KR20110135154A - Lighting emitting diode having function of wireless power driving and test method thereof - Google Patents

Abstract

PURPOSE: A light emitting diode wafer which includes a wireless power source driving function and a test method thereof are provided to test faults in a light emitting diode chip without using a probe card, thereby reducing probe card manufacturing costs. CONSTITUTION: A plurality of light emitting diode chips(10u) is arranged on a substrate and separated by a scribe line. A power receiver(32) receives wireless power from a power transmitter of a tester in order to supply power to a power source terminal of the multiple diode chips. The power receiving end creates a high frequency alternating current by receiving an electromagnetic wave or magnetic field. A power conversion part converts the high frequency alternating current into a direct current. A power saving and supplying part saves power generated by the direct current.

Description

Lighting emitting diode having function of wireless power driving and test method

The present invention relates to a light emitting diode and a test method thereof, and more particularly, to a light emitting diode wafer having a wireless power supply drive function and a test method thereof.

Light emitting diodes (LEDs) are used for various display devices and various light sources because they have excellent initial driving characteristics and shock resistance and excellent repetitive characteristics such as on / off lighting.

The light emitting diodes are manufactured by cutting a plurality of light emitting diode chips on a light emitting diode wafer, and then cutting and packaging them. The LED wafer performs a defective test by contacting a probe card of a tester (test device) for each LED chip at the wafer level.

Since LED chips vary in model, a separate probe card must be manufactured for each model. Probe cards also have the disadvantage of being expensive to manufacture.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light emitting diode wafer capable of performing a defective test of a light emitting diode chip wirelessly without using a probe card.

Another object of the present invention is to provide a test method of a light emitting diode wafer having a wireless power supply driving function.

In order to achieve the above object, the light emitting diode wafer according to an embodiment of the present invention is to receive a wireless power from the power source of the tester, a plurality of light emitting diode chips formed on the substrate and separated by a scribe line, And a power receiver capable of supplying power to power terminals of the plurality of light emitting diode chips.

The power receiver may be connected to a power terminal of one LED chip. The power receiver may be connected to power terminals of a plurality of LED chips.

The power receiver includes a power receiver configured to receive the electromagnetic wave or the magnetic field to generate a high frequency alternating current, a power converter to convert the high frequency alternating current into a direct current, and a power to store power generated by the direct current. It may comprise a storage and providing unit.

The power receiver may be formed at a portion without a pattern on a scribe line or the substrate.

The power receiver may be formed on the surface or the back of the substrate.

In order to achieve the above object, a test method of a light emitting diode wafer according to an embodiment of the present invention includes preparing a light emitting diode wafer having a power receiver. The power transmitter of the tester supplies wireless power to the power receiver of the light emitting diode wafer to supply power to a predetermined light emitting diode chip of the light emitting diode wafer. The quality of the light emitting diode chip is determined.

The power transmitter may include a high frequency power driver configured to generate a high frequency AC current, and a power transmitter configured to generate an electromagnetic wave or a magnetic field from the high frequency AC current.

The power transmitter and the power receiver may be aligned along a reference line in a direction perpendicular to the light emitting diode wafer. The power transmitter and the power receiver may include an antenna, a coil, or a resonator.

The light emitting diode wafer according to the embodiment of the present invention can test the defect of the light emitting diode chip without using a probe card. This can reduce the cost of manufacturing the probe card.

In addition, since the LED wafer according to the embodiment of the present invention tests the LED chip using wireless power, it is possible to increase the test reliability compared to the contact test using the probe card.

1 is a plan view of a light emitting diode wafer according to an embodiment of the present invention.
2 and 3 are views for explaining a method for performing a bad test of the light emitting diode wafer according to an embodiment of the present invention.
4 is a cross-sectional view illustrating a light emitting diode wafer including a light emitting diode chip according to another embodiment of the present invention.
5 is a block diagram illustrating a power transmitter of a tester according to an embodiment of the present invention.
6 is a block diagram illustrating a power receiver of a light emitting diode wafer according to an embodiment of the present invention.
7 is a view for explaining a test method of a light emitting diode chip according to an embodiment of the present invention.
8 is a view for explaining a test method of a light emitting diode chip according to another embodiment of the present invention.
9 is a detailed configuration diagram of the voltage drop means of FIG. 8.
10 is a flowchart illustrating a test method of the light emitting diode chip of FIGS. 8 and 9.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified into various other forms, It is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept to those skilled in the art.

