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This article will explore seven basic (and critical) skills and strategies for both novice and veteran printed circuit board (PCB) design. As long as you pay more attention to these skills in the PCB design process, you and your team can reduce re- Design times, shorten design time, and ease the task of diagnosing the overall design results; let us look at them one by one below.
1. Familiar with PCB factory manufacturing process
In this era of fabless IC industry dominance, many engineers actually don't know the PCB production steps and chemical treatment processes based on their design files; this is not surprising. However, this lack of practical knowledge often leads novice engineers to make unnecessary and more complex design decisions.
Does the design really need to be that complicated? Isn't it possible to use a larger grid for wiring, thereby reducing the cost of the circuit board and improving reliability? Other mistakes that PCB design novices are likely to make are unnecessary small via sizes, blind vias and buried vias. Those advanced through-hole structures are a weapon for PCB designers, but their effectiveness is highly contextualized. Although they are usable tools, they do not mean that they must be used.
2. The circuit diagram can simplify the design task
Sometimes just designing a simple circuit board, drawing schematics (schematic) seems to be a waste of time; especially if you already have experience in completing one or two designs. But for people who are designing PCBs for the first time, drawing circuit diagrams can also be a difficult task. Skip the circuit diagram is a strategy often adopted by novices and design engineers with moderate experience, but please develop your wiring from a complete circuit diagram that can be used as a reference to help ensure that your wiring connections can be completed. ; The following is the reason.
First of all, the circuit diagram is the visual presentation of the PCB circuit, which can convey multiple levels of information; the sub-areas of the circuit are drawn in detail on several pages, and the components corresponding to the function can be arranged in adjacent positions, regardless of the final physical layout. Secondly, because the circuit diagram symbol will mark each pin of each component, it is easy to check the disconnected pins; in other words, regardless of whether the formal rules describing the circuit are followed, the circuit diagram helps you quickly visualize Determine to ensure the integrity of the circuit.
When designing the PCB, if there is a circuit diagram that can be used as a basic template, it can simplify the wiring task. Use the circuit diagram symbols to complete the link, and at the same time you will overcome the wiring challenge without having to think about those connections; in the end, you will save the design rework because you have caught the wiring connections that were missed in the first revision.
3. Use automatic router but don't rely on it
Most professional PCB CAD tools have automatic routers, but unless you design the PCB very professionally, the automatic routers can only be used to make the design preliminary; for the PCB circuit link, the automatic router is not a one-click For the finished solution, you should still know how to wire it manually.
When you consider using an auto-router, ask yourself: “After I set the auto-router constraints for the board, and even set the constraints for each trace on the circuit diagram, how much time do I have? Manual wiring?" Veteran design engineers will focus most of their energy on the initial part layout. Almost half of the entire design time is devoted to optimizing the component layout from the following three aspects:
Simplified wiring-minimize the crossing of flying wires (rat's nest, or rat's nest, rat's nest) and so on.
Proximity of components-the shorter the winding, the better.
Signal timing considerations.
4. Consider the board size and current
Most people engaged in electronic design know that, just like a river walking along a river, flowing electrons may also encounter throat points and bottlenecks; this is directly applied to the design of automotive fuse. By controlling the thickness and shape of the trace (U-shaped bending, V-shaped bending, S-shaped, etc.), the fuse can be calibrated to blow at the throat point when the current is overloaded.
5. Avoid the risk of splinters
Sliver is a manufacturing error, which can be best managed through proper circuit board design (Figure 1); in order to understand the problem of sliver, we need to review the chemical etching process. Chemical etching is to decompose unnecessary copper, but if the part to be etched is particularly long, thin, and flakes, those shapes will sometimes be peeled off before being completely decomposed; such lobes will float in the chemical solution. It may fall randomly on another circuit board.
In this case, the narrow shield between the traces is safe for the circuit board
Figure 1 In this case, the narrow shield between the traces is safe for the circuit board.
It is also possible that the risk is that the split remains on the original circuit board; if the split is narrow enough, the acid pool may corrode enough copper below to partially peel off the split. As a result, the slivers stuck to the circuit board like flags and floated around, and in the end they inevitably fell on the board and caused other traces to short-circuit.
6. Follow DRC
The setting of the auto-router is usually aimed at the design function, and the Design Rule Checker (DRC) is generally used to capture the manufacturer’s design constraints; although the setting process is also cumbersome, it is much better than the auto-router . Most design teams will eventually establish a set of design rules with the goal of standardizing bare board production costs, maximizing yield, and making assembly, inspection, and testing as consistent as possible.
In order to solve all these problems, many PCB design tools have built-in DRC-some tools call them "constraint managers"-when you are editing, DRC will interactively mark design violations; and Once you have set the DRC rules for the manufacturer of your choice, be prepared to take mistakes seriously.
7. Get to know existing foundry partners
After discussing the DRC settings, this last PCB design secret is almost-but not completely-superfluous; besides helping you set the DRC rules correctly, it is important for your circuit board design to be sent to the manufacturer. As far as I know, I can get some additional pre-entry assistance.
