In today's society, more and more industries will use PCB, but do you know the production steps of a PCB circuit board?

Here is a step-by-step explanation of how printed circuit boards (PCBs) are manufactured.

1. Preparatory Stage: Design & Material Preparation

Circuit Design: Engineers use specialized software (e.g., Altium, Cadence) to create circuit layouts, which are then converted into Gerber files. These files contain critical data for manufacturing, including traces, drill holes, and solder mask layers.

Substrate Selection: The base material is typically a copper-clad laminate (CCL), such as FR-4 (epoxy glass fiber board), with a thin copper foil layer (common thickness: 18μm, 35μm) bonded to it.

2. Drilling: Creating Through-Holes

Drilling Process: High-speed drilling machines (with drills as small as 0.1mm) create plated through holes (PTH) and mounting holes based on the design data.

Deburring: After drilling, the holes are cleaned to remove burrs, ensuring smooth surfaces for subsequent electroplating.

3. Hole Metallization (Copper Plating)

 Chemical Copper Deposition: The hole walls are first coated with a conductive layer (e.g., carbon powder or palladium colloid) to enable electroless plating. A thin copper layer (5–8μm) is chemically deposited to connect the top and bottom copper layers through the holes.

Electroplating Thickness Enhancement: An electroplating bath is used to thicken the copper layer (typically requiring ≥25μm in holes) for improved conductivity and mechanical strength.

4. Image Transfer: Circuit Pattern Development

 Photoresist Application: A photosensitive film (dry film or liquid photoresist) is applied to the copper surface. When exposed to UV light through a photomask (film), the resist hardens in the exposed areas.

Exposure & Development: After alignment with the photomask, the board is exposed to UV light. Unexposed (non-hardened) resist is dissolved by a developer, revealing the copper areas that will be etched.

5. Etching: Removing Excess Copper

Etching Process: An etchant (acidic, e.g., ferric chloride, or alkaline, e.g., sodium hydroxide) dissolves the unprotected copper, leaving only the desired circuit traces.

Resist Stripping: The remaining photoresist is removed with a strong alkaline solution, exposing the clean copper circuits.

6. Multi-Layer PCB Processing (for multi-layer boards)

Inner-Layer Etching: Each inner layer is etched separately to form internal circuits.

Lamination: Inner layers, prepreg sheets (semi-cured epoxy, PP sheets), and outer copper foils are stacked and bonded under high temperature and pressure to form a single, solid board, ensuring interlayer insulation and adhesion.

Redrilling & Plating: Holes are drilled again to connect layers, followed by another round of metallization to link the multi-layer circuits.

7. Solder Mask & Legend Printing

Solder Mask Application: An insulating ink (commonly green, but also red, blue, etc.) is applied to the board, except for solder pads and vias (openings created via exposure/development). This protects the circuits from short circuits and environmental damage.
Legend Printing: A white ink is screen-printed to mark component designators, polarity symbols, and other identification information for assembly and repair.

8. Surface Finishing: Protecting Solder Pads

- Hot Air Solder Leveling (HASL): A tin-lead (or lead-free tin) alloy is applied to solder pads to prevent oxidation and facilitate soldering.

- Electroless Nickel Immersion Gold (ENIG): A nickel-gold layer is chemically deposited for flat, oxidation-resistant surfaces, ideal for high-precision components (e.g., BGA).

- Other Methods: Options like immersion silver or OSP (organic solderability preservative) are chosen based on specific requirements.

9. Routing: Board Shaping

CNC Routing: The PCB is cut to its final shape using a CNC router, removing excess material. Edges are smoothed or chamfered for safety.

V-Cutting/Stamp Holes: For panelized boards (multiple PCBs produced together), V-grooves or half-holes are created to allow easy separation during assembly.

10. Inspection & Quality Control

Electrical Testing: Automated tools like flying probe testers or in-circuit testers (ICT) check for open circuits, shorts, and connectivity.

Visual Inspection: Automatic Optical Inspection (AOI) and manual checks ensure the solder mask, legends, and dimensions meet specifications.

Reliability Testing: High-end PCBs may undergo tests for solder heat resistance, peel strength, or thermal cycling.

11. Packaging & Delivery

- The boards are cleaned, protected with anti-static film, and vacuum-sealed to prevent moisture damage. They are shipped with quality reports to ensure compliance with standards.

Simplified Process Flowchart

Design Files → Drilling → Hole Metallization → Image Transfer → Etching → (Multi-Layer Lamination) → Solder Mask → Legend Printing → Surface Finishing → Routing → Testing → Packaging

Each step requires precise control over precision and quality, especially for advanced PCBs like HDI (High-Density Interconnect) with microvias and fine traces. The process combines "subtractive" techniques (etching away copper) and "additive" techniques (plating and deposition) to achieve both electrical functionality and mechanical durability.

Ring PCB Technology Co., Limited offers comprehensive one-stop services for PCB and PCBA, ensuring convenience and reliability at every stage.  If you are interested in our PCB circuit boards, please contact us online, or visit our website to pick up more PCB&PCBA products.

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