JPH0758316B2 - Circuit board inspection method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a circuit board inspection method for inspecting the quality of a circuit board on which electronic components and the like are mounted.

[Conventional example]

Circuit board inspection devices called in-circuit testers have come to be used for inspection of circuit boards on which electronic components are mounted.

This type of device is generally provided with a direct current and an alternating current and a voltage source as a signal source for measurement, and appropriately uses them depending on the measurement item, but the device is relatively complicated because there are many types of signal sources. In addition, it has drawbacks such that it takes a long time for measurement and a user needs a large load to create an inspection program or the like.

In view of these circumstances, the present applicant measures the impedance of a substrate to be inspected by using an AC voltage as a signal source and compares it with data obtained by measuring from a substrate which is confirmed to be a non-defective product in advance to judge its quality. Therefore, several inventions and inventions of an in-circuit tester which is fast and does not require programming on the user side have been proposed.

The outline of the invention according to Japanese Patent Application No. 63-129724, which is one of them, will be briefly described with reference to FIG. 4. A circuit board to be inspected (hereinafter referred to as “test board”) 1 is, for example, a circuit pattern. 2a to 2e and electronic parts 3a to 3c mounted between the respective patterns, and the pins P _{1 to} P ₄ from the device body ₄ are in contact with the same pattern. These pins are, for example, signal source side relays S _{1 to} S ₄ in the scanner 5 and measuring section side relays.
The signal source 6 and the measuring unit 7 are connected via S ₁ ′ to S ₄ ′, respectively, and the ON / OFF of each relay is driven by the measuring unit 7. The signal source 6 is also controlled by the measuring unit 7 so that an AC voltage of a predetermined frequency is sent out for one cycle per measurement.

In the invention of this prior application, for example, one pin is attached to the measuring unit 7.
And all other pins are connected to the signal source 6 and the impedance between them is measured by the current flowing into the measuring unit 7 via the above-mentioned one pin, but it is specified especially for the low impedance part of the test board. The two pins are designated and connected to the measuring unit 7 and the signal source 6, respectively, and the impedance between them is measured. Here, the former is abbreviated as "measurement between one pin and all other pins", and the latter is abbreviated as "measurement between designated pins".

As described above, when conducting a board inspection, the impedance of a plurality of boards confirmed to be non-defective is measured and the data is collected, but the above-mentioned invention of the prior application specifies measurement between one pin and all other pins. Pin-to-pin measurement can be done either manually or automatically. An example of manual measurement between one pin and all other pins by manual will now be described. For example, one of the good substrates is set in the device, and the measurement unit 7
The pin P ₁ connected to is designated by a key on the keyboard (not shown). Thus, the control signal as shown from the measuring unit 7 to Step 1 of FIG. 5 for example to the scanner 5 is issued, the measurement portion of the relay S ₁ 'another relay ON (1)
S ₂ '~S _4' is OFF (0) and, S ₁ each relay of the signal source side each by the inverted signal off (0), S ₂ '~
S _i ′ is turned on (1).

Simultaneously with the ON / OFF control of the relay, a measuring AC voltage is sent from the signal source 6 for one cycle, and the impedance of the substrate for the positive half wave and the negative half wave is measured. Thereafter, when the pins P ₂ to P _{4 are} measured in the same manner, the test step and the impedance measurement data of each step are loaded into the memory (not shown) of the measuring unit 7.

For other non-defective boards, the pins P ₁ to P _{4 are} automatically measured according to the inspection step formed by the above-mentioned manual measurement, and the comparison reference value and the upper limit value of the tolerance to it and the comparison reference value are calculated according to the impedance data of these non-defective boards. Find the lower limit and put it in the memory. After that, the inspection of the test board is started, and the measurement data is compared with the above-mentioned reference value to judge the quality.

The above-mentioned measurement between one pin and all other pins is performed, for example, with the input range (not shown) of the measuring section 7 fixed, but a low-impedance element such as a large-capacity capacitor or small-inductance coil is mounted on the substrate. When attached, it may be difficult to distinguish it from a short due to a bridge or the like. In such a case, the input range is switched to the lowest range, the measurement between designated pins is performed, and the value is confirmed. Usually, the measurement system has an impedance of about 5Ω due to wiring, etc., and in consideration of this, for example, the minimum comparison value K (≈5Ω) is set, and the measured value> K
If so, it is determined not to be short-circuited, and if the measured value is K, it is determined to be short-circuited.

