Schematic common mistakes
1) The ERC report pin has no access signal:
b. The inconsistent grid properties were modified when creating components or placing components, and the pins and lines were not connected;
c. When creating a component, the pin direction is reversed, and it must be connected to the non-pin name end;
d. The most common reason is that the project file is not created, which is the most common mistake for beginners.
2) The component runs out of the drawing bounds: The component is not created in the center of the drawing paper of the component library.
3) The netlist of the created project file can only be partially transferred to the pcb: global is not selected when generating the netlist.
4) When using self-created multi-part components, never use annotate.
Common mistakes in PCB
1) Report NODE not found when the network is loaded:
a. The components in the schematic diagram use packages that are not in the pcb library;
b. The components in the schematic diagram use packages with inconsistent names in the pcb library;
c. The components in the schematic use packages with inconsistent pin numbers in the pcb library. Such as triode: pin number in sch is e, b, c, while in pcb it is 1, 2, 3.
2) It always fails to fit on one page when printing:
a. It is not at the origin when creating the pcb library;
b. The components have been moved and rotated many times, and there are hidden characters outside the pcb board boundary. Choose to show all hidden characters, shrink the pcb, and move the characters inside the boundaries.
3) The DRC reporting network is divided into several parts:
Indicates that the network is not connected, look at the report file, use the CONNECTED COPPER to find.
For more complex designs, try not to use automatic routing.
Common mistakes in PCB manufacturing
1) Pad overlap:
a. Causes heavy holes. When drilling, the broken drill and hole damage are caused by multiple drilling in one place.
b. In a multi-layer board, there are both connection pads and isolation pads at the same position, and the board is shown as • isolation and connection errors.
2) Improper use of graphics layer:
a. Violating the conventional design, such as the component surface is designed on the Bottom layer, and the soldering surface is designed on the TOP layer, which is misleading.
b. There is a lot of design rubbish on each layer, such as broken lines, useless borders, callouts, etc.
3) The characters are unreasonable:
a. The characters cover the SMD solder tab, which brings inconvenience to the PCB continuity detection and component welding.
b. The characters are too small, making screen printing difficult, and too large will make the characters overlap each other, making it difficult to distinguish. The font is generally >40mil.
4) Single-sided pad setting aperture:
a. The single-sided pad is generally not drilled, and its aperture should be designed to be zero, otherwise the coordinates of the hole will appear at this position when drilling data is generated. Such as drilling should be special instructions.
b. If the single-sided pad needs to be drilled, but the aperture is not designed, the software will treat this pad as an SMT pad when outputting electrical and ground data, and the inner layer will lose the isolation disc.
5) Draw pads with fill blocks:
In this way, although the DRC inspection can be passed, the solder mask data cannot be directly generated during processing, and the pads covered with solder resist cannot be soldered.
6) The electric stratum is designed with both the heat sink and the signal line. The positive image and the negative image are designed together, and there is an error.
7) Large area grid spacing is too small:
The grid line spacing is < 0.3mm. During the PCB manufacturing process, the pattern transfer process produces broken films after development, causing wire breakage. Increase the difficulty of processing.
8) The graphics are too close to the outer frame:
The spacing should be at least 0.2mm or more (more than 0.35mm at the V-cut), otherwise the copper foil will warp and the solder resist will fall off during the external processing. Affects the appearance quality (including the inner copper skin of the multilayer board).
9) The design of the outline frame is not clear:
Many layers are designed with borders, and they do not overlap, making it difficult for PCB manufacturers to determine which line to form. The standard border should be designed on the mechanical layer or the BOARD layer, and the internal hollowing out should be clear.
10) Graphic design is uneven:
When the pattern is electroplated, the current distribution is uneven, which affects the uniformity of the coating and even causes warpage.
11) Short shaped hole:
The length/width of the special-shaped hole should be >2:1, and the width >1.0mm, otherwise the CNC drilling machine cannot process it.
12) The positioning hole for milling shape is not designed:
If possible, design at least 2 positioning holes with a diameter of >1.5mm in the PCB board.
13) The aperture is not clearly marked:
a. The hole diameter should be marked in metric system as far as possible, and it should be incremented by 0.05.
b. As far as possible, merge the apertures that may be merged into one pool area.
c. Whether the tolerances of metallized holes and special holes (such as crimping holes) are clearly marked.
