Can't Tell Single-Sided, Double-Sided, and Multi-Layer PCBs Apart?

July 6, 2025

Printed Circuit Boards (PCBs) are substrates that carry electronic components and provide electrical connections between them. Structurally, PCBs can be categorized into single-sided, double-sided, and multi-layer boards.

Single-Sided PCB

A single-sided PCB is the most basic type, with components mounted on one side and conductive traces on the other. Since traces appear only on one side, it is called a "single-sided" PCB. These boards have strict design limitations (traces cannot cross and must follow independent paths), so they were primarily used in early circuits.

Single-sided PCBs typically use screen printing for trace patterns—applying resist on the copper surface, etching, then adding solder mask markings. For small-batch production, a photosensitive resist method may be used.

Double-Sided PCB

Double-sided PCBs have copper layers on both the Top and Bottom sides, allowing traces and soldering on both surfaces, separated by an insulating layer. This design significantly reduces wiring complexity, making it widely adopted.

To connect traces between layers, vias—small holes plated with metal—are used as "bridges." Double-sided PCBs offer twice the routing space of single-sided ones, solving crossover issues and supporting more complex circuits.

Multi-Layer PCB

Multi-layer PCBs stack multiple single or double-sided boards. For example:
A 4-layer PCB combines one double-sided inner layer with two single-sided outer layers.
A 6-layer PCB uses two double-sided inner layers and two single-sided outer layers.
Common multi-layer PCBs have 4 or 6 layers, though advanced designs can exceed dozens.

Key Features:

Unlike single/double-sided PCBs, multi-layer boards include internal power and ground planes for optimized power distribution. Routing primarily occurs on the top and bottom layers, with inner layers assisting. The critical challenge lies in optimizing internal layer routing for better EMI performance.

Double-Sided vs. Multi-Layer PCBs: Key Differences

1.Materials:

Double-sided: Prepreg and copper foil only.
Multi-layer: Adds inner core boards between prepreg layers.

2.Production:
Multi-layer PCBs require additional steps for inner layer fabrication (similar to outer layers).

In summary:

Single-sided: Low cost, simple circuits.
Double-sided: Balanced complexity and cost.
Multi-layer: High density, EMI shielding, for advanced applications.