KR100229070B1 - Inspection method and device of cream solder of pcb - Google Patents

Abstract

An apparatus and method for cream lead inspection of a printed circuit board is disclosed. The apparatus includes optical calculation means for repeatedly acquiring, storing and outputting images of cream lead and images of the transferred cream lead by photographing the cream lead, and positioning for moving the optical calculation means three-dimensionally in response to the position control signal. Means, a printed circuit board conveying means for moving, stopping, or discharging the printed circuit board to be measured in response to the conveyor control signal, and generating a position control signal and a conveyor control signal, and using the images input from the optical calculation means, It is characterized in that it comprises a control means for calculating the height, it is possible to measure the height and volume of the cream lead with a high resolution of 1㎛ level, it is possible to calculate the high reliability printing conditions using the analysis results of the current printing conditions and printing conditions Easy-to-use, high speed and high resolution line cream lead test enables It is possible to improve the productivity and reliability of the final product by drastically reducing defects in the parts mounting process and the soldering process, which can produce the plate and are closely related to the subsequent printing process.

Description

Cream lead inspection apparatus and method of printed circuit board

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to printed circuit board inspection, and more particularly, to an apparatus and method for cream lead inspection of a printed circuit board capable of calculating the height and volume of the cream lead of the printed circuit board.

Hereinafter, with reference to the accompanying drawings, the configuration and operation of a cream lead inspection apparatus of a conventional printed circuit board will be described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view for explaining a cream lead inspection apparatus of a conventional printed circuit board, and includes a line projector 10, a galvano mirror 12, a motor 14, and a solid-state imaging device. Charged Coupled Device (CCD) camera 16, slit beam 18, solder paster 20, Printed Circuit Board (PCB) 22 and monitor 24 It is composed.

The line projector 10 shown in FIG. 1 performs a function of generating slit light and projects one line. Depending on the manufacturing company, several lines may be created simultaneously to improve speed. The galvano mirror 12 causes the slit light emitted from the line projector 10 to be bent at an angle. Here, the slit light is moved from one end of the cream lead 20 to the other end. As a result, the entire area of the cream lead 20 is scanned. Meanwhile, the motor 14 rotates the galvano mirror 14, and the CCD camera 16 acquires an image of the slit beam 18 formed on the cream lead 20. At this time, the shape of the image acquired by the CCD camera 16 appears as if drawn on the monitor 24. Because the line projector 10 is scanned obliquely with respect to the PCB substrate 22 serving as a reference plane, the waveforms as shown in the monitor 24 appear in the vertically mounted CCD camera 16. The controller (not shown) calculates height information by processing and analyzing the image. The height at this time can be simply calculated by generally known optical trigonometry.

That is, the print evaluation device or the cream lead tester shown in FIG. 1 installed behind a screen printer to check the printing state mainly performs two-dimensional inspection in-line, and some averages three-dimensional inspection but one. It is impossible to track the printing conditions to measure the height level only.

Therefore, the above-described conventional cream lead inspection apparatus of a printed circuit board takes a considerable time when the height is measured by continuously scanning the entire area of the cream lead 20, so in the case of in-line equipment, Measurement is made at three or more sampling points, but this results in a decrease in measurement reliability. In addition, since the line width of the slit beam 18 is limited, there is a limit in reducing the pitch of the sampling point and there is a problem that it is difficult to increase the measurement resolution. In addition, the point laser must be used to obtain a resolution of 1㎛ moisture, which takes a considerable time to measure, there is an unsuitable problem when installed in the in-line equipment.

An object of the present invention is to provide a cream lead inspection apparatus of a printed circuit board for measuring the volume and height of the cream lead of the printed circuit board printed through a screen printer at high speed and with high accuracy.

Another object of the present invention is to provide a cream lead inspection method of a printed circuit board performed in the cream lead inspection apparatus of the printed circuit board.

1 is a view for explaining a cream lead inspection device of a conventional printed circuit board.

2 is a block diagram of a cream lead inspection apparatus of a PCB according to the present invention.

3 is a block diagram according to the present invention of the optical calculation unit shown in FIG.

