X-ray inspection in electronics manufacturing

Along the entire production chain, the components and assemblies at A+B Electronic come into contact with X-ray technology.

Where optical inspection reaches its limits, an X-ray inspection system can help in many cases. From component inspection and the initial sample control to manual reworking - Manual X-ray Inspection (MXI) is becoming more important, especially in times of component shortages.

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Component inspection in a 1-to-1 comparison

Even before the components are assembled on the PCB, we run random X-ray tests. In this way, we can see directly whether the components are correct and at least functional on the hardware side. For this purpose, a direct 1-to-1 comparison is made. The trained colleagues use a component as a reference that is certainly intact. This is compared with other components on the X-ray system. This makes it possible to see, for example, whether the bonding wires are placed in the same places.

Special case: Detecting fake components by X-ray inspection

Generally speaking, fake components are not the order of the day at A+B Electronic. But especially in the context of the tense delivery situation, there are more and more situations in which we check components for their authenticity with the help of X-ray technology.

Since the beginning of 2021, it has become increasingly difficult to purchase components directly from manufacturers. Instead, more and more electronics manufacturers have to buy on the open market. For this purpose, A+B Electronic also works with certified brokers. Despite all caution, a certain uncertainty remains: Have the components been stored correctly? Are they really originals?

Today, counterfeits are so good that they cannot be recognised from the outside. A look at the inside can help, because in the worst case, the cases do not contain any electronics at all. An empty plastic case with little legs that cannot be used for electronics. Such brazen fakes can be easily detected by X-ray inspection. However, these extreme cases are very rare. Nevertheless, we are currently carrying out more random checks to exclude serious defects.

Two identical components in the X-ray system. The left one with intact bonding wires, the right one with a defect.

„The current rule is that the more difficult a component is to obtain, the greater the risk that something is wrong with it. Resistors and capacitors, for example, are less affected than ICs."

Kristin Teichmann
Head of Production
A+B Electronic

X-ray inspection system YXLON Cheetah

  • Transmitted light area: 460x410 mm
  • Maximum detail detectability: 0.75 µm
  • Maximum weight of test part: 5 kg

With our X-ray inspection systems we can also find hidden defects on assemblies and react flexibly to customer requirements.

X-ray component counting: checking stock levels without loss

X-ray technology is not only used for inspections, but also for checking stock levels. One might think it's simple mathematics: 2,000 components are taken from the warehouse to assemble 900 of them in one order. At the end, 1,100 components should be put back into stock. But it is not quite that simple. During the placement process, there are often minor losses - sometimes components fall out when the feeders are set up, sometimes the placement machine sorts out individual parts.

Whereas in the past component rolls had to be manually pulled through a mechanical counting machine before being stored, today there is a fully automatic component X-ray counter in the A+B Electronic warehouse. Up to 4 rolls can be checked in parallel. X-rays are used to determine how many components are on the roll. From here, the status is automatically transmitted to the internal ERP system and the components are stored until the next order. This way, we are always on the safe side when it comes to the available components in our company.

Another advantage: components do not have to be removed from their protective packaging in order to record the stock. Each component has an MSL, a Moisture Sensitivity Level, which describes its sensitivity to moisture. That's why building components are stored in airtight, shrink-wrapped packaging. Any contact with the air means that the component can draw moisture. In the assembly process, this can lead to problems. Using the component X-ray counter, the component reels can remain in their packaging and are thus exposed to fewer environmental influences.

X-ray component counting with the HAWKEYE1000

  • Scanning of up to four rolls in <10 seconds
  • From 01005 components to large connectors
  • Detection of rolls, trays and special shapes (e.g. DryPacks)

With our X-ray component counter we always have an exact overview of our stock. This allows us to optimally plan our processes and material purchasing.

X-ray inspection during initial sample control

At A+B Electronic, the X-ray inspection system is mainly used to ensure process reliability. At the beginning of a project, an initial sample is produced under series conditions, which is then checked in the X-ray inspection. In this way, hidden solder joints in BGAs or QFNs can be checked. During X-ray inspection, faults such as voids, offsets and similar defects are immediately apparent and, if necessary, can be corrected for series production. Only flawless initial samples are passed on to SMT and THT assembly. From the time of the initial sample inspection, we also carry out random checks and documentation at the customer's request.

X-ray inspection in the rework process

Directly neighbouring the X-ray system is the rework station from A+B Electronic. Here, individual components on assembled PCBs can be exchanged manually. Replacing individual, defective components is not only more sustainable, but also more cost-effective and faster than a new series production. The manual process is then checked via the X-ray system. In this way, the colleagues can see directly whether all solder joints are correct.

The limits of X-ray inspection

A manual X-ray inspection does not offer absolute security. Although the hardware of components can be inspected, it can be more difficult if there is an error in the programming. For example, there are components that can only be programmed once. It is externally functional for the X-ray unit, but it has already been used in other assemblies and cannot be used for other projects because of the programming.

Also essential to X-ray inspection is a well-trained staff. Skilled employees are particularly important at this point, as no defects are detected automatically in the MXI process. Other forms of inspection, such as automatic optical inspection (AOI), specify possible sources of error, which then only need to be assessed. The greyscales of an X-ray image, on the other hand, always leave some room for interpretation, which must be compensated for by experience. That is why we have several colleagues in our company who have undergone further training in the field of X-ray inspection.

Special case Kinder Surprise Egg

For the family day at A+B Electronic, Kinder Surprise Eggs are sometimes sent through the X-ray inspection. Even if the surprise is no longer as big when they are opened, it is still a great highlight - not only for the children.

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