The measurement between the designated pins will be supplementarily described with reference to FIG. 6 in which the main part of FIG. 4 is omitted. For example, a jumper wire JP is provided between the patterns on the substrate 1 and a resistor R having an impedance of more than 5Ω is used. And capacitor C
Was installed. In this case, since it can be expected from the beginning that the impedance of the jumper wire JP is small, the specified pin-to-pin measurement by the pins P ₁ and P ₂ is set for the jumper wire JP. That is, as shown in the figure, the measuring unit side relay S ₁ ′ of the pin P ₁ is on and the signal source side relay S ₁ is off,
The measurement section side relay S ₂ ′ of the pin P ₂ is turned off, the signal source side relay S ₂ thereof is turned on, and the relays of the pins P ₃ and P ₄ are all turned off. In this state, measure the impedance between P ₁ and P ₂ ,
It is confirmed that the measured value K works as a jumper wire.

For the resistor R and the capacitor C, for example, the measurement between one pin and all other pins is set as shown in FIG. That is, the measuring unit side relay S ₂ ′ of the pin P ₂ is turned on and the signal source side relay S ₂ thereof is turned off, and the measuring unit side relays S ₁ ′, S ₃ ′ of the pins P ₁ , P ₃ , P ₄ are S ₄ ′ is off. In this case, pins P ₃ , P
₄ the signal source-side relay S ₃ and S ₄ of the turns on but the signal source-side relay S ₁ pin P ₁ is fixed to OFF. The reason is that if this relay S ₁ is turned on like any other relay, the impedance of the jumper wire, which is almost zero, is added in parallel to the impedance between the pin P ₂ and the other pins P ₃ and P _4.
This is because the measurement between the pin and all other pins becomes meaningless. Therefore, a control table for each signal source side relay S _{1 to} S ₄ is prepared in a memory (not shown) in the measuring unit 7,
Other when a low impedance detection was performed by between specified pin measurement, relay forming the relay and pair of connecting the pin to the measuring section, i.e. in the illustrated example is written in the control table specific mark data to the S ₁ It is distinguished from the relay of No. 1 and is kept in a non-operating state in the subsequent inspection steps.

In this way, from the non-defective board, the measurement between 1 pin to all other pins, or the measurement between 1 pin to all other pins and the specified pin measurement step is configured, and the impedance reference value and the tolerance for it at each step, After setting the control table for the signal source side relay, the measurement of the test board is started.

[Problems to be Solved by the Invention]

The above-mentioned invention of the prior application has an advantage that the inspection step of the test board automatically proceeds if the non-defective board is measured and the data is collected in the memory and each relay is turned on and off according to the relay control table.

By the way, in the board inspection, for example, as a pre-inspection, first, the measurement between designated pins is performed to check the presence or absence of a circuit pattern disconnection, a solder bridge, or a conduction failure such as a through hole, and then a book for measurement between one pin and all other pins. It is desirable to enter an inspection. In this case, in the prior invention, one contact pin is provided for each pattern as in the case of a general in-circuit tester, and the position thereof is the pattern as shown by the solid line in FIGS. 8 (A) and 8 (B). It is decided in consideration of the shape and so on. Therefore, when checking the pattern itself for disconnection or poor continuity, it is necessary to provide a dedicated pin at a position avoiding the above pins as shown by the dotted line in the figure, which is not preferable because it takes time to set the pins. was there.

The present invention has been made in consideration of the above circumstances, and an object thereof is to eliminate the troublesomeness of setting dedicated pins, to conduct a continuity inspection of patterns, through holes, etc., and to measure the impedance of a board including mounted components. It is an object of the present invention to provide a method for inspecting a circuit board that is continuously performed.

