阅读说明：本技术 一种基于超宽带微波的焊点质量检测方法 (Welding spot quality detection method based on ultra-wideband microwave ) 是由 王晓梅 李刚 陈彦萍 于 2020-12-09 设计创作，主要内容包括：本发明涉及一种基于超宽带微波的焊点质量检测方法,该方法包括：设置一检测台,上方设置一超宽带微波信号发射装置,下方设置一超宽带微波信号接收装置；发射装置发送指定模式的超宽带微波,接收装置获取背景信号；加载待检测电路板；获取检测信号；采用背景相减法计算预处理信号；采用后向投影算法生成待检测电路板图像；根据印制电路板布板图获取待检测焊点位置；根据待检测焊点位置,提取待检测焊点图像；根据待检测焊点图像与典型值拟合程度,判断焊点质量。本发明通过以指定模式的超宽带微波作为信号源,多根电线形成信号接收阵列,采用后向投影算法生成待检测电路板图像,与典型值拟合,判断焊点质量,提高了焊点检测的准确率。(The invention relates to a welding spot quality detection method based on ultra-wideband microwave, which comprises the following steps: arranging a detection table, arranging an ultra-wideband microwave signal transmitting device above the detection table, and arranging an ultra-wideband microwave signal receiving device below the detection table; the transmitting device transmits ultra-wideband microwaves in a specified mode, and the receiving device acquires a background signal; loading a circuit board to be detected; acquiring a detection signal; calculating a preprocessed signal by adopting a background subtraction method; generating a circuit board image to be detected by adopting a back projection algorithm; acquiring the position of a welding spot to be detected according to a printed circuit board layout; extracting an image of the welding spot to be detected according to the position of the welding spot to be detected; and judging the quality of the welding spot according to the fitting degree of the image of the welding spot to be detected and the typical value. According to the invention, ultra-wideband microwaves in a specified mode are used as a signal source, a plurality of wires form a signal receiving array, a back projection algorithm is adopted to generate a circuit board image to be detected, the circuit board image is fitted with typical values, the quality of welding spots is judged, and the accuracy of welding spot detection is improved.)

1. A welding spot quality detection method based on ultra-wideband microwave is characterized by comprising the following steps:

step 1, arranging a detection table T, and arranging an ultra-wideband microwave signal transmitting device D above the detection table_tAn ultra-wideband microwave signal receiving device D is arranged below the microwave signal receiving device_r；

Step 2, transmitting device D_tTransmitting ultra-wideband microwave of specified mode, receiving device D_rAcquiring background signal S of unloaded circuit board to be detected₀；

Step 3, loading a circuit board R to be detected on the detection table T;

step 4, transmitting device D_tTransmitting ultra-wideband microwave of specified mode, receiving device D_rAcquiring detection signal S after loading to-be-detected circuit board_R；

Step 5, adopting background subtraction method to detect signal S_RAnd a background signal S₀Calculating a preprocessed signal S_p；

Step 6, adopting a back projection algorithm and according to the preprocessed signal S_pGenerating a waitDetecting a circuit board image G_p；

Step 7, acquiring a position C of a welding spot to be detected according to a printed circuit board layout;

8, according to the position C of the welding spot to be detected, using the image G of the circuit board to be detected_pExtracting image G of welding spot to be detected_C；

Step 9, according to the image G of the welding spot to be detected_CAnd (5) judging the quality of the welding spot according to the fitting degree of the typical value.

2. The ultra-wideband microwave based solder joint quality detection method according to claim 1, wherein the mode of ultra-wideband microwave specified in step 2 further comprises:

the ultra-wideband microwave of a specified mode is a modulated Gaussian pulse E (t), and the mathematical expression of the signal mode is as follows:

wherein f is₀Is the center frequency of the signal, t₀Is the peak time of the signal pulse, t is the sampling time point of the modulated gaussian pulse time e (t), and τ is the pulse width of the signal.

