Share the journey of PCB circuit board processing from design to finished product manufacturing

　　PCB (Printed Circuit Board) is the core carrier of modern electronic products and is known as the "mother of electronic products". Its processing is a complex process that integrates precision machinery, fine chemical engineering, optics, and electronic technology. This article will systematically introduce the complete manufacturing process of PCB from design files to physical circuit boards.

　　1、 Core before processing: design and data preparation

　　Processing begins with design output. The PCB design files completed by engineers (usually in Gerber format, drill files, netsheets, etc.) are the "blueprints" for manufacturing. In addition, clear process requirements documents are required, including board type, number of layers, thickness, surface treatment process, special impedance requirements, etc.

　　Key step: DFM inspection

　　Legitimate PCB manufacturers will conduct manufacturability design checks before production to ensure that the design meets the factory's process capabilities and avoids designs that cannot be produced or are prone to defects. This is the first step in ensuring quality and yield.

　　2、 Core process flow of PCB processing (taking multi-layer board as an example)

　　The entire process can be summarized as a cycle and combination of "graphic transfer etching lamination drilling electroplating".

　　1. Preparation of substrate and production of inner layer

　　Cutting: Cut large copper-clad laminates into sizes suitable for production.

　　Pre treatment: Clean the copper surface to ensure subsequent adhesion.

　　Inner layer graphic transfer (dry film method):

　　Film coating: Cover a layer of photosensitive dry film or wet film on a copper plate.

　　Exposure: Use ultraviolet light to polymerize and harden the dry film of the circuit section through a negative film containing circuit graphics (or direct laser imaging).

　　Development: Use chemical solution to wash away the uncured dry film, exposing the copper that needs to be etched away.

　　Etching: Use acidic chemical solution to corrode the exposed non patterned copper, leaving a circuit pattern protected by a dry film.

　　Film stripping: Remove the hardened dry film to obtain a clear inner layer circuit.

　　AOI inspection: Use automatic optical inspection equipment to scan the inner circuit, compare the design documents, and identify defects such as open circuits, short circuits, and gaps.

　　2. Layering: Building a multi-layer structure

　　Oxidation (blackening/browning): Micro roughening treatment is applied to the inner circuit board to enhance its adhesion with the insulation layer.

　　Stacking: The inner layer board, semi cured sheet (pre impregnated material, PP), and copper foil are stacked in the order of "copper foil PP inner core board PP copper foil".

　　Compression: Under high temperature and pressure, the semi cured sheet melts and solidifies, firmly bonding each layer into a multi-layer board.

　　3. Drilling: Establishing interlayer connections

　　Mechanical drilling/laser drilling: Use high-precision CNC drilling machines or laser machines to drill through holes and blind buried holes on the board. This is the foundation for subsequent electrical interconnection.

　　Deburring and adhesive residue removal: Clean the burrs and melted resin on the hole wall to prepare for the metallization of the hole wall.

　　4. Hole metallization and outer layer graphics

　　Chemical Copper Deposition (PTH): Deposition of a thin layer of chemical copper on the wall of a non-conductive hole to make it conductive.

　　Electroplated copper: By electroplating thick copper layers on the hole walls and surface, electrical connection reliability and current carrying capacity are ensured.

　　Outer layer graphic transfer: The process is similar to the inner layer, but this time it forms outer layer circuit and pad graphics.

　　Graphic electroplating: electroplating again, thickening the outer layer of the circuit and the copper layer inside the hole, and possibly plating tin as an etching protection layer.

　　5. Etching and surface treatment

　　Film stripping and etching: Remove the dry film resistant to electroplating, and then etch away the unprotected copper with alkaline solution to form an independent outer circuit.

　　Tin removal: Removing the tin protective layer on the circuit.

　　Solder resist layer: printed or coated with green oil (or other colors) insulation layer to protect the circuit and prevent welding short circuits. Open the window to expose the solder pads.

　　Screen printing: Printing white (or other colored) text such as component part numbers, polarity labels, logos, etc.

　　Surface treatment: Treat the exposed solder pads as needed to protect the copper surface and provide good solderability. Common processes include:

　　Spraying tin, immersion gold, immersion tin, OSP (organic solder mask), electroplating hard gold, etc.

　　6. Molding and Testing

　　Molding: Cut the panel into individual PCBs using a CNC milling machine or mold.

　　Electrical testing: Use a flying needle testing machine or needle bed testing machine to check the electrical connectivity (open/short circuit) of the PCB.

　　Inspection (FQC): Conduct visual, dimensional, hole count, and other inspections.

　　Packaging and shipping: Vacuum moisture-proof packaging to avoid oxidation and moisture.

　　3、 Key technologies and advanced processes

　　HDI technology: using processes such as laser drilling, micropores, and hole filling electroplating to achieve smaller aperture and higher wiring density.

　　Impedance control: By accurately calculating and controlling line width, dielectric thickness, etc., the impedance of high-speed signal lines is matched to design requirements.

　　Rigid flex PCB: Combining flexible PCB and rigid PCB together to meet the requirements of 3D assembly.

　　Application of special materials: High frequency high-speed plates use low loss materials (such as PTFE); High thermal conductivity plates use metal substrates, etc.

　　4、 The core capabilities of modern PCB processing plants

　　Automation and Intelligence: Fully automated production lines, AGV handling, MES system tracking to improve efficiency and consistency.

　　Refined management: strict process control, clean production environment, and a sound quality management system (following IPC standards).

　　Engineering support capability: Strong DFM analysis, rapid prototyping, and problem-solving skills.

　　summary

　　PCB circuit board processing is a highly complex and precise manufacturing process. From a design blueprint to a fully functional circuit board, every step embodies the crystallization of materials science and manufacturing technology. With the development of electronic products towards miniaturization, high frequency, high speed, and high reliability, PCB processing technology is constantly breaking through its limits, providing a solid foundation for innovation in the electronics industry.