CN1261760C - Ultrasonic imaging non-destructive testing method and testing system for bonding quality of electrical switch contacts - Google Patents

Abstract

The invention discloses an ultrasonic imaging nondestructive testing method and a testing system for the bonding quality of electrical switch contacts. Based on the principle of ultrasonic nondestructive testing and an image processing method, a water immersion focusing probe is used to scan the bonding surface of switch contacts point by point. The ultrasonic reflection echo detection signal at each point is sampled to form an ultrasonic scanning image of the joint surface, an appropriate threshold is selected, and the image processing method is used to separate the bound area and the unbound area in the ultrasonic image, and the interface binding rate is calculated. The detection and detection system consists of an ultrasonic signal generator, a probe, a three-dimensional precision scanning platform, an image acquisition card, a stepper motor drive card, a stepper motor drive power supply, an industrial control computer and system software. The invention has high degree of automation, has the characteristics of accurate detection, high efficiency, reliability, etc., and realizes the nondestructive detection of the bonding quality of switch contacts.

Description

Ultrasonic imaging non-destructive testing method and testing system for bonding quality of electrical switch contacts

Technical field

The invention belongs to the technical field of ultrasonic nondestructive testing, and in particular relates to an ultrasonic imaging nondestructive testing method and a testing system for the bonding quality of electrical switch contacts.

Background technique

The electrical contact is the key component of the electrical switch. The electrical contact includes two parts: the contact and the support. The quality of the combination of the contact and the support directly affects whether the electrical switch can work reliably and stably. The traditional method of contact bonding quality inspection mainly adopts the destructive test method. The destructive test method is to use tools to remove the contacts along the joint surface, so that the joint interface is exposed, and the quality of the joint is judged by estimating the magnitude of the force and the joint rate of the joint surface. This method obviously has many disadvantages and cannot accurately detect the binding quality. In addition, some non-destructive test methods such as X-ray method and infrared imaging method are also used to detect the quality of contact bonding, but due to the expensive equipment required by these methods and the low resolution of defects, they are generally difficult to be widely used .

Contents of Invention

In view of the above defects or deficiencies in the prior art, an object of the present invention is to provide an ultrasonic imaging non-destructive testing method for contact bonding quality. The method and system can quickly, easily and accurately detect contact bonding quality. The invention utilizes the principle of ultrasonic nondestructive testing and image processing technology, uses a water immersion focusing probe to scan the joint surface of the switch contact point by point, samples the ultrasonic reflection echo detection signal at each point, and forms an ultrasonic scanning image of the joint surface. Threshold, use the method of image processing to separate the bound area and unbound area in the ultrasound image, and calculate the interface binding rate.

Another object of the present invention is to provide a detection system for implementing the above method.

In order to achieve the above object, the present invention adopts the following technical solutions.

An ultrasonic imaging non-destructive testing method for contact bonding quality, comprising the following steps:

(1) Assemble the workpiece to be tested on the fixture in the water tank of the detection system, so that the contact interface of the workpiece to be tested is perpendicular to the ultrasonic incident sound beam;

(2) Adjust the parameters of the detection system, the detection parameters mainly include the sound velocity of the material, the thickness of the contact, and the scanning range of the probe;

The sound velocity of the material adopts the nominal longitudinal wave sound velocity, and for the contact of silver alloy material, the material sound velocity selects the nominal longitudinal wave sound velocity of silver to be 3600m/s;

(3) Place the probe above the contact, and according to the detection parameters, the three-dimensional precision scanning platform drives the probe to automatically focus on the joint surface to be tested;

(4) Determine the position of the sampling gate according to the reflected echo detection signal;

(5) Automatic scanning and real-time imaging of the tested joint surface;

(6) Analyzing the ultrasonic image of the junction surface, selecting a threshold, segmenting the junction area and the unbonding area, and calculating the interface binding rate;

In the method, the threshold selected in the segmentation of the ultrasonic image and the calculation of the combination rate is obtained by the following method: different workpieces of the same type are detected and the ultrasonic images are recorded, the detected workpiece is processed by sawing and planing, and the joint support body is removed (copper), until the thickness of the copper layer is about 0.3mm, and then soaked in ferric chloride solution for corrosion. After the copper layer is completely removed, the sample is taken out, and only the joint surface and the upper silver contact are left on the joint. It can be clearly seen that the joint surface is photographed with a digital camera, and the actual binding rate of the joint surface is calculated by image processing method. According to the result, an appropriate threshold is selected to calculate the joint rate of the ultrasonic image of the workpiece, so that the calculated binding rate is consistent with the actual binding rate. Threshold for artifacts. The same operation is performed on different workpieces of the same type, and the threshold value of multiple workpieces is averaged to obtain the threshold value of this type of workpiece.

