Single-Sided PCB: A Comprehensive Guide

September 14, 2023

Table of Contents

Introduction

A single-sided printed circuit board (PCB) is the most basic type of PCB with a single copper layer, allowing components to be mounted on one side. Single-sided PCBs paved the way for modern PCB technology and play an essential role in many electronic devices today due to their simple design and low cost.

This comprehensive guide will cover everything you need to know about single-sided PCBs, including:

What is a single-sided PCB? Single-sided PCB design, Single-sided PCB stack-up

Benefits of single-sided PCBs, Limitations of single-sided PCBs, Single-sided PCB manufacturing process, Single-sided PCB materials, Single-sided PCB cost

Single-sided PCB thickness, Comparing single vs. double-sided PCBs, Single-sided PCB applications, Design tips for single-sided PCBs, Single-sided PCB vs. multilayer PCB

Finding a reliable single-sided PCB manufacturer

Let’s get started!

What is a single-sided PCB?

As the name suggests, a single-sided PCB has a single conductive copper layer on one side of the insulating substrate material. The other side of the PCB is primarily used to mount and solder components.

The main parts of a single-sided PCB include:

Substrate – forms the base of the PCB. Usually made of materials like FR-4, polyimide, etc.
Copper layer – The single conductive layer that creates the circuit wiring traces.
Solder mask – An epoxy-based layer that protects the copper traces.
Silkscreen – Indicates component placement, polarity, component values, etc.
Plated through holes – For component leads to pass through and connect both sides.

As there is only one conductive layer, single-sided PCBs are best suited for simple, low-density circuits like basic electronics, toys, simple medical devices, etc. For more complex designs, double-sided or multilayer PCBs are preferred.

Single-Sided PCB Design

Designing the layout of a single-sided PCB involves several key steps:

Schematic Capture

The first and foundational step is developing the circuit schematic diagram.
The schematic will contain symbols representing all the electronic components.
Interconnections between components are shown using wires.
The schematic will be the basis for translating the logical circuit into the physical PCB layout.

Component Library Creation

Before the PCB layout can begin, the component library needs to be built.
This involves making schematic symbols and 3D footprint models for each component.
Accurate footprints matching the datasheet recommendations are crucial for error-free PCB design.

PCB Layout Routing

With the schematic and component libraries ready, the layout of the PCB can proceed.
Components are virtually placed on the single-sided board following the schematic netlist.
Interconnections between component pads are routed on the top layer based on the schematic.
Autoroutes can be used for initial trace routing, which is then optimized manually.
Care is taken to route traces at proper angles and minimize length for optimum performance.

Copper Pour

Copper pours are added to fill large empty areas on the routing layer.
This acts as a pseudo-ground plane, providing shielding and improved signal return paths.
Thermal relief connections are given between the copper pour and component pads.
Copper balances are maintained to avoid bowing of the PCB due to thermal stresses.

Design Rule Checking

Completed layouts are verified against design rules like trace width, clearance, and annular rings.
Electrical rules like maximum etch length matched line lengths are checked.
Errors like shorts, open circuits, and violations are identified and fixed at this stage before manufacturing.

Documentation

Finally, fabrication and assembly drawings like assembly drawings, BOM, layer plots, and drill charts are generated.
PCB manufacturers require this documentation for prototyping or production.

Single-sided PCB Stack-up

The stack-up of a single-sided PCB involves the following:

Substrate – Forms the core. FR-4 glass epoxy is commonly used.
Copper Layer – A single layer of copper foil laminated to the substrate.
Solder Mask – Epoxy layer over the copper layer preventing solder bridges.
Silkscreen – Provides markings for assembly and components.

The simplicity of the single-sided PCB stackup makes it easy to manufacture.

Benefits of Single-Sided PCBs

Single-sided PCBs offer several advantages:

Low Cost – Single-sided PCBs are inexpensive due to their simple design. This makes them economical for high-volume production.
Faster Manufacturing – Single-sided PCB fabrication is quicker and easier with only one conductive layer. This enables faster prototype iterations.
Simple Layout – The layout of a single-sided board is straightforward with no complex routing, enabling faster design.
Easy Assembly – With all components on one side, single-sided PCB assembly is easier manually or using automation.
Flexible and Durable – The FR-4 substrate provides enough flexibility for the PCB to be bent to a certain degree without damage.
Easier Troubleshooting – Fault finding is more straightforward with a single copper layer.

