基于機器視覺的PCB 光板缺陷檢測技術(shù)研究

1、 （申請工學(xué)碩士學(xué)位論文） 基于機器視覺的PCB 光板缺陷 檢測技術(shù)研究培養(yǎng)單位 ：信息工程學(xué)院 學(xué)科專業(yè) ：通信與信息系統(tǒng) 研 究 生 ：胡文娟指導(dǎo)教師 ：劉 泉 教 授2007年4月基于機器視覺的PCB光板缺陷檢測技術(shù)研究胡文娟武漢理工大學(xué)分類號密 級 UDC 學(xué)校代碼學(xué) 位 論 文題 目 基于機器視覺的PCB 光板缺陷檢測技術(shù)研究 英 文 Research of Machine Vision Based題 目 Defect Detection Techniques on PCB 研究生姓名姓 名職 稱 單位名稱 郵 編申請學(xué)位級別 碩士 學(xué)科專業(yè)名稱 通信與信息系統(tǒng) 論文提交日期 200

2、7年4月 論文答辯日期 2007年5月 學(xué)位授予單位 武漢理工大學(xué) 學(xué)位授予日期 答辯委員會主席 陳 偉 評閱人 周 祖 德2007年4月指導(dǎo)教師摘 要印刷電路板(PCB是集成各種電子元器件的信息載體，在電子領(lǐng)域中有著廣泛的應(yīng)用。隨著技術(shù)的不斷發(fā)展和工藝水平的不斷提高，電子產(chǎn)品趨于更輕、更薄、更小，PCB 朝著層數(shù)更多、密度更高的方向發(fā)展，這使得PCB 的質(zhì)量檢驗成為一件非常困難的工作。傳統(tǒng)的人工檢測方法容易漏檢、檢測速度慢、檢測時間長，已經(jīng)不能滿足生產(chǎn)的需要，如何更有效的實現(xiàn)PCB 的自動缺陷檢測，成為半導(dǎo)體工業(yè)領(lǐng)域一個熱門問題。機器視覺檢測技術(shù)，集電子學(xué)、光電探測、圖像處理和計算機技術(shù)于一

3、身，是精密測試技術(shù)領(lǐng)域內(nèi)最具有發(fā)展?jié)摿Φ男录夹g(shù)。機器視覺系統(tǒng)，一般采用CCD 或CMOS 攝像機攝取待檢測目標并轉(zhuǎn)化為數(shù)字信號，再采用先進的計算機硬件與軟件技術(shù)對數(shù)字圖像信號進行處理，從而得到所需要的各種目標圖像特征值，并由此實現(xiàn)零件識別或缺陷檢測等多種功能。然后再根據(jù)其結(jié)果顯示圖像，輸出數(shù)據(jù)，由反饋信息引導(dǎo)執(zhí)行機構(gòu)完成位置調(diào)整、好壞篩選等自動化流程。將機器視覺引入到工業(yè)檢測中，具有非接觸、速度快、柔性好等突出優(yōu)點，在現(xiàn)代制造業(yè)中有著重要的應(yīng)用前景。本文將機器視覺技術(shù)應(yīng)用到PCB 光板的缺陷檢測中，實現(xiàn)PCB 光板的自動缺陷檢測。在研究機器視覺技術(shù)的基礎(chǔ)上，針對PCB 光板上的幾種常見幾何缺陷

4、類型，制定PCB 光板缺陷檢測系統(tǒng)總體方案，討論視覺檢測系統(tǒng)工作原理，為PCB 光板視覺檢測系統(tǒng)搭建硬件平臺：包括照明系統(tǒng)、圖像采集系統(tǒng)、以及控制臺系統(tǒng)；重點針對采集的PCB 光板圖像討論視覺檢測算法并進行仿真實驗，包括圖像預(yù)處理、分割、描述、數(shù)學(xué)形態(tài)學(xué)、模式識別等方法，著重根據(jù)PCB 設(shè)計規(guī)則運用數(shù)學(xué)形態(tài)學(xué)及模式識別方法完成自動檢測識別；最后根據(jù)視覺檢測算法設(shè)計系統(tǒng)軟件，對PCB 光板完成缺陷的檢測與識別。對包含不同缺陷的PCB 光板圖像進行實驗，結(jié)果證明本文的PCB 光板缺陷檢測系統(tǒng)能夠?qū)CB 光板上的短路、斷路、毛刺、缺損四種主要缺陷做出有效的檢測、定位與識別。關(guān)鍵字：印刷電路板(PC