14) The inner layer wiring of the multilayer board is unreasonable:
a. The heat dissipation pad is placed on the isolation tape, and it is easy to be unable to connect after drilling.
b. There is a gap in the design of the isolation belt, which is easy to be misunderstood.
c. The design of the isolation belt is too narrow to accurately judge the network
15) Design problems of buried blind via plate:
The significance of designing buried blind via plate:
a. Increase the density of the multi-layer board by more than 30%, reduce the number of layers and reduce the size of the multi-layer board
b. Improve PCB performance, especially control of characteristic impedance (conductor shortening, aperture reduction)
c. Improve PCB design freedom
d. Reduce raw materials and costs, which is conducive to environmental protection.
Others attribute these problems to work habits, and the people who are in trouble often have these bad habits.
lack of planning
As the saying goes, "If a person doesn't plan ahead, he will find trouble coming." This of course also applies to PCB design. One of the many steps to making a PCB design a success is choosing the right tools. Today's PCB design engineers can find many powerful and easy-to-use EDA kits on the market. Each has its own unique capabilities, advantages and limitations. Also, it should be noted that no piece of software is foolproof, so issues such as component packaging mismatches are bound to occur. It is possible that no single tool will meet all of your needs, however, you must do your research beforehand and try to find the best product for your needs. Some information on the Internet can help you get started quickly.
poor communication
Although the practice of outsourcing PCB design to other vendors is becoming more common and often very cost-effective, it may not be suitable for high-complexity PCB designs where performance and reliability Sex is extremely critical. As design complexity increases, face-to-face communication between engineers and PCB designers is critical to ensure accurate component placement and routing in real time. This face-to-face communication will help save costly rework later on. do (rework) work.
It is also important to invite the PCB board manufacturer early in the design process. They can provide initial feedback on your design, and they can maximize efficiency based on their processes and procedures, which will save you considerable time and money in the long run. By letting them know your design goals and involving them in the early stages of PCB layout, you can avoid any potential problems and shorten your time-to-market before your product goes into production.
Failure to thoroughly test early prototypes
Prototype boards allow you to prove that your design is working to original specifications. Prototype testing allows you to verify the functionality and quality of the PCB, as well as its performance, before mass production. Successful prototype testing requires a lot of time and experience, but a strong test plan and a clear set of goals can reduce evaluation time and also reduce the likelihood of production-related errors. If any problems are found during prototype testing, a second test on the reconfigured board is required. Include high-risk factors early in the design process, and you'll benefit from multiple iterations of testing to identify any potential problems early, reduce risk, and ensure plans are on schedule.
Using inefficient layout techniques or incorrect components
Smaller, faster devices allow PCB designers to lay out complex designs that will use smaller components to reduce footprint, and they will also be placed closer together. Using technologies such as embedded discretes on internal PCB layers, or ball grid array (BGA) packaging with tighter pin pitch, will help reduce board size, improve performance, and preserve space for You can redo it after you get to the problem. When working with components with high pin counts and smaller pitches, it is important to choose the correct board layout technique at design time to avoid problems later and minimize manufacturing costs.
Also, be sure to study carefully the range of values ​​and performance characteristics of the replacement components you plan to use, even those marked as drop-in replacements. A small change in the characteristics of a replacement component can be enough to screw up the performance of the entire design.
Forgetting to back up your work
Back up important data. Do I still need to remind me? At the very least, you should back up your most important work and other hard-to-replace files. While most companies back up all of the company's data on a daily basis, some smaller companies may not do this, or if you're someone who works from home. Backing up data to the cloud is so easy and cheap these days that there is really no excuse not to back up your data and keep it in a safe place to protect it from theft, fire, and other local disasters.
be a solo island
While you may think your designs are flawless and that making mistakes is simply not your style, many times your peers will see mistakes in your designs that you didn't notice. Sometimes, even if you know the intricate details of a design, someone with less exposure to it may be able to maintain a more objective attitude and provide valuable insights. Regularly reviewing your designs with your peers can help identify unforeseen issues and keep your plans on track and within budget.
Of course, mistakes are inevitable, but as long as you learn the lesson, you can design a great product next time.
Shenzhen Ever-smart Sensor Technology Co., LTD , https://www.fluhandy.com