Waveform simulator and ultrasonic imaging device

Abstract

A waveform simulator (10) comprises: a first processing unit (1) that performs first processing to calculate, on the basis of layer structure information a delay time from when an ultrasound wave is emitted from a probe into a laminated body until the probe receives a reflected wave from a target interface; a second processing unit (2) that performs second processing to calculate a first transmittance from when the ultrasound wave is output from the probe to when the ultrasound wave reaches the target interface; a third processing unit (3) that performs third processing to calculate a reflection coefficient of a reflection generated inside a target laminated portion by the ultrasound wave; and a fourth processing unit (4) that performs fourth processing to calculate a second transmittance until the reflected wave reaches the probe from the target interface.

Description

Waveform simulator and ultrasonic imaging device

[0001] The present invention relates to a waveform simulator and an ultrasonic imaging device that simulates the reflected waves that are reflected and returned from a target interface that indicates the bottom surface of a target laminate that indicates a desired laminate when ultrasonic waves are irradiated onto a laminate having a multiple layer structure.

[0002] Generally, ultrasonic detection of defects in a multi-layered object is achieved by utilizing the reflection characteristics due to differences in acoustic impedance. Ultrasonic waves propagate through liquids and solids, generating reflected waves (echoes) at the boundaries and voids between materials with different acoustic impedances. Reflected waves from defects such as delaminations and voids have higher intensity than waves reflected from areas without defects. Therefore, by imaging the reflection intensity at the interface between each layer of the object, it is possible to obtain an image that clearly shows the defects present in the object.

[0003] An ultrasonic imaging device scans an ultrasonic probe two-dimensionally in the horizontal direction, and generates an image of a defect using amplitude information and time information within a time gate (a time range of interest) of reflected waves from an inspection target portion of an inspection target. If the inspection target has a defect and reflected waves originating from the defect exist within the time gate, a difference will occur between the reflected waves from the defective inspection target and the reflected waves from a sound inspection target without any defects, and this can be observed as a defect image.

[0004] The ultrasonic imaging device of Patent Document 1 has a time gate setting unit, which receives as input a defect-free calculation model in which no defect of the inspection object is set and a defect-containing calculation model in which a defect is set as a calculation model, and obtains ultrasonic waves propagating through the inspection object for each of the defect-free calculation model and the defect-containing calculation model by numerical simulation, and the time gate is disclosed to be at least a part of the time range in which the waveform of the ultrasonic waves obtained by the defect-free calculation model and the waveform of the ultrasonic waves obtained by the defect-containing calculation model are different from each other.

[0005] JP 2018-189550 A

[0006] The device described in Patent Document 1 can obtain ultrasonic wave propagation through numerical simulation using an existing simulator, but in order to set a time gate, two types of models must be prepared: one without a defect and one with a defect. In addition, in a state where it is unknown where the defect is located, repeated trial and error is required to set the time gate.

[0007] Furthermore, while existing simulators can obtain the overall waveform of the reflected wave, they are unable to clearly grasp the relationship between structural information and the time position at which the reflected wave rises, making it difficult to set the time gate position for a specific interface.

[0008] Therefore, an object of the present invention is to provide a waveform simulator and an ultrasonic imaging device that can easily set a time gate for an object to be inspected having a multi-layer structure with multiple inspection interfaces, and that can determine the reflected wave reflected from a desired interface when ultrasonic waves are irradiated onto a laminate.

[0009] In order to solve the above problem, the waveform simulator of the present invention is a waveform simulator that simulates a reflected wave that is reflected and returned from a target interface representing the bottom surface of a target laminate portion representing a desired laminate portion when ultrasonic waves are irradiated onto a laminate having a multiple layer structure, and is characterized by comprising: a first processing unit that inputs layer structure information including the material and thickness of each laminate portion constituting the laminate, and calculates a delay time from when the ultrasonic waves are irradiated onto the laminate from a probe to when the reflected wave from the target interface is received by the probe using the layer structure information and a material database, a second processing unit that performs a second processing that calculates a first transmittance from when the ultrasonic waves are output from the probe to when they reach the target interface using the sound speed and density of each laminate portion, a third processing unit that performs a third processing that calculates a reflectance of the ultrasonic waves reflected inside the target laminate portion using the sound speed and density of each laminate portion, and a fourth processing unit that performs a fourth processing that calculates a second transmittance from when the reflected wave reaches the probe from the target interface using the sound speed and density of each laminate portion. Other aspects of the present invention will be described in the embodiments described below.

[0010] According to the present invention, when ultrasonic waves are irradiated onto a laminate, the reflected waves reflected from the desired interfaces can be obtained so that time gates can be easily set for an object to be inspected that has a multi-layer structure with multiple inspection interfaces.

