Introduction About Single Sided and Double Sided SMT Assembly

Introduction About Single-Sided and Double-Sided SMT Assembly

Single-sided and double-sided SMT assemblies differ in terms of component density. Single-sided SMT assembly has a higher density than double-sided SMT assembly and requires a higher amount of heat to process. Most assemblers process the higher-density side first. This minimizes the risk of components falling out during the heating process. Both sides of the reflow assembly process require the addition of SMT adhesive to hold the components in place during the heating operation.


Single-sided PCBs are the most common. In a single-sided board, all the components are located on one side of the board, and assembly is only needed on that side. Double-sided boards have traces on both sides of the board, which reduces their footprint. Double-sided boards also offer better heat dissipation. The manufacturing process for double-sided boards is different than for single-sided PCBs. During the double-sided process, copper is removed from the double-sided board and then reinserted after an etching process.

Single-sided PCBs are also easier to manufacture and less expensive. Manufacturing a single-sided PCB includes several stages, including cutting, drilling holes, circuit treatment, solder resist, and text printing. Single-sided PCBs also undergo electrical measurements, surface treatment, and AOI.

PI copper-clad board

The PI copper-clad board single-sided and double-sided smt assembly process involves the use of a polyimide cover film to laminate copper on one side of the PCB. The copper-clad board is then pressed into position by an adhesive glue that opens at a specific position. Afterwards, the copper-clad board is patterned with anti-welding resistance and the part guide hole is punched.

A single-sided flexible PCB is composed of a PI copper-clad board with one conductor layer, usually rolled copper foil. This flexible circuit is covered with a protective film after the circuit is completed. A single-sided flexible PCB can be manufactured with or without a cover layer, which acts as a protective barrier to protect the circuit. Single-sided PCBs have only one layer of conductors, which is why they are often used in portable products.


FR4 is a grade of epoxy resin that is commonly used in PCB fabrication. This material offers excellent heat and flame resistance. The FR4 material has a high glass transition temperature, which is crucial for high-speed applications. Its mechanical properties include tensile and shear strength. Dimensional stability is tested to ensure the material does not change shape or lose its strength in various working environments.

FR4 single-sided and double-stacked multi-layer boards consist of an FR4 insulating core and a thin copper coating on the bottom. During manufacturing, through-hole components mounted on the component side of the substrate with leads running through to copper tracks or pads on the bottom side. In contrast, surface-mounted components mount directly on the solder side. While they are very similar in structure and construction, the primary difference is in the placement of the conductors.


Surface Mount Technology (SMT) assembly is an efficient way to attach electronic components to printed circuit boards without the need for holes. This type of technology is suitable for both leaded and non-leaded components. With the double-sided SMT technique, the printed circuit board (PCB) has two conductive layers – one on the top and one on the bottom. The copper covering on both sides of the board acts as a current-carrying material and helps in the attachment of components to the PCB.

For single-sided boards, it is easy to use simple support pillars. For double-sided boards, additional support is required. The free area around the board should be at least 10 mm.


The process of FR8 single-sided and double smt assembly is similar to the general assembly process with a few differences. Both processes use adhesive and solder paste. They are followed by cleaning, inspection, and testing. The finished product must meet the specifications specified by the designer.

Single-sided boards are more common and have a smaller footprint. However, double-sided boards reduce space requirements and maximize heat dissipation. During the etching process, copper is removed from the double-sided side. It is reinserted after the process.

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