5、B；機器視覺；數(shù)學(xué)形態(tài)學(xué)；模式識別AbstractPrinted Circuit Board, a kind of information carrier which integrates varieties of electronic devices, has popular applications in electronic fields nowadays. With the rapid development of manufacture techniques, electronic product tends to lighter, thinner and smaller, and

6、PCB turns to have more layers and higher density, which makes quality detection of PCB become more difficult. Traditional detection methods can not satisfy the large production for inaccurate, slow and long time detection, then how to realize automated defect detection of PCB becomes a hot topic in

7、semiconductor industry.Machine vision technology, which combines electronics, photoelectric detection, image processing and computer technology into oneself, is a potential new technology in industrial detection field. Machine vision system, usually obtains digital image signals of detected object b

8、y CCD or CMOS camera, then processes the digital image signals to get characteristic values by adopting advanced computer hardware and software techniques, and accomplishes workpiece recognition or defect detection accordingly. Based on the results, the system displays the images, exports the data a

9、nd sends out instructions to control corresponding equipment to act such as location adjusting and quality filtering according to feedback information.Machine vision technology is applied into automated PCB defect detection in this paper. On the basis of studying machine vision technology, we design

10、 the whole scheme of PCB defect detection system towards several simple geometric defects on PCB, discuss the principle of the system, and establish hardware platform for the system, including illuminating unit, image acquisition unit and control unit. Then, we discuss and design the foremost vision

11、 detection algorithm towards PCB image, including image pre-processing, segmentation, description, mathematical morphology, and pattern recognition, while the key is to accomplish defect detection using mathematical morphology and pattern recognition based on PCB design rules. Finally, we design sys

12、tem software according to the vision detection algorithm to realize defect detection and recognition on PCB.Experimental results demonstrate that though the PCB defect detection system described in this paper, four types of defects including short circuit, open circuit,protuberance and concavity on

13、PCB can be effectively detected, located and recognized.Keywords: Printed Circuit Board(PCB; Machine Vision; Mathematical Morphology;Pattern Recognition目 錄第1章 緒 論·······················

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21、·······················6第2章 PCB光板視覺檢測系統(tǒng)總體設(shè)計·······················

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138、;··········74第1章 緒 論1.1 機器視覺檢測技術(shù)綜述檢測技術(shù)是制造業(yè)的基礎(chǔ)，隨著制造水平的快速發(fā)展，制造領(lǐng)域不斷擴大，產(chǎn)品質(zhì)量不斷提高。相應(yīng)地，對檢測技術(shù)提出了新的需要，傳統(tǒng)意義上的很多檢測方法已經(jīng)不能適應(yīng)現(xiàn)代制造業(yè)的要求。比如在汽車工業(yè)中，為全面控制車身的制造質(zhì)量，需要在制造現(xiàn)場對制造過程中的產(chǎn)品(或零件 實行檢測，這是一類典型的在線測量問題，在現(xiàn)代制造業(yè)中具有廣泛代表性，也是傳統(tǒng)測量方法難以解決的。對于工業(yè)中批量生產(chǎn)的產(chǎn)品，傳統(tǒng)的人工檢測存在以下幾個不可避免的缺點：(1 容易

139、漏檢。由于是人眼檢測，眼睛容易疲勞，會造成故障不能被發(fā)現(xiàn)的問題。并且人工檢測主觀性大，判斷標準不統(tǒng)一，使檢測質(zhì)量變得不穩(wěn)定。(2 檢測速度慢，檢測時間長。比如對于圖形復(fù)雜的印刷電路板，人工很難實現(xiàn)快速高效的檢測，因此人工檢測不能滿足高速的生產(chǎn)效率。(3 隨著技術(shù)的發(fā)展，設(shè)備的成本降低，人工費用增加，仍然由人工進行產(chǎn)品質(zhì)量控制，將難于實現(xiàn)優(yōu)質(zhì)高效，而且還會增加生產(chǎn)成本。(4 在信息技術(shù)如此發(fā)達的今天人工檢測有不可克服的劣勢，例如：對檢測結(jié)果實時地保存和遠距離傳輸，對原始圖像的保存和遠距離傳輸?shù)取?5 有些在線檢測系統(tǒng)是接觸式檢測，需要與產(chǎn)品進行接觸測量，因此，有可能會損傷產(chǎn)品。機器視覺(Mach

