New reconstruction method for x-ray testing of multilayer printed circuit board

For multilayer printed circuit board (PCB) and large-scale integrated circuit (LIC) chips, nondestructive testing of the inner structure and welding defects is very important for circuit diagram reverse design and manufacturing quality control. The traditional nondestructive testing of this kind of plate-like object is digital radiography (DR), which can provide only images with overlapped information, so it is difficult to get a full and accurate circuit image of every layer and the position of the defects using the DR method. At the same time, traditional computed tomography scanning methods are also unable to resolve this problem. A new reconstruction method is proposed for the nondestructive testing of plate-like objects. With this method, x rays irradiate the surface of the reconstructed object at an oblique angle, and a series of projection images are obtained while the object is rotating. Then, through a relevant preprocessing method on the projections and a special reconstructing algorithm, cross sections of the scanning region are finally obtained slice by slice. The experimental results prove that this method satisfactorily addresses the challenges of nondestructive testing of plate-like objects such as PCB or LIC.