FR4 PCB manufacturing

FR4 PCB manufacturing

What is FR4 substrate material?

FR4, also written as FR-4, is both a name and a standard rating. The name is applied to the fiberglass-reinforced epoxy-laminated sheets used in printed circuit board manufacturing. However, the name also functions as a grade used to rate epoxy laminate sheets. The designation essentially indicates the base quality of a laminate sheet, meaning a variety of sheet materials and designs fall under the FR4 rating. The “FR” in the name stands for flame retardant, while the 4 differentiates the material from others of the same class.

The material widely referred to as FR4 is a composite structure. The most basic layer of the material is fiberglass woven into a thin, cloth-like sheet. The fiberglass gives FR4 its necessary structural stability. This innermost fiberglass layer is then surrounded and bound by a flame-resistant epoxy resin. This resin is what gives the material rigidity, among its other physical properties.

FR4 sheets are widely popular among electrical engineers and designers as a PCB base material. The low cost and versatility of the material, as well as its wealth of beneficial physical properties, account for that popularity. FR4 sheets are electrical insulators with high dielectric strength. They also feature a high strength-to-weight ratio and are lightweight and resistant to moisture. Add this to their relative temperature resistance, and FR4 material can perform well in most environmental conditions.

When choosing different types of circuit board, there are multiple strategies to consider, such as referencing performance parameters. Click at here the parameter table for conventional FR4.

How to select FR4 thickness?

When ordering a laminate board for a PCB project, the designer or electrical engineer must specify the FR4 thickness. This is measured in inch-based units, such as the thousandth of an inch, or thou, or millimeters, depending on which is most appropriate for the setting. The thickness of a sheet of FR4 ranges widely depending on the needs of the project, but it tends to range from ten thou to three inches.

While board thickness may not seem like a significant factor in the design of a PCB, in reality, it is an essential feature. Board thickness affects several aspects of the board’s functionality, which is why several factors are considered in determining the thickness of a board for design. These include the following.

1. Space: Thinner May Be Better

If space concerns the designer, a thinner FR4 board tends to be preferable. This is a predominant factor for the manufacture of smaller devices, like USB connectors and many Bluetooth accessories. Even for larger projects, smaller FR4 PCBs tend to be favored to save space within the device.

2. Connections: The Wrong One Could Result in Damage

A two-sided PCB design requires an edge connector to join the two sides. This can be a major limiting factor for the final size of the PCB since PCB edge connectors only fit a particular set of PCB thicknesses. The mating portion of a connector has to fit snugly on the side of the PCB, or else risk slippage or damage to the PCB. This is one of the primary reasons why circuit design comes before choosing materials for the circuit.

3. Impedance Matching: Essential to Maintaining Board Function

Every multi-layered board acts as a capacitor on adjacent layers. This is why the thickness of this board is so important — the thickness of the PCB FR4 material determines the thickness of the dielectric, which in turn affects the value of the capacitance.

This is an especially key factor for some high-frequency PCBs, such as RF and microwave designs. High-frequency designs focus on impedance matching as an essential component to maintain optimal board function, so getting the right capacitance for each layer is crucial.

4. Flexibility: Depends on the Application

Thinner boards can flex in some capacity. While an unusual trait, flexibility can be a positive or negative feature, depending on the application.

More flexible boards tend to be preferable in some applications where the product is regularly stressed or flexed. For example, those using boards for medical and automotive applications often prefer flexible boards due to the constant stress and flexing to which these PCBs are often subjected.

However, flexibility can be a detriment to the PCB manufacturing process, resulting in serious problems later in assembly. When handled by a machine, a more flexible board may flex when dealt with by a soldering machine, causing the component to be soldered at an angle. Additionally, this flexing has the potential to break freshly placed components and connections already on the board.

5. Design Requirements: Intended Use Impacts FR4 Thickness

Thin boards aren’t preferable in all cases, primarily due to the limitations thin boards put on PCB plans. Thin FR4 boards can’t feasibly feature grooves, and they can’t be too large without risking fracture. Thicker boards, however, can accomplish both. Always account for this when weighing options between FR4 thicknesses.

