Multilayer PCB
Modern day consumer electronics such as smartphones and microwaves use multilayer pcb. This type of PCB has various layers that allow it to operate at high frequencies. It also requires a return path or ground level to prevent EMI (electromagnetic interference) issues.
The process of making a multilayer PCB starts with the design using software like Eagle, Proteus Altium and KiCAD. Then the layers are fabricated by laminating sheets of inner layer core, prepreg and copper foils.
Layer Configuration
The layer configuration of a multilayer PCB has a significant impact on the performance of the board. For example, high-speed designs may require a stripline layer structure for signal routing and the proper ground plane arrangement to reduce crosstalk. Also, areas of analog and digital circuitry need to be separated with their own ground planes for optimal performance.
These multilayer boards have several conductive layers that are separated by insulation and are bonded with prepreg to form a rigid board. They can be fabricated in a variety of shapes and sizes, including single-sided, double-sided, and quad-layer. They are widely used in consumer electronics such as smartphones, tablets, and microwaves.
The layer stack-up of a multilayer PCB determines how well it will perform and how expensive it will be to manufacture. It is important to understand the layer configuration before starting to layout the PCB. This is because a change in the layer configuration could significantly alter the impedance and EMI performance of the circuit board. The best way to do this is by working with a manufacturer that can advise on the best layer stack-up for your specific needs.
Via Configuration
In multilayer PCBs, vias are electric connections between different layers of the circuit board. They are usually referred to as standard vias and can be found multilayer pcb on the top and bottom of the circuit board.
The layout of these vias is crucial to ensure proper signal flow in the circuit board. For example, sensitive signals may need to be routed on inner layers adjacent to ground planes in order to reduce potential broadside coupling and crosstalk. It’s also important to make sure that via holes and barrels are kept to a minimum distance from copper areas on inner layers. This will help to prevent thermal expansion and improve fabrication yield.
It’s also important to keep the via configuration in mind when preparing the multilayer PCB for fabrication. This includes ensuring that the PCB’s layer stack-up is compatible with the capabilities of the fabrication shop. For instance, it’s important to consider the maximum aspect ratio of the backplane via hole and the minimum fabricated hole size (FHS). The ideal fabrication material for the PCB depends on the performance requirements of the circuitry, which may influence the layer count and configuration.
Copper Traces
The copper traces on a multilayer pcb are the conductive paths that transmit power and signal. These traces must be carefully designed in order to meet various electrical and thermal requirements. A few key considerations include trace width, thickness, and current handling capacity. A broader copper trace can better dissipate heat from components because it has a larger surface area.
In addition, wider traces are easier to fabricate. The etching process has more pronounced effects on long, isolated traces, which is why it is recommended to make them as wide as possible. For example, a 20-mil trace can tolerate much more loss of metal during etching than a 2-mil trace can.
The width of a copper trace also affects its resistance and current handling capacity. For instance, a thinner trace has a lower resistance than a thicker one. However, a thin trace is more susceptible to thermal stress and is less likely to conduct current efficiently. The optimum thickness of a copper trace depends on the type of PCB and its current handling capabilities.
Substrate Materials
The substrate materials of multilayer PCBs are layered and glued together using heat and pressure. The material must be able to withstand high temperatures without breaking down or releasing gases. The substrate also needs to have a low coefficient of thermal expansion, which reduces stress and strain on the board.
Different substrate materials are used in different applications. The most common are FR-2 and FR-4, which are glass-reinforced epoxy laminates. They can withstand high temperatures and are resistant to thermal and electrical problems. They are also very durable and can withstand rough handling.
Multilayer PCBs require more complex routing than single-sided ones, so it’s important to plan ahead. Make sure there is sufficient space for the copper areas and that the copper lines are not blocked by the ground planes. Also, consider the spacing between signal layers, which can affect signal transmission and noise levels. To avoid this, use buried or blind vias, which are holes that penetrate only the necessary layers. This will prevent them from affecting the signal return path and allow for better performance.
Delamination
While multilayer PCBs have many benefits, they also pose a number of challenges. One such challenge is delamination, which occurs when the board loses its integrity due to gaps in the layers of the copper. These gaps can occur on the surface or in the internal layer.
A common cause of this problem is moisture that seeps through the resin during production and curing. This can lead to delamination or measling, which causes the top of the board Multilayer PCB Supplier to crack and peel away. It can also occur if the board is exposed to high temperatures.
To prevent this from happening, the manufacturer must use proper lamination techniques. This involves alternating sheets of core, prepreg, and foil in the manufacturing process. Then, pressure, heat and vacuum are applied to the stack to bond it together. This helps prevent moisture from entering the inner layers. Additionally, the manufacturer must ensure that the layers have symmetrical designs to avoid bow and twist. This is because asymmetric designs will create unbalanced stress conditions.