CN109785316A - A kind of apparent defect inspection method of chip - Google Patents

A kind of apparent defect inspection method of chip Download PDF

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CN109785316A
CN109785316A CN201910061382.1A CN201910061382A CN109785316A CN 109785316 A CN109785316 A CN 109785316A CN 201910061382 A CN201910061382 A CN 201910061382A CN 109785316 A CN109785316 A CN 109785316A
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pin
centroid
vector
angle
image
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CN109785316B (en
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袁小芳
刘琛
田争鸣
王浩然
陈祎婧
肖祥慧
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Hunan University
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Abstract

A kind of apparent defect inspection method of chip, SOP chip image is shot using colorful CCD camera, the profile and centroid of chip circular mark and pin are extracted through a series of pretreatment, calculate the improvement environmental characteristic vector of circular mark and each centroid of pin, then matching positioning is carried out with template image, calculate affine transformation matrix, by image affine transformation template image coordinate system, finally whether the improvement environment vector determination pin of its circular mark is lacked, to its printing zone extract printed pixels and edge judge printing information whether defect, minimum circumscribed rectangle is calculated to its each pin profile and judges whether pin upwarps, it has a downwarp and crooked, oxidation is extracted to its pin field and desoldering pixel judges whether pin aoxidizes and desoldering.This method can automatic, quickly, easily and accurately judge SOP chip pin lack, upwarp, having a downwarp, crooked, desoldering and problem of oxidation, can also judge print information area whether complete display, can effectively detect SOP chip product appearance, reduce staff labor intensity.

Description

A kind of apparent defect inspection method of chip
Technical field
The present invention is a kind of apparent defect inspection method of chip, belongs to Machine Vision Detection field, is a kind of based on improvement The apparent defect inspection method of integrated antenna package (SOP) chip of environment vector quick location technique.
Background technique
In chip device production process, the apparent mass detection of chip is the essential link of one of them, at present The SOP chip apparent mass detection of integrated circuit mainly surveys method using Manual Visual Inspection, and great work intensity be easy to cause erroneous detection, and And detection speed and precision is lower, so that detection efficiency is low, is unable to satisfy the requirement of scope of the enterprise production, above-mentioned factor is larger The development of China's integrated chip production industry is constrained in degree.
Currently, some intrinsic defects also limit the accuracy of SOP chip detection, such as detection speed to a certain extent Degree and precision.
Summary of the invention
To solve the above-mentioned problems, the present invention provide one kind can it is automatic, quickly, easily and accurately judge SOP chip Pin lacks, upwarps, having a downwarp, skew, desoldering and problem of oxidation, can also judge to print information area whether complete display, can The effectively detection method of detection SOP chip product visual defects.The technical solution taken is a kind of apparent defects detection side of chip Method includes the following steps:
(1) machine vision product defects detection hardware platform is built, detection chip obtains color image;
(2) image that histogram equalization is obtained by step (1), then median filter process image;
(3) image that gray processing is obtained by step (2) extracts circular mark profile and pin profile in the picture, calculates The centroid of pin and circular mark respective profile;
(4) centroid obtained by step (3), calculate the improvement environmental characteristic of circular mark centroid and pin profile centroid to Amount;
(5) the improvement environment vector of the centroid obtained by step (4) is similar to the improvement environment vector of template image centroid Matching, wherein template image circular mark and pin environment vector are calculated by step (1) to step (4) in advance;
(6) affine transformation matrix is calculated by the matching centroid point obtained by step (5), then affine transformation is by step (2) color image obtained and the pin profile extracted by step (3) are to reference picture coordinate system;
(7) the improvement environmental characteristic vector of the circular mark centroid obtained by step (4), the circular mark with template image Centroid improves environmental characteristic vector and does similar comparison, shows pin if approximate without lacking, pin on the contrary lacks;
(8) gray processing obtains transformed image by step (6), and locating segmentation goes out to print information area, calculates font picture Element and font edge pixel number account for the ratio of entire printing information area number of pixels, judge to print information whether defect;
(9) hsv color model transformation is obtained the color image after affine transformation by step (6), calculates each pin area Domain defect pixel number accounts for the ratio of entire pin field number of pixels, thus judge the pin whether desoldering and oxidation;
(10) length-width ratio and horizontal tilt of the transformed pin profile minimum circumscribed rectangle obtained by step (6) are calculated Angle, can determine whether pin upwarps and have a downwarp by length-width ratio, can determine whether pin is crooked by horizontal tilt angle.