3. The ultra-wideband microwave based solder joint quality detection method according to claim 1, wherein the back projection algorithm in step 6 further comprises:

step 6.1, dividing the image area into grids of x rows and y columns;

step 6.2, for mesh P_xyCalculating the transmitting device D_tTo the receiving device D_rActual propagation time t in_xy；

Step 6.3, mixing t_xyComputing the receiving device D as a time input of a time-domain finite difference method_rElectric field amplitude value W of the ith antenna_xyi；

Step 6.4, calculating the corresponding grid P_xyPosition receiving device D_rAll antennas inElectric field amplitude value W of_xy；

Step 6.5, with the value of electric field amplitude W_xyAs an image G of the circuit board to be inspected_pIn the grid P_xyGenerating an image G of the circuit board to be detected_p。

4. Backprojection algorithm as claimed in claim 3, characterized in that the transmitting means D in step 6.2_tTo the receiving device D_rActual propagation time t in_xyThe method also comprises the following steps:

calculating the actual propagation time t according to the following formula_xy：

Wherein x and y are respectively a line number and a column number after the image area is divided into grids, and l_xy1Is a grid P_xyThickness of position PCB printed circuit board, < i >_xy2Is a transmitting device D_tTo grid P_xyAnd a grid P_xyTo the receiving device D_rAir distance between l_xy3Is a grid P_xyTheoretical thickness of the solder joint or component at location, c is the speed of light in vacuum, ε_rIs the relative dielectric constant, ε, of the circuit board_r1Is a grid P_xyThe relative dielectric constants of the location pads and the components.

5. Backprojection algorithm as claimed in claim 3 wherein the corresponding grid P in step 6.4_xyPosition receiving device D_rElectric field amplitude value W of all antennas_xyThe method also comprises the following steps:

calculating the electric field amplitude values W of all the antennas according to the following formula_xy：

Wherein x and y are each independentlyIs the line number and column number after the image area is divided into grids, i is the antenna number, n is the receiving device D_rNumber of antennas in, W_xyiIs a receiving device D_rElectric field amplitude value of the ith antenna.

Technical Field

The invention relates to the technical field of circuit board welding spot quality detection, in particular to a welding spot quality detection method based on ultra-wideband microwave.

Background

At present, a method of Automatic Optical Inspection (AOI) is generally used for detecting defects of a Printed Circuit Board (PCB), and a main idea is to obtain a surface state image of a PCB finished product through a CCD (Charge Coupled Device) image sensor, then extract a local image of each welding point, perform defect detection by means of digital image processing and a classifier, display or mark the welding point of a suspected defect, and facilitate checking and repairing.

In practical application, as the size integration of components on a printed circuit board is higher and higher, more and more components are mounted by Ball Grid Array (BGA) packages, but the solder joints of the BGA components are hidden under the packages, and it is difficult to acquire the solder joint images by using an optical detection method, so that the solder joint defects of the components are difficult to be effectively, accurately and quickly detected by the conventional detection method.

Therefore, the method for detecting the quality of the welding spot in the prior art has the problem that the welding spot defect hidden under the component is difficult to effectively, accurately and quickly detect.

The above drawbacks are expected to be overcome by those skilled in the art.

Disclosure of Invention

Technical problem to be solved

In order to solve the problems in the prior art, the invention provides a welding spot quality detection method based on ultra-wideband microwave, which solves the problem that the welding spot defect hidden under a component is difficult to effectively, accurately and quickly detect in the prior art.

(II) technical scheme

In order to achieve the purpose, the invention adopts the main technical scheme that:

an embodiment of the invention provides a welding spot quality detection method based on ultra-wideband microwave, which comprises the following steps:

step 1, arranging a detection table T, and arranging an ultra-wideband microwave signal transmitting device D above the detection table_tAn ultra-wideband microwave signal receiving device D is arranged below the microwave signal receiving device_r；

Step 2, transmitting device D_tTransmitting ultra-wideband microwave of specified mode, receiving device D_rAcquiring background signal S of unloaded circuit board to be detected₀；

Step 3, loading a circuit board R to be detected on the detection table T;

step 4, transmitting device D_tSending fingerFixed mode ultra-wideband microwave receiving device D_rAcquiring detection signal S after loading to-be-detected circuit board_R；

