2-Layer PCB Manufacturing Process
The standard PCB manufacturing process for double-sided circuit boards. This process involves creating conductive patterns on both sides of a substrate with through-hole connections.
Design Data Preparation CAM
Import Gerber files, drill files (Excellon), and perform Design Rule Check (DRC). Generate tooling holes and panelization for efficient production.
Material Cutting & Preparation LAMINATE
Cut copper-clad laminate (CCL) to panel size. FR-4 glass epoxy is standard, with copper foil thickness typically 1oz (35μm) or 2oz (70μm).
Inner Layer Imaging PHOTOLITHOGRAPHY
Apply dry film photoresist, expose using LDI (Laser Direct Imaging) or conventional exposure with photomask, then develop to create circuit pattern.
Etching CHEMICAL
Remove unwanted copper using chemical etchant (typically CuCl₂ or FeCl₃ based), leaving only the protected circuit traces. Strip remaining photoresist.
AOI Inspection QUALITY
Automated Optical Inspection to detect opens, shorts, missing features, and other defects before proceeding to drilling.
CNC Drilling MECHANICAL
High-speed drilling for through-holes and component holes using carbide drill bits. Multiple hit counts tracked for tool life management.
Electroless Copper Deposition PLATING
Desmear, activate, and deposit thin electroless copper layer (0.5-1μm) on hole walls to establish conductivity for subsequent electroplating.
Electrolytic Copper Plating PLATING
Build up copper thickness in holes (PTH) and on surface. Target plating thickness typically 20-25μm in holes per IPC-6012 Class 2.
Solder Mask Application COATING
Apply liquid photoimageable solder mask (LPI/LPISM), expose, develop to protect copper and define solderable areas.
Surface Finish FINISHING
Apply protective finish to exposed copper pads. Options include HASL, ENIG, OSP, Immersion Silver, or Immersion Tin based on application.
Silkscreen Legend MARKING
Print component reference designators, logos, and other markings using inkjet or screen printing with epoxy-based ink.
Electrical Test & Profiling FINAL QC
Flying probe or fixture test for opens/shorts. CNC routing to final board dimensions with V-scoring or tab routing for arrays.
Standard Specifications
- Board Thickness 0.4-3.2mm
- Copper Weight 0.5-6 oz
- Min Trace/Space 3/3 mil
- Min Drill Size 0.15mm
- Aspect Ratio 10:1
- Surface Finish Multiple
Quality Standards
- IPC-A-600 Acceptability
- IPC-6012 Qualification
- IPC-2221 Design
- UL 94V-0 Flammability
- RoHS Compliant
- ISO 9001 Certified
Common Applications
- Consumer Electronics High Vol
- LED Lighting Standard
- Power Supplies Heavy Cu
- IoT Devices Compact
- Automotive Reliable
- Industrial Control Robust
Multilayer PCB Manufacturing Process
Advanced PCB manufacturing for 4+ layer boards requiring lamination of multiple inner layers with prepreg and copper foil. Essential for high-density designs and impedance control.
Design Review & Stackup Definition ENGINEERING
Define layer stackup, material selection, and impedance requirements. Calculate prepreg/core thicknesses for target impedance values.
Inner Layer Core Preparation MATERIAL
Cut thin core laminate (typically 0.1-0.5mm) with copper on both sides. Clean and prepare for imaging process.
Inner Layer Imaging PHOTOLITHOGRAPHY
Apply photoresist, expose inner layer patterns using high-precision LDI, and develop. Critical for layer-to-layer registration.
Inner Layer Etching CHEMICAL
Etch away exposed copper to form inner layer circuitry. Etch factor control critical for fine-pitch designs.
AOI Inner Layer Inspection QUALITY
100% automated optical inspection of inner layers before lamination. Defects cannot be repaired after lamination.
Oxide/Brown Oxide Treatment SURFACE PREP
Create micro-rough copper surface for enhanced bonding with prepreg during lamination. Black oxide or alternative treatments.