FIG. 4 is a flowchart for explaining a cream lead test method according to the present invention performed in the apparatus shown in FIG. 2.

The cream lead inspection apparatus of a printed circuit board according to the present invention for achieving the above object, the optical lead means for photographing the cream lead repeatedly obtained, stored and output the image of the cream lead and the transferred cream lead, and Position adjusting means for three-dimensionally moving the optical calculation means in response to a position control signal, printed circuit board conveying means for moving, stopping or discharging the printed circuit board to be measured in response to a conveyor control signal and the position control signal And control means for generating the conveyor control signal and calculating the height of the cream lead using the images input from the optical calculation means.

In order to achieve the above another object, the cream lead test method according to the present invention, which is composed of a telecentric projection moiré, is performed in a cream lead test apparatus of a printed circuit board that calculates the volume of the cream lead according to a phase shift amount. Obtaining an image of the printed circuit board, removing noise from the obtained image, detecting an edge component from the image from which the noise is removed, and extracting an area for the cream lead; Determining whether to examine the volume of the cream lead or the height of the cream lead; and, if the volume of the cream lead is to be examined, calculating contour data, calculating area and centers, and calculating shape data about the volume. In order to examine the height of the cream lead, calculate the light intensity distribution and the measurement phase at the measuring point, and phase Calculating shape data with respect to height by aligning, determining whether the shape data is greater than or equal to a reference value, and determining that the printed state of the printed circuit board is poor if the shape data is greater than or equal to the reference value; and If shape data is below the said reference value, it is preferable to consist of a step which determines that the printing state of the said printed circuit board is favorable.

EMBODIMENT OF THE INVENTION Hereinafter, the structure and operation | movement of the cream lead test | inspection apparatus of the printed circuit board by this invention are demonstrated as follows with reference to attached drawing.

FIG. 2 is a block diagram of a cream lead inspection apparatus of a PCB according to the present invention. An optical calculation unit repeatedly photographs the cream lead on the PCB 46 and repeatedly acquires, stores and outputs the image of the cream lead and the transferred cream lead. 40), the position adjusting unit 42 and 44 which can be implemented as a two-axis robot and moves the optical calculation unit 40 three-dimensionally in response to the position control signal, the printed circuit board to be measured in response to the conveyor control signal , The conveyor 48, the stopper 50, the stopper cylinder 52, the sensor 50 and the drive motor 54, the substrate 46 to be inspected, and the cream lead constituting the PCB carrier to stop or discharge. The first display unit 56 for displaying information about the second display unit 58, the frame grabber 60, the illumination control unit for controlling the brightness of the camera to display the image taken by the optical calculation unit 40 62, movement control signal The moving control unit 64 generated, the position control unit 66 generating the position control signal, and the image signal input from the camera are analyzed to calculate the height of the cream lead, and the position control unit 66, the conveyor control unit 70, and the lighting control unit. And a main control unit 68 for controlling the moving control units 64 and a conveyor control unit 70 for generating a conveyor control signal in response to the main control signal.

The apparatus shown in FIG. 2 is first controlled by the main controller 68 and the conveyor controller 70. When the conveyor 48 is driven by the drive motor 54, the substrate 56 to be measured enters the inspection position. Arrival at the test position is detected by the sensor 50 and the stopper cylinder 52 is raised to stop the flow of the substrate 46. In this case, the conveyor controller 70 outputs a signal to start the inspection because the substrate has arrived at the main controller 68.

On the other hand, the main controller 68 outputs a position control signal to the position controller 66 for controlling the position adjusters 42 and 44 so that the substrate 46 moves to the inspection position. Under the control of the position adjusting units 42 and 44, when the substrate 46 arrives at the inspection position and the image is captured by the optical calculating unit 40, the main control unit 68 receives an image signal from the optical calculating unit 40. Control to be stored in the frame grabber 60.

3 is a block diagram according to the present invention of the optical calculation unit 40 shown in FIG. 2, which is an image constituting an image forming unit and a light source 82, a projection grating 88, and a projection lens 90. It consists of the camera 80 which picks up a moiré pattern, the microscope tube 92, the reference grating 94, and the imaging lens 98. As shown in FIG. Here, reference numeral 84 denotes an optical calculation unit, 86 denotes a moving unit for minutely moving the two gratings 88 and 94 for phase transfer, and 96 denotes a PCB substrate 96, respectively.