140、ine Vision檢測技術(shù)，綜合運用了電子學(xué)、光電探測、圖像處理和計算機技術(shù)，是精密測試技術(shù)領(lǐng)域內(nèi)最具有發(fā)展?jié)摿Φ男录夹g(shù)。將機器視覺引入到工業(yè)檢測中，實現(xiàn)對物體(產(chǎn)品或零件 三維尺寸或位置的快速測量，具有非接觸、速度快、柔性好等突出優(yōu)點，在現(xiàn)代制造業(yè)中有著重要的應(yīng)用前景。機器視覺工業(yè)檢測系統(tǒng)就其檢測性質(zhì)和應(yīng)用范圍而言，分為定量檢測和定性檢測兩大類，每類又分為不同的子類。機器視覺在工業(yè)在線檢測的各個應(yīng)用領(lǐng)域十分活躍，如：印刷電路板的視覺檢測、鋼板表面的自動探傷、大型工件平行度和垂直度測量、容器容積或雜質(zhì)檢測、機械零件的自動識別分類和幾何尺寸測量等。此外，在許多其它方法難以檢測的場合，利用機器視

141、覺系統(tǒng)可以有效地實現(xiàn)。機器視覺的應(yīng)用正越來越多地代替人去完成許多工作，這無疑在很大程度上提高了生產(chǎn)自動化水平和檢測系統(tǒng)的智能水平1,2。具體來講，機器視覺系統(tǒng)是指通過機器視覺產(chǎn)品，即圖像攝取裝置，將被攝取目標轉(zhuǎn)換成圖像信號，傳送給專用的圖像處理系統(tǒng)，根據(jù)像素分布和亮度、顏色等信息，轉(zhuǎn)變成數(shù)字化信號；圖像系統(tǒng)對這些信號進行各種運算來抽取目標的特征，進而根據(jù)判別的結(jié)果來控制現(xiàn)場的設(shè)備動作。機器視覺系統(tǒng)基本構(gòu)成框圖如圖1-1所示。 圖1-1 機器視覺系統(tǒng)基本構(gòu)成框圖由于機器視覺系統(tǒng)可以快速獲取大量信息，而且易于自動處理，也易于同設(shè)計信息以及加工控制信息集成，因此，在現(xiàn)代自動化生產(chǎn)過程中，人們將機器視

142、覺系統(tǒng)廣泛地用于工況監(jiān)視、成品檢驗和質(zhì)量控制等領(lǐng)域。機器視覺系統(tǒng)的特點是提高生產(chǎn)的柔性和自動化程度。在一些不適合于人工作業(yè)的危險工作環(huán)境或人工視覺難以滿足要求的場合，常用機器視覺來替代人工視覺；同時在大批量工業(yè)生產(chǎn)過程中，用人工視覺檢查產(chǎn)品質(zhì)量效率低且精度不高，用機器視覺檢測方法可以大大提高生產(chǎn)效率和生產(chǎn)的自動化程度。而且機器視覺易于實現(xiàn)信息集成，是實現(xiàn)計算機集成制造的基礎(chǔ)技術(shù)。DVT 總裁Robert Steinke認為，“任何通過人來完成的檢測過程，都適合于用機器視覺技術(shù)來代替”?？傊?，隨著機器視覺技術(shù)自身的成熟和發(fā)展，可以預(yù)計它將在現(xiàn)代和未來制造企業(yè)中得到越來越廣泛的應(yīng)用。在國外，機器視

