JPH0435817Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention is designed to reduce the electrical overstress caused by electrostatic discharge to large-scale integrated circuits, integrated circuits, semiconductor elements, microstructured electronic components, and various electronic devices. or electromagnetic interference or various circuits as mentioned above,
This invention relates to an electrostatic discharge simulator that artificially generates electrostatic discharge in order to test and evaluate the susceptibility of parts, various electronic devices, etc. to electrostatic discharge.

(Prior Art) The electrostatic discharges to various electronic circuits, parts, various electronic devices, etc. mentioned above are most often caused by electrostatic charges on charged objects made of conductors insulated from the earth, especially the human body. Therefore, many electrostatic discharge simulators use equivalent models of a charged human body.

Figure 2 is a circuit diagram of the main parts of an example of a conventional electrostatic discharge simulator, where C _CD is a charging/discharging capacitor with a capacitance equivalent to that of a charged human body, and R _D is the resistance of a charged human body. SED is the discharge electrode, GAP is the discharge gap, and EUT is the test object.

The charging voltage of the human body usually ranges from several kV to a maximum of 30-odd kV, so a charging power supply circuit (not shown) is designed so that the charging voltage of the charging/discharging capacitor C _CD can be set in the range of OV to 30-odd kV. The equivalent capacitance of the charging/discharging capacitor C _CD and the equivalent resistance of the discharging resistor R _D are also determined according to the actual measured values of the human body, but since each value has a fairly wide range of variation, the representative Appropriate fixed values are selected from a range of 50 pF to 250 pF for the equivalent capacitance of the charging/discharging capacitor C _CD and 100 Ω to 1500 Ω for the equivalent resistance of the discharging resistor R _D.

After charging the charging/discharging capacitor C _CD in advance to the required voltage, when the discharging electrode SED is gradually brought closer to the EUT under test, the product of the length of the discharging gap GAP and the atmospheric pressure changes according to the charging voltage of the charging/discharging capacitor C _CD . The spark discharge that occurs when this value is reached causes the electric charge of the charging/discharging capacitor C _CD to be instantaneously applied to the EUT under test.

(Problem to be solved by the invention) In principle, the waveform of an electrostatic discharge current corresponds to an exponential curve, but due to causes specific to the spark discharge phenomenon in electrical discharge engineering, the actual waveform of the discharge current is The resulting waveform is quite different from the original waveform.

This kind of waveform change is due to the charging/discharging capacitor.
It has long been known that the voltage of C _CD depends on the change in the discharge starting voltage in the discharge gap GAP, but as a result of repeated discharge experiments using an electrostatic discharge simulator, the inventor of the present invention found the following. We were able to clarify that waveform changes occur due to various causes.

That is, when the electric charge of the charging/discharging capacitor C _CD is supplied to the discharge gap GAP, the conductivity of the spark space increases in the initial stage, and in the rising process, a part of the electric charge of the charging/discharging capacitor C _CD is lost in the spark space. The electric field strength in the spark space during the spark discharge generation process decreases, and this decrease in electric field strength weakens the effect of increasing conductivity, causing the conductivity to increase along a trajectory corresponding to the original rise time. The rise time of the discharge current is no longer carried out, and the discharge gap GAP
As a result, the waveform of the discharge current is distorted, reducing the reliability of the discharge test.

(Means and actions for solving the problem) In the discharge gap GAP between the discharge electrode SED of the electrostatic discharge simulator shown in Fig. 2 and the discharge electrode formed by a part of the EUT under test. There is a stray capacitance of about 1 pF to several pF depending on the surface area of the discharge electrode and the length of the discharge gap GAP.
At the beginning of spark discharge generation, the charge on the stray capacitance quickly disappears in the spark space, so the existence of the stray capacitance can be almost ignored. However, if the size of the stray capacitance is intentionally increased, the following operation occurs. It should be done.

That is, at the beginning of the spark discharge in the discharge gap GAP, the charge of the charge/discharge capacitor C _CD tries to be injected into the spark space via the discharge resistance R _D , but due to the discharge resistance R _D and the spark resistance in the discharge gap GAP, The amount of charge that is limited and injected into the spark space is extremely small.

However, since the charge of the stray capacitance is limited only by the spark resistance in the discharge gap GAP, regardless of the discharge resistance R _D , the amount of charge injected from the stray capacitance into the spark space is equal to the charge/discharge capacitor C C _D
The amount of charge injected from the spark gap is much larger than that of the spark, and as the conductivity in the discharge gap GAP increases, all of the charge in the stray capacitance is injected only into the spark space.