Preferably: the step (4) the following steps are included:
(4-1) calculates improvement environmental characteristic vector of the circular mark centroid under pin centroid set;
(4-2) calculate the improvement environmental characteristic of each pin centroid under center mark and other pin centroid set to Amount;
Preferably: the step (5) the following steps are included:
The improvement environment for improving environment vector and template image pin centroid of (5-1) calculating input image pin centroid to Similarity between amount;
The pin centroid of the input picture of most like improvement environment vector and reference picture are mutually matched by (5-2) It is right, while directly matching reference picture circular mark centroid and input picture circular mark centroid;
Preferably: the improved environmental characteristic vector used calculate the following steps are included:
Wherein on two-dimensional surface point c in point set P={ p1, p2...pNImproved environmental characteristic vector Context calculating Steps are as follows:
Step 1: the unit vector of calculating point c to the point set p-shaped heartCalculation formula is as follows:
Step 2: the vector of all the points on point c to point set P is calculatedWith vectorAngle Angle={ angle1, angle2...angleN, angle indicates 0~2 π of range, and calculation formula is as follows:
Step 3: the distance Dist={ dist of all the points on point c to point set P is calculated1, dist2...distN, it calculates Formula is as follows:
Step 4: initialization angular histogram AngleHist [l]=0, l=1 ..., L and distance distribution histogram DistHist [l]=0, l=1 ..., L traverses all angle collection Angle and distance set Dist statistics angular histogram and distance distribution histogram, Wherein L indicates the resolution ratio of statistics, and statistical is as follows:
Step 5: normalization angular histogram AngleHist and distance distribution histogram DistHist obtains angle environmental characteristic Vector AngleVector and apart from environment feature vector DistVector, environmental characteristic vector Context is by angle environmental characteristic Vector AngleVector and apart from environment feature vector DistVector form, normalization formula it is as follows:
More detailed detection method is described as follows:
(1) machine vision product defects detection hardware platform is built, detection chip obtains 3 channel RGB image I1
(2) the image I that histogram equalization is obtained by step (1)1, then the median filter process image obtains I2
(3) gray level image I2Obtain image I3, in image I3Middle extraction circular mark profile MarkContour and pin Profile PinContourk, k=1~K, calculate circular mark and pin respective profile centroid MarkCentroid and PinCentroidk, k=1~K, K are pin number;
Further, step (3) includes step in detailed below:
(3-1) is by 3 channel RGB image I2Be converted to gray level image I3
(3-2) global threshold divides I3Obtain the image I containing chip pin region4, threshold value thresh selection be generally higher than 200, it is as follows that global threshold divides formula:
Wherein, I3(i, j) indicates gray level image I3In the pixel value of coordinate (i, j), I4(i, j) indicates global threshold segmentation Image I4In the pixel value of coordinate (i, j), thresh is the threshold value that experience is chosen;
(3-3) extracts image I using a kind of contour following algorithm4Pin profile, given threshold abandon contour area about PinContour is obtained less than normal pins area 60% and greater than 140% profile of pin areak, k=1~K, and calculate Its centroid PinCentroidk, k=1~K, K are pin number, and centroid calculation formula is as follows:
Wherein (xk, yk) represent k-th of profile PinCentroidkCentroid, MkIndicate that k-th of profile contains total pixel Number, (xkm, ykm) indicate profile on m-th of pixel coordinate;
(3-4) extracts the centroid namely circle of circular mark profile MarkContour and circular mark using hough-circle transform Heart MarkCentroid;
(4) the centroid MarkCentroid and PinCentroid obtained by step (3)k, k=1~K, calculating circular mark Improvement environmental characteristic the vector M arkContext and PinContext of centroid and pin profile centroidk, k=1~K;
Further, step (4) includes step in detailed below:
(4-1) calculates circular mark centroid MarkCentroid in set { PinCentroid1...PinCentroidKUnder Improvement environmental characteristic vector M arkContext;
(4-2) calculates each pin centroid PinCentroidk, k=1~K set MarkCentroid, PinCentroid1...PinCentroidk-1, PinCentroidk+1...PinCentroidKUnder improvement environmental characteristic vector PinContextk, k=1~K;
