High spatial-resolution X-ray inspection by pixelated scintillator

Abstract

X-ray inspections using X-ray flat panel detectors (FPDs) have been widely used in electronic packaging to detect defects and contaminations. In the FPDs, scintillating materials convert X-ray into visible light, and a-Si photodiode array converts the light into electrons for imaging. However, it is desired that the spatial resolution of FPDs is improved because the light spreading inside scintillator causes crosstalk to next a-Si pixels and the resolution is degraded. In this study, the scintillator was pixelated with same pixel pitch as a-Si photodiode array by barrier rib structure to limit the light spreading, and the spatial resolution was improved. The pixelated scintillator was aligned with 83μm pixel pitch of a-Si photodiode array and set as a FPD. The FPD with 83μm pitch pixelated scintillator showed high modulation transfer function (mTF) such as >0.90 at 2cycles/mm. The MTF value was almost equal to the maximum value that can be theoretically achieved. Thus the FPD with pixelated scintillator has great potential to apply to high spatial-resolution X-ray inspection.