Single-sided PCBs, also known as print-and-etch boards, are boards with traces on only one side. The etch resist is typically applied using screen printing techniques, and the conductor pattern is formed by chemically etching away the unwanted copper foil that is exposed. These are traditional single-sided PCBs, common used materials are FR-1, CEM-1, CEM-3, and FR-4. Of course there are some other types of boards also single-sided, like the flexible circuits and metal core PCBs, a lot of them also in single-sided, the processes are different and much more complex.
Typical substrates used for Single-Sided Circuit Boards are XPC, FR-1, FR-2, FR-4, CEM-1, CEM-3.
XPC, FR-1, FR-2 are flame-retardant phenolic materials that are also highly punchable, they have excellent electrical, heat-resistant, moisture-resistant, flame-resistant and other properties as well as low cost. FR-3 is epoxy Copper Clad Laminate, it is flame retardant with high electrical properties.
CEM-1, which is a composite of paper and glass impregnated with epoxy resin, is the most popular substrate for SSBs. While not as low cost as XPC-FR or FR-2, CEM-1 has gained popularity because of its mechanical strength and also because of the relative unavailability of paper phenolic laminates.
CEM-3 is similar to FR4, but uses a composite material of a non-woven glass core and a woven glass surface instead of a full sheet of woven glass. It’s a flame retardant epoxy resin, copper-clad glass material, commonly used in double-sided PCBs.
“FR” is the abbreviation of flame retardant. As the board runs on electricity, it should be heat resistant. FR4 has much better heat resistance than FR1 and XPC due to the different composition of the layers.
| No. | Material | Composition | Max Temp (°C) | Characteristics | Common Applications |
|---|---|---|---|---|---|
| 1 | FR-1 | Paper phenolic | 120 | Basic strength, moderate dielectric strength | Low-power consumer devices |
| 2 | FR-2 | Phenolic resin | 130 | Better moisture resistance, improved properties | Household appliances |
| 3 | XPC | Epoxy laminate | 130 | Good chemical/mildew resistance | Connectors, switches |
| 4 | CEM-1 | Epoxy composite | 130 | Good insulation, lightweight | Single-sided PCBs |
| 5 | CEM-3 | Fiberglass/epoxy | 140 | High strength, good thermal properties | Double-sided/multilayer PCBs |
| 6 | FR-4 | Glass epoxy | 130-180 | Excellent insulation, high strength, low moisture | Most common PCB applications |
When designing a single-sided PCB, holes are necessary for component leads and mounting purposes. The methods used for creating SSB holes are primarily drilling and punching, each having specific techniques, advantages, and applications.
CEM-1 and CEM-3 are composite materials that provide good dielectric properties, making them suitable for various applications, while FR-4 is a widely used epoxy resin that offers excellent mechanical strength and thermal stability. These material requires careful handling during the drilling process to ensure high-quality production and efficient assembly, as precision in hole size and placement directly affects the performance and reliability of the PCB.
Single-sided PCB are mostly used in high-volume, low cost consumer electronics which uses XPC, FR-1, FR-2 materials, these punchable materials can enhance production efficiency and significantly saving the overall costs.
These functions make solder masks an essential component in PCB fabrication, ensuring the boards are robust, reliable, and compliant with industry standards.
Soldermask, or solder resist, is a heat-resistant coating material applied to selected areas to prevent the deposition of solder upon those areas during subsequent soldering.” With the evolution of PCB technology, solder mask coatings are now asked to provide much more functionality than simply a soldering aid.
Selective Coating, Acts as a resist during plating processes, allowing for selective deposition of metals on specific areas of the PCB.
Electrical Insulation, Enhances the dielectric properties of the PCB, ensuring that high-voltage areas are adequately insulated.
Markings and Labels, Allows for the inclusion of necessary markings (e.g., manufacturer, UL markings) and labels (e.g., part numbers, date codes) for identification and traceability.
Color and Finish, Available in various colors and finishes to meet specific aesthetic and functional requirements, such as improving visibility for optical inspections or enhancing the appearance of LED applications.
Regulatory Adherence, Ensures that the PCB complies with environmental regulations like RoHS, which restrict the use of hazardous substances.
Solder Mask Bridges, creates bridges between individual solder pads and between solder pads, component holes, and vias to prevent solder from causing short circuits; Insulates individual conductor traces to prevent short circuits and leakage currents, ensuring reliable electrical performance.
Component Placement, helps in the accurate placement of components by providing clear demarcations and preventing solder from bridging unintended areas.
Environmental Shield, Protects copper surfaces from environmental influences such as moisture, dust, and contaminants, preventing corrosion and extending the PCB’s lifespan.
Durability, Provides a protective layer that shields the PCB from mechanical damage during handling, assembly, and operation.
Heat Resistance, Withstands high temperatures during soldering processes, especially in lead-free environments, without degrading.
OSPs are exceptionally thin organic coatings specifically formulated to preserve the solderability of copper surfaces on printed circuit boards (PCBs). These coatings work by forming a complex organo-metallic bond with the copper, which is critical for ensuring a reliable solderable finish. OSPs are particularly suitable for a range of applications, including both surface mount and through-hole assembly processes. Additionally, they offer a shelf life that supports effective long-term storage without compromising solderability, making them a practical choice for manufacturers and engineers alike.
