Foshan flexible circuit board defect detection method guide is as follows

There are many classification methods for FPC products of flexible circuit board. According to the number of laminating layers of flexible circuit board, it can be divided into: single flexible circuit board FPC, double-sided flexible circuit board FPC board, multi-layer flexible circuit board FPC board and soft-hard combination board.  As a common type of circuit board, the market share of FPC is rising with the development of electronic products to miniaturization and portability.  However, FPC of flexible circuit board may have defects such as circuit break, short circuit and line width discrepancy in the process of processing, loading and mounting.  In view of this, this paper mainly analyzes FPC defect detection method of flexible circuit board.  

Different production technology makes it has many unique characteristics:  

(1) The FPC assembly density of the flexible circuit board is high, which reduces the connection between parts;  

(2) The flexible CIRCUIT board FPC has light weight and thin thickness, which can effectively reduce the weight of the product and is convenient to carry;  

(3) The FPC flexible circuit board can be folded and bent arbitrarily.  

Flexible CIRCUIT board FPC has the advantages of good reliability, strong heat dissipation, easy installation and low comprehensive cost, which provides convenience for the high integration and high performance of electronic products.  

There are many classification methods for FPC products of flexible circuit board. According to the number of laminating layers of flexible circuit board, it can be divided into single-sided flexible circuit board FPC, double-sided flexible circuit board FPC, multi-layer flexible circuit board FPC and soft and hard combination board.  

Development status of FPC defect detection technology for flexible circuit board  

The existing FPC defect detection algorithm of flexible CIRCUIT board is mostly derived from PCB detection algorithm. However, due to the limitation of its uniqueness, FPC defect detection algorithm of flexible circuit board has higher accuracy requirements, larger detection sample size, and easy deformation of sample image. Therefore, the defect detection algorithm for PCB board cannot directly apply FPC detection algorithm of flexible circuit board.  It is necessary to develop a suitable detection algorithm according to the actual circuit characteristics of FPC flexible circuit board.  

China metrology institute of the traditional problem of slow speed and low accuracy of template matching algorithm, the proposed flexible PCB FPC line defects can be divided into two categories, global and local defect, eight connected domain area method combined with global histogram matching method to capture image defects, on the basis of projection matching and correlation coefficient method is used to identify local defect of the image.  This method is faster and more accurate than traditional detection algorithms, but the classification of related defect categories is not detailed enough.  

Analysis of FPC defect detection method for flexible circuit board  

For the global template matching problem, the local template matching method is considered to implement FPC defect detection of FPCB.  Considering the contour based template matching method, the template should have significant contour characteristics. Although the conventional lines on the flexible circuit board have regular trend, they have no significant shape characteristics. Moreover, the conventional lines are distributed in the whole image, and the large template matching time is too slow, which is not conducive to line detection.  

Special-shaped circuit belongs to the irregular shape on the flexible circuit board, generally including LED lights, S-shaped circles, etc.  Due to the shape of peripherals, the wiring is generally related to the FPC style structure of the flexible circuit board to be inspected.  For this kind of line, the template matching method is considered to implement detection: firstly, the position and pose of each special-shaped line on the FPC of the whole flexible circuit board are located by rough step of template matching method, and the contour of special-shaped line is obtained.  Then defect detection was carried out based on morphology theory.  

FPC Defect Detection method guide for flexible circuit boards  

(1) Load the data information related to the registration template, including the registration template area and profile information.  

(2) Using the regional information carried by the registered template, locate the template search space, and search the template instance in the search image based on the metric principle of normalized Correlation number (NCC).  

(3) Cut the irregular area.  The size of the special-shaped region is obtained by taking the smallest enclosing rectangle of the shape template instance. Since the shape template is a rectangular region, the region obtained by the smallest enclosing rectangle is the matched special-shaped region.  Arbitrary template matching cannot make two images perfectly aligned in space, there is a match within a permissible range.  Due to the reduction of the space range, the matching accuracy of the shape template is improved. The overall matching error is about 1/5 line width (3 pixels), which is within the allowable range of defect determination.  

(4) Considering the precision error of shape matching, before the difference between the standard template image and the image of the irregular region is calculated directly, corrosion operation is carried out on the irregular region by small size structural elements to remove the influence of boundary difference.  When there are defects in the image, the corrosion operation at this size cannot completely corrode the defective line, so the final judgment result is not affected.  

(5) Regional difference set calculation is carried out between the template image and the irregular region to obtain the difference region of the two.  When there is no defect, the difference is 0.  When there is a defect, the region difference set returns a binary image which is not 0.  

(6) Mark the connected domain of the difference image to segment different defect blocks;  

(7) Calculate the area of each connected domain, and take the geometric size center of the largest defect block as the center of the irregular region to output the defect information.  

The FPC flexible circuit board defect detection method is studied from the global and local scope, and experimental conclusions are drawn:  

(1) Due to the FPC imaging deformation of the flexible circuit board, the template matching circuit based on the global scope is misaligned, and the defect information on the image cannot be correctly located.  

(2) Based on local template matching, firstly cut out the FPC flexible circuit board has significant shape characteristics compared with the conventional circuit, and take it as the template;  Instance detection is performed near the corresponding template area on the search image to compress the search space.  Then the line defect information is detected based on morphology theory.  

In short, as the most basic component of electronic circuit, the FPC of flexible circuit board greatly affects the quality of the entire electronic products.  Therefore, how to implement precision of circuit board defect detection is an important link of the product quality assurance, and most domestic enterprises commonly rely on artificial visual to FPC flexible circuit board defect detection, high cost and low efficiency, and because there is no relative standard quality inspection standards, staff by reason of subjective consciousness or visual fatigue prone to leak and mistakenly identified;  Due to the limitations of equipment price, technical support and after-sales service, the excellent foreign testing equipment introduced by some enterprises is difficult to adapt to the low cost and mass production needs of modern technology.  Therefore, it is extremely urgent to develop a fast and efficient FPC defect automatic detection system to meet the needs of the domestic market.  

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