6. Component Compatibility: May Work With a Small Range

The thickness of a board can also affect the compatibility of components with the board. Just like edge connectors, many components work with a small range of board thicknesses. This is especially true for some through-hole components, for example.

7. Weight: Lighter Products May Be More Attractive

The FR4 thickness will, logically, affect the weight of the final PCB. While weight is less of an issue in some applications, it is often a consideration in consumer electronics. Lighter PCBs make for lighter products, which makes them cheaper to ship and, in some cases, more attractive to consumers.

Reliable FR4 PCB Manufacturer - GWT

1.More Choices

GWT has rich experiences in PCB manufacturing and can meet the needs of most customers. Compared to other manufacturers, we offer a wider range of options, such as various thicknesses and layers, multiple surface treatments, and different substrate materials. This makes it more advantageous for you to customize FR4 PCB to your specific requirements.

Regarding materials, we source our laminate and prepreg materials from top suppliers such as Isola, Taconic, Panasonic, and Shengyi Technology. This ensures that we provide high-quality materials that are consistent and reliable, resulting in superior circuit board.

2.Wide range of services

Unlike traditional Chinese FR4 PCB manufacturers, we are a service provider that integrates industry and trade. Our company structure comprises a manufacturing workshop, assembly workshop, sales department, purchasing department, technical department, and after-sales processing department. This means that we offer more service options, such as IC programming, design, assembly, and manufacturing, which can be either turnkey or standalone services.

3.Quality and Reliability

We are a reliable company that can provide various industry certifications, including the conventional ISO9001 and 14001, as well as the “International Automotive Industry Technical Specifications” IATF16949 and “Medical Device Quality Management System for Regulatory Requirements” ISO13485. However, at GWT, qualification certification is only one aspect of demonstrating our capabilities to customers. We also formulate stricter operating specifications and testing services, which are essential in ensuring the smooth progress of your PCB project.

4.Delivery Time

Delivery time is a crucial concern for customers when choosing PCB manufacturing services. For FR4 PCB prototype orders, we prioritize faster shipping, which typically takes only a few days. We understand that customers are eager to receive their goods promptly. When you submit your order request to us, we will provide you with an estimated delivery time based on your receiving address, the number of boards, and the level of complexity.

5.Customer Support

At GWT, we strive to impress our customers with our exceptional service and quality. To achieve this, we provide tailored customer support services to meet the unique needs of each customer. Our customers can reach their dedicated customer service representative through phone, email, chat, or social media platforms 24/7. If any technical issues arise, they are promptly forwarded to our technical department and resolved in a timely manner.

Selection of F4 PCB Board

1.High TG FR4

High TG FR4 is a type of FR4 PCB that belongs to the category of FR4 PCBs with higher curing temperatures. It is characterized by having a higher glass transition temperature (TG) than standard FR4. The glass transition temperature is the temperature at which a material transitions from a rigid, glass-like state to a softer, rubber-like state. With a TG of approximately 170-180 °C, High TG FR4 has a higher TG than the typical TG of standard FR4, which is 130-140 °C.

High TG FR4 is often considered the best choice for lead-free assembly and for securing the board from variable temperature conditions. It is commonly used in projects and applications that require high temperatures, such as power electronics, LED lighting, and automotive electronics.

2.Halogen-free FR4

The term “halogen-free” refers to the absence of the periodic table elements bromine, iodine, and chlorine in the substrate. While halogen-containing flame retardant materials provide good flame retardancy, they produce a large amount of toxic gas that is harmful to humans after combustion.

To prevent the damage caused by halogen elements, FS Tech uses phosphorus and phosphorus nitrogen instead. These materials are also suitable for lead-free soldering and have a glass transition temperature of about 150°C and a decomposition temperature of 330°C. Halogen-free substrates are ideal for devices that produce hazardous smoke when burned, such as technical instruments, and are commonly used in mobile communication systems and related projects.

3.FR4 Multilayer PCB

The FR-4 PCB is the most commonly used board in the electronics industry due to its ease of manufacturing and the extensive experience that most manufacturers have in using it. It is typically constructed as a multilayer structure, making it a suitable choice for projects that require FR4 multilayer boards. FS Technology can provide a lower price list and manufacture multilayer PCB with 1–56 layers.