[0011] 1 is a block diagram showing the configuration of a waveform simulator according to the first embodiment. FIG. 2 is a diagram showing an example of layer structure information. FIG. 3 is a diagram showing a material database. FIG. 4 is a diagram showing an example of calculating a delay time. FIG. 5 is a diagram showing an example of calculating a first transmittance. FIG. 6 is a diagram showing an example of calculating a reflectance. FIG. 7 is a diagram showing an example of calculating a second transmittance. A flowchart showing the processing of the waveform simulator according to the first embodiment. FIG. 8 is a diagram showing the configuration of an ultrasonic imaging device according to a second embodiment. A flowchart showing the processing of an ultrasonic imaging device according to the second embodiment. A diagram showing an example of a simulated reflected wave displayed on a display unit. A diagram showing superimposed simulated reflected waves. A diagram showing an example of a propagation path in which reflection occurs only in a specific layer. A diagram showing waveform data calculated for a propagation path in which reflection occurs only in a specific layer. A diagram showing an example screen of a waveform simulator. A diagram showing the hardware configuration of a waveform simulator, etc.

[0012] An ultrasonic imaging device is a useful tool for inspecting whether there are any defects such as peeling or voids at the target interface by irradiating ultrasonic waves onto the object to be inspected, such as a semiconductor wafer or semiconductor package having a multi-layer structure, acquiring the reflected waves that are reflected back from the laminate, and checking the waveform of the reflected waves from the target interface, which is the bottom surface of the target laminate that indicates the desired laminate.

[0013] When the object to be inspected has a multi-layer structure, the reflected wave is returned from each layer that makes up the stack, resulting in a waveform with a series of multiple peaks. Therefore, when observing the waveform to be inspected, a gate is set to extract that waveform. For example, when the object to be inspected is a five-layer stack, and the target layer is the third layer, and the reflected wave from the bottom surface of the target interface is to be observed, a gate is set to include a peak portion at a position that surrounds the reflected wave from the target interface of the third layer.

[0014] This gate setting work requires skill, and facilitating the work will greatly improve work efficiency.

[0015] When ultrasonic waves are irradiated onto a laminate, the waveform simulator generates a simulated reflected wave that simulates the wave reflected from the target interface, and assists in the task of setting an appropriate gate for the reflected wave from the target interface.This allows the task to be performed quickly without being affected by the operator's level of skill, greatly improving the efficiency of inspection for defects in laminates.

[0016] 1 is a block diagram showing the configuration of a waveform simulator 10 according to a first embodiment. The waveform simulator 10 includes an input unit 9 for inputting layer structure information of a laminate, a material database 7 for storing information about materials, a first processing unit 1 (see FIG. 4 ) for performing a first process for calculating a delay time, a second processing unit 2 (see FIG. 5 ) for performing a second process for calculating a first transmittance, a third processing unit 3 (see FIG. 6 ) for performing a third process for calculating a reflectance, a fourth processing unit 4 (see FIG. 7 ) for performing a fourth process for calculating a second transmittance, a simulation signal generating unit 5 for generating a simulation signal, a waveform converting unit 6 for generating a simulated reflected wave, and a waveform database 8 (storage unit) for storing the delay time and the simulated reflected wave.

[0017] The input layer structure information 22 includes the name (material) of the material of each laminated portion constituting the laminate for which waveform simulation is performed, and the thickness of each laminated portion.

[0018] Fig. 2 is a diagram showing an example of the layer structure information 22. In the case of the stacked structure 21 in Fig. 2, the number of stacked layers is five (a first layer L1, a second layer L2, a third layer L3, a fourth layer L4, and a fifth layer L5), and further includes a liquid medium (usually water) that propagates the ultrasonic waves emitted from the ultrasonic probe 50 to the stacked body.

[0019] The layer structure information 22 includes the layer name, material name, and thickness (thickness). In this figure, the material names of the respective laminated layers are expressed as Material 1 and Material 2, but in reality, epoxy resin, silicon, etc. are input. The unit of thickness is mm.

[0020] 3 is a diagram showing the material database 7. The material database 7 stores the sound speed and density for each material name constituting the laminate. In the process of generating a simulated reflected wave from the target interface, the waveform simulator 10 uses the sound speed and density of each laminate part constituting the laminate. Therefore, the sound speed and density of various material names are stored in the material database 7 in advance, and the sound speed and density of each laminate part are extracted from the material database using the material name of the layer structure information input from the input unit 9 as a key. The unit of sound speed is m / sec, and the unit of density is g / cm. 3 The material database 7 may also include acoustic impedance, which will be described later.

[0021] 4 is a diagram showing an example of calculating the delay time. FIG. 4 is a diagram related to the first processing for calculating the delay time in the first processing unit 1. When ultrasonic waves are irradiated onto the laminate, the ultrasonic waves propagate through each laminate section and reach the substrate. During this propagation process, a propagation delay occurs. The delay time of each laminate section can be calculated using the following formula: (Delay time) = (Thickness of laminate section) / (Speed ​​of sound within laminate section) Since propagation delay occurs in all laminate sections, the delay time occurring up to the interface of the nth laminate section can be calculated using the following formula.