(5) improvement environment the vector M arkContext and PinContext of the centroid obtained by step (4)k, k=1~K With improvement environment the vector rMarkContext and rPinContext of template image centroidk, k=1~K Similarity matching will most phase Like the pin centroid PinCentroid for improving environment vectork, the pin centroid rPinCentroid of k=1~K and template imagek, K=1~K is mutually matched in pairs, while directly matching input picture circular mark centroid MarkCentroid and template image Circular mark centroid rMarkCentroid, wherein template image circular mark and the centroid of pin and environment vector are in advance by step Suddenly (1) to step (4) step calculates;
Further step (5) includes following several detailed steps:
(5-1) calculates the improvement environment vector of the pin centroid obtained by step (4) {PinContext1...PinContextKWith the improvement environment vector of template image pin centroid {rPinContext1...rPinContextKBetween similarity Sim, similarity formula is as follows:
Wherein Sim (p, q) indicates PinContextpAnd rPinContextqSimilarity, Sim (p, q) closer to 0 indicate Similarity is higher, AngleVectorpAnd DistVectorpIt is environmental characteristic vector PinContextpAngle and distance component, Similarly, AngleVectorqAnd DistVectorqIt is environmental characteristic vector rPinContextqAngle and distance component;
(5-2) is by the pin centroid PinCentroid of the input picture of most like improvement environment vectork, k=1~K and Reference picture rPinCentroidk, k=1~K is mutually matched in pairs, while directly matching reference picture circular mark centroid MarkCentroid and input picture circular mark centroid rMarkCentroid;
(6) affine transformation is calculated by the consistent RANSANC algorithm of the matching centroid point random sampling obtained by step (5) Matrix T, the RGB image I that then affine transformation is obtained by step (2)2With the pin profile extracted by step (3) PinContourk, k=1~K to reference picture coordinate system obtains image I5With pin profile tPinContourk, k=1~K;
(7) the improvement environmental characteristic vector M arkContext of the circular mark centroid obtained by step (4), with Prototype drawing The improvement environmental characteristic vector rMarkContext of picture does similar comparison, show if approximate pin without lacking, otherwise pin Lack, wherein making similarity calculation using formula (4), decision threshold is selected by experience;
(8) gray processing obtains transformed image I by step (6)5, locating segmentation, which goes out, prints information area ROI, calculating word Volumetric pixel and font edge pixel number account for the ratio of entire printing information area ROI number of pixels, judge to print whether information lacks It falls into;
Further, step (8) includes step in detailed below:
(8-1) gray processing obtains transformed image I by step (6)5, locating segmentation go out print information area ROI;
(8-2) maximum variance between clusters binaryzation prints information area ROI, printing type face number of pixels is counted, if a The ratio that number accounts for printing information area ROI total number is lower than the 80% of normal value, then determines to print imperfect;
(8-3) edge detection algorithm (Canny algorithm) extracts printing information area ROI, counts printing type face edge pixel Number determines to print unintelligible if the ratio that number accounts for printing information area ROI total number is lower than the 80% of normal value;
(9) hsv color model transformation is obtained the RGB image I after affine transformation by step (6)5, calculate each pin area Domain defect pixel number accounts for the ratio of entire pin field number of pixels, thus judge the pin whether desoldering and oxidation;
Further, step (9) includes step in detailed below:
The transformation of (9-1) hsv color model obtains transformed RGB image I by step (6)5
(9-2) counts each pin field pixel tone H at 40 °~80 °, and saturation degree S is greater than 0.15 number, if What number accounted for the pin total number 40% or more then determines pin desoldering;
(9-3) counts each pin field pixel tone H at 70 °~130 °, and number of the lightness V less than 0.97, if Number account for the pin total number 40% or more then determine pin aoxidize;
(10) the transformed pin profile tPinContour obtained by step (6) is calculatedk, the minimum external square of k=1~K The length-width ratio AspectRatio of shapek, k=1~K and horizontal tilt angle HorizontalAnglek, k=1~K, by length-width ratio AspectRatiok, k=1~K can determine whether pin upwarps and have a downwarp, by horizontal tilt angle HorizontalAnglek, k =1~K can determine whether pin is crooked.