Step 5, adopting background subtraction method to detect signal S_RAnd a background signal S₀Calculating a preprocessed signal S_p；

Step 6, adopting a back projection algorithm and according to the preprocessed signal S_pGenerating a circuit board image G to be detected_p；

Step 7, acquiring a position C of a welding spot to be detected according to a printed circuit board layout;

8, according to the position C of the welding spot to be detected, using the image G of the circuit board to be detected_pExtracting image G of welding spot to be detected_C；

Step 9, according to the image G of the welding spot to be detected_CAnd (5) judging the quality of the welding spot according to the fitting degree of the typical value.

In an embodiment of the present invention, the mode of the ultra-wideband microwave specified in step 2 further includes:

the ultra-wideband microwave of a specified mode is a modulated Gaussian pulse E (t), and the mathematical expression of the signal mode is as follows:

wherein f is₀Is the center frequency of the signal, t₀Is the peak time of the signal pulse, t is the sampling time point of the modulated gaussian pulse time e (t), and τ is the pulse width of the signal.

In one embodiment of the present invention, the background signal S in step 2 is₀The method also comprises the following steps:

background signal S₀By the receiving device D_rThe received multiple signal components for the multiple antennas in (1) may be expressed as:

S₀＝(S₀₁，S₀₂，…，S_0i，…，S_0n)

wherein i is the antenna number, S_0iIs the signal received by the ith antennaN is the receiving device D_rThe number of antennas in (1).

In one embodiment of the present invention, the detection signal S in step 4 is_RThe method also comprises the following steps:

detecting signal S_RBy the receiving device D_rThe received multiple signal components for the multiple antennas in (1) may be expressed as:

S_R＝(S_R1，S_R2，…，S_Ri，…，S_Rn)

wherein i is the antenna number, S_RiIs the signal received by the ith antenna, and n is the receiving device D_rThe number of antennas in (1).

In one embodiment of the present invention, the preprocessing signal S in the step 5_pThe method also comprises the following steps:

preprocessing the signal S_pConsists of a number of signal components, which can be expressed as:

S_p＝(S_p1，S_p2，…，S_pi，…，S_pn)

wherein i is the antenna number, S_piIs the signal to be processed of the ith antenna, and n is the receiving device D_rThe number of antennas in (1) is calculated according to the following formula_pi：

S_pi＝S_Ri-S_0i

Wherein i is the antenna number, S_RiA receiving device D for loading the circuit board R to be detected_rSignal received by the ith antenna, S_0iIs not loaded with the front receiving device D of the circuit board R to be detected_rThe signal received by the ith antenna.

In an embodiment of the present invention, the back projection algorithm in step 6 further includes:

step 6.1, dividing the image area into grids of x rows and y columns;

step 6.2, for mesh P_xyCalculating the transmitting device D_tTo the receiving device D_rActual propagation time t in_xy；

And (4) a step 6.3 of,will t_xyComputing the receiving device D as a time input of a time-domain finite difference method_rElectric field amplitude value W of the ith antenna_xyi；

Step 6.4, calculating the corresponding grid P_xyPosition receiving device D_rElectric field amplitude value W of all antennas_xy；

Step 6.5, with the value of electric field amplitude W_xyAs an image G of the circuit board to be inspected_pIn the grid P_xyGenerating an image G of the circuit board to be detected_p。

In one embodiment of the invention, the transmitting device D in step 6.2_tTo the receiving device D_rActual propagation time t in_xyThe method also comprises the following steps:

calculating the actual propagation time t according to the following formula_xy：

Wherein x and y are respectively a line number and a column number after the image area is divided into grids, and l_xy1Is a grid P_xyThickness of position PCB printed circuit board, < i >_xy2Is a transmitting device D_tTo grid P_xyAnd a grid P_xyTo the receiving device D_rAir distance between l_xy3Is a grid P_xyTheoretical thickness of the solder joint or component at location, c is the speed of light in vacuum, ε_rIs the relative dielectric constant, ε, of the circuit board_r1Is a grid P_xyThe relative dielectric constants of the location pads and the components.