[0022] Here, n is the number of layers up to the target interface, k is an integer variable from 0 to n, V is the sound velocity, and D is the thickness.

[0023] Propagation delay consists of the delay that occurs between the time when the ultrasonic wave emitted from the probe reaches the target interface and the time when the reflected wave returns from the target interface and reaches the probe. The final delay time can be calculated using the following formula.

[0024]

[0025] 5 is a diagram showing an example of calculating the first transmittance. FIG. 5 is a diagram showing the second process of calculating the first transmittance in the second processing unit 2. Ultrasonic waves are attenuated as they pass through interfaces before the target interface after being emitted from the ultrasonic probe 50 and before reaching the target interface. Therefore, the amplitude of the ultrasonic waves before passing through a certain interface is multiplied by the transmittance of the interface. As shown in FIG. 5, for example, the transmittance of an interface 1 between the first layer stack and the second layer stack can be calculated using the following formula.

[0026] (Transmittance) = (2Z2) / (Z1 + Z2) where Z represents the acoustic impedance of each laminated portion, and can be calculated by Z = (sound velocity of laminated portion) x (density of laminated portion). Here, Z1 is the acoustic impedance of the laminated portion of the first layer L1, and Z2 is the acoustic impedance of the laminated portion of the second layer L2. Z1 is the acoustic impedance of the laminated portion of the first layer L1, and Z2 is the acoustic impedance of the laminated portion of the second layer L2. １ And Zn is Z ｎ It may be written as:

[0027] Ultrasonic wave attenuation occurs at each interface through which the ultrasonic waves pass, including the surface of the first layer L1, from the time the ultrasonic waves are emitted from the ultrasonic probe 50 until they reach the target interface. Therefore, if the amplitude of the ultrasonic waves emitted from the ultrasonic probe 50 is Y, the transmittance of each interface is Tk, the ultrasonic waves that have passed through each interface and are attenuated are Yk, and the number of layers in the laminate is 3, the amplitude of the transmitted wave will attenuate as follows:

[0028] Y0=Y×T0 Y1=Y0×T1 Y2=Y1×T2 Y3=Y2×T3 Here, T0 is the transmittance of the surface of the first layer L1, and Y0 is the amplitude of the transmitted wave that has passed through the surface of the first layer L1.

[0029] Therefore, the final transmitted wave Y3 can be calculated as follows: Y3 = Y x T0 x T1 x T2 x T3

[0030] Therefore, when the number of layers in the laminate is three, if the overall transmittance of the ultrasonic waves emitted from the ultrasonic probe 50 until they reach the target interface (interface 3) is defined as a first transmittance, the first transmittance through the surface, interface 1, and interface 2 can be calculated by the following formula: (first transmittance) = T0 x T1 x T2

[0031] When the number of stacked layers in the laminate is n, the first transmittance can be calculated by the following formula: (First transmittance)=T0×T1× . . . ×(Tn-1) (Formula 3)

[0032] Therefore, the first transmittance of the stack having n stacked layers can be calculated by the following formula: (First transmittance)=(2×Z1 / (Z0+Z1))×...×(2×Zn / ((Zn−1)+Zn) (Formula 4)

[0033] 6 is a diagram showing an example of calculating the reflectance. FIG. 6 is a diagram showing the third process for calculating the reflectance in the third processing unit 3. When the ultrasonic wave reaches the target stack, it is reflected between the target interface, which is the bottom surface of the target stack, and the target top surface, which is the top surface of the target stack. In this embodiment, this reflection is simply referred to as reflection, and the reflectance is simply referred to as reflectance. Reflection occurs multiple times, but here it is assumed that it occurs five times. The number of reflections may be changed as necessary.

[0034] 6, there are three reflections from the target interface to the target upper surface portion and two reflections from the target upper surface portion to the target interface, for a total of five reflections. In other words, the number of reflections from the target interface to the target upper surface portion is one more than the number of reflections from the target upper surface portion to the target interface.

[0035] When the acoustic impedance of the target laminated section is Z2, the acoustic impedance of the previous laminated section is Z1, and the acoustic impedance of the next laminated section is Z3, a first reflectance indicating the reflectance of the first reflection of ultrasonic waves reflected from the target interface to the target upper surface can be calculated by the following formula: (First reflectance) = (Z3 - Z2) / (Z3 + Z2)

[0036] A second reflectance, which indicates the reflectance of the second reflection of the ultrasonic wave from the upper surface of the target to the target interface, can be calculated by the following formula: (Second reflectance)=(Z1-Z2) / (Z1+Z2).

