What is BGA X-Ray Inspection? The Only Guide You Need

A BGA, or ball grid array, is a junction that can be checked visually or with an X-ray machine called a BGA. However, the inspection is necessary to ensure the solder joints’ caliber and quality control. Besides this, you can also use an x-ray inspection to find bridging, cold solder joints, solder balls, and voiding flaws. 

Even though you can inspect a BGA component with an X-ray machine, it is quite a challenging and complex procedure due to the irregular shape of a solder joint. So let’s find out if there’s an easy and uncomplicated way to inspect a BGA solder joint. But first, let’s look at the most effective BGA inspection method and why. 

What Is the Effective Technique for Inspecting A Solder Joint?

There are a variety of effective approaches to inspecting BGAs. Each method comes with its own set of advantages and disadvantages. It all boils down to the defects you’re searching for and the solder joints you’re inspecting, so make sure you do both.

Visual examination, for instance, is the best technique if you merely want to find flaws like a closed circuit, absence of solder, etc. In other cases, if you want to inspect a solder joint, a BGA x-ray inspection is your best bet.

However, before using a BGA x-ray inspection, you need to be familiar with the defects that can be identified by an x-ray examination. The following is a list of defects that can be identified using x-ray technology:

  • Voiding defects in solder joints when insufficient solder deposits on the substrate.
  • Cold solder joint resulting in insufficient pressure, heat, or both. 
  • A bridging defect if you put the solder paste on both sides of the copper or when the paste connects the board and the package. 

The most effective way to determine when to use an x-ray machine is to understand how it performs its functions. You can use this information to determine when it will be best to apply it on your BGA ball joints and put it into practice.

What’s a BGA X-ray Machine?

The electrical equipment used to take x-rays of a solder connection is a BGA X-ray machine. However, you can replace the conventional X-ray scanner with an alternative method called the x-ray examination of BGA solder joints.

Finding voiding defects is the most important task while performing a BGA inspection. In addition to that, though, you can use it to locate colder solder joints and bridging issues.

The x-ray machine is composed of x-ray sources and detectors which projects an image to the screen. The revolving anode x-ray tube and the rotating target x-ray tube are the two different sources of an x-ray. Then the product detected by the detector after being examined by x-rays is collected.

How Does the BGA X-Ray Machine Works?

In order to examine a sample, an X-ray machine will broadcast a beam of X-rays. Before it reaches the detector, the beam travels all the way through the sample. The detector then converts the data into an electrical signal once the x-rays have been transmitted through the sample.

After that, the computer will receive the electrical signal, then process the data, and finally, display the results as a digital image on the screen. You have the option of saving this digital image to a file for usage at a later time.

Finding gaps and cracks in ceramic boards, disc brake drums, and other products can be accomplished with the help of X-ray equipment, among its many other applications.

How to Do A BGA X-Ray Inspection?

A BGA X-ray inspection is the most sophisticated technology for inspecting BGAs. X-rays operate by projecting X-ray energy onto the board from an X-ray tube. Different amounts of X-rays penetrate the board. Whereas denser regions trap more x-rays than any other region.

Once the X-rays gather at a detector, they are converted into visible light to create an image. Here you can see solder ball patterns because solder joints appear darker than their surroundings. 

However, an ideal board will appear as a consistent grid of similar black circles in the final image, with the circles denoting solder joints.

The BGA X-ray inspection produces a top-down view of the component, allowing for a thorough examination of the solder patterns and ball grid. Utilizing a tilt function, more sophisticated X-ray inspection technology can examine solder junctions from various angles to determine their shape. 

This technology is effective at detecting popcorning, solder bridges, excess solder, and other problems because it allows users to perceive differences in solder patterns and forms. However, this system struggles to detect openings.

A BGA X-ray inspection technology, like endoscopes, has a variety of uses besides BGA inspection. For instance, unleaded solder inspection, surface-mount defect analysis, and through and through-hole inspection are a few examples.

The X-ray inspection makes it possible to see through the solder joint of the device beneath the components. This capability makes automated X-ray inspection (AXI) technology for BGA inspection quite popular.

BGA X-Ray Image Analysis

When you’ve done a BGA x-ray inspection, you must wonder how to read the images. So, here’s how you can do the x-ray image analysis.

1) Solder Joint Quantitative Analysis:

The image processing software first counts the BGA solder ball joints and then measures the space between them. After that, it calculates the proportion of spacing, the number of missing balls, and the difference in spacing.

2) Finding Bridging Defect

Through meticulous picture analysis, it is possible to ascertain whether or not the solder joints contain bridging flaws. The defect known as bridging is characterized by empty space between solder balls located above the substrate’s surface. To analyze this, you will need a microscope to inspect the BGA solder joint. if the top of your solder ball shows a dome like appearance, this indicates an issue with the bridging.

3) Finding Missing Balls

We can check for missing solder balls by inspecting the photos of the solder joints. A hole in the solder junction image represents the missing ball. In space, the radiolucent substance is air. 

