JPH05164803A - Open test device for in-circuit tester - Google Patents

Abstract

PURPOSE:To reduce inaccuracy of judgement on test results faking place at the time of the contact inferiority of a probe. CONSTITUTION:An open device is provided with a means 42 which prepares criterions by using a good quality printed-circuit board 28, and when the measured resistance at a specified position on the said board exceeds the value inputted, the inputted value is decided as the primary criterion value, and when the measured resistance by the maximum range of resistance measurement at the same position exceeds the maximum range value, the secondary criterion is set up as the over-range, and, in the case where the measured resistance is less than the maximum range value the secondary criterion is set up as being in the range over the primary criterion value. Moreover, the device is provided with an open test means 48 for a printed- circuit board 28 to be tested, and judges whether the measured resistance value at the same position on the printed-circuit board 28 to be tested is over the primary criterion value or not. Hence it is judged whether the specified position is in a short circuit condition or not. When the measured resistance exceeds the maximum range value, the same position is measures again with the maximum range. And in the case where the measured resistance is over the maximum range value, a second criterion judging means 46 decides that the measured resistance is in the over range, and while in the case where the measured resistance is less than the maximum range, the secondary criterion whether the measured resistance is in the range over the primary criterion value or not. Hence the device can judge whether a probe is in contact inferiority or not.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an open test device for an in-circuit tester used for judging the quality of a mounting board.

[0002]

2. Description of the Related Art Conventionally, a mounting board, that is, a printed circuit board to which a large number of electric components are soldered, is judged by using an in-circuit tester. At that time, a probe is appropriately contacted with a necessary measurement point such as a component or a circuit network in each designated portion of the board, a signal such as voltage or current is applied, and electrical measurement is performed for various inspection items. The result of the above is comprehensively judged to judge the quality.

An open test is one of the items of board inspection by such an in-circuit tester. In the open test, the resistance is measured at each specified location on the board to be inspected, and if the measured value exceeds the reference value, it is regarded as a pass and "GO".
If the result is below the standard value, it is rejected and "NG"
To determine.

At that time, a resistance measuring device is often used in which a constant DC voltage is applied to a designated measurement point, a current value is read, and a resistance value is calculated.
Then, the resistance value as a reference value is basically created by measuring or logically obtaining each mounted component. However, finally, a non-defective substrate is determined and obtained from the measured value.

[0005]

However, in the case of the open test by the in-circuit tester, the reference value is not set for each designated place in this way, and the reference value is generally set to about several tens Ω. Moreover, if the measured value exceeds the reference value, it is determined as a pass, so that the determination result is "GO" even if the probe has a contact failure. Therefore, the board to be inspected cannot be accurately determined.

The present invention has been made in view of such conventional problems, and it is an object of the present invention to provide an open test device for an in-circuit tester capable of reducing the inaccuracy of judgment that occurs when a probe has a poor contact. To aim.

[0007]

Means for achieving the above object will be described below with reference to FIG. 1 which clearly shows the present invention. This open test device for an in-circuit tester has an operation unit 12, and is equipped with a resistance measuring device 40 that measures a resistance value at a preset designated position by bringing a probe into contact with the mounting substrate 28. Then, the judgment reference creating means 42 for creating the judgment reference for the open test using the non-defective substrate 28.
While inputting the temporary judgment reference value,
The primary judgment criterion determining means 4 for measuring the resistance value of the designated place in the range of 1) in the range corresponding to the input value, and determining the input value as the primary judgment criterion value when the measured value exceeds the input value.
4 and the resistance value of the same designated place is judged in the maximum range, and when the measured value exceeds the secondary judgment reference value corresponding to the maximum range value, the secondary judgment standard is set as overrange and 2
A secondary judgment reference setting means 46 is provided for setting the secondary judgment reference to a range range exceeding the primary judgment reference value when the value is equal to or smaller than the next judgment reference value.

Further, as the open test means 48 for the inspected substrate, the resistance value of the same designated place on the inspected substrate 28 is measured in the range corresponding to the primary determination reference value, and the measured value is the primary determination reference value. 1 to determine if it exceeds
When the next determination means 50 and its measured value exceed the primary determination reference value, the resistance value at the same designated location is measured again in the highest range, and when the measured value exceeds the secondary determination reference value, 2
The secondary determination means 52 determines whether the next determination criterion is overrange, and when the measured value is equal to or less than the secondary determination reference value, determines whether the secondary determination criterion is a range range exceeding the primary determination reference value.

[0009]

With the above-described structure, the resistance value of the designated portion on the non-defective substrate 28 is measured in the range corresponding to the input value by using the non-defective substrate 28 while inputting the temporary judgment reference value. When the value exceeds the input value, the input value is determined as the primary determination reference value. Furthermore, the resistance value of the same designated location is measured in the highest range, and when the measured value exceeds the secondary judgment reference value, the secondary judgment reference is set as overrange, and when the measured value exceeds the secondary judgment reference value, The secondary judgment standard is set as the range range that exceeds the primary judgment standard value.