[0037] As described above, the reflection within the target laminated portion occurs three times as the first reflection and two times as the second reflection, so the overall reflectance can be calculated as follows: (reflectance) = (first reflectance) ３ × (second reflectance) ２ =((Z3-Z2) / (Z3+Z2)) ３ ×((Z1-Z2) / (Z1+Z2)) ２

[0038] Therefore, when the nth layer is the target layer, the reflectance can be calculated using the following formula: (Reflectance)=((Zn+1)-Zn) / ((Zn+1)+Zn) ３ ×((Zn-1)-Zn)) / ((Zn-1)+Zn)) ２ (Formula 5)

[0039] 7 is a diagram showing an example of calculating the second transmittance. Fig. 7 is a diagram showing a fourth process for calculating the second transmittance in the fourth processing unit 4. In the propagation path of an ultrasonic wave from the target interface, where the reflected wave returns to the probe and is input to the probe, the ultrasonic wave is attenuated at each interface through which the ultrasonic wave passes from the target interface to the probe, similar to the propagation path of an ultrasonic wave emitted from the probe to the target interface. Therefore, similar to the first transmittance, the amplitude of the reflected wave reaching the probe can be calculated by calculating a second transmittance indicating the transmittance from the target interface to the probe and multiplying the second transmittance by the reflected wave reflected at the target interface.

[0040] When the number of layers in the laminate is n and the acoustic impedance of each laminate is Zk (k is a positive integer from 0 to n), the second transmittance can be calculated by the following formula: (Second transmittance)=(2×Z0 / (Z0+Z1))×...×(2×(Zn-1) / ((Zn-1)+Zn) (Formula 6)

[0041] The processing from the first processing unit 1 to the fourth processing unit 4 has been explained above. As a result of these processing steps, the waveform simulator processes the process in which the ultrasonic waves emitted from the ultrasonic probe 50 are reflected at the target interface, return to the ultrasonic probe 50, and are input as follows.

[0042] 8 is a flowchart showing the process (S100) of the waveform simulator 10 according to the first embodiment. FIG. 1 is also referred to as appropriate. The waveform simulator 10 first inputs, from the input unit 9, stacking structure information of the laminate to be subjected to waveform simulation (S101). Specifically, information on the material and thickness of each of the first to nth stacking layers is input.

[0043] Next, the first processing unit 1 to the fourth processing unit 4 execute the first processing to the fourth processing for each stacked portion constituting the stack, and calculate the delay time and simulated reflected wave for each stacked portion and store them in the waveform database 8.

[0044] The process will be described in detail below. The waveform simulator 10 inputs layer structure information (S101), sets a parameter n (number of layers), and assigns 1 as its initial value (S102). The waveform simulator 10 identifies the layer structure corresponding to parameter n as a target layer structure, and extracts the sound velocity and density of the material from a material database using the material of the target layer structure included in the input layer structure information as a search key (S103). The waveform simulator 10 uses the sound velocity, density, and thickness of the target layer structure to execute first to fourth processes in first processing unit 1 to fourth processing unit 4 (S104 to S107), thereby calculating the delay time, first transmittance, reflectance, and second transmittance for the target layer structure.

[0045] Next, the waveform simulator 10 generates a simulation signal using the simulation signal generator 5 (S108). The simulation signal corresponds to the ultrasonic waves emitted from the probe in an actual ultrasonic imaging device. The simulation signal preferably uses a sinc function, which has a waveform similar to that of the actual ultrasonic waves. The sinc function is an elementary function obtained by dividing a sine function by its variable.

[0046] The waveform simulator 10 inputs the first transmittance, reflectance, second transmittance, and simulated signal calculated by the above processing to the waveform converter 6, multiplies the first transmittance, reflectance, and second transmittance to calculate the amplitude change rate (S109), and multiplies the simulated signal by the amplitude change rate to calculate a simulated reflected wave (S110). The waveform simulator 10 stores the delay time and the simulated reflected wave in the waveform database, linking them to the value of n of the target laminate (S111). (Simulated reflected wave) = Y × (First transmittance) × (Reflectance) × (Second transmittance), where Y is the simulated signal generated by the simulated signal generator.

[0047] The waveform simulator 10 increments n and executes all processes from the first process on all stacked parts included in the input layer structure information, repeating this process until the delay time and simulated reflected wave are stored in the waveform database 8 (S112, S113).

[0048] The work of actually using an ultrasonic imaging device to set gates for reflected waves from each interface constituting a laminate can be carried out as in the second embodiment. Prior to the actual work, a waveform simulation is performed using a waveform simulator, and the delay times and simulated reflected waves for each laminate are stored in a waveform database. In the actual work, the delay times and simulated reflected waves for each laminate stored in the waveform database are called up, and time gates (gates) are set around the simulated signals.

[0049] In this way, by using the waveform simulator 10, it is possible to easily and accurately set time gates for each stacked portion, regardless of the skill level of the worker.