In the following description, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Also, the phrases "comprising" and / or "comprising" as used herein do not specify the stated steps, actions, elements, elements, shapes, numbers, and / or presence of these groups, and one It is not intended to exclude the presence or addition of other steps, operations, members, elements, shapes, numbers, and / or groups thereof. In addition, "and / or" includes any and all combinations of one or more of the listed items.

Although the terms first, second, etc. are used herein to describe various members, regions, parts, means, and / or functions, these members, regions, parts, means, and / or functions are defined by these terms. It is obvious that not. These terms are intended to be used to distinguish one member, region, part, means or function from another member, region, part, means or function. Thus, the first member, region, portion, means or function described below may refer to the second member, region, portion, means or function without departing from the teachings of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings schematically showing embodiments of the present invention. Like numbers refer to like elements in the figures. Elements shown in the drawings are presented for convenience and clarity of description, and variations and modifications may be expected by the art. Accordingly, embodiments of the invention should not be construed as limited to the specific forms set forth herein.

1 is a plan view of a light emitting diode wafer according to an embodiment of the present invention.

Specifically, in the light emitting diode wafer 20 according to the present invention, a plurality of light emitting diode chips 10u separated by a scribe line 12 are formed on a substrate 10, and power is provided between the light emitting diode chips 10u. The receiving unit 32 is formed. The power receiver 32 is a portion that receives wireless power from a power transmitter of a tester for testing the quality of the light emitting diode chips 10u at the wafer level. The power receiver 32 is connected to a power supply terminal (not shown) of the LED chips 10u.

The power receiver 32 may be formed on the surface of the substrate 10. The power receiver 32 may be formed in the scribe line 12, and may be connected to a power supply terminal of one LED chip 10u or a power supply terminal of a plurality of LED chips 10u. The space where the power receiver 32 is formed may be the remaining space of the light emitting diode wafer 20 in which the scribe line 12 or the light emitting diode chip 10u is not formed. Although seven power receivers 32 are shown in this drawing, the scope of the present invention is not limited thereto. The power receiver 32 may be provided in plural in the substrate 10 as necessary.

2 and 3 are views for explaining a method for performing a bad test of the light emitting diode wafer according to an embodiment of the present invention.

Specifically, the light emitting diode wafer 20 according to the embodiment of the present invention is prepared. The light emitting diode wafer 20 has a plurality of light emitting diode chips 10u1 and 10u2 formed on the substrate 10, for example. Of course, a plurality of light emitting diode chips 10 are formed on the light emitting diode wafer 20 as described above, but only two are shown here for convenience.

The light emitting diode chips 10u1 and 10u2 may include an n-type semiconductor layer 120, an n-type semiconductor layer 120, an n-type cladding layer 130, an active layer 140, and a p-type cladding layer 150 on the substrate 10. ), a p-type semiconductor layer 160, a p-type power supply terminal 170, and an n-type power supply terminal 180. The light emitting diodes included in the light emitting diode chips 10u1 and 10u2 are semiconductor pn junction diodes. When the p-type semiconductor and the n-type semiconductor are bonded together and the voltage is applied, holes in the p-type semiconductor go toward the n-type semiconductor and are collected in the middle layer. In contrast, electrons in the n-type semiconductor move toward the p-type semiconductor and conduction band Gather in the middle floor, the lowest point of). These electrons naturally fall into the holes of the valence band, and at this point, they emit as much energy as the difference in height between the conduction band and the appliance band, that is, the energy gap, which is emitted in the form of light.

In the present embodiment, the light emitting diode chips 10u1 and 10u2 are n-type semiconductor layer 120, n-type cladding layer 130, active layer 140, p-type cladding layer 150, p on the substrate 10. The semiconductor semiconductor layer 160 is formed by sequentially stacking, exposing a predetermined region of the n-type semiconductor layer 120 through etching, and the n-type power supply terminal 180 on the exposed n-type semiconductor layer 120. The p-type power supply terminal 170 is formed on the p semiconductor layer 160. The n-type cladding layer 130 and the p-type cladding layer 150 effectively limit electrons and holes in the active layer 140 to increase the recombination efficiency of electrons and holes, which may be omitted in some cases. In addition, a buffer layer may be additionally formed on the substrate 10 to mitigate lattice mismatch.

