JP2872301B2 - Ground disconnection detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground wire disconnection detecting device for detecting the presence or absence of a ground wire disconnection, and more particularly, to a ground wire disconnection for preventing electrostatic breakdown of a semiconductor device. The present invention relates to a technology that is effective for detection.

[Conventional technology]

2. Description of the Related Art In a process of manufacturing a semiconductor device such as a high-frequency device or a MOS IC (metal oxide semiconductor integrated circuit), if a static level of a working environment exceeds a certain value, electrostatic breakdown may be caused. For this reason, consideration must be given to the environment of the work site. Specifically, the following countermeasures are taken.

Do not bring easily charged insulators to the work site.

Avoid low humidity atmosphere.

Forming a conductive atmosphere (eg, a conductive mat,
Conductive containers, anti-static work clothes, use of air ionization blowers, etc.).

Measurement equipment, test equipment,
Ground the workbench, tools, solder bath, soldering iron, etc.

The worker's arms and legs are grounded to the human body via bracelets and ankles.

By taking the above countermeasures, the static electricity level exerted on the semiconductor device can be reduced to a specified value or less, and the semiconductor device can be protected from electrostatic breakdown.

For details of such measures, see, for example, “Semiconductor Device Reliability Handbook” published by Hitachi, Ltd. 4-23
There is a description on the page.

By the way, the present inventor has studied the effect of disconnection of the ground wire used for human body grounding.

The following is a technique studied by the present inventors, and the outline is as follows.

In other words, semiconductor devices often depend on the manual work of workers, and if static electricity is charged on the human body, hand- →
Discharge from semiconductor device to ground. If the static electricity level at this time exceeds the allowable value of the semiconductor device, electrostatic breakdown is caused and the product yield is reduced.

Therefore, in general, a method is adopted in which a conductive bracelet or ankle is attached to an arm or a foot of a worker, and the armlet or the annulus is connected to the ground via a ground wire to form a discharge circuit. ing. In addition, workers wear conductive footwear, lay a grounded conductive mat on the floor of this work area,
A method has also been adopted in which the work is performed on this mat so that the human body is grounded via footwear so that the human body is not charged.

Similarly, the measurement equipment, test equipment, and various facilities are also grounded via a ground wire.

[Problems to be solved by the invention]

However, as described above, it is essential to connect a ground wire when grounding the human body or the apparatus, but if the ground wire is broken, the discharge path is cut off, which may cause damage to the semiconductor device. Become. And
Since this ground wire is usually coated with vinyl, even if there is a disconnection, it cannot be determined from the outside, and as a result of working without noticing the disconnection, there is a problem that defective products are successively generated. Have been found by the present inventors.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a ground wire disconnection detecting device which can immediately detect a ground wire disconnection.

The above objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[Means for solving the problem]

The outline of a representative invention among the inventions disclosed in the present application will be briefly described as follows.

That is, the ground disconnection detection device of the present invention includes a band that holds a pair of electrodes that are separately disposed so as to be able to contact a human body,
The skin resistance formed between the pair of electrodes by contact with the skin of the human body when the band is worn on a human body is used as a part of a voltage dividing circuit, and a low potential end of the voltage dividing circuit is connected to a high resistance. Grounded, between the human body and the ground according to a change in output voltage caused by the wearing or non-wearing of the band, poor contact between the pair of electrodes and skin, disconnection of lead wires of the pair of electrodes, etc. A first voltage generation circuit for detecting electrical contact or interruption, and a power supply,
A primary winding that excites a secondary winding of the first voltage generation circuit, outputs a DC voltage, and has one output terminal commonly connected to a ground terminal of the first voltage generation circuit; A second voltage generation circuit connected to the ground via a wire, for detecting contact or interruption of the ground wire with the ground based on a change in the DC voltage caused by disconnection or the like of the ground wire; Determining means having input terminals respectively connected to output terminals of the second voltage generating circuit, and determining a disconnection state according to a preset logical condition using each output voltage of the first and second voltage generating circuits; Is provided.

