BGA Rework and Repair may seem daunting at first glance. In fact, considering the macro scale at which our eyes perceive the world, it is daunting to dissect a PCB or BGA. Luckily, the field of optics has accelerated greatly in recent years, and microscope technology has only seen greater levels of magnification added to it. When put in conversation with X-ray technology, the combination serves as an efficient and accessible tool for BGA inspection. Of course, it still takes a keen eye to decipher that wealth of new information; what is defective and what is a process indicator may seem indistinguishable to the inexperienced observer.
Assemblers and inspectors don’t simply play it by ear, however. Though every BGA and PCB is unique, there are some objective standards one must measure from for a board or array to be considered acceptable. This article will concentrate on BGA X-ray inspection in particular.
BGAs (Ball Grid Arrays) are SMT packages with an array of solder balls on one side used to conduct electrical signals between the component and PCB. Every ball functions essentially like a pin from a leaded SMT component. Due to the sheer number of connections needed, however, pins were considered too risky to implement. Solder balls remove the concern of bridging connections due to its evenly-spaced organization, and though the process can be done by hand, most BGAs go through machines instead.
However, machines too are prone to error. This is one major reason why we use X-ray inspection. Using a 3D X-ray provides an oblique and see-through view of the BGA, eliminating any extraneous information and allowing the inspector to focus on key areas in a non-destructive manner.
Manufacturing errors such as voiding and opens are common for Ball Grid Arrays. Voiding occurs when flux becomes entrapped within the solder joint, causing empty spaces or “voids” to appear. These holes are imperceptible to the human eye and, with enough frequency, can be harmful to the BGA or board in question either by creating an open circuit or solder shorts. Herein lies the advantage of x-ray inspection. Faulty joints can be isolated, reworked, and re-checked with ease from any angle. It is recommended for x-ray cameras to be high resolution and capable of displaying high contrast so that no defects are lost in the video feed. Furthermore, multiple BGAs can be inspected at once to ensure efficiency and efficacy in the inspection.
Overall, inspecting a BGA with the naked eye or even a microscope does little to showcase the most common issues in BGA joints such as opening or voiding, which results from flux becoming entrapped within the solder. With the use of x-ray inspection, however, one can accurately assess the normally imperceptible imperfections within the joints themselves. It is often these tiny faults that cause open circuits or solder shorts. X-rays can specifically target the faulty solder and mark it for rework. It is an integral tool for any company invested in SMT rework and repairs and will only improve in the coming years.
This post first appeared on How Assemblers Use X-Ray Inspection For BGA, please read the originial post: here
