JPH0562701B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a printed circuit board inspection device, and more particularly to an improvement in one used for detecting defects in conductor lands on a printed circuit board.

<Prior Art> Generally, most of the defects that occur in printed circuit boards are due to disconnections in conductor lands formed on the board or short circuits between lands.

Therefore, a device for inspecting such defects is required.

However, such conventional testing equipment only tests the conductive state of the conductor land, and therefore cannot detect potential defects such as parts of the conductor land that are largely missing while maintaining continuity. In the end, inspection of the above-mentioned potential defective parts had no choice but to rely on visual inspection with the naked eye.

In order to solve these problems, a printed circuit board inspection apparatus as shown in FIG. 4 has been devised.

To explain this, printed circuit board inspection equipment is
It is composed of a constant current power supply 1, a pulse generator 2, a power transistor 3, a current detection shunt resistor 4, a comparator 5, a logic gate (AND circuit) 6, and the like.

Here, the constant current power supply 1 is connected via a power transistor 3 to one end of a conductive land 8 of a printed circuit board 7 to be inspected. Pulse generator 2
outputs two timing pulse signals P1 and P2, as shown in FIG. The power transistor 3 receives one pulse signal P from the pulse generator 2.
The conduction is controlled by 1. As a result, the constant current from the constant current power supply 5 is applied to the conductor land 8 for a predetermined period of time.
It is now possible to energize.

The other end of the conductor land 8 is connected to the current return path (ground side) of the constant current power supply 1 via the shunt resistor 4.

A voltage proportional to the current I ₀ flowing through the conductor land 8 is divided into the shunt resistor 4 . This divided voltage is applied to one comparison input terminal (-) of the comparator 5.

A predetermined reference voltage Vr is applied to the other comparison input terminal (+) of the comparator 5. A comparison output A of the comparator 5 is outputted via a logic gate 6. The gate operation of the logic gate 6 is controlled by the other pulse signal P2 from the pulse generator 2. Here, the other pulse signal P2 is emitted just before the one pulse signal P1 falls. Thereby, the comparison output A of the comparator 5 is extracted and outputted immediately before the end of the energization time by the constant current power source 1. Then, this extracted comparison output becomes the determination output B of the printed circuit board inspection device.

Note that the shunt resistor 4 and the comparator 5 constitute a current detection means, and the logic gate (AND circuit) 6 constitutes a gate circuit.

The operation of this configuration is such that, first, when the inspected conductor land 8 is normal, the judgment output B does not rise while the pulse signal P2 rises, as shown in FIG. 5A. L (low level)
Stay as you are.

However, as shown in FIG. 4, if there is a potential defective location X where the inspected conductor land 8 is partially missing and is prone to disconnection, by flowing the constant current _I0 , The conductive portion where the defective point X remains is fused. As a result, the defective location X exhibits an obvious conduction defect. Therefore, by extracting the comparison output A of the comparator 5 immediately before the end of the energization time from the constant current power source 1, the defective location can be electrically detected reliably.

FIG. 5B shows the operating state when the potentially defective location X occurs. That is, the current _I0 from the constant current power source 1 is cut off in the middle of the energization time, and as a result, the comparison output A of the comparator 5 changes from L (low level) to H (high level) near the end of the energization time. Changes to This change is extracted in synchronization with the pulse signal P2 and appears in the determination output B.

In the manner described above, the potential defective location X can be reliably detected electrically without visual inspection with the naked eye.

<Problems to be Solved by the Invention> However, in such a conventional printed circuit board inspection device, since the current from the constant current power source 1 and the energization time controlled by the pulse generator 2 are constant, the inspection The fusing conditions (current x time) corresponding to the conductor land 8 to which the Therefore, the detection ability was inferior and the reliability of the test was lacking. Furthermore, as a result of not achieving optimal fusing conditions, there was also the drawback that stress on the inspected product increased.

The present invention was devised in view of these conventional problems, and an object of the present invention is to improve the reliability of inspection by optimizing the fusing conditions for conductor lands.

<Means for Solving the Problems> For this reason, the present invention provides a printed circuit board inspection apparatus that can also inspect potential defective locations.
As shown in FIG. 1, there is a resistance/inductance measuring means for measuring the direct current resistance and inductance of a conductor land, and the current is predetermined by the resistance/inductance based on the measured value output from the measuring means. a condition setting means for setting a value and an energization time; a current setting means in a constant current power supply for energizing a predetermined constant current to a conductor land of a printed circuit board so as to meet the conditions; and a pulse for controlling an energization time by the constant current power supply. control means for controlling the generator;
has been established.

<Function> In the above configuration, the DC resistance and inductance of the conductor land to be inspected are measured in advance, and the condition of the conductor land's wire, thickness, length, etc., is checked.
Thereafter, a predetermined current and energization time are determined from this situation, and an inspection is performed using this current and energization time. Therefore, the inspection can be performed under optimal fusing conditions, and the reliability of the inspection can be improved.

<Example> Hereinafter, an example of the present invention will be described based on FIGS. 2 and 3.

In FIG. 2, the same elements as those in FIG. 4 are given the same reference numerals to simplify the explanation.

In FIG. 2, the printed circuit board inspection device consists of a constant current power supply 1, a pulse generator 2, a power transistor 3, a current detection shunt resistor 4, a comparator 5, and a logic gate (AND circuit) 6. , and the operations of these components are the same as those of the conventional device described above, so a description thereof will be omitted here.

