JP2008003014A - Ultrasonic inspection method and ultrasonic inspection apparatus - Google Patents

Abstract

An object of the present invention is to provide an ultrasonic inspection method capable of quickly setting a focal position of an ultrasonic transducer to a target position without being an expert.
Since the upper surface of the position reference object 8 arranged under the inspection object 2 can be identified and the transmission / reception focal point of the ultrasonic transducer 5 can be matched with the inspection position inside the inspection object 2, The focal position of the ultrasonic transducer 5 can be quickly set as the target position.
[Selection] Figure 1

Description

  The present invention relates to a nondestructive inspection inside an inspection target by ultrasonic waves.

  As shown in FIG. 13 (b), when ultrasonically inspecting the inside of the semiconductor integrated circuit element 2 mounted on the substrate 1, the substrate 1 is set in the medium tank 4 containing the ultrasonic transmission medium 3, An ultrasonic wave is transmitted from the ultrasonic transducer 5 toward the semiconductor integrated circuit element 2, a reflected wave reflected inside the semiconductor integrated circuit element 2 is received by the ultrasonic transducer 5, and the ultrasonic transducer 5 is horizontally scanned. (X-axis direction) and inspected from the received signal at each scanning position. 6 is a spacer.

  More specifically, this inspection method is used for inspection of peeling of die bonding located near the lower layer of the semiconductor integrated circuit element 2. In this case, since it is necessary to perform horizontal scanning by precisely focusing the ultrasonic transducer 5 on the layer where the die bonding exists, the ultrasonic transducer 5 is moved up and down (in the Z-axis direction) to perform supersonic scanning. The focus of the sound wave vibrator 5 is set in advance.

  In setting the focus of the ultrasonic transducer 5, the semiconductor integrated circuit element 2 is set in the medium tank 4 via the spacer 7 as shown in FIG. The height of the spacer 7 is, for example, such that the height of the ultrasonic transducer 5 is the same as that of the semiconductor integrated circuit element 2 mounted on the substrate 1 in FIG.

In this state, the reflected wave is received while bringing the ultrasonic transducer 5 close to the semiconductor integrated circuit element 2, and the focal position of the ultrasonic transducer 5 from time to time is compared with the known laminated structure of the semiconductor integrated circuit element 2. And the focal position of the ultrasonic transducer 5 is adjusted to the position of the lower surface of the semiconductor integrated circuit element 2. The height of the ultrasonic transducer 5 at that time is V1. Here, when the distance between the known laminated structure of the semiconductor integrated circuit element 2 and the lower surface of the semiconductor integrated circuit element 2 and the layer where the die bonding to be inspected exists is V2, the ultrasonic vibrator 5 Is raised by a distance V2, and the height of the ultrasonic transducer 5 is set to (V1-V2). Then, the ultrasonic transducer 5 is horizontally scanned to confirm the die bonding layer.
Japanese Patent Laid-Open No. 4-95873

  However, the setting operation for adjusting the focal position of the ultrasonic transducer 5 to the position of the lower surface of the semiconductor integrated circuit element 2 as described above requires skill. In the case of an inexperienced measurer, even if the actual focal position of the ultrasonic transducer 5 passes through the lower surface of the semiconductor integrated circuit element 2, the detection of the lower surface of the semiconductor integrated circuit element 2 is continued without being noticed. The current situation is that it takes a long time to start the inspection.

  An object of the present invention is to provide an ultrasonic inspection method capable of quickly setting a focal position of an ultrasonic transducer to a target position without being an expert.

  In the ultrasonic inspection method according to claim 1 of the present invention, an ultrasonic wave is transmitted from an ultrasonic transducer toward an inspection target, and a reflected wave reflected inside the inspection target is received by the ultrasonic transducer. When inspecting the inside of an object, an inspection object is arranged on a position reference object on which a plane pattern having different acoustic impedance to ultrasonic waves is recorded in an adjacent section, and the ultrasonic transducer passes through the inspection object to Ultrasonic waves are transmitted and received toward the position reference object, and the ultrasonic transducer is horizontally scanned in a direction passing through the adjacent section of the position reference object, and the ultrasonic transducer is received by the horizontal scanning. It is determined whether the signal is a plane pattern of the position reference object, and the ultrasonic transducer and the position reference object are moved relative to each other until the reflection signal from the plane pattern of the position reference object is received. The distance between the child and the position reference object is changed, and horizontal scanning of the ultrasonic transducer is repeated in the direction passing through the adjacent section of the position reference object, and the reflected signal from the plane pattern of the position reference object is obtained. Upon reception, the ultrasonic transducer and the position reference object are moved relative to each other, and the transmission / reception focal point of the ultrasonic transducer coincides with the upper surface of the position reference object from the change in the reception signal of the ultrasonic transducer. The relative position between the ultrasonic vibrator and the position reference object is specified, and the ultrasonic vibrator and the position are determined from the specified position by a known distance between the inspection layer inside the inspection target and the upper surface of the position reference object. The reference object is relatively moved so that the transmission / reception focal points of the ultrasonic transducers coincide with the inspection position inside the inspection object.

