X-ray inspection of solder joints by planar computer tomography (PCT)

Abstract

A new algorithm for 3D-reconstruction of objects from x-ray projections, called Planar Computer Tomography (PCT), is applied to inspection of solder joints. In contrast to axial computer tomography reconstruction is based on linear object movements instead of axial rotation. By this the handling of the Printed Circuit Board is simplified and integration into the conventional x-ray inspection process is enabled. Since the algorithm is well suited for parallel computers and only a few projections are necessary a significant speed up will be achieved compared with axial Computer Tomography (CT) Computational complexity of CT is another limiting factor for application in electronic production. This problem is tackled by a reduction of the number of projections, by integration of model based knowledge and by using highly parallel computers. In the following main aspects of the new reconstruction algorithm are summarized: -Reconstruction is resticted to small volumes in suspect areas of interest (A01) Multiresolution image processing Integration of model based knowledge Algebraic Reconstruction Technique (ART) --and other 3D inspection techniques.

Overview of the Use of X-Ray Equipment in Electronics Quality Tests

“…In [21] x-ray inspection is used for technological processes in 2 and 3 dimensions, due to the use of projections from multiple projections of the test element. An important aspect in X-ray examinations is the amount of radiation dose that the tested electronics take.…”

“…In order for X-ray inspection to be an even more perfect way of imaging, further work is needed to improve it [21]. X-ray sensors were improved to provide better contrast and resolution to the resulting images.…”

“…Table 1 provides a comparison of inspections of the main types of defects on SMT boards concerning defects in brazed connectors. In [21] defects such as: solder bridges, open connects, lifted lead, aignment between pad and lead, solder thickness and others were observed using visual inspection and X-rays. [21] In [16] X-ray images (Fig 4a) were analysed.…”

“…In [21] defects such as: solder bridges, open connects, lifted lead, aignment between pad and lead, solder thickness and others were observed using visual inspection and X-rays. [21] In [16] X-ray images (Fig 4a) were analysed. To this end, an algorithm based on contour ball joints.…”

“…Projection from different directions is possible using a rotary flat panel detector transfer. Solutions are also being created based on Planar Tomography Computer (PCT) [21]. It enables much faster reconstruction based on the linear movements of the test object.…”