As a result of heightened requirements for quality,integrity and reliability of electronic products,the role of wafer auditing
and nondestructive testing of printed circuit boards and electronic assemblies has grown at an unprecedented rate.
Nondestructive testing improves a product’s performance,increases quality and reliability,and lowers return rate. It is
estimated that the cost of a failure decreases by a factor of ten when the error is identified in the course of production instead
of in the field. Optical and x-ray cameras have become the most efficient and reliable tools for nondestructive testing.
Time delay integration (TDI) method of imaging is based on the concept of accumulation of multiple exposures of the same
object. The primary advantage of this method compared to the conventional line-scan method is the possibility of detecting
low exposure levels with a superior signal-to-noise ratio when high spatial resolution is required.
In the semiconductor industry,TDI-based instruments are used for wafer and reticle inspections where ultraviolet (UV) and
deep ultraviolet (DUV) instruments are mandated by defect detection requirements. In the electronics industry,TDI-based
instruments can be efficiently used for high-speed automated optical inspection (AOI) of high-density electronic assemblies
where dimensions of components populated on the PCB (printed circuit board) become smaller,and spacing between the
components becomes narrower.
X-ray TDI cameras are a critical part of the automated x-ray inspection (AXI) systems used for inspection of multilayer
printed circuit boards and circuit card assemblies with BGA (ball grid array) and other SMT (surface-mount technology)
components. High-resolution x-ray TDI cameras allow efficient inspection of the printed pattern,wire bonding,quality of
soldering of BGA components,and other elements of a PCB structure and circuit assembly.
