CN104729961A

CN104729961A - Method for detecting particles in anisotropic conductive film

Info

Publication number: CN104729961A
Application number: CN201510140140.3A
Authority: CN
Inventors: 刘霖; 谢煜; 胡勇; 何岗; 梁翔; 刘鹏; 张静; 刘娟秀; 倪光明; 叶玉堂; 刘永
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2015-03-27
Filing date: 2015-03-27
Publication date: 2015-06-24
Anticipated expiration: 2035-03-27
Also published as: CN104729961B

Abstract

The invention discloses a method for detecting particles in an anisotropic conductive film; the method is applied to automatic optical inspection of activated carbon fiber (ACF) particles in the manufacturing process of a chip on glass (COG) or fiber optic gyroscope (FOG); the invention particularly relates to a method for detecting the pressed conductive particles. The method comprises the steps of merging characteristics according to the gray scale and the position characteristic of a particle image; carrying out quantification on the gradient field to avoid a great deal of data operation, wherein the operation speed can completely catch up with the actual production rhythm. The method is very high in detection accuracy rate and is capable of replacing manual electrical detection and microscope detection, thus being widely applied to the automatic optical inspection in the production process of the COG and the FOG.

Description

The detection method of particle in a kind of anisotropic conductive film

Technical field

Be applied to the ACF particle automatic optical detection method in COG, FOG processing procedure, particularly detect the conducting particles of compacting.

Background technology

Liquid crystal display except liquid crystal panel, its peripheral must interlock driving chip as the control purposes of display signal.COG is the abbreviation of chip on glass, and namely chip is directly bundled on glass; FOG is the abbreviation of FPC on Glass.Both for the processing mode of liquid-crystalline glasses and circuit electrical conducting.

ACF is the abbreviation of Anisotropic Conductive Film (anisotropic conductive film), and its feature is that the resistance characteristic of Z axis electrically conducting direction and XY insulating planar has obvious otherness.After the difference of Z axis conduction resistance value and XY planar insulative resistance value exceedes certain ratio, both can be described as good conduction anisotropy.Conductivity principle utilizes conducting particles connection IC chip and substrate electrode between the two to make it to become conducting, can avoid again conducting short circuit between adjacent two electrodes simultaneously, and reach only in the object of Z-direction conducting.

COG processing procedure utilizes to cover crystalline substance (Flip Chip) conduction mode, wafer directly aimed at the electrode on glass substrate, utilizes ACF material as the dielectric surface material engaged, make the electrode conduction of two kinds of binding object vertical direction.

The whether qualified main employing of conducting particles two kinds of methods detect in present liquid crystal manufacturer, and one is electric test, and another kind is the imaging directly observing particle under the microscope.Namely electric test connects testing power supply to LCD screen, and whether measuring current and voltage reach requirement.Directly observe under microscope test and staff take microscope liquid crystal display, see whether particle is suppressed qualified.(context of methods principle is the same with microscope test, is all to carry out analysis to particle imaging to judge), two kinds of methods are all need manually to test every a slice screen, and efficiency is low, and cost is high.

Summary of the invention

The present invention is directed to the deficiency of background technology, technical matters to be solved is a kind of simple to operate, automatic optical detection method of detecting after the compacting of ACF particle whether validity fast and effectively of design, validity and effective particle number of particle reach requirement, can meet conduction requirement.

The detection method of particle in a kind of anisotropic conductive film of the present invention, the method comprises:

Step 1: utilize line-scan digital camera to gather particle picture in anisotropic conductive film, the particle picture be amplified, and direction of illumination during records photographing image;

Step 2: denoising is carried out to the image collected;

Step 3: adopt histogram equalization method to carry out greyscale transformation to denoising image, obtain gray level image;

Step 4: adopt direction of illumination differential technique to process the gray level image that step 3 obtains; Direction of illumination is the direction of illumination that step 1 records;

Step 5: binary conversion treatment is carried out to the image that step 4 obtains, obtaining background is black, and particle is the image of white, calculates particle number thus;

Step 6: obtain white portion position in image according to step 5, determining step 4 processes particle position in rear image;

Step 7: adopt Laplace operator to obtain the gradient fields of each particle in step 6, judge that whether particle is qualified; Set a threshold value according to illumination and environmental change, it is then qualified that the gradient fields calculated is greater than threshold value, is less than then defective.