In one embodiment of the invention, the corresponding grid P in step 6.4 is_xyPosition receiving device D_rElectric field amplitude value W of all antennas_xyThe method also comprises the following steps:

calculating the electric field amplitude values W of all the antennas according to the following formula_xy：

Wherein x and y are respectively a line number and a column number after the image area is divided into grids, i is an antenna number, and n is a receiving device D_rNumber of antennas in, W_xyiIs a receiving device D_rElectric field amplitude value of the ith antenna.

In one embodiment of the present invention, the step 9 is performed according to the image G of the welding spot to be detected_CAnd the fitting degree with the typical value is used for judging the quality of the welding spot, and the method further comprises the following steps:

the method for judging the degree of fitting is a Support Vector Machine (SVM), and the judging method is as follows:

according to the image G of the welding spot to be detected_CAnd manually judging the label to establish a training set of the SVM;

training the training set, and continuously changing the offset factor to achieve an SVM model with optimized training;

solder joint image G to be detected by using optimized SVM model_CAnd predicting and judging the quality of the welding spot.

(III) advantageous effects

The invention has the beneficial effects that: the welding spot quality detection method based on the ultra-wideband microwaves provided by the embodiment of the invention uses the ultra-wideband microwaves in a specified mode to detect, uses a plurality of antennas to receive detection signals, adopts a back projection algorithm to generate a circuit board image to be detected, further obtains the welding spot image to be detected to be fitted with a typical value, judges the welding spot quality, and solves the problem that the welding spot defect hidden below a component is difficult to effectively, accurately and quickly detect in the prior art.

Drawings

Fig. 1 is a flowchart of a method for detecting quality of a welding spot based on ultra-wideband microwave according to an embodiment of the present invention;

FIG. 2 is a flowchart of a backprojection algorithm in an embodiment of the present invention.

Detailed Description

For the purpose of better explaining the present invention and to facilitate understanding, the present invention will be described in detail by way of specific embodiments with reference to the accompanying drawings.

All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Fig. 1 is a flowchart of a method for detecting solder joint quality based on ultra-wideband microwave according to an embodiment of the present invention, and as shown in fig. 1, the method includes the following steps:

as shown in FIG. 1, in step S110, a testing platform T is provided, and an ultra-wideband microwave signal emitting device D is disposed above the testing platform T_tAn ultra-wideband microwave signal receiving device D is arranged below the microwave signal receiving device_r；

As shown in fig. 1, in step S120, the transmitting device D_tTransmitting ultra-wideband microwave of specified mode, receiving device D_rAcquiring background signal S of unloaded circuit board to be detected₀；

As shown in fig. 1, in step S130, a circuit board R to be inspected is loaded on the inspection table T;

as shown in fig. 1, in step S140, the transmitting device D_tTransmitting ultra-wideband microwave of specified mode, receiving device D_rAcquiring detection signal S after loading to-be-detected circuit board_R；

As shown in FIG. 1, in step S150, a background subtraction method is used to detect the signal S_RAnd a background signal S₀Calculating a preprocessed signal S_p；

As shown in FIG. 1, in step S160, a back projection algorithm is applied according to the preprocessed signal S_pGenerating a circuit board image G to be detected_p；

As shown in fig. 1, in step S170, a solder joint position C to be detected is obtained according to the printed circuit board layout;

as shown in fig. 1, in step S180, according to the position C of the solder joint to be detected, the circuit board image G to be detected_pExtracting the image of the welding spot to be detectedG_C；

As shown in FIG. 1, in step S190, according to the image G of the welding spot to be detected_CAnd (5) judging the quality of the welding spot according to the fitting degree of the typical value.

As shown in fig. 1, in the technical scheme provided by the embodiment of the present invention, ultra-wideband microwaves in a specific mode are used for detection, a plurality of antennas are used for receiving detection signals, a back-projection algorithm is used for generating an image of a circuit board to be detected, and then the image of a solder joint to be detected is obtained to be fitted with a typical value, so as to judge the quality of the solder joint, thereby solving the problem that the defect of the solder joint hidden under a component is difficult to effectively, accurately and quickly detect in the prior art.