Further, step (10) includes step in detailed below:
(10-1) calculates the transformed pin profile tPinContour obtained by step (6)k, k=1~K's is minimum outer Connect rectangle;
The length-width ratio AspectRatio of (10-2) calculating minimum circumscribed rectanglek, k=1~K, if length-width ratio is greater than or small In the 20% of normal value, then show that the pin upwarps or has a downwarp;
The horizontal tilt angle HorizontalAngle of (10-3) calculating minimum circumscribed rectanglek, k=1~K, if angle More than or less than horizontal 20 °, then show pin skew;
Wherein on two-dimensional surface point c in point set P={ p1, p2...pNImproved environmental characteristic vector Context calculating Steps are as follows:
Step 1: the unit vector of calculating point c to the point set p-shaped heartCalculation formula is as follows:
Step 2: the vector of all the points on point c to point set P is calculatedWith vectorAngle Angle={ angle1, angle2...angleN, angle indicates 0~2 π of range, and calculation formula is as follows:
WhereinIndicate vectorWith the angle of coordinate system,Indicate vectorWith polar angle, anglen Indicate vectorWith vectorAngle;
Step 3: the Euclidean distance Dist={ dist of all the points on point c to point set P is calculated1, dist2...distN, Calculation formula is as follows:
Step 4: initialization angular histogram AngleHist [l]=0, l=1 ..., L and distance distribution histogram DistHist [l]=0, l=1 ..., L traverses all angle collection Angle and distance set Dist statistics angular histogram and distance distribution histogram, Wherein L indicates the resolution ratio of statistics, and statistical is as follows:
Step 5: normalization angular histogram AngleHist and distance distribution histogram DistHist obtains angle environmental characteristic Vector AngleVector and apart from environment feature vector DistVector, environmental characteristic vector Context is by angle environmental characteristic Vector AngleVector and apart from environment feature vector DistVector form, normalization formula it is as follows:
Detailed description of the invention
Fig. 1 is that the present invention is based on the streams for the apparent defect inspection method of SOP chip for improving environment vector quick location technique Cheng Tu;
Fig. 2 is SOP chip defect detection system hardware structural diagram of the present invention;
Fig. 3 is the improvement environment vector of 8 pin SOP chip template image circular marks;
Fig. 4 to Figure 11 is the improvement environment vector of the 8 each pins of pin SOP chip template image;
Figure 12 is that 8 pin SOP chip input picture circular marks improve environment vector;
Figure 13 to Figure 20 is the improvement environment vector of the 8 each pins of pin SOP chip input picture;
Figure 21 is the centroid matching result of 8 pin SOP chip template images and input picture;
Specific embodiment
Present invention will be further explained below with reference to the attached drawings and examples, and embodiments of the present invention include but is not limited to The following example.
Fig. 2 is SOP chip defect detection system hardware structural diagram of the present invention.To pacify above objective chip before detection Industry color CCD camera and light source are filled, computer controls camera shooting and conveyer belt is mobile, when chip is moved to immediately below camera When clap coring piece.Empty soma around chip is required to disturb when detection, conveyer belt background is black, while illumination is abundant, circle mark Note irradiation is clear, and pin brightness is relatively high, and camera resolution is clear enough.
Fig. 3 indicates that the improvement environment vector of the circular mark of 8 pin SOP chip template images, Fig. 4 to Figure 11 indicate template 8 pin centroids of image improve environmental characteristic vector.Equally, Figure 12 indicates that the circular mark of input picture improves environment vector, Figure 13 to Figure 20 indicates that 8 pin centroids of input picture improve environmental characteristic vector.It is all completed above by step (4), each Curve graph represents the improvement environmental characteristic vector of corresponding circular mark and pin centroid, improves the statistics of environmental characteristic vector here Resolution ratio L is 9, and solid line distance indicates that distance feature vector DistVector, dotted line angle indicate angle character vector AngleHist.It can intuitively show that the improvement environmental characteristic vector of template image and input picture corresponding pin is substantially similar , show invariance of the feature with scale, rotation, translation that the algorithm extracts, while there are also certain stability.
Figure 21 is the centroid matching result of 8 pin SOP chip template images and input picture.Template image and input picture All step (5) are arrived by step (1).In step (3), program needs to sieve the pin profile that contour following algorithm extracts Choosing, screening technique lean on contour area, and area approximation pin area retains, and others are rejected;Hough circle extracts circular mark simultaneously It is influenced vulnerable to parameter, needs to be screened according to circular radius size, also to position local area search circular mark, reduce meter in this way Calculation amount reduces noise simultaneously, increases the stability of detection.In step (4), the improvement environmental characteristic of corresponding pin is to measurer There is very high similitude (similitude by formula (4) calculate), it can be seen that template image and input picture correspond to centroid one by one Match.