By reducing the impedance of the current path connecting the stray capacitance and the discharge gap GAP, charge can be quickly injected from the stray capacitance into the spark space, and most of the charge in the charge/discharge capacitor C _CD is lost. By flashing the discharge gap GAP without causing any damage, almost all of the charge in the charging/discharging capacitor C _CD can be applied to the EUT under test.

The energy applied to the EUT under test is
It is determined only by the current discharged from the charge/discharge capacitor C _CD through the discharge gap GAP, and is independent of the charge of stray capacitance.

This invention connects a capacitance element in parallel with the discharge gap in order to intentionally increase the stray capacitance existing in the discharge gap, and also reduces the impedance of the current path connecting this parallel capacitance element and the discharge gap. By making this extremely small, distortion of the waveform of the discharge current and An electrostatic discharge simulator that can significantly improve electrical characteristics such as the rise time of a discharge current compared to conventional ones, and that can extremely minimize variations in the electrical characteristics that occur for each discharge due to the uncertainty of a spark generation mechanism. The purpose is to realize the following.

FIG. 1 is a diagram showing the main parts of an embodiment of the present invention, in which BED ₁ , BED ₂ and BED ₃ are flanged counter electrodes;
CP is a cylindrical contact body in which a flange-shaped conductor is integrally connected to the lower edge of the cylindrical conductor, and its outer periphery is connected to a flange-shaped counter electrode.
Central electrode BED ₂ among BED ₁ , BED ₂ and BED ₃
It is fixed to the inner periphery of the

Incidentally, instead of forming the center electrode BED ₂ and the cylindrical contact body CP separately and then joining them together, it is also possible to form them into the desired shape by drawing a single conductive plate or other means. good.

HED is a hemispherical electrode, which is formed from a conductive thin plate with appropriate elasticity, and has radial notches around its periphery, and this periphery is used as a brim-shaped counter electrode.
It is pressed against the inner periphery of BED ₃ .

SUP is an insulating support made of suitable hard synthetic resin, etc., and has flanged counter electrodes BED ₁ , BED ₂ and BED ₃
The upper electrode
It is provided on each outer periphery of BED ₁ and lower electrode BED ₃ integrally with the electrode.

Note that, in order to prevent creeping discharge, a portion of the insulating support SUP covers the space between the inner peripheral edge of the electrode BED ₁ and the electrode BED ₂ , and between the inner peripheral edge of the electrode BED ₃ and the electrode BED ₂ . FS is an element that supports the discharge electrode and adjusts the discharge gap, and consists of a feed screw mechanism used in micrometers, etc., and can move the movable shaft forward or backward by rotating the rotation control knob in the forward or reverse direction. , so that the moving distance of the movable shaft can be indicated by a scale. SUP _T
is a protrusion for supporting the discharge gap adjustment element FS, which is made of the same material as the insulating support SUP, and is integrated with the insulating support SUP on the upper surface of the insulating support SUP, that is, the surface on the brim-shaped counter electrode BED ₁ side. The counter electrodes BED ₁ , BED ₂ and BED ₃ are made to protrude almost perpendicularly to the plate surfaces of the counter electrodes BED 1 , BED 2 and BED 3 , and a discharge gap adjusting element FS is inserted therein and fixed with a support HW. There is. The movable shaft of the discharge gap adjustment element FS is inserted into the cylindrical contact body CP inside the support protrusion SUP _T , is slidable in the axial direction, and is electrically connected to the cylindrical contact body CP. .

In order to make the movable axis of the discharge gap adjustment element FS slidable and to ensure electrical connection with the cylindrical contact body CP, the cylindrical contact body CP is formed of an elastic conductor, and the upper end portion An appropriate number of crimp pieces may be formed by providing an axial notch over an appropriate axial length. SED is a discharge electrode,
It is fixedly attached to the inner end surface of the movable shaft of the discharge gap adjustment element FS, and forms a pair of discharge electrodes together with the hemispherical electrode HED. NT is a cylindrical nut part,
It is made of the same material as the insulating support SUP, and the insulating support is placed outside the hemispherical electrode HED on the lower surface of the insulating support SUP, that is, the surface on the side of the brim-shaped counter electrode BED ₃ .
It is integrated with the SUP and installed protrudingly. ZS is a zero adjustment screw, made of the same material as the nut part NT, screwed onto the nut part NT, and formed so that its inner end is pressed into contact with the hemispherical electrode HED.

