heat generated when flowing in the test is observed.

  Patent Document 2 discloses, as an improved technique with respect to Patent Document 1, a first DC power supply, a second DC power supply, and an AC power supply, and a first probe pair that forms a pair for connection to both ends of a circuit to be inspected. Including a second probe group and a switch for switching and connecting the AC power source to the first probe group or the second probe group. The switch switches preheating and inspection between a plurality of circuits to be inspected, and preheats before inspection. It is described that the entire inspection time is shortened by performing the above in parallel.

JP-A-58-19173 JP 2005-300386 A

  The aging inspection as described above takes a long inspection time, and if it is determined to be defective, the circuit board on which the electronic component is mounted is discarded, which causes problems such as waste and environmental destruction. there were. SUMMARY OF THE INVENTION An object of the present invention is to provide a circuit board inspection method and inspection system that can detect a potential defect of a circuit board before mounting an electronic component and reasonably judge whether it is good or bad.

  In the circuit board inspection method according to the present invention, the circuit board to be inspected is set to the first test temperature, the electrical characteristics of the circuit board are measured, and based on the measurement result, at least pass, fail, or unknown. A first inspection step for ranking, and a change in electrical characteristics of the circuit board is measured for a predetermined time while maintaining the circuit board ranked unclear in the step at the second test temperature, and the measurement result And a second inspection step for re-ranking pass or fail.

  Here, the first and second test temperatures are preferably selected from a range of about −40 ° C. to 200 ° C. in the case of an unmounted substrate on which no electronic component is mounted. On the other hand, in the case of a mounting board on which electronic components are mounted, it is desirable to select from a range of about −40 ° C. to 150 ° C.

  The first test temperature and the second test temperature may be the same temperature, but from the viewpoint of reliability, when the circuit board is inspected in a high temperature environment, the first test temperature is higher than the room temperature. The second test temperature may be a higher temperature.

When the circuit board is inspected in a low temperature environment, the first test temperature may be lower than room temperature, and the second test temperature may be further lower.
In such a method, the reliability of the inspection result can be further improved by making the condition of the second inspection step stricter than that of the first inspection step.

  In the first inspection step, the circuit board to be inspected may be set to the first test temperature in an atmosphere of a predetermined test humidity, and the electrical characteristics of the circuit board may be measured. .

  Further, in the second inspection step, the circuit board ranked unclear in the first inspection step is maintained at the second test temperature in an atmosphere of a predetermined test humidity, while the circuit board The change in electrical characteristics may be measured for a predetermined time.

  Here, the test humidity is desirably selected from a range of 10% to 100%.

  In the first inspection step, the measurement of the electrical characteristics of the circuit board may be repeated two or more times with different first test conditions.

  In the first inspection step, an evaluation standard for ranking at least pass, fail, and unknown for the circuit board on which the electrical characteristics are measured is prepared for each first test temperature. Also good.

  In this method, at least one of DC resistance and AC resistance may be inspected.

  Further, at least one of high-frequency reflection, resistance during high-current heat generation, high-frequency signal transmission delay time, impedance, leakage current, AC capacitor, and AC inductance may be inspected.

  A circuit board inspection system according to the present invention includes a first environmental device for bringing a circuit board to be inspected into a first test temperature and a test treatment for electrically contacting the circuit board carried out of the environmental device. A first test apparatus for measuring electrical characteristics of the circuit board, and the circuit board is ranked at least as pass, fail, or unknown based on a measurement result by the first test apparatus. A first environmental determination device; a second environmental device that carries in a circuit board that is unclearly ranked by the first determination device and maintains a second test temperature; and a circuit in the second environmental device. A test jig for making electrical contact with the board; a second test apparatus for measuring a change in electrical characteristics of the circuit board for a predetermined time; and the circuit board based on a measurement result by the second test apparatus. Is re-ranked to pass or fail And a second determination unit.

  Here, at least one of the first test apparatus and the second test apparatus further includes a cable connecting the test jig and the test apparatus, and a heat control means for controlling the heat of the cable. Also good.

  Further, at least one of the first environmental device and the second environmental device may be configured such that the carried circuit board is set to the first or second test temperature in an atmosphere of a predetermined humidity. Good.

  According to the method for inspecting a circuit board according to the present invention, it is possible to rationally determine whether the circuit board is defective by detecting a potential defect of the circuit board before mounting the electronic component. That is, among the circuit boards that are ranked as unacceptable and unknown by the first inspection step (conventionally regarded as defective), the circuit board that is specifically ranked as unknown is the second In the inspection step, the change of the electrical characteristics over time is measured. As a result, if the electrical characteristics are stable, there is no possibility of causing a problem in practical use, so that it is re-ranked as acceptable.