Multiple gaps mean that numerous solder balls are missing. The number of missing balls can be determined by counting the holes in a solder junction. For instance, three solder balls are missing if your joint has three gaps. 

4) Finding The Voiding Defect

Voiding defect is another type of solder junction imperfection that can occur. Solder paste or the air in the vacant region could be the radiolucent substance if your BGA X-Ray picture reveals an abnormally bright point. Indicative of a voiding defect is the presence of air as the radiolucent material.

Benefits of BGA X-Ray Inspection

Here are a few benefits of an x-ray inspection:

Clear BGA Visibility 

Ball Grid Array (BGA) component arrangement allows for installing tiny components on the PCB and reducing the size of devices.

BGA still has limitations, particularly in terms of quality control and inspections. Components fitted using the Ball Grid Array (BGA) technique are frequently crammed closely together on the board with little to no room between them.

Due to this compact layout, an inspector won’t be able to detect flaws in the board or the installed components visually.

The best way to evaluate the board connection quality and the components is to use a PCB X-ray machine, as its X-rays may penetrate the BGA assembly.

Using the images produced by the PCB X-ray equipment during this non-destructive test (NDT), the inspector can examine each component in detail and spot any defects.

Aid In Identifying Landing Pattern Flaws

When building components on PCBs (PCB Assembly), faults frequently happen. One such error is the way some pieces settle on the board.

The difficulty of getting the landing pattern incorrect arises if the components built on the board are outside the components provided in the library of regularly used SMD components.

Design engineers are frequently tasked with drawing up schematics of the new component and its intended placement on the board.

Without this schematic, eye inspection may make it difficult to detect any errors in the landing pattern.

However, with the help of a PCB X-ray machine, determining whether or not an installed component has the incorrect landing pattern is rather simple.

Simple to Recognize Pin-Hole Fills

In particular, for components that require a stronger connection while in layers, through-hole connections are one way to connect components on PCBs.

Pin-hole fills are one of the common faults with this connection form. This problem typically results from gas that escapes during soldering.

If the soldering heat is too high and too much gas is continuously escaping, pin-hole fills will always result from this gas, which is frequently water vapor.

Visual examination and other subpar inspection techniques could be more effective in detecting these irregularities.

On the other hand, PCB X-ray machines provide the most reliable and precise method of detecting pin-hole fills during quality assurance testing, ensuring the soldering process’s reliability.

Why Is BGA Inspection Important?

The solder junctions are hidden beneath the BGA package, making examination a challenge. As a result of its placement, the BGA is not always easily accessible for examination. Despite this challenge, inspection is crucial for BGAs for several reasons, such as:

Soldering Complexity:

The process is quite difficult since you need to heat the array to a specific temperature in order to solder the BGA components. This is because all the grid’s balls need to melt to make solder connections. Errors are likely to arise as a result of the difficult soldering process and a large number of connections. Trained specialists can discover inadequacies like this during inspections, which then allows them to stop the distribution of defective components.

Reusing Materials:

using a rework station, you can repair or replace your solder defect. Early fault detection during inspection converts material and reduces material waste.

faulty Electrical Tests

A current passing through the PCB during electrical tests to ensure it is good electric. Although this test can determine whether the BGA components are linked, it can only determine if the current is on. These tests are unreliable since they can only identify a small number of problem types and cannot localize any defects they do identify. This technique assists with other thorough inspections strategies to produce a more thorough picture of mistakes and their locations.

Quality Assurance

For BGA SMT assembly, having quality physical connections is necessary. Therefore, it is vital to examine these connections in great detail in order to maintain BGA quality control. Inspections are a great way to identify trends and reoccurring problems. These are significant because recurring faults may point to problems with manufacturing and assembly and design flaws in the PCB product.

Cost Cutting

Processes for thorough inspection reduce the number of flaws that move on to the next production stage. Inspection-passed flaws may appear later in the production cycle, increasing the cost of rework. It will cost your business more money the longer it takes to discover the flaw. Early detection, prevention, and remediation are, therefore, essential.

Inspection teams must employ comprehensive and efficient tools and processes because of how important inspection is. These teams will be able to identify all problems and their sources and locations before they become more serious and expensive concerns.

Conclusion

Smaller ICT spaces, more invisible welding joints like BGA, and higher standards for welding quality are the future development trends driven by the growth of communication, computer electronics, computer, and other industries.

Under the conditions of not harming the goods, reflecting the internal information of the product, and doing qualitative and quantitative research on the detection results, the X-ray detection method can find undetectable flaws. Identifying the issue quickly and lowering the rejection rate is advantageous.

Consequently, if your PCB BGA has some flaws, you should conduct an x-ray examination as soon as possible because x rays can assist you in locating various flaws. For example, voiding defects, bridging defects, and finding missing balls are a few examples. Other than this, x-rays shows clear picture of your soldering defects which cannot be visible using other inpecting techniques.