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Manufacturing

Upon completing the PCB layout in KiCad, the subsequent phase involves manufacturing the physical Printed Circuit Board (PCB). This stage encompasses selecting an appropriate manufacturing method and preparing the design files necessary for production. This documentation delineates the prevalent PCB manufacturing options, elucidates the process of generating and verifying Gerber files, and provides guidance on interfacing with professional PCB manufacturers to ensure the realization of high-quality PCBs.

Manufacturing Options for PCBs​

1. Chemical Etching (DIY)​

Chemical etching represents a conventional method for fabricating PCBs in a home or laboratory setting. This technique involves the selective removal of copper from a copper-clad board to create the desired circuit patterns. While it offers a hands-on approach to PCB manufacturing, it entails significant safety hazards and procedural complexities.

  • Materials Required:

    • Muriatic Acid (Hydrochloric Acid): Utilized as the primary etching agent.
    • Hydrogen Peroxide (H₂O₂): Acts as an oxidizing agent to facilitate the etching process.
    • Copper-Clad Board: The substrate on which the PCB is fabricated.
    • Protective Equipment: Includes gloves, safety goggles, and adequate ventilation apparatus to mitigate exposure to hazardous fumes.

  • Process Overview:

    1. Transfer of Layout: The PCB design is transferred onto the copper-clad board using methods such as toner transfer or UV exposure.
    2. Etching: The board is immersed in a chemical solution comprising muriatic acid and hydrogen peroxide. The etchant selectively removes unprotected copper, delineating the circuit traces.
    3. Cleaning and Drilling: Post-etching, the board is thoroughly rinsed to halt the chemical reaction, and excess resist material is removed. Precision drilling is then performed to create vias and component mounting holes.

  • Safety Concerns:

    • Hazardous Fumes: The chemical reactions generate toxic fumes, necessitating a well-ventilated workspace.
    • Chemical Handling Risks: Improper handling of acids and oxidizers can result in severe chemical burns and environmental hazards.
    • Operational Risks: The etching process is labor-intensive and susceptible to errors, potentially leading to defective PCBs.

Given these challenges, chemical etching is primarily suited for educational purposes or prototyping under controlled conditions. For most applications, especially those requiring precision and scalability, professional PCB manufacturing services are recommended.

Professional PCB manufacturing is the industry-standard approach for producing high-quality, reliable PCBs. This method leverages advanced fabrication technologies to deliver precise and scalable solutions tailored to specific design requirements. The proliferation of cost-effective PCB manufacturers, particularly in regions such as China, has made professional services accessible and economically viable for both hobbyists and commercial entities.

  • Advantages:

    • Precision and Quality: Advanced machinery ensures accurate trace dimensions, consistent layer alignment, and high-fidelity reproduction of complex designs.
    • Scalability: Suitable for both small-scale prototypes and large-scale production runs.
    • Customization: Extensive options for board materials, thicknesses, surface finishes, and other specifications to meet diverse application needs.
    • Efficiency: Reduced turnaround times with options for expedited manufacturing and shipping.

  • Notable PCB Manufacturers:

    • Oshpark: Renowned for its simplicity and suitability for beginners, Oshpark offers an intuitive ordering process where designers can upload Gerber files or KiCad project files directly. The service is particularly favored for small batch orders and prototyping.
    • PCBWay: Catering to advanced users, PCBWay provides extensive customization capabilities, allowing designers to specify board materials, thicknesses, solder mask colors, and other intricate details. This flexibility makes it ideal for projects requiring specialized PCB characteristics.

How to Order a PCB from a Manufacturer​

Engaging with a professional PCB manufacturer involves a series of methodical steps to ensure that the final product aligns with the design specifications. Below are exemplar workflows for ordering PCBs from Oshpark and PCBWay.

Example 1: Ordering from Oshpark​

Oshpark streamlines the PCB ordering process, making it accessible and efficient for designers of varying expertise levels. The following outlines the procedure:

  1. Export Gerber Files from KiCad:

    • Navigate to KiCad’s PCB layout editor (PCBnew).
    • Utilize the Gerber export tool to generate the requisite Gerber files, encapsulating all necessary layers and specifications.

  2. Upload the Gerber Files:

    • Access Oshpark’s online platform.
    • Upload the Gerber files by dragging and dropping a compressed (.zip) archive containing the Gerber outputs.

  3. Review the Design:

    • Oshpark provides a visual preview of the uploaded PCB design.
    • Conduct a thorough inspection to identify and rectify any potential design defects or discrepancies.

  4. Place Your Order:

    • Upon verification, proceed to finalize the order.
    • Oshpark typically offers options such as three copies of a small PCB at an approximate cost of $13, catering to budget-conscious projects.