[Action]

According to the above means, the output voltage of the first voltage generation circuit changes in level according to the conduction / interruption between the leads connected to the electrodes of the band worn on the human body, while the second voltage generation circuit The output voltage of the circuit changes in a binary manner depending on whether or not the ground wire is disconnected from the ground. Therefore, it is possible to determine the ground disconnection and the band lead disconnection from the comparison of the output voltages of the respective voltage generation circuits.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of a ground wire disconnection detecting device according to the present invention. 2 and 3 are an inner perspective view and an outer perspective view showing details of an arm electrode.

The transformer 1 has two secondary windings n ₂₁ and n ₂₂ and one primary winding n _1, and the primary winding n ₁ is connected to a commercial AC power supply (for example, AC
100V). Between the primary winding n _1, resistors 2 and 3 for dividing the AC voltage is inserted by connecting in series.
One end of a resistor 4 is connected to a connection point between the resistors 2 and 3,
The other end is connected to the ground via a ground wire 5.
In the first figure, the connection point of the resistors 3 and the primary winding n ₁ indicates a state in which ground all, as is well known, the primary winding n ₁ is connected to the transformer 1 The distribution line is grounded at the pole transformer. Therefore, in use, it is not necessary to ground _one of the primary windings n1 of the device.

The anode of a diode 6 for half-wave rectification is connected to the high potential side of the resistor 4, and a smoothing capacitor 7 is connected between the cathode of the diode 6 and the other end of the resistor 4. Further, a resistor 8 as a load is connected to the capacitor 7 in parallel. A circuit from the above voltage dividing means to obtaining a smoothed DC voltage by the capacitor 7 forms a second voltage generating circuit. The second voltage generating circuit is for detecting contact or interruption of the earth line 5 with the ground based on the change of the DC voltage.

Next, the configuration of the first voltage generation circuit for detecting electrical contact or interruption between the human body and the ground will be described.

Low voltage (e.g., about 20 Vrms) to one end of the secondary winding n ₂₁ of the transformer 1 that outputs is connected to one end of a resistor 9 for preventing shocks, the other end and the other end of the resistor 4 (GND: Ground line )
It is connected to the. To the other end of the resistor 9, a protection resistor 10 for preventing the human body from being applied with a high voltage (a voltage generated when the band-side electrode and the human body are brought into a half-contact state, which will be described later), A buffer resistor 11 is connected in series.
The cathode of the diode 30 is connected between the resistors 10 and 11, and one end of the resistor 31 is connected to the anode. The other end of the resistor 31 is connected to GND. The anode of a diode 12 for half-wave rectification is connected to the resistor 11, and a resistor 13 as a load is connected between its cathode and the other end (GND) of the resistor 4. To this resistor 13, a smoothing capacitor 14 is connected in parallel.

The cathodes of the diode 12 and the diode 6 are connected to the input terminal of an AND gate 15 which receives the voltages E ₁ and E ₂ , and the output terminal of the AND gate 15 amplifies the output signal of the AND gate 15. An alarm circuit 16 is connected as a determination means for generating a signal. An output terminal of the alarm circuit 16 is connected to a speaker 17 that converts an alarm signal into an electric signal. In addition, the alarm circuit 16 outputs a disconnection determination signal Sc, and direct use such as stopping a line using this signal or indirect use such as reporting to a management center can be performed. .

Further, a band 29 as shown in FIGS. 2 and 3 is connected to the resistor 10. The band 29 is mainly composed of a band 18 made of an insulating and flexible cloth or the like, and two electrodes 19a and 19b are parallel to each other in the longitudinal direction inside the band 18 so that the surface can contact the human skin. Mounted on The electrodes 19a and 19b are made of a material having flexibility so that the electrodes 19a and 19b can be wound around the wrist (or ankle) of the human body. The electrodes 19a and 19b are held in an electrically insulated state, and when the band 29 is correctly attached to, for example, a wrist of a human body, skin resistance due to contact with the human body between the electrodes 19a and 19b is reduced. Is to occur.

