A Simple Automated Void Defect Detection for Poor Contrast X-ray Images of BGA

Abstract

For surface mount technology, the occurrence of void defects inside solder balls during the ball grid array (BGA) reflow is an important problem. In this paper, we design a simple automated system for void detection. First, it can analyze the X-ray images obtained from arbitrary rotating angles and it is robust against occluded balls caused by some interference. Second, we apply the new method, which is to average multiple outputs of local contrast enhancement over different block sizes, for treating poor contrast images in order to reduce some false voids while the accuracy of void location and void area is reasonably preserved. These conclusions were confirmed by our experiments.

An efficient method of occluded solder ball segmentation for automated BGA void defect inspection using X-ray images

“…Moreover, we also claim that this current implementation scheme mentioned in 2) using the unit cell extraction and interpolation is a non-search based method, precisely, which differs from our previous scheme applied in [8], that was a search-based method with yielding higher processing time.…”

“…Furthermore, we emphasize that the proposed method using DT and unit cell interpolation, which is a geometry-based approach, also provides the nearly optimal search [8] for identifying the centers of occluded solder balls compared to the blind search in the case of using cross-correlation method in [5]. Comparison among geometry-based methods, our method can deal with arbitrary rotating view of X-ray images, but the method in [4] is limited to the case of a regular distribution pattern, that is the solder balls locates on the 0 • , ±45 • , and ±90 • directions only.…”

“…And recently, the solder ball size and the spacing between pitches have been continuously reduced in order to achieve a demand for higher density package in manufacturing, because of this; the qualities of solder joints assembly are naturally concerned. To assure the reliability of solder joints, naturally, we can incorporate several different types of automated inspection methodologies into a screening system; especially, the inspection techniques based on X-ray imaging approaches for identifying, e.g., cracks [1], abnormal joint shapes [2], non-wet soldering [3], and void defects [4], [5], [6], [7], [8] in solder joints, non-destructively, were developed in previous studies. Importantly, the existence of voids at joints may degrade the mechanical strength of the interconnection potentially reducing the performance of electrical conductivity, which can seriously affect the longterm reliability of devices [9], [10].…”

Advancing surface mount technology quality: a computer-assisted approach for enhanced X-ray inspection of solder joints

“…An adaptive circular convolution kernel is proposed to detect voids. [7] A solder extraction model for BGA solder balls needs to be based on knowledge of the area, shape, and placement rules. Feature parameters are extracted through various classi cation steps to identify each component within the solder ball as a candidate or phantom void.…”