Example 2: Ordering from PCBWay​

PCBWay accommodates designers requiring advanced customization, offering a comprehensive suite of options to tailor PCB specifications:

  1. Set PCB Dimensions:

    • Determine the physical dimensions of the PCB within KiCad (e.g., 66.04mm x 25.95mm).
    • Input these measurements accurately on PCBWay’s order interface.

  2. Select Layer and Material Options:

    • Specify the number of layers (e.g., two-layer boards) and select the desired substrate material (e.g., standard FR4, aluminum, high-TG FR4).
    • PCBWay provides options for specialized materials to meet specific application requirements.

  3. Customize Further:

    • Define additional parameters such as solder mask color, board thickness, minimum hole sizes, and other advanced features.
    • These customizations enable precise alignment with the project’s technical and aesthetic needs.

  4. Get a Quote and Order:

    • PCBWay offers real-time pricing based on the selected customizations, with basic two-layer PCBs starting from approximately $5.
    • Review the quote and proceed to place the order, ensuring all specifications are accurately captured.

Understanding Gerber Files​

Gerber files are the cornerstone of PCB manufacturing, serving as the universal standard for conveying design data to fabrication facilities. These files encapsulate comprehensive information about each layer of the PCB, ensuring precise reproduction during the manufacturing process.

What Do Gerber Files Include?​

Each Gerber file corresponds to a specific layer or aspect of the PCB, collectively providing a holistic blueprint for fabrication:

  • Top Copper Layer (Front Copper): Defines the circuitry and trace patterns on the upper surface of the PCB.
  • Bottom Copper Layer (Back Copper): Details the circuitry on the lower surface of the board.
  • Solder Mask (Top/Bottom): Specifies areas where solder will be applied, protecting and insulating the copper traces while preventing solder bridges.
  • Silkscreen (Top/Bottom): Contains textual and graphical annotations, such as component labels, logos, and identification marks.
  • Drill File: Enumerates the locations and diameters of holes to be drilled for vias, through-hole components, and mounting purposes.

How to Generate Gerber Files in KiCad​

The generation of Gerber files in KiCad involves a structured process to ensure all necessary layers and specifications are accurately captured:

  1. Open PCBnew (KiCad’s Layout Editor):

    • Navigate to the completed PCB layout within PCBnew.
    • Access the Gerber export functionality through the “File” menu.

  2. Select Layers:

    • Choose the specific layers to include in the Gerber export, such as front copper, back copper, silkscreen, solder mask, and others as required by the manufacturer.

  3. Export the Files:

    • Initiate the export process, resulting in a collection of Gerber files.
    • Compress the exported files into a .zip archive, encapsulating all necessary data for submission to the PCB manufacturer.

Gerber File Format​

Gerber files are governed by standards established by Ucamco, with the Gerber X2 format representing the most current iteration. Gerber X2 enhances previous versions by incorporating additional metadata and improved interoperability. Notably, Gerber files are human-readable and can be inspected using text editors or specialized Gerber viewers, facilitating verification and troubleshooting.

Verifying Gerber Files​

Prior to submitting Gerber files to a manufacturer, it is imperative to conduct a thorough verification to ensure design integrity and prevent manufacturing errors. Utilizing a Gerber viewer enables designers to visually inspect each layer for accuracy and completeness.

  • Load the Gerber Files:

    • Open the Gerber files using KiCad’s built-in Gerber viewer or alternative external viewers.
    • Import each layer individually to facilitate detailed inspection.

  • Inspect the Layers:

    • Front and Back Copper: Verify the accuracy of trace routings, component placements, and ensure no unintended copper areas exist.
    • Solder Mask and Silkscreen: Confirm that solder mask openings align with component pads and that silkscreen annotations are correctly positioned and legible.
    • Drill File: Ensure that all via and hole locations are accurately represented and that hole sizes correspond to the design specifications.

This verification step is crucial for identifying and rectifying issues such as missing traces, overlapping elements, or misaligned layers, thereby safeguarding against costly manufacturing defects.

Conclusion​

The transition from PCB layout to physical fabrication encompasses critical decisions regarding manufacturing methodologies and meticulous preparation of design files. While chemical etching offers a hands-on approach for DIY enthusiasts, professional PCB manufacturing services are predominantly recommended due to their precision, scalability, and safety advantages. Central to this process are Gerber files, which encapsulate the comprehensive design data required for accurate PCB production. By adhering to industry standards for file generation and verification, designers can ensure the seamless translation of their electronic concepts into reliable, high-quality PCBs. Leveraging manufacturers such as Oshpark and PCBWay facilitates access to advanced fabrication capabilities, enabling the realization of sophisticated and customized PCB designs with efficiency and reliability.