  As a result, it is possible to relieve a circuit board that has been determined to be unacceptable as an acceptable circuit board that has no problem in circuit operation. As a result, the yield is improved and the waste of defective circuit boards can be reduced.

  Note that if the first test temperature is higher than room temperature (in the case of a heating test) and the second test temperature is higher, the second inspection step is performed under more severe conditions. Therefore, reliability is further improved.

  Further, even when the first test temperature is lower than room temperature (in the case of a cooling test) and the second test temperature is further lower, the reliability is further improved as described above.

  In particular, in the first inspection step, the circuit board to be inspected is set to a test temperature in an atmosphere of a predetermined test humidity, and the electrical characteristics of the circuit board are measured, or in the second inspection step. In the configuration in which the circuit board ranked unclear in the first inspection step is measured at a test temperature in an atmosphere of a predetermined test humidity while measuring a change in electrical characteristics of the circuit board for a predetermined time. Inspection can be performed by promoting migration by humidity.

  Further, in the first inspection step, the defect can be detected more reliably in the configuration in which the measurement of the electrical characteristics of the circuit board is repeated twice or more with different test conditions.

  In the first inspection step, it is possible to detect defects more reliably in a configuration in which evaluation standards for ranking at least pass, fail, and unknown are prepared for each test temperature for circuit boards whose electrical characteristics have been measured. .

  If at least one of the direct current resistance and the alternating current resistance is inspected by the circuit board inspection method according to the present invention, it is possible to detect an open defect and a short defect of the conductive pattern.

  In addition, if the method for inspecting a circuit board according to the present invention inspects at least one of high-frequency reflection, resistance during high-current heat generation, high-frequency signal transmission delay time, impedance, leakage current, AC capacitor, AC inductance, etc. Even a specially designed circuit board can detect defects.

  The circuit board inspection system according to the present invention can be expected to have the same effects as described above. In particular, at least one of the first test apparatus and the second test apparatus includes a cable connecting the test probe and the test apparatus, and a thermal control means for controlling the heat of the cable. Even when the temperature is high, it is possible to prevent the connector provided in the test apparatus, the electronic circuit from being burned out, or dew condensation. Also, damage to the cable sheath can be prevented.

  As described above, according to the present invention, it is particularly effective for the conductive pattern inspection of the circuit board before mounting the electronic component, but it can also be applied to the characteristic inspection of the circuit board mounted with the electronic component.

3 is a flowchart showing a basic procedure of the method according to the present invention. It is another example of the flowchart which showed the basic procedure of the method by this invention. It is an example of evaluation criteria. It is the block diagram which showed the basic composition of the system by this invention. It is the schematic of a test apparatus.

In the method according to the present invention, a circuit board before mounting an electronic component is assumed as a circuit board to be inspected. Specific circuit boards include, for example, an unmounted printed board, an unmounted flexible board, an unmounted COF (Chip On Film), and an unmounted COB (Chip On
Board), unmounted TCP (Tape Carrier Package), unmounted TAB (Tape Automated Bonding). This method is particularly effective for the conductive pattern inspection of the circuit board before mounting the electronic component, but can also be applied to the characteristic inspection of the circuit board mounted with the electronic component.

In summary, the method sets the circuit board to be inspected to the first test temperature, measures the electrical characteristics of the circuit board, and ranks at least pass, fail, and unknown based on the measurement result. A first inspection step;
While maintaining the circuit board ranked unclear in this first step at the second test temperature, the change in the electrical characteristics of the circuit board is measured for a predetermined time, and based on the measurement result, it is passed or failed. And a second inspection step for re-ranking.

  The measurement items of basic electrical characteristics for the circuit board include, for example, a direct current resistance and an alternating current resistance of the conductive pattern. Thereby, an open defect and a short defect of the conductive pattern can be detected.

  In addition, it can be applied to high-frequency reflection, resistance during high-current heat generation, high-frequency signal transmission delay time, impedance, leakage current, AC capacitor, AC inductance, and the like as measurement items for more advanced electrical characteristics. As a result, it becomes possible to detect a defect even with a specially designed circuit board for high frequency use.