On the light emitting diode wafer 20, a tester 40 capable of testing a defective product by applying power to the light emitting diode chips 10u1 and 10u2 in a non-contact manner is positioned. The power receiver 32 is provided on the upper surface (surface) or the rear surface of the substrate 10 of the light emitting diode wafer 20. The power receiver 32 is connected to the p-type power supply terminal 170 and the n-type power supply terminal 180 through electrical wiring. For example, the power receiver 32 may be connected to the p-type power terminal 170 and the n-type power terminal 180 through an electrical wiring or an electrical redistribution through a through hole formed in the substrate 10. The tester 40 may test the defect by applying power to the light emitting diode chips 10u1 and 10u2 formed on the light emitting diode wafer 20 in a non-contact manner.

The power receiver 32 receives the wireless power from the power transmitter 34 of the tester 40 as described above. The power transmitter 34 and the power receiver 32 may be arranged along a reference line in a direction perpendicular to the light emitting diode wafer 20. Shapes of the light emitting diode chips 10u1 and 10u2 may vary, but only one structure is illustrated in FIG. 2 for convenience. The power transmitter 40 included in the tester 40 and the power receiver 32 included in the light emitting diode wafer 20 will be described later in more detail.

4 is a cross-sectional view illustrating a light emitting diode wafer including a light emitting diode chip according to another embodiment of the present invention.

Specifically, the light emitting diode wafer 20a shown in FIG. 4 includes light emitting diode chips 10u1-1 and 10u2-1 as compared with FIG. As described above, the light emitting diode chips 10u1-1 and 10u2-1 are also semiconductor pn junction diodes. In the present embodiment, the light emitting diode chips 10u1-1 and 10u2-1 are formed by sequentially stacking an n-type semiconductor layer 120, an active layer 140, and a p-type semiconductor layer 160 on a substrate 10. It is.

An n-type power terminal 180 is formed on the n-type semiconductor layer 120, and the substrate 10 serves as a p-type power terminal. In this case, a defective test of the LED chips 10u1-1 and 10u2-1 formed on the LED wafer 20a may be performed by applying power through the power receiver 32 and the substrate 10. have. 3 and 4 illustrate examples of the light emitting diode chips 10u1, 10u2, 10u1-1, and 10u2-1, but the present invention is not limited thereto, and the present invention may be applied to light emitting diode chips having various structures.

Hereinafter, the reference number of the light emitting diode wafer is used as 20 for convenience. Of course, the light emitting diode wafer may include the light emitting diode wafers 20 and 20a as described above, and may have various structures.

5 is a block diagram illustrating a power transmitter of a tester according to an embodiment of the present invention, and FIG. 6 is a block diagram illustrating a power receiver of a light emitting diode wafer according to an embodiment of the present invention.

In detail, the power transmitter 34 and the power receiver 32 are wireless power units capable of wirelessly receiving or transmitting power. The wireless power supply unit is a radial method using radio frequency (RF) waves or ultrasonic waves, an inductive coupling method using magnetic induction, or a non-radiative method using magnetic field resonance. Power may be received and transmitted. The radial method may receive and transmit power energy wirelessly using an antenna such as a monopole or a planar inverted-F antenna (PIFA). In the radial method, radiation occurs while an electric field or a magnetic field changing with time affects each other, and when there is an antenna of the same frequency, power may be received and transmitted according to polarization characteristics of an incident wave. In the inductive coupling method, a coil is wound a plurality of times to generate a strong magnetic field in one direction, and a coil is generated by proximity of a coil that resonates within a similar range of frequencies, thereby receiving and transmitting power energy wirelessly. . The non-radioactive method can receive and transmit power energy wirelessly by using an evanescent wave coupling that moves an electromagnetic wave between two media resonating at the same frequency through a near field.