As shown in Fig. 1 to Figure 21, the SOP chip based on 8 pin of detection for improving environment vector quick location technique is specific Example comprises the following specific steps that:
(1) hardware detection system such as Fig. 2 is built, when transmission comes with chip transportation, computer is sent out to video camera Shooting instruction is sent, the enough clearly input picture I of chip RGB triple channel is obtained1
(2) the image I that histogram equalization is obtained by step (1)1, then the median filter process image obtains I2
(3) gray level image I2Obtain image I3, since the chip of detection is 8 pin chips, therefore chip pin number K is 8, in image I3Middle extraction circular mark profile MarkContour and pin profile PinContourk, k=1~8 calculate round The centroid MarkCentroid and PinCentroid of label and pin respective profilek, k=1~8;
Further, step (3) includes step in detailed below:
(3-1) is by 3 channel RGB image I2Be converted to gray level image I3
(3-2) divides I with formula (1) global threshold3Obtain the image I containing chip pin region4, threshold value thresh choosing It is taken as 220;
Wherein, I3(i, j) indicates gray level image I3In the pixel value of coordinate (i, j), I4(i, j) indicates global threshold segmentation Image I4In the pixel value of coordinate (i, j), thresh is the threshold value that experience is chosen;
(3-3) extracts image I using contour tracing method4Pin profile, abandon pin contour area be less than normally draws Instep accumulates 60% and obtains pin profile PinContour greater than 140% profile of pin contour areak, k=1~8, and by Formula (2) and formula (3) calculate its centroid PinCentroidk, k=1~8;
Wherein (xk, yk) represent k-th of profile PinCentroidkCentroid, MkIndicate that k-th of profile contains total pixel Number, (xkm, ykm) indicate profile on m-th of pixel coordinate;
(3-4) extracts the centroid namely circle of circular mark profile MarkContour and circular mark using hough-circle transform Heart MarkCentroid;
(4) the centroid MarkCentroid and PinCentroid obtained by step (3)k, k=1~8 calculate circular mark Improvement environmental characteristic the vector M arkContext and PinContext of centroid and pin profile centroidk, k=1~8,8 pin SOP Improvement environmental characteristic vector calculated result such as Fig. 3 to Figure 11 and Figure 12 to Figure 20 institute of chip detection example template and input picture Show;
Further, step (4) includes step in detailed below:
(4-1) calculates circular mark centroid MarkCentroid in set { PinCentroid1...PinCentroid8Under Improvement environmental characteristic vector M arkContext;
(4-2) calculates each pin centroid PinCentroidk, k=1~8 set MarkCentroid, PinCentroid1...PinCentroidk-1, PinCentroidk+1...PinCentroid8Improvement environmental characteristic vector PinContextk, k=1~8;
(5) improvement environment the vector M arkContext and PinContext of the centroid obtained by step (4)k, k=1~8 With improvement environment the vector rMarkContext and rPinContext of template image centroidk, the Similarity matching of k=1~8 will most phase Like the pin centroid PinCentroid for improving environment vectork, the pin centroid rPinCentroid of k=1~8 and template imagek, K=1~8 are mutually matched in pairs, while matching the circle of input picture circular mark centroid MarkCentroid and template image Centroid rMarkCentroid is marked, 8 pin SOP chip detection example matching results are as shown in figure 21;
Further step (5) includes following several detailed steps:
(5-1) calculates the improvement environment vector of the pin centroid obtained by step (4) with formula (4) {PinContext1...PinContext8With the improvement environment vector of template image pin centroid {rPinContext1...rPinContext8Between similarity Sim;
Wherein Sim (p, q) indicates PinContextpAnd rPinContextqSimilarity, Sim (p, q) closer to 0 indicate Similarity is higher, AngleVectorpAnd DistVectorpIt is environmental characteristic vector PinContextpAngle and distance component, Similarly, AngleVectorqAnd DistVectorqIt is environmental characteristic vector rPinContextqAngle and distance component;
(5-2) is by the pin centroid PinCentroid of the input picture of most like improvement environment vectork, the He of k=1~8 Reference picture rPinCentroidk, k=1~8 are mutually matched in pairs, while directly matching reference picture circular mark centroid RMarkCentroid and input picture circular mark centroid MarkCentroid;
(6) affine transformation is calculated by the consistent RANSANC method of the matching centroid point random sampling obtained by step (5) Matrix T, the RGB image I that then affine transformation is obtained by step (2)2With the pin profile extracted by step (3) PinContourk, k=1~8 arrive reference picture coordinate system, obtain I5And tPinContourk, k=1~8;