(7) Automatically generate and print test reports.

The method has wide applicability and is not only suitable for the detection of the bonding quality of high-voltage switch contacts, but also for the detection of the bonding quality of low-voltage switch contacts. At the same time, the method is suitable for contact brazing interfaces, spot welding interfaces and sintering interfaces. detection.

The method can calculate the overall bonding ratio of the contacts, and can also calculate the local bonding ratio of the contacts.

The method can calculate the bonding ratio of rectangular contacts, and can also calculate the bonding ratio of contacts of other shapes (such as circular, elliptical, trapezoidal and irregular shapes).

An ultrasonic imaging non-destructive testing system for the combination quality of switches and contacts for realizing the above method, which is characterized in that it includes an ultrasonic signal generator, a probe, a three-dimensional precision scanning platform, an image acquisition card, a stepping motor drive card, and a stepping motor drive power supply , industrial control computer with system software and printer, constituted by electrical connection;

Among them, the image acquisition card, the stepper motor drive card, and the printer are respectively connected with the industrial control computer; the stepper motor drive card is connected with the stepper motor drive power supply, and is connected with the three-dimensional precision scanning platform through the stepper motor drive power supply; the image acquisition The card is connected through the ultrasonic signal generator and the three-dimensional precision scanning platform; the probe is respectively connected with the image acquisition card and the three-dimensional precision scanning platform; The software displays and processes the ultrasonic images, and at the same time evaluates the bonding quality, and the evaluation results are output by the printer in the form of a test report.

The above-mentioned image acquisition card circuit is composed of an analog-to-digital conversion channel, a clock generator, a window controller, A, B, and C scan mode selection circuits, a sound velocity measurement circuit, a DMA channel, image data storage and a bus management circuit; the input of the image acquisition card The signals include the echo RF signal and the detection signal, the synchronous trigger signal of the ultrasonic signal generator and the gate signal.

The clock generator is composed of an oscillation circuit and a frequency divider. The oscillation circuit is a high-precision horizontal crystal oscillator with temperature compensation, which generates an 80MHz clock signal, and generates 40MHz and 20MHz through the frequency divider. the clock signal;

The sound velocity measuring circuit determines the actual sound velocity of the sound wave by calculating the position of the gate signal, and at the same time determines the starting point of defect sampling.

The DMA channel makes the image acquisition card independent of the computer, and automatically completes the acquisition and storage of image data.

The image acquisition card performs analog-to-digital conversion, data exchange and storage, and ultrasonic imaging under the action of the system software. And the ultrasonic image is displayed and processed by the system software, and the bonding quality is evaluated at the same time, and the evaluation result is output by the printer in the form of a test report.

Because the invention adopts the ultrasonic non-destructive testing principle and the image processing method, it can accurately and reliably realize the non-destructive testing of the bonding quality of the switch contacts.

Description of drawings

Accompanying drawing 1 is the system schematic diagram of the ultrasonic non-destructive testing detection system for electrical switch contacts.

Accompanying drawing 2 is the schematic diagram of the automatic scanning detection system.

Accompanying drawing 3 is the functional block diagram of the image acquisition card circuit.

Accompanying drawing 4 is a functional block diagram of the system software.

Accompanying drawing 5 is the ultrasonic scanning image of coin surface.

Accompanying drawing 6 is the comparison diagram of the detection image of the high-voltage switch contact and the actual image, wherein (a) is the detection image, and (b) is the actual image.

