For the first time, a new inspection system at TWI Technology Centre (Cambridge, UK; www.twi.co.uk) has combined four different techniques to give 100% defect coverage. The system has been developed within the EU Framework 6 Microscan project led by Phil Wallace and Ian Nicholson in Port Talbot, Wales.
Ten organizations 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, 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 (such as ball-grid-array packages, integrated passives, and vias/trials in multilayer boards). Other defects, such as plastic encapsulated delamination and heat-plane delamination, can only be detected reliably with SAM and active thermography.
At present this prototype is aimed at high-return PCBs, particularly for medical use, rather than high-throughput production work. Nevertheless, the whole scanning process for a PCB can take only about 50 s, depending on the number of components present.
It is planned that within the next two years, the system will be refined so that it is suitable for use by industry, an advance that will have far-reaching effects on productivity and cost savings.
For more information, visit www.microscan.eu.com.