The specific implementation of the steps of the embodiment shown in fig. 1 is described in detail below:

in step S110, a test table T is disposed, and an ultra-wideband microwave signal emitting device D is disposed above the test table T_tAn ultra-wideband microwave signal receiving device D is arranged below the microwave signal receiving device_r。

In one embodiment of the invention, a detection table T is required to be arranged for placing the circuit board to be detected, and an ultra-wideband microwave signal transmitting device D is arranged above the detection table_tEmitting device D_tIs used for transmitting the ultra-wideband microwave signal of a specified mode, and an ultra-wideband microwave signal receiving device D is arranged below the ultra-wideband microwave signal receiving device_rReceiving apparatus D_rThe ultra-wideband microwave signal receiving device is used for receiving an ultra-wideband microwave signal penetrating through a circuit board to be detected.

In one embodiment of the invention, the receiving device D_rA gridding structure with a plurality of antennas is adopted, and ultra-wideband microwave signals penetrating through a circuit board to be detected are received and recorded through the plurality of antennas respectively.

In step S120, the device D is transmitted_tTransmitting ultra-wideband microwave of specified mode, receiving device D_rAcquiring background signal S of unloaded circuit board to be detected₀。

In one embodiment of the invention, the transmitting device D_tThe sent ultra-wideband microwave with a specified mode is a modulated Gaussian pulse E (t), and the mathematical expression of the signal mode is as follows:

wherein f is₀Is the center frequency of the signal, t₀Is the peak time of the signal pulse, t is the sampling time point of the modulated gaussian pulse time e (t), and τ is the pulse width of the signal.

In one embodiment of the invention, the background signal S₀By the receiving device D_rThe received multiple signal components for the multiple antennas in (1) may be expressed as:

S₀＝(S₀₁，S₀₂，…，S_0i，…，S_0n)

wherein i is the antenna number, S_0iIs the signal received by the ith antenna, and n is the receiving device D_rThe number of antennas in (1).

In step S130, the circuit board R to be inspected is loaded on the inspection table T.

In one embodiment of the present invention, it is desirable to employ background subtraction based on the detected signal S_RAnd a background signal S₀Calculating a preprocessed signal S_pTherefore, it is necessary to obtain the background signal S of the circuit board R to be detected which is not loaded₀After the circuit board to be detected is loaded, a detection signal S after the circuit board to be detected R is loaded is obtained_RThereafter computing a preprocessed signal S using background subtraction_p。

In step S140, the device D is transmitted_tTransmitting ultra-wideband microwave of specified mode, receiving device D_rAcquiring detection signal S after loading to-be-detected circuit board_R。

In one embodiment of the invention, the signal S is detected_RBy the receiving device D_rThe received multiple signal components for the multiple antennas in (1) may be expressed as:

S_R＝(S_R1，S_R2，…，S_Ri，…，S_Rn)

wherein i is the antenna number, S_RiIs received by the ith antennaN is the receiving device D_rThe number of antennas in (1).

In step S150, a background subtraction method is used to detect the signal S_RAnd a background signal S₀Calculating a preprocessed signal S_p。

In one embodiment of the invention, the signal S is preprocessed_pConsists of a number of signal components, which can be expressed as:

S_p＝(S_p1，S_p2，…，S_pi，…，S_pn)

wherein i is the antenna number, S_piIs the signal to be processed of the ith antenna, and n is the receiving device D_rThe number of antennas in (1) is calculated according to the following formula_pi：

S_pi＝S_Ri-S_0i

Wherein i is the antenna number, S_RiA receiving device D for loading the circuit board R to be detected_rSignal received by the ith antenna, S_0iIs not loaded with the front receiving device D of the circuit board R to be detected_rThe signal received by the ith antenna.

