PCB manufacturing process involves multiple steps, from material preparation to final inspection. Each stage plays a crucial role in transforming the raw materials into a functional prototype. Below is an overview of the standard rigid board manufacturing process and its timeline.
- PCB fabrication (duration: 1–2 days)
The first step in manufacturing is preparing the core/laminate materials as defined in the stack-up and structure the board’s conductive pathways. This process includes:
- Material preparation: After the design passes the front-end engineering review, the appropriate material type and core thickness are selected and sent to the manufacturing floor.
- Surface preparation: The copper-clad laminate is chemically cleaned to ensure proper adhesion of the resist material.
- Imaging: A light-sensitive resist layer is applied to the cores and selectively exposed to UV light through laser direct imaging. The exposed resist hardens and the unexposed areas are washed away leaving the circuit pattern on top of the copper.
- Copper etching: Chemical etching removes the exposed copper, leaving behind the desired copper features.
- Layer alignment and lamination: For multi-layer boards, inner layers are aligned, pinned and bonded together using a tightly controlled vacuum lamination press.
This phase is critical for maintaining internal layer to layer registration and proper dielectric thickness between layers.
- Drilling (duration: 0.5–1 day)
Once the panels are laminated, the next step is drilling. During this phase, holes are created for component leads and interlayer connections (vias). Here’s how it’s done:
-
X-ray drilling for alignment: In multi-layer boards, X-ray imaging detects internal pad locations to precisely align and drill tooling holes. This ensures accurate layer registration.
-
Main drilling process: CNC drilling machines accurately drill holes at defined locations. For multi-layer boards, a camera/vision system scans each panel and makes slight adjustments based on the X-ray-drilled targets, ensuring perfect alignment.
-
Hole preparation: After drilling, the boards go through a cleaning and preparation process:
-
A scrubbing machine removes burrs.
-
Ultrasonic cleaning and high-pressure rinsing clear out debris.
-
A chemical de-smear process removes epoxy residue from the hole walls.
-
Electroless copper plating coats the hole walls with a thin copper layer, making them conductive for the next plating step.
- Plating and testing (duration: 1 day)
At this stage, the PCB undergoes additional cleaning and preparation before copper plating. A layer of photoresist is applied again, but this time, the exposed areas define the circuit traces and drilled holes that will be plated. Key steps in this stage include:
- Electroplating: Copper is deposited inside the drilled holes and on the exposed traces, ensuring strong electrical connections.
- Tin plating: A protective tin layer is added to shield the plated copper from unwanted etching.
- Strip resist and etching: The resist layer is removed, and any unprotected copper is etched away, leaving only the required circuit pathways.
- Automated optical inspection (AOI): AOI machines scan the board to identify defects like missing traces, incomplete connections, or bridges that could cause shorts.
- Electrical test: Using flying probe technology, each panel is tested for opens, shorts, and high-resistance connections
- Solder mask and surface finish application (duration: 1 day)
A protective solder mask is applied to prevent oxidation and short circuits, followed by the final surface finish for soldering components. The process includes:
- Solder mask coating: A green (or other color) epoxy-based mask is applied to insulate the PCB.
- Tack drying: The solder mask is partially cured.
- Image and develop: UV light exposes the mask, and unexposed areas (pads) are washed away.
- Inspection and final curing: The board undergoes visual and automated inspections before the solder mask is fully cured with heat.
- Silkscreen/legend: Generally white ink is applied using inkjet printing. Other colors may require manual screening.
- Surface finish application: A final finish, such as ENIG, HASL, or OSP, is applied.
- Routing: The PCB is cut into its final shape using CNC routers or laser-cutting techniques.
- Final inspection and packaging (duration: 0.5–1 day)
Before shipping, every printed board goes through rigorous quality checks to ensure it meets all specifications and is free of defects.
Final inspection:
- Trained technicians carefully inspect each board to confirm compliance with customer requirements.
- Reports such as XRF gold thickness, cross-section analysis, impedance results, and material certifications are provided if requested.
Packaging and shipping:
- Boards are packaged according to the customer instructions, including vacuum sealing and serial number tracking if required.
The entire PCB manufacturing process for standard rigid boards typically takes 5 to 6 days. Each stage plays a crucial role in producing high-quality, reliable circuit boards that meet design specifications.
By understanding this timeline, PCB designers can better plan their production schedules and avoid delays.