The concrete grammar of the direction of illumination differential technique of described step 4 is: choose a pixel, then finds this pixel along the gray-scale value minimum value within the scope of 1 ~ D on direction of illumination; By the gray-scale value of selected pixels point and the gray-scale value of this minimum point poor, the difference obtained is composed as the new gray-scale value of selected pixels point; Wherein the value of D is determined according to the size of real image particle, and particle in the picture radius is r, then D value is in 2*r ± 2.

The detection method of particle in a kind of anisotropic conductive film of the present invention, the method, according to the gray scale of particle picture and position feature, carries out feature merging, then by the quantification of gradient fields, avoid a large amount of data operations, arithmetic speed can be caught up with actual productive temp completely.It is very high that this method detects accuracy, can replace artificial electric detection and microscopic examination, can be widely used in the automatic optics inspection in COG and FOG production.

Accompanying drawing explanation

Fig. 1 is the particle picture collected;

Fig. 2 is the image after adopting the process of direction of illumination differential technique;

Fig. 3 is the curve synoptic diagram of the rear particle properties of former figure and process.

Embodiment

Below in conjunction with accompanying drawing, the present invention is further detailed.

Step 1: build motion platform as liquid crystal display objective table, PLC parametric controller moves, and utilize the line-scan digital camera that rate is respectively 0.7um to gather image, the camera lens of adding 10 times amplifies, and records direction of illumination.

Step 2: utilize medium filtering to remove high frequency noise, get the scope that medium filtering template is 3 × 3.

Step 3: histogram equalization is divided into 3 steps:

Step 3.1: the number of times that each gray level of statistic histogram occurs;

Step 3.2: accumulative normalized histogram;

Step 3.3: calculate new pixel value, computing formula is as follows

h (v) = round (\frac{f (v) - f_{\min}}{(M \times N) - f_{\min}} \times (L - 1));

H (v) represents that gray-scale value is the new gray-scale value of v, and f (v) represents that gray-scale value is the accumulative occurrence number of v, f _minrepresent that the number of times that gray-scale value occurrence number is minimum, M × N represent that the length and width of image are amassed, L is number of greyscale levels, and image bit is 8 deeply, then number of greyscale levels is 2^8=256.

Step 4: direction of illumination differential technique process image, the direction of illumination that input step 1 records, then recalculates the gray-scale value of pixel according to the direction of illumination.

Step 5: the image particle characteristics after difference is quite obvious, OTSU binaryzation obtains particle region, in order to determine particle position, the method of local maximum is adopted to judge, template with one 5 × 5 carries out the traversal of particle region, when the central point of template is maximum value, and the minimizing difference within the scope of the gray-scale value of maximum value and template is when being greater than given threshold value, also maximum value situation is there is at smooth region in this threshold value for rejecting image, then think and find a particle, particle position is the center of current template.

Step 6: Laplace operator computing is done to the particle found, obtain the quantized values of a particle gradient fields, when numerical value is larger, illustrate that particle compacting is better, numerical value is less, illustrates that the feature of particle is not clearly, there is the situation that vacation is pressed or particle is crushed, this is all defective particle, needs to get rid of.

The Laplace operator adopted is the template of 3 × 3, judges, be greater than threshold value and think qualified particle, be less than, be not for particle whether qualified use threshold value.Whether liquid crystal display is qualified is exactly whether the qualified population judged on each pin reaches requirement.

As can be seen from Figure 3 particle is without the feature of the bright dark change in original graph, but become and only have brighter feature, and this brightness contrast is in the drawings more much larger than the contrast of dividing compared with highlights in original graph, so this brighter feature in particle local is more prone to extract relative to original graph.This is because after making difference by the gray scale minimal value of current pixel and direction of illumination, brighter areas in figure is just with in figure, comparatively dark areas is poor, the brighter areas obtained like this is just more outstanding than former figure, more easily identify, and bright dark two feature unifications before above a feature, make whole identifying more succinct, quick like this.

Claims

1. the detection method of particle in anisotropic conductive film, the method comprises:

Step 2: denoising is carried out to the image collected;

2. the detection method of particle in a kind of anisotropic conductive film as claimed in claim 1, it is characterized in that the concrete grammar of the direction of illumination differential technique of described step 4 is: choose a pixel, then find this pixel along the gray-scale value minimum value within the scope of 1 ~ D on direction of illumination; By the gray-scale value of selected pixels point and the gray-scale value of this minimum point poor, the difference obtained is composed as the new gray-scale value of selected pixels point; Wherein the value of D is determined according to the size of real image particle, and particle in the picture radius is r, then D value is in 2*r ± 2.