  The ultrasonic inspection method according to a second aspect of the present invention is characterized in that, in the first aspect, the position reference object is provided with irregularities so that the acoustic impedance to the ultrasonic wave differs between adjacent sections.

  The ultrasonic inspection method according to claim 3 of the present invention is the ultrasonic inspection method according to claim 1, wherein the position reference object is formed of a material having a different elastic coefficient so that an acoustic impedance to the ultrasonic wave is different between adjacent sections. Features.

  The ultrasonic inspection method according to a fourth aspect of the present invention is the ultrasonic inspection method according to the second aspect, wherein the planar pattern is detected from a delay time difference of a received signal at a position where the ultrasonic transducer is horizontally scanned. .

  The ultrasonic inspection method according to claim 5 of the present invention is the ultrasonic inspection method according to claim 3, wherein the planar pattern is detected from a difference in received signal intensity at a position where the ultrasonic transducer is horizontally scanned. .

  An ultrasonic inspection apparatus according to a sixth aspect of the present invention is an ultrasonic inspection apparatus that sets a focal position of transmission / reception of an ultrasonic transducer to a specific position inside an inspection object, and for ultrasonic waves between adjacent sections. A plane pattern having different acoustic impedance is recorded, and a position reference object disposed on the opposite side of the ultrasonic transducer with an inspection object interposed therebetween, and known information such as the shape of the position reference object are programmed to store the super pattern. A control device that calculates the amount of movement of the ultrasonic transducer by using a transmission / reception signal of the ultrasonic transducer as an input signal, a first actuator that drives the ultrasonic transducer in the Z-axis direction by an output of the control device, A second actuator that drives the ultrasonic transducer in the X-axis direction or the Y-direction according to the output of the control device, and the control device is moved from the ultrasonic transducer to the position through the inspection object. An ultrasonic wave is transmitted and received toward the reference object, and the ultrasonic transducer is horizontally scanned in a direction passing through the adjacent section in the position reference object, and the received signal of the ultrasonic transducer is scanned by the horizontal scan. Is a plane pattern of the position reference object, and until the reflected signal from the plane pattern of the position reference object is received, the ultrasonic vibrator and the position reference object are relatively moved to When the distance of the position reference object is changed and the ultrasonic transducer is horizontally scanned repeatedly in a direction passing through the adjacent section of the position reference object, and when the reflected signal from the planar pattern of the position reference object is received, The ultrasonic transducer and the position reference object are relatively moved to change the reception signal of the ultrasonic vibrator so that the transmission / reception focal point of the ultrasonic vibrator coincides with the upper surface of the position reference object. The relative position between the ultrasonic transducer and the position reference object is specified, and from the specified position by a known distance between the inspection layer inside the inspection target and the upper surface of the position reference object, the ultrasonic vibrator and The position reference object is relatively moved so that the transmission / reception focal points of the ultrasonic transducers coincide with the inspection positions inside the inspection object.

  According to this configuration, it is possible to identify the upper surface of the position reference object arranged under the inspection target, and to make the transmission / reception focal point of the ultrasonic transducer coincide with the inspection position inside the inspection target. The focal position of the sonic transducer can be quickly set to the target position.

Embodiments of the present invention will be described below with reference to FIGS.
(Embodiment 1)
1 to 6 show (Embodiment 1) of the present invention.

FIG. 1A shows a process of setting the focal point of the ultrasonic transducer 5 to the die bonding layer inside the semiconductor integrated circuit element 2 as an inspection target.
First, the position reference object 8 is set in the medium tank 4 containing the ultrasonic transmission medium 3, and the semiconductor integrated circuit element 2 is set thereon via the spacer 9. In this example, a case of a BGA (Ball Grid Array) package in which the ball electrode 10 is provided on the back surface of the semiconductor integrated circuit element 2 is shown. The ultrasonic vibrator 5 having a resonance frequency of 100 MHz is used.

