Single Layer Flex PCB Guidelines

As you may know, printed circuit boards have a multi-layer structure. However, high-end electronics with dense circuitry require more layers, which can increase manufacturing costs and complexities, especially in the case of flexible circuits. In this TechSparks article, we aim to help you save money by providing a guide for designing single-layer flexible PCB with a simplified circuit structure.

Table of Contents

What is a Single Layer Flex PCB

single layer flexible PCB
  • Single Layer PCB

A single layer or single sided PCB is the simplest type of circuit board, consisting of only one layer of conductive material, typically copper, laminated onto a substrate material such as fiberglass or polyimide. On a single-layer PCB, all the components, traces, and circuitry are located on one side of the board, with the other side typically featuring a ground plane or copper plane.

Single-layer PCB internal structure diagram

  • Flex PCB

Also known as an FPC, is a circuit board that can be bent or twisted without damaging its components or circuits. It is made of thin and flexible insulating materials such as polyimide or polyester.

flexible printed circuit

  • Single-Layer Flex PCB

Combines a single-layer board with a flexible board, representing the most basic form of a flexible circuit. Manufacturing multi-layer structures for flexible PCB is challenging for most manufacturers, and even professional flexible PCB manufacturers have limited capabilities, typically restricted to 10 layers or less.

There are several reasons for these limitations. Firstly, flexible substrates impose higher handling and processing requirements. Secondly, manufacturers must possess precise process control capabilities, including control over parameters such as chemical solution concentration, temperature, and time. These limitations increase the risk of damage to flexible PCB during production, leading to higher project costs. Therefore, opting for single-layer flexible PCBs becomes a more practical choice. It not only reduces material costs but also mitigates the risk of high failure rates.

Single-layer flexible PCB internal structure

Using Single Layer Flexible PCB in Project

Option Comparison

PropertiesSingle-layer Flexible PCBSingle Layer Rigid PCBMultilayer Flexible PCB
FlexibilityBendable or FoldableNot applicableBendable or Foldable
ReliabilityPoorSturdyPoor, regardless of the number of layers
Space EfficiencyApplicable to three-dimensional space, can compress the redundant space in the electronExtremely poor, not only can’t compress the space, but also has low circuit density, requiring a larger sizeOptimally, the circuits are stacked together for a more compact arrangement of electronic components
High Frequency PerformancePoorRigid materials are worse in terms of dielectric loss, so signal integrity is better than flex PCBGenerally
DifficultyAppropriateEasiestHigh Difficulty
CostCost-EffectiveCheapestHigh Price

Single Sided FPC Application Scenarios

For flexible PCB, we usually discuss its static and dynamic characteristics. The following are some common applications of single-layer flexible PCB listed by TechSparks:

  • Smart Watch
  • Fitness Tracker
  • Pacemaker
  • Hearing Aid
  • Smart Phone
  • Tablet
  • Laptop
  • Dashboard Display
  • Sensor
  • Surveillance System
  • LED Lighting
  • More

Single Layer Flexible PCB Structure​

  • Substrate: Usually made of polyimide (PI) or polyester (PET);
  • Conductor: The circuit pattern, typically made of copper, results from etching the copper layer during PCB manufacturing.
  • Adhesive: The adhesive is used to bond the copper layer and polyimide film together.
  • Overlay: Used to protect the copper traces of a flexible PCB and prevent unwanted solder bridges during assembly.
  • Silkscreen: Special symbols, marks, symbols, or letters are printed on the circuit board and provide information about components, polarity, and orientation.
  • Vias: Used to provide electrical connections between different layers of a circuit board. In a PCB, vias are used to provide connections between the top and bottom sides of the board.
  • Ribs: Flexible PCB manufacturer sometimes add ribs to the flexible circuit according to different application scenarios to strengthen solder joints, increase wear resistance, reduce strain, and improve heat dissipation.
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