Moreover, the FR4 multilayer board is composed of multiple layers of conductive materials separated by insulating layers. It exhibits good mechanical properties and enables the realization of more complex and compact designs. PCBA processing plants can easily solder components to PCBs through SMT assembly and through hole PCB assembly, thereby creating functional electronic circuits.

4.Thick Copper FR-4 PCB

Thick Copper FR-4 PCBs are made from the same base material as regular FR-4 PCBs, but the copper layer on the board is thicker, hence the name. According to the PCB Copper Thickness Guidelines, thicker copper layers can improve electrical conductivity and heat dissipation, making them the first choice for applications that handle higher currents and power, such as power supplies, motor control circuits, and LED lighting.

When designing Thick Copper FR4 PCB, it is important to consider the additional weight and cost of the thicker copper layers. Additionally, the board may require special manufacturing techniques, such as controlled impedance routing, to ensure proper performance.

5.Rigid-Flex FR4 PCB

Rigid-Flex FR4 PCBs are a type of hybrid printed circuit board that combines the durability and rigidity of FR4 material with the flexibility of a polyimide film. This allows for the creation of PCBs that can bend and twist without breaking, while also maintaining a rigid structure in certain areas. Rigid Flex PCB is ideal for applications that require both flexibility and durability, such as medical devices, aerospace, and military applications.

The design of a Rigid-Flex FR4 PCB is complex and requires careful consideration of the placement of the rigid and flexible areas, as well as the routing of the traces and vias. The use of specialized tools and software, such as 3D modeling and simulation software, can help with the design process. The manufacturing process for Rigid-Flex FR4 PCBs also requires specialized techniques, such as laser drilling and controlled depth routing, to ensure the proper alignment and functionality of the rigid and flexible layers.

FR4 PCB Material Properties

1.Temperature

In PCBs, the TG value is an index used to measure the board’s heat resistance. A higher TG value indicates a higher temperature rating, while a lower TG value indicates a lower temperature rating. PCBs made of FR4 material can withstand an operating temperature of up to 130°C, which sets a high standard for PCB temperature ratings. However, GWT recommends not exceeding 100°C, as even if the ambient temperature does not reach the rated value, the circuit board’s physical characteristics may change. As large numbers of components with different thermal tolerances are assembled onto the PCBA, it is challenging to consider all components’ heat exposure. Additionally, FR4 has low thermal conductivity, and poor design choices may cause components to heat up and become damaged. Due to FR4’s excellent electrical and mechanical properties, it is commonly used in industrial PCB, but it is crucial to consider the temperature rating of FR4 when designing circuits.

2.Thickness

The thickness of an FR4 PCB can vary depending on the specific application and design requirements. Generally, FR4 PCBs are available in thicknesses ranging from 0.2mm to 6.0mm or more. Thinner PCBs are often used in applications where space is limited, such as in mobile devices or wearable technology, while thicker PCBs are used in applications that require greater durability and strength, such as in industrial or military equipment. The thickness of an FR4 PCB can also affect its electrical properties, such as impedance and capacitance, so it’s important to carefully consider the design requirements and choose the appropriate thickness for the application.

3.Thermal Conductivity

FR4 materials are considered to have poor thermal conductivity, with a thermal conductivity of only 0.3W/(m·K), compared to copper’s high thermal conductivity of 385W/(m·K), and the general range of 10~45W/(m·K) for most materials. The thermal coefficient of metal materials is the highest. Several factors affect the thermal conductivity of an FR4 PCB, including Vias, Copper Traces, and Inner Layers.

Vias are holes created on the surface of the PCB to help dissipate heat. The principle is to spread the heat through the components to the surface of the entire PCBA by punching holes on the bare board and then transferring the heat to the external environment through convection and radiation transfer. GWT believes that this is only a way to treat the symptoms and not the root cause. If only vias are used as a heat dissipation measure, a small number of vias cannot effectively solve the problem. When the number of vias reaches a certain value, the benefits will be greatly reduced because the heat will collect in the position of the via, causing uneven heating of the entire circuit board.

