JPH0528532Y2 - - 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) Electrostatic discharges to the various electronic circuits, components, and various electronic devices described above are most often caused by static electricity being discharged from a charged body made of a conductor insulated from the ground, particularly the human body, and therefore most electrostatic discharge simulators use an equivalent model 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 discharge 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. During the spark discharge generation process, the electric field strength in the spark space decreases, and this decrease in electric field strength weakens the effect of increasing conductivity, causing the conductivity to increase along the trajectory corresponding to the original rise time. is no longer performed, and the rise time of the discharge current becomes shorter than the discharge gap.
There is a significant delay compared to the fixed time determined depending on the length of the GAP and the atmospheric pressure, and 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 discharge current compared to conventional ones, and can also minimize variations in the electrical characteristics that occur from discharge to discharge due to uncertainty in the 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 BOW is a bowl-shaped supporting conductor, BED is a brim-shaped electrode,
It is integrally attached to the periphery of the bowl-shaped support conductor BOW. GUD is a guide tube with an axial keyway KG, which is integrally attached to the top of the bowl-shaped support conductor BOW, and the keyway of the hole bored in the approximate center of the bowl-shaped support conductor BOW and the keyway of the guide tube GUD. It is connected so that the position matches with KG. INS _s
is an insulating layer, which covers the inner and outer surfaces of the bowl-shaped supporting conductor BOW, the front and back surfaces of the brim-shaped electrode BED, its periphery, and the guide tube.
A key groove with the same size and key groove position as the hole is provided integrally over the outer circumferential surface of the GUD at a location corresponding to a hole with a key groove bored approximately in the center of the bowl-shaped support conductor BOW. A grooved hole is provided.

In addition, the bowl-shaped support conductor BOW and the guide tube GUD are formed into a rigid body using a relatively thick conductor, and the flange-shaped electrode
The BED is formed of a relatively flexible conductor, and the insulating layer _INS is formed of a rubber elastic material, or the bowl-shaped supporting conductor BOW, the guide tube GUD, and the brim-shaped electrode BED are all formed of a flexible conductor. At the same time, a bowl-shaped supporting conductor is placed inside the insulating layer INS _s.
By forming the insulating layer portions corresponding to the surfaces of the BOW and guide cylinder GUD using a hard insulating synthetic resin, etc., and forming the insulating layer portion corresponding to the surface of the brim-shaped electrode BED using a soft insulating synthetic resin, a bowl-shaped Although it is most desirable to form the support conductor BOW and the guide tube GUD part in a rigid body shape, and to form the brim electrode BED part in a flexible manner, the present invention can also be implemented even if the entire body is formed in a rigid body shape. I can do it.

Further, instead of forming the guide tube GUD from a conductor as described above, it may be formed from an insulating hard synthetic resin.

SUP is a rod-shaped movable conductor, with an axial protrusion KY provided on the front half and a screw cut on the rear half, so that the axial protrusion KY matches the keyway KG of the guide tube GUD and is inserted into the guide tube GUD. It is formed so that it can slide in the axial direction while maintaining electrical connection with the bowl-shaped support conductor BOW. The SED is a discharge electrode attached to the front end of the rod-shaped movable conductor SUP. HOL is a cylindrical insulating support, and HAN is a handle, which is integrally attached to the cylindrical insulating support HOL. DS
is a feed screw, and by interposing the inner periphery of a hole drilled in the front end wall of the cylindrical insulating support HOL between the screw body and the flange-like protrusion provided on its back, the feed screw DS can be shaped into a cylindrical shape. It is rotatably supported on the front end wall of the insulating support HOL, and the rod-shaped movable conductor
It is screwed onto the screw provided on the rear half of the SUP.
The feed screw DS is formed of a hard insulating synthetic resin or a suitable metal material, and when formed of a metal material, an insulating layer is provided on the outer surface in the same manner as the bowl-shaped supporting conductor BOW. The EUT is the object under test,
INS _E is an insulating layer provided on its surface.

Although not shown in the figure, the cylindrical insulating support HOL
A charging/discharging capacitor and a discharging resistor are installed inside the hollow, and a connecting wire and a return wire to the charging power supply circuit are introduced through the insulating handle HAN, and inside the connecting wire,
Connect the high potential side wire to the high potential side electrode of the charge/discharge capacitor via a buffer resistor, and connect the low potential side wire of the connection wire to the low potential side electrode of the charge/discharge capacitor. The high potential side electrode of is connected to the rear end of the rod-shaped movable conductor SUP via a discharge resistor, and the inner end of the return wire is connected to the low potential side electrode of the charging/discharging capacitor.

In the electrostatic discharge simulator of this invention, the equivalent capacitance of the charge/discharge capacitor is selected from a range of 50 pF to 250 pF, and the equivalent resistance of the discharge resistor is selected from a range of 100 Ω to 1500 Ω. The charging power supply circuit is formed of a high-voltage DC source, a power switch, a charging resistor, etc., and is configured so that the charging voltage of the charging/discharging capacitor can be set appropriately over a range of 0V to 30-odd kV.

