In the event of failure, printed circuit board (PCB) failure analysis seeks to identify the causal factors with enough precision to enable remediation of the fault. This requires systematic testing of the PCB to eliminate individual components as causal factors for the failure. The process of PCB failure analysis is as important as the integrity of the steps; skipping a step in the progression of testing and analysis can contaminate the results and prevent failure analysis engineers from drawing actionable conclusions.
Further, complicating PCB failure analysis is the spiraling complexity of today’s PCBs. From through-hole to surface mount involving 1-mil tolerances, from double-sided boards to those with as many as 14 layers, PCBs have evolved dramatically in a relatively short time. Additionally, PCBs now routinely include such exotic design elements as COB (chip on board), flip chips and Ball Grid Arrays.
The consequent compact board layout creates issues for PCB fabrication with underfill and contacts hidden from the naked eye. The additional design complexity requires PCB failure analysis to include much more granular and exacting PCB testing and PCB analysis than previous generations of boards.
PCB failure analysis calls for such advanced failure analysis techniques as radiography, acoustic microscopy and X-ray fluorescence in addition to the more traditional surface analysis. Each technique in PCB failure analysis allows analysts to eliminate certain factors and focus in on the real causes of the failure. For example, the surface analysis will highlight any contaminants on the board, such as dust, while radiography (also knows as X-ray imaging) will reveal cracks and other defects in the vias and may also enable examination of hidden solder joints. Taken together and in a progressive order, the process of PCB failure analysis will lead to valuable conclusions about the sources of the PCB failure.