  The first and second test temperatures should be set in a range corresponding to the inspection item. Specifically, in the case of an unmounted substrate on which no electronic component is mounted, about −40 ° C. to 200 °. It is desirable to select from the range of C. On the other hand, in the case of a mounting board on which electronic components are mounted, it is desirable to select from a range of about −40 ° C. to 150 ° C. It is necessary to increase the test temperature to detect poor contact such as mouse bite (pattern chipping), laser via, blind via, etc., and open failure such as through hole and fine pattern (fine pattern). This is because it is necessary to lower the test temperature in order to detect short-circuit defects such as solder jumps.

  In particular, when the circuit board is inspected in a high temperature environment, it is desirable that the first test temperature is higher than room temperature and the second test temperature is higher. On the other hand, when the circuit board is inspected in a low temperature environment, it is desirable that the first test temperature is lower than room temperature and the second test temperature is further lower.

  In this way, since the inspection condition in the second inspection step becomes stricter than the inspection condition in the first inspection step, the reliability of the inspection result is further improved.

  In the first inspection step, the circuit board ranked as acceptable is a level that should be regarded as a non-defective product, but the circuit board ranked as unacceptable or unknown should be regarded as a defective product according to the standard. Of the level. However, the circuit boards that should be considered as defective include those that can be practically used although the quality is slightly inferior.

  In other words, if a defect such as a high resistance of the conductive pattern is detected, the degree of the defect is at a level that does not cause a problem in circuit operation, and there is no risk of further deterioration over time. Will not happen. Therefore, in the present method, such a circuit board is temporarily ranked as unknown by the first inspection step, and then the change over time of the electrical characteristics is measured by the second inspection step to pass or fail. Re-rank to pass. As a result, a circuit board that is supposed to be defective should be rescued as a non-defective product. As a result, yield can be improved and waste can be reduced.

  The unknown rank is preferably subdivided into a plurality of ranks depending on the value of the electrical characteristics. As a result, the tendency of occurrence of defects can be known, and a powerful clue for improving the manufacturing process can be obtained.

  FIG. 1 is a more detailed flowchart of the method. In this flowchart, the step of setting the circuit board to be inspected to the test temperature (S101), the step of measuring the electrical characteristics of the circuit board (S102), and at least passing, failing, unknown based on the measurement result The attaching step (S103) corresponds to the first inspection step.

  In addition, a step of selecting an unranked circuit board (S104), a step of setting the selected circuit board to a test temperature (S105), and a change in electrical characteristics while maintaining the circuit board at the test temperature. The step of measuring for a predetermined time (S106) and the step of re-ranking the circuit board to pass or fail (S107) correspond to the second inspection step. In addition, it is desirable to implement the step (S108) which returns a circuit board to normal temperature after these procedures.

  On the other hand, FIG. 2 is another example of the flowchart of this method. In this flowchart, compared to FIG. 1, in the point that step (S101) is removed, and in the procedure of step (S107 ′), the circuit board ranked unknown is re-ranked to pass or fail. The point is different.

  That is, the flowchart of FIG. 1 selects only the circuit boards that are ranked in the unknown in step (S104), and the subsequent steps (S105) to (S107 ′) are the circuit boards that are ranked in the unknown. Only for.

  On the other hand, in the flowchart of FIG. 2, step (S105) and step (S106) are performed for all circuit boards, and in step (S107 ′), only the circuit boards that are ranked as unknown are displayed. Re-rank to pass or fail.

  Thus, the method can be partially modified. However, in any case, the present invention includes the first inspection step and the second inspection step.

  In the first inspection step, the circuit board to be inspected may be set to a test temperature in an atmosphere of a predetermined test humidity, and the electrical characteristics of the circuit board may be measured. Alternatively, in the second inspection step, the circuit board ranked unclear in the first inspection step is subjected to a predetermined change in electrical characteristics of the circuit board while maintaining the test temperature in an atmosphere of a predetermined test humidity. You may measure time. If it does in this way, it will become possible to promote and detect migration by high humidity.

  Further, in the first inspection step, the measurement of the electrical characteristics of the circuit board may be repeated twice or more with different test conditions. In the first inspection step, an evaluation criterion for ranking at least pass, fail, and unknown for the circuit board whose electrical characteristics are measured may be prepared for each test temperature. Then, a defect can be detected more reliably.

  FIG. 3 is an example of evaluation criteria. In this evaluation standard, unknown is composed of a plurality of levels. When preparing an evaluation standard for each test temperature, such an evaluation standard is prepared for each temperature.

  In the following, the test of electrical characteristics possible by this method is illustrated.

