JP4249666B2 - Printed wiring board - Google Patents

Description

  The present invention relates to a printed wiring board that detects a malfunction of an electronic circuit on a printed circuit board caused by an environmental defect.

  Many electric and electronic circuits of various devices use a printed wiring board in which a circuit pattern made of a conductive material is provided on a substrate made of an insulating material. In an environment where such an apparatus using a printed wiring board is used, the printed wiring board may be contaminated with dust, cutting oil, or the like, resulting in malfunction. For example, as shown in FIG. 8, foreign matter 11 such as cutting oil or chips adheres between two legs 10a of an integrated circuit (hereinafter referred to as IC) chip 10 mounted on a printed wiring board, and the foreign matter 11 becomes conductive. If there is, the insulation resistance between both feet 10a is reduced, and an electrical failure occurs. In addition, when the adhered foreign matter is corrosive, the conductive pattern on the printed wiring board is disconnected, causing a malfunction.

  As a method for detecting such deterioration of a printed wiring board, a printed board having a deterioration detection pattern, an A / D converter, a determination circuit, a display circuit, etc. is connected to a printed board unit subject to preventive maintenance with a connector. The voltage is applied to both ends of the degradation detection pattern, the detection voltage is converted to a digital value by the A / D converter, and the detection data converted to the digital value is analyzed by the determination circuit to determine the deterioration. An invention in which display is performed by a display circuit is known (see Patent Document 1).

Japanese Patent Laid-Open No. 10-62476

The printed wiring board deterioration detection method according to the invention described in Patent Document 1 described above requires a deterioration detection pattern, an A / D converter, a determination circuit for determining a detection level, and a display circuit. Necessary and cost increases.
Therefore, an object of the present invention is to provide a printed wiring board capable of detecting deterioration and malfunction of the printed wiring board at low cost.

The invention according to claim 1 is a printed wiring board in which a circuit made of a conductive material is provided on a substrate made of an insulating material, and a plurality of input terminals connected to a wiring connection portion provided on the printed wiring board. An integrated circuit composed of a logic circuit, a differential receiver circuit, or an output enable circuit is disposed in a place that is most easily contaminated on a printed wiring board, and the integrated circuit detects an insulation failure between the input terminals. It is what you do . According to a second aspect of the present invention, the integrated circuit detects a change in output level from a normal output level to detect insulation between adjacent input terminals .

  The malfunction due to the deterioration of the printed wiring board and the disconnection of the conductive pattern can be detected using a general-purpose logic integrated circuit or the like, so that it can be configured at low cost.

  The present invention uses a general-purpose logic IC as a printed circuit board deterioration and malfunction detection IC. This detection circuit IC is contaminated with a printed circuit board near the air inlet in the printed circuit board. Implement in a place where there is a high possibility of As a result, the detection circuit ICs are placed under the conditions of the same position as the printed wiring board that is actually used and in the most easily contaminated location, so that the printed wiring board is more reliably deteriorated and malfunctions. It can be detected.

The detection circuit IC used in the present invention uses a general-purpose logic IC, and uses a logic IC such as AND, NAND, OR, NOR, EXOR, and EXNOR.
FIG. 1 shows a first embodiment in which the detection circuit IC is composed of AND gates. A predetermined voltage Vcc is applied to one input terminal 1a of an AND gate 1 'provided in the IC1, and the other input terminal 1b is mounted on a printed wiring board so as to be grounded via a resistor R. In a normal state, a low level signal is output from the output terminal 2c of IC1 (AND gate 1 ′). However, if foreign matter 11 such as conductive dust or cutting oil adheres between the terminals 1a and 1b, the inputs of the AND gate 1 'are both at a high level, so that the output signal output from the output terminal 1c is High. Become a level. This High level signal is used as an alarm signal.

FIG. 2 shows a second embodiment in which the detection circuit IC 2 is constituted by an AND gate having three input terminals.
A predetermined voltage Vcc is applied to the central input terminal 2b of the 3-input AND gate 2 'provided in the IC 2, and the input terminals 2a and 2c on both sides are connected to the printed wiring board so as to be grounded via the resistor R. It is installed. In a normal state, a low level signal is output from the output terminal 2d. However, if foreign matter such as conductive dust or cutting oil adheres between the input terminals 2a and 2b or to the input terminals 2b and 2c, the inputs of the AND gate 2 'both become high level, so that the high level from the output terminal 2d. The alarm signal will be output.

  In the second embodiment, the example of the detection circuit IC 2 constituted by the three-input AND gate 2 ′ is shown, but an AND gate having three or more inputs may be used. In that case, when two adjacent input terminals are made conductive by foreign matter by connecting the terminals connected to the predetermined voltage Vcc and the input terminals connected to the grounded resistor R alternately, All the input terminals become high level inputs, and a high level signal alarm is output from the output terminals.

FIG. 3 shows a third embodiment in which the detection circuit IC 3 is configured by an OR gate.
A predetermined voltage Vcc is applied to one input terminal 3a of the OR gate 3 'provided in the IC 3 via a resistor R, and the other input terminal 3b is mounted on a printed wiring board so as to be grounded. In a normal state, a high level signal is output from the output terminal 3c. However, if foreign matter such as conductive dust or cutting oil adheres between the input terminals 3a and 3b, both inputs of the OR gate 3 become low level, so a low level signal is output from the output terminal 3c. A low level signal is used as an alarm signal.

  FIG. 4 shows a fourth embodiment in which the detection circuit IC 4 is composed of an OR gate 4 'having three input terminals.

