JPH04221780A - Detecting method for detective contact of pin for measurement in circuit board inspecting device - Google Patents

Abstract

PURPOSE:To perform detection of defective contact of a pin for measurement by measuring impedance of an indefective board between given two pins, determining comparing reference data for detecting defective contact, and comparing the comparing reference data with the impedance value of a board decided to be defective. CONSTITUTION:Based on one pin connected to a measuring part 4, all other pins are connected, in order, one by one to a signal source. From minimum data of test between two pins through which impedance there between is measured, comparing reference data for detecting defective contact is determined, and the data is stored in a data holding means 15. Regarding boards in a lot to be inspected which are decided to be defective, impedance between two pins is measured in a similar manner described above, and the data is compared with comparing reference data by means of a comparing and deciding means 16.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting poor contact of measuring pins in a circuit board testing device.

0002

2. Description of the Related Art A circuit board testing device called an in-circuit tester is used to test circuit boards on which electronic components and the like are mounted.

In general, this type of device applies a measurement signal from a signal source via a pin that contacts a predetermined circuit pattern position on the board after placing the board to be tested on the device, and then transmits the response signal to another signal. It is designed to be taken into the measuring section through the contact pin and measured. In this case, measurements are performed on each component on the board individually, and the data is compared with values stipulated in each component standard, catalog specifications, etc. to determine whether the board is good or bad. .

However, since the measurement items and rated values differ depending on the component, it takes a great deal of effort and time to complete the inspection for high-density mounting boards. Automating the measurement would solve the above problems, but this would require a complex and large-scale control program, which would be extremely difficult to create in an inspection department or the like.

[0005] Therefore, the present applicant considers a plurality of components connected to a certain circuit pattern to be one circuit network including that pattern, and the applicant considers that a plurality of components connected to a certain circuit pattern including that pattern is one circuit network. The impedance is measured using a circuit board inspection device, and the required tolerance is set as reference data. Thereafter, several inventions were previously proposed for circuit board inspection methods in which the impedance of the circuit network of the inspected lot board is measured in the same manner as for non-defective boards, and the data is compared with the above-mentioned reference data to determine pass/fail.

[0006] For example, one of them is the patent application 1986-129.
According to the prior invention of No. 724, since the measurement item is one impedance item, automatic measurement is possible without particularly requiring a complicated inspection program, and the board inspection can be completed in an extremely short time.

[0007]

[Problem to be Solved by the Invention] By the way, when a measuring pin is brought into contact with a land etc. of a board, the contact resistance is usually 1.
It is about 0 to 20 mΩ and can be ignored, but when the number of boards increases, solder powder generated from the land portion due to repeated contact may adhere to the pin tip, increasing contact resistance and causing contact failure. Therefore, even if the impedance of the network is within an acceptable range, contact resistance is added to the measured value.
If it exceeds the allowable upper limit value, the device determines that it is defective (NG).

In this case, the person in charge of the inspection, for example, looks at the printed out NG judgment data and determines whether the problem is due to poor contact of the measuring pin or poor impedance of the circuit network itself, or whether the measuring pin is not connected properly. The board is then moved away from the board, the tips of the pins are cleaned, and measurements are taken again to determine if there is any effect of contact resistance.

However, in the former case, the person in charge requires experience, and the judgment may differ depending on the person. In the latter case, if the number of pins increases, cleaning them becomes extremely troublesome, which is not preferable in any case.

[0010] This invention was made in consideration of the above circumstances, and its purpose is to ensure that impedance measurement data is NG.
It is an object of the present invention to provide a method for detecting poor contact of a measuring pin, in which a circuit board inspection device detects whether or not there is a poor contact of the measuring pin when the determination is made.

[0011]

[Means for Solving the Problems] FIG. 1(A) is an overall configuration diagram of an embodiment of a circuit board inspection apparatus to which the present invention is applied. For example, 1 is a signal source that emits an AC signal for measurement, and 2 is not shown. The circuit boards to be tested, N1, N2, etc., are set in the apparatus using a holder, and measurement pins are implanted in a pin board (not shown) facing the above board, and by moving the pin board, a predetermined measurement of the above board is made. It is designed to touch a point. Reference numeral 3 denotes a scanner consisting of a group of relays, and an example in which there are four measurement pins is shown in FIG. It is designed to be connected by switching.