  As shown in FIG. 2, the position reference object 8 is recorded with a planar pattern of the concave portion 11 and the convex portion 12 so that the acoustic impedance to the ultrasonic wave differs between adjacent sections. When the planar shape of the semiconductor integrated circuit element 2 is about 10 mm × 10 mm, a shape in which the concave portion 11 and the convex portion 12 are repeated in the X-axis direction at a pitch of 0.5 mm is used here.

FIG. 3 shows a process for setting the focal point of the ultrasonic transducer 5 to the die bonding layer.
In step S1, the ultrasonic transducer 5 is lowered by one unit (for example, 0.1 mm) defined toward the semiconductor integrated circuit element 2. In step S2, an ultrasonic wave is transmitted from the ultrasonic transducer 5 to the semiconductor integrated circuit element 2 via the ultrasonic transmission medium 3 and a reflected wave is received, and the ultrasonic transducer 5 is moved in the horizontal direction (X-axis). In the direction), the ultrasonic waves are repeatedly transmitted and received while scanning at a distance of at least 2 mm at a constant speed.

  At this time, in step S3, it is determined whether the change in the delay time of the received signal is a specific pattern. Specifically, until the focal point of the ultrasonic transducer 5 reaches the position reference object 8, even if horizontal scanning is performed in step S 2, the change in the delay time of the received signal at that time is the internal structure of the semiconductor integrated circuit element 2. And there is very little possibility of matching with the specific pattern. Therefore, the routine from step S1 to step S3 is repeatedly executed.

  When the focal point of the ultrasonic transducer 5 reaches the position reference object 8, the change in the delay time of the received signal is caused by the horizontal scanning when the scanning speed is constant and the concave portion 11 and the convex portion 12 of the position reference object 8. It is a specific pattern determined by the planar pattern. FIG. 4 shows this example.

  The ultrasonic wave reflected by the convex part 12 of the position reference object 8 is received by the ultrasonic transducer 5 with a delay time T1, whereas the ultrasonic wave reflected by the bottom of the concave part 11 of the position reference object 8 is delayed. The ultrasonic transducer 5 receives the signal at time T1 + t. Accordingly, when the length of the delay time T1 and the length of the delay time T1 + t are the same, it is determined that the specific pattern has been obtained, the routine of steps S1 to S3 is exited, and step S4 is executed.

  When the ultrasonic frequency is 100 MHz and the ultrasonic transmission medium 3 is water, since one ultrasonic pulse has a width of about 10 nsec, the time difference between the concave portion 11 and the convex portion 12 may be 10 nsec or more. The depth of the corresponding recess 11 may be 0.740 μm (when the sound speed of water is 1480 m / s) or more.

  From the known laminated structure of the semiconductor integrated circuit element 2, the distance between the lower surface of the semiconductor integrated circuit element 2 and the layer where the die bonding to be inspected exists is V2, and the height of the spacer 9 is V3. If so, in step S4, the ultrasonic transducer 5 is set to a height raised by a distance (V2 + V3).

  In the flowchart shown in FIG. 3, as shown in FIG. 6, the ultrasonic vibration is generated by using the control device 13 whose main part is a microcomputer in which known information such as the shape of the position reference object 8 is programmed. Using the transmission / reception signal 14 of the child 5 as an input signal, the first actuator 15 that moves the ultrasonic transducer 5 in the Z-axis direction and the second actuator 16 that moves the ultrasonic transducer 5 in the X-axis direction are operated. By controlling, the height setting of the ultrasonic transducer 5 can be automatically controlled.

  After setting the height of the ultrasonic transducer 5 in this way, the substrate 1 on which the semiconductor integrated circuit element 2 is mounted is set on the spacer 17 as shown in FIG. The ultrasonic transducer 5 is horizontally scanned in the X-axis direction and the Y-axis direction to inspect whether the die bonding layer is peeled off. The height of the spacer 17 is such that the height of the semiconductor integrated circuit element 2 mounted on the substrate 1 is the same as that of the semiconductor integrated circuit element 2 in FIG.

  In this way, by specifying the upper surface of the position reference object 8 arranged under the semiconductor integrated circuit element 2 and making the transmission / reception focal point of the ultrasonic transducer coincide with the inspection position inside the semiconductor integrated circuit element 2 Even the inexperienced measurer can quickly set the focal position of the ultrasonic transducer 5 to the target position.