Referring to FIG. 5, the power transmitter 34 may include a power converter 34a, a high frequency power driver 34b, a power transmitter 34c, a power detector 34d, and a power controller 34e.

The power converter 34a may receive a power signal transmitted from the outside, for example, an AC signal or a DC signal. Accordingly, the power converter 34a may convert the received AC power into a DC current, or convert the received DC power into a desired AC current. Subsequently, the power converter 34a may provide operating power to the high frequency power driver 34b and the power controller 34e. The power converter 34a may include a voltage limiting circuit (not shown) and a rectifier circuit (not shown). In addition, the power converter 34a is optional and may be omitted in some cases.

The high frequency power driver 34b may be driven according to the received operating power source to generate AC power, for example, high frequency power. For example, the high frequency power driver 34b may include a switching mode power supply (SMPS) that generates the high frequency AC current through a high speed switching operation. Subsequently, the high frequency power generated by the high frequency power driver 34b may be wirelessly provided to the outside through the power transmitter 34c.

The power detector 34d continuously measures a power value supplied from the high frequency power driver 34b to the power transmitter 34c, for example, a voltage value and a current value, and outputs information about the voltage value and the current value. It transfers to the control part 34e. For example, the power detector 34d may be a circuit including a resistance element capable of directly measuring the voltage value and the current value.

The power controller 34e may drive as a microprocessor that controls the overall operation of the power transmitter 32. The power control unit 34e may be operated by the DC current transmitted by the power converter 34a. The power controller 34e may receive the voltage value and the current value transmitted from the power detector 34d and control the driving of the power converter 34a accordingly. In addition, the power controller 34e controls the high frequency power driver 34b to modulate the width, amplitude, frequency, number of pulses, and the like of the generated high frequency power pulses. can do. Through the above pulse width modulation (PWM), pulse amplitude modulation (PAM), pulse frequency modulation (PFM), pulse number modulation (PNM) The controller 34e may adjust the power of the high frequency AC current.

The power transmitter 34c may be configured to receive a high frequency AC current from the high frequency power driver 34b and wirelessly transmit power to an external device.

In the case where the wireless power transfer method is the above-described radial method, that is, when the wireless power supply unit uses radio frequency waves or ultrasonic waves, the power transmission end 34c of the wireless power supply unit is a monopole or a planar inverted-F antenna. It may include an antenna such as). The antenna generates an electromagnetic wave according to a high frequency current, and a receiving antenna such as an external element to receive the generated power may generate the high frequency power from the electromagnetic wave by receiving the electromagnetic wave.

In the case of the inductive coupling scheme described above, that is, when the wireless power unit uses magnetic induction, the power transmitter 34c of the wireless power unit may include a coil. According to the electromagnetic induction principle, when a high frequency current is applied to the power transmitting end 34c, the coil generates a magnetic field, and a receiving coil such as an external element to receive the generated power generates a high frequency current from the magnetic field.

In the case where the wireless power transfer method is the non-radiative method described above, that is, when the wireless power supply unit uses magnetic field resonance, the power transmitter 34c may include a resonator that generates an evanescent wave. have. The attenuation wave produces a steel plate field at close range and the intensity decreases exponentially as the distance increases. The resonator of the power transmitter 34c may resonate at the same frequency as a reception resonator such as an external device to receive the generated power, and in this case, a short range electromagnetic field may be formed between the two resonators. When a high frequency current is applied to the power transmitter 34c, the resonator generates an attenuation wave, and the attenuation wave may wirelessly transmit power through the near field.

Referring to FIG. 6, the power receiver 32 may include a power receiver 32a, a power converter 32b, a power storage / provider 32c, a power detector 32d, and a power controller 32e. have.

The power receiver 32a receives an external power signal wirelessly or by wire, and transmits it to the power converter 32b. When the power receiver 32a wirelessly receives the external power, the power receiver 32a may include an antenna, a coil, or a resonator, and the external power signal may be an AC signal. In this case, the external power signal can be received by the radial method, the inductive coupling method, or the non-radial method described above. If necessary, the power receiving end 32a may be configured to convert the external power signal into a high frequency alternating current.

