How to Solve the Acute Angle Problem in PCB Manufacturing

I. Introduction

In the manufacturing process of Printed Circuit Boards (PCBs), the acute angle problem is a common and significant issue that requires attention. Acute angles refer to the sharp or odd angles present on copper components in PCBs. During manufacturing, these acute angles can lead to a series of adverse consequences, with the most prominent one being the accumulation of acid, which in turn corrodes the copper components. Therefore, taking effective measures to solve the acute angle problem is crucial for ensuring the quality of PCBs.

II. Causes and Impacts of the Acute Angle Problem

(A) Causes

During the PCB design phase, designers may inadvertently or due to insufficient understanding of the manufacturing process use acute or odd angles when connecting traces to pads. For example, in manual routing, to pursue compact layout of the circuitry or complete the design quickly, designers may not follow proper angle design principles, resulting in acute angles. Additionally, some automatic routing tools, if not properly set up and optimized, may also generate traces with acute angles.

(B) Impacts

1. Acid Corrosion Problem: In the etching process of PCB manufacturing, acidic solutions are used to remove excess copper foil. When there are acute angles on copper components, acidic solutions tend to accumulate at these locations. Due to the prolonged action of the acid, the copper at the acute angles will be over-etched, causing the traces to become thinner or even break. This seriously affects the electrical conductivity of the circuit.
2. Signal Integrity Issues: The abrupt change in the geometric shape of traces at acute angles can cause signal reflection and scattering. In high-speed signal transmission PCBs, such signal reflection and scattering can lead to signal distortion, attenuation, reduced signal quality, and transmission rate. It may even trigger signal errors, affecting the normal operation of the entire electronic system.
3. Increased Manufacturing Difficulty: The presence of acute angles increases the difficulty of the PCB manufacturing process. For example, in drilling and plating processes, stress concentration is likely to occur at acute angle locations, resulting in poor drilling quality and uneven plating layers. This increases the scrap rate and raises manufacturing costs.

III. Methods to Solve the Acute Angle Problem

(A) Prevention during the Design Phase

1. Follow Angle Design Specifications
   • When designing PCBs, avoid placing traces at acute or odd angles into pads. It is a common and effective method to keep the angles near the pads at 45 degrees or 90 degrees. A 45-degree angle can make the trace transition smoother and reduce signal reflection, while a 90-degree angle is relatively simple and clear, facilitating manufacturing and inspection. For example, when connecting integrated circuit pins to traces, using 45-degree or 90-degree angles for connection can ensure both reasonable circuit layout and the avoidance of acute angles.
   • For special cases where non-45-degree or 90-degree angles must be used, try to adopt larger obtuse angles and avoid acute angles less than 90 degrees. At the same time, ensure a natural transition of the angles without obvious abrupt changes.
2. Utilize Design Tool Functions
   • Modern PCB design software usually has functions for angle checking and correction. During the design process, these tools can be used to check in real-time whether the trace angles meet the requirements. For example, some software can set an angle threshold. When it detects that a trace angle is less than the set value, it will automatically issue a warning to prompt the designer to make modifications.
   • Some design software also provides automatic routing optimization functions. By properly setting parameters, the software can avoid the generation of acute angles during automatic routing as much as possible. After automatic routing is completed, manually adjust local unreasonable traces to ensure that there are no acute angle problems in the entire PCB design.
3. Conduct Design Rule Check (DRC)
   • Design rule check is an important part of the PCB design process. After completing the preliminary design, run the DRC function to check whether the design complies with the preset rules, including angle rules. DRC can quickly detect acute angle problems in the design and generate detailed reports. Designers can then correct the problems one by one according to the prompts in the reports.
   • Regularly update and improve the design rule library to ensure that the angle rules in the library match the actual manufacturing process requirements. As manufacturing technology continues to develop, the requirements for angles may also change. Timely updating the rule library can improve the quality and accuracy of the design.

(B) Handling during the Manufacturing Phase

1. Collaborate with Manufacturers
   • Before PCB manufacturing, designers should communicate fully with manufacturers, providing detailed design files and manufacturing requirements, especially emphasizing the precautions regarding the acute angle problem. Manufacturers can evaluate the design based on their own process capabilities and experience and provide improvement suggestions.
   • After receiving the design files, manufacturers will conduct Design for Manufacturability (DFM) analysis, which also includes checking for acute angle problems. If acute angle problems are found in the design, the manufacturer will promptly provide feedback to the designer, and both parties will jointly discuss solutions to ensure the smooth manufacturing of the PCB.
2. Adopt Special Manufacturing Processes
   • For some complex PCBs where acute angles cannot be completely avoided through design modifications, manufacturers can adopt special manufacturing processes to reduce the impact of acute angles. For example, in the etching process, more precise etching equipment and process parameters can be used to control the flow and action time of the acidic solution, reducing the accumulation and corrosion of acid at acute angles.
   • In the plating process, the plating solution formula and plating conditions can be optimized to improve the uniformity and adhesion of the plating layer at acute angle locations, enhancing the corrosion resistance of these areas.

IV. Conclusion

Solving the acute angle problem in PCB manufacturing requires efforts from both the design phase and the manufacturing phase. In the design phase, following angle design specifications, utilizing design tool functions, and conducting design rule checks are key to preventing acute angle problems. In the manufacturing phase, collaborating with manufacturers and adopting special manufacturing processes can effectively deal with potential acute angle problems in the design. By implementing these comprehensive measures, the adverse effects of the acute angle problem on PCB quality and performance can be effectively avoided, improving the reliability and stability of PCBs and ensuring the normal operation of electronic products.

• ShwayPCB, Specialized Production: FP4, High TG, halogen-free, aluminum/copper/ceramic-based, and Rogers material printed circuit boards (PCBs).

  Offerings: Double-sided boards, multilayer boards, HDI (High-Density Interconnect) boards, rigid-flex boards, high-frequency boards, etc., to cater to diverse requirements.

  Surface Finish Processes: OSP (Organic Solderability Preservative), HASL (Hot Air Solder Leveling), ENIG (Electroless Nickel/Immersion Gold), immersion silver, immersion tin, electroplated nickel-gold, and electroless palladium, etc.

  Product Application Areas: Industrial control, telecommunications equipment, consumer electronics, automotive electronics, medical devices, aerospace, computers and data centers, energy and power, IoT (Internet of Things) and smart home, military and defense, marine electronics, AI (Artificial Intelligence) terminals.
  Contact us immediately at yuan@shwaypcb.com to obtain preferential quotations.