When it comes to snake lines, many PCB engineers are not unfamiliar with them. Snake lines are a commonly used routing method in PCB design, primarily aimed at adjusting delays and meeting system timing design requirements. However, many engineers often misuse snake lines, leading to reduced signal quality and a less aesthetically pleasing board. So how can we reasonably use snake lines in PCB routing? Do engineers know?
Generally speaking, many senior engineers have the following attitude towards snake lines: Since snake lines can degrade signal quality, they should be avoided as much as possible during routing. However, in actual PCB design, to ensure that signals have sufficient hold time or to reduce timing skew between signals in the same group, snake lines must be used.
1. What Are the Uses of Snake Lines?
Snake lines have various functions and can provide different capabilities based on board requirements, specifically as follows:① Compensation Function: The main function of snake lines is to compensate for the parts with shorter delays in “related signals of the same group”. These parts have little or no additional logical processing compared to other signals. A classic application is the clock line, as it does not require any logical processing, so its delay is shorter than that of other related signals.② Reception Antenna: This routing method is often seen in mobile phones or radios because some antennas utilize the PCB snake line form to achieve their function.③ Filtering Function: In RF circuits, snake lines can form an LC circuit, which has a filtering effect on signals of certain frequencies.④ Fuse: Short and narrow snake lines can be used as fuses.⑤ Other Functions: Snake lines serve different purposes in various applications. For instance, when they appear in a computer board, they act as a filtering inductor to enhance the circuit’s anti-interference capability; when they appear in a computer motherboard, they are used for clock signals, such as PCI Express and AGP, serving the purpose of impedance matching and filtering inductance.
2. How to Use Snake Lines Effectively?
The following content provides some suggestions for engineers when dealing with snake lines, hoping to be helpful: ① Try not to use snake lines; ② The signal transmission delay caused by snake lines in strip lines is less than that in microstrip lines; ③ Minimize the coupling length Lp of snake lines, where Lp’s delay should be less than or equal to 6Tr (parallel coupling length Lp: less than or equal to Tr (inches)); ④ If snake lines must be used, try to use snake lines at arbitrary angles, which can effectively reduce mutual coupling; ⑤ If the signal line has strict requirements for speed and timing, avoid using snake lines as much as possible; ⑥ Increase the distance S between parallel line segments, which should be at least greater than or equal to 4H (H refers to the distance from the signal line to the reference plane).
In summary, having more snake lines on a PCB does not necessarily mean it is more advanced; there are both advantages and disadvantages. Engineers need to reasonably decide whether to adopt snake lines based on the actual situation of the PCB.
Additionally, you can also check out the newly launched “90-Day PCB Practical Talent Training Course by Fanyi Education”, which is a corporate training course specifically designed for companies.
This course is created by multiple top PCB design engineers and is a training course specifically for PCB engineers, using practical exercises to ensure a worry-free learning experience for engineers, greatly shortening the learning cycle, enhancing their project experience and technical level, and can customize courses based on corporate models and development prospects to enhance the competitiveness of the enterprise. There are many new product discounts, hurry and grab!
▼ Scan the QR code to register or inquire ▼
Registration fee: Register 3 get 1 free, register 5 get 2 free
For corporate team registrations, the minimum is 2785/personShare, like, and see more, isn’t it great to click me?
This article is an original piece by Fanyi Corporate Training, please indicate the source when reprinting!
Submissions/Recruitment/Advertising/Course cooperation/Resource exchange, please add WeChat: 1323741820