JPS6239708B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inspection device for circuit boards such as printed circuit boards.

Inspection methods for circuit boards such as printed circuit boards include an operation check method in which the operation of the circuit is confirmed by operating the circuit, and a DC check method in which the voltage at each measurement point is measured. Although the former method can be tested at low cost, it has the disadvantage of poor reliability because even if a circuit constant is abnormal when a different circuit element is inserted and connected to a board, it may not be recognized as an abnormality in circuit operation. In the latter DC check method, it is necessary to determine a standard voltage value for each check point, store it in a memory device, and then compare this stored data with measured data, which has the disadvantage of increasing the price of the device. There is. Furthermore, in order to convert measurement data into digital values, an A/D converter that operates at low speed is required, resulting in an increase in measurement time. Furthermore, an increase in the number of measurement points is unavoidable, which leads to a decrease in reliability due to poor contact of the contacts.

An object of the present invention is to provide a circuit board inspection device with an extremely simple configuration and high reliability.

The inspection apparatus of the present invention prepares a reference circuit board having a circuit board to be tested and a circuit network that is to be a standard for this board, and selects arbitrary corresponding first and second circuit boards on each circuit network of both circuit boards. Select the second check point, connect the first check point on the circuit board under test and the second check point on the reference circuit board, and connect the second check point on the circuit board under test to the first check point on the reference circuit board. A constant voltage V is applied between the first and second check points, and the quality of the circuit between the first and second check points of the circuit board to be inspected is determined based on the voltage state of the connection point of the above-mentioned check points.
This is a device that tests the quality of a circuit board by sequentially switching the selection of check points, and the detection means for detecting the voltage state of a connection point is such that the voltage at the connection point is V/2 (1 ± δ ) (where δ is constant) and outputs a good signal.

It is characterized by using a variable resistor or a plurality of resistors with different values in order to variably set the value of ±δ indicating this error range as desired.

The present invention will be explained below using the drawings.

FIG. 1 is a schematic diagram of the circuit network of the circuit board to be inspected, where Z ₀ to _{Z 11} indicate basic circuits or elements,
TP ₁ to TP ₅ are check terminals indicating check points. FIG. 2 is a schematic diagram of the circuit network of a reference circuit board that has a circuit network that should be the standard for this circuit board to be tested, that is, a good sample circuit board that has a normal circuit network _{. -Z11} ' indicate basic circuits or circuit elements, and _TP0 ' to _TP5 ' are check terminals indicating check points. In both figures, each check terminal TP ₀ ~ TP ₁₁ and TP ₀ ′ ~
It is assumed that TP ₁₁ ' are provided at corresponding and equal locations on the circuit network.

After preparing such two circuit boards, consider the operation of the connected state shown in FIG. 3, for example. That is, when determining the quality of the circuit between the first and second check terminals TP ₀ and TP ₁ of the circuit board to be inspected shown in FIG. 1, for example, a constant positive voltage +V is applied to the check terminal TP ₀ . The other check terminal TP ₁ is directly connected to the corresponding first check terminal TP ₀ ' of the reference circuit board, and the other corresponding second check terminal TP ₁ ' of the reference circuit board is grounded. At this time, assuming that no power supply voltage is applied to the circuit networks of both circuit boards, the first and second check terminals TP ₀ and TP ₁ of the circuit board to be tested are
and the DC impedance component X ₁ between the first and second check terminals TP ₀ ' of the reference circuit board and
If _the DC impedance component X ₁ ′ between terminals TP _{1 ′} and
It is clear that V ₀ is V/2. In other words, short circuits due to _solder bridges, open circuits due to pattern _breakage , erroneous resistance, and
If there is a defect such as a missing item or reverse insertion of a semiconductor element, the potential V ₀ of the connection point will deviate from V/2, and as a result, by knowing the potential state of this connection point, the circuit between both terminals can be corrected. It can be seen that it is possible to determine the quality of the product. Here, since there is naturally a certain range of variation between circuit elements, the potential V ₀ at the connection point fluctuates within a range of V/2 (1 ± δ). If the value is above, it may be determined that the circuit between both terminals is good. Note that δ is a value indicating a certain error range and is determined by the circuit network or the like.

A general example of the principle shown in Figure 3 is shown in Figure 4.
1 is a schematic equivalent circuit diagram illustrating an embodiment of the present invention. FIG. A selection switch S1 is provided to selectively apply a constant voltage +V to one check terminal of the circuit board to be inspected, and a selection switch _S1 is provided to selectively apply _a constant voltage ₊ V to one check terminal of the circuit board under test. A selection switch _S2 is provided for selecting the check terminal _TP3 . and a check terminal corresponding to check terminal TP ₂ selected by switch S ₁ on the circuit board to be tested of the reference circuit board.
A switch _S3 is provided which selects TP2' and connects it to the check terminal _TP3 of the circuit board to be inspected selected by the previous switch _S2 , and also connects the check terminal _TP3 selected by the switch _{S2 .} A switch _S4 is provided for selecting and grounding the check terminal _TP3 ' of the reference circuit board corresponding to the reference circuit board.

