Single-Sided PCB Manufacturing: A Complete Guide
What a Single-Sided Board Is
A single-sided board carries copper on one face of a rigid laminate and none on the other. Components are mounted on the copper side and their leads pass through drilled holes to be soldered on the same side, which means the second face of the board is used only for the legend and, sometimes, for a small amount of jumper wire.
There is no plated through hole in the classic construction, so the two faces are not electrically connected at all and there is nothing to plate. That single fact is what makes the board cheap: the process is shorter, the material is thinner, the drilling is a single pass with no plating, and the yield is high because there is less that can go wrong.
Where It Still Makes Sense
- High volume consumer products. Remote controls, calculators, toys, power adapters and simple LED products, where the circuit is small and the price of the board matters more than anything else.
- Simple power and interface circuits. A relay board, a connector panel or a power distribution board with few components.
- Disposable and cost-driven devices. Where the product is replaced rather than repaired and the board is a few cents of the total cost.
- LED strips and simple lighting. Long narrow boards where the circuit is a repeated pattern and a second layer would add nothing.
- Membrane and switch panels. Where the board is a set of contacts and the routing is trivially simple.
The board is not suitable where the circuit needs a ground plane, where the routing crosses itself, where components are mounted on both faces, or where the product needs controlled impedance. Those are the cases that justify the second layer.
Materials
The substrate is chosen for cost. Composite laminates such as CEM-1 and CEM-3 are common, because the board is punched rather than routed in high volume and the paper or non-woven glass core is cheaper than woven glass. FR-4 is used where the board needs better mechanical or thermal properties or where the thickness tolerance matters.
Where the product is extremely cost sensitive, a phenolic paper board is used, at the price of a lower temperature rating and higher moisture absorption. Where the board has to pass a flammability requirement, a flame retardant grade is specified, which is what the FR in FR-4 refers to.
Copper weight is usually one ounce, or two where the board carries a moderate current. Heavier copper on a single-sided board is unusual because a board with a heavy current path usually has other reasons to be built on a better substrate. Our notes on PCB manufacturing describe the material families in more detail.
The Manufacturing Process
- Laminate preparation. The copper clad sheet is cut to panel size, cleaned and, where a punched outline is used, the tooling is set.
- Pattern printing. A resist is applied, exposed through the artwork and developed, leaving the resist over the copper that will become the circuit.
- Etching. The exposed copper is dissolved away, leaving the traces and pads under the resist.
- Resist stripping. The resist is removed and the copper pattern is exposed.
- Drilling. Component and mounting holes are drilled or punched. There is no plating step, so the hole wall is bare laminate.
- Solder mask. Printed and cured over the copper, with openings at the pads.
- Legend. The reference designators and any marking are printed over the mask.
- Surface finish. Hot air levelling, an organic solderability preservative or immersion tin protects the copper and makes it solderable.
- Test and inspection. An electrical test confirms there are no opens or shorts, and a visual inspection catches the pattern defects.
The process has one well known limitation: because the holes are not plated, the solder has to form the connection between the top and the bottom of the joint by flowing through the hole. That works well on a hand or wave soldered board, and it is why the holes on a single-sided board are usually a little larger and the pads a little more generous than on a plated board.
Design Rules
Solve the crossings. With one routing layer, every crossing has to be eliminated by re-routing, by a zero ohm resistor or a wire link, or by moving a component. This is the constraint that decides whether a design can be single sided at all, and it is usually assessed early in the layout.
Use a generous pad and hole. The joint relies on solder flowing through the hole, so the pad and the hole are sized for that rather than for a plated barrel. Keep the annular ring adequate for the hole tolerance.
Plan for the finish. A board that is wave soldered once can use an organic coating. A board that is handled or stored for a long time, or soldered more than once, is better with a metallic finish.
Consider a copper pour. A large ground area on the copper side improves the electrical behaviour of a simple circuit at no cost, provided the layout leaves room for it and the pour does not create an unwanted coupling path. Our notes on PCB design and layout cover the layout techniques.
Design the panel. Single-sided boards are usually produced in large panels with a punched or routed outline, and the panel is designed with the tooling and the border the process needs.
Single Sided Against Two Layers
The cost difference is real and it is not as large as people assume. A two layer board adds a second copper layer, a lamination and, most importantly, a plating line, which is the expensive part of the process. In modest quantities the difference is often only a few tens of percent, and the second layer buys a ground plane, a second routing layer and plated holes.
The decision rule is therefore not the board price but the circuit. If the circuit routes comfortably in one layer, if there is no need for a ground plane and if the volume is large, the single-sided board is the right choice. If any of those conditions fails, the two layer board is usually cheaper in the end, because the layout time, the wire links and the rework cost more than the difference in the board price; our notes on PCB assembly describe the assembly consequences of each.
What It Costs
A simple single-sided board in high volume costs cents rather than dollars. In moderate quantity, a small board of roughly 100 by 100 millimetres is typically around 0.80 to 1.50 US dollars, falling substantially above a thousand pieces and falling further when the design can be punched rather than routed.
The price is driven by the panel utilisation, the number of holes, the finish and, above all, the quantity and the tooling arrangement. Our notes on quality management describe the process controls that keep the yield high on a product where the margin is measured in cents.
FAQ
Can a single-sided board have plated holes? Not in the classic construction, because there is no second copper layer to connect to. Where plated holes are needed, the board is built as a double-sided board.
Why are the holes larger on a single-sided board? Because the solder has to flow through the hole to form the joint, which requires a larger opening than a plated barrel.
Is a single-sided board less reliable? Not inherently. It has fewer process steps and therefore fewer opportunities for a defect, but it cannot provide a ground plane, and the solder-through joint is less forgiving than a plated one on a dense board.
Where is it used most? In high volume consumer products with simple circuits, and in the power and interface boards of larger products.
Conclusion
Single-sided PCB manufacturing is the shortest path from artwork to finished board: print, etch, drill, mask, finish and test, with no plating and no lamination. It is the cheapest construction available and it is limited to circuits that route in one layer and need no ground plane or controlled impedance. Use it where the volume is high and the circuit is simple, and move to two layers as soon as a ground reference or a second routing layer is required.
