SMD PCB 錫瑕疵與電阻缺錯件自動視覺檢測系統

Abstract

於印刷電路板組裝業中，所應用之表面黏著技術（SMT）日益成熟，著裝機之準確度亦不斷提昇，但仍有許多瑕疵存在於製程之中，其中主要包括元件之缺件、錯件、歪斜、極性反、錫膏造成短路、錫焊點錫量過多與錫焊點錫量過少等瑕疵現象。 本研究針對（1）電阻之缺件與錯件、（2）具IC腳之排阻、小型外引腳積體電路（SOP）及方形扁平封裝積體電路（QFP）之錫腳橋接與（3）方形扁平封裝積體電路之錫焊點錫量過多或太少等瑕疵現象，並考慮到實務上的問題，進行檢測演算法之開發。 鑑於不同照明方式會密切影響檢測結果，本研究採用多層式環狀發光二極體陣列（LED Array），可根據不同取像需求，程式控制自動切換照明方式，以取得適當之影像，因此本研究利用所開發之演算法，搭配不同照明以決定最適光源與PCB自動檢測演算法之組合，並以實作系統來驗證所開發PCB自動檢測系統之適用性及有效性。

SMT machine in PCB assembly is moving up rapidly during the past decades. While many defects, such as component missing, wrong component, misalignment, wrong polarity, solder bridge, excess solder, insufficient solder etc., still hide in the working process. This paper is to design and develop an SMD-based PCB auto-inspection system by using the machine vision technology. The in-line PCB production problem is considered. The mainly focused inspection items of SMD components are resister missing / wrong component, solder bridge of the lead of SOP or QFP, and excess solder / insufficient solder of solder joints of QFP. A new programmable-controlled lighting environment composed of multi-layer of ring-type LED array is also designed, which can provide appropriate light for grabbing the desired PCB image. A prototype of the PCB auto-inspection machine is implemented which shows high robustness and effectiveness of the proposed machine vision method.