In order to detect the potential V ₀ at the common connection point of switches S ₂ and S ₃ , first and second comparators 1 and 2 are connected.
is provided, and this potential V ₀ serves as one input. As the other inputs, the divided voltage outputs V ₁ and V ₂ of the voltage dividing circuit 3 that divides the reference voltage source +V are used, respectively. For example, as shown in the figure, this voltage divider circuit 3 is made up of a series connection circuit of resistors R ₁ and R ₂ and a variable resistor VR, and by setting the value of the variable resistor VR arbitrarily, the above-mentioned variations in circuit elements can be eliminated. It is possible to define an error range ±δ due to . By doing this, when a voltage _V0 exceeding +V/2 (1±δ) is input to comparators 1 and 2, the output OUT-1 or OUT-2 of either comparator 1 or 2 changes accordingly. Abnormalities can be determined by The comparators 1 and 2 constitute a so-called window comparator circuit.

It is clear that the circuits between any two check terminals of the circuit board to be tested can be inspected by appropriately controlling each of the switches _S1 to _S4 .

Incidentally, a constant positive (or negative) voltage may be applied to one of the check terminals on the reference circuit board side, and in short, a set of corresponding check terminals on both circuit boards is applied to the opposite check terminals. Of course, a constant voltage may be applied between TP ₃ and TP ₂ ' in FIG. 4, for example.

The switches S ₁ to _{S 4} can be controlled according to a program determined by a control device such as a microcomputer, and the output
If the discrimination between OUT-1 and OUT-2 is also processed and determined by a processor such as a microcomputer, it can be an extremely high-speed inspection device.

In the example shown in Fig. 4, a variable resistor VR is used to set the error range ±δ, but with this method, once the variation in circuit elements is set to a certain constant value δ, it is difficult to change it afterwards. . However, in reality, the impedance among the many check points on the circuit board is not uniform, as there are many places where there are large variations even if the board is of good quality. Therefore, the error ±δ
must be set to the maximum value, and as a result, the ability to detect defective locations is reduced.

An example in which this drawback has been solved is shown in FIG. 5, in which parts equivalent to those in FIG. 4 are designated by the same reference numerals. In the figure, as a circuit to determine the error range ±δ, multiple resistors with different values are used instead of a variable resistor.
Set R ₁₀ to R _1o and switch one of these resistors.
The reference voltages V ₁ and V ₂ are obtained by selecting S ₅ and S ₆ . Therefore, assuming that both resistors R ₁ and R ₂ are equally R, one resistor R _1i (i=0 to
When n) is selected, the value δi of the error range becomes the following equation.

δi=R _1i /2R+R _1i (1) For example, R=1KΩ, _R10 =100Ω, _R11 =220Ω,
If R ₁₂ = 470Ω, R ₁₃ = 2KΩ, and R ₁₄ = 12KΩ, δi is δ ₀ = 4.8%, δ ₁ = 9.9%, δ ₂ =
19%, δ ₃ =50%, and δ ₄ =86%. Therefore, if the switches S ₅ and S ₆ are switched and controlled in synchronization with each other, the error range can be selected as desired.

As described above, the present invention has the advantage of enabling a high-speed and highly reliable inspection method with an extremely simple configuration.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the circuit network of the circuit board to be tested, Fig. 2 is a schematic diagram of the circuit network of the reference circuit board that is to be the standard for the circuit board to be tested in Fig. 1, and Fig. 3 is a schematic diagram of the circuit network of the circuit board to be tested. FIG. 4 is a schematic diagram for explaining an embodiment of the present invention, and FIG.
The figure is a schematic diagram for explaining another embodiment of the present invention. Explanation of the symbols of the main parts, TP ₀ ~ TP _o ... Tested circuit board check terminal, TP ₀ ′ ~ TP _o ′ ... Reference circuit board check terminal, VR ... Variable resistor for setting error range, R ₁₀ ... _R1o ...Resistance for error range setting,
S ₁ ~ _{S 6} ... switch.

Claims (1)

[Scope of Claims] 1. Corresponding to any corresponding first check point of each circuit network of a circuit board to be inspected and a reference circuit board having a circuit network to be a standard for this circuit board to be inspected. means for connecting the first check point of the circuit board to be inspected and the second check point of the reference circuit board at a common connection point; means for applying a constant voltage V between the second check point and the first check point of the reference circuit board; a voltage detecting means for outputting a pass/fail signal of the circuit, the circuit board testing device is configured to test the pass/fail of the circuit board by sequentially switching selections of the first and second check points, the circuit board testing device comprising: The detection means detects that the voltage at the common connection point is (V/2)
×(1±δ) (δ is a value according to the permissible range of impedance between the first and second check points of the circuit board to be inspected) and outputs a good signal. A circuit board inspection device characterized by having a circuit. 2. The voltage detection means includes a reference voltage generation means that generates a reference voltage of (V/2)×(1±δ), and a comparator that compares the reference voltage with the voltage at the common connection point. An apparatus according to claim 1. 3 The reference voltage generation circuit is configured to generate ±δ of the reference voltage.
3. The device according to claim 2, further comprising a variable resistor that changes the value of the resistor. 4. A patent characterized in that the reference voltage generation circuit has a plurality of resistors having different values, and a resistance selection circuit that selects one of the resistors to select a desired value of ±δ of the reference voltage. Claim 2
Apparatus described in section.