Layup & Registration LAMINATION
Stack inner layers with prepreg sheets and outer copper foil in precise alignment using pins or mass lamination systems.
Vacuum Lamination Press LAMINATION
Apply heat and pressure in vacuum press to cure prepreg and bond all layers into solid multilayer structure.
X-Ray Drilling & Target Drill ALIGNMENT
Use X-ray to locate inner layer registration targets. Drill precision tooling holes for outer layer alignment.
Mechanical Drilling DRILLING
Drill through-holes and non-plated holes. High aspect ratio drilling requires specialized processes.
Laser Drilling (Microvias) HDI
CO₂ or UV laser drilling for blind/buried vias in HDI designs. Via-in-pad and stacked microvia capability.
Desmear & Electroless Copper PLATING
Remove drilling smear from hole walls and deposit seed copper layer for subsequent electroplating.
Pattern Plating (Outer Layer) PLATING
Image outer layers, then electroplate copper and tin (etch resist) on circuit pattern areas only.
Outer Layer Etching CHEMICAL
Strip photoresist, etch exposed copper, strip tin to reveal finished outer layer circuit pattern.
Solder Mask & Finish COATING
Apply solder mask, surface finish, and silkscreen. Same process as 2-layer but with tighter registration requirements.
Electrical Test TESTING
Complete netlist verification using flying probe or dedicated test fixture. Impedance testing for controlled impedance boards.
Final Inspection & Profiling FINAL QC
Visual inspection, dimensional verification, cross-section analysis for qualification lots, and final routing.
Packaging & Shipping LOGISTICS
Vacuum seal with desiccant, ESD-safe packaging, and documentation including test reports and certificates of conformance.
Multilayer Capabilities
- Layer Count 4-40+ layers
- Min Trace/Space 2/2 mil
- Laser Via Size 75μm
- Aspect Ratio 15:1
- Registration ±2 mil
- Impedance Tolerance ±10%
Advanced Materials
- High-Speed Megtron 6/7
- RF/Microwave Rogers RO4350B
- High-Tg TG170+ FR-4
- Halogen-Free Available
- Low-Dk Dk 3.0-3.5
- Metal Core Aluminum/Copper
HDI Structures
- 1+N+1 Standard HDI
- 2+N+2 Advanced HDI
- Any-Layer ELIC
- Via-in-Pad Filled & Capped
- Stacked Vias Up to 4
- Skip Vias Supported
Flex PCB Manufacturing Process
Flexible circuit manufacturing using polyimide substrates. Requires specialized handling and processes to maintain dimensional stability and flexibility.
Design Analysis & Material Selection ENGINEERING
Evaluate bend radius, flex cycles, and dynamic vs static flex requirements. Select appropriate polyimide and adhesive system.
Polyimide Film Preparation MATERIAL
Cut copper-clad polyimide laminate. Pre-bake to remove moisture and stabilize dimensional properties.
Carrier/Frame Attachment HANDLING
Mount flexible material on rigid carrier frame for processing stability. Critical for dimensional control during imaging.
Drilling (Through-Holes & Vias) DRILLING
UV laser or mechanical drilling for vias. Laser preferred for thin materials and small holes.
Plasma Desmear & Surface Prep CLEANING
Plasma treatment to remove polyimide smear and prepare hole walls. Also improves adhesion for plating.
Metallization & Plating PLATING
Electroless copper seeding followed by electrolytic copper build-up. Lower temperatures than rigid PCB processes.
Imaging & Pattern Definition PHOTOLITHOGRAPHY
Apply photoresist, expose circuit pattern with scale compensation for dimensional changes during processing.
Etching CHEMICAL
Pattern etching with precise control for thin copper foils and fine features. Spray etching preferred.
AOI Inspection QUALITY
Automated optical inspection adapted for flexible substrates. Critical before coverlay application.
Coverlay Application COATING
Apply polyimide coverlay (flexible solder mask) using adhesive lamination. Requires precise registration and void-free bonding.