A jack 20 connected to each of the electrodes 19a and 19b is attached to an end of the surface of the band 18. This jack 20
, A plug 21 to which a lead wire 22 is connected is detachably mounted. Further, a plug 23 is connected to the other end of the lead wire 22 having such a length that does not cause any inconvenience in the operation, and can be inserted and connected to a jack 24 connected in parallel with the resistor 10.

As shown in FIG. 2, a narrow surface fastener 25 is sewn (or stuck) to the inner surface of the band 18 at one end thereof in the width direction. In addition, a surface fastener 26 having a size larger than the surface fastener 25 is attached to the other end of the surface of the band body 18 (an opposite end where the surface fastener 25 is mounted) so that the belt fastener 25 can be coupled to the surface fastener 25 in the same manner. Installed by.

Incidentally, the secondary winding n _22, used to drive an alarm circuit 16, rectifying circuit (not shown), a smoothing circuit, a power supply circuit configured to include a like voltage stabilizing circuit provided if necessary 28 are connected.

Next, a description will be given of a usage method and a circuit operation of the embodiment having the above configuration.

First, when the power supply plug 27 of the device is inserted into the outlet of the commercial power supply line, an AC voltage e ₄ is generated at both ends of the resistor 4 and the AC voltage corresponding to the turns ratio is applied to the secondary windings n ₂₁ and n _22. Occurs. This voltage e ₄ is half-wave rectified by the diode 6 and further smoothed by the capacitor 7 to be converted into a DC voltage. This voltage E ₂ occurs in the resistor 8, the voltage E ₂ is the AND gate 15
Is applied to the input terminal b.

On the other hand, the voltage e ₁ generated in the secondary winding n ₂₁ is attenuated sequentially through the resistors 9, 10, 11 forming an attenuator, and the stepped-down voltage is applied to the diode 12. Diode 12
Supplies half-wave rectification of the applied voltage to the resistor 13.
The resistor 13 is smoothed to the capacitor 14 is connected, the DC voltage E ₁ is supplied removed the ripple in the resistor 13. This voltage E ₁ is applied to input terminal a of the AND gate 15. The diode 30, resistor 31 is for e ₂ is AC.

By the way, the skin resistance of the human body is usually 2-3 MΩ,
If, for example, 40 MΩ is used for the resistor 10, the terminal voltage e ₂ of the resistor 10 changes depending on whether the plug 23 is inserted into the jack 24, and the voltage e _{3 at} the output side of the resistor 11 and the diode output voltage E ₁ of the 12 changes.

That is, when the plug 23 is not inserted, the high attenuator is connected, and the voltage applied to the load resistance (resistance 13) decreases. On the other hand, when the plug 23 is inserted and in the conductive state, the low attenuator is connected, and the voltage applied to the load resistance increases. In this embodiment, the output voltage E ₁ of the diode 12 is configured to vary under the following conditions.

When the plug 23 is not inserted into the jack 24, or when the circuit of the band 29 connected to the plug 23 is disconnected, the voltage E ₁ = + 0.66V. Normal circuit (when a loop is formed without disconnection)
When it is, the voltage E ₁ = + 5.13V Further, in the second voltage generating circuit, the presence or absence of connection of the ground wire 5 (disconnected), the output voltage E ₂ is changed. In this embodiment, it changes under the following conditions.

When the ground wire 5 is connected and conducting, the voltage E ₂ = + 4.16V When the ground wire 5 is disconnected (or unconnected), the voltage E ₂ = 0V In this case, the return line of the resistor 4 is eliminated. For,
The voltage e ₄ disappears, so that E ₂ = 0.

The AND gate 15 operates to change the output voltage from "L" level to "H" level when both the input terminals a and b are at "H" level. When one of the input terminals or both inputs are at “L” level, the output voltage becomes “L”.
Operate to level. Normally, the non-operating voltage is +2.4 V or less (TTL level). When the non-operating voltage is higher than this, the circuit operates as the "H" level.

Further, the output of the AND gate 15 is "L"
When the level is at the level, the speaker 17 is driven and a disconnection determination signal Sc is generated.

