The Risks of Using Tin-Spray Process for BGA Packages and Solutions

As integrated circuit (IC) technology evolves, coupled with advancements in equipment and high-precision PCB manufacturing, consumer electronics are trending toward being lighter, thinner, and more powerful.

Traditional through-hole or standard surface-mount components (SMT) are no longer sufficient to meet these demands. With the increasing integration level of silicon chips, the packaging method has transitioned to Ball Grid Array (BGA) technology.

The Rise of BGA Packaging

BGA package offers several advantages over older methods:

• Higher I/O pin density within a smaller area.

• l Better performance at higher frequencies.

• l Improved thermal and electrical properties.

• l Lower power consumption.

Nowadays, most high-pin-count chips utilize BGA packaes, making it the top choice for high-density, high-performance, multi-pin applications.

Where You Find BGA Packages

In our daily electronics, such as mobile phone motherboards, computer motherboards, and graphics cards, the square black chips on these boards are BGA packages. As you can see, they are very small, and if you were to open them, you’d find many densely packed chip pins underneath. Unlike traditional plug-in or surface-mounted components, where the soldering points are visible, BGA packages require proper design and appropriate processes to ensure successful soldering of these specialized components.  

Common Causes of BGA Soldering Defects

Several factors contribute to BGA soldering defects, including:

• Improper soldering temperatures

• Issues with solder paste quality

• SMT equipment precision problems

However, one often-overlooked issue comes from the PCB surface finishing process, specifically the use of the tin-spray method.

The Risks of Tin-Spray on BGA Pads

As shown in the diagram, problems like "excessively thin solder," "excessively thick solder," "solder accumulating on one side," and "indented solder points" can occur on the tin-sprayed BGA pads. So, what kinds of assembly issues can these cause for BGA?  

There are two main problems:  

1. Due to the uneven height of the solder points, when the BGA component is placed on the BGA pad, the uneven positioning can cause the thicker solder to form a proper connection with the component pin. Meanwhile, the thinner solder may either not connect at all or form weak connections with cracks, leading to poor or false soldering.  

2.During the assembly of BGA components, the high temperature causes the solder paste to flow, and excess solder from overly thick solder points can flow into the gap between two BGA pads, leading to a short circuit.  

Solutions and Recommendations

Given that BGA pads are "numerous and densely packed, requiring high flatness on the PCB surface," it is recommended to use the immersion gold process to avoid uneven soldering points and ensure smooth soldering surfaces. PCBA boards with BGA components typically have high value, and quality should be the top priority. Compared to the value of the board, the cost of the immersion gold process is not the most critical factor.

At JLC, we strongly recommend that engineers choose the immersion gold process for BGA applications. Quality issues in BGA soldering are extremely difficult to repair, but the immersion gold process provides superior soldering quality and minimizes the need for costly rework.

Conclusion

Avoiding the tin-spray process for BGA pads and opting for immersion gold is the best strategy for ensuring reliable, high-quality connections in modern, high-performance electronics. Note that JLCPCB defaults to ENIG for 6-layer and above boards!