Next, the resistance value of the same designated place on the inspected substrate 28 is measured in the range corresponding to the primary determination reference value, and it is determined whether the measured value exceeds the primary determination reference value.
At that time, if the measured value is less than or equal to the primary determination reference value, it is determined that the designated portion is in the short-circuited state. When the measured value exceeds the primary judgment reference value, the resistance value at the same designated position is measured again in the highest range, and when the measured value exceeds the secondary judgment reference value, the secondary judgment reference is exceeded. If the measured value is less than or equal to the secondary determination reference value, it is determined whether the range is a range in which the secondary determination reference exceeds the primary determination reference value. At that time, even if the measured value exceeds the secondary determination reference value, it is determined that the probe has a poor contact in the range range in which the secondary determination reference exceeds the primary determination reference value.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 2 is a block diagram showing the configuration of the open test unit of the fixture type in-circuit tester to which the present invention is applied. In the figure, 10 is an in-circuit tester, 12 is its operation unit, 14 is a measurement unit, 16 is a multiplexer, 18 is a display unit, and 20 is a calculation control unit. The operation unit 12 includes a keyboard, various switches and the like.
Therefore, by appropriately operating a key, a switch, or the like, data such as the primary determination reference value can be input from the outside, and the measurement range can be switched.

The measuring section 14 is provided with a DC constant voltage power source 22, a current measuring device 24, etc., which are connected to the multiplexer 16. Further, each channel output from a large number of switches provided in the multiplexer 16 is connected to a corresponding probe 26 provided upright on a fixture (not shown). Therefore, when the mounting board (the board to be inspected or the non-defective board) 28 mounted on the fixture is placed and the probes are brought into contact with the necessary measurement points such as the parts and the circuit networks at the respective preset locations set in advance, A constant voltage can be applied at each designated location, and the current flowing there can be measured. At this time, the arithmetic and control unit 20 controls the multiplexer 16 to select the switch corresponding to the designated portion in accordance with the set measurement order, and turn on and off the measuring unit 14 and each probe 26 as appropriate.

The display unit 18 includes a screen display device such as a CRT. Therefore, the data input from the outside, the set 1
Next, secondary determination reference values, “GO” and “NG” indicating pass / fail of designated locations, and determination results indicating contact failure of the probe can be displayed as appropriate.

The arithmetic and control unit 20 includes a CPU (central processing unit) 30, a ROM (read only memory) 32, and a RAM.
(Readable / writable memory) 34, input / output port 3
6, a microcomputer including a bus line 38 and the like. The CPU 30 corresponds to a central part of the brain of the microcomputer, which executes control over the whole according to instructions of a program and performs arithmetic and logical operations,
The result is also temporarily stored. In addition, peripheral devices are also controlled appropriately. The ROM 32 stores a control program for controlling the whole.

Further, the RAM 34 receives input data input from the outside, primary and secondary determination reference values, measured current values, determination results indicating pass / fail of specified locations, probe contact failure, and input from a floppy disk. Various data such as the open test determination reference processing program, the open test processing program, and the resistance value calculated by the CPU 30 are stored. The input / output port 36 is connected to the operation unit 12, the measurement unit 14, the multiplexer 16, various devices provided in the display unit 18, and the like. Further, the bus line 38 includes an address bus line, a data bus line, a control bus line and the like for connecting them, and is properly coupled to peripheral devices.

Next, the operation of this embodiment will be described. FIG. 3 is a flowchart consisting of steps P1 to P8 showing the operation of the open test judgment reference processing program. First, a non-defective substrate 28 of the same type as the inspected substrate 28 is used, the non-defective substrate 28 is placed and fixed at a predetermined location on the fixture, and the probe is brought into contact with the measurement points at each designated location.

Then, the processing by the program is started,
According to the measurement order preset in P1, a measurement point at one designated place to be measured is set. Then go to P2. At P2, the keyboard on the operation unit 12 is operated to input a temporary primary determination reference value a. Then go to P3. At P3, the resistance value at the specified location is measured in the range corresponding to the input value, and it is determined whether the measured value x exceeds the primary determination reference value a. YES
In case of, go to P4. At P4, the input value is confirmed as the primary determination reference value a.

If NO, the process returns to P2 and P3 returns YES.
Until the determination is made, the primary determination reference value a is adjusted and input. At that time, with respect to the measured value x, the primary judgment reference value a is determined in consideration of the allowable range at the time of inspection, but normally, it is several tens Ω.
Set to a degree. The resistance value x at the designated location is calculated from the known constant voltage v and the measured current value i using the equation x = v / i.

After confirming the primary judgment reference value a, the process goes to P5. P
In step 5, the highest measurable range is set, and the highest range value, for example, 10 MΩ is set as the secondary judgment reference value b. Then P
Go to 6. In P6, the resistance value at the same designated location is measured in the highest range, and it is determined whether the measured value x'is less than or equal to the secondary determination reference value b. If YES, go to P7. At P7, the secondary judgment reference c is set to L indicating that it is in the range exceeding the primary judgment reference value a, that is, the range exceeding the primary judgment reference value a and smaller than the secondary judgment reference value b.