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides one pin and all other pins, or one of two specific two pins and another one pin among a plurality of pins contacting each pattern of a circuit board to be inspected. Connected to the measurement unit side and the signal source side by the relays provided corresponding to the above pins, respectively, and sequentially switching them according to the measurement step, and from the signal source to the circuit board under test, an AC signal for measurement is sent. Supply the response signal to the measuring unit and measure the impedance of the circuit board to be inspected at each inspection step by measuring between one pin and all other pins, or by measuring between specific pins. In the circuit board inspection method of comparing the reference value previously obtained from the board and determining the quality of the circuit board to be inspected, each of the pins is connected to each pattern of the non-defective board. After arranging so as to contact the formed land, for each land of the same quality substrate, the above-mentioned measurement between 1 pin and all other pins is performed, and a predetermined value is measured between that 1 pin and any one other pin. When the following impedance is detected, a pin-to-pin measurement step is performed to perform impedance measurement only between the two pins, and the above-mentioned relay corresponding to the pin that is determined to be pin-to-pin measurement is also measured. In the measurement steps other than the step, the signal source is set to the non-connection state, and in the measurement of the circuit board to be inspected, first, the pin-to-pin measurement step is performed, and then the remaining pins are paired with one pin. The feature is that the measurement between all other pins is performed.

[Action]

By providing the above means, for example, by specifying pins contacting two lands on the same pattern and performing pin-to-pin measurement, it is possible to detect whether the lands are good or bad and whether or not there is a pattern break between the lands. .

After the inspection, the impedance of the test board including the mounted components can be found by performing the measurement between one pin and all the other pins, as in the above-mentioned prior invention.

〔Example〕

As shown in FIG. 1, in this embodiment, there are n pins which contact the lands formed in each pattern of the test substrate 1, and in the illustrated example, there are six pins P _{1 to} P ₆ . Although not shown for the convenience of drawing, the signal source side relay and the measurement unit side, which connect the pins P _{1 to} P ₆ to the measurement unit 7 and the signal source 6, respectively, are provided in the scanner 5 as in the above-mentioned prior invention. Each relay is provided. Further, the measuring section 7 is provided with a measuring mode setting means 7a made of software, for example, but it has substantially the same configuration as the measuring section of the invention of the prior application shown in FIG.

Now, assuming that a non-defective board is set as the board to be inspected and the data is collected, for example, from the pins P ₁ to P _{6 in} order by measuring between one pin and all other pins, step 1 in FIG.
As shown in FIG. 2, the pin P ₁ is connected to the measuring unit 7 by a measuring unit side relay (not shown) in the scanner 5, and the pins P _{2 to} P ₆ are connected to the signal source 6 by signal source side relays. However, the pin P ₁ and P ₂ are short-circuited by the jumper wire JP, so it is judged as the minimum comparison value K (5Ω) or less and the pin-to-pin measurement by the pins P ₁ and P ₂ is automatically set, and at the same time. The pins P _{3 to} P _{6 which} are once connected to the signal source 6 are turned off by a relay (not shown) of the scanner 5.

At the time of this pin-to-pin measurement, the other signal source side relay paired with the relay connecting the pin P ₁ to the measuring unit 7 is fixed to OFF by a relay control table (not shown) of the measuring unit 7. Therefore, in the next step 2, pin P ₂
When P is connected to the measuring unit 7, P ₁ becomes inactive (marked with Δ), and the pins P _{3 to} P ₆ are connected to the signal source 6. in this case,
Pattern 2b between P ₂ and P ₃ is short-circuited and K (5
Ω) or less, the inter-pin measurement is automatically performed as in the case of step 1, and the pins P _{4 to} P ₆ are switched off. At the time of this pin-to-pin measurement, the relay connecting the pin P ₂ to the signal source 6 is fixed to OFF by the relay control table (not shown) as in the case of step 1 above.

In step 3, the pin P ₃ is connected to the measuring section 7, the pins P _{4 to} P ₆ are connected to the signal source 6, and the measurement between all the other pins is performed for each pin. In step 4, the measurement between the pin 1 (P ₄ ) once set and all the other pins (P ₃ , P ₅ , P ₆ ) is performed by the pattern 2d through the through hole.
The short-circuited state is caused by, and similarly, the measurement is switched to the pin-to-pin measurement of the pattern 2d by P ₄ and P ₅ , and in steps 5 and 6, the pins P ₅ and P ₆ are connected to the measurement unit 7 respectively, and the 1-pin pair Pin-to-pin measurements are taken.

That is, when low impedance detection is performed by measurement between designated pins, the signal source side relay of the pin connected to the measurement unit is fixed to OFF by the relay control table, and that pin is connected to the signal source in the subsequent inspection step. It is supposed not to be done.

When the measurement of the non-defective substrate is completed as described above, for example, 6
In steps 1, 2, and 4, measurement between designated pins is automatically generated, and the data is collected in a memory (not shown) in the measuring unit 7. Also, for steps 3, 5, and 6, the measurement between one pin and all other pins is performed, and the data is similarly collected.

