PCB inspection

A new inspection system for PCBs at TWI's Technology Centre in Wales has combined four different techniques to give 100% defect coverage.

The system has been developed within the EU Framework 6 Microscan project and led by Phil Wallace and Ian Nicholson in Port Talbot.

Ten organisations collaborated to produce the machine which combines automated optical inspection (AOI), thermography, scanning acoustic microscopy (SAM) and X-ray inspection.

Although some of the techniques are already used in industry, with the exception of AOI, they are typically used offline and therefore can only be used to conduct batch tests with limited defect detection capability.

AOI is also currently limited to line-of-sight inspection and cannot be applied to hidden joints and devices/features (eg ball grid array packages, integrated passives and vias/trials in multi-layer boards).

Other defects, such as plastic encapsulated delamination and heat plane delamination, can only be detected reliably with SAM and active thermography.