The measuring section 4 includes, for example, an amplifier 5, an A/D converter 6, and a controller 7. The controller 7 controls signal generation to the signal source 1, controls relay switching of the scanner 3, controls input range switching of the amplifier 5, and controls the input range of the amplifier 5. A/D
It takes in the data from the converter 6, measures the current flowing through the circuit board, calculates the impedance of the board, compares it with reference data collected from non-defective boards to determine whether it is good or bad, and transfers the necessary data to the recording unit 8. It can be displayed or printed out. Their functions are shown in FIG. 1(B).

Referring to FIG. 1(B), in order to solve the above problem, for example, the controller 7 is equipped with the following means (1) to (3).

(1) Among the measurement pins N1, N2, . Test setting means 11 between one pin and all other pins is sequentially switched and connected to perform impedance measurement between the one pin and all other pins.

(2) Two-pin test setting means 12 for connecting one pin connected to the measuring section 4 to a signal source sequentially from all other pins, and measuring the impedance between them.

(3) Find the minimum data among the impedance data obtained in the 2-pin test in (2) above, add the required positive value to that data, and use it as a comparison standard for contact failure detection. Data holding means 15 for holding data.

[0017]

[Operation] First, the impedance between one pin and all other pins is measured by the above means (1) and the impedance between 2 pins is measured by the above means (2) on a mounting board that has been confirmed to be good in advance, Upper and lower limit tolerances +α% and -β% are given to the measurement data (1), respectively, and stored in the data storage means 15 as reference data for quality determination.

Regarding the measurement data in (2), for the impedance data between two pins showing the minimum value, the allowable maximum value of contact resistance + γ is determined by the method in (3) above.
% is added and stored in the data holding means 15 in the same manner as described above as comparison reference data for detecting poor contact.

Thereafter, the impedance measurement between one pin and all other pins according to (1) above is performed on the inspected lot board in the same manner as for the non-defective board, and the reference data collected from the non-defective board in the comparison/judgment means 16 is measured. Compare with and judge whether it is good or bad.

In this case, for the inspected lot board that is determined to be defective, the 2-pin test according to (2) above is performed for the pins with the same pin number as the two pins that showed the minimum value in the 2-pin test of the above-mentioned non-defective board. The impedance between them is measured, and the data is compared with the comparison reference data for contact failure detection in (3) above, which is collected from non-defective boards in the comparison/judgment means 16.

Here, for example, if the measured value ≦ the comparison reference data for contact failure detection, a normal "NG" judgment is made due to a defective part, etc., and if the measurement value > the comparison reference data for contact failure detection, then "good contact" is determined. A determination of "NG" is made and displayed on the display section 8.

[0022]

[Example] A method of collecting impedance data from a non-defective board using the above problem solving means (1) and creating reference data for pass/fail judgment, and a method of collecting impedance data between two pins using the same means (2). Since the method is the same as the content of the prior invention, it will be briefly explained below.

In FIG. 1A, first, a non-defective board 2a is set in the circuit board inspection device, and impedance measurement data between one pin and all other pins is collected by the above means (1) and used for pass/fail judgment. Create standard data. An example of this will be explained with reference to FIG.

In FIG. 2A, which shows a relay circuit inside the scanner 3 of FIG.
R5, and its resistance value is as shown in the figure. In addition, measurement pins N1 to N4 are in contact with the four measurement points of the circuit network, respectively, and these pins are connected to the signal source 1 or the measurement unit 4 by relays S1a, S1b to S4a, and S4b in the scanner 3. It is assumed that the

For example, if pin N4 is connected to the measuring section 4 side, and all other pins N1 to N3 are connected to the signal source 1 side to measure the impedance therebetween, the operation of the relay is as shown in FIG. As shown in (A), S4b is on and S1b
~S3b is turned off, S4a is turned off, and S1a~S3a are turned on. This state is shown in FIG. 2(C).