From the above facts, when the plug 23 is not inserted into the jack 24 and the ground wire 5 is normal (meaning the connection state and the conduction state), the voltage E ₁ = + 0.66 V and the voltage E ₂
= 4.61V is applied to the AND gate 15, the logical product condition is not satisfied, the output is at the "L" level, and the band 29 is not attached by an alarm sound (intermittent sound, continuous sound, etc.) I do.

Further, while the voltage E ₁ remains in the state of E ₁ = + 0.66 V (that is, the state in which the plug 23 is not inserted into the jack 24),
When the ground wire 5 is disconnected or unconnected and the voltage E ₂ =
When it becomes 0, the input terminals of the AND gate 15 are both at the “L” level, and the logical product condition is not satisfied.
The 15 output is at the "L" level. As a result, the speaker 17 is driven, and a warning is given that the ground wire 5 is disconnected or unconnected.

Next, a case where the band 29 is worn will be described.

For example, when the band 29 is worn on the wrist, the band 18 is wound around the wrist with the electrodes 19a and 19b inside, and is held so that no gap is formed between the electrodes 19a and 19b and the skin. The hook-and-loop fastener 25 and the hook-and-loop fastener 26 are brought into contact with each other to fix the ends of the band body 18 together. Then Jack 20
The plug 21 is inserted into the jack 24, and the plug 23 is further inserted into the jack 24, whereby the mounting is completed.

When the lead wire 22 is not broken and the electrodes 19a and 19b are both in close contact with the skin, as described above, the skin resistance caused by the contact between the electrodes 19a and 19b and the skin of the human body ( 2-3 MΩ) are connected in parallel, and the resistance between the resistors 10 is reduced. Therefore, when the terminal voltage e ₂ is in this embodiment, reduced as follows.

e ₂ = + 18.6 Vrms → + 9.09 Vrms As a result, the voltage E ₁ rises from +0.66 V to +5.13 V. At this time, the ground wire 5 is normal (connected and conductive)
If it is, the voltage E ₂ is + because it is 4.61V, the input terminal of the AND gate 15 becomes both "H" level. Therefore,
The output of the AND gate 15 becomes “H” level, and the alarm circuit 16
Is in a non-operating state, no alarm is issued, and no disconnection determination signal Sc is output.

Here, the lead wire 22 is disconnected, or the electrodes 19a, 19b
If there is a gap between the skin and the skin, the voltage e ₂ is uniquely determined by the resistor 10, and the voltage e ₂ is from +9.09 Vrms to +18.6
Turns to Vrms. Therefore, the AND gate 15 has the input terminal a falling from + 5.13V to + 0.66V and the input terminal b having +4.
Since it is 61V, the logical product condition is not satisfied, and the alarm circuit 1
6 becomes operational. As a result, the speaker 17 gives a warning by a warning sound, and also outputs the disconnection determination signal Sc.

In addition, the band 29 is not attached (the lead wire 22 is disconnected, the plug 23 is detached and not inserted, the contact between the electrodes 19a and 19b and the skin is poor, etc.), and the ground wire 5 is disconnected (the ground wire 5 is not connected).
Unconnected, disconnected, etc.), the input terminal a
0.66V and the input terminal b becomes 0V. Therefore, the inputs of the AND gate 15 both become “L” level, and as a result, the AND condition is not satisfied. As a result, the alarm circuit 16 is activated, an alarm is issued by the speaker 17, and the disconnection determination signal Sc is also output. Is done.

In the above embodiment, the voltage supplied to the resistor 4 is obtained from a commercial power supply. Alternatively, a DC power supply such as a dry battery or a secondary battery is DC-DC converted to obtain a desired voltage. A configuration that can be obtained is conceivable. But in this case,
In place of the earth ground of the pole transformer, a dedicated ground wire must be provided separately, and the effects of this disconnection, poor connection, and unconnection must be newly considered. It is disadvantageous in comparison.

As described above, the invention made by the inventor has been specifically described based on the embodiment. However, it is needless to say that the present invention is not limited to the embodiment, and various changes can be made without departing from the gist of the invention. No.

