Have you ever wondered how your powerful smartphone, lightweight tablet, or office router works normally? How are their “brain” and “nerve center”carried perfectly？
The answer is all on the printed circuit board, commonly referred to as a PCB. However, double-sided PCBs play a crucial, if not always dominant, supporting role. Today, let’s explore this microscopic world and discover the extraordinary charm of double-sided PCBs.

I. What is a Double-Sided PCB? A Simple Metaphor to Make You Understand

-. Single-Sided PCB: It is like a country road with only one lane. All vehicles (current signals) can only go from point A to point B and cannot cross each other. The line design is extremely restrictive.

-. Double-Sided PCB: Update to two lanes. The top layer and bottom layer of the PCB can carry copper foil circuit, just like two separate lanes. While plated through-hole, PTH, it serves as  an “overpass” connecting the upper and lower layers, allowing signals to move freely between them.

This structural leap has given circuit design unprecedented flexibility and complexity. It is no longer a simple connection, but a three-dimensional transportation network.

II. Why Choose Double-Sided PCB? Four Core Advantages Convince Engineers

When a single-sided PCB can not meet the requirement, and a 4-layer PCB costs too much, a double-sided PCB takes the lead role with its extraordinary cost-effectiveness.

Cost-Effectiveness
This is the most fatal attraction of double-sided PCBs. With the mature manufacturing technology and low-price material, double-sided PCBs are very suitable for consumer electronics, middle and small quantity production projects, and prototype verification of startups. Under the condition of ensuring the functions, how to use well every penny, is the first consideration of product managers and engineers.

Design Flexibility
With an additional layer for routing, engineers no longer have to worry about routing. Two-layer routing effectively solves the common crossover issues of single-sided boards, greatly simplifying design and improving routing success. Double-sided boards are an ideal choice for circuits containing microcontrollers (MCUs) and common interface chips (such as USB and Ethernet).

Moderate Complexity & Density
Double-sided PCB can carry twice as many components as a single-sided PCB(using SMT technology and the components can be placed on the two sides) to realize more complex functions, at the same time, avoid the expensive manufacturing cost and longer lead time of multilayer PCB. A double-sided PCB is a perfect stepping stone from a simple circuit to a complex system.

Proven Reliability
Since its birth, the manufacturing process of double-sided PCB has been refined over decades, resulting in an extremely mature and stable technology. From drilling, copper plating, and electroplating to graphic etching, every process has strict quality control standards to ensure the consistency of the final product and long-term reliability.

III. Double-Sided PCB Manufacturing Process: The Combination of Technology and Precise Art

The manufacturing of double-sided PCB is a precise micro sculpture art;

Cutting: cutting the big-sized copper clad lamination to the manufacturing size.

Drilling: using high-precision drilling machines for the component holes and vital through holes.

PTH & Plating: This is the key! Through chemical deposition and electroplating, a layer of copper is deposited inside the non-metallic hole wall, connecting the upper and lower layers of circuits.

Pattern Transfer: The designed circuit pattern is transferred to the copper-clad board through the photolithography process.

Etching: Chemicals are used to remove unnecessary copper foil, leaving the designed circuitry.

Solder Mask & Silkscreen: Green solder mask ink is applied to prevent soldering shorts, and component identification and logos are printed.

Surface Finish: Surface treatments such as HASL, ENIG, and immersion silver are applied as needed to protect the pads and ensure good solderability.

Testing & Inspection: Electrical performance testing is performed using flying probe testing or fixtures to ensure 100% connectivity on every board.

IV. Double-Sided Wide Applications

Double-sided PCBs can be used almost everywhere.

Industrial Control: PLC controller, sensor module, power supply monitor device.

Automotive Electronics: Vehicle central control, instrument panel, LED light controller.

Consumer Electronics: Toy, smart home devices(smart switch, socket), small home appliances, mouse, and keyboard.

Communications equipment: routers, switches, modems.

Medical equipment: handheld monitors, electronic thermometers, and other devices that have requirements for size and cost.

V. About Quotation: Offer a Transparent and Professional Quotation as Reference

Have we ever met such a question: “How much does it cost to make this double-sided PCB?” That is a good question, but the answer is not a fixed number. The price for PCB is just like custom suits, it will depend on the detailed “dimension” and “fabric”, the main factors include;

Panel size: The larger the size, the higher the unit price, but one needs to consider the panel utilization comprehensively.

Material: Standard FR-4, high tg materials, halogen-free materials, and high-frequency materials have a big price range.

Layer count: As the layer count goes up, the manufacturing cost will be higher as well

Thickness: Normally, the thickness is 1.6mm, and the price is different for different thicknesses

Copper weight: Like 1oz(35um), 2oz(70um). The thicker the copper, the higher the cost; the thinner the copper, the higher the cost as well.

Min. Trace & space: The finer the requirement (such as 4/4mil), the more difficult the process is and the higher the price. In Jerico, the min. trace and space we can do is 2mil/2mil.

Surface finish: HASL is a cost-effective choice, while ENIG is more expensive with better flatness, which is suitable for precise chips.

Special process: Like golden fingers, optional ENIG and countersink holes will increase additional costs.

Quantity: With a bigger quantity, the unit price will be lower

VI. Double-Sided PCB vs. Multilayer PCB-How to Make the Right Choice?

This is a very classic engineering balance question. Choose a double-sided PCB or a multilayer PCB?

Choose a double-sided PCB:

-. The cost should be the first considered factor.

-. The logic of the circuit should be relatively easy.

-. The circuit density is not high.

-. Signal frequency is low(normally below 50-100MHz), with no strict impedance control or EMI/EMC requirement.

-. The board space should be enough, allowing a bigger size design.

Updating to multilayer PCB;

-. The circuit is very complex, and a double-sided PCB can not realize the circuit design.

-. Need to proceed with high-speed digital signal(like DDR storage, high-speed SerDes interface), must proceed with strict impedance control and signal integrity management.

-. There are severe electromagnetic interference (EMI) or electromagnetic compatibility (EMC) requirements, requiring dedicated ground planes and power planes to provide shielding.

-. The product size requires it to be extremely compact, and the wiring density must be increased by increasing the number of layers.

Core principle: Do not use a double-sided PCB to challenge high-speed or high-interference design, or the later debugging cost and pain will be more than the initial cost of a multilayer PCB.

How do you decide whether the project to go with a double-sided PCB or a multilayer PCB? On what kind of occasions double-sided PCB be the first option for you? Let’s talk about PCB today!