The method for driving this relay is shown in FIG. 1 above, for example.
The test mode setting means 9 (B) specifies a test between one pin and all other pins. As a result, the scanner control means 1
The test setting means 11 between 1 pin in 0 and all other pins is activated. For example, when this is input using a keyboard (not shown), the test setting means 11 between one pin and all other pins sends a drive current to relay S4b to connect pin N4 to the measuring section side. Further, for the relays S1a to S4a, drive currents are sent to the relays S1a to S3a by, for example, the above-mentioned inverted signal, and the pins N1 to N3 are connected to the signal source side. In the case of this pin connection, the impedance viewed from the measurement unit side to the circuit network side via pin N4 is defined as Z4.

Here, when a "measurement" command is given, for example, using a keyboard (not shown), the signal source 1 generates a measurement AC voltage of a predetermined level and applies it to the circuit network to be measured via the pins N1 to N3. As a result, current flows from the signal source 1 to the measuring section 4 via the circuit network and pin N4. The measuring section 4 measures this inflow current to obtain the impedance Z4. For example, in the measurement of Figure 2(C), Z4=29.70
Ω, which is shown in the top column of FIG. 2(D).

Further, a tolerance range of an upper limit value +α and a lower limit value −β is set for the value of Z4 and used as reference data. Here, an example in which α=β=10% is shown at the right end of the above top column. Below, do the same for the other pins.
Perform pin-to-all other pin-to-pin tests, each shown in Figure 2 above.
The data holding means 15 creates the reference data shown in (D).
(FIG. 1(B)).

Next, a method of creating comparison reference data for detecting poor contact will be explained. In addition, in FIG. 3A, which has the same configuration as FIG. Assume that the two-pin impedance between pins N4 and N3 is measured for the same circuit network as described above in 2a. In this case, as shown in FIG. 3A, relay S4b is on and S1b to S3b are off, and relay S3a is on and S1a, S2a, and S4a are off. This state is shown in FIG. 3(B). In the connection shown in FIG. 3(B), the impedance viewed from the measuring section side to the circuit network side via pin N4 is Z4.3.

The relay driving method is, for example, by specifying a test between two pins using the test mode setting means 9 (FIG. 1(B)).
2-pin test setting means 12 in the scanner control means 10
put it into operation. Next, and are input by key operations on a keyboard (not shown), for example. As a result, the two-pin test setting means 12 sends a drive current to the relays S4b and S3a, and connects the pins N4 and N3 to the measuring section 4 side and the signal source 1 side, respectively.

When "measurement" is commanded using the keyboard, for example, the signal source 1 emits an AC voltage for measurement, and the response current flows into the measurement section 4 via the pin N4. The measuring section 4 measures this current to determine the impedance Z4.3 between the two pins.

Next, with pin N4 connected to the measuring section side, pins N2 and N1 are sequentially connected to the signal source side, and impedances Z4.2 and Z4.1 therebetween are measured. Similarly, when pins N3, N2, and N1 are sequentially connected to the measurement unit side and one of the other pins is connected to the signal source side and the impedance between the two pins is measured, the data shown in Figure 3 (C) is obtained. can get.

[0033] Here, the minimum value is found from the impedance measurement values between one pin connected to the measuring section side and another pin connected to the signal source side. For example, when pin N4 is connected to the measurement unit side and other pins are connected to the signal source side, the measurement data is Z4.3, Z4.2, and Z4.1, but Z4.3 is 29. Since it is the smallest at 71Ω, it is taken as the minimum value.

Comparison reference data for contact failure detection is created by adding a positive value +γ to this minimum value. Figure 3 above (
C) shows an example in which comparison reference data is created by setting the minimum value extracted from the impedance measurement value between two pins of each pin and the above-mentioned γ to be added to this minimum value to be, for example, 10% of the minimum value. Here, the reason for using the minimum value of the impedance between two pins and the additional value γ will be explained.

Regarding the minimum value of the impedance between two pins, if there is contact resistance between the circuit network and the measurement pin, the measurement impedance=the original impedance of the circuit network+the contact resistance. In this case, if there are a large number of pins involved in the measurement, it will be difficult to detect which pin has poor contact, so the number of pins is set to the minimum number, that is, two.

