JPS59214780A - Detection of short-circuited point for printed circuit board - Google Patents

Abstract

PURPOSE:To detect short-circuited points in a multilayer printed circuit board efficiently and accurately by connecting one end of a lead connected to a buzzer checker to a power source section and/or a ground section and a conduction element to the other end thereof while a circuit is swept with the conducting element through a sheet. CONSTITUTION:A power source layer Vcc and a ground layer GND on a printed circuit board are connected to a battery 6 and a buzzer 5 with a leads 7 and 8 and a conducting element 4 is connected thereto. When a scanning is done over a conductor from a signal terminal 3 through an insulation sheet, the conductor is connected to an adjacent conductor through a short-circuited point 10 and then, to the power source layer Vcc or a copper plating of the ground GND through a power source terminal 1 or a ground terminal 2 to form a current loop through a capacitance C. This also enables the formation of a loop even in case of a short-circuiting in the inner layer of a multilayer printed circuit board. The conducting element 4 uses a conducting brush and when a buzzer sounds, the movement of the conducting element 4 is halted to check for short- circuited points 10.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for detecting short circuits on a printed wiring board.
In particular, it relates to a method for detecting printed wiring boards with special shapes that cannot be inspected by automatic inspection machines, or short circuits between lands that are not on a standard grid.

[Prior art]

Conventionally, inspection of printed wiring boards has been emphasized in order to improve their reliability. Recently, automatic inspection machines that individually detect conductive units on printed wiring have been proposed and put into practical use. For automatic inspection of printed wiring boards, a method is generally used in which a glove is brought into contact with each terminal on the network, and current is sequentially applied between specific probes to check the connection state. In that case, in order to ensure that hundreds to thousands of probes make contact with the terminals of the printed wiring board, extensible gloves with springs are used, and these gloves are placed at each terminal position on the printed wiring board to be inspected. It is implanted on a board according to the requirements, and connected to the main body of an automatic inspection machine using a connector to form a glove adapter.The adapter is then brought into close contact with the printed board to be inspected manually, using a vacuum or pneumatic press, and inspection is performed. This adapter needs to be manufactured individually for each pattern on the printed board, but as the number of gloves increases, the cost of the probe and the number of wiring steps increase, making it extremely expensive. Therefore, in order to automatically inspect large printed boards or printed boards of a wide variety and small quantity, it is absolutely necessary to share the adapter. Therefore, we make an adapter that places gloves on all grid points in the inspection area in accordance with the most common grid size of 2.54 m, and during actual inspection, only the gloves necessary for that drawing number are used. , a method is used to prevent unnecessary probes from operating. In order to prevent unnecessary probes from operating, there are two methods: a physical method of using a mask film with holes drilled only at necessary locations, and an electrical method of skipping unnecessary probes during probe scanning. In this way, automatic inspection machines
2.54 For a printed wiring board with multiple lands on a standard grid, probes are brought into contact with each terminal other than the mask, and current is sequentially applied between specific probes to check the connection status using a computer as a standard. By checking while comparing, abnormalities such as short circuits and disconnections can be detected in a short time. However, there is a drawback that the above-mentioned automatic inspection machine cannot inspect between lands that are not on the standard grid. In other words, recently, the diversification of IC packages has progressed, and 1.27
The number of non-standard lattice parts such as 1.905 and 1.905 is increasing. Moreover, printed wiring boards of special shapes such as circular shapes cannot be inspected by the above-mentioned automatic inspection machine. For this reason, printed wiring boards for which automatic inspection machines cannot be used must rely on visual inspection, but visual inspection is inefficient and has low reliability.

Furthermore, recently, multilayer printed wiring boards having a ground layer and a power supply layer have come into widespread use, but there are limits to visual inspection of multilayer printed wiring boards. for example,
The 4-layer printed wiring board, as shown in Figures 1 and 2,
The second and third layers are used as a power layer and a ground layer, respectively. Among the through holes that penetrate from the first layer to the fourth layer, the power hole l is connected to the power layer with copper plating, and the ground hole 2 is connected to the ground layer. The signal hole 3 is not connected to these power supply layer and ground layer, but penetrates from the first layer to the fourth layer, and forms a land on the first layer or the fourth layer. Furthermore, a signal layer can be inserted between the power supply layer and the ground layer to increase the number of layers to five or more. Even if an attempt is made to detect a short circuit in a multilayer printed wiring board by visual inspection, it is impossible to detect a short circuit in an inner layer other than the outer layer.

[Purpose of the invention]

The object of the present invention is to eliminate such conventional drawbacks and to provide a short-circuit point that can electrically efficiently and reliably detect short-circuit points in printed wiring boards that cannot be inspected with automatic inspection machines or in multilayer printed wiring boards that cannot be inspected even with visual inspection. The objective is to provide a power method.

