The continuous growth in demand for faster and high-power electronic devices has driven the need for new packaging techniques with higher pin counts and improved thermal dissipation. Ball Grid Array or BGA packaging rose to popularity as a key solution in providing high I/O (input-output), replacing packages with multiple tiny leads. As device densification is the ongoing trend in modern electronics, BGA packaging has a smaller form factor which fulfils a compact design. China’s PCB assembly suppliers are active in the current market because they provide high-quality products.

In this article, the advantages and assembly challenges of BGA assembly are explored. Understanding the common challenges encountered during BGA PCB assembly will help plan for preventive measures to address potential defects and issues.

What is the BGA Assembly?

BGA is a type of surface mount device (SMD) which are permanently mounted on the PCB by melting the solder balls attached to the BGA package. A BGA package has an array of solder balls, in a grid arrangement, instead of leads, to maximize the area of connections. There are two internal construction types of a BGA which are the wire bonded type and the flip chip type. In a wire-bonded BGA package, the semiconductor chip is connected to the substrate through wire bonding while in a flip-chip BGA package, the semiconductor chip is connected to the substrate through bumps while the die is oriented upside down.

The final BGA package is assembled on the printed circuit board using Surface Mount Technology or SMT. Below are the major steps in BGA assembly:

Solder Paste Application. Solder paste is distributed on the circuit board pads using a stencil for the exact positioning of the paste.
Component Placement. The BGA component is picked up by the SMT machine and mounted on the PCB with solder paste.
Reflow Soldering. Following a controlled soldering profile, the PCB is passed through a reflow oven to melt the solder paste and establish connections with the PCB pads.
Inspection and Testing. Advanced inspection and testing techniques are being performed to detect parts with quality issues during BGA assembly. Automated Optical Inspection (AOI) machine and X-ray imaging are both essential to spot abnormalities on the assembled PCB.

What are the Key Advantages of the BGA Assembly?

BGA is an indispensable technology with multiple benefits. It is widely used in many important applications due to the following advantages.

Reduced Assembly Concerns. The absence of leads significantly reduces coplanarity issues and damaged terminals. As leads can easily be bent and twisted, handling issues are therefore minimised with BGA packages. Placement accuracy is also improved during SMT reflow processes with the self-centring capability of solder balls. The overall yield is improved having a lesser chance of assembly defects.
Improved Thermal and Electrical Characteristics. The thermal and electrical characteristics can be better with BGA assembly than with conventional leaded packages. Thermal management is improved as solder balls can dissipate heat well, being a straightforward path for heat.
Higher Device Density. BGA assembly allows the miniaturization of devices as an array of solder balls is used, providing a higher number of connections. Traditional surface mount devices with leads occupy more space and are limited to fewer connections. BGA is a valuable solution for maximising space in an electronic device.
Reliability. The presence of a solder ball on a BGA package also gives mechanical robustness in the overall assembly. BGA assemblies are more durable and reliable due to lesser susceptibility to damage. They are resilient against vibrations and other mechanical stresses.
Versatility. BGA PCB assembly has a wide scope of applications, from consumer to industrial and automotive electronics. Many applications with complex systems rely on BGA assembly due to its excellent mechanical and thermal performance.

What are the Different Challenges and Solutions in BGA Assembly?

BGA assembly can be challenging; however, early mitigation can be implemented to address issues beforehand. China PCB assembly suppliers can address many issues incurred in production. Below are some of the common issues and challenges that are encountered in BGA assembly.

Package Warpage. Larger BGA package sizes can be more prone to package warpage. Warpage issues can interfere with mounting processes; thus, the planarity of the package must be improved. This can be achieved by utilizing thermal stress simulation software and improving package design. A low-stress adhesive can also help decrease warpage. Proper heat distribution is also recommended to avoid bending the package due to an unbalanced heat profile across the board.
Rework Processing. If not carefully controlled, rework processing for BGA packages can be burdensome. Additional defects may be incurred if the rework is done incorrectly. Thus, appropriate rework steps must be followed— from removal of the part using the hot gas tool to site preparation until the new component is then replaced.
Solder Bridging. In some cases, the solder material can creep out from its designated solder pad and bridge nearby components. This phenomenon results in electrical shorting due to bridged components that are supposedly isolated from each other. To address the solder bridging issues, the right solder volume and accurate placement of components are both critical.
Concealed Solder Joints. Unlike other leaded packages where solder joints are seen outright, BGA packages have solder connections that are concealed under the package. This results in more difficult visual inspection, requiring the mandatory use of X-ray inspection and advanced automated optical inspection (AOI) machines to detect soldering issues. Machine detection systems are optimised to avoid any defect escapees.
Solder Voiding. Solder voids are air gaps on the solder which adds unwanted resistance to the circuitry. Voids also weaken the solder connection which may result in other defects such as delamination and cracking. Mitigating solder voids can be done through proper thermal profiles during reflow and choosing the right paste chemistry in the BGA PCB assembly process.
Misaligned Components. Some movements during reflow cannot be avoided which may result in misaligned components. Other factors causing misaligned components are inaccurate placement and uneven solder paste volume. To ensure well-aligned components, high-precision SMT machines must be utilized with inspection capabilities to effectively position the components during the placement process. Calibration and preventive maintenance at regular intervals will help ensure that the machines are capable of processing the parts with accuracy.