Furthermore, according to the above equation, the smaller the inherent impedance of the circuit network, the larger the ratio of contact resistance to the measured value is, and therefore the easier it is to detect pins with poor contact. Therefore, for example, if the contact resistance of the measurement pin is 10 to 20
The impedance between two pins of a good board is measured at a normally negligible value such as mΩ, and the minimum value is used.

Next, the additional value γ will be explained. In addition,
In FIG. 2(B) or FIG. 3(B), the resistance values of the resistors R1 to R5 forming the circuit network represent nominal values. Here, it is assumed that a resistor having a value substantially equal to the nominal value is used in a non-defective board, and a resistor having a tolerance of ±10% from the nominal value is used in the inspected lot board. Then, the minimum value of the impedance between two pins obtained by measuring the inspected lot board will vary from -10% to + around the minimum value obtained from the good board.
It will vary within a range of 10%.

However, since a lot of substrates to be inspected generally use a mixture of resistors with negative tolerance and resistors with positive tolerance, the actual range of variation is averaged out and becomes narrower than the above. If there is contact resistance on the measurement pin, the minimum value measured will increase by the amount of contact resistance, so if the minimum value of a good board is used as a reference, the allowable upper limit of contact resistance is set higher than that. In this embodiment, a certain value +γ is added to the minimum value of a non-defective board to obtain an allowable upper limit value, that is, comparison reference data for detecting poor contact. Figure 3 (C) above
In practical terms, this additional value + γ is set to, for example, 10% of the minimum value of a good board for a general circuit network, but it is not possible to decide the value of γ depending on the severity of the function required of the circuit network. Of course.

The above is an example of creating comparison reference data for contact failure detection using one minimum value data from a plurality of 2-pin impedance measurement data, but if there is enough memory (data holding means 15) In this case, two comparison reference data may be created using the minimum value and the next smallest measurement data. For example, the measuring part side pin N4 in Fig. 3(C) above
As shown in the figure, the minimum value is 29.71Ω (Z
4.3) In addition to the comparison standard data of 32.7 Ω, use the next smallest value of 48.67 Ω (Z4.2) and set the 10% increase to 53.5 Ω as the comparison standard data.

[0040] In this way, for example, if the test data Z4.3 between two pins of the inspected lot board becomes Z4.3>comparison standard data (32.7Ω) and it is determined that there is a poor contact, the test data between pins N4 and Which side of N3 has poor contact can be determined by the 2-pin impedance Z4 between pins N4 and N2.
This can be easily determined by measuring 2 and comparing it with the other comparison reference data (53.5Ω) mentioned above.

For example, if Z4.2>comparison standard data (53.5Ω), there is a poor contact on the pin N4 side, and if Z4.2≦comparison standard data (
53.5Ω), it can be seen that there is a contact failure on the pin N3 side.

Incidentally, FIG. 4 shows a flow diagram of an example in which a circuit board inspection apparatus is used to detect a contact failure. An overview of each step will be explained below.

P1...Measure the impedance between one pin and all other pins for each circuit network on a non-defective board, and collect the data.

P2... Desired tolerances +α and -β are set to the data collected in P1 to create reference data for determining the quality of the board.

P3...Measure the impedance between two pins of the above circuit network and collect the data.

P4...The minimum value is extracted from the data collected in P3, and a desired value + γ is added to create comparison reference data for contact failure detection.

[0047] P5...If the data collection is not completed, the process returns to P1, and when it is completed, the testing of the lot board to be inspected begins.

P6...The same measurement as P1 is carried out on the lot substrates to be inspected.

P7...The measurement data of P6 is compared with the standard data for quality determination (P2).

P8...If it is determined to be defective (NG), impedance is measured between two pins having the same number as the pin showing the minimum value of P4.

P9...The measured data of P8 is compared with the comparison standard data for contact failure detection (P4), and if the measured data≦comparison standard data, then it is a normal defect due to parts, etc., and if the measured data>comparison standard data, then It is determined that the defect is due to poor contact.