Accompanying drawing 7 is the low-voltage switch contact detection image and the physical image comparison chart, wherein (a), (c), (e) are the detection images of rectangle, trapezoidal and irregular shape contacts respectively, (b) (d) ( f) The actual images of the bonding interface of rectangular, trapezoidal and irregular-shaped contacts, respectively.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Accompanying drawing 1 is the system schematic diagram of the electrical switch outlet combined with the quality ultrasonic non-destructive testing detection system. The industrial control computer 7 (hereinafter referred to as the industrial PC) is connected with the image acquisition card 4, the stepping motor drive card 5 and the printer 8. The stepper motor drive card is connected with the drive power supply 6 . The industrial PC 7 sends instructions to the stepper motor driver card through the system software 9, and the stepper motor driver card drives the three-dimensional precision scanning platform 3 to drive the probe 2 to move through the driving power to complete auto-focus or auto-scan. The probe 2 is excited by the ultrasonic transmitter and receiver 1, and emits ultrasonic waves of a certain frequency and intensity, which are reflected at the contact interface, and the reflected waves are received by the probe, and the ultrasonic transmitter and receiver transmit the reflected waves to the image acquisition card. The image acquisition card performs analog-to-digital conversion, data exchange and storage, and ultrasonic imaging under the action of the system software. And the ultrasonic image is displayed and processed by the system software, and the bonding quality is evaluated at the same time, and the evaluation result is output by the printer in the form of a test report.

Accompanying drawing 2 is the schematic diagram of the automatic scanning detection system. The X, Y, and Z axes are driven by lead screws, and the rotation force is provided by stepping motors or servo motors. The screw can be a linear screw or a ball screw, and its movement speed is 10mm/s～200mm/s. The X-axis 10 and the Y-axis 11 drive the probe to move horizontally to complete the scanning function, and the Z-axis 12 drives the probe to move vertically to complete the auto-focus function. The water in the water tank 13 acts as a coupling agent. The function of the fixture 14 is to ensure that the measured bonding interface of the workpiece is perpendicular to the incident ultrasonic beam.

Accompanying drawing 3 is the functional block diagram of the image acquisition card circuit. The image acquisition card circuit consists of an analog-to-digital conversion channel 15, a clock generator 16, a window controller 17, A, B, and C scanning mode selection circuits 18, a sound velocity measurement circuit 19, a DMA channel 20, an image data storage 21 and a bus management circuit 22 composition. The input signals of the image acquisition card include the echo RF signal and detection signal, the synchronous trigger signal of the ultrasonic signal generator and the gate signal. The analog-to-digital conversion channel is composed of a signal adjustment circuit 23 and a high-speed AD converter 24 . The signal adjustment circuit is composed of a low-noise, high-precision, high-speed broadband operational amplifier. Its function is to adjust the input signal to the range required by the AD converter. The high-speed AD converter uses AD9058, and the conversion accuracy is 8 bits, the highest The sampling speed is 50MSPS, and the RF signal and detection signal are converted and sampled by the analog-to-digital conversion channel. The clock generator is composed of an oscillating circuit and a frequency divider. The oscillating circuit is a high-precision horizontal crystal oscillator with temperature compensation. It generates an 80MHz clock signal, and generates 40MHz and 20MHz clock signals through the frequency divider. . The clock generator provides a clock reference for the whole interface circuit, so that the whole circuit works in harmony. The sound speed measurement circuit is composed of two D flip-flops and a 8254 programmable counter. The sound speed measurement circuit determines the actual sound speed of the sound wave by calculating the position of the gate signal, and at the same time determines the starting point of defect sampling. The ABC scan selection circuit is composed of a 8254 programmable counter. Its function is to enable the circuit to complete the A, B, and C scan functions. During A scan, the modulus channel collects RF signals, and collects detection signals during B and C scans. The window controller is composed of a piece of 8254 programmable counter, a piece of GAL16V8A chip and a piece of D flip-flop, and its function is to determine the scanning range of ultrasonic detection. A DMA channel consists of a DMA controller, an address generator, and an internal bus. The role of the DMA controller is to generate various control signals required by the DMA. The address generator consists of 4 slices of 4-bit binary counters (74F161), which generate 16-bit addresses. The internal bus includes a 16-bit address bus, an 8-bit data bus and a control bus. The DMA channel makes the image acquisition card independent of the computer, and automatically completes the acquisition and storage of image data. The data memory adopts 2 slices of CY7C198 static RAM, which is a 12ns 32K×8 chip, and the total capacity of image data storage is 64K. The bus management circuit consists of two GAL16V8A chips and two GAL20V8A chips.