(Embodiment 2)
FIG. 7 shows (Embodiment 2) of the present invention.
In (Embodiment 1), as the position reference object 8, the concave portion 11 and the convex portion 12 are repeatedly configured at a predetermined pitch in the X-axis direction, and the concave portion 11 or the convex portion 12 is continuous in the Y-axis direction. 7, the concave and convex portions are repeatedly recorded at a predetermined pitch not only in the X-axis direction but also in the Y-axis direction, and in plan view, the position reference object 8 shown in FIG. Concave portions 18 having vertical and horizontal dimensions equal to the predetermined pitch are formed at the intersections of the Y-axis coordinates. Others are the same as (Embodiment 1).

  Thus, by using the position reference object 8 in which the recesses 18 are formed at a predetermined pitch in the X-axis direction and the Y-axis direction, the horizontal scanning in step S2 in FIG. In any of the Y-axis directions shown, the focal position of the ultrasonic transducer 5 can be quickly set to the target position. When horizontal scanning is performed in the Y-axis direction in step S2 in FIG. 3, the ultrasonic transducer 5 is driven in the Y-axis direction by the second actuator 16 illustrated in FIG.

(Embodiment 3)
FIG. 8 shows (Embodiment 3) of the present invention.
In (Embodiment 1), as the position reference object 8, the concave portion 11 and the convex portion 12 are repeatedly configured at a predetermined pitch in the X-axis direction, and the concave portion 11 or the convex portion 12 is continuous in the Y-axis direction. In the position reference object 8 shown in FIG. 8, not only the X-axis direction but also the Y-axis direction has concave and convex portions repeatedly recorded at a predetermined pitch. The rows of concavities and convexities adjacent to each other in the X-axis direction and the Y-axis direction are formed so that the phases are different by 90 degrees so that the protrusions 21 are located on both sides in the axial direction. Others are the same as (Embodiment 1).

  By using the position reference object 8 formed in this way, the horizontal scanning in step S2 in FIG. 3 is performed in either the X direction indicated by reference numeral 19 or the Y axis direction indicated by reference numeral 20. The focal position can be quickly set to the target position. When horizontal scanning is performed in the Y-axis direction in step S2 in FIG. 3, the ultrasonic transducer 5 is driven in the Y-axis direction by the second actuator 16 illustrated in FIG.

(Embodiment 4)
9 and 10 show (Embodiment 4) of the present invention.
In the first embodiment, as the position reference object 8, the recesses 11 and the protrusions 12 are repeatedly configured at a predetermined pitch in the X-axis direction, and the shape of the recess 11 extends vertically downward from the upper surface of the position reference object 8. Although the concave portion 11 of the position reference object 8 shown in FIG. 9 is formed by a V-shaped groove extending in the Y-axis direction.

  When this position reference object 8 is used, the ultrasonic wave US1 that has collided with the upper surface of the position reference object 8 is received by the ultrasonic transducer 5 via the semiconductor integrated circuit element 2 as shown in FIG. However, since the reflected wave of the ultrasonic wave US2 that has entered the V-shaped concave portion 11 is reflected by the inclined side of the concave portion 11 and travels outside the directivity range of the ultrasonic transducer 5, the signal of the received signal As shown in FIG. 10B, the level is LV2, which is extremely lower than the signal level LV1 of the ultrasonic wave UV1.

  In step S3 of (Embodiment 1), it is determined whether or not the change in the reception signal transmission time when performing horizontal scanning in step S2 is a specific pattern. In this (Embodiment 4), horizontal scanning is performed in step S2. In step S3, it is determined whether the change in the received signal level of the received signal is a specific pattern. Specifically, every time the scanning of 1 pitch 1P constituted by the concave portion 11 and the convex portion 12 is advanced in the X-axis direction, whether the level of the received signal is repeatedly generated at the same cycle with the high level LV1 and the low level LV2. Is determined in step S3. Others are the same as (Embodiment 1).

(Embodiment 5)
FIG. 11 shows (Embodiment 5) of the present invention.
In the position reference object 8 of (Embodiment 4), the concave portion 11 or the convex portion 12 is continuous in the Y-axis direction. However, the position reference object 8 shown in FIG. Also in the direction, concave and convex portions are repeatedly recorded at a predetermined pitch. Others are the same as (Embodiment 4).