[Summary of the invention]

In order to achieve the above object, one end of the lead wire connected to the buzzer checker is connected to the power supply section and/or the ground section on the circuit to be inspected, based on the short circuit detection method of the printed wiring board according to the present invention. Connect a conductor to the other end, cover the above circuit with an insulating sheet with a through hole provided only at the land portion, and sweep the conductor over the insulating sheet to detect the short circuit by sounding a buzzer. There is a characteristic in doing.

[Embodiments of the invention]

FIG. 3 is a diagram showing the principle of the method for detecting nine short points on a printed wiring board according to the present invention.

In the present invention, a power supply section (that is, a power layer) and/or a ground section (that is, a ground layer) of a printed wiring board
Connect one end of the lead wire to the printed wiring board, cover the printed wiring board with an insulating sheet that has through holes only in the land area, and clean the insulating sheet with a conductor such as a copper brush to create a short circuit. The cylinder 79i is detected by a buzzer. If this is written as a circuit, as shown in Figure 3, the power layer (Vcc) of the printed wiring board, 7)"M(GND) wo!J-)
Connect the wire 7.8 to the battery 6 and the buzzer 5 through the IC, and connect the conductor 4 to the tip.If you scan the land ?t1≦, that is, the conductor from the signal terminal 3 through the insulating sheet, there will be no short circuit. When the circuit is normal, no current loop is formed, so the buzzer 5 does not sound.However, when there is a short-circuit point 10, it is connected to the adjacent conductor through this short-circuit point IO, and the power supply 1°M terminal 1 or the ground terminal 2 is via the power supply layer (Vcc) or ground (GNI)
)), a current loop including the buzzer 5 and the battery O is formed.

Since a current loop is formed via the capacitance C, a loop can be formed even if a short circuit occurs in the inner surface layer of a multilayer printed wiring board, and the short circuit location can be detected.

Short circuits are often connected to adjacent conductive wires through "whiskers" caused by defects in the copper pattern, but by scanning the conductor 4 according to the present invention, short circuit locations can be efficiently detected.

Fig. wJ4 is an implementation layout diagram of a method for detecting a short circuit according to an embodiment of the present invention, and Fig. 5 is a back view of the conductor shown in Fig. 4.

Connect one end of the lead wires 7 and 8 to the power layer and ground layer of the printed wiring board, respectively, and connect the buzzer/checker 5 and the battery 6.
A conductor 4 is connected to the other end via. The insulating sheet 9 coated on the printed wiring board has a thickness of, for example, 0. :L
A polyester film with a diameter of mm is used, and only the land portion, that is, the signal terminal ①@O is provided with a through hole. As the conduction calf, a conduction brush as shown in FIG. 5 is used, which includes a copper brush +1 in which copper pins are densely implanted, a grip part 42 for fixing this copper brush 41, and a copper brush 41.
It is composed of a socket portion 43 that connects the handle nL. Note that a pen-shaped calf can also be used as the conductive calf. By scanning from above the film 9 with this conductor 4, if there is a short circuit point 10, a current will flow and a buzzer will sound, so when this buzzer sounds, the movement of the conductive calf is stopped and the short circuit point 10 is Check.

The present invention is particularly effective when detecting short-circuit locations on a printed wiring board that cannot be inspected with an automatic inspection machine, such as a circular printed wiring board, or when detecting short-circuit locations on a multilayer printed wiring board.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to electrically efficiently and accurately detect short-circuit locations on a printed wiring board. This method is effective in detecting short circuits in multilayer printed wiring boards that cannot be inspected with an automatic inspection machine or visually inspected.

[Brief explanation of drawings]

Fig. 1 is an exploded explanatory diagram of a multilayer printed wiring board, Fig. 2 is a cross-sectional structural diagram of the multilayer printed wiring board, Fig. 8 is a principle diagram of the printed wiring board short circuit detection method of the present invention, and Fig. 4 is a diagram of the present invention. Fig. 5 is a structural diagram of the conductor shown in Fig. 4; 1: Power supply terminal (hole), 2 Nigelland terminal (hole), 3 = Signal terminal (hole), 4: Conductor, 5: Buzzer/checker, 6
: Battery, 7, 8: Lead wire, 9: Insulating film, lO:
Short circuit point, PWB niblint wiring board. Proxy Masutoshi Masatoshi Isomura/Figure 1

Claims (1)

[Claims] In a method for detecting short circuits on printed wiring boards, one end of a lead wire connected to a buzzer checker is connected to the power source and/or ground section of the circuit to be inspected, and a conductor is connected to the other end. The circuit is characterized in that an insulating sheet having a through hole is provided only on the land portion, and the conductor is rubbed over the insulating sheet to detect a short-circuit point by sounding a buzzer. Method for detecting short circuits on printed wiring boards.