Next, the test board 1 is set in the apparatus and inspected. In this case, for example, the specified pin measurement step and the 1-pin-to-all other pin measurement step for each of the remaining pins are automatically set from the data collected in the memory (not shown) by the measurement mode setting means 7a. It This allows
The measuring unit 7 first executes the inspections in steps 1, 2, and 4, and then executes the inspections in steps 3, 5, and 6.

In the measuring step between designated pins, as described above, as a pre-inspection, defective soldering of jumper wires in each land, defective conduction of through holes, presence or absence of pattern breakage, etc. are detected. Further, in the step of measuring between one pin and all other pins, impedance measurement of the mounted component, detection of solder bridge, component omission, reverse mounting of diode, electrolytic capacitor and the like are performed.

Note that FIG. 3 is a flow chart showing an example of automatically controlling the inspection by a microcomputer, for example.

〔effect〕

As described above in detail, in the present invention, the pins that come into contact with the lands of the board confirmed to be non-defective are provided,
For example, while collecting the data in the memory by measuring between one pin and all other pins, at the low impedance part of the board, a specified pin measurement step with two pins is automatically generated and executed, and the data is similarly measured. To collect.

Therefore, the specified pin-to-pin measurement step generated on the non-defective board is applied to, for example, the pre-inspection of the test board to perform the measurement, and then the above-mentioned 1-pin-to-all other pin-to-pin measurement step is performed to the main inspection of the test board. When applied and measured, the former measurement can detect pattern breaks, land conduction defects, etc.
With the latter measurement, it is possible to detect the impedance measurement of the board including the mounted component, the component omission, the solder bridge, the reverse of the component, and other necessary items for determining the quality.

In addition, since it is only necessary to provide a pin at a position facing each land on the board, when setting one pin for one conventional pattern, the pin is positioned while considering the shape of the pattern, and for pattern inspection. This eliminates the hassle of separately setting the dedicated pin of.

[Brief description of drawings]

1 to 3 relate to an embodiment of the present invention, FIG. 1 is a block diagram showing a configuration of a circuit board inspection apparatus to which the present invention is applied, and FIG. 2 is an explanatory view of a contact pin connection state, FIG. 3 is a flow chart showing an example of a case where a substrate inspection is automatically controlled by a microcomputer, and FIGS.
FIG. 4 shows an example of a conventional apparatus, FIG. 4 is a block diagram showing the apparatus configuration, FIG. 5 is an operation explanatory view of a scanner relay, and FIG.
FIG. 7 and FIG. 7 are schematic diagrams of the main part of the apparatus, and FIGS. 8A and 8B are explanatory diagrams of dedicated pin setting. In the figure, 1 is a circuit board to be inspected, 2a to 2e are patterns, 5
Is a scanner, 6 is a signal source, and 7 is a measuring unit.

Claims (1)

[Claims] 1. Among a plurality of pins contacting each pattern of a circuit board to be inspected, one pin and all other pins, or one of two specific two pins and the other one pin correspond to the above pins. Connected to the measuring section side and the signal source side respectively by the provided relays and switching them sequentially according to the measurement step, and supplying the measuring AC signal from the signal source to the circuit board under test The impedance of the inspected circuit board at each inspection step is measured by measuring the pin-to-pin value with all other pins or a specific pin-to-pin measurement, and the measured value and the non-defective board are obtained in advance. In the circuit board inspecting method for comparing the standard value that is present to determine the quality of the circuit board to be inspected, each of the pins described above is attached to a land formed in each pattern of the non-defective board. After arranging so as to make contact with each other, for each land of the non-defective board, the above-mentioned measurement between 1 pin and all the other pins is performed, and an impedance of a predetermined value or less is detected between the 1 pin and any one of the other pins. In this case, a pin-to-pin measurement step that performs impedance measurement only between the two pins is generated, and the relay corresponding to the pin that is determined to be pin-to-pin measurement is used in the measurement steps other than the pin-to-pin measurement step. Set to the non-connection state with respect to the signal source, in measuring the circuit board to be inspected, first,
A method for inspecting a circuit board, wherein the pin-to-pin measuring step is carried out, and thereafter, the pin-to-pin and all other pins are measured for each of the remaining pins.