Hot air solder level (HASL or HAL) is the process of immersing a circuit board into molten solder, immediately followed by blowing the excess molten solder out of the holes using hot air under high pressure. For the vast majority of HASL applications, the solder alloy is tin-lead. For Pb-free applications, the main alloys include tin-copper, tin-silver-copper, tin-coppernickel, and tin-copper-nickel-germanium alloys.
ENIG is a versatile surface finish consisting of a nickel layer topped with immersion gold. This configuration protects the nickel from oxidation and serves various functions, including soldering and as a bonding surface. The nickel layer acts as a diffusion barrier, preventing copper from leaching into the gold, and enhances the strength of thru holes. Gold, being a stable element that does not oxidize, ensures excellent wettability in soldering processes, contributing to the overall reliability of PCBs.
Immersion Silver (IAg) is a surface finish that forms a thin layer over copper, suitable for soldering, press-fit connections, and potentially for aluminum wire bonding. This finish protects the copper from oxidation during its shelf life and is applied using a galvanic displacement process with thicknesses ranging from 0.1 to 0.4 μm. Although the fabrication process is straightforward, the layer can tarnish when exposed post-assembly, which may lead to corrosion and functional degradation over time.
ISn is a protective layer of pure tin, applied using a galvanic displacement process. This coating safeguards the underlying copper from oxidation while ensuring excellent solderability and compliant pin connector functionality. The IPC-4554 specification mandates a minimum thickness of 1 μm to guarantee sufficient virgin tin for soldering, considering that an intermetallic layer forms over time between the tin and copper. Solderability tests and stress testing conditions are also outlined in the specification.
ENEPlG is a relatively new surface finish. This surface finish is much more expensivethan ENlG but is the only finish that is solderable without creating a brittle solderjoint and wire bondable. This is usually used in applications requiring both thesefeatures due to its costs.
Most PCBs use copper as their primary conductor. If the copper is left unprotected after finishing, it can oxidize, making soldering difficult. An ideal surface finish would possess good solderability, a flat coplanar surface, cost-effectiveness, the ability to withstand unlimited heat cycles, and minimal health and safety concerns. There are various final finishes available, each with its own advantages and disadvantages. Different finishes are more suitable for specific applications.
Union Circuits offers a wide range of PCB fabrication services, from single-sided to complex 42-layer boards. Whether you need a few prototypes for testing or large
XPC, FR-1, FR-2 are flame-retardant phenolic materials that are also highly punchable, they have excellent electrical, heat-resistant, moisture-resistant, flame-resistant and other properties as well as low cost. FR-3 is epoxy Copper Clad Laminate, it is flame retardant with high electrical properties.
CEM-1, which is a composite of paper and glass impregnated with epoxy resin, is the most popular substrate for SSBs. While not as low cost as XPC-FR or FR-2, CEM-1 has gained popularity because of its mechanical strength and also because of the relative unavailability of paper phenolic laminates.
CEM-3 is similar to FR4, but uses a composite material of a non-woven glass core and a woven glass surface instead of a full sheet of woven glass. It’s a flame retardant epoxy resin, copper-clad glass material, commonly used in double-sided PCBs.
“FR” is the abbreviation of flame retardant. As the board runs on electricity, it should be heat resistant. FR4 has much better heat resistance than FR1 and XPC due to the different composition of the layers.
Common FAQ topics. If you have specific questions in mind, feel free to ask!
XPC, FR-1, FR-2 are flame-retardant phenolic materials that are also highly punchable, they have excellent electrical, heat-resistant, moisture-resistant, flame-resistant and other properties as well as low cost. FR-3 is epoxy Copper Clad Laminate, it is flame retardant with high electrical properties.
CEM-1, which is a composite of paper and glass impregnated with epoxy resin, is the most popular substrate for SSBs. While not as low cost as XPC-FR or FR-2, CEM-1 has gained popularity because of its mechanical strength and also because of the relative unavailability of paper phenolic laminates.
CEM-3 is similar to FR4, but uses a composite material of a non-woven glass core and a woven glass surface instead of a full sheet of woven glass. It’s a flame retardant epoxy resin, copper-clad glass material, commonly used in double-sided PCBs.
“FR” is the abbreviation of flame retardant. As the board runs on electricity, it should be heat resistant. FR4 has much better heat resistance than FR1 and XPC due to the different composition of the layers.
XPC, FR-1, FR-2 are flame-retardant phenolic materials that are also highly punchable, they have excellent electrical, heat-resistant, moisture-resistant, flame-resistant and other properties as well as low cost. FR-3 is epoxy Copper Clad Laminate, it is flame retardant with high electrical properties.
CEM-1, which is a composite of paper and glass impregnated with epoxy resin, is the most popular substrate for SSBs. While not as low cost as XPC-FR or FR-2, CEM-1 has gained popularity because of its mechanical strength and also because of the relative unavailability of paper phenolic laminates.
CEM-3 is similar to FR4, but uses a composite material of a non-woven glass core and a woven glass surface instead of a full sheet of woven glass. It’s a flame retardant epoxy resin, copper-clad glass material, commonly used in double-sided PCBs.
“FR” is the abbreviation of flame retardant. As the board runs on electricity, it should be heat resistant. FR4 has much better heat resistance than FR1 and XPC due to the different composition of the layers.
