How to use an X-ray Machine to Inspect BGA

1. What is BGA?

The Ball Grid Array or BGA, for short, is a type of circuit arrangement on a carrier known as a surface mount package. This system allows for a circuit arrangement where there are limited spaces between the chips. This is why it is called high-density packaging.

The possibility of having soldering errors increases due to the tightly-packed pins, especially with earlier circuit-mounting technologies like the Pin Grid Array (PGA). However, with the advent of BGA, the accuracy of soldering joints has increased, but another challenge persists.

The difficulty of inspecting the high-density package exists due to the closeness and availability of so little spaces between the chip pins. BGA allows for a spherical joint-soldering of the pins and increases the pins’ number, with more space between the pins than the PGA.

Nevertheless, the BGA’s increased spacing does not suffice for manual soldering methods and physical inspection to be carried out for quality.

As opposed to the PGA arrangement – which merely allows for signal conduction between the Integrated Circuits (IC) and the Printed Circuit Boards (PCB), the BGA system allows for a better connection with improved speed.

This improved connection results from BGA utilizing the entire board surface for mounting devices rather than using only the perimeter as experienced with other grid array systems. BGA also allows a faster assembling time.

2. Why do we need X-ray for BGA inspection?

BGA has perhaps the highest number of devices mounted per unit area than other PCB mounting systems. With more chip pins and the increased utilization of more board areas, including the board’s internal and perimeters, the allowance for visual inspection is not there.

Moreover, the type of errors in BGA soldering is more in number and unique to the BGA PCB-mounting system than other mounting systems. Most of this system cannot be detected using visual inspection and will need a non-destructive and non-intrusive method.

The X-ray inspection method is a non-destructive and non-intrusive method that uses imaging to achieve quality inspection and assessment of works that are hard to see with ordinary eyes using visual inspection.

During BGA inspection with a PCB x-ray machine, errors often encountered include but are not limited to solder balls cavity-hollow, bridging of solder balls, solder ball shifting, solder starving, and loss of solder ball.

3. How do we use an X-ray machine for inspecting BGA?

Due to BGA soldering’s delicate and unique nature, a carefully designed non-destructive method is required to check the accuracy of welding effectively.

 Industry professionals often use X-rays for this purpose because it avails the inspector an accurate and fast process using imagery without any destructive activity.

 It produces better results compared with other methods like the flying needle electron testing and the visual inspection for non-destructive tests. However, the steps involved in using the X-ray machine for inspection require a high level of attention to detail.

For starters, you’ll have to take precautions to avoid any electrocution by ensuring you’re properly grounded before taking the PCB out of its case. Then you’ll need to ascertain the criteria to be used for inspection to confirm it meets with acceptable international standards.

When handling the electronic assembly during operation, you will need to locate the point of the discrepancy. Mark the area of interest before loading into the X-ray machine and adjust the image settings for a good contrast value so that you see errors in the BGA easily.

Controlling the laser pointer is also important to access the marked area of interest. This will make it visible on the screen via the operator interface.

Since it is now visible on the screen, you can now check the BGA for soldering errors, including bridges, shorts, sphericity, ball shape and size, soldering consistencies, and openings. You’ll also be able to identify other solder ball defects that exist internally, like concentricity and voids.

All errors should be captured as an image or a video from different angles while using the x-ray for the inspection. The Zoom feature will allow you to take a closer look at the BGA during the inspection.

Since many images and videos will be taken from various angles, enough folders should be created and labeled properly for storage purposes.

Once done with the inspection, the PCB should be removed from the X-ray machine and returned to its special storage case.  

4. Conclusion

Even though the BGA technology has several advantages, including high-density packaging, which makes it suitable for manufacturing smaller devices, it still does not allow for easy inspection for using visual inspection.

However, with a PCB X-ray inspection machine, carrying out a non-destructive inspection on BGA becomes easier. All external, as well as internal soldering defects are identified easily and repaired as required.

With more pins being placed within a small PCB area and with an increased production pace of BGAs, a matching technology in its accuracy and automation is BGA x-ray inspection.

 In a nutshell, BGA X-ray inspection should be a walk in the park if given meticulous attention and if the steps detailed above are followed to the letters.

Finally, whatever technologies you have been using for inspection of BGA for errors like bridging of solder balls, inconsistent solder ball size, or solder balls hollow, it would be advisable if you switch to BGA x-ray as it may give you a more accurate and faster result of the quality of your work.

So, if you want to have an easy assessment, accurate error identification, and timely quality inspection results, select an industrial X-ray machine for BGA inspection might be your best bet.

Article by Born Realist