In the high-speed PCB design process, stack-up design and impedance calculation are crucial initial steps. While the methods for impedance calculation are well-established and largely consistent across software, the process can still be quite tedious. The real challenge lies in finding a "balanced art" between impedance requirements and manufacturing capabilities. This balance ensures that we meet our impedance control goals while also maintaining manufacturability, reducing processing costs, and avoiding unnecessary complications.
Below are some key considerations when designing a stacked impedance structure to improve your efficiency and accuracy:
1. **Use wider line widths where possible.**
Since there are process limitations on fine-line etching, it's better to avoid pushing the line width to its minimum limit. Adjusting the impedance by changing the line width can lead to costly rework or relaxed tolerance if you hit the edge of what the manufacturer can handle. Therefore, aim for a slightly lower target impedance. For example, instead of aiming for 50 ohms, calculate for 49 ohms and avoid going above 51 ohms.
2. **Maintain a consistent trend in impedance values.**
If your design has multiple impedance targets, ensure they follow a logical pattern. Avoid situations where some lines are over 100 ohms and others under 90 ohms, as this can complicate the overall design and make it harder to maintain consistency.
3. **Account for residual copper ratio and resin content.**
During the lamination process, the prepreg fills the etched areas, which affects the thickness of the dielectric material between layers. A higher residual copper ratio means less resin is present, which can impact the final dielectric constant. When specifying the thickness of the prepreg, consider the copper fill percentage to ensure accurate results.
4. **Specify glass fiber type and resin content.**
Different glass fabrics and prepregs have varying dielectric constants. Even small differences—such as between 3.5 and 4.0—can affect the single-ended impedance by about 3 ohms. Additionally, the glass fiber effect is influenced by the size of the window openings. For high-speed designs (e.g., 10 Gbps or higher), using an unspecified material may lead to signal integrity issues. It’s best to specify the exact materials or work closely with the manufacturer to choose the right ones.
Keep in mind that residual copper ratios and dielectric constants can sometimes vary from nominal values. Some manufacturers may not have the exact materials available, which could delay production or prevent the stack-up from being realized as designed. To avoid these issues, it’s highly recommended to involve the PCB manufacturer early in the design phase. Let them help define the laminate stack based on their experience and your specifications. This collaboration can reduce the number of iterations needed and help achieve a stack-up that is both ideal and feasible.
53 Modular Jack
53 Jack.We are manufacturer of 6p6c Female Connector in China, if you want to buy RJ11 Jack Full Plastic MINI,6 Pin RJ11 Modular Connector,RJ11 Jack Full Shielded please contact us.
The RJ-45 interface can be used to connect the RJ-45 connector. It is suitable for the network constructed by twisted pair. This port is the most common port, which is generally provided by Ethernet hub. The number of hubs we usually talk about is the number of RJ-45 ports. The RJ-45 port of the hub can be directly connected to terminal devices such as computers and network printers, and can also be connected with other hub equipment and routers such as switches and hubs.
6p6c Female Connector,RJ11 Jack Full Plastic MINI,6 Pin RJ11 Modular Connector,RJ11 Jack Full Shielded
ShenZhen Antenk Electronics Co,Ltd , https://www.antenk.com