The power converter 32b may convert a power signal received from the power receiver 32a, for example, an AC signal, into a DC signal. The power converter 32b may include a voltage limiting circuit (not shown) and a rectifier circuit (not shown). The voltage limiting circuit may function to prevent the AC signal from being excessively supplied. The rectifier circuit may rectify the AC signal into a DC current. When the direct current signal is transmitted from the power receiver 32a, the power converter 32b may be omitted or may function to convert the direct current signal to a predetermined voltage. Subsequently, the DC signal converted by the power converter 32b may be transferred to the power storage / provider 32c.

The power storage / provider 32c may include a power storage element such as a capacitor, and may store the DC signal transmitted to the power converter 32b. In addition, power, for example, a test current, may be provided to the LED wafer 20 through the DC signal, that is, power. The power storage / provider 32c may be omitted as an optional component, in which case it is possible to provide power, such as a test current, to the light emitting diode wafer 20 directly from the power converter 32b.

The power detector 32d continuously measures a power value, for example, a voltage value and a current value, supplied from the power converter 32d to the power storage / provider 32c, and relates to the voltage value and the current value. Information is transmitted to the power control unit 32e. For example, the power detector 32d may be a circuit including a resistance element capable of directly measuring the voltage value and the current value.

The power controller 32e may be a microprocessor that controls the overall operation of the power receiver 32. The power controller 32e may be operated by the direct current delivered by the power converter 32b. The power controller 32e may receive the voltage value and the current value transmitted from the power detector 32d and control the driving of the power converter 32b accordingly. For example, the power control unit 32e compares the voltage value and the current value measured and transmitted by the power detection unit 32d with a predetermined reference voltage value and a reference current value, and thus the power converter 32b and the power. The driving of the power converter 32b may be controlled so that the overvoltage or overcurrent of the storage / provider 32c does not occur.

7 is a view for explaining a test method of a light emitting diode chip according to an embodiment of the present invention.

Specifically, the test method of the LED chip according to the embodiment of the present invention prepares the LED wafer 20 as described above. Subsequently, the power supply unit 201 of the tester 40 supplies power to the light emitting diode 205 of the light emitting diode wafer 20 to emit light of the light emitting diode 205. When the power supply 201 of the tester 40 supplies power to the light emitting diode 205 of the light emitting diode wafer 20, the wireless power is supplied using the wireless power supply, that is, the power supply and the power receiver, as described above.

The test method of the LED chip according to the embodiment of the present invention includes a voltage drop checking means 203 to check the voltage drop of the power supplied to the LED 205. That is, if the voltage drop of the power supplied to the light emitting diode 205 is higher than or equal to a certain level, it is determined to be normal (good quality).

8 is a view for explaining a test method of a light emitting diode chip according to another embodiment of the present invention, Figure 9 is a detailed configuration diagram of the voltage drop means of FIG.

Specifically, the test method of the LED chip according to another embodiment of the present invention prepares the LED wafer 20 as described above. The tester 40 includes a power supply unit 301, a voltage stabilizer 303, a voltage drop checking unit 305, and a driving controller 307. The voltage stabilizer 303 outputs the voltage supplied from the power supply unit 301 to a voltage required for light emission of the light emitting diode 309 of the light emitting diode wafer 20.

The driving controller 307 receives the voltage output from the voltage stabilizer 202 and selectively controls the operation of the light emitting diode 309. The driving controller 307 controls the test current output from the voltage drop checking means 305. The voltage drop checking means 305 serves to supply a test current for checking the voltage drop of the light emitting diode 309 to the light emitting diode 309 under the control of the driving controller 307.

In the present invention, when the voltage drop means 305 of the tester 40 supplies power to the light emitting diode 309 of the light emitting diode wafer 20, as described above, the wireless power source is used, that is, the power supply unit and the power receiving unit. To supply.

The voltage drop checking means 203 is composed of a switching means 311 and a plurality of test current supply means 313 for supplying a predetermined test current. The switching means 311 is switched to any one of the plurality of test current supply means 313 so that the test current of the corresponding test current supply means 313 is supplied. The test currents supplied by the plurality of test current supply means 313 are different from each other. As an example of various test currents, the test current may be configured to 10 kHz, 50 kHz, 100 kHz, 200 ㎂, 300 ㎂, 400 ㎂, 500 ㎂.