  By using the position reference object 8 formed in this way, the horizontal scanning in step S2 in FIG. 3 is performed in either the X direction indicated by reference numeral 19 or the Y axis direction indicated by reference numeral 20. The focal position can be quickly set to the target position. When horizontal scanning is performed in the Y-axis direction in step S2 in FIG. 3, the ultrasonic transducer 5 is driven in the Y-axis direction by the second actuator 16 illustrated in FIG.

  Examples of the material of the position reference object 8 in each of the above embodiments include materials having a large acoustic impedance in the ultrasonic waves, such as SUS, aluminum, copper, and glass.

(Embodiment 6)
FIG. 12 shows (Embodiment 6) of the present invention.
In the position reference object 8 in each of the above embodiments, the concave portions 11 and the convex portions 12 are formed at a predetermined pitch so that the acoustic impedance differs between adjacent sections. However, the position reference object 8 shown in FIG. Is flat, and the upper surface is formed of a material having a different elastic coefficient at a constant pitch so that the acoustic impedance to the ultrasonic wave differs between adjacent sections.

  For example, a block made of a material having a large acoustic impedance having the recess 11 and the projection 12 shown in FIG. 2 is formed, and the recess 11 of this block is filled with a material having a small acoustic impedance, such as silicon rubber 22. it can.

  When the position reference object 8 of (Embodiment 6) is used, the change in the received signal level of the received signal at the time of horizontal scanning in step S2 of FIG. 3 is the same as in the case of (Embodiment 4). In step S3, it is determined whether the pattern is a specific pattern. Others are the same as (Embodiment 1).

Similarly, the concave portion 18 shown in FIG. 7 or FIG. 8 can be configured by filling the position reference object 8 with a material having a small acoustic impedance to ultrasonic waves, such as silicon rubber.
In each of the above-described embodiments, the position reference object 8 is set to the fixed side, and the ultrasonic transducer 5 is driven in the X-axis direction, the Y-axis direction, and the Z-axis direction. When the position reference object 8 is driven in the X-axis direction, the Y-axis direction, and the Z-axis direction on the fixed side, or the distance between the ultrasonic transducer 5 and the position reference object 8 is reduced, When the reference object 8 is raised and the ultrasonic vibrator 5 is lowered, or when the interval between the ultrasonic vibrator 5 and the position reference object 8 is increased, the position reference object 8 is lowered and the ultrasonic vibrator 5 is raised. In the case of horizontal scanning, the ultrasonic transducer 5 can be moved in the direction opposite to the position reference object 8, and in any case, the ultrasonic transducer 5 and the position reference object 8 are moved to X. It can be said that execution is performed with relative movement in the axial direction, the Y-axis direction, and the Z-axis direction.

  In each of the embodiments described above, the package of the semiconductor integrated circuit element 2 to be inspected is a BGA, and the influence of the error in the height of the ball electrode 10 provided on the back surface of the semiconductor integrated circuit element 2 is avoided. Although the spacer 9 is used as an object, when the package is an LGA (Land Grid Array) or the like, it can be similarly implemented even if it is arranged directly on the position reference object 8 and executed.

  According to the present invention, it is possible to quickly realize quality inspection of a mounted wiring board, and to contribute to improving the quality of various electronic devices.

Process drawing of ultrasonic inspection method of (Embodiment 1) of the present invention Partially enlarged perspective view of a position reference object used in the embodiment The flowchart figure of the control apparatus in the ultrasonic inspection apparatus used in the embodiment Explanatory drawing of step S2 and step S3 Explanatory drawing of step S4 Configuration diagram of ultrasonic inspection equipment Partial enlarged perspective view of a position reference object used in (Embodiment 2) of the present invention Partial enlarged perspective view of a position reference object used in (Embodiment 3) of the present invention Partial enlarged perspective view of a position reference object used in (Embodiment 4) of the present invention Explanatory drawing of step S2 and step S3 of the same embodiment Partially enlarged perspective view of a position reference object used in (Embodiment 5) of the present invention Partial enlarged perspective view of a position reference object used in (Embodiment 6) of the present invention Process diagram of conventional ultrasonic inspection method

Explanation of symbols

2 Semiconductor integrated circuit elements (inspected)
DESCRIPTION OF SYMBOLS 3 Ultrasonic transmission medium 4 Medium tank 5 Ultrasonic vibrator 8 Position reference | standard object 9 Spacer 11 Concave part 12 Convex part 13 Control apparatus 14 Transmission / reception signal 15 of the ultrasonic vibrator 5 1st actuator 16 2nd actuator 17 Spacer 18 Concave part 21 Projection 22 Silicon rubber (material with low acoustic impedance)

