JPH023146B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION After various electronic components are assembled on a printed circuit board, the present invention checks the contact state of a contact pin for signal extraction used in an adjustment machine or an inspection machine for the mounted printed circuit board with respect to the printed circuit board. The present invention relates to a device capable of determining and detecting a poor contact state.

For example, when inspecting whether the waveform at a certain measurement point on a mounted printed circuit board meets the standard, or when trying to adjust a semi-fixed volume or variable coil built into a printed circuit board. For example, as shown in Figure 1, the contact pin B for signal extraction of the inspection machine or adjustment machine A is brought into contact with the predetermined conductive pattern part D or connection lead part of the printed circuit board C to extract the signal for inspection and adjustment. I try to do this. Therefore, if there is dust or flux attached to the measurement points or other points where the above pins come into contact, or if the contact pins cause poor contact due to other reasons, accurate inspection and adjustment may be hindered. There is. Therefore, it is desirable to be able to clearly determine whether the contact condition of the contact pins is good or bad, but in conventional board adjustment inspection machines, no special consideration has been given to detecting poor contact of the contact pins. When adjustment is not possible or the test result is defective, it is not possible to distinguish whether this is due to malfunction of the printed circuit board itself or to poor contact between the contact pins and the printed circuit board.

Therefore, if adjustment is not possible or test results are poor,
Adjustments and inspections, such as re-checking, become complicated and cause a decrease in productivity.

Therefore, in view of the above-mentioned circumstances, the present invention has been devised to make it possible to judge whether or not the contact state of the contact pin for signal extraction to the printed circuit board is good or not, so that adjustment and inspection of the circuit board can be performed easily and accurately. The purpose is to try.

Furthermore, it is an object of the present invention to judge the contact state of the contact pins without requiring any unique operation or work for the judgment, and to connect the contact pins to the printed circuit board for normal board adjustment or inspection. The purpose of this is to obtain a judgment signal by the operation itself of touching the object.

Furthermore, another object of the present invention is to obtain a contact state determination signal indicating whether or not the contact pin is in contact with the circuit under test, and at the same time to obtain a detection output of a measurement point. It is.

Furthermore, it is an object of the present invention to provide a printed circuit board adjustment and inspection machine that can be constructed without requiring a major change in the basic configuration of a conventionally used board adjustment and inspection machine.

In order to achieve the above-mentioned object, the present invention provides a printed circuit board adjustment and inspection machine equipped with a contact pin for signal extraction, which extracts a detection output such as a voltage waveform at a measurement point from a circuit under test via a buffer amplifier. Based on a reference voltage that is sufficiently lower than the voltage at the measurement point of the circuit under test, which is supplied via a reference impedance that is lower in impedance than the input impedance of the buffer amplifier connected to the input side of the amplifier and higher in impedance than the impedance of the measurement circuit. A switching element performs a switching operation depending on whether the voltage of the contact pin is equal to or higher than a predetermined switching voltage lower than the signal voltage, and detects whether or not the contact pin is in contact with the circuit under test. An impedance detection circuit is connected to the contact pin, and the switching element obtains a signal for determining the contact state of the pin with respect to the circuit under test, and at the same time obtains a detection output of the measurement point.

In FIG. 2, P is a measurement point on the printed circuit board 1 to be inspected, and it is assumed that the potential at this point P varies from zero to 12V, for example. When the signal extraction contact pin 2 is brought into contact with this point P during measurement, the potential at the point P is sent to the buffer amplifier 3 through the contact pin 2. Further, a pin contact detection circuit 4 is connected to the contact pin 2.
This circuit 4 is configured as a circuit for detecting impedance changes, and receives a reference signal from a reference signal source provided via a resistor 5 whose value is sufficiently larger than the impedance of the measurement point P on the printed circuit board 1 to be inspected. Added as the base voltage of the transistor 7 via the diode 6 for transistor protection,
The detection signal outputted as the collector voltage of the transistor 7 is used to determine whether the contact state of the contact pin 2 is good or bad. That is, the diode 6, the transistor 7, and the resistor 8 constitute a voltage comparator 9, and a detection signal is obtained from its output terminal 10.

Therefore, when the contact pin 2 is in normal contact with the measurement point P, the potential of the contact pin 2 becomes equal to the potential of the measurement point P, and becomes a potential of zero V or more.
The base and emitter of transistor 7 are reverse biased, and no collector current flows. At this time,
The potential of the output terminal 10 becomes the reference voltage -V.

On the other hand, if the contact pin 2 is not in equal contact with the measurement point P, since the input impedance of the buffer amplifier 3 is selected to be sufficiently larger than the resistor 5,
Contact pin 2 is drawn through resistor 5 to reference voltage -V. Since the base potential of the transistor 7 is pulled through the diode 6 at the reference voltage -V, a positive bias is created between the base and emitter of the transistor 7, a collector current flows, and the output terminal 10
The potential of increases to near zero V.