[0050] Second Embodiment In the second embodiment, an ultrasonic imaging device 100 incorporating the waveform simulator 10 of the first embodiment will be described. Fig. 9 is a diagram showing the configuration of the ultrasonic imaging device 100 according to the second embodiment. The ultrasonic imaging device 100 includes a waveform simulator 10 including a material database 7 and a waveform database 8, an ultrasonic probe 50, a probe driver 40 that drives the ultrasonic probe 50, and a control device 30. The control device 30 includes an input unit 9, a scan controller 31 that controls scanning of the probe driver 40, a gate information input unit 32, a transmission / reception controller 33 that exchanges signals with the probe, a gate setting unit 34, an image generator 35, and a display unit 36. The input unit 9 is shared by the ultrasonic imaging device and the waveform simulator.

[0051] The ultrasonic imaging device 100 irradiates ultrasonic waves via the ultrasonic probe 50 to irradiation points set at predetermined intervals within an inspection range of the object, acquires the reflected waves, extracts interface echoes indicating the waveform of the bonded interface to be inspected from the reflected waves, converts the signal intensity of the interface echoes into positive integer values ​​(0 to 255) and generates pixelated information, performs this process on all or specific irradiation points, and generates an image of the bonded interface based on the generated pixelated information for the irradiation points to find defects.

[0052] The ultrasonic probe 50 includes an encoder 51 that detects the scanning position of the ultrasonic probe 50, and a piezoelectric element 52 that converts between an electric signal and an ultrasonic signal. The piezoelectric element 52 is, for example, a single-focus ultrasonic sensor.

[0053] The control device 30 includes an input unit 9, a scan control unit 31 that controls the scan of the probe driver 40, a gate information input unit 32, a transmission / reception control unit 33 that exchanges signals with the probe, a gate setting unit 34, an image generation unit 35, and a display unit 36. The input unit 9 is shared by the ultrasound imaging device 100 and the waveform simulator 10.

[0054] The probe driver 40 controls the scanning position of the ultrasonic probe 50 using a mechanical controller 41, an X-axis scanner 42, a Y-axis scanner 43, and a Z-axis scanner 44, and the mechanical controller 41 receives information on the current scanning position of the ultrasonic probe 50.

[0055] The piezoelectric element 52 has electrodes attached to both sides of a piezoelectric film and is made of zinc oxide (ZnO), ceramics, fluorine-based copolymer, etc. The piezoelectric element 52 transmits ultrasonic waves from the piezoelectric film when a voltage is applied between the two electrodes. Furthermore, the piezoelectric element 52 converts the echo waves (received waves) received by the piezoelectric film into a received signal, which is a voltage generated between the two electrodes.

[0056] Water 61 is poured into the water tank 60, and a test object 62 is placed submerged in the water 61. The water 61 in the water tank 60 is a liquid substance that is a propagation medium necessary for efficiently propagating ultrasonic waves emitted from the opening at the bottom end of the ultrasonic probe 50 (ultrasonic probe) into the inside of the test object 62. The test object 62 is, for example, a semiconductor wafer or semiconductor package having a multi-layer structure.

[0057] The ultrasonic probe 50 is immersed in water 61 filled in a water tank 60, and is positioned above an object 62 so as to face the object 62 at a predetermined distance in the Z direction.

[0058] The ultrasonic probe 50 can be freely moved in the X, Y, and Z directions by the probe driver 40. For example, the ultrasonic probe 50 scans the subject 62 in the X-axis direction at a predetermined speed from the start point (one end point) to the end point (the other end point) of the subject 62 while irradiating the subject 62 with ultrasonic waves. When the ultrasonic probe 50 reaches the end point, the probe is moved a predetermined distance in the Y-axis direction, and scans in the opposite direction at a predetermined speed in the X-axis direction from the viewpoint to the end point.

[0059] Based on this movement, the ultrasonic probe 50 scans a predetermined measurement range on the surface of the specimen 62, transmits ultrasonic waves, receives reflected echo waves at multiple predetermined measurement points within the measurement range, and visualizes and inspects defects in the internal structure included in the measurement range.

[0060] The ultrasonic imaging device 100 is an ultrasonic imaging device including a waveform simulator 10 and a display unit 36, and inputs layer structure information of a laminate from an input unit 9, provides the layer structure information to the waveform simulator 10, calculates delay times and simulated reflected waves of all laminate parts that make up the laminate based on the layer structure information, stores them in a waveform database 8, obtains a display number selected in a display number selection unit 38 (see FIG. 11 ) displayed on the display unit 36, extracts the delay times and simulated reflected waves of the laminate parts corresponding to the display number using the display number as a search key, and displays the simulated reflected waves at a position delayed by the delay time on a two-dimensional plane set on the display unit 36 ​​with the horizontal axis as the time axis and the vertical axis as the amplitude axis.