For simple, cost-sensitive designs, single-sided PCBs offer the optimal solution.

Limitations of Single-Sided PCB

However, single-sided PCBs also come with some limitations:

Larger Size – With the circuit traces confined to one layer, the PCB area increases, causing larger board sizes.
Lower Component Density – Only one side is available for component placement, reducing component density.
Limited Routing – There is no crossing over of traces, so routing capabilities are constrained.
More Susceptible to Noise – Lack of a proper ground plane or power plane makes the board more susceptible to noise.
Not Suitable for Complex Circuits – Single-sided PCBs are not feasible for complex, dense circuit designs.

So, for anything other than simple, low-density circuits, double-sided or multilayer PCBs become essential.

Single-Sided PCB Manufacturing Process

Single-sided PCB fabrication involves relatively simple steps:

Board Preparation

The substrate is cut to the required PCB dimensions, and holes are drilled per the layout.

Conductive Layer Patterning

A photoresist coating is applied on the copper-clad substrate. The circuit layout is then transferred to the PCB using photographic techniques. The exposed copper is etched away, leaving behind the desired conductive pattern.

Solder Mask Application

A solder mask coating is applied over the copper layer, exposing only the soldering pads and contacts.

Silkscreen Printing

Graphics and markings are screen-printed on the solder mask layer to indicate polarity, placement, text, etc.

Surface Finish

A chemical coating like HASL, immersion silver, ENIG, etc., is applied to protect the exposed copper from oxidation.

Electrical Testing

The fabricated PCBs undergo electrical testing before delivery to ensure correctly functioning boards.

Single-Sided PCB Materials

The common materials used in single-sided PCB fabrication include:

Substrate – FR-4, CEM-1, Polyimide, PTFE, etc.
Conductive Layer – Copper foil is usually 1 oz (35 μm) or 2 oz (70 μm) thicker.
Solder Mask – LPI (liquid photo imageable) or Dry Film.
Silkscreen Ink – Epoxy or UV ink-based.

FR-4 glass epoxy is the most popular and cost-effective substrate option. The material choices determine the PCB’s electrical and mechanical characteristics.

Single-Sided PCBs Cost

Several factors determine the cost of single-sided PCBs:

Board Size – Larger boards require more materials, increasing cost.
Board Thickness – Thicker boards with thicker copper foils cost more.
Quantity – Unit cost reduces with larger order quantities due to economies of scale.
Lead Time – Faster fabrication with lower lead times increases cost.
Base Material – FR-4 is the cheapest option. Other exotic materials cost more.
Copper Weight – Heavier copper foils are more expensive.
Special Finishes – ENIG, immersion silver, etc., cost more than basic HASL.
Certifications – UL, IPC, ISO, etc. certified PCBs are more expensive.
Location – Costs vary based on the geographic location.

Single-sided PCB Thickness

The thickness of a single-sided PCB depends on the following:

Copper Thickness – 1 oz or 2 oz copper foils are commonly used.
Number of Layers – Only one conductive layer is present.
Substrate Thickness – Based on application – 0.4mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.6mm, 2 mm+.
Component Heights – Thicker PCBs allow taller components.

Standard single-sided PCBs thickness with 1 oz copper and FR-4 substrate is 1.6 mm. This provides adequate stiffness while allowing flexibility for most applications. Maximum PCB thickness can reach over 2mm.

Comparing Single-Sided Vs. Double-Sided PCBs

Let’s compare single-sided PCBs to double-sided PCBs:

Parameter	Single Sided PCB	Double Sided PCB
Number of Copper Layers	One	Two (top and bottom)
Component Placement	One side only	Both sides
Interconnection	No overlapping traces	Traces can crossover
Routing Complexity	Simple routing	Improved profitability
Circuit Density	Low-density circuits	High-density circuits possible
Board Size	Larger size	More compact
Cost	Lower cost	Higher cost than single-sided
Manufacturing Time	Faster	Slower due to increased complexity
Applications	Simple electronics	Ideal for complex circuits

Double-sided PCBs offer greater design flexibility along with enhanced circuit density, albeit at increased cost.

Single-Sided PCB Applications

Some typical applications of single-sided PCBs include:

Basic electronic circuits
Simple medical devices
Toys
Remote controls
LED lighting
Power supplies
Radios
Battery chargers
Printers
Basic IoT products
Vending machines

Any product requiring a simple, low-cost PCB can benefit from a single-sided board. For more complexity, double-sided or multilayer boards are preferred.

Design Tips for Single-Sided PCBs

Here are some helpful guidelines to follow when designing single-sided PCBs:

Minimize the number of jumper wires and zero ohm resistors to reduce assembly errors.
Place bypass capacitors close to IC power pins for improved power integrity.
Ensure ground fills do not rely on just a few vias for connections. Use thermal reliefs and polygons.
Include generous clearances between high-voltage and low-voltage circuits.
Allow sufficient creepage distances between primary circuits and other traces.
Place test points, indicators, and potentiometers conveniently for troubleshooting.
Maintain the same trace widths in bus lines for consistent impedance.
Include a ground plane as far as possible for EMI reduction.

Good layout practices result in robust and noise-immune single-sided PCB designs.

Comparing Single-Sided PCBs vs. Multilayer PCBs

Single-sided PCBs and multilayer PCBs have significant differences when it comes to design, performance, and applications:

Component Density

Single-sided PCBs allow component placement only on one side, restricting density.
Multilayer PCBs enable components to be placed on multiple layers vertically, increasing density.
Complex circuits with hundreds of components can be realized with multilayer PCBs.

Routing Capability

On single-sided PCBs, routing is limited as traces cannot cross over.
Multilayer PCBs provide multiple routing layers, allowing traces to cross over freely.
Even the most complex routing requirements can be met with adequate layers.

Signal Integrity

Single-sided PCBs cannot correctly isolate or shield signals from noise.
Multilayer PCBs allow a complete reference plane system for shielding and isolation.
This enables multilayer PCBs to maintain signal integrity at high speeds.

Miniaturization

Single-sided PCBs require larger areas as components sit side by side.
By going vertical, multilayer PCBs conserve lateral space, enabling miniaturization.
Phone and tablet PCBs demonstrate the small footprint achievable.

EMI/EMC

Single-sided PCBs provide minimal control over radiated noise emissions.
Multilayer PCBs incorporate continuous ground/power planes to contain EMI/EMC.
This allows multilayer boards to meet stringent emissions requirements.

High-Speed Signals

High-frequency signals incur more loss in single-sided PCBs without proper return paths.
Multilayer PCBs with uninterrupted reference planes have a lower loss for high-speed signals.
This enables multi-Gbps signaling in cards, backplanes, routers, etc.

Cost

Single-sided PCB fabrication has lower costs due to more straightforward construction.
Multilayer PCBs require advanced materials and processes, increasing costs.
However, the benefits of multilayer PCBs generally outweigh their higher costs.

Multilayer PCB technology enables highly complex, high-performance, miniaturized circuit designs despite increased costs.

Conclusion

Single-sided PCBs offer a cost-effective solution for essential electronic products requiring a simple circuit layout. While their design and fabrication process is straightforward, following good layout practices results in robust boards. Double-sided or multilayer PCBs become essential for more complex, dense designs. Finding a PCB vendor with expertise and quality certifications helps obtain reliable single-sided boards tailored to your application needs.

Frequently Asked Questions (FAQs)

What are the layers in a single-sided PCBs?

A single-sided PCB contains a substrate layer, a single copper layer, a solder mask layer, and a silkscreen layer. The components are mounted on one side and the circuit on the other.

Why are single-sided PCBs used?

Single-sided PCBs are commonly used due to their simple design, low-cost fabrication, faster manufacturing time, and suitability for low-density circuits.

What is the difference between single-sided and double-sided PCB?

Single-sided PCBs have the circuit and components on one side, while double-sided PCBs have conductive layers on both sides, allowing higher component density and complex routing.

What are the advantages of single-sided PCB?

Benefits include low cost, faster fabrication, simple layout, easy assembly, flexibility, and more straightforward troubleshooting.

What are the limitations of a single-sided PCB?

Limitations include larger board sizes, lower component density, constrained routing, more noise susceptibility, and unsuitability for complex circuits.

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