Before explaining the optical calculation unit 84 shown in FIG. 3, the operating principle of the present invention will be described as follows.

First, before calculating the cream lead, it is assumed that the moiré pattern generated by the beat phenomenon when two or more periodic patterns overlap, and the height information is extracted by analyzing the moiré pattern generated by the photophase interference method. In the present invention, a projection moiré is applied among various moiré generation methods most frequently used in measuring a three-dimensional shape of an object. The principle is that the moiré pattern is formed on the reference grid by scanning the moiré grid on the object surface to be measured using a projector and imaging the deformed grid changed according to the shape of the object on the reference grid using an imaging lens.

Projection-type moire is a method that can easily measure relatively large area by non-contact, but it has lower visibility than shadow type, so the measurement resolution is slightly lowered. There is a problem in that the tilt occurs with respect to the absolute coordinate system of the object. To eliminate this phenomenon, it is necessary to construct a telecentric projection moiré system in which the optical systems of the imaging system and the lighting system are exactly coincident and the optical axes of each other are kept in parallel.

That is, the telecentric projection moiré is composed of the illumination optical system and the imaging optical system symmetrically to each other in the same system, to scan the moire grating on the measurement object, and uses a 55mm macro lens to form the image. Here, the reason why the macro lens is used is that the distance between the object and the measured object is at least 250 mm, and 5 times the magnification is used. In addition, in order to increase the measurement resolution, the smaller the distance between the measuring object and the probe, the more advantageous. This is because the projection lens 90 and the imaging lens 98 satisfying such structural requirements are aberrations corrected at close range as a macro lens.

On the other hand, the basic concept of a phase shift interferometer is to find out from the interference fringe formed the optical path difference between the desired measurement wave and the reference wave by giving a time-shifted phase transfer between the reference wave and the measurement wave used in the interferometer. That is, the light intensity of the interference fringe changes as the phase transfer is performed at one measurement point, and the height information of the surface to be measured can be obtained by calculating the amount of phase shift proportional to the height information by using this. This is called a phase shift method.

In order to achieve phase shift in the projection moiré, relative movement between the reference grating 94 and the projection grating 88 is performed. In the case of the phase shifting method by the lattice transfer, the reference lattice 94 shifts the distance of one pitch of the lattice by 5 or 6 equal parts according to the measurement algorithm. If the reference grating 94 is 40 lines / mm, it must move on a stage 86 capable of driving resolution in units of μm to divide 25 μm into 5 and 6 equal parts. Constraints in movement should be that both gratings are in the same plane even after they are moved, and that the grating moved relative to the projection grating 88 should be free of relative rolling, pitching, and yawing.

Based on the above-described principle, the operation process of the optical calculation unit 40 shown in FIG. 3 is as follows. That is, once the optical calculation unit 40 is completed to move to the designated position in the device shown in Figure 2, the camera 80 obtains a single image (hereinafter referred to as grabbing or less). The obtained video signal, that is, the moiré image, is stored in the frame grabber 60 shown in FIG. In order to perform the phase shift, a motor built in the moving unit 86 is driven to transfer the projection grating 88 and the reference grating 94 by a small amount. Then grab again. After repeating this process five or six times, the moiré image repeated until this time is continuously stored in the frame grabber 60 shown in FIG. 2.

The main controller 68 reads the image information stored in the frame grabber 60 continuously, analyzes the moire interference fringe, calculates the amount of phase shift, and calculates the height of the object therefrom. The calculated result is shown in the first display unit 56. Once the inspection of the designated position on the PCB 46 is made, the optical calculation unit 40 is moved to the next position, and the above-described process is repeated to complete the inspection of the entire area of the substrate 46. When the inspection is completed, the main control unit 68 sends a signal to the conveyor control unit 70 that the inspection is completed, and the conveyor control unit 70 receives the lowering of the stopper cylinder 52 and drives the conveyor driving motor 54. The test is finished by discharging the test board 46.

