JPS61117473A - Method and device for inspecting printed wiring board - Google Patents

Abstract

PURPOSE:To speed up inspection by inspecting the breaking of wiring between a reference pin and other pins in networks of a printed wiring board for every network, and performing the batch short-circuit inspection of other pins outside the networks. CONSTITUTION:When the reference pin is formed at a land part 1 of the printed wiring board and a network is formed by pins 1, 2, and 5, an output is sent to the pin 2 through a decoding circuit A as to the reference pin 1 to inspect the breaking of wiring between the pins 1 and 2, and inspection as to the pins 1 and 5 is also performed similarly to complete the inspection of the breaking of wiring in the network. Then, an all-active signal is sent from a signal line D to perform the batch short-circuit inspection of all pins 3, 4... outside the network for the reference pin 1. At this time, the latch integrated circuit C of the pins 2 and 5 is set during the inspection of the breaking of wiring and the Q output is at H, so the condition of AND with the all-active signal is not satisfied and the pins 2 and 5 within the network are cut. Thus, the short- circuit inspection is performed for pins outside the network at a time, so the inspection of the printed wiring board is speeded up.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printed wiring board inspection method and an inspection apparatus thereof, and more specifically, the present invention relates to a method for inspecting a printed wiring board and an inspection apparatus therefor. A quick and easy test for disconnection between a specific reference pin (hereinafter referred to as the reference pin) and other pins in the network, as well as a batch short-circuit test between the reference pin and all other pins that do not belong to the network. The present invention relates to a method for inspecting a printed wiring board and an inspection apparatus therefor, characterized in that the inspection is carried out sequentially on all networks with high efficiency, and when the inspection is not being carried out, all of the pins are grounded to prevent static electricity from being charged.

[Conventional technology]

In general, the inspection method for printed wiring boards involves bringing probe pins (hereinafter simply referred to as pins) into contact with lands that are part of the pattern of the printed wiring board, which is the object to be inspected, and testing whether there is continuity between each land. However, by comparing the reference data of the pattern of a good printed wiring board stored in advance in the central control unit (IC memory) with the data of each pattern to be inspected, it is possible to detect disconnections or short circuits in the pattern. It is used to discover defective circuit parts.

For this reason, conventionally, in order to test whether the pattern between a reference pin and which pin has continuity, a so-called scan-type all-pin test was performed, in which continuity tests were performed on all pins other than the reference pin. I was worried.

However, in such all-pin inspection, if the number of pins that contact the land of the pattern of the printed wiring board that is the object to be inspected is, for example, 0 (usually n is a large number of pins in the thousands), then n (n-1)X Since the scanner (all pin inspection operation) must be repeated 1/2 times, a high-speed scanning operation is naturally required, and the rσ energy stored in the printed wiring board, which is the object to be inspected, is Volume remains.

Therefore, in such an inspection method that requires a large number of inspection operations, pins between patterns that are not originally short-circuited show a short-circuited state due to accumulation of electricity, which causes incorrect inspection of the printed wiring board. Further, there are drawbacks such as mismatching of characteristic impedances due to high-speed scanning, emissions due to standing waves, and static electricity generated during inspection work, which may cause malfunction or damage to the IC.

[Problem that the invention seeks to solve]

Therefore, in order to eliminate the drawbacks of the conventional inspection methods described above, the inventor of the present invention proposed that in a printed wiring board, lands that contact pins such as through holes and pads are connected by conductive patterns to form several networks. Focusing on
When inspecting printed wiring boards, standard data of good printed wiring boards is downloaded to the central control unit in advance.
A reference pin and a number group of pins belonging to this network are stored for each network, and at the time of inspection, the reference pin and other pin number groups are sequentially read out for each network from the IC memory of the central control unit to inspect for disconnections in the network.
Perform a batch short-circuit test with all other pins that do not belong to the network, and after the test is finished, ground all of the pins between the set of the tested board and the offset until the next test starts. As a result, we devised a method for removing static electricity that accumulates on the substrate to be inspected and the jig mounting plate, and a device used in this method.

In other words, it is possible to perform a batch short-circuit test that eliminates the above-mentioned shortcomings and inconveniences associated with the high-speed scanning method of conventional test methods, and on the other hand, short-circuit tests can be performed slowly for each network to eliminate the influence of accumulation of electricity on the printed wiring board, and the overall short circuit test can be performed slowly. It is an object of the present invention to provide a printed wiring board testing method and testing device that can shorten the testing time and perform highly reliable continuity testing.

[Means for Solving the Problems and Their Effects] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a schematic circuit diagram of the main parts of a circuit used in the printed wiring board inspection apparatus of the present invention, and FIG. 2 is a functional explanatory diagram showing the open and closed states of switches in the circuit of FIG.

First, in FIG. 1, 1, 2, 3, 4, and 5 indicate the positions of the reference pins, respectively, and correspond to the head pin numbers of the group pins of each network. (5) is a decoding circuit, which is composed of a plurality of output signals that become "H" only when the input becomes a specific value. (B) is a reset signal line, and if you send a signal, the latch IC will be reset. (C) is a latch IC, which is a set/reset IC.

(D) is a signal line that brings out the active function,
D gate (E), OR gate (F), inverter (G
) etc., an all-active function is formed.

Further, (0) is a detection point, and (T) is a shift register.

