In-line optical micro-crack detection system for solar wafers

Abstract

A new approach incorporating adaptive lighting intensity for micro-crack inspection of solar wafers with variable thickness is proposed. Wafer thickness is measured with a pair of laser displacement sensors and the lighting intensity is adaptively adjusted to normalize near infrared (NIR) transmission based on measured thickness. This technique enables the image contrast be maintained at relatively uniform intensity in response to the variation of the solar wafer thickness. An improved version of Niblack segmentation algorithm is developed for this application. Experimental results demonstrate the competitiveness of the proposed system compared with established techniques, and achieves better performance both visually and quantitatively. Meanwhile, the runtime is consistently less than 1 s, corresponding to a throughput rate of approximately 3600 wafers/h. These results suggest that the methods and procedures are suitable for online processing of solar wafers.

A Gabor filter based weak crack detection method for glassivation passivation parts wafer

“…In silicon wafer and solar cell fields, many studies have investigated micro-crack defect detection methods, which can be generally divided into the following categories according to their respective technical principles [3,4]: light beam induced current [5], lock-in thermography [6], resonance ultrasonic vibration [7], scanning acoustic microscopy [8], optical transmission [9], photoluminescence (PL) [10], and electroluminescence (EL) [11]. However, these methods are primarily used to detect micro-crack defects on the surface or internal structure of silicon wafers and solar cells.…”

Recent advancements in micro-crack inspection of crystalline silicon wafers and solar cells

“…In the past, various specialised tools and instruments have been developed to solve this problem. Some recent techniques include light beam induced current (LBIC) [7], lock-in thermography (LIT) [8], resonance ultrasonic vibration (RUV) [9], scanning acoustic microscopy (SAM) [10], electroluminescence (EL) [11][12][13][14][15], photoluminescence (PL) [16][17][18][19][20] and optical transmission (OT) [21][22][23][24][25]. Good topical reviews on these subjects have been published elsewhere [26,27].…”