PCB proofing refers to the preliminary production of printed circuit boards prior to full-scale manufacturing. This process is primarily utilized by electronic engineers who design circuits, finalize the PCB, and then send it for small-scale trial production, known as PCB proofing. The specific steps involved in PCB proofing are outlined as follows:
1. First, you need to provide the manufacturer with the necessary documents, process specifications, and quantities.
Using Shenzhen Zhongqicheng PCB Factory as an example, you would first access their platform, register for a customer number (please enter “R” for the code), after which a specialist will provide you with a quotation. You can then place an order and monitor the production progress.
2. Cutting
1. Purpose: To segment large sheets into smaller panels that meet engineering data specifications (MI). The aim is to produce smaller sheets that align with customer requirements.
Process: large sheet → cutting board according to MI specifications → curium board → beer fillet/grinding → panels ready.
3. Drilling
1. Purpose: To drill the required apertures at designated locations on the sheet that adheres to the specified dimensions.
Process: stacked board pin → upper board → drilling → lower board → inspection/repair.
4. Immersion copper
Purpose: The immersion copper process involves depositing a thin layer of copper onto the insulating hole walls using a chemical method.
Process: rough grinding → hanging board → automatic copper sinking line → lower board → dipping in 1% dilute H2SO4 → copper thickening.
5. Graphics transfer
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1. **Purpose**: Graphic transfer involves transferring the image from the production film to the board.
**Process**: (blue oil process): grind plate – print first side – dry – print second side – dry – explode – develop shadow – inspect; (dry film process): prepare hemp board – press film – rest – position correctly – expose – rest – develop – inspect.
2. **Graphic plating**
**Purpose**: Pattern electroplating aims to apply a copper layer of the required thickness, along with a gold-nickel or tin layer, on the bare copper surface or hole wall of the circuit pattern.
**Process**: upper board – degrease – rinse twice with water – micro-etch – rinse – pickle – copper plate – rinse – pickle – tin plate – rinse – lower board.
3. **Removal of the film**
**Purpose**: Use NaOH solution to strip the anti-electroplating coating film, exposing the non-circuit copper layer.
**Process**: water film: insert rack – soak in alkali – rinse – scrub – pass through machine; dry film: release board – pass through machine.
4. **Etching**
**Purpose**: Etching uses a chemical reaction to remove copper from non-circuit areas.
5. **Green oil**
**Purpose**: Green oil transfers the graphic from the green oil film to the board, protecting the circuit and preventing solder from adhering during component welding.
**Process**: grind plate – print photosensitive green oil – cure plate – expose – grind plate – print first side – dry plate – print second side – dry plate.
6. **Characters**
**Purpose**: Characters serve as markers for easy identification.
**Process**: After green oil application – cool and rest – adjust screen – print characters – cure rear.
7. **Gold-plated fingers**
**Purpose**: Apply a nickel/gold layer of the required thickness to the plug fingers, enhancing hardness and wear resistance.
**Process**: upper plate – degrease – rinse twice – micro-etch – rinse twice – pickle – copper plate – rinse – nickel plate – rinse – gold plate.
8. **Tin plate (parallel process)**
**Purpose**: Tin spraying applies a lead-tin layer to exposed copper surfaces, protecting against corrosion and oxidation, ensuring optimal soldering performance.
**Process**: micro-erosion – air dry – preheat – apply rosin – coat with solder – hot air level – air cool – wash and air dry.
9. **Forming**
**Purpose**: Form the shape required by the customer through die stamping or CNC machining. Options include organic forming, beer board, hand forming, and hand cutting.
**Note**: Data from CNC machines and beer boards offer higher accuracy. Hand forming is less precise, while hand-cut boards can only create simple shapes.
10. **Test**
**Purpose**: Conduct 100% electronic testing to detect functional defects, such as hard-to-spot open and short circuits.
**Process**: upper mold – release board – test – pass – FQC visual inspection – unqualified – repair – retest – OK – REJ – scrap.
11. **Final inspection**
**Purpose**: Perform 100% visual inspection for board appearance defects and repair minor issues to prevent defective boards from being released.
**Workflow**: incoming materials – review information – visual inspection – qualified – FQA spot check – qualified – package – unqualified – process – inspect OK.
This outlines the PCB manufacturing proofing process, and I hope it assists everyone.
