PRINTED CIRCUIT BOARD (PCB)

Printed circuit boards (PCBs), also known as printed wiring boards (PWBs), are sandwich structures made of conductive and insulating layers that are laminated. Each sandwich structure has a pattern of traces, planes, and other features that resemble wires on a flat surface. These features are etched from one or more copper sheet layers that are laminated onto or between paper layers of a non-conductive substrate.

 
fig1.1 A PRINTED CIRCUIT BOARD

In an electrical circuit, PCBs are used to "wire" or connect components to one another. In order to mechanically and electrically attach the components to the board, soldering is typically used to attach electrical components to conductive pads on the outer layers. Vias, which are metal-lined drilled holes that allow electrical connections between conductive layers, are added to boards with many sides in a different manufacturing process. 

There are different types of PCBS. They include:

  • Single-sided: Only one surface is used to mount the components on this board. Usually, a solder mask is applied to the back surface after it has been completely copper (ground).
  • Double-sided: Components are positioned on both sides of this kind of circuit board. Since each surface in the PCB stack-up is designated as a signal layer, the surfaces will have traces that transmit signals from one component to another.

  • Multi-layer PCBs - These boards have conductors on internal layers that carry electrical signals between components, or the internal layers could be conductive plane layers. Multi-layer PCBs may be single-sided or double-sided.
  • Rigid-flex PCBs- Rigid-flex PCBs use a flexible polyimide ribbon that connects two or more rigid sections in a printed circuit board assembly. A rigid-flex board might be used when the design must have some movable element, such as a folding or bending enclosure.
  • Flex PCBS - Fully flexible PCBs do not use any rigid materials and are made entirely of flexible polyimide ribbons. These boards can have components mounted and soldered on the, just like rigid and rigid-flex printed circuit boards.
  • Printed flex PCBs - These PCBs use a flexible material as the base, and copper conductors are printed onto the flexible material in an inkjet process or in a similar additive process. The resulting boards are very similar to flex PCBs.
  • Metal-core PCBs(or insulated metal substrate (IMS) PCBs) - These boards use a metal slab in the core layer (normally aluminum) in order to provide much greater rigidity and heat dissipation than in typical rigid printed circuit boards. The metal-core PCB design manufacturing process is quite different from the standard rigid PCB design manufacturing process, and there are a few design points to consider to ensure solvability. These boards are common in high-power lighting and some industrial applications.
  • Ceramic PCBs - These boards are less common and are used in applications that require very high thermal conductivity such that the board can dissipate large amounts of heat away from components.
  • HDI PCBs - These PCBs use very high pin count components that require a specialized manufacturing process and specialized materials to accommodate a very high density of copper connections.
  • USDI and Subtrate-like PCBs - These PCBs are so small and dense that they have bypassed capabilities of subtractive etching, and instead they require a specialized additive manufacturing process used to build IC packages.
KEY STEPS IN DESIGNING A PCB

Step 1: Define Your Requirements

Before starting, clearly define:

  • The circuit functionality
  • Number of components
  • Power requirements
  • Board size constraints
  • Single-layer or multi-layer PCB

Step 2: Create a Schematic Diagram

Use PCB design software like KiCad, Eagle, Altium Designer, or EasyEDA to create a schematic:

  1. Add components from the library.
  2. Connect components using wires or nets.
  3. Assign values (resistors, capacitors, ICs, etc.).
  4. Verify the schematic for errors.

Step 3: Select PCB Design Software

Choose an appropriate PCB design tool. Some popular options:

  • KiCad (Free, open-source)
  • Eagle (Widely used, free for small projects)
  • Altium Designer (Advanced, paid)
  • EasyEDA (Online-based, beginner-friendly)

Step 4: Create a PCB Layout

  1. Import your schematic into the PCB layout editor.
  2. Define the board outline.
  3. Place components strategically to minimize trace length and avoid overlaps.
  4. Define power and ground planes (especially in multi-layer boards).
  5. Route traces between components, following best practices:
    • Use thicker traces for high-current paths.
    • Keep signal traces short to reduce noise.
    • Use vias for multi-layer designs.

Step 5: Design Rule Check (DRC)

Most PCB design software has a Design Rule Check (DRC) feature:

  • Ensures minimum spacing between traces and pads.
  • Checks for unconnected or overlapping traces.
  • Identifies possible short circuits.

Step 6: Generate Gerber Files

Once the layout is finalized:

  1. Export Gerber files (standard format for PCB manufacturing).
  2. Generate drill files (for component holes).
  3. Review files using a Gerber viewer.

Step 7: Order the PCB

Send your Gerber files to a PCB manufacturer. Some popular PCB fabrication services:

  • JLCPCB
  • PCBWay
  • OSH Park
  • Seeed Studio

Specify:

  • Material (FR4, flexible PCB, etc.)
  • Board thickness
  • Copper thickness
  • Solder mask and silkscreen color

Step 8: Assemble and Test

  1. Solder components onto the board (manually or using a reflow oven).
  2. Test the PCB for continuity and functionality.
  3. Troubleshoot any issues by checking connections, power supply, and signals.

Bonus Tips for Beginners

  • Start with single-layer PCBs before moving to multi-layer designs.
  • Follow standard trace width guidelines (e.g., 1mm for high current traces).
  • Avoid 90-degree trace bends to minimize signal issues.
  • Keep ground planes large for better stability.
  • Double-check component footprints before ordering.

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