A resistance/inductance measuring device 9 is provided as a resistance/inductance measuring means for measuring the direct current resistance (R) and inductance (L) of the conductor land 8. This resistance/inductance measuring instrument 9 is
Information such as the length and thickness of the conductor land 8 is read using the current vector. The control unit 10 includes a condition setting means for setting the current value and energization time predetermined by the resistance/inductance based on the measured value output from the resistance/inductance measuring device 9; A current setting means 11 in the constant current power supply 1 and a control means for controlling the pulse generator 2 are provided so that the constant current power supply 1 has a current setting means 11 and a control means for controlling the pulse generator 2.

Here, switches 12 and 13 are provided at both ends of the wiring connecting one end of the conductor land 8 of the printed circuit board 7 to be inspected and the power transistor 3, respectively. Switch 12 on the conductor land 8 side
is for switchingly connecting a plurality of connection terminals a, b, c connectable to one end of the conductor land 8,
The switch 13 on the side of the power transistor 3 switches and connects the connection terminal d of the power transistor 3 and one connection terminal e of the resistance/inductance measuring device 9. A plurality of connection terminals f, g, h connectable to the other end of the conductor land 8 are each connected to a current return path (ground side) of the constant current power supply 1 via a shunt resistor 4. A switch 14 is provided on the ground side wiring of the constant current power supply 1. This switch 14
is used to switch and connect the connection terminal i of the constant current power supply 1 and the other connection terminal j of the resistance/inductance measuring instrument 9.

Next, the operation of this configuration will be explained.

First, the switch 12 is used to switch one of the connection terminals a, b, and c that can be connected to one end of the conductor land 8 to be inspected.
3 is switched to one connection terminal e of the resistance/inductance measuring instrument 9 as shown, and the switch 14 is switched to the other connecting terminal j of the resistance/inductance measuring instrument 9.

Then, the fusing condition for the conductor land is set by the action shown in the flowchart of FIG.

That is, in S1, the resistance/inductance of the conductor land 8 to be tested is measured by the resistance/inductance measuring device 9. and,
In S2, based on the resistance/inductance signal measured in S1, the corresponding current/energization time is read from the map of current/energization time determined by the relationship with resistance/inductance, and in S3, this current/energization time is set. . In S4, the current setting means 11 in the constant current power supply 1 and the pulse generator 2 are controlled so that the set value is achieved.

After that, switch 13 is connected to power transistor 3.
At the same time, switch 14 is switched to connection terminal d.
is switched to the connection terminal i of the constant current power supply 1, and the constant current from the constant current power supply 1 is applied to the conductor land 8 for a predetermined period of time.
The test operation is performed in the same manner as in the past.

Then, switch 12 to select the conductor land 8 to be inspected, and perform the above operation on the conductor land 8.
Do this every time.

According to this configuration, the direct current resistance and inductance of the conductor land 8 to be inspected are measured in advance to check the conditions such as the thickness and length of the wire of the conductor land 8, and then a predetermined current and energization are determined from this condition. Since the test is performed using this current and current-carrying time, the fusing conditions (current x time) for the conductor land 8 to be inspected can always be set to the optimum value, and for thin wire conductors. However, it is also the optimum fusing condition for thick conductors.

Therefore, the detection ability can be improved, the reliability of the inspection can be improved, and the disadvantage of increased stress on the product to be inspected can also be eliminated.

<Effects of the Invention> As explained above, according to the present invention, in a printed circuit board inspection apparatus that can also inspect potential defective parts, the DC resistance and inductance of the conductor land to be inspected are measured in advance and the conductor land is inspected. We investigated the conditions such as the thickness and length of the land wires, then learned the predetermined current and energization time from this situation, and performed the inspection using this current and energization time. The inspection can be performed under suitable fusing conditions, the detection ability can be improved, the reliability of the inspection can be improved, and the drawback of increased stress on the product to be inspected can be eliminated.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a printed circuit board inspection device according to the present invention, Fig. 2 is a circuit diagram showing an embodiment of the same device, and Fig. 3 is a flowchart explaining the operation related to setting of fusing conditions in the same device. , Figure 4 is a circuit diagram of a conventional example of a printed circuit board inspection device, and Figure 5 is a circuit diagram of a conventional example of a printed circuit board inspection device.
Figures A and B are timing charts showing an example of the operation of the above device, respectively. 1...constant current power supply, 2...pulse generator, 3...
... Power transistor, 4 ... Current detection shunt resistor, 5 ... Comparator, 6 ... Logic gate (AND circuit), 7 ... Printed circuit board, 8 ... Conductor land,
9...Resistance/inductance setting device, 10...Control unit, 11...Current setting means 1
1.

Claims (1)

[Claims] 1. A constant current power supply that supplies a predetermined constant current to the conductor lands of the printed circuit board, a pulse generator that controls the energization time by the constant current power supply, a current detection means that detects the current flowing through the conductor lands, and a current detection means that detects the current flowing through the conductor lands. A printed circuit board inspection apparatus comprising: a gate circuit for extracting the detection output of the detection means immediately before the end of the energization time by the constant current power source;
an inductance measuring means; a condition setting means for setting the current value and energization time predetermined by the resistance/inductance based on the measured value output from the measuring means; A printed circuit board inspection device comprising: current setting means in a power source and control means for controlling a pulse generator.