Stiffener Attachment ASSEMBLY
Bond FR-4, polyimide, or stainless steel stiffeners to designated areas for component mounting support.
Surface Finish Application FINISHING
Apply surface finish to exposed pads. ENIG preferred for flex due to flat surface and corrosion resistance.
Silkscreen/Legend Printing MARKING
Inkjet printing preferred for flex circuits. Must use flexible inks that won't crack during bending.
Electrical Testing TESTING
Flying probe or dedicated fixtures with soft contact probes. Special handling to prevent damage to thin materials.
Singulation & Final Inspection FINAL QC
Die-cut, laser cut, or steel rule die for final profiling. Visual inspection and flex cycle testing for critical applications.
Flex Specifications
- Polyimide Thickness 12.5-125μm
- Copper Type ED or RA
- Min Bend Radius 1mm
- Flex Cycles 1M+ dynamic
- Min Trace/Space 2/2 mil
- Operating Temp -200 to 400°C
Material Options
- Standard PI Kapton®
- LCP High-frequency
- Adhesive Acrylic/Epoxy
- Adhesiveless Best flex life
- FR (Flame Retardant) UL 94 VTM-0
- Coverlay PI + Adhesive
Applications
- Mobile Devices Smartphones
- Medical Implants Pacemakers
- Aerospace Satellites
- Wearables Smartwatches
- Automotive Sensors
- Industrial Robotics
PCB Manufacturing Process Comparison
Compare key differences between 2-layer, multilayer, and flex PCB manufacturing processes to select the right technology for your application.
| Process Parameter | 2-Layer PCB | Multilayer PCB | Flex PCB |
|---|---|---|---|
| Base Material | FR-4 Glass Epoxy | FR-4, High-Tg, Rogers | Polyimide (Kapton®) |
| Layer Count | 2 layers | 4-40+ layers | 1-12 layers |
| Lamination Process | None (single laminate) | Multiple lamination cycles | Coverlay lamination |
| Via Types | Through-hole only | Through, blind, buried, microvias | Through, blind vias |
| Drilling Method | Mechanical CNC | Mechanical + Laser | UV Laser + Mechanical |
| Min Trace/Space | 3/3 mil (75μm) | 2/2 mil (50μm) | 2/2 mil (50μm) |
| Protective Coating | LPI Solder Mask | LPI Solder Mask | Polyimide Coverlay |
| Typical Lead Time | 5-7 days | 10-15 days | 12-20 days |
| Key Challenges | Limited routing, thermal | Registration, impedance control | Dimensional stability, handling |
| Cost Factor | 1x (baseline) | 2-5x (layer dependent) | 3-8x (complexity dependent) |
| IPC Standard | IPC-6012 | IPC-6012 | IPC-6013 |
| Surface Finish Options | HASL, ENIG, OSP, ImSn, ImAg | HASL, ENIG, OSP, ENEPIG | ENIG, OSP, ImSn (no HASL) |
Understanding the PCB Manufacturing Process
The PCB manufacturing process is a complex series of steps that transforms raw materials into functional printed circuit boards. Whether producing simple 2-layer boards, complex multilayer PCBs with high-density interconnects, or flexible circuits for dynamic applications, each technology requires specialized equipment, materials, and expertise.
Key Stages in PCB Board Manufacturing
All PCB fabrication processes share common fundamental stages: design data preparation, substrate preparation, pattern imaging, copper etching, drilling, plating, and surface finishing. However, the specific techniques and equipment vary significantly based on the board type and complexity.
Quality Standards in PCB Fabrication
Professional PCB manufacturers follow strict quality standards including IPC-A-600 for acceptability, IPC-6012 for rigid board qualification, and IPC-6013 for flexible circuit qualification. These standards ensure consistent quality and reliability across the industry.
Choosing the Right PCB Technology
Selection depends on factors including circuit complexity, space constraints, environmental requirements, signal integrity needs, and cost considerations. 2-layer PCBs suit simple designs, multilayer boards enable complex high-speed circuits, and flex PCBs solve space and dynamic flexing challenges.
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