  For example, in laser via defect detection, a high temperature is applied to widen the joining portion of the laser via, and the quality of the joining is judged by a high frequency reflection inspection, a high frequency transmission delay inspection, a high current heating resistance inspection, or a low resistance inspection. . At that time, it is desirable to select the first and second test temperatures from 125 ° C to 200 ° C. At this time, the humidity is not particularly limited.

  In migration failure detection, since migration is formed in an environment of high temperature, high humidity, and strong electric field, a positive voltage and a negative voltage are applied to the insulating part for a certain period of time, and within that period, it is instantaneous or at regular intervals. In addition, leakage current inspection, continuous leakage current inspection, and insulation resistance inspection are performed. In that case, it is desirable to select the first and second test temperatures from 60 ° C to 180 ° C. The humidity is desirably 60% to 100%.

  Further, in detecting a mouse bite defect and a crack defect, a high-frequency reflection inspection and a high-frequency transmission delay inspection are performed. In this case, it is desirable to select the first and second test temperatures from −40 ° C. to 200 ° C. At this time, the humidity is not particularly limited.

FIG. 4 is a basic block diagram of a circuit board test system to which the present method is applied.
The test system 1 includes a first environmental device 11 that brings the circuit board 20 to be inspected into the first test temperature, and a test treatment that makes electrical contact with the circuit board 20 carried out of the environmental device 11. Based on the measurement result of the first test apparatus 12 having the tool 12a and measuring the electrical characteristics of the circuit board 20 and the first test apparatus 12, the circuit board 20 is at least passed, rejected, or unknown. A first determination means 13 for ranking, a second environmental device 14 that carries in the circuit board 20 that has been ranked indefinitely by the first determination means 13 and maintains the second test temperature, and a second A second test apparatus 15 having a test jig 15a for making electrical contact with the circuit board 20 in the environmental apparatus 14 and measuring a change in electrical characteristics of the circuit board 20 for a predetermined time, and a second test apparatus. 15 based on the measurement result There are, the circuit board 20, pass, and a second determination means 16 for attaching again ranked rejected, and a third environmental device 17 to return the circuit board 20 to the normal temperature.

  The environmental device 11, the test jig 12 a, the determination unit 13, the environmental device 14, the determination unit 16, and the environmental device 17 are connected by a transport unit 19 that transports the circuit board 20.

  The test devices 12 and 15 are connected to test jigs 12a and 15b via cables 12c and 15c. The cables 12c and 15c are provided with thermal control means 12b and 15b for controlling the heat of the cables 12c and 15c. It has been added. In addition, the test devices 12 and 15 have, as the electrical characteristics of the circuit board 20, for example, DC resistance and AC resistance of the conductive pattern, further high frequency reflection, resistance at high current heating, high frequency signal transmission delay time, impedance, leakage current, It has a function to measure AC capacitors, AC inductances, etc.

  The determination means 13 stores in advance evaluation criteria related to pass, fail, and unknown, and applies the evaluation criteria to the measurement result of the test apparatus 12 to rank the circuit board 20 as pass, fail, or unknown. . The result is stored. Further, the ranking may be marked at a predetermined position of the circuit board ranked as pass or fail.

  Further, the judging means 16 stores in advance evaluation criteria concerning pass / fail, and applies the evaluation criteria to the measurement result of the test apparatus 15 to pass or fail the circuit board 20 ranked unknown. Re-rank. Further, the ranking may be marked at a predetermined position of the circuit board ranked as pass or fail.

  The environmental devices 11, 14, and 17 may use a general environmental testing machine. The environmental testing machine generally has a performance of thermally controlling a controlled object from a predetermined temperature to about ± 1 ° C. by generating low temperature wind by a thermostream and generating high temperature wind by a heater. Further, the environmental devices 11 and 14 may include humidity control means 18 and 19 so that the circuit board 20 carried in can be set to a test temperature in an atmosphere of a predetermined humidity.

  In the environmental devices 11 and 17, a plurality of circuit boards are accumulated, and circuit boards that have reached the test temperature after a lapse of a predetermined time are sequentially taken out. Thereby, batch processing of a plurality of circuit boards becomes possible.

  FIG. 5 is a schematic configuration diagram of the test apparatus 12, but the test apparatus 15 has the same configuration. On the upper surface of the test jig 12a, a large number of probe needles 12d are arranged and projected in a pattern corresponding to the circuit board 20 at a predetermined location, and when the circuit board 20 is placed on the test jig 12a, the probe The needle 12d comes into contact with a test land or the like formed on the circuit board 20. Note that the probe needle 12d itself has elasticity or is biased upward by a metal spring or the like, and if the circuit board 20 placed on the test jig 12a is pressed downward, it is used for testing. It contacts the land etc. securely and is electrically connected. The number of probe needles 12d is not limited.

