Authored By:
Ian J Brown PhD
RoBAT Ltd, Manchester, UK
Summary
Fully automatic X-ray Inspection (AXI) is an established technique for inspecting component mounting and solder joint integrity on PCBA's. It is occasionally used for the detection of faults on (or more precisely, under) press fit connectors.
However, existing commercial automatic X-ray inspection systems limit the application of this technique to sample boards smaller than 610mm (24") x 508mm (20") and under 5mm (0.2") thick. This is far too small an envelope to test most backplane assemblies and other large PCBA's. These systems also use higher X-ray energies than is required to find all the types of assembly faults found on backplanes thereby unnecessarily increasing the weight and cost of the safety enclosures.
Existing manual systems can handle the largest of backplanes, but expecting a human operator to consistently recognize minor defects in the several hundred images required for a single large backplane (never mind production volumes) is unrealistic.
The authors describe a novel concept for a test system where a low energy micro focus X-ray source, and a 4 mega pixel detector, are mounted in separate robotically controlled heads. Each head is also fitted with a high resolution colour machine vision camera. The resulting RXI (Robotic X-ray Inspection) system provides both high resolution AXI for detecting faults under connectors, and full colour high resolution optical AOI for detecting faults within connectors, in the same machine, and in a single test activity. This fully automatic test system is a reliable, high speed, and highly cost effective test system for backplanes and other large PCB assemblies up to 1000mm (39.4") x 1600mm (63") in size and over 18mm (0.7") thick.
Conclusions
The iNEMA 2009 manufacturing report Research and Development requirement for an automated X-ray methodology capable of doing 100% inspection of pins pressed into the same via barrel and scalable to test the largest backplanes is fully realised in this robotic test system.
Utilising a low energy X-ray source, the resulting RXI (Robotic X-ray Inspection) system provides both high resolution AXI for detecting faults under connectors, and full colour high resolution optical AOI for detecting faults within connectors, in the same machine, and in a single test sequence. This fully automatic test system is a reliable, high speed, and highly cost effective test system for backplanes and other large PCB assemblies up to 1000mm (39.4") x 1600mm (63") in size and over 18mm (0.7") thick.
Initially Published in the IPC Proceedings
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