143、覺的應(yīng)用普及主要體現(xiàn)在半導(dǎo)體及電子行業(yè)，其中大概40%-50%都集中在半導(dǎo)體行業(yè)。具體如PCB 印刷電路：各類生產(chǎn)印刷電路板組裝技術(shù)、設(shè)備；單、雙面、多層線路板，覆銅板及所需的材料及輔料；輔助設(shè)施以及耗材、油墨、藥水藥劑、配件；電子封裝技術(shù)與設(shè)備；絲網(wǎng)印刷設(shè)備及絲網(wǎng)周邊材料等。SMT 表面貼裝：SMT 工藝與設(shè)備、焊接設(shè)備、測試儀器、返修設(shè)備及各種輔助工具及配件、SMT 材料、貼片劑、膠粘劑、焊劑、焊料及防氧化油、焊膏、清洗劑等；再流焊機、波峰焊機及自動化生產(chǎn)線設(shè)備。電子生產(chǎn)加工設(shè)備：電子元件制造設(shè)備、半導(dǎo)體及集成電路制造設(shè)備、元器件成型設(shè)備、電子工模具。機器視覺系統(tǒng)還在質(zhì)量檢測的各個方面已經(jīng)

144、得到了廣泛的應(yīng)用，并且其產(chǎn)品在應(yīng)用中占據(jù)著舉足輕重的地位3-6。而在中國，以上行業(yè)本身就屬于新興的領(lǐng)域，再加之機器視覺產(chǎn)品技術(shù)的普及不夠，導(dǎo)致以上各行業(yè)的應(yīng)用幾乎空白，即便是有，也只是低端方面的應(yīng)用。目前在我國，隨著配套基礎(chǔ)建設(shè)的完善，技術(shù)、資金的積累，各行各業(yè)對采用圖像和機器視覺技術(shù)的工業(yè)自動化、智能化需求開始廣泛出現(xiàn)。國內(nèi)有關(guān)大專院校、研究所和企業(yè)近兩年在圖像和機器視覺技術(shù)領(lǐng)域進行了積極思索和大膽的嘗試，逐步開始了工業(yè)現(xiàn)場的應(yīng)用。其主要應(yīng)用于制藥、印刷、礦泉水瓶蓋檢測等領(lǐng)域。這些應(yīng)用大多集中在如藥品檢測分裝、印刷色彩檢測等，真正高端的應(yīng)用還很少，因此，以上相關(guān)行業(yè)的應(yīng)用空間還比較大。當然，

145、其他領(lǐng)域如指紋檢測等等領(lǐng)域也有著很好的發(fā)展空間。1.2 PCB光板視覺檢測技術(shù)發(fā)展狀況及分析隨著信息技術(shù)的發(fā)展，微電子產(chǎn)業(yè)已經(jīng)成為信息產(chǎn)業(yè)的核心，而集成電路又是信息技術(shù)產(chǎn)業(yè)群的基礎(chǔ)，因此發(fā)展集成電路產(chǎn)業(yè)是我國信息產(chǎn)業(yè)發(fā)展的重中之重。微電子產(chǎn)業(yè)是一個高新技術(shù)行業(yè)，同時也是一個巨大的行業(yè)，它包含了科研開發(fā)、生產(chǎn)加工、質(zhì)量檢測等諸多方面，而微電子產(chǎn)品的檢測技術(shù)是產(chǎn)品研發(fā)及生產(chǎn)加工質(zhì)量保證的關(guān)鍵技術(shù)。印刷電路板(PCB是集成各種電子元器件的信息載體，在各個領(lǐng)域得到了廣泛的應(yīng)用。隨著技術(shù)的不斷發(fā)展和工業(yè)的持續(xù)進步，電子產(chǎn)品趨于更輕、更薄、更短、更小，也使得PCB 制造技術(shù)朝更高密度發(fā)展。由于這些原因，生

146、產(chǎn)及更換它們的成本也越來越高。所以，需要相應(yīng)的質(zhì)量控制手段，使每一層上的線路都能夠在上一層鋪設(shè)之前被檢查，排除或修復(fù)大部分缺陷。在PCB 光板的大批量生產(chǎn)過程中，出現(xiàn)的故障基本都是線路錯誤，主要可分為：短路、斷路、毛刺、缺損四類。如果不及時地將這些質(zhì)量問題檢查出來，勢必在PCB 板調(diào)試和使用過程中留下隱患，造成更大的損失7,8。自動光學(xué)檢測(AOI, Automated Optical Inspection是近幾年興起一種視覺檢測方法。它是通過CCD 照相的方式獲得器件的圖像，然后經(jīng)過計算機的處理和分析比較來判斷缺陷和故障。其優(yōu)點是檢測速度快，編程時間較短，可以放到生產(chǎn)線中的不同位置，便于及時

