Online Vision Detection System For Quality Of LED Patch On Printed Circuit Board

Flexible printed circuit is a kind of highly reliability and flexible board,which is more and more widely used.The flexible printed circuit board is mainly used in notebook computer keyboard,the led on the flexible printed circuit board need to be gone through three process silver point,patch,glue sealing.But the human visual defect detection method is used in the test by most business.Compared with the traditional rigid printed circuit board,the flexible printed circuit is different in plate and material,so is the imaging and production process.So the traditional rigid circuit board detection method can not be used directly for flexible printed circuit board.In order to improve the detection speed and reduce the cost of employment,a specialized defect detection system online about silver point,patch,glue sealing is needed.The contents of this paper are mainly focused on the following aspects:(1)Hardware program of silver,patch and seal defect detection of flexible printed circuit board is designed,which is according to the FPC product line,and the imaging system is designed according to the line character and function needed.(2)Image enhancement and morphology are used to locate the silver point roughly.Based on roughly location,template matching is used to locate silver point precisely.The difference of silver point and retention holes and positional relationship are used to detect misalignment.The length and width of contour in background are used to detect silver point brush beyond the specified range flaw.(3)In order to defect patch leak,rarity,stick inclined and offset,template matching based on contour-feature is used to locate the land of patch;Smallest bounding rectangle is adopted to get the range of effective area,and template matching is used to detect patch leak.Average gray value is adopted to detect rarity.The intersection and difference of effective area and LED domain is applied,which detect the stick inclined and offset.(4)Glue sealing defect detection method is studied: Template matching is used to locate the LED.The ratio of black adhesive and the valid area of black adhesive is used to test more glue and less glue.The Average gray value is used to detect lamp cover.The proposed scheme which has already used on-line indicated that the test time is satisfy the requirements and has a high detection accuracy.