(7) the improvement environmental characteristic vector M arkContext of the circular mark centroid obtained by step (4), with Prototype drawing The improvement environmental characteristic vector rMarkContext of picture does similar comparison, show if approximate pin without lacking, otherwise pin Lack, wherein using formula (4) calculating formula of similarity, decision threshold is selected by experience;
(8) gray processing obtains transformed image I by (6)5, locating segmentation, which goes out, prints information area ROI, calculating font picture Element and font edge pixel number account for the ratio of entire printing information area ROI number of pixels, judge to print information whether defect;
Further, step (8) includes step in detailed below:
(8-1) gray processing obtains transformed image I by (6)5, locating segmentation go out print information area ROI;
(8-2) maximum variance between clusters binaryzation prints information area ROI, printing type face number of pixels is counted, if a The ratio that number accounts for printing information area ROI total number is lower than the 80% of normal value, then determines to print imperfect;
(8-3) edge detection method (Canny method) extracts printing information area ROI, counts printing type face edge pixel Number determines to print unintelligible if the ratio that number accounts for printing information area ROI total number is lower than the 80% of normal value;
(9) hsv color model transformation is obtained the RGB image I after affine transformation by (6)5, calculate each pin field and lack Sunken number of pixels accounts for the ratio of entire pin field number of pixels, thus judge the pin whether desoldering and oxidation;
Further, step (9) includes step in detailed below:
The transformation of (9-1) hsv color model obtains transformed RGB image I by (6)5
(9-2) counts each pin field pixel tone H at 40 °~80 °, and saturation degree S is greater than 0.15 number, if What number accounted for the pin total number 40% or more then determines pin desoldering;
(9-3) counts each pin field pixel tone H at 70 °~130 °, and number of the lightness V less than 0.97, if Number account for the pin total number 40% or more then determine pin aoxidize;
(10) the transformed pin profile tPinContour obtained by (6) is calculatedk, the minimum circumscribed rectangle of k=1~8 Length-width ratio AspectRatiok, k=1~8 and horizontal tilt angle HorizontalAnglek, k=1~8, by length-width ratio AspectRatiok, k=1~8 can determine whether pin upwarps and have a downwarp, by horizontal tilt angle HorizontalAnglek, k =1~8 can determine whether pin is crooked.
Further, step (10) includes step in detailed below:
(10-1) calculates the transformed pin profile tPinContour obtained by (6)k, the external square of minimum of k=1~8 Shape;
The length-width ratio AspectRatio of (10-2) calculating minimum circumscribed rectanglek, k=1~8, if length-width ratio is greater than or small In the 20% of normal value, then show that the pin upwarps or has a downwarp;
The horizontal tilt angle HorizontalAngle of (10-3) calculating minimum circumscribed rectanglek, k=1~8, if angle More than or less than horizontal 20 °, then show pin skew;
Wherein on two-dimensional surface point c in point set P={ p1, p2...pNImproved environmental characteristic vector Context calculating Steps are as follows:
Step 1: the unit vector of calculating point c to the point set p-shaped heartCalculation formula is as follows:
Step 2: the vector of all the points on point c to point set P is calculatedWith vectorAngle Angle={ angle1, angle2...angleN, angle indicates 0~2 π of range, and calculation formula is as follows:
WhereinIndicate vectorWith the angle of coordinate system,Indicate vectorWith polar angle, anglen Indicate vectorWith vectorAngle;
Step 3: the Euclidean distance Dist={ dist of all the points on point c to point set P is calculated1, dist2...distN, Calculation formula is as follows:
Step 4: initialization angular histogram AngleHist [l]=0, l=1 ..., L and distance distribution histogram DistHist [l]=0, l=1 ..., L traverses all angle collection Angle and distance set Dist statistics angular histogram and distance distribution histogram, Wherein L indicates the resolution ratio of statistics, and statistical is as follows:
Step 5: normalization angular histogram AngleHist and distance distribution histogram DistHist obtains angle environmental characteristic Vector AngleVector and apart from environment feature vector DistVector, environmental characteristic vector Context is by angle environmental characteristic Vector AngleVector and apart from environment feature vector DistVector form, normalization formula it is as follows:
According to above-described embodiment, the present invention can be realized well.It is worth noting that before based on said structure design It puts, to solve same technical problem, even if that makes in the present invention is some without substantive change or polishing, is used Technical solution essence still as the present invention, therefore it should also be as within the scope of the present invention.

