Materials Used in Multilayer PCB
The material used for multilayer pcb is usually polytetrafluoroethylene (PTFE). These boards are durable and adapt well to varying temperatures. However, they must be properly designed to ensure heat distribution and the quality of signal transmission.
Instead of building normal tracks into each layer, which could waste space, buried or blind vias are used. Also, 90 degree traces should be avoided in order to avoid EMI issues.
High-frequency laminates
A high-frequency PCB requires specialized laminate materials with low dielectric constants and loss tangents to minimize signal attenuation. These materials also have low coefficients of thermal expansion and contraction, so they bind together more tightly when temperatures fluctuate. In addition, they must be able to withstand high temperatures in the reflow oven, where soldering takes place. Finally, they must have appropriate peel off resistance and chemical and water absorption properties.
These materials are designed to meet the needs of a high multilayer pcb variety of applications, including medical devices, mobile phones, and computer and communications equipment. They are often made of copper foil with a surface finish like ENIG or OSP to prevent oxidation and improve signal transmission. They also have a low etching rate, making them easy to cut and route.
The design of a high-frequency multilayer PCB involves complex and time-consuming tasks. First, the circuit designer creates a PCB layout using advanced CAD software. Next, the manufacturer prepares the substrate and copper foil for the circuit board. They are then coated with a photo-imageable resist. The resist is then exposed to a light source that produces a pattern. The pattern is then cut with a CNC machine.
The final step is to inspect the finished product. This step is critical to ensure that the board is error-free. The inspection process includes checking for function fit, solder masking options, and trace parameters. In addition, it is important to use a contract manufacturer that has the right level of experience and domain expertise.
Immersion silver
Immersion silver is an environment-friendly surface finish that consists of a thin (5-15 micro inch) layer of pure silver. It is used to ensure the solderability of components on a PCB. It is a popular choice for high-speed signal circuits, especially those with high copper density. It is also RoHS compliant and offers good flatness and contact. However, it has its disadvantages, including tarnishing and champagne voids.
During the immersion silver process, a fabricator uses an immersion solution to deposit silver on the copper surface of a printed circuit board. The process relies on a displacement reaction, in which the silver ions displace the metal copper. First, the fabricator roughens the copper surface with a micro-etching solution and then deposits a uniform layer of silver at a controlled speed.
The immersion silver solution also helps prevent oxidation, which is caused by a chemical reaction between copper and oxygen. To reduce oxidation, the solution should be low in acidity and have a neutral pH. It should also be free of halides and water vapor, which can cause corrosion.
Using an immersion silver finish can improve the reliability of your PCBs, as it allows for greater flexibility in design and assembly. This High Multilayer PCB Supplier process is more accurate than HASL and provides a high-quality surface for the soldering process. It is also useful in reducing the cost of manufacturing high-density circuit boards, because it requires less copper than other finishes.
HASL
Hot air leveling (HASL) is a circuit board surface finish that uses a combination of solder and air to create a uniform coating of tin. The process is used to pre-tin copper pads for the assembly of components. This technique allows for easy hand soldering and is a cost-effective alternative to other types of finishes. The HASL process also offers good activity and low corrosion, and is compatible with most electronics.
During the HASL process, the board is affixed to clamps and then immersed in molten solder. The flux helps to moisten the copper surface, increase free radicals and promote the bonding of tin and copper. After the tin has been deposited, the clamps are removed and the board is cooled. The tin layer is then inspected for defects, such as rough tin surface and insufficient or excess solder. Once the tin is inspected, the board is ready to be shipped.
The HASL process can lead to uneven surfaces, which can pose a challenge for fine-pitch components. It can also cause solder bridges in closely placed pads. Because of these problems, many PCB assemblers now prefer to use ENIG instead of HASL for fine-pitch SMT applications.
Another disadvantage of the HASL process is that it uses traditional lead-based solder, which may not be ideal for some applications or regulations. This can be a problem for manufacturers who want to meet customer demands or regulations.
FR-4
The FR-4 is one of the most popular PCB materials in the industry. It uses glass fiber epoxy resin and is highly heat-resistant. It is used in a wide variety of products, including high-speed circuit boards and wireless communication devices. The FR-4’s high thermal resistance helps to reduce electromagnetic interference (EMI) between components. It also increases immunity to external noise.
The insulating material in a multilayer PCB is crucial to its performance. It must be thick enough to prevent the transmission of EMI signals between different layers. In addition, it must be flexible to enable the creation of V-grooves. It is also essential that the copper traces are laid out in a way that minimizes EMI effects. This can be achieved by placing the ground planes on separate layers and avoiding 90 degree traces, which can increase EMI and interfere with sensitive signals.
The FR-4 is also known for its moisture resistance, which is a vital attribute in a multilayer PCB. Its low moisture absorption allows it to withstand harsh environmental conditions. In fact, it is capable of surviving temperatures up to 200 degrees Celsius. Moreover, the FR-4 has a high CTI value, which means that it can withstand high voltages. This makes it an ideal choice for a high-speed multilayer PCB. This type of board is also suitable for use in industrial applications.