For example, the voltage supplied to the resistor 4 is obtained by dividing the AC voltage by the resistors 2 and 3,
A capacitor may be used instead of a few.

Further, in the above embodiment, the band 29 is fixed by the hook-and-loop fastener, but a belt may be provided at both ends, and both may be connected with a hook and a stop hole, or a string may be provided and connected. Good.

Furthermore, although the electrodes 19a and 19b have shown examples of linear shapes,
Alternatively, a spiral shape, a waveform, a maze shape, or the like may be used so as to minimize skin resistance between the electrodes.

In the above description, the invention made mainly by the present inventor is intended for detection of disconnection of a ground wire accompanying the manufacture of a semiconductor device as a field of use, but the invention is not limited to this. It can also be applied to disconnection detection of electrical equipment and facilities where connection of the above is essential.

〔The invention's effect〕

The effects obtained by typical aspects of the invention disclosed in the present application will be briefly described as follows.

That is, according to the present invention, it is possible to reliably detect a disconnection of a ground wire or the like that causes electrostatic breakdown, minimize the electrostatic breakdown of a semiconductor device, and improve the product yield. It becomes possible to plan.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a ground wire disconnection detecting device according to the present invention. 2 and 3 are an inner perspective view and an outer perspective view showing details of the arm electrode. 1… Transformer, 2,3,4,8,9,10,11,13,31 …… Resistance, 5…
... Earth wire, 6, 12, 30 ... Diode, 7, 14 ... Capacitor, 15 ... AND gate, 16 ... Alarm circuit, 17 ... Speaker, 18 ... Strip, 19a, 19b ... Electrode, 20, 24 ... Jack, 21, 23 ... Plug, 22 ... Lead wire, 25, 26 ... Surface fastener, 27 ... Power plug, 28 ... Power circuit, 29 ...
…band.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-21467 (JP, A) JP-A-2-183996 (JP, A) JP-A-1-140799 (JP, U) JP-A-63 99699 (JP, U) Actually open sho 64-16100 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05F 1/00-3/04 H02H 3/08-3/253

Claims (4)

(57) [Claims] 1. A band for holding a pair of spaced electrodes so as to be in contact with a human body, and a skin resistance formed between the pair of electrodes due to contact with the skin of the human body when the band is worn on the human body. Used as a part of a voltage divider circuit and the low potential end of the voltage divider circuit is grounded to ground via high resistance, the band is worn or not worn, poor contact between the pair of electrodes and skin, and the pair of electrodes. A first voltage generation circuit for detecting electrical contact or interruption between a human body and ground in response to a change in output voltage caused by a disconnection of a lead wire of the electrode; It has a primary winding that excites a secondary winding of the voltage generation circuit, outputs a DC voltage, and has one output terminal commonly connected to a ground terminal of the first voltage generation circuit, and via a ground line. Connected to ground, disconnection of the ground wire, etc. A second voltage generation circuit for detecting contact or interruption of the ground line with the ground based on the change in the DC voltage caused by the change, and inputs connected to output terminals of the first and second voltage generation circuits, respectively. A ground disconnection detecting device having a terminal and determining a disconnection state according to a preset logical condition using each output voltage of the first and second voltage generating circuits. 2. The band includes two flexible electrodes, an insulative and flexible band disposed so that the two electrodes can contact the skin of a human body, and a band of the band. 2. The ground wire disconnection detecting device according to claim 1, further comprising: an engaging member for detachably fixing both ends. 3. The system according to claim 1, wherein said second voltage generating circuit obtains an input voltage by dividing a commercial power supply, and uses a ground of a pole transformer as a return circuit.
The ground disconnection detecting device according to the above. 4. The method according to claim 1, wherein the determining means determines that a logical product of a rectified output voltage of a low potential terminal output of the first voltage generation circuit and a rectified output voltage of the second voltage generation circuit is satisfied. 2. The ground wire disconnection detecting device according to claim 1, wherein the disconnection of the ground wire and the disconnection of the loop between the band and the first voltage generating circuit are determined.