Claims (6)

When inspecting the inside of the inspection object by transmitting ultrasonic waves from the ultrasonic vibrator toward the inspection object, receiving the reflected wave reflected inside the inspection object by the ultrasonic vibrator,
An inspection object is placed on a position reference object in which a plane pattern in which the acoustic impedance to ultrasonic waves differs between adjacent sections is recorded,
The ultrasonic transducer transmits and receives an ultrasonic wave toward the position reference object via the inspection object, and horizontally scans the ultrasonic transducer in a direction passing through the adjacent section of the position reference object. ,
It is determined whether the reception signal of the ultrasonic transducer is a plane pattern of the position reference object by the horizontal scanning, and the ultrasonic transducer and the position reference object are received until a reflection signal from the plane pattern of the position reference object is received. Repeatedly moving the ultrasonic transducer horizontally in a direction passing through the adjacent section of the position reference object by changing the distance between the ultrasonic vibrator and the position reference object by relatively moving
When a reflected signal from the planar pattern of the position reference object is received, the ultrasonic transducer and the position reference object are moved relative to each other to change the received signal of the ultrasonic vibrator, and the transmission / reception focus of the ultrasonic vibrator Specifies the relative position of the ultrasonic transducer and the position reference object that coincide with the upper surface of the position reference object,
The ultrasonic transducer and the position reference object are relatively moved from the specified position by a known distance between the inspection layer inside the inspection target and the upper surface of the position reference object, and transmission / reception of the ultrasonic transducer is performed. An ultrasonic inspection method in which a focal point coincides with an inspection position inside the inspection object. The ultrasonic inspection method according to claim 1, wherein the position reference object is formed with unevenness so that acoustic impedance to the ultrasonic wave differs between adjacent sections. The ultrasonic inspection method according to claim 1, wherein the position reference object is formed of a material having a different elastic coefficient so that an acoustic impedance to the ultrasonic wave differs between adjacent sections. The ultrasonic inspection method according to claim 2, wherein the planar pattern is detected from a delay time difference of a received signal at a position where the ultrasonic transducer is horizontally scanned. The ultrasonic inspection method according to claim 3, wherein the planar pattern is detected from a difference in received signal intensity at a position where the ultrasonic transducer is horizontally scanned. An ultrasonic inspection apparatus that sets a focal position of transmission / reception of an ultrasonic transducer to a specific position inside an inspection object,
A position reference object disposed on the opposite side of the ultrasonic transducer with a plane pattern in which the acoustic impedance to the ultrasonic wave is different between adjacent sections recorded and inspected,
A controller for calculating known amounts of information such as the shape of the position reference object and calculating the amount of movement of the ultrasonic transducer using a transmission / reception signal of the ultrasonic transducer as an input signal;
A first actuator for driving the ultrasonic transducer in the Z-axis direction by an output of the control device;
A second actuator for driving the ultrasonic transducer in the X-axis direction or the Y-direction according to the output of the control device, and the control device,
The ultrasonic transducer transmits and receives an ultrasonic wave toward the position reference object via the inspection object, and horizontally scans the ultrasonic transducer in a direction passing through the adjacent section of the position reference object. ,
It is determined whether the reception signal of the ultrasonic transducer is a plane pattern of the position reference object by the horizontal scanning, and the ultrasonic transducer and the position reference object are received until a reflection signal from the plane pattern of the position reference object is received. Repeatedly moving the ultrasonic transducer horizontally in a direction passing through the adjacent section of the position reference object by changing the distance between the ultrasonic vibrator and the position reference object by relatively moving
When a reflected signal from the planar pattern of the position reference object is received, the ultrasonic transducer and the position reference object are moved relative to each other to change the received signal of the ultrasonic vibrator, and the transmission / reception focus of the ultrasonic vibrator Specifies the relative position of the ultrasonic transducer and the position reference object that coincide with the upper surface of the position reference object,
The ultrasonic transducer and the position reference object are relatively moved from the specified position by a known distance between the inspection layer inside the inspection target and the upper surface of the position reference object, and transmission / reception of the ultrasonic transducer is performed. An ultrasonic inspection apparatus configured to make a focal point coincide with an inspection position inside the inspection object.

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