P10, P11...The determination results of P9 are displayed respectively.

[0053]

[Effect] As explained in detail above, in this invention, first, the impedance measurement between 1 pin and all other pins and the impedance measurement between 2 pins are performed on the circuit network of a good board, and the measured value of the former is For each, upper and lower tolerance limits are set to create reference data for board pass/fail judgment, and for the latter measurement value, the minimum measurement value between one pin on the measuring part side and one pin on the signal source side is created. A positive predetermined value is added to each value to create comparison reference data for contact failure detection.

Thereafter, the impedance between one pin and all other pins was measured for the circuit network of the inspected lot board using the same method as for non-defective boards, and compared with the above standard data for pass/fail judgment. There is. Here, if the measured value is outside the allowable range of the above standard data and is determined to be defective, the signal source side pin that has the minimum impedance between the two pins with respect to the measurement unit side pin of the relevant measurement step. The impedance between them is measured using the same method as for the non-defective board, and the value is compared with the comparison reference data for contact failure detection. In this case, for example, if the measured value≦comparison standard data, it is determined that it is a normal defect due to a defective part or the like, and if the measured value>comparison standard data, it is determined that there is a contact failure, and these are displayed.

Therefore, according to the present invention, since the device automatically determines whether there is a contact failure by comparing the measured data with the reference data, the thinking and judgment of the person in charge of the inspection are not required, and there are no artificial differences in the determination. This is extremely advantageous in increasing the efficiency of board inspection.

[Brief explanation of the drawing]

[Fig. 1] (A) Block diagram showing the overall configuration of a circuit board inspection device to which the present invention is applied. (B) Block diagram showing the internal functions of a controller.

[Figure 2] (A) Connection diagram for explaining the test between 1 pin and all other pins (B) Configuration diagram of the circuit network to be measured (C) Connection diagram for the test between 1 pin and all other pins in the circuit network to be measured Figure (D) Explanatory diagram of how to create standard data for testing between 1 pin and all other pins

[Figure 3] (A) Connection diagram for explaining the 2-pin test (B
) Connection diagram for 2-pin test in the circuit network to be measured (C) Explanatory diagram of how to create comparison standard data in the circuit network to be measured

[Figure 4] Flow diagram showing the procedure for automatically detecting poor contact

[Explanation of symbols]

1 Signal source 2 Inspected lot board 2a Good board 3 Scanner 4 Measuring unit 11 Test setting means 12 between 1 pin and all other pins
2-pin test setting means 14 Impedance calculation means 16 Comparison/judgment means N1, N2,... Measuring pins

Claims (1)

[Claims] [Claim 1] A plurality of measurement pins are brought into contact with predetermined pattern positions on a mounted circuit board that has been previously confirmed to be non-defective, and one of the pins and all the other pins are sequentially switched and connected to a measurement unit and a signal source, respectively, using a scanner. Each time, an AC voltage for measurement is emitted from the same signal source to the above-mentioned good board, and the response current signal is taken into the measuring section through the above-mentioned one pin, and the circuit network of the good board at the same pin position is connected to one pin versus the other. Measure the impedance between all pins of the board to create reference data, then measure the impedance of the circuit network of the test lot board using the same method as above, and compare the measured value with the reference data created from the above-mentioned non-defective board. In a circuit board inspection device that determines the quality of a circuit board by sequentially combining one pin of the measuring section and one of the plurality of pins on the signal source side,
In addition to measuring the impedance of a good board between pins in advance, a positive predetermined value related to the accuracy of the function required by the circuit network is determined for the minimum value among multiple measurement data obtained for the same pin on the measurement unit side. The value is added and used as comparison standard data for detecting poor contact, and if the inspected lot board is determined to be defective by impedance measurement between 1 pin and all other pins, the impedance between 2 pins of the above-mentioned non-defective board is Measurement in a circuit board inspection device characterized by measuring the impedance between two pins of a defective board at the same pin as the pin showing the minimum value, and determining a contact failure when the measured value exceeds the comparison reference data. Method for detecting poor contact of pins.