Understanding ICD Issues in PCB Manufacturing: Causes and Solutions

In the vast realm of the electronics manufacturing industry, PCBs (Printed Circuit Boards) are undoubtedly the shining stars. They are not only indispensable components in electronic devices but also serve as bridges connecting various electronic components. However, during the production of PCBs, engineers often face a frustrating issue known as ICD (Inner Connection Defects). Today, let’s discuss this dreaded ICD problem in the PCB industry, explore what it is, how it arises, and how we can address it.

What is ICD?

In simple terms, ICD refers to issues with the connections between the inner layer circuits of a PCB, leading to poor electrical performance or even complete failure. Imagine if the pillars of a bridge were unstable, or if the bridge surface had cracks; could that bridge still be safe to cross? Similarly, if the connections in a PCB’s inner layer are not secure, the performance of the entire circuit board will significantly decline, potentially rendering it unusable.

How Does ICD Arise?

The root cause of the ICD issue often lies in the PCB manufacturing process, particularly in the critical stages of drilling and de-bonding.

Drilling Stage: The Resin “Furnace” Under High Temperature

During the PCB drilling process, the drill bit needs to rotate at high speed and penetrate the material to create vias for wire connections. However, this process is not always smooth. The drill bit generates extremely high temperatures during high-speed rotation, sometimes exceeding 200°C. Such high temperatures can cause the resin materials in the board to melt again, forming what is known as “glue residues.” These residues cling stubbornly to the inner copper and hole walls, complicating subsequent production.

If drilling parameters are improperly set, such as using a dull drill bit or incorrect rotation speed, it can intensify friction between the drill bit and the material, generating more heat and glue residues. If these residues are not thoroughly removed, they can form an isolation layer during the plating process, obstructing effective connections between the inner copper and plated copper, ultimately leading to ICD issues.

De-bonding Stage: A Dual Challenge of Chemistry and Physics

The de-bonding process after drilling is a critical step for removing glue residues and ensuring interconnections of inner layer circuits. However, this stage is also fraught with challenges. Traditional chemical de-bonding methods can remove residues to some extent, but their effectiveness often falls short for high-frequency and high-speed materials. These materials, characterized by a high content of resin fillers and rigid physical properties, make the de-bonding process even more difficult.

Additionally, the chemical agents used in the de-bonding process require precise control over their concentration, temperature, time, and other parameters. Any deviation in these parameters can lead to inadequate or excessive de-bonding, thereby triggering ICD issues. For example, if the concentration in the potassium permanganate solution is too low, it will not effectively decompose the resin on the hole walls; if too high, it may corrode the base copper layer, causing new damage.

How Serious is the ICD Problem?

ICD issues can significantly impact not only the electrical performance of PCBs but also the overall quality and reliability of the products. Minor ICDs can lead to signal distortion and transmission delays, while severe ICDs can cause fatal failures like open circuits and short circuits, rendering products inoperative.

For high-frequency and high-speed materials, the impact of ICD issues is even more pronounced. These materials, prized for their excellent electrical properties and heat resistance, are widely used in high-speed data transmission and wireless communication. However, once ICD issues arise, they can severely affect signal transmission quality and stability, potentially leading to complete system failure.

How to Address ICD Issues?

In the face of ICD issues, we cannot remain idle; we must take proactive and effective measures to address them.

Optimize Drilling Parameters

First, we should reduce the generation of glue residues from the source. By optimizing drilling parameters, such as selecting the appropriate drill bit type and adjusting speed and feed rates, we can reduce friction and heat between the drill bit and the material, thus minimizing glue residue production. Additionally, regularly inspecting and replacing drill bits to ensure their sharpness and precision is an effective method to reduce glue residues.

Improve De-bonding Processes

Next, we should focus on enhancing the de-bonding process. Given the unique characteristics of high-frequency and high-speed materials, we can adopt more advanced de-bonding techniques, such as plasma de-bonding and ultrasonic-assisted de-bonding. These methods can more effectively remove glue residues from the hole walls while minimizing damage to the base copper layer. Furthermore, we need to strictly control all parameters during the de-bonding process, such as the concentration, temperature, and time of chemical agents, to ensure consistency and stability in de-bonding results.

Strengthen Quality Inspection and Monitoring

Finally, we must enhance quality inspection and monitoring. Through techniques like cross-sectional observation and electrical performance testing, we can comprehensively assess the interconnection status of the PCB’s inner layer circuits, promptly identifying and addressing ICD issues. Establishing a complete quality traceability system to record and monitor every production stage ensures that issues can be traced and resolved.

Conclusion

ICD issues are a significant concern in the PCB manufacturing process. They not only affect the electrical performance and reliability of products but also have a massive impact on the entire production flow. Therefore, we must take proactive and effective measures to address ICD issues, starting from critical stages like drilling and de-bonding. Only by doing so can we ensure the quality and reliability of PCBs, contributing to the advancement of the electronics manufacturing industry.