As described above, the state of contact between the contact pin 2 and the measurement point P can be determined based on the potential of the output terminal 10.

Furthermore, FIG. 3 shows an example in which the device of the present invention is applied to an actual board adjustment/inspection machine. The measuring point is configured to touch and inspect the measuring point.

That is, 20 is a group of contact pins, 2A, 2
B and 2C are contact pins for contacting predetermined measurement points, respectively, and 2D, 2E, and 2F are ground connection terminals for preventing noise from entering from the printed circuit board side to be measured.

The pin contact detection circuits 4A, 4B, and 4C described in FIG. 2 are connected to the contact pins 2A, 2B, and 2C, respectively. And, each output terminal 10A of each detection circuit 4A, 4B, 4C,
10B and 10C are connected to corresponding interface circuits 11A, 11B and 11C, respectively. In addition, the interface circuits 11A, 11
B, 11C are the respective output terminals 10A, 10B,
10C to the first transistors 12A and 1, respectively.
2B and 12C, and the bases of second transistors 14A, 14B, and 14C are connected to the respective collector sides of these transistors 12A, 12B, and 12C via respective resistors 13A, 13B, and 13C. The middle points of the second transistors 14A, 14B, 14C and the resistors 15A, 15B, 15C connected to the collector side of the detection signals from the respective detection circuits 4A, 4B, 4C are at the operating level of the microcomputer MC, for example. Shift levels.

In the above configuration, the plurality of contact pins 2A, 2
b, 2C, for example, if the contact pin 2A is in poor contact with the printed circuit board to be measured, and the other contact pins 2B, 2C are in good condition, the potential of each of the contact pins 2B, 2C in contact is as follows. The potential is equal to the potential of the measurement point on the printed circuit board to be measured and is equal to or higher than zero V. Therefore, the collector current of the transistor 7 of each detection circuit 4B, 4C does not flow, and the potential of the output terminals 10B, 10C becomes the reference voltage -V. Become.

On the other hand, for the contact pin 2A in a contact failure state, a positive bias is applied between the base and emitter of the transistor 7 of the detection circuit 4A, and the collector current flows and the potential of the collector of the transistor 7 becomes zero V.
Rise nearby.

Therefore, each interface circuit 11B, 11 connected to each of the above-mentioned detection circuits 4B, 4C
C has a zero bias between the bases and emitters of the first transistors 12B and 12C, and a positive bias between the bases and emitters of the second transistors 14B and 14C.
A ground potential, that is, a logic "L" signal is supplied from the collectors of B and 14C to the microcomputer MC.

Further, the interface circuit 11A connected to the detection circuit 4A has a positive bias between the base and emitter due to the output of the detection circuit 4A at the base of the first transistor 12A. - A reverse bias is applied between the emitters and a logic "H" signal at a predetermined level is supplied from the collector to the microcomputer MC.

Therefore, the microcomputer MC can control the board adjustment/inspection machine according to the quality of the contact state of the plurality of contact pins 2A, 2B, and 2C.

As described above, in the present invention, it is possible to accurately determine the contact failure test of the contact pin for signal extraction, which has not been given any consideration in the conventional printed circuit board adjustment inspection machine, during the contact operation. .

By making such a defect determination possible and correctly grasping the situation in which a contact defect occurs, the intended purpose can be fully achieved, such as increasing the efficiency of adjustment and detection.

[Brief explanation of drawings]

FIG. 1 is a schematic side view illustrating the usage state of the board adjustment/inspection machine. FIG. 2 is a circuit diagram of a main part of the present invention, and FIG. 3 is a partial block diagram showing a specific example of the present invention. 1... Printed circuit board to be inspected, 2... Contact pin for signal extraction, 4... Pin contact detection circuit, 5... Resistor, 7... Transistor.

Claims (1)

[Claims] 1 In a printed circuit board adjustment/inspection machine equipped with a contact pin for signal extraction to extract detection outputs such as voltage waveforms at measurement points from the circuit under test via a buffer amplifier, the input of the buffer amplifier connected to the input side of the buffer amplifier. A predetermined switching voltage at which the voltage at the contact pin is lower than the signal voltage based on a reference voltage sufficiently lower than the voltage at the measurement point of the circuit under test, which is supplied via a reference impedance whose impedance is lower than the impedance and higher than the impedance of the measurement circuit. An impedance detection circuit that detects whether or not the contact pin is in contact with the circuit under test is connected to the contact pin using a switching element that performs a switching operation depending on whether or not the above-mentioned state exists. A printed circuit board adjusting machine characterized in that a switching element obtains a signal for determining the contact state of the pin with respect to the circuit under test, and at the same time obtains a detection output of a measurement point.