BGA Assembly: What is it and How Does it Work?

There is a need to understand what BGA is before venturing into what BGA Assembly is all about. BGA, also called ball grid array, is a form of IC package whose pins are placed in solder ball form. In contrast to conventional technologies for packaging, BGA works with higher-density pin layouts. 

Due to technological advancements, PCB design for small and complex chips has experienced a huge rise in demand. Hence, working with a packaging method that accommodates these high I/O density chips while ensuring cost-effectiveness is important. This is where BGA plays an important role.

In this article, you will understand what BGA Assembly is, its pros and cons, and the challenges faced during assembly. We will also explain how to check the quality of solder joints. Please read on as we explain the topic further.

What is BGA Assembly?

BGA Assembly involves mounting BGAs (ball grid arrays) to a printed circuit board using solder reflow. Furthermore, these SMT components use solder ball arrays for electrical interconnections. These solder balls melt when passed through a reflow oven, creating an interconnection.

Manufacturers use BGA Assembly to mount devices with hundreds of pins. BGA Assembly differs from SMD packaging. This is because BGA Assembly is an automated process. Also, it requires accurate control during the soldering process. With BGAs, it is possible to reduce the resistance by applying thermally-enhanced mechanisms. 

Furthermore, BGA Assembly features higher functional capabilities. This feature benefits high-speed and high-power ICs requiring advanced thermal and electrical performance. 
Now, let’s consider the benefits of BGA Assembly compared to conventional packages.

Advantages of BGA Assembly

Below are the benefits of BGA Assembly.

Increase in density

BGA Assembly involves the use of more solder balls. This causes an increase in the connection between these balls. The connection leads to an increase in the density of connections. Also, these numerous solder balls present reduce the space available on the circuit board. This leads to lighter and smaller products.

Better electrical performance

BGA Assembly offers better electrical performance. This quality is due to the shorter path between the circuit board and the die. BGA assembly dissipates heat often due to its tiny size. Also, this package lacks pins, which can easily bend and break, increasing its electrical performance and stability.

Improved heat dissipation

BGA Assembly ensures improved heat dissipation. It possesses this quality due to its low thermal resistance and tiny size. 

Self Alignment

The PCB space is well utilized. This is because the soldering balls usually self-align underneath the board. BGA Assembly ensures the use of the entire circuit board.

What are the Steps Involved in BGA Assembly?

The process of BGA Assembly deals with the mounting and soldering the BGA components on PCBs. Here are the steps:

PCB Design and Preparation

This step involves preparing printed circuit boards. The process is possible by applying solder paste to pads where the BGA mounting will happen. The solder paste comprises flux and solder alloy, which aids in soldering.

Solder Paste Application

This step involves the application of solder paste on the PCB metal pads through stencil printing. The stencil’s thickness helps determine the quantity of solder paste to use. Utilize laser-cut stencils to ensure a uniform solder paste transfer to the PCB.

Components Placement

BGA components are usually more easily mounted than QFP components, which have a pitch of 0.5 mm. The physical characteristics of BGA components cause them to have high manufacturability.
This step is also called the “Pick-and-place” step. The process describes how an automated machine picks and places the BGA components on the printed circuit boards. The machines usually rely on high-quality cameras. This is to ensure the accurate placement of the components.

Reflow Soldering

Here, a reflow oven helps to heat the board. The reflow oven melts the solder paste. This causes a strong bond between the circuit board and the BGA components. Also, small metallic balls underneath the BGA components melt inside the solder joints.

Inspection and Testing

Inspection is important to ensure that the BGA components are properly fixed. Also, there shouldn’t be defects like shorts, open connections, etc. 

Due to the physical structures of the BGA components, visual inspection won’t work. Therefore, an X-ray inspection helps to check soldering defects. These defects include short circuits, voids, air holes, and more.Electrical tests help to find defects like short and open circuits.

Challenges Faced During BGA Assembly

Although BGA Assembly offers many benefits, it comes with challenges. Below are some challenges faced during BGA Assembly.

Soldering Defects
The soldering process isn’t easy, and even the use of machines isn’t accurate. Therefore, it is possible to face soldering defects during BGA Assembly. These defects include excessive soldering, openings, solder bridges, component shifting, etc.

Repair and Rework
Repair and rework tasks on BGA Assemblies are usually challenging. This is because of its dense components. Also, there is a need for specialized skills and tools.

Inspection Limitations
The BGA assembly is always very close to the solder balls. This makes it very challenging to perform an inspection on the package.

Time-Consuming Process
The process of BGA Assembly could be time-consuming. This is because the engineer must properly attach the components to the board before soldering.

How to Check the Quality of Your Solder Joint

Solder joints are very complex and have irregular shapes. Therefore, checking the quality by visual inspection would take time and effort. Thus, for more complex issues, it’s advisable to use X-ray imaging. Let us consider both methods.

Visual Inspection (Optical Inspection)
This method for checking solder joint quality is only effective for detecting defects. These include closed circuits, the absence of solder in joints, and more. The method is straightforward because you only need the naked eye to inspect.

X-ray Inspection

This method detects bridging, incomplete wiring, voiding, and other defects. Also, it can detect majority of defects on leads and pads.
This method involves inspecting the solder joints using an X-ray device. The X-ray machine is composed of the X-ray source and detector. Both are connected to the system and used to transfer the image to a screen. X-ray inspection is fast and automated, thereby saving time.

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Conclusion

BGA Assembly is necessary for different industries. This is because of its reliability, effectiveness, and efficiency. Today, BGA Assembly has become an important advancement in technology. There could be soldering defects, and the process could be time-consuming. Yet, BGA Assembly offers many benefits. These include better electrical performance, increased density, and improved heat dissipation.

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