Traces also play a crucial role in good thermal conductivity. If the traces are connected properly, heat can dissipate easily. For high heat dissipation, the traces must be completed.

The inner layers of the board also play a role in heat dissipation. If the layers are thicker, thermal conductivity will be reduced.

4.Density

The density of FR4 PCB depends on the thickness and number of layers of the board. Typically, the density of FR4 material is 1.85g/cm³, but the actual density of the PCB may vary depending on the design and manufacturing process.

The number of layers in the PCB can also affect its density. A single-layer FR4 PCB will have a lower density than a multi-layer FR4 PCB because the latter has more layers of copper and insulating material. The thickness of the copper layers can also contribute to the density of the PCB, with thicker copper layers increasing the overall weight and density of the board.

5.Low Hygroscopicity

FR4 PCBs have low hygroscopicity, which means they absorb only a small amount of moisture from the environment, helping to maintain their dielectric properties even in humid conditions. Moisture absorption can cause changes in the electrical properties and mechanical strength of the PCB, potentially leading to problems such as delamination, microcracks, and electrical shorts.

To avoid such situations, GWT takes effective measures:

--Storing the PCBs in a dry environment with a relative humidity below 50%;

--Wearing gloves when handling the boards to prevent transfer of oil and moisture from the skin;

--Following proper baking guidelines in wet conditions.

Mechanical Properties

FR4 PCBs have good mechanical properties, making them suitable for a variety of applications. They have high strength, stiffness, and dimensional stability, and are resistant to impact, vibration, and shock. The tensile strength of FR4 ranges from 345-414 MPa, while the flexural strength ranges from 483-586 MPa. The coefficient of thermal expansion (CTE) of FR4 is low, typically around 14-18 ppm/°C, making it dimensionally stable even under temperature changes.

Fr4 PCB VS Other

FR1, FR2, FR3, and FR4 are four different types of flame-retardant materials used in the manufacturing of printed circuit boards (PCBs).

FR1 is made of phenolic resin and paper. It has a low cost and is commonly used in low-voltage and low-frequency applications.

FR2 is made of phenolic resin and cotton. It has better mechanical properties than FR1 and is used in applications that require higher voltage and frequency.

FR3 is made of epoxy resin and paper. It has better thermal and mechanical properties than FR1 and FR2 and is used in applications that require higher performance.

FR4 is made of epoxy resin and glass fiber. It is the most widely used material in PCB manufacturing due to its excellent electrical, mechanical, and thermal properties. It is suitable for high-frequency and high-performance applications.

Rogers VS Fr4

Rogers is superior to FR4 when it comes to managing high temperatures;

FR4 is more susceptible to signal loss compared to Rogers;

FR materials have higher dissipation factor values than Rogers;

In terms of impedance control, Rogers has a different dielectric constant than FR4;

FR4 is more cost-effective than Rogers;

FR4 has a lower dielectric constant value than Rogers PCB.

Aluminum VS Fr4

Aluminum PCB have better thermal conductivity compared to FR4, enabling them to dissipate heat more effectively, making them an excellent choice for applications that require high-power components that generate a lot of heat.

FR4 is a cost-effective alternative and is cheaper than aluminum.

Due to its good mechanical strength and ability to accommodate more components, aluminum substrates are easier to PCB assembly.

Aluminum is much heavier than FR4, which can be a disadvantage in weight-sensitive applications, such as the aerospace or automotive industries.

Aluminum has the ability to shield circuit components from electromagnetic radiation.

Ceramic VS Fr4

The thermal conductivity of FR4 is much lower than that of ceramic substrates such as alumina, aluminum nitride, or silicon carbide.

FR4 PCBs require vias, metal layers, and cooling elements to achieve heat dissipation, while ceramic PCB do not require these elements.

FR4 PCBs have excellent electrical insulation performance and are cost-effective, while ceramic PCBs have high-temperature resistance.

Ceramic substrate materials are more suitable for high-price and high-profit electronic projects such as medical PCB, military electronic PCBs, or the aerospace industry, while FR4 is more suitable for consumer electronic PCB.