On the other hand, the main control unit 68, the lighting control unit 62 for adjusting the brightness of the illumination, the movement control unit 64 for the phase shift, and the frame grabber 60 for storing the moiré pattern detected from the camera 80 as image information. Under the control of, perform the corresponding function.

EMBODIMENT OF THE INVENTION Hereinafter, with reference to the accompanying drawing, the cream lead test | inspection method of the printed circuit board by this invention is demonstrated as follows.

4 is a flowchart illustrating a cream lead test method according to an embodiment of the present invention performed in the apparatus shown in FIG. 2, wherein an image is obtained from a PCB to remove noise (steps 200 to 204), and Extracting the area of the image and extracting the shape data according to the target to be inspected (steps 206 to 212), comparing the shape data with a reference value to determine the quantity / badness of the print state (steps 214 to 218); Comprising a step of calculating the height or area (220 and 222).

First, an image is acquired through the optical calculator 40, which is a measurement head (S200). The following process is performed to extract the cream lead region of the PCB substrate 46 through the image processing unit installed in the main controller 68. That is, since the shadows engraved on the grids 88 and 94 appear in the form of stripes in the image accumulated through the head, and may act as noise in the image interpretation thereof, fast fourier transform (FFT) analysis and inverse FFT (IFFT) analysis. In operation 202, an image from which the grid shadow which is a periodic noise component is removed is obtained.

After step 202, a series of preprocessing processes, such as filtering to remove various noises, are performed because there are irregular noises that interfere with image analysis even through the obtained image (step 204). After operation 204, an edge is extracted from the obtained image, and only an area corresponding to cream lead is extracted (operation 206). After step 206, it is determined whether to calculate the volume or the height of the cream lead (step 208). If the volume of the cream lead is to be calculated, the contour of the extracted lead region is extracted, and the shape data is extracted by calculating the area and the center (step 210). However, in order to calculate the height of the cream lead, in order to obtain three-dimensional information, the light intensity distribution is calculated for the lead region, that is, the corresponding coordinate point in the region corresponding to lead, the calculated phase is calculated, and then the phase In operation 212, shape data that is three-dimensional image information is obtained by aligning. In step 212, there are a variety of known methods for calculating the measurement phase, but the random interval phase transfer measurement is used here.

After step 210 or step 212, that is, after extracting the shape data, it is determined whether the shape data is equal to or greater than the reference value (step 214). If the shape data is larger or narrower than the reference value, the printout of the inspected PCB is determined to be defective by considering the case of being out of center and the like (step 216). However, if the shape data is within the reference value, it is determined that the printing state is good (step 218).

After step 218, the average height of lead may be calculated using three-dimensional height information, and the volume (average height * area) is measured in combination with the results obtained in the two-dimensional measurement (step 220). After step 220, a unique number is assigned to each pad, and the two-dimensional and three-dimensional measurement results are connected to the corresponding pads of the stored file and stored in a file in the main controller 68 (step 222).

As described above, the cream lead inspection device and method of the printed circuit board according to the present invention can measure the height and volume of the cream lead with a high resolution of 1㎛ level, using the analysis results of the current printing conditions and printing conditions It is easy to calculate high reliability printing conditions, and enables high speed and high resolution line cream lead inspection, which enables the production of saddle PCB boards and defects in parts mounting and soldering processes that are closely related to subsequent printing processes. Significantly reduced, there is an effect that can improve the productivity and reliability of the final product.

Claims (12)