  The probe needle 12d is connected to a connector provided on the test jig 12a, and a cable 12c led out from the test apparatus 12 is connected to the connector. The type of the cable 12c is not particularly limited. For example, the cable 12c may be formed of a general-purpose flat cable or a flexible cable, or may be formed of a harness made of a single wire cable such as an enamel wire or a magnet wire.

  The cable 12c is connected to the test apparatus 12 via the heat control means 12b. A metal heat transfer member 12e is added to an intermediate portion of the cable 12d, and the heat control means 12b thermally controls the cable 12c through the heat transfer member 12e. The heat transfer member 12e is preferably formed of, for example, a copper plate having excellent thermal conductivity. By thermally controlling the cable 12c by the thermal control means 12b, it is possible to prevent a connector provided in the test apparatus 12 from being burned out or dew condensation. Further, the covering of the cable 12c can also be prevented from being damaged.

DESCRIPTION OF SYMBOLS 1 Circuit board inspection system 11 1st environmental apparatus 12 1st test apparatus 12a Test jig 12b Thermal control means 13 1st determination means 14 2nd environmental apparatus 15 2nd test apparatus 15a Test jig 15b Heat Control means 16 Second determination means 20 Circuit board

Claims (12)

A first test step in which the circuit board to be inspected is set to a first test temperature, electrical characteristics of the circuit board are measured, and at least a pass, a fail, and an unknown are ranked based on the measurement results;
While maintaining the circuit board ranked unclear in the above step at the second test temperature, the change in the electrical characteristics of the circuit board is measured for a predetermined time, and re-ranked to pass or fail based on the measurement result. A circuit board inspection method comprising: a second inspection step. In claim 1,
A circuit board inspection method characterized in that the first test temperature is higher than room temperature, and the second test temperature is higher. In claim 1,
The circuit board inspection method, wherein the first test temperature is lower than room temperature, and the second test temperature is lower. In any one of Claims 1-3,
In the first inspection step, the circuit board to be inspected is set to the first test temperature in an atmosphere of a predetermined test humidity, and the electrical characteristics of the circuit board are measured. Inspection method. In any one of Claims 1-4,
In the second inspection step, the circuit board ranked unclear in the first inspection step is kept at the second test temperature in an atmosphere of a predetermined test humidity while the circuit board is electrically A circuit board inspection method characterized by measuring a change in characteristics for a predetermined time. In any one of Claims 1-5,
In the first inspection step, the circuit board inspection method is characterized in that the measurement of the electrical characteristics of the circuit board is repeated twice or more at different first test temperatures. In claim 6,
In the first inspection step, an evaluation criterion for ranking at least pass, fail, and unknown for the circuit board on which the electrical characteristics are measured is prepared for each of the first test temperatures. Circuit board inspection method. In any one of Claims 1-7,
An inspection method for a circuit board, wherein at least one of a direct current resistance and an alternating current resistance is inspected as the electrical characteristic. In any one of Claims 1-7,
A method for inspecting a circuit board, comprising: inspecting at least one of high-frequency reflection, resistance during high-current heat generation, high-frequency signal transmission delay time, impedance, leakage current, AC capacitor, and AC inductance as the electrical characteristics. A first environmental device for bringing a circuit board to be inspected into a first test temperature;
A first test apparatus that has a test jig for making electrical contact with the circuit board carried out from the environmental apparatus, and that measures the electrical characteristics of the circuit board;
First determination means for ranking the circuit board at least as pass, fail, or unknown based on the measurement result by the first test apparatus;
A second environmental device that carries in a circuit board ranked indefinitely by the first determination means and maintains a second test temperature;
A second test device having a test jig for making electrical contact with a circuit board in the second environmental device, and measuring a change in electrical characteristics of the circuit board for a predetermined time;
A circuit board inspection system comprising: second determination means for re-ranking the circuit board to pass or fail based on a measurement result by a second test apparatus. In claim 8,
At least one of the first test apparatus and the second test apparatus is:
A circuit board inspection system further comprising: a cable connecting the test jig and the test apparatus; and a heat control means for controlling the heat of the cable. In claim 8 or 9,
At least one of the first environmental device and the second environmental device has the circuit board carried therein at the first or second test temperature in an atmosphere of a predetermined humidity. Inspection system.

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