Impedance Calculations for Flex PCB Fabrication
Calculations for Flex PCB Fabrication
Keeping track of impedance calculations is vital in PCB fabrication. These are calculations that factor in resistance, capacitance, and inductance to determine a circuit’s transmission line impedance. This is a necessary step in creating performance-driven flex PCBs that are able to meet the demands of the application they are designed for.
Rigid-flex PCBs need to withstand frequent and repetitive bending, and the design process needs to keep this in mind. To do so, the traces and components on the rigid section need to be protected from damage during this process. This can be done by designing the flex section to be very thin and using low copper weights. In addition, the design should also limit the number of layers it uses. The more layers a flexible PCB has, the more stress it will experience during repeated bending.
The rigid flex pcb fabrication design should also avoid putting too many holes, vias, or pads on the flex area, and instead focus on placing these in the rigid section. When this is done, the flexible traces need to have sufficient length to ensure that they will reach these plated connections without losing signal integrity or breaking in the middle. For this reason, it’s recommended to use anchors and teardrops for these connections in the flex section of the board, rather than ring-type terminations. These will provide the most stability and longevity in the flex area of the design.
Impedance Calculations for Flex PCB Fabrication
Conductor layer thickness is another important consideration in flex PCB fabrication. The higher the copper layer, the more the flex circuit will have to bend in order to reach its destination. To minimize this effect, the copper layer should be kept as close to the neutral axis as possible. This can be achieved by either reducing the copper weight or decreasing the dielectric thickness.
It’s also important to note that flex PCBs can have different traces than their rigid counterparts, and this should be taken into account when performing impedance calculations. This is because the conductive layers in a flex circuit are typically made of copper with an embedded dielectric, which means they will have different impedances from rigid PCBs.
A flex circuit can have an odd mode or even mode impedance, and the designer should determine which type of impedance is desired for the circuit. Odd mode impedance is a single-ended signal, while even mode impedance consists of two identical signals with the same polarity at both ends of the circuit.
To perform an accurate impedance calculation, the flex PCB designer should use a software program that takes into account several factors, including copper thickness, dielectric thickness, and conductive layer thickness. There are a variety of impedance calculators available on the market, and some of them are specifically designed for use with flex PCBs. These calculators will be able to produce more reliable results than those based on a grid reference plane. A specialized tool like this is especially helpful for flex PCBs that need to comply with UL standards.