How do X-ray machines inspect BGA?
1. What are the main applications of BGA?
Do you often wonder how your personal digital devices are assembled? It is usually the programmed-automation assembly work geared towards a very high precision-based arrangement of individual electronic components.
Fortunately, technology keeps improving to give us components like the Printed Circuit Board (PCB), that carry Integrated Circuits (IC), using surface mounting technologies like Ball Grid Arrays (BGA).
This BGA offers more components per unit area of the circuit board than any other technology and is key to many of your personal devices, including your smartphone. However, many other applications need the BGA to fuse their components, as enumerated below.
Home electronics and communication devices use BGA to connect individual components to the PCB. Devices like your phone, TVs, camcorders, and computers are all in this category and need to connect so many ICs on a tiny area of PCBs.
Manufacturing equipment benefits from this mounting technology. Manufacturing assemblies often use robotic hands that carry integrated circuits on their boards. Hence, the BGA avails this robotic assembly to mount as many chips as possible to function optimally and accurately
Medical tools and equipment use ICs for measuring the medical vitals of patients. Some of these devices, like digital thermometers, are very small and portable. This is because they make use of BGA to assemble all the ICs on the small area on the PCB
Advanced light technology, especially the LEDs used in vehicles, computers, medical equipment indicators, and home lightings, are put together with the BGA mounting technology
Aircraft and satellites have measuring devices for measuring atmospheric conditions and sensors to detect obstacles or movement. These all have internal components that rely on the BGA technology to fuse them
Automobiles also use sensors to ensure safety and to measure the effectiveness of the moving parts. These sensors are facilitated using the BGA as surface mounting technology to install their components
All of these are applications of the BGA. These applications cannot sidestep the BGA to contribute to the ease and speed of installation of individual internal components on their respective printed circuit boards (PCB).
2. What are the defects of BGA production?
There are various defects that a soldering job can present, even more so when the components that are being soldered are so closely packed as we have in the case of BGAs.
The high-density package arrangement of Integrated circuits (ICs) on the Printed Circuit Boards (PCB) gives the BGA technology some very unusual defects to handle.
But the truth of the matter is that these soldering defects fall under four general categories as enumerated below.
Inadequate soldering – This can include errors like irregular solder ball shapes, insufficient solder ball size, uneven space between solder balls, and unsymmetrical solder ball pattern. It can be detected using BGA x-ray inspection
Excess soldering – This can include soldering errors like overlapping of solder balls. A BGA x-ray inspection machine can highlight this error
Voids – This occurs when the soldering ball is totally missing from the spot of connection with the PCB. It can occur as a result of an inadequate melting temperature for the solder ball. BGA x-ray is also enough to point out this error
Component misalignment – This depends largely on the chip mounting system employed for mounting the components on the circuit boards. Even though the mounting system is automatic and most precise in its accuracy, it is not uncommon to still find that some components are misaligned and therefore don't receive the required connection during soldering.
3. How to keep the quality while producing BGA?
Quality assessment and inspection for BGA is crucial as all the connecting solders are beneath the component and are hidden from the naked eye. Moreover, any non-conformance to quality specification during production will lead to the whole PCB's total rework.
Hence, to ensure that quality work is done, the necessary steps must be taken.
Firstly, there should be an awareness of likely defects at every stage of the assembling process. Most importantly are the two most rampant defects, including Open circuit (non-collapsible BGA soldering) and Voiding (collapsible BGA soldering).
Secondly, carry out some physical tests to ascertain the characteristics of certain production factors like the nature of the setting of soldering while at the reflow soldering stage.
Thirdly, confirm the nature of inspection of the BGA and ascertain possible challenges during the inspection stages.
Lastly, employ a suitable inspection method that will give an accurate representation of the inspected device without taking more time than necessary.
4. How to use an x-ray machine to detect BGA defects?
The high-density mounting technology of the BGA does not give an inspector the luxury of physical visual inspection to determine defects in the production of PCBs.
Nonetheless, with the aid of a cool PCB x-ray machine , an accurate image can be taken, which gives a grayscale but clear imagery to accurately determine if there are defects and the type of defects present.
The PCB x-ray machine's workings are such that x-rays are projected on the inspected device, and the image produced is displayed on the screen. Usually, a contrast setting is tweaked to give a clear image of the device being inspected.
The image produced on the screen depicts the components' absorption levels in the path of the x-ray, with dark colors showing dense materials like soldering, while light colors show less dense material like voids.
Voids can indicate a missing soldering connection and are often part of the defects that can cause a rework of the entire PCB component.
The PCB x-ray machine can either be automated or operated manually. Also, the image can be a 2-D image or a 3-D image depending on the x-ray machine's sophistication.
Nevertheless, all images produced should be properly documented and stored electronically in a folder to ensure future analysis and reference.
5. Conclusion
Adequate attention to detail is usually required when installing PCBs using the BGA surface mounting technology. This is necessitated by the high-density package that allows many circuit components to be arranged on a minimal circuit board area.
With so many industries depending on this BGA for turning out their device application, this production's quality is also vital. Hence, using a x-ray machine for inspecting the integrity of the soldering and connection is essential.