147、發(fā)現(xiàn)故障和缺陷，使生產(chǎn)、檢測合二為一，可縮短發(fā)現(xiàn)故障和缺陷時間，及時找出故障和缺陷的成因。因此它是目前采用得比較多的一種檢測手段。在國外，經(jīng)過10多年的努力，自動光學(xué)檢測系統(tǒng)(AOI最終被成功地運用在印刷電路板生產(chǎn)線上。在這段時間內(nèi)，AOI 供應(yīng)商的數(shù)量急劇增加，各種AOI 技術(shù)也得到了長足發(fā)展。目前，從簡單的攝像系統(tǒng)到復(fù)雜的3-D X光檢測系統(tǒng)，眾多供應(yīng)商們已經(jīng)幾乎能夠提供可以適用于所有自動生產(chǎn)線的AOI 設(shè)備9。目前具備AOI 系統(tǒng)的供應(yīng)商有英國Diagnosys 公司的Vision Point型，由中國三吉電氣(集團 有限公司代理；美國Tera Dyne公司的5500型，由香港DEI 公

148、司代理；美國Angilent 公司的SDX(有X 射線 ，由安捷倫公司代理。此外還有其它PCB 自動檢測儀，如Sony Minokamo Corporation(索尼美濃加茂株式會社 的CPC-1000系列產(chǎn)品，Orbotech 公司生產(chǎn)的Trion-2000系列。對于Trion-2000系列，由于采用了多攝像頭技術(shù)，因此對于很多平常難以檢測到的缺陷都可以發(fā)現(xiàn)，功能十分強大，但價格十分昂貴，而國內(nèi)還沒有這樣強大功能的自主產(chǎn)品。隨著科學(xué)技術(shù)的飛速發(fā)展和工業(yè)自動化程度的提高，高速、高精度、非接觸的在線檢測已成為檢測行業(yè)的發(fā)展方向，它可以大大地解放勞動力，達到提高生產(chǎn)效率和產(chǎn)品質(zhì)量、降低成本的目的。

149、科技的發(fā)展的和使用要求的提高，對應(yīng)用于辦公自動化和產(chǎn)品質(zhì)量檢測的圖像輸入、檢測和識別系統(tǒng)提出了大幅面、高速、高分辨率和高精度的要求。在辦公自動化系統(tǒng)中，要求對大幅面圖紙等進行高速、高精度的掃描輸入，以提高辦公自動化的效率和質(zhì)量；在產(chǎn)品質(zhì)量檢測中，要求對寬幅打印機打印質(zhì)量(高分辨率 、彩色印刷套色質(zhì)量(印刷品的表現(xiàn)力 、PCB 制造質(zhì)量和液晶點陣顯示器質(zhì)量檢測(加工制造密度己經(jīng)達到近10微米的數(shù)量級 、硬盤磁頭等進行高精度檢測和跟蹤控制。假如以前依靠人眼進行質(zhì)量檢測，現(xiàn)在若仍采用該手段，已無法達到質(zhì)量檢測目的10-12。機器視覺技術(shù)與圖像掃描技術(shù)密不可分，掃描技術(shù)已廣泛應(yīng)用于將光學(xué)信號轉(zhuǎn)變?yōu)殡娦盘柕脑O(shè)備中。光學(xué)技術(shù)的發(fā)展，使得人類可以借助于攝像機、照相機、顯微鏡等獲取的圖像信息記錄、觀察和描述客觀世界。CCD 技術(shù)是一種基于數(shù)字光學(xué)的掃描技術(shù)，其品質(zhì)的高低在很大程度上就決定了掃描圖像的質(zhì)量。CCD 器件的出現(xiàn)使掃描技術(shù)由原來的機械掃描轉(zhuǎn)向電子掃描，是掃描技術(shù)的一大發(fā)展。利用CCD 器件掃描不僅可以大大提高掃描速度，而且使掃描更穩(wěn)定可靠、易于控制且自動化操作。利用數(shù)字掃描機或數(shù)字照相機對景物圖像、圖形、文件等進行掃描拍攝，將光影像聚焦到掃描機內(nèi)光電荷藕合器件CCD 傳感器上進行光電轉(zhuǎn)換成數(shù)字電信號，再把電信號轉(zhuǎn)輸?shù)桨雽?dǎo)體存