1. The X-Ray Inspection Process
The current use of component packages such as BGA devices (Ball Grid Arrays) etc where the connections are underneath the device and not visible, means that standard optical inspection is impossible. The cost and complexity of these types of devices demand that the manufacturing process is stable and repeatable.
X-Ray inspection is employed to visualise these hidden joints and features during production to ensure that they meet the relevant quality requirements.
X-Rays are passed through the PCB or sample being tested to an x-ray detector, the received signals pass from the x-ray detector through an image chain which converts the data into a realtime x-ray image on a monitor for viewing.
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2. X-Ray Inspection Applications
In electronics manufacturing, x-ray inspection is used for a number of applicatons. The main use is for x-ray inspection of hidden features and solder joints,
Solder joints are inspected for voiding, bridging/shorts, wettability and presence amongst others.
Specific components can be internally examined for wire sweep, die attach voiding, cracking and failure analysis purposes.
Bare PCB's can be inspected for layer alignment, barrel/via plating and delamination too name but a few.
CT ( Computed Tomography) systems can be used for small sample non destructive failure analysis, by generating a full 3d representation of the sample, which can be sliced and sectioned to determine failure modes.
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3. X-Ray Inspection Machine Types
X-Ray inspection systems as used in electronics manufacturing can either be inline of offline with the choice of open or closed x-ray tube technology.
Open tube technology relys on the system to generate the vacuum for the x-ray generator, whilst closed tube technology comes in the form of a sealed unit.
Open tube systems only require the replacement of the filament when the lifetime is reached , whilst closed tube systems require that the whole xray unit be replaced when lifetime is reached.
The open tube x-ray systems tend to be more expensive initially, but the filaments are a relatively low cost and easy item to replace when necessary, they also tend to capable of higher operating voltages which results in greater flexability in the samples which can be inspected.
Closed tube systems on the other hand are a lower cost option initially, but the closed tube unit is a costly item top replace. These systems also tend to be capable of less power and as a result are limited in types of sample you can inspect and to what detail you can detect.
Sample/detector manipulation is also important, with the ability to view samples at different oblique views and magnifications necessary to identify failures accurately and quickly.
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4. Troubleshooting X-Ray Inspection Problems
X-Ray inspection is a very reliable process and as it is used for inspection purposes does not affect the process as such.
X-Ray inspection was in the past a black art which required a very experienced operator to identify problems from the displayed images, however manufacturers are introducing ever more powerful software with automated routines for the most common inspection tasks, such as automatic voiding calculation which makes the process altogether more reliable.
X-ray voltage and current settings determine the brightness and contrast of displayed images and must be optimised to achieve the best results.
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5. Expert Advice..
Please visit individual supplier websites for further detailed information.Browse manufacturers x-ray inspection machines here
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