Note that by making the center axis of the zero adjustment screw ZS substantially coincide with the center axis of the discharge gap adjustment element FS, the zero adjustment described later can be performed accurately. CTT is a contact made of a rod-shaped conductor.The tip is sharpened, the rear end is screwed into a screw hole provided from the outer circumferential surface of the insulating support SUP toward the center, or it is firmly inserted, and the rear end is centered The surface is the periphery of the brim-shaped counter electrode BED ₂ (ground side electrode) or the electrode
It is installed so that it is electrically connected to the lead wire etc. from BED ₂ . The HOL is an insulating holding cylinder, and the peripheral part of the insulating support SUP is firmly fitted into the hole provided at the front end of the HOL, and if necessary, the insulating holding cylinder HOL and the insulating support SUP are connected using adhesive or set screws.
and an insulating holding cylinder.
A part of the peripheral part of the insulating support SUP inserted into the hollow interior of the HOL is cut out to form a flanged counter electrode on the top.
A part of the peripheral edge of BED ₁ and the lower brim-shaped counter electrode BED ₃ is exposed in the hollow interior of the insulation holding cylinder HOL, and both electrodes are electrically connected at this part, or the brim-shaped counter electrode BED 1 and the lower brim-shaped counter electrode BED ₃ are connected electrically. Each end of each lead wire connected to BED ₃ is introduced into the hollow interior of the insulation holding cylinder HOL, and both lead wires are electrically connected. The brim-like counter electrodes BED ₁ and BED ₃ may be connected to each other at any peripheral portion in addition to the above connection points, and the contact CTT and the center brim-like counter electrode BED ₂ may be connected to each other at any peripheral portion.
It may be electrically connected to the entire circumference except for the connection part.

In addition, when connecting the insulating support SUP and the insulating holding tube HOL together, the axial direction of the contactor CTT and the axial direction of the insulating holding tube HOL are made to almost match, thereby making handling operations during the discharge test easier. You can do it if it's easy.

Although not shown in the figure, a charging/discharging capacitor and a discharging resistor are installed inside the hollow interior of the insulating holding cylinder HOL, and a connecting wire to the charging power supply circuit is introduced from the rear end or side wall of the insulating holding cylinder HOL, Connect the high potential side electrode of the charge/discharge capacitor C _CD to the flanged counter electrodes BED ₁ and BED ₃ (high voltage side electrode) via the discharge resistor, and connect the high potential side of the connection wire to the charging power supply circuit. Connect to the line and also charge/discharge capacitor
Connect the low-potential side electrode of C _CD to the low-potential side connection wire among the connection wires to the charging power supply circuit, and then connect it to the appropriate part of the discharge gap adjusting element FS, its support HW, or the contactor CTT. Connect an appropriate high resistance between the point electrically connected to the brim-shaped counter electrode BED ₂ (ground side electrode) and the ground air.

In the electrostatic discharge simulator of the present invention constructed in this way, the scale is made to match zero by operating the knob of the discharge gap adjustment element FS, and the zero adjustment screw is
Zero adjustment is performed by rotating ZS and bringing the discharge electrode SED into close contact with the inner bottom wall of the hemispherical electrode HED.
To detect the close contact between SED and hemispherical electrode HED,
For example, keep the charging power supply circuit in an open state, and connect the connection wire to the charging power supply circuit, the connection wire on the high potential side, and the appropriate parts of the discharge gap adjustment element FS or its support.
A circuit tester or the like is used to detect interruption or continuity between the HW or the contactor CTT, that is, the discharge electrode SED and the electrically connected location. That is, the zero adjustment screw
If you rotate ZS in the opposite direction and move it backwards,
Due to the elasticity of the hemispherical electrode HED, the top recedes while maintaining contact between its periphery and the flanged counter electrode BED ₃ , breaking contact with the discharge electrode SED, and rotating the zero adjustment screw ZS in the positive direction. and hemispherical electrode HED
When the zero adjustment screw ZS is moved forward against the elasticity of
The peripheral part of the hemispherical electrode HED is pressed against the surface of the brim-shaped counter electrode BED ₃ and deforms while sliding and expanding in the radial direction, and the top part moves forward and comes into contact with the discharge electrode SED, so the circuit test is performed. Completion of zero adjustment can be confirmed by reading changes in the deflection of the instrument's pointer.