[0061] The gate setting operation by the ultrasonic imaging device 100 will be described. Fig. 10 is a flowchart showing the process S120 of the ultrasonic imaging device 100 according to the second embodiment. Fig. 11 is a diagram showing an example of a simulated reflected wave displayed on the display unit 36. The ultrasonic imaging device 100 inputs layer structure information of the laminate to be inspected from the input unit 9 (S121). Based on the input layer structure information, a waveform simulation is performed to calculate delay times and simulated reflected waves for all laminate sections, and these are stored in the waveform database 8 (S122).

[0062] The ultrasonic imaging device 100 acquires the display number of the target stack from the display number selection unit 38 on the display unit 36, and displays the simulated reflected wave corresponding to the display number (S123). Then, the operator sets a gate on the display unit 36, stores the gate information in the gate information storage unit 70 (S124), and ends the process.

[0063] Figure 11 shows a diagram in which a simulated reflected wave from the third layer is displayed on the display unit. A display number indicating the number of the target laminate is obtained from the display number selection unit 38 displayed on the display unit 36. The obtained display number is used as a search key to extract the delay time and simulated reflected wave corresponding to the display number from the waveform database 8. Figure 11 shows an example in which the target laminate is input as the third laminate from the display number selection unit. A two-dimensional plane 37 is set on the display unit 36, with the time axis set on the horizontal axis and the amplitude axis set on the vertical axis, and the simulated reflected wave is displayed at the position of the extracted delay time. Note that a simulated signal 39 generated by the simulated signal generation unit 5 is shown for reference on the left side of Figure 11.

[0064] The worker uses a pointing device connected to the ultrasound imaging device 100 to trace the area (range) surrounding the simulated reflected wave displayed on the display unit 36, including the peak value of the simulated reflected wave, and sets this area (range) as the gate setting section 34 of the stack section corresponding to the display number.The time position and shape of the area are linked to the display number and stored in the gate information storage unit 70.

[0065] By performing these processes for all stacked layers, gate information for all stacked layers can be stored in the gate information storage unit.

[0066] When an operator actually inspects a laminate, the operator extracts gate setting information for the target laminate part to be inspected from the gate information storage unit 70 using the target laminate part number, i.e., the display number, as a search key, and sets the gate on the display unit 36. In this way, a highly accurate gate can be easily set for the target interface, regardless of the operator's level of skill.

[0067] In this manner, simulated reflected waves corresponding to all stacked layers included in the input layer structure information are calculated and stored in the waveform database 8. Furthermore, gate information corresponding to all stacked layers is calculated and stored in the gate information storage unit 70. In response to an instruction from an operator, the ultrasound imaging device 100 retrieves all of the simulated reflected waves and their corresponding gate information, and then superimposes all of the simulated reflected waves, taking into account the delay times of each simulated reflected wave, to form a single simulated reflected wave, which is then displayed in a two-dimensional space set on the display unit 36. When displaying the superimposed simulated reflected waves in two-dimensional space, the operator specifies how each simulated reflected wave can be distinguished from the other simulated reflected waves. The distinction may be made by color coding or by alternating thick and thin lines. This distinction method is pre-installed in the ultrasound imaging device. Figure 12 shows a diagram of superimposed simulated reflected waves, and in this example, each simulated reflected wave is distinguished by its shade.

[0068] The timing for displaying the superimposed simulated reflected waves may be determined by receiving instructions from an operator, or may be automatically determined when the simulated reflected waves and gate information corresponding to all stacked portions are stored.

[0069] <Example of a Waveform Simulator Screen> The features of the waveform simulator 10 will be further described. FIG. 13A is a diagram showing an example of a propagation path in which reflection occurs only at a specific layer. FIG. 13B is a diagram showing waveform data calculated for a propagation path in which reflection occurs only at a specific layer. The waveform simulator 10 of this embodiment can display, for example, multiple propagation paths in which reflection occurs only at a specific layer. Considering reflection at interface 1 in FIG. 13A, path 1 is the case where there is a single reflection at interface 1. Path 2 is the case where there is reflection at interface 1, reflection at interface 0, and further reflection at interface 1. Path 3 is the case where there is reflection at interface 1, reflection at interface 0, further reflection at interface 1, reflection at interface 0, and further reflection at interface 1. Therefore, if an operator wants to know the expected reflected waveform for only a specific layer, a display such as that shown in FIG. 13B can be used.

[0070] FIG. 14 is a diagram showing an example screen of the waveform simulator 10. The waveform simulation screen includes a layer structure input screen and a simulation waveform display section. In the comparative example (the method of Patent Document 1), only the overall waveform (thin line) indicated by reference numeral 81 is displayed, making it unclear which interface the reflection originated from. In contrast, with the waveform simulator 10 of this embodiment, if an operator wants to know the reflected wave from interface 1, for example, the specific interface waveform (thick line, actually a green line) indicated by reference numeral 82 can be displayed. This allows the operator to easily set a time gate to match the reflected wave from interface 1, for example. Furthermore, when the simulated reflected wave is displayed, it is displayed on the two-dimensional plane in the color specified on the layer structure input screen. This allows the operator to easily determine which interface the reflected wave originated from.

