Why PCB Thickness Matters More Than You Think

When engineers design circuit boards, thickness selection is often an afterthought, but this parameter directly impacts product performance, reliability, and cost. Like choosing a building's foundation, PCB thickness determines the entire structure's stability and durability.

The Most Common Standard: Why 1.6mm Dominates

If you ask any PCB manufacturer their default thickness, 90% will say "1.6mm." This standard didn't happen by accident—it's the optimal balance point validated through decades of practice:

• Provides sufficient mechanical strength to prevent warping during production

• Suitable for soldering and mounting most components

• Offers the best cost-effectiveness with ample raw material supply

• Compatible with standard connectors and enclosure designs

Interestingly, 1.6mm (approximately 1/16 inch) originated from the imperial system but was widely adopted globally. Even in the United States, where imperial units are commonly used, the PCB industry generally accepts this metric value.

Complete Standard Thickness Series

Thin Board Series (For Compact Devices)

• 0.4mm: The thinnest rigid boards, for extreme space constraints

• 0.6mm: Common in memory modules, small sensors

• 0.8mm: Smartphone internal modules, wearable devices

• 1.0mm: USB devices, small controllers, IoT modules

Standard Series (For Most Products)

• 1.2mm: Slightly thinner general-purpose option

• 1.6mm: Industry default standard (most widely used)

• 2.0mm: Applications requiring extra strength

Thick Board Series (Special Requirements)

• 2.4mm: Industrial control boards, devices with heavy connectors

• 3.0mm and above: Power equipment, backplanes, high-reliability applications
  

Five Key Factors in Thickness Selection

1. Mechanical Strength Requirements

How much physical stress must the board withstand? Consider:

• Number and location of screw mounting points

• Insertion/extraction forces of connectors

• Vibration and shock during device use

• Board size (larger boards need greater thickness to prevent bending)

2. Electrical Performance Needs

• Impedance control: Thickness affects dielectric height, influencing characteristic impedance

• Heat dissipation capability: Thicker boards have greater thermal mass

• Interplane capacitance: Distance between power and ground planes affects high-frequency decoupling

3. Manufacturing and Assembly Considerations

• Thermal stress during assembly

• Compatibility with automated handling equipment

• Adaptability to test fixtures

• Weight limitations of the final product

4. Cost Implications

Standard thicknesses (particularly 1.6mm) typically offer the lowest cost because:

• Raw material inventory is plentiful

• Production processes are mature

• Yield rates are highest

• No special equipment or setups are needed

5. Industry Conventions and Compatibility

Certain industries have developed their own thickness standards:

• Computer expansion cards: Typically 1.6mm

• Automotive electronics: Often 1.6-2.0mm

• Military/aerospace: Varies by specification, generally thicker

Common Misconceptions Clarified

Myth #1: "Thickness Should Be Perfectly Uniform"

Actually, all PCBs have thickness tolerances, typically ±10%. For a 1.6mm board, anything between 1.44-1.76mm is normal. Precision applications require early consultation with manufacturers about their capabilities.

Myth #2: "More Layers Mean Thicker Boards"

While additional layers do increase thickness, using thinner dielectric materials can keep an 8-layer board around 1.6mm. Thickness depends more on insulating material than the number of copper layers.

Myth #3: "Thickness Doesn't Affect Signal Quality"

For high-speed signals, dielectric thickness directly impacts impedance. Changing thickness may require recalculating trace widths to maintain target impedance values.

Practical Selection Advice

When unsure how to choose, follow this decision process:

1. Ask Three Basic Questions First:

   • How large is the circuit board?

   • What environment will it be installed in?

   • What's the budget?

2. Reference Similar Products:
   Examine successful designs from competitors or similar applications

3. Early Communication with Manufacturers:
   Consult about production feasibility before starting layout

4. Prototype Verification:
   If uncertain, start with standard thickness for prototype testing

5. Special Attention Points:

   • Controlled impedance designs: Determine thickness early

   • High-power devices: Consider thermal requirements

   • High-vibration environments: May require increased thickness

Special Application Considerations

Flexible Circuits

Typically 0.1-0.3mm thick, selected based on bend radius and dynamic flex cycles.

Metal-Core Boards

Used in heat-sensitive applications like high-power LEDs, with thickness determined by both insulating and metal base layers.

High-Frequency Circuits

May require specific thicknesses of low-loss materials to meet performance targets.