Claims (4)

1. a kind of apparent defect inspection method of chip, characterized by the following steps:
(1) machine vision product defects detection hardware platform is built, detection chip obtains color image;
(2) image that histogram equalization is obtained by step (1), then median filter process image;
(3) image that gray processing is obtained by step (2) extracts circular mark profile and pin profile in the picture, calculates pin With the centroid of circular mark respective profile;
(4) centroid obtained by step (3) calculates the improvement environmental characteristic vector of circular mark centroid and pin profile centroid;
(5) the improvement environment vector Similarity matching of improvement the environment vector and template image centroid of the centroid obtained by step (4), Wherein template image circular mark and pin environment vector are calculated by step (1) to step (4) in advance;
(6) affine transformation matrix is calculated by the matching centroid point obtained by step (5), then affine transformation is obtained by step (2) The color image that takes and the pin profile extracted by step (3) are to reference picture coordinate system;
(7) the improvement environmental characteristic vector of the circular mark centroid obtained by step (4), the circular mark centroid with template image It improves environmental characteristic vector and does similar comparison, show pin if approximate without lacking, pin on the contrary lacks;
(8) gray processing obtains transformed image by step (6), and locating segmentation goes out to print information area, calculate font pixel and Font edge pixel number accounts for the ratio of entire printing information area number of pixels, judge to print information whether defect;
(9) hsv color model transformation is obtained the color image after affine transformation by step (6), is calculated each pin field and is lacked Sunken number of pixels accounts for the ratio of entire pin field number of pixels, thus judge the pin whether desoldering and oxidation;
(10) length-width ratio and the horizontal tilt angle of the transformed pin profile minimum circumscribed rectangle obtained by step (6) are calculated Degree, can determine whether pin upwarps and have a downwarp by length-width ratio, can determine whether pin is crooked by horizontal tilt angle.
2. the apparent defect inspection method of a kind of chip according to claim 1, it is characterised in that: the step (4) includes Following steps:
(4-1) calculates improvement environmental characteristic vector of the circular mark centroid under pin centroid set;
(4-2) calculates improvement environmental characteristic vector of each pin centroid under center mark and other pin centroid set.
3. the apparent defect inspection method of a kind of chip according to claim 1, it is characterised in that: the step (5) include with Lower step:
The improvement environment vector for improving environment vector and template image pin centroid of (5-1) calculating input image pin centroid it Between similarity;
The pin centroid of the input picture of most like improvement environment vector and reference picture are mutually matched in pairs, together by (5-2) When direct matching reference picture circular mark centroid and input picture circular mark centroid.
4. the apparent defect inspection method of a kind of chip according to claim 1, it is characterised in that: step (4) and step (7) institute The improved environmental characteristic vector stated calculate the following steps are included:
Wherein on two-dimensional surface point c in point set P={ p1, p2...pNImproved environmental characteristic vector Context calculating step It is as follows:
Step S001: the unit vector of calculating point c to the point set p-shaped heartCalculation formula is as follows:
Step S002: the vector of all the points on point c to point set P is calculatedWith vectorIncluded angle A ngle ={ angle1, angle2...angleN, angle indicates 0~2 π of range, and calculation formula is as follows:
WhereinIndicate vectorWith the angle of coordinate system,Indicate vectorWith polar angle, anglenIt indicates VectorWith vectorAngle;
Step S003: the Euclidean distance Dist={ dist of all the points on point c to point set P is calculated1, dist2...distN, meter It is as follows to calculate formula:
Step S004: initialization angular histogram AngleHist [l]=0, l=1 ..., L and distance distribution histogram DistHist [l]=0, l=1 ..., L traverses all angle collection Angle and distance set Dist statistics angular histogram and distance distribution histogram, Wherein L indicates the resolution ratio of statistics, and statistical is as follows:
Step S005: normalization angular histogram AngleHist and distance distribution histogram DistHist obtain angle environmental characteristic to Measure AngleVector and apart from environment feature vector DistVector, environmental characteristic vector Context from angle environmental characteristic to It measures AngleVector and is formed apart from environment feature vector DistVector, normalization formula is as follows:
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