[0071] <Hardware Configuration> Fig. 15 is a diagram showing the hardware configuration of the waveform simulator 10, etc. A computer 1200 shown in Fig. 15 is one implementation of the input unit 9, processing units (first processing unit 1, second processing unit 2, third processing unit 3, fourth processing unit 4), simulation signal generation unit 5, waveform conversion unit 6, material database 7, and waveform database 8 shown in Fig. 1. Note that each unit may be implemented by multiple computers 1200.

[0072] The computer 1200 includes a memory 1201, a processor 1202, a storage device 1203 such as a hard disk (HD), a communication unit 1204 such as a network interface card (NIC), and a user interface unit 1205. Note that while a central processing unit (CPU) or a graphics processing unit (GPU) can be considered as an example of a processor, other semiconductor devices may also be used as long as they are capable of executing predetermined processing.

[0073] Then, the program stored in the storage device 1203 is loaded into the memory 1201, and the loaded program is executed by the processor 1202. This embodies the functions of the processing units shown in Fig. 1, the simulation signal generation unit 5, the waveform conversion unit 6, the material database 7, and the waveform database 8. The computer 1200 may have a display, a touch panel, a mouse, and a keyboard as a user interface unit 1205.

[0074] The waveform simulator 10 of the present embodiment described above has the following main features: (1) It is a waveform simulator that simulates a reflected wave that is reflected and returned from a target interface that represents the bottom surface of a target laminate that represents a desired laminate when ultrasonic waves are irradiated onto a laminate having a multiple layer structure, and includes: a first processing unit 1 that inputs layer structure information including the material and thickness of each laminate that constitutes the laminate, and performs a first processing that calculates, based on the layer structure information 22 and a material database 7, a delay time from when ultrasonic waves are irradiated onto the laminate from a probe (ultrasonic probe 50) to when the probe receives a reflected wave from the target interface; a second processing unit 2 that performs a second processing that calculates a first transmittance of the ultrasonic waves from when they are output from the probe to when they reach the target interface; a third processing unit 3 that performs a third processing that calculates a reflectance of the ultrasonic waves reflected inside the target laminate; and a fourth processing unit 4 that performs a fourth processing that calculates a second transmittance of the reflected wave from the target interface to when it reaches the probe.

[0075] (2) The waveform simulator of (1) has a simulated signal generating unit 5 that generates a simulated signal corresponding to an ultrasonic wave, calculates the delay time in all stacked sections, and the first transmittance, reflectance, and second transmittance in all stacked sections, multiplies these values ​​to calculate an amplitude change rate for the simulated signal, and stores the simulated reflected wave calculated by multiplying the amplitude change rate by the simulated signal in a memory unit (waveform database 8).

[0076] According to this embodiment, when an ultrasonic wave is irradiated onto a laminated body, a reflected wave from a desired interface can be obtained so that a time gate can be easily set for an object to be inspected that has a multi-layer structure with a multi-interface to be inspected. Therefore, an operator can easily set a high-precision gate (time gate) for a target interface, regardless of their level of skill.

[0077] As described above, the waveform simulator generates simulated reflected waves that simulate the waves reflected from the target interface when ultrasonic waves are irradiated onto the laminate, and assists in the task of setting appropriate gates for the waves reflected from the target interface.This allows the task to be performed quickly without being affected by the level of skill of the operator, greatly improving the efficiency of inspection for defects in the laminate.

[0078] REFERENCE SIGNS LIST 1 First processing unit 2 Second processing unit 3 Third processing unit 4 Fourth processing unit 5 Simulation signal generation unit 6 Waveform conversion unit 7 Material database 8 Waveform database (storage unit) 9 Input unit 10 Waveform simulator 21 Stacking configuration 22 Layer structure information 30 Control device 31 Scanning control unit 32 Gate information input unit 33 Transmission / reception control unit 34 Gate setting unit 35 Image generation unit 36 ​​Display unit 37 Two-dimensional plane 38 Display number selection unit 39 Simulation signal 40 Probe driving unit 41 Mechanical control unit 42 X-axis scanner 43 Y-axis scanner 44 Z-axis scanner 50 Ultrasonic probe (probe) 51 Encoder 52 Piezoelectric element 60 Water tank 61 Water 62 Subject 70 Gate information storage unit 100 Ultrasonic imaging device L1 First layer L2 Second layer L3 Third layer L4 4th layer L5 5th layer S100 Processing (processing of waveform simulator) S120 Processing (processing of ultrasonic imaging device) Z Acoustic impedance Zn, Z ｎ Acoustic impedance of the nth layer