If NO, go to P8. At P8, the secondary judgment criterion c is set to H indicating that it is over the range, that is, exceeds the secondary judgment criterion value b. It should be noted that if the maximum range is selected from a plurality of ranges provided for resistance value measurement and used, it can be surely judged whether it is overrange or contact failure of the probe. In this way, the primary determination reference value a and the secondary determination reference c are sequentially determined for each designated location.

FIG. 4 is a flowchart consisting of steps P10 to P19 showing the operation of the open test processing program. First, in place of the non-defective substrate 28, the substrate 28 to be inspected is fixed at a predetermined position on the fixture, and the probe is brought into contact with each measurement point at each designated position.

Then, the processing by the program is started,
According to the measurement order preset in P10, one designated measurement point to be measured is set. Then go to P11. P
In 11, the resistance value at the specified location is measured in the range corresponding to the primary determination reference value a. Then go to P12. In P12, it is determined whether the measured value x exceeds the previously determined primary determination reference value a. If NO, go to P13. In P13, it is determined that the designated portion is in the short-circuited state, and the rejection is "NG".

If YES, go to P14. In P14, the resistance value at the same designated location is measured again in the maximum range.
Then go to P15. At P15, it is determined whether the measured value x'is less than or equal to the secondary determination reference value b. If NO, go to P16. In P16, it is determined whether the previously determined criterion c is H.
If NO, go to P17. At P17, it is determined that the contact is poor. In this case, the probe is contacted well and the inspection is performed again. Therefore, it is possible to prevent such an error that the contact failure of the probe is uniformly determined as acceptable.

If YES is determined in P15, the process goes to P18. At P18, it is determined whether the previously determined criterion c is L. If YES or NO, go to P19.
In P19, it is judged as "GO" as a pass. Also, the previous P
Even if it is judged as YES in 16, go to P19 and "GO"
To determine. In this way, the open test is sequentially performed at each designated location.

When the determination in P18 is NO, it can be inferred that there is a problem in the circuit network, but it is uniformly determined as "GO" without determining as "NG" or the like in the short circuit state. This is because the failure of the circuit network is likely to occur due to variations in the parts used and has a very high probability of being found in other inspection steps or inspection items, and should be ignored in the open test.

Although the present invention is applied to the fixture type in-circuit tester in the above embodiment, it is naturally applicable to the in-circuit tester equipped with a fixtureless XY unit.

[0027]

According to the present invention described above, a primary judgment standard value and a secondary judgment standard are prepared as the judgment standard for the open test, and whether the designated parts of the primary judgment standard value are short-circuited or not. Since it is used to determine whether or not the contact state of the probe is good or bad, the inaccuracy of the determination that occurs when the probe has a poor contact can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an open test device for an in-circuit tester according to the present invention.

FIG. 2 is a block diagram showing a configuration of an open test unit of a fixture type in-circuit tester to which the present invention is applied.

FIG. 3 is a flowchart showing an operation by a judgment reference processing program for open test stored in a RAM of the in-circuit tester.

FIG. 4 is a flowchart showing an operation by an open test processing program stored in a RAM of the in-circuit tester.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... In-circuit tester 12 ... Operation part 14 ... Measuring part 16 ... Multiplexer 18 ... Display part 20 ... Arithmetic control part 26 ... Probe 28 ... Mounting board 40 ... Resistance measuring device 42 ... Open test judgment reference creating means 44 ... Primary Judgment criterion determining means 46 ... Secondary judgment criterion determining means 48 ... Open test means 50 ... Primary judging means 52 ... Secondary judging means

Claims (1)

[Claims] 1. An open test device for an in-circuit tester, comprising an operation unit, and a resistance measuring device for measuring a resistance value at a preset designated position by contacting a probe with a mounting board. As a judgment criterion creating means for creating the judgment criterion of (3) using a non-defective board, while inputting a temporary judgment reference value, the resistance value at the specified location on the non-defective board is measured in the range corresponding to the input value, and the measured value is When the input value is exceeded, the primary determination standard determining means for determining the input value as the primary determination standard value and the resistance value at the same designated location are measured in the maximum range, and the measured value corresponds to the maximum range value. When the secondary judgment reference value is exceeded, the secondary judgment reference is set to overrange, and when it is less than the secondary judgment reference value, the secondary judgment reference is set to the range range exceeding the primary judgment reference value 2 Next judgment A reference setting means is provided, and as an open test means for the board to be inspected, the resistance value at the same designated place on the board to be inspected is measured in the range corresponding to the primary judgment reference value, and the measured value is the primary judgment reference value. When the primary judgment means for judging whether or not it exceeds and the measured value exceeds the primary judgment reference value, the resistance value at the same designated location is measured again in the highest range, and the measured value exceeds the secondary judgment reference value. Determines whether the secondary criterion is overrange and the measured value is 2
An open test device for an in-circuit tester, comprising: a secondary determination means for determining whether the secondary determination reference is in a range exceeding the primary determination reference value when the secondary determination reference value is less than or equal to the secondary determination reference value.