Using Non Destructive Testing in BGA X-Ray Inspection

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In post assembly operations of most of today’s PCB assemblies the boards are subject to X-

Ray Inspection. This inspection can either be accomplished on a sampling plan basis, once

the process is deemed to be in control, or it can be done on 100% of the boards if the

assembly has a high value or is of critical functioning. The 100% inspection can be

accomplished with an AXI (automated x-ray inspection) capable machine.

On a sampling plan basis the assembly can be inspected by manually examining, with the x-

ray system, the various solder joint criteria required. Initially the x-ray inspection will

include the examination for gross anomalies such as solder ball diameters, solder joint

voids, bridges or missing solder balls. Most reasonably modern x-ray systems will have the

ability to plug in the minimum and maximum ball diameters in terms of acceptability and

the machine can then “flag” those particular locations that are not within the specified

tolerance. In the same manner solder joint voiding criteria, currently at 30% of the

inspectable area, can be set as the maximum calculated void criteria. Bridges and missing

solder balls or usually easily discerned by skilled and experienced x -ray technicians.

Using x-rays as their source, the x-ray machine can provide step and repeat functionality to

inspect components which are hidden from view. Most machines, once the acceptability

parameters and limits are programmed in to the machine, can then make the comparison

to the desired values and report those parameters on the PCBA found to be outside of these

parameters. AXI is used as the software inspection routine to determine opens, shorts,

excessive solder, missing parts and mis-aligned components as part of the inspection

routine once it has been programmed.

BEST can provide outsourced BGA inspection services including X-RAY and AXI inspection

services in order to perform the above inspections.

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