Highleap Electronic: Negative Electroplating Process in PCB Manufacturing

In the PCB manufacturing industry, the quality and efficiency of the production process are critical to the success of the final product. Negative electroplating, a key electroplating technique, is widely used in PCB production, especially for handling complex designs and improving PCB performance. Discover when to use negative electroplating in PCB production, how to create accurate Gerber files, and its benefits for complex designs and better performance.

How to Determine if Negative Electroplating Should Be Used

The decision to use negative electroplating depends on the specific requirements of the PCB design. At Highleap Electronic, the CAM engineering department follows specific guidelines for determining when this process is applicable. In addition to the basic criteria, line width and spacing capabilities also play a critical role in this decision. To ensure accuracy, CAM engineers will typically check the smallest line width areas and evaluate whether they meet the necessary requirements for the negative electroplating process. If the design does not meet these criteria, the process may be switched to graphic electroplating (using alkaline etching). However, if the conditions allow, negative electroplating should be prioritized due to its superior plating quality.

Gold-Plated, Metallized Half-Hole, and Board Edge Metallized PCBs Cannot Use Negative Electroplating

PCBs that are gold-plated, have metallized half-holes, or feature board edge metallization are not suitable for negative electroplating. The gold layer on gold-plated PCBs creates difficulties by interfering with the electroplating process, leading to inconsistent plating. Similarly, metallized half-holes cause issues with even plating, as their unique structure disrupts the uniform application of the electroplating layer.

In addition, board edge metallization complicates the plating process due to poor adhesion at the edges of the board, resulting in uneven plating. These challenges make it difficult to achieve the desired uniformity and quality when using negative electroplating. For these types of designs, alternative methods like graphic electroplating (alkaline etching) are employed, ensuring consistent and reliable plating across the entire PCB.

Metallic Non-Circular Holes Can Use Negative Electroplating

For PCBs with metallic non-circular holes (such as oval or irregular-shaped vias), negative electroplating is viable. However, the process requires the addition of burr holes to ensure an even and high-quality plating process.

PCBs with Negative Pads in Outer Layer Circuits Require Communication with the Customer

For PCBs with negative pads in the outer layer circuits, it is essential to communicate with the customer to either add solder rings or change the pads to NP (Non-Plated) holes. Negative pads can affect the plating quality, and this modification ensures a smooth electroplating process. This step must be reviewed and discussed with the customer during the order review phase.

Line Width and Spacing Capabilities Should Be Considered

The capabilities for line width and spacing can also affect the decision to use negative electroplating. To accurately assess whether the design can support the negative electroplating process, the CAM engineer should check the minimum line width in the design. If the minimum line width does not meet the requirements for negative electroplating, the design may need to be adjusted to fit the process. In cases where the design doesn’t meet the criteria for negative electroplating, it may be more appropriate to switch to graphic electroplating, which uses alkaline etching. If possible, however, negative electroplating should always be prioritized, as it offers several key advantages for certain designs.

Creating Gerber Files for Negative Electroplating

Once it has been determined that negative electroplating will be used, the next step is to create Gerber files that accurately represent the design and plating process. Gerber files are essential for translating the PCB design into a format that can be used for manufacturing. Here’s how to generate the files while ensuring they adhere to the negative electroplating process:

Confirm Pad Designs

Ensure that the pad designs in the outer layers are compatible with negative electroplating. If negative pads are present, communicate with the customer about potential modifications, such as adding solder rings or changing them to NP holes. The shapes and sizes of these pads in the Gerber files must match the process specifications.

Handling of Metallic Non-Circular Holes

If the design includes metallic non-circular holes, it’s essential to mark the positions and sizes of burr holes in the Gerber files. These burr holes are necessary for the successful application of negative electroplating, particularly for areas where conventional plating methods may not work effectively.

Mark Gold-Plated and Metallized Areas Clearly

When preparing for graphic electroplating (alkaline etching) instead of negative electroplating, it is essential to clearly identify areas in the Gerber files that cannot undergo negative electroplating. These include gold-plated areas and metallized half-holes (such as blind or buried vias). Negative electroplating is incompatible with these features, so if they are present in the design, the entire PCB will need to be processed using graphic electroplating.

To assist the production team, providing supporting images of these regions is highly recommended. By marking gold-plated sections and metallized half-holes in the Gerber files and accompanying these markings with clear images, the factory team can quickly assess whether the PCB design is suitable for negative electroplating or whether graphic electroplating is required. This makes it easier for the team to verify the process that should be applied and ensures accurate production.

By highlighting these areas and providing clear visual cues, the production process is streamlined, minimizing errors and ensuring the PCB undergoes the correct electroplating process.

Negative Electroplating Process Workflow in PCB Manufacturing

After generating the Gerber files, the next step is to document the negative electroplating processing workflow in our ERP system. This documentation ensures that the factory can carry out the process accurately and efficiently. The following outlines the typical steps for different types of PCBs, including double-sided and multilayer boards:

1. Double-Sided PCB Process (Example with HASL/ENIG)

• Material cutting → Material drying after cutting → Drilling → Deburring → Copper plating → Negative electroplating → Negative electroplating grinding → Negative dry film → Dry film inspection → Negative etching → Outer layer AOI → Grinding → Solder mask hole filling → Solder mask → Solder mask inspection → Characters → HASL/ENIG → Impedance testing → Electrical testing → Secondary drilling, V-CUT → Milling → Functional check → Final inspection → Packaging → Finished goods warehouse.
  • Note: If there is a large tin area in the character section, it should be tin-plated before character marking.
  • For “false” double-sided PCBs (without metallized holes), the process should follow the single-sided PCB workflow.