Next, in FIG. 2, 1, 2, 3, 4, and 5 indicate the positions of the reference pins, respectively. (W) and (U) are transistors.
(FFJT) and also has the function of a switch.

FIG. 3 is a partially enlarged plan view of the pattern of the printed wiring board. In this drawing, (P) is the substrate surface of the printed wiring board, 1.2.3.4.5.6.7 indicates each through hole and its land portion, (a), (b),
(C) and (B) indicate conduction lines between each through hole.

The printed wiring board inspection apparatus of the present invention having the circuit shown in FIG. , is characterized by having at least an all-active function for all pins and a launch function for cutting all other pins belonging to the network other than the reference pin.

- Therefore, it has the function of opening and closing the switch as shown in Fig. 2. That is, when the switch Wl is closed and the switch U2 is closed, it can be tested that the pattern from pin number 1 to pin number 2 is conductive. On the other hand, when Wl and US are closed, it means that it is possible to test whether the pattern from pin number 1 to pin number 5 is electrically connected.

Next, the printed wiring board inspection method of the present invention will be explained based on the plan view of FIG.

In this drawing, the land portion 1.3.4 indicates the first reference pin, the third reference pin, and the fourth reference pin, and for each of these reference pins, 1-2-5.3-7.4 −6 networks are formed. Then, the data is written and stored in the IC memory of the central control unit as data, as shown in the data schematic diagram of FIG. 4, for example.

In this case, the printed wiring board inspection procedure is to first output pin 2 of the first reference pin through the decoding circuit, conduct a connection test between pins 1 and 2, and do the same with pins 1 and 5.
The pins will also be inspected. In this way, a disconnection test within the first net can be performed.

Next, an all-active signal is sent from the signal line (D), and a short-circuit test is performed on all other pins belonging to the first net other than the first reference pin at once. At this time, the 4 other latch ICs on pins 2 and 5 are set during the disconnection test, and the Q output is "H", so AND cannot be taken with the all-active signal, and the signal in the network of the first reference pin is Pins are cut.

Therefore, according to the present invention, the simultaneous short-circuit test to see if all other pins belonging to the first net are short-circuited can be completed in an instant by simply issuing an all-active signal. There are advantages that can be achieved. This allows inspection of printed wiring boards to be completed within an extremely short time, approximately 1/10 to 1/100 of the time required for scanning all pin inspections in conventional inspection methods, so each network short-circuit inspection can be performed slowly at regular intervals, and as a result, it is possible to eliminate any residual electrical charge in the printed wiring board, and also eliminate the mismatch of characteristic impedance and emission caused by standing waves caused by conventional high-speed scanning methods. There is an advantage that it can be eliminated.

Furthermore, in Figure 1, after scanning all pins, all the outputs of the shift register (T) are set to negative, and (B)
All R/s latches IC (C) are reset using the signal line. Then, using the signal line (D), all the pins are set to the active state, and all the test probe pins are grounded. This can prevent malfunctions and damage to the IC due to static electricity entering from the test probe pins. Furthermore, the time required for inspecting printed wiring boards can ultimately be shortened to one-tenth of that of conventional methods, and printed wiring boards can be inspected quickly, easily, and with high reliability.

〔Effect of the invention〕

As described above, according to the present invention, for each network of a printed wiring board, the reference pin is inspected for disconnection with other pins in the network, and all other pins belonging to other than the net are simultaneously inspected. Be able to quickly and easily perform short circuit inspections.

Note that the second and third nets also perform the same internal wire breakage inspection for the first reference pin as described above for the third and fourth reference pins, as well as for all other pins that belong to other than the net. Since short-circuit inspections can be performed alternately, printed wiring boards can be inspected quickly, easily, and with high reliability as a whole.

[Brief explanation of drawings]

t1g1 is a schematic circuit diagram of the main parts of the circuit used in the printed wiring board inspection device of the present invention, FIG. The enlarged plan view of FIG. 4 is an example of a schematic diagram of data stored in the IC memory of the central control unit. In the above drawing. A...--Decoding circuit (decoder) B-
...... Reset signal line, C... Latch IC1 D... Active function signal line. E......AND gate, F...-..., OR gate, G...Inverter, O...-detection point, P...・・・・・・Board surface of printed wiring board, T・
・-・・Shift register, Q・・・Q gate, U・・・・・・Transistor circuit, W,, −,・・
-Transistor circuit.

Claims (1)

[Claims] 1. Divide the pattern on the printed wiring board, which is the object to be inspected, into network units, store the reference pins for each network and the number group of pins belonging to the network in a central control device, and control the central control at the time of inspection. The device reads the reference pin and the number group of pins belonging to the network for each specific network, and performs pattern inspection within the network and batch short-circuit inspection of all other pins that do not belong to the network with respect to the reference pin, sequentially for all networks. A method for inspecting a printed wiring board, characterized in that all of the pins are grounded when the inspection is not being carried out. 2. A decoding function that divides the pattern on the printed wiring board, which is the object to be inspected, into network units and specifies the reference pin and number group of pins belonging to the network for each network, an all-active function for all pins, and a reference pin Inspection of a printed wiring board that has at least a latch function that can cut all other pins in the network other than the above, and a mechanism that allows circuits with these functions to be communicated and controlled by a central control unit. Device.