PCB design seven basic and key techniques for beginners and experienced professionals(1)

- Nov 03, 2018-

1. Be familiar with the manufacturing process in this era when the IC manufacturers of non-wafer factories are in charge, many engineers actually do not know the PCB production steps and chemical processing techniques based on their design files;This is not surprising.However, this lack of practical knowledge often leads novice engineers to make unnecessarily complex design decisions.Is the design really that complex?Can't bigger grids be used for wiring, thus reducing circuit board costs and improving reliability?There are other mistakes that novice designers can make, as well as unnecessary oversize holes and blind and buried via.Those advanced through-hole structures are a powerful tool for PCB designers, but their effectiveness is highly contextualized, and while they are available, they do not mean they have to be used.A blog post by Bert Simonovich, a PCB design expert, addressed the question of the ratio of through-hole sizes: "a 6-to-1 through-hole ensures that your circuit board can be manufactured anywhere."For most designs, with a little thought and planning, you can avoid those high-density (HDI) features and again save costs and improve design manufacturability.Not all PCB foundries are good at the physical and hydrodynamic capabilities required to conduct copper plating on ultra-small or dead-ended holes.Remember, one bad hole can destroy the entire circuit board.If you have 20,000 through-holes in your design, you have 20,000 chances of failure.When the HDI was used unnecessarily, the failure rate soared.

2. Circuit diagram can simplify the design task. Sometimes it is just a simple circuit board.Especially if you've already done one or two designs.But for someone who first designed a PCB, drawing a circuit diagram can be a daunting task.Skipping circuit diagrams is a strategy often adopted by novice and moderately experienced design engineers, but develop your wiring from a complete circuit diagram that can be used as a reference, helping to ensure that your wiring connections are fully completed;Here's why.Firstly, circuit diagram is the visual presentation of PCB circuit, which can convey multiple levels of information.The subarea of the circuit is mapped in several pages in detail, and the functional equivalent of the zero component can be arranged in adjacent locations, regardless of the final physical layout.Second, since the circuit diagram symbol will indicate each pin of each component, it is easy to check out the pin that is not online.In other words, whether the formal rules for describing the circuit are followed or not, the circuit diagram helps you quickly visually determine the circuit to ensure its integrity.In PCB design, if a circuit diagram can be used as the basic template, can simplify wiring tasks.Use circuit diagram symbols to complete the links, and you overcome the routing challenge without having to think about those links over and over again.In the end, you'll save design rework by grabbing a link that was missed during the first revision.

3. Use automatic wiring device but don't rely on most professional PCB CAD tools.For PCB connections, automatic wiring is not a one-click solution, and you should still know how to do it by hand.Automatic wiring device is a highly configurable tool. In order to give full play to their role, each task should carefully and thoughtfully set the parameters of the device and even consider individual modules on a single PCB. In short, there is no appropriate basic universal default value.When you ask an experienced design engineer, "which automatic wiring device works best?"They would answer, "something between the ears (eyes);"And they are serious.The routing process is more like an art like an algorithm, and is heuristic in itself, so it is very similar to the traditional backtracking algorithm.Backtracking algorithm is very suitable for finding solutions, especially for cases where path selection is limited, such as maze or puzzle.But in an open, no-holds-barred situation, such as a pre-positioned PCB with zero components, backtracking algorithms can't play to the strengths of finding optimized solutions.Unless the constraints of the automated wiring unit are carefully fine-tuned by the engineer, the finished wiring will still need to be manually checked for weaknesses in the backtracking algorithm's results.The routing size is another problem. The automatic wiring device cannot determine 100 percent how much current you intend to pass through a routing line, so it can't help you determine how wide to use.The result is that most automatic wipers produce runs that do not fit specifications.When you're thinking about using an autoloader, ask yourself, "how much time do I have to manually wire after I've set the autoloader's constraints on the board, or even after I've set constraints on every route on the circuit diagram?"An experienced design engineer will devote most of his or her energy to the initial component layout, and almost half of his or her design time will be devoted to optimizing component layouts in three ways: