What is Single Sided PCB?

How Single-Sided PCBs are Manufactured

The process for manufacturing single-sided PCBs involves several key steps:

Substrate Selection – An insulating substrate material, usually a rigid laminate such as FR-4 fiberglass, is selected based on the desired properties (cost, durability, dielectric constant, etc.). The substrate is cut to the required board dimensions.
Copper Cladding – One side of the substrate is laminated with a thin layer of copper foil, typically 1-2 oz in weight (thickness). The copper provides the conductive layer for creating circuit traces.
Applying Resist – A photoresist layer, which is sensitive to ultraviolet (UV) light, is applied on top of the copper. This is done through a process called “dry film lamination” or “screen printing”.
Exposure and Developing – The PCB pattern is transferred from a photomask or film onto the photoresist layer by exposing it to UV light. The exposed areas of the resist undergo a chemical change. In the developing step, the exposed areas are dissolved away by a chemical solution, leaving the unexposed resist to protect the copper underneath.
Etching – The unprotected copper areas are chemically etched away using an acidic solution, usually ferric chloride or ammonium persulfate. This leaves only the desired copper traces and pads as defined by the resist pattern.
Resist Removal – After etching, the remaining photoresist is stripped off using a chemical stripper or by mechanical abrasion, exposing the final copper pattern.
Drilling – Holes are drilled through the board to accommodate through-hole component leads and provide interconnections to the other side if required. Miniature drill bits or a CNC drill machine is used for this.
Surface Finish – To protect the exposed copper from oxidation and enhance solderability, a surface finish like HASL (hot air solder leveling), ENIG (electroless nickel immersion gold), or OSP (organic solderability preservative) is applied. A silkscreen layer may also be added to print component labels and markings.
Cutting and Profiling – If multiple small PCBs were patterned on a larger panel for production efficiency, they are routed out and separated using a saw or router. The individual board edges may be milled or beveled if required.
Quality Check – The finished PCBs undergo a visual inspection and electrical testing to ensure they meet the design specifications and are free of manufacturing defects before being packaged and shipped.

Request PCB Copy & IC Crack Quote Now

Advantages of Single-Sided PCBs

Single-sided PCBs offer several advantages, making them a popular choice for many electronic applications:

Cost-Effective

Single-sided boards are the least expensive type of PCB to manufacture. They require fewer raw materials, less processing steps, and simpler equipment than double-sided or multilayer boards. This makes them an economical solution for high-volume, low-cost products.

Quick Turnaround

With a streamlined fabrication process, single-sided PCBs can be manufactured relatively quickly. Fewer steps involved means less time from design to finished product. This is advantageous when rapid prototyping or tight production deadlines are involved.

Easy to Design

Designing a single-sided PCB layout is simpler and more straightforward compared to double-sided or multilayer boards. There is no need to worry about interlayer connections, via placement, or drilling registration. PCB design software tools are also easier to use and less expensive for single-sided boards.

Simplified Assembly

Assembling components on a single-sided board is generally easier and faster. All the parts are placed and soldered on the same side, making it suitable for manual assembly or simpler pick-and-place machines. Single-sided designs often use through-hole components which are sturdier and easier to work with than surface-mount devices.

Easier Troubleshooting and Repair

With all components and traces exposed on one side, single-sided PCBs are easier to inspect, debug and repair. Visual tracing of signal paths and probing of test points is more convenient. Replacing a faulty component is also straightforward with access to all the solder joints.

Limitations of Single-Sided PCBs

Despite their benefits, single-sided PCBs also come with some limitations:

Limited Routing Space

With only one conductive layer available, the routing space on a single-sided board is restricted. This limits the component density and circuit complexity that can be accommodated. Traces may need to take longer, meandering paths to avoid overlaps, increasing the overall board size.

No Shielding or Grounding Plane

Single-sided boards lack a dedicated ground plane or shielding layer, which can be problematic for circuits sensitive to electromagnetic interference (EMI) or radio frequency interference (RFI). Noisy signals can easily couple to adjacent traces causing crosstalk and degrading signal integrity.

Limited Power Handling

The current carrying capacity of traces on a single-sided board is limited by the copper thickness and width. For power-hungry circuits or high-current applications, the trace size required may be impractically large, or the power dissipation may cause excessive heating without proper heat sinking.

Higher Impedance and Larger Parasitics

The lack of a ground plane means that signal return paths are longer and less well-defined on single-sided boards. This leads to higher trace impedance and larger parasitic inductance and capacitance. High-speed signals and sensitive analog circuits can be adversely affected by these parasitics.

Not Suitable for High Density Designs

Single-sided construction is not suitable for circuits with high component density or ball grid array (BGA) packaging. The restricted routing space makes it difficult to fan out a large number of traces from a fine-pitch component. Boards with dense surface-mount devices typically require double-sided or multilayer construction.

Applications of Single-Sided PCBs

Despite their limitations, single-sided PCBs find use in a wide range of electronic applications, particularly those that prioritize cost savings over performance or miniaturization. Some common applications include:

Consumer Electronics

Remote controls
Toys and games
Calculators
Clocks and timers
Simple appliances

Industrial and Automotive

Sensors and detectors
Relays and switches
Lighting controls
Power supplies
Instrumentation displays

Hobbyist and Educational

Arduino Shields
Breadboard adapters
Prototyping boards
Student project kits
DIY electronics

Telecommunications

Telephone line filters
ADSL splitters
Cable and connector adapters
Junction boxes
Legacy equipment

Alternatives to Single-Sided PCBs

When the limitations of single-sided construction are too restrictive for a given application, designers can consider alternative PCB technologies:

Double-Sided PCBs

These have conductive layers on both sides of the substrate, effectively doubling the available routing space. Through-hole vias are used to interconnect the top and bottom layers. Double-sided boards can accommodate higher component density and more complex circuitry than single-sided boards.

Multilayer PCBs

Multilayer boards consist of three or more conductive layers laminated together with insulating layers in between. The internal layers are used for power and ground planes, while the outer layers are used for signal routing. Multilayer construction offers the highest density and performance, but at a higher cost and manufacturing complexity.

Flexible PCBs

Flexible PCBs are made with a thin, flexible polymer substrate such as polyimide instead of rigid FR-4. They can be single-sided, double-sided, or multilayer. Flex PCBs can conform to curved surfaces and withstand repeated bending, making them ideal for applications with limited space or movable parts.

Rigid-Flex PCBs

Rigid-flex boards combine rigid and flexible substrates into a single assembly. They consist of rigid PCB sections connected by flexible ribbon-like segments. This allows for 3D packaging and eliminates the need for connectors between boards. Rigid-flex designs are commonly used in aerospace, medical, and consumer electronics.

Single-Sided PCB Design Considerations

When designing a single-sided PCB, there are several key factors to consider for optimal performance and manufacturability:

Component Placement

Components should be placed in a logical sequence according to the signal flow, with minimal crossovers and jumpers. Placing components on a grid with standardized pitch helps with automated assembly. Adequate spacing should be provided around components for soldering and heat dissipation.

Trace Routing

Traces should be routed as directly as possible, minimizing lengths and avoiding sharp angles. Wider traces should be used for power and high-current signals. Proper trace spacing is important to minimize crosstalk, especially for high-speed signals. Ground traces should be used to provide a low-impedance return path.

Jumper Wires

When trace crossovers are unavoidable, jumper wires can be used to bridge the connections. However, jumpers add to the assembly cost and can be a reliability concern. They should be kept to a minimum and placed in accessible locations for easier rework if needed.

Copper Pour

Unused areas of the PCB can be filled with a copper pour connected to ground. This helps to reduce EMI, improve heat dissipation, and provide a more robust ground connection. However, copper pour can increase the etching time and the amount of etchant required during manufacturing.

Solder Mask and Silkscreen

A solder mask layer helps to protect the copper traces from oxidation and prevents solder bridges during assembly. An indexing hole mount can be added for assisting automated assembly robots. The silkscreen layer should clearly label all the components, test points, and connectors for easier assembly and debugging.

Panelization

For efficient mass production, multiple copies of a PCB design are usually arranged in a larger panel. Breakaway tabs or Mouse Bites are added between the individual boards to hold them together during manufacturing. The panelization scheme should consider the available fab equipment and assembly processes.

FAQ

1. What is the typical thickness of a single-sided PCB?

A standard single-sided PCB is usually 1.6 mm thick, but thinner or thicker substrates are available for special applications. The copper layer is typically 1 oz or 35 microns thick.

2. Can single-sided PCBs be used for high-frequency circuits?

Single-sided construction is generally not recommended for high-frequency circuits above a few hundred MHz due to the lack of a ground plane and higher parasitic impedances. Double-sided or multilayer boards with controlled impedance traces are preferred for RF and microwave applications.

3. Are single-sided PCBs suitable for automated assembly?

Yes, single-sided boards can be assembled using automated pick-and-place machines and wave soldering or reflow ovens. However, the component placement and orientation must be carefully designed to ensure compatibility with the assembly equipment.

4. How small can the traces and spaces be on a single-sided PCB?

The minimum trace width and spacing depend on the PCB manufacturer’s capabilities and the desired copper thickness. Typical values are 0.2 mm (8 mil) for traces and 0.4 mm (16 mil) for spaces, but finer features are possible with specialized fabrication processes.

5. Can single-sided PCBs be used for surface-mount components?

Yes, surface-mount devices (SMDs) can be used on single-sided boards, but the component density and pin count may be limited by the available routing space. Fine-pitch SMDs and BGAs are usually not practical on single-sided boards due to the difficulty of fanning out the traces.