Claims

1. A waveform simulator that simulates a reflected wave that is reflected and returned from a target interface that represents the bottom surface of a target laminate that represents a desired laminate when ultrasonic waves are irradiated onto a laminate having a multiple layer structure, comprising: a first processing unit that performs a first processing of inputting layer structure information including the material and thickness of each laminate that constitutes the laminate, and calculating a delay time from when the ultrasonic waves are irradiated from the probe onto the laminate to when the probe receives the reflected wave from the target interface, using the thickness and sound speed of each laminate, based on the layer structure information and a material database; a second processing unit that performs a second processing of calculating a first transmittance from when the ultrasonic waves are output from the probe to when they reach the target interface, using the sound speed and density of each laminate; a third processing unit that performs a third processing of calculating a reflectance of the ultrasonic waves reflected inside the target laminate, using the sound speed and density of each laminate; and a fourth processing unit that performs a fourth processing of calculating a second transmittance of the reflected wave from the target interface to when it reaches the probe, using the sound speed and density of each laminate.

2. A waveform simulator as claimed in claim 1, comprising a simulated signal generating section which generates a simulated signal equivalent to said ultrasonic wave, calculates the delay time in all of said laminated sections and the first transmittance, the reflectance and the second transmittance in all of said laminated sections, multiplies these values ​​to calculate an amplitude change rate for said simulated signal, and stores in a memory section a simulated reflected wave calculated by multiplying said simulated signal by said amplitude change rate.

3. A waveform simulator as claimed in claim 2, wherein in the first process, a sound velocity V of each of the laminated parts is extracted from the material database using the material of each of the laminated parts as a search key, and when the thickness of each of the laminated parts in the layer structure information is D, the number of layers of the laminated body up to the target interface is n, and k is a variable from 0 to n, The waveform simulator calculates the delay time by:

4. A waveform simulator according to claim 2, wherein in the second process, the acoustic impedance Z of each of the laminated parts is extracted from the material database using the material of each of the laminated parts as a search key, and the number of layers of the laminated body up to the target interface is n, and the acoustic impedance of the liquid medium is Z. ０ When the first transmittance is set to 1, the first transmittance is set to 1. １ ) / (Z ０ +Z １ )) ×... × (2Z ｎ / (Z ｎ－１ +Z ｎ ) calculating the first transmittance by the above formula (1).

5. A waveform simulator according to claim 2, wherein in the third process, when the target laminated section is the nth, the acoustic impedances of the n-1th, nth and n+1th laminated sections are extracted from a material database using the material of each of the laminated sections as a search key, and the Z of the acoustic impedance of each of the laminated sections is extracted, and the number of reflections occurring inside the target laminated section is set to 5, the reflectance is calculated as follows: ｎ＋１ )-Z ｎ )) / ((Z ｎ＋１ ) + Z ｎ ) ３ ×((Z ｎ－１ )-Z ｎ ) / ((Z ｎ－１ ) + Z ｎ ) ２ The waveform simulator calculates the reflectance by:

6. A waveform simulator according to claim 2, wherein in the fourth process, the acoustic impedance Z of each of the laminated parts is extracted from the material database using the material of each of the laminated parts as a search key, and the number of layers of the laminated body up to the target interface is n, and the acoustic impedance of the liquid medium is Z. ０ Then, (second transmittance) = (2(Z ０ ) / (Z ０ +Z １ )) × ... × (2 (Z ｎ－１ ) / (Z ｎ－1 +Z ｎ ) calculating the second transmittance by the above-mentioned method.

7. An ultrasonic imaging device comprising a waveform simulator according to any one of claims 2 to 6 and a display unit, characterized in that the layer structure information of the laminate is input from an input unit, the layer structure information is applied to the waveform simulator, the delay time and the simulated reflected wave of all the laminate parts constituting the laminate are calculated based on the layer structure information and stored in a waveform database, a display number selected in a display number selection unit displayed on the display unit is obtained, the display number is used as a search key to extract the delay time and the simulated reflected wave of the laminate part corresponding to the display number, and the simulated reflected wave is displayed at a position delayed by the delay time on a two-dimensional plane set on the display unit with the horizontal axis as the time axis and the vertical axis as the amplitude axis.

8. An ultrasonic imaging device as claimed in claim 7, further comprising a pointing device, wherein the ultrasonic imaging device sets a gate within a range traced on the display unit with the pointing device, and stores the position and shape of the gate as gate information in a gate information storage unit in association with the stack unit corresponding to the display number.

9. An ultrasonic imaging device as described in claim 8, characterized in that the simulated reflected waves corresponding to all of the laminated parts included in the layer structure information are stored in the waveform database, the gate information is stored in the gate information storage unit, the simulated reflected waves and the delay times corresponding to all of the laminated parts are retrieved, the simulated reflected waves of all the laminated parts are superimposed to form one simulated reflected wave, and the reflected waves of each of the laminated parts are displayed on the two-dimensional plane, distinguished from the reflected waves of the other laminated parts.

10. An ultrasonic imaging device according to claim 7, characterized in that, when the simulated reflected wave is displayed, it is displayed on the display unit in a color designated on a layer structure input screen.

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