In the cream lead inspection device of a printed circuit board, Optical calculation means for photographing the cream lead and repeatedly acquiring, storing, and outputting the image of the cream lead and the images of the transferred cream lead; Position adjusting means for moving the optical calculating means three-dimensionally in response to a position control signal; Printed circuit board conveying means for moving, stopping or discharging the printed circuit board to be measured in response to a conveyor control signal; And And a control means for generating the position control signal and the conveyor control signal and calculating the height of the cream lead using the images inputted from the optical calculation means. The cream lead inspection apparatus of claim 1, wherein First display means for displaying information on the height of the cream lead calculated by the control means; And Cream lead inspection apparatus for a printed circuit board further comprises a second display means for displaying an image taken by the optical calculation means. The method of claim 1, wherein the optical calculation means Light source; A projection grating for passing light generated from the light source; A projection lens for irradiating the cream lead with the light passing through the projection grating; An imaging lens for passing an image changed according to the shape of the cream lead; A reference grating positioned horizontally with the projection grating to form the image passing through the imaging lens; A camera for picking up an image formed on the reference grid; A microscope probe positioned between the camera and the reference grating; And And moving means for moving the projection grating and the reference grating in a horizontal direction in response to a movement control signal in a horizontal direction. The printed circuit board of claim 1, wherein the optical calculation means comprises a telecentric projection moiré, and the control means calculates the height of the cream lead according to a phase shift amount. Cream lead test device. The method of claim 4, wherein the control means Position control means for generating the position control signal; Conveyor control means for generating the conveyor control signal in response to a main control signal; Illumination control means for controlling illumination brightness of the camera; Movement control means for generating the movement control signal; And And a main control means for analyzing the image signal input from the camera to calculate the height of the cream lead and controlling the position control means, the conveyor control means, the illumination control means and the movement control means. Cream lead inspection device on a printed circuit board. In the cream lead inspection device of a printed circuit board, Optical calculation means for photographing the cream lead and repeatedly acquiring, storing and outputting the image of the cream lead and the images of the transferred cream lead; Position adjusting means for moving the optical calculating means two-dimensionally in response to a position control signal; Printed circuit board conveying means for moving, stopping or discharging the printed circuit board to be measured in response to a conveyor control signal; And And a control means for generating the position control signal and the conveyor control signal and calculating the volume of the cream lead using the images output from the optical calculation means. The cream lead inspection apparatus of claim 6, wherein First display means for displaying information on the volume of the cream lead calculated by the control means; And Cream lead inspection apparatus for a printed circuit board further comprises a second display means for displaying an image taken by the optical calculation means. The method of claim 6, wherein the optical calculation means Light source; A projection grating for passing light generated from the light source; A projection lens for irradiating the cream lead with the light passing through the projection grating; An imaging lens for passing an image changed according to the shape of the cream lead; A reference grating positioned horizontally with the projection grating to form the image passing through the imaging lens; A camera for picking up an image formed on the reference grid; A microscope probe positioned between the camera and the reference grating; And And moving means for moving the projection grating and the reference grating in a horizontal direction in response to a movement control signal in a horizontal direction. 9. The printed circuit board of claim 6 or 8, wherein the optical calculation means comprises a telecentric projection moire, and the control means calculates the height of the cream lead according to the amount of phase shift. Cream lead test device. The method of claim 9, wherein the control means Position control means for generating the position control signal; Conveyor control means for generating the conveyor control signal in response to a main control signal; Illumination control means for controlling illumination brightness of the camera; Movement control means for generating the movement control signal; And And a main control means for analyzing the image signal input from the camera to calculate the volume of the cream lead and to control the position control means, the conveyor control means, the illumination control means and the movement control means. Cream lead inspection device on a printed circuit board. In the cream lead inspection method which is composed of a telecentric projection moire, the cream lead inspection apparatus of the printed circuit board to calculate the volume of the cream lead in accordance with the amount of phase shift, Acquiring an image of the printed circuit board; Removing noise from the obtained image; Detecting an edge component from the noise-free image and extracting an area for the cream lead; Determining whether to examine the volume or height of the cream lead; If the volume of the cream lead is to be examined, calculating contour data, calculating area and center, and calculating shape data about the volume; Calculating a light intensity distribution and a measurement phase at a measurement point when calculating the height of the cream lead, and arranging phases to calculate shape data of the height; Determining whether the shape data is equal to or greater than a reference value; If the shape data is equal to or larger than the reference value, determining the print state of the printed circuit board as being bad; And And determining that the printed state of the printed circuit board is good if the shape data is less than or equal to the reference value. The method of claim 11, wherein the cream lead test method of the printed circuit board After determining that the printing state is good, calculating the height or the area using the shape data; And And assigning and storing a unique number in the calculated height or area.

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