After completing the zero adjustment, adjust the length of the discharge gap to the required value by operating the knob of the discharge gap adjustment element FS, and then touch the tip of the contactor CTT to the desired location on the test object to remove the charge/discharge capacitor. When charged, discharge occurs when the charging voltage reaches a voltage corresponding to the length of the discharge gap.

In addition, in FIG. 1, three flanged counter electrodes BED ₁ ,
Although the case where parallel capacitance is formed by BED ₂ and BED ₃ is illustrated, electrode BED ₁ is omitted and electrode BED ₂ is
The present invention can be implemented even if a parallel capacitance is formed by BED 3 and BED ₃ .

(Effect of the invention) In the electrostatic discharge simulator of the present invention, a capacitance in parallel with the discharge gap is formed by the flanged counter electrodes BED ₁ , BED ₂ and SED ₃ , and this parallel capacitance and the discharge gap are Since the hemispherical electrode HED that forms the discharge electrode is connected to the discharge electrode SED, the movable shaft of the discharge gap adjustment element FS, and the cylindrical contact body CP, the impedance at this connection part is extremely small. be.

When charging the charge/discharge capacitor, when charging the charge/discharge capacitor with the contactor CTT in contact with the test object in advance, the insulating holding tube
Discharge resistor and flanged counter electrode built into HOL
BED ₁ , BED ₃ and BED ₂ , contactor CTT and flanged counter electrodes BED ₁ , BED ₂ and
When a parallel capacitor consisting of BED ₃ is charged together with a charge/discharge capacitor and the charge/discharge capacitor is charged without contacting the contactor CTT with the test object, the discharge gap adjustment element FS or its support may be The high resistance inserted between the part electrically connected to the flanged counter electrode BED ₂ such as HW or contactor CTT and the ground air, and the discharge resistor built into the insulation holding tube HOL, Counter electrode BED ₁ ,
The parallel capacitance consisting of BED ₂ and BED ₃ is also charged,
When the charge/discharge capacitor is discharged, a large amount of charge from the parallel capacitor is quickly injected into the spark space, causing the discharge gap to flash without losing much of the charge/discharge capacitor's charge. According to the results of experiments conducted by changing the capacitance of the charge/discharge capacitor, the resistance value of the discharge resistor, the length of the discharge gap, etc., it was found that the rise time and It was confirmed that the electrical characteristics such as waveform distortion were significantly improved compared to the conventional method, and that the variation in the electrical characteristics between discharges was also extremely small.

Furthermore, if the resistance value of the high resistance provided for charging the parallel capacitance consisting of the brim-shaped counter electrodes BED ₁ , BED ₂ , and BED ₃ is made appropriately larger than the impedance of the test object, the discharge current can be increased. There is no risk of the current being shunted to this high resistance.

[Brief explanation of the drawing]

FIG _. 1 is a diagram showing an embodiment of the present invention, and FIG _{. 2} is a diagram showing an example of a conventional electrostatic discharge simulator. Cylindrical contact body, HED... hemispherical electrode,
SUP...Insulating support, FS...Discharge gap adjustment element, SUP _T ...Protrusion, HW...Support, SED...
...discharge electrode, NT...nut part, ZS...zero adjustment screw, CTT...contact, HOL...insulation holding cylinder,
C _CD ...Charging/discharging capacitor, R _D ...Discharging resistor,
GAP...discharge gap, EUT...test object.

Claims (1)

[Scope of utility model registration request] A flange-shaped counter electrode facing each other at an appropriate interval, a cylindrical contact body integrally provided in the center portion of the ground side electrode within the flange-shaped counter electrode, and an insulator provided on the outer periphery of the flange-shaped counter electrode. a support, a discharge gap adjusting element supported by the insulating support and having a movable shaft slidably slidable while maintaining contact with the cylindrical contact body; and a discharge gap adjusting element that is movable in the discharge gap adjusting element. A discharge electrode attached to the inner end of the shaft, a hemispherical electrode whose peripheral portion is pressure-welded to the inner periphery of the high-voltage side electrode in the brim-shaped counter electrode and is opposed to the discharge electrode, and the insulating support. A zero adjustment screw is screwed into a partially protruding cylindrical portion and has its inner end pressed into contact with the hemispherical electrode; A contact made of a conductor connected to the ground side electrode in the counter electrode, and a charging/discharging capacitor connected to the high voltage side electrode in the flanged counter electrode via a discharge resistor are installed inside the insulating support. An electrostatic discharge simulator characterized by comprising: an insulating holding tube attached to the simulator.