In the electrostatic discharge simulator of the present invention configured in this way, the feed screw DS is rotated in the opposite direction to retract the rod-shaped movable conductor SUP and the discharge electrode SED to the maximum extent, and the ground terminal of the EUT under test or the wall of the housing, etc. In addition to grounding the middle and grounding points, connect the outer end of the return wire to the grounding terminal of the EUT under test or to the grounding point, and connect the discharge electrode SED directly to the required discharge point to connect the flanged electrode BED. After the part is brought into close contact with the surface of the EUT under test and the charging/discharging capacitor is charged to the required voltage, the charging power supply circuit is opened and the feed screw DS is rotated in the positive direction to gradually disconnect the bar-shaped movable conductor SUP and the discharge electrode SED. When the discharge electrode SED is moved forward to The spark discharge that occurs when the dielectric breakdown gap length determined by the material of the insulating layer INS _E on the surface of the EUT is reached causes the electric charge of the charging/discharging capacitor to be instantaneously applied to the EUT under test, and is transferred via the return wire. and return to the charge/discharge capacitor.

During this discharge, the electromagnetic energy that is about to be radiated from the connection line to the charging power supply circuit as the potential of the high-potential side electrode of the charging/discharging capacitor decreases is suppressed by the buffer resistor, and the discharge test There is no risk of giving an error.

As mentioned above, after charging the charge/discharge capacitor with the discharge gap length increased, instead of gradually narrowing the discharge gap to cause discharge, the flange-shaped electrode BED portion is connected to the EUT under test. If the charging/discharging capacitor is charged after the charging/discharging capacitor is brought into close contact with the surface and the discharge gap is adjusted to an appropriate length in advance, a spark discharge will occur when the charging voltage of the charging/discharging capacitor reaches the discharge starting voltage at the discharge gap. However, in this case, the charging/discharging capacitor is immediately recharged after discharging, and discharging is repeated until the charging power supply circuit is opened.

In this case, for example, an electromagnetic induction element or an electrostatic induction element is provided in the discharge circuit to detect the discharge current, and the charging power supply circuit is automatically opened based on this detection output. can be limited to one time.

(Effect of the invention) In the electrostatic discharge simulator of the present invention, a discharge gap is formed between the discharge electrode SED and the discharge electrode formed by a part of the conductor part of the EUT under test that directly faces the discharge electrode SED, and the discharge gap is formed in the shape of a flange. electrode
BED and the test object facing this brim-shaped electrode BED
Capacitance is formed between some conductor parts of the EUT,
Furthermore, this capacitance is transferred to the discharge electrode via the brim-shaped electrode BED, the bowl-shaped support conductor BOW, and the rod-shaped movable conductor SUP.
In addition to being connected to the SED, the conductor part that is involved in capacitance formation and the conductor part that is involved in discharge electrode formation on the EUT side under test are connected by the conductor part that is interposed between them. Flange-shaped electrode
The capacitance formed by the BED and the corresponding part of the conductor on the EUT side is the discharge electrode.
It is connected in parallel to the discharge gap formed by the SED and a corresponding part of the conductor on the side of the EUT under test, and the impedance of the connected circuit is extremely small.

When charging the charge/discharge capacitor, a discharge resistor, a rod-shaped movable conductor SUP, a bowl-shaped support conductor BOW,
The parallel capacitance formed by the flange-shaped electrode BED, a part of the conductor of the EUT under test, and the part of the conductor of the EUT under test that faces the flange-shaped electrode BED through the ground air also has the same voltage as the charging/discharging capacitor. 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 discharge current It was confirmed that the electrical characteristics such as rise time and waveform distortion were significantly improved compared to the conventional ones, and the variation in the electrical characteristics between discharges was also extremely small.

In addition, instead of configuring the rod-shaped movable conductor SUP to be moved forward and backward by a feed screw mechanism, the rear end of the rod-shaped movable conductor SUP is fixedly attached to the front end of the cylindrical insulating support HOL, and the guide cylinder is
Insert into GUD and bowl-shaped support conductor BOW, insulated handle
The rod-shaped movable conductor SUP may be moved forward and backward by moving the HAN or the cylindrical insulating support HOL back and forth, and in this case, the guide tube GUD may be omitted.

Above, we have explained the case where the surface of the EUT under test is covered with the insulating layer INS _E , but the flange-like electrode
Since the BED part is covered with an insulating _layer , the surface of the EUT under test is not covered with an insulating layer.
Even when the conductor is directly exposed, a discharge test can be performed in the same manner as above.

[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, in which BOW...bowl-shaped support conductor, BED...flange-shaped electrode, GUD... Guide tube, KG...Keyway, INS _s ...
...insulating layer, SUP...rod-shaped movable conductor, KY...protrusion, SED...discharge electrode, HOL...cylindrical insulating support, HAN...insulating handle, DS...feeding screw,
EUT...Test object, INS _E ...Insulating layer, C _CD ...
Charge/discharge capacitor, R _D ……Discharge resistance, GAP……
This is the discharge gap.

Claims (1)

[Scope of utility model registration request] A flange-shaped electrode provided integrally around the periphery of the bowl-shaped support conductor and covered with an insulating layer, a rod-shaped movable conductor slidably supported by the bowl-shaped support conductor, and attached to the front end of the rod-shaped movable conductor. 1. An electrostatic discharge simulator comprising: a discharge electrode having a cylindrical shape; and a cylindrical insulating support body that supports the rear part of the rod-shaped movable conductor and houses a discharge resistor and a charge/discharge capacitor in its hollow interior.