  A predetermined voltage Vcc is applied to a central input terminal 4b of a three-input OR gate 4 'provided in the IC 4 via a resistor R, and the input terminals 4a and 4c on both sides are mounted on a printed wiring board so as to be grounded. Has been. In a normal state, a high level signal is output from the output terminal 4d. However, if foreign matter such as conductive dust or cutting oil adheres between the input terminals 4a and 4b or on the input terminals 4b and 4c, the inputs of the OR gate 4 'both become low level, so that the low level from the output terminal 4d. The alarm signal will be output.

  Also, in the case of the detection circuit IC 1 composed of an OR gate having three or more inputs, an input terminal to be grounded and an input terminal connected to the other end of the resistor to which a predetermined voltage is applied at once are alternately arranged. The connection should be as follows. Also in this case, when two adjacent input terminals are made conductive by a foreign substance, all the input terminals become low level inputs, and a low level signal alarm is output from the output terminals.

  Each of the embodiments described above uses an AND gate or an OR gate, but in addition to the AND gate or the OR gate, each logic circuit of NAND, NOR, EXOR, and EXNOR can be used. Since NAND, OR, NOR, EXOR, and EXNOR are also equivalent to the first to fourth embodiments described above, detailed description thereof is omitted. Further, these logic circuits do not need to be special, and can be general-purpose logic circuit ICs.

In addition to the logic circuit, a general-purpose differential receiver IC can be used.
FIG. 5 is an explanatory diagram of a fifth embodiment of the present invention using an IC 5 of a general-purpose differential input receiver circuit 5 ′. One input terminal 5 a of the differential input receiver circuit 5 ′ is grounded, and the other input terminal 5 b is applied with a predetermined voltage Vcc via a resistor R. Since there is usually a voltage difference between the input terminals 5a and 5b, the difference signal is output. However, when the input terminals 5a and 5b are contaminated with conductive foreign matter, the voltage difference becomes small or disappears, and the signal level output from the output terminal 5c changes. This changed signal is used as an alarm signal.

  FIG. 6 is an explanatory diagram of a sixth embodiment in which the IC 6 of the circuit 6 'having an output enable terminal is used as a detection circuit. A predetermined voltage Vcc is applied to the input terminal 6a of the circuit 6 'having an output enable terminal via a resistor R, and the output enable terminal 6 is grounded. A normal signal (High level signal) is output from the output terminal 6c in a normal state, but conductive foreign matter adheres between the input terminal 6 and the output enable terminal 6b, and the input terminal 6a is changed to the Low level. As a result, the signal level output from the output terminal 6c changes (changes to a Low level signal). This change in the output signal is used as an alarm signal.

  In each of the above-described embodiments, it has been detected that conductive foreign matter such as cutting oil or dust has adhered to the printed wiring board and the insulation has been lowered. There is no such thing as it corrodes the pattern of the printed wiring board. In the present invention, disconnection due to corrosion of the conductive pattern is detected by an IC such as a general-purpose logic circuit. FIG. 7 is an explanatory diagram of the seventh embodiment of the present invention in which the disconnection of the printed wiring board pattern is detected by the IC 7 of the AND gate 7 '.

  The input terminals 7a and 7b of the AND gate 7 'of the IC 7 provided with the AND gate 7' are connected to both ends of the pattern portion 8 on the printed wiring board where foreign matter is likely to adhere. One input terminal 7a side is applied with a predetermined voltage Vcc via a resistor R, and the other input terminal 7b is grounded via a resistor R.

  If the pattern portion 8 of the printed wiring board between the input terminals 7a and 7b is not disconnected, the input of both the input terminals 7a and 7b is at a high level, and therefore a high level signal is output from the output terminal 7c. . However, when the pattern portion 8 between the input terminals 7a and 7b is disconnected, the input of the input terminal 7 becomes a low level, so that the signal output from the output terminal 7 becomes a low level. This Low level signal is used as an alarm signal.

  As for the disconnection detection circuit, only the one using an AND gate is shown in FIG. 7, but this disconnection detection circuit is also composed of logic gates such as AND, NAND, OR, NOR, EXOR, and EXNOR having two or more terminals. You can also. Further, it can be constituted by an IC of a circuit having a differential receiver circuit or an output enable terminal.

  In each of the above-described embodiments, the output alarm signal is an interrupt signal for CPU processing such as a control device using a printed wiring board, input as an alarm signal to a DI (input circuit), LED It is used for lighting of LED, etc., to notify the deterioration and malfunction of the printed wiring board.

It is explanatory drawing of the 1st Embodiment of this invention. It is explanatory drawing of the 2nd Embodiment of this invention. It is explanatory drawing of the 3rd Embodiment of this invention. It is explanatory drawing of the 4th Embodiment of this invention. It is explanatory drawing of the 5th Embodiment of this invention. It is explanatory drawing of the 6th Embodiment of this invention. It is explanatory drawing of the 7th Embodiment of this invention. It is explanatory drawing of the cause which a malfunctioning generate | occur | produces with the foreign material adhering to a printed wiring board.

Explanation of symbols

1-7 IC (integrated circuit)
1 ′, 2 ′, 7 ′ AND gate 3 ′, 4 ′ OR gate 5 ′ differential receiver circuit 6 ′ circuit having output enable terminal 8 pattern portion

Claims (2)

  A printed circuit board provided with a circuit made of a conductive material on a substrate made of an insulating material, comprising a plurality of input terminals connected to a wiring connection portion provided on the printed circuit board, a logic circuit, and a differential receiver A printed wiring board characterized in that an integrated circuit composed of a circuit or an output enable circuit is disposed at a place on the printed wiring board where contamination is most likely to occur, and the integrated circuit detects an insulation failure between the input terminals. .   2. The printed wiring board according to claim 1, wherein the integrated circuit is a circuit that detects insulation between adjacent input terminals by detecting a change in output level from a normal output level.

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