10 is a flowchart illustrating a test method of the light emitting diode chip of FIGS. 8 and 9.

Specifically, when power is supplied from the power supply unit 301 of the tester 40 to the voltage stabilizer 303, the voltage stabilizer 303 converts and outputs the corresponding power to a voltage necessary for light emission of the light emitting diode 309 (S401). , S402). Subsequently, the driving controller 307 receives the voltage output from the voltage stabilizer 303 and supplies the voltage to the light emitting diode 309 to emit light.

While the predetermined voltage is supplied to the light emitting diode 309, the voltage drop checking means 305 supplies a predetermined test current to the light emitting diode 309 under the control of the driving controller 307 (S403). At this time, the test current supplied from the voltage drop checking means 305 is a plurality of test currents having various amounts of current. The plurality of test currents set in the voltage drop checking means 305 are supplied to the light emitting diode 309 in the order of the smallest amount of current. For example, the first, second, third ... n-th test currents having current amounts of 10 kV, 50 kV, 100 kV, 200 kV, 300 kV, 400 kV, 500 kV can be supplied sequentially. There is (S404).

A plurality of test currents having various amounts of current as described above are supplied to the light emitting diode 309. All of the above test currents, i.e., the first, second, third ... The nth test current is not supplied to the light emitting diode 309. For example, after the first test current having a current amount of 10 mA is supplied to the light emitting diode 309, if the voltage drop of the light emitting diode 309 is equal to or more than a predetermined reference, for example, 2 V or more, the corresponding light emitting diode 309 is provided. Is determined to be normal (good quality) to maintain the voltage supply for light emission.

On the other hand, if the voltage drop of 2V or less is checked as a result of the first test current supply, the second test current of 50 mA, for example, 50 mA is supplied to the light emitting diode 309 to check the voltage drop. If the voltage drop after the second test current is greater than or equal to a predetermined reference, it is determined to be normal. If the voltage drop less than or equal to the predetermined reference is checked, the third test current is supplied. In this way, the first, second, third ... n-th test currents set in the voltage drop checking means 305 check whether the corresponding light emitting diode 309 is defective.

In order to clearly understand the present invention, the shape of each part of the accompanying drawings should be understood as illustrative. It should be noted that the present invention may be modified in various shapes other than the illustrated shape. Like numbers described in the figures refer to like elements.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Will be clear to those who have knowledge of.

Claims (10)

Board;
A plurality of light emitting diode chips formed on the substrate and separated by scribe lines; And
And a power receiver configured to receive wireless power from a power transmitter of a tester to supply power to power terminals of the plurality of LED chips. The light emitting diode wafer of claim 1, wherein the power receiver is connected to a power terminal of one light emitting diode chip. The light emitting diode wafer of claim 1, wherein the power receiver is connected to a power terminal of the plurality of light emitting diode chips. The power receiver of claim 1, wherein the power receiver comprises: a power receiver configured to receive the electromagnetic wave or the magnetic field to generate a high frequency alternating current;
A power converter converting the high frequency alternating current into a direct current; And
The light emitting diode wafer comprising a power storage and providing unit for storing the power generated by the direct current. The light emitting diode wafer of claim 1, wherein the power receiver is formed at a portion without a scribe line or a pattern on the substrate. The light emitting diode wafer of claim 1, wherein the power receiver is formed on a surface or a rear surface of the substrate. Preparing a light emitting diode wafer having a power receiver;
Supplying wireless power from a power transmitter of a tester to a power receiver of the light emitting diode wafer to supply power to a predetermined light emitting diode chip of the light emitting diode wafer;
And determining the quality of the light emitting diode chip. 8. The apparatus of claim 7, wherein the power transmitter comprises: a high frequency power driver configured to generate a high frequency alternating current; And
And a power transmitter configured to generate an electromagnetic wave or a magnetic field from the high frequency alternating current. The test method of claim 7, wherein the power transmitter and the power receiver are aligned along a reference line in a direction perpendicular to the light emitting diode wafer. The test method of claim 7, wherein the power transmitter and the power receiver comprise an antenna, a coil, or a resonator.

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