In step S160, a back projection algorithm is applied according to the preprocessed signal S_pGenerating a circuit board image G to be detected_p。

In an embodiment of the present invention, the back projection algorithm in this step has multiple options, but when the back projection algorithm is applied to the detection scene, the detection scene needs to be modeled again for adaptation, a common back projection algorithm is taken as an example in this embodiment, fig. 2 is a flowchart of the back projection algorithm in an embodiment of the present invention, and includes the following steps:

as shown in fig. 2, in step S161, the image area is divided into a grid of x rows and y columns;

as shown in FIG. 2, in step S162, for mesh P_xyCalculating the transmitting device D_tTo the receiving device D_rActual propagation time t in_xy；

As shown in FIG. 2, in step S163, t is set_xyComputing as a time input to a time domain finite difference methodReceiving apparatus D_rElectric field amplitude value W of the ith antenna_xyi；

As shown in fig. 2, in step S164, the corresponding mesh P is calculated_xyPosition receiving device D_rElectric field amplitude value W of all antennas_xy；

As shown in FIG. 2, in step S165, the electric field amplitude value W is used_xyAs an image G of the circuit board to be inspected_pIn the grid P_xyGenerating an image G of the circuit board to be detected_p。

In one embodiment of the present invention, in step S162, the transmitting device D_tTo the receiving device D_rActual propagation time t in_xyThe method also comprises the following steps:

calculating the actual propagation time t according to the following formula_xy：

Wherein x and y are respectively a line number and a column number after the image area is divided into grids, and l_xy1Is a grid P_xyThickness of position PCB printed circuit board, < i >_xy2Is a transmitting device D_tTo grid P_xyAnd a grid P_xyTo the receiving device D_rAir distance between l_xy3Is a grid P_xyTheoretical thickness of the solder joint or component at location, c is the speed of light in vacuum, ε_rIs the relative dielectric constant, ε, of the circuit board_r1Is a grid P_xyThe relative dielectric constants of the location pads and the components.

In one embodiment of the present invention, in step S164, the corresponding grid P_xyPosition receiving device D_rElectric field amplitude value W of all antennas_xyThe method also comprises the following steps:

calculating the electric field amplitude values W of all the antennas according to the following formula_xy：

Wherein x and y are respectively a line number and a column number after the image area is divided into grids, i is an antenna number, and n is a receiving device D_rNumber of antennas in, W_xyiIs a receiving device D_rElectric field amplitude value of the ith antenna.

In step S170, a solder joint position C to be detected is obtained according to the printed circuit board layout.

In an embodiment of the invention, the position C of the solder joint to be detected needs to obtain accurate positioning information from the printed circuit board layout, and the detection area of the solder joint to be detected can be obtained by appropriately enlarging the size of the solder joint according to the accurate positioning information and the size of the solder joint set by the printed circuit board layout.

In step S180, according to the position C of the solder joint to be detected, the circuit board image G to be detected_pExtracting image G of welding spot to be detected_C。

In one embodiment of the invention, after the detection area of the welding spot to be detected is obtained from the welding spot position C to be detected, the circuit board image G to be detected is obtained according to the position of the detection area_pExtracting image G of welding spot to be detected_C。

In step S190, according to the image G of the welding spot to be detected_CAnd (5) judging the quality of the welding spot according to the fitting degree of the typical value.

In an embodiment of the present invention, the method for determining the degree of fit in this step is divided into a classifier based on features and a method for machine learning, and in this embodiment, for example, a Support Vector Machine (SVM) in machine learning is used to determine the quality of a weld spot, and the method for determining the quality of a weld spot based on a support vector machine specifically includes:

firstly, according to the image G of the welding spot to be detected_CAnd manually judging the label to establish a training set of the SVM; secondly, training the training set, and continuously changing the offset factor to achieve an SVM model with optimized training; finally, the optimized SVM model is utilized to detect the welding spot image G_CAnd predicting and judging the quality of the welding spot.

In summary, the invention provides a welding spot quality detection method based on ultra-wideband microwave, which solves the problem that the welding spot defect hidden under a component is difficult to effectively, accurately and quickly detect in the prior art.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

It will be understood that the invention is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.