2. Multilayer PCB Process (Example with HASL/ENIG)

• Material cutting → Material drying after cutting → LDI positioning holes → Inner dry film → Inner etching → Inner AOI → Browning → Lamination → Drilling (aluminum drilling) → Metallization milling → Deburring → Copper plating → Negative electroplating → Negative electroplating grinding → Negative dry film → Dry film inspection → Negative etching → Outer layer AOI → Grinding → Solder mask hole filling → Solder mask → Solder mask inspection → Characters → HASL/ENIG → Impedance testing → Electrical testing → Secondary drilling, V-CUT → Milling → Functional check → Final inspection → Packaging → Finished goods warehouse.
  • Note: Similarly, if there is a large tin area in the character section, it should be tin-plated before character marking.

Documenting these processes in the ERP system ensures that all stages of manufacturing are followed precisely, aligning with the Gerber design files and process specifications. This reduces errors and increases efficiency, ultimately enhancing the quality and consistency of the final product.

Benefits of Negative Electroplating

Negative electroplating offers several important advantages in PCB manufacturing, particularly in terms of improving quality, reducing production costs, and enhancing performance. Here are the key benefits:

1. Improved Plating Uniformity
   Negative electroplating ensures an even plating layer, particularly for complex designs. The even current distribution results in consistent plating thickness, preventing issues such as underplating or overplating, which can compromise the PCB’s performance.
2. Cost Reduction
   Negative electroplating helps reduce material and time wastage by providing a straightforward way to plate complex PCBs without requiring additional steps or processes. This leads to lower production costs, especially for designs involving metallic non-circular holes and intricate circuit layouts.
3. Enhanced Soldering Performance
   The uniform plating provided by negative electroplating improves the adhesion of solder during the soldering process. This results in better soldering reliability, which is particularly important for small pads and fine-pitch components.
4. Flexibility for Complex Designs
   Negative electroplating is well-suited for designs with special requirements, such as metallic non-circular holes or negative pads. This process enables these unique features to be incorporated into the design without altering the PCB structure or workflow, offering designers flexibility in their creations.
5. Increased Durability and Oxidation Resistance
   The robust plating layer created by negative electroplating enhances the durability of the PCB and makes it more resistant to oxidation. This is crucial for PCBs used in demanding environments or those requiring long-term reliability.
6. Reduced Defect Rates
   The uniformity achieved through negative electroplating reduces the occurrence of plating defects, such as non-uniform thickness or poor adhesion, which helps reduce waste and increase production efficiency.

Comprehensive PCB Manufacturing Solutions at Highleap Electronic

At Highleap Electronic, we offer a wide range of production processes tailored to meet the diverse needs of our clients. While the negative electroplating process is a key part of our capabilities, if your PCB design does not meet the requirements for this process, we also provide graphic electroplating (alkaline etching) as an alternative. The following highlights explain why we choose the negative electroplating process, but it is important to note that our manufacturing capabilities extend far beyond this process. Below are some of the key features of our advanced manufacturing capabilities:

Our Manufacturing Highlights

At Highleap Electronic, we specialize in producing high-quality, reliable PCBs, with a focus on complex and demanding designs. Our manufacturing capabilities include:

• 2/2mil Line Width/Spacing for High-Density Designs
  We support high-density PCB designs that require extremely fine line widths and spacings, ensuring precision for the most intricate layouts.

• Up to 60 Layers for Complex, Multilayer PCBs
  Our facilities are capable of producing up to 60 layers, enabling the production of highly complex, multilayer PCBs that meet the most demanding specifications.

• Advanced Via Technologies, Including Blind, Buried, and Microvias
  We offer advanced via technologies such as blind vias, buried vias, and microvias to support intricate PCB designs and high-performance requirements.

• Thermal Management with Metal Core and Ceramic Materials
  Our thermal management solutions include metal core and ceramic materials, ensuring optimal performance and reliability for heat-sensitive applications.

• Comprehensive Testing to Ensure Quality and Performance for Every Application
  We conduct thorough testing to guarantee that every PCB meets the highest standards of quality and performs reliably in its intended application.

Whether you require negative electroplating or graphic electroplating, Highleap Electronic has the expertise and flexibility to deliver the precise solution for your needs, backed by our comprehensive range of advanced manufacturing capabilities.

Conclusion

By following the guidelines for determining when to use negative electroplating, creating Gerber files according to process specifications, and documenting the processing workflow in our ERP system, we ensure the smooth execution of this advanced electroplating technique. Negative electroplating offers significant benefits in terms of improving PCB quality, reducing costs, and providing flexibility for complex designs.

At Highleap Electronic, we are dedicated to delivering high-quality, reliable PCBs that exceed customer expectations. Our team of experts is always ready to support both conventional and unconventional designs, ensuring that your project is handled with the utmost precision and efficiency. With our cutting-edge manufacturing processes and commitment to excellence, you can trust Highleap Electronic to meet your most demanding PCB needs.