Accompanying drawing 4 is a functional block diagram of the system software. The system software is developed by Visual C++ under the Windows 98 platform, and consists of a database management module 25, a parameter input module 26, an interface circuit initialization module 27, an automatic focus module 28, A, B, C scanning modules 29, and a sound velocity measurement module 30 , signal and image processing module 31, defect analysis and judgment module 32 and so on. The database management module includes two parts, an image database 33 and a detection parameter database 34 . The input of the image parameters can be input directly, and the data in the detection parameter database can also be called. After the parameters are input, the interface circuit is initialized according to the parameters. At this time, the whole system can perform sound velocity measurement or automatic focusing. After auto-focusing, select A, B, and C scanning modes to scan the workpiece. After scanning, use the signal and image processing module to process the scanning results, and further use the defect analysis and judgment module to evaluate the scanning results.

By adopting the method of the present invention, the workpiece to be tested can be a high-voltage switch contact or a low-voltage switch contact; the workpiece to be tested can be a combination of brazing contacts, or a combination of sintered contact interfaces or spot welding contacts, The interface bonding ratio may be the bonding ratio of the entire contact area, or the bonding ratio of the partial area of the contact, and the shape of the contact may be rectangular or other shapes.

The sound velocity of the material adopts the nominal longitudinal wave sound velocity. For the silver alloy contact, the material sound velocity selects the nominal longitudinal wave sound velocity of silver as 3600m/s.

The scanning sampling interval can be adjusted according to the resolution requirements, the image pixel level can be selected from 256 or 16, and the image display can be displayed in two ways: pseudo-color image or grayscale image.

Example 1:

With reference to accompanying drawing 5, accompanying drawing 5 is a one-yuan coin surface scanning image, can find out by Fig. 5, use method and detection system of the present invention can correctly image coin surface, and resolution is higher, therefore proves the feasibility of the present invention sex and effectiveness.

Example 2:

Referring to accompanying drawing 6, accompanying drawing 6 is the detection image and the physical photo of the annular brazing interface of the high-voltage switch contact. It can be seen from Fig. 5 that the detection image has a good consistency with the real object photo, and the detection image accurately reflects the combination of the interface between the contact and the support body. Using the method of the present invention to calculate the segmentation threshold of this type of workpiece is 120, the segmentation threshold of the contact in Figure 6 is 120, and the combination rate is 72%.

Example 3:

Referring to accompanying drawing 7, accompanying drawing 7 is the low-voltage switch contact detection image and real photograph. (a), (c), and (e) are the detection images of rectangular, trapezoidal, and irregular-shaped contacts, respectively, and (b) (d) (f) are the real objects of the bonding interface of rectangular, trapezoidal, and irregular-shaped contacts, respectively. image. (a) is the segmentation threshold: 130, the binding rate: 71%; (c) is the segmentation threshold: 140, the binding rate: 84%; (e) is the segmentation threshold: 120, the binding rate: 92%. It can be seen from accompanying drawing 5 that the detection image has a good consistency with the real photo. The results shown in Table 1 are obtained by calculation. It can be seen from this that the invention is not only applicable to the detection of high-voltage switch contacts, but also suitable for the detection of low-voltage switch contacts.

Table 1 Test results of contacts with different shapes Workpiece shape segmentation threshold Binding rate% rectangular trapezoidal irregular shape 130140120 718492

Claims (7)

1. A method for ultrasonic imaging non-destructive testing of switch contact bonding quality, characterized in that, comprising the steps: (1) Assemble the workpiece to be tested on the fixture in the water tank of the detection system, so that the contact interface of the workpiece to be tested is perpendicular to the ultrasonic incident sound beam; (2) Adjust the parameters of the detection system, the detection parameters mainly include the sound velocity of the material, the thickness of the contact, and the scanning range of the probe; The sound velocity of the material adopts the nominal longitudinal wave sound velocity, and for the contact of silver alloy material, the material sound velocity selects the nominal longitudinal wave sound velocity of silver to be 3600m/s; (3) Place the probe above the contact, and according to the detection parameters, the three-dimensional precision scanning platform drives the probe to automatically focus on the joint surface to be tested; (4) Determine the position of the sampling gate according to the reflected echo detection signal; (5) Automatic scanning and real-time imaging of the tested joint surface; (6) Analyzing the ultrasonic image of the junction surface, selecting a threshold, segmenting the junction area and the unbonding area, and calculating the interface binding rate; The threshold selected in the calculation of the segmentation and combination rate of the ultrasound image is obtained by the following method: Detect different workpieces of the same type and record ultrasonic images. First, the workpiece after inspection is sawed and planed to remove the copper support of the contact until the thickness of the copper layer is about 0.3mm, and then soaked in ferric chloride solution Carry out corrosion, and after the copper layer is completely removed, the sample is taken out, and only the joint surface and the upper silver contact are left in the joint. Binding rate, according to this result, select an appropriate threshold to calculate the binding rate of the ultrasonic image of the workpiece, so that the calculated binding rate is consistent with the actual binding rate, and determine the threshold of the workpiece; perform the same operation on different workpieces of the same type, and average the thresholds of multiple workpieces value, the threshold value of this type of artifact is obtained; (7) Automatically generate and print test reports. 2. according to the ultrasonic imaging non-destructive testing method of the bonding quality of switch contact according to claim 1, it is characterized in that, described tested workpiece is high-voltage switch contact, or low-voltage switch contact; Tested workpiece is brazing contact Head bonding, or sintered contact interface bonding or spot welding contact bonding, the interface bonding rate is the bonding rate of the entire contact area, or the bonding rate of the partial area of the contact, and the shape of the contact is a rectangle. 3. The ultrasonic imaging nondestructive testing method for the bonding quality of switch contacts according to claim 1, wherein the scanning sampling distance is adjusted according to the resolution requirements, the image pixel level is selected to be 256 or 16, and the image display adopts pseudo-color Image or grayscale image in two ways. 4. A detection system of an ultrasonic imaging non-destructive testing method for the combined quality of switch contacts, characterized in that it includes an ultrasonic signal generator (1), a probe (2), a three-dimensional precision scanning platform (3), an image acquisition card (4 ), a stepper motor drive card (5), a stepper motor drive power supply (6), an industrial control computer (7) with system software (9) and a printer (8), constituted by electrical connection; Wherein the image acquisition card (4), the stepper motor driver card (5), and the printer (8) are respectively connected with the industrial control computer (7); the stepper motor driver card (5) is connected with the stepper motor driver power supply (6) , and connected to the three-dimensional precision scanning platform (3) through the stepper motor drive power supply (6); the image acquisition card (4) is connected through the ultrasonic signal generator (1) and the three-dimensional precision scanning platform (3); the probe (2) Connect with the image acquisition card (4) and the three-dimensional precision scanning platform (3) respectively; the image acquisition card (4) performs analog-to-digital conversion, data exchange storage and ultrasonic imaging under the action of the system software (9), and the ultrasonic imaging is performed by the system software The image is displayed and processed, and the bonding quality is evaluated at the same time, and the evaluation result is output by the printer in the form of a test report; Described image acquisition card circuit is made of analog-to-digital conversion channel (15), clock generator (16), window controller (17), A, B, C scanning mode selection circuit (18), measuring sound velocity circuit (19), DMA channel (20), image data storage (21) and bus management circuit (22); the input signal of image acquisition card includes echo RF signal and detection signal, ultrasonic signal generator synchronous trigger signal and gate signal; Described clock generator (16) is made up of start-up circuit and frequency divider, and start-up circuit is a horizontal crystal oscillator with temperature compensation of high precision, and it produces the clock signal of 80MHz, produces through the effect of frequency divider 40MHz and 20MHz clock signals; The sound velocity measuring circuit (19) determines the actual sound velocity of the sound wave by calculating the position of the gate signal, and simultaneously determines the defect sampling starting point; The DMA channel (20) makes the image acquisition card independent of the computer, and automatically completes the acquisition and storage of image data. 5. The detection system of the ultrasonic imaging non-destructive testing method for the bonding quality of switch contacts as claimed in claim 4, characterized in that, the three-dimensional precision scanning platform (3) consists of X axis (10), Y axis (11), The Z-axis (12) is composed of three-dimensional motion modules, and each dimensional motion module is composed of a lead screw and a motor. The X-axis (10) and the Y-axis (11) enable the probe to move horizontally, and the Z-axis (12) enables the probe to move vertically. 6. The detection system of the ultrasonic imaging non-destructive testing method of the switch contact bonding quality as claimed in claim 4, wherein the leading screw of the three-dimensional precision scanning platform (3) is a linear screw or a ball screw, The motor is a stepping motor or a servo motor, and its moving speed is 10mm/s～200mm/s. 7. the detection system of the ultrasonic imaging nondestructive testing method of switch contact bonding quality as claimed in claim 4, is characterized in that, described system software (9) is made up of database management module (25), interface circuit initialization module (26) , parameter input module (27), autofocus module (28), A, B, C scanning module (29), sound velocity measurement module (30), signal and image processing module (31), defect analysis and judgment module (32) composition.

Images