When there are multiple rules defined for a rule category, Altium applies a priority ranking system to decide which rule will be executed. Notice in my rule hierarchy that there are now two short circuit rules, listed in descending priority: However, I can modify my design rules so that this connection is allowed by manipulating the rule priority. The default Short-Circuit rule will prevent me from making this connection (or at least give me a warning… more on this distinction later). The tie point on the board (where the shield and ground meet) will usually be a copper region to which both nets will connect. However, I will sometimes create separate nets for my Ground and Shield connections so that I can apply different rules and routing techniques to each. In general, short circuits on a PCB are a bad thing. An example that has popped up on a few of my past designs applies to the Short Circuit rule (Electrical -> Short-Circuit). There may be situations in your design where two different constraints of the same design rule might apply for different groups of components or traces. Most of the rules have associated diagrams that illustrate what is being controlled. Here, any two items that are on different nets (3.3V and Ground, for example) are required to be no less than 10 mils apart. The Constraints are then evaluated for each object returned by the queries. For anyone new to the query system in Altium, I recommend reading this article on the Altium Wiki. By default, the query is simply “All” which means that the design rule is applied to every object in the design. In the case of the electrical clearance rule, two queries are executed: one to pick the first copper feature, and the next to pick the second.
#ALTIUM PCB DESIGN ROOMS HOW TO#
Highlight that rule in the tree view on the left side of the editor to show the details of the constraint.Īltium decides how to apply design rules by evaluating one or more queries. That rule is captured under Electrical -> Clearance. Let’s go back to the example earlier in this post that defines a minimum separation between copper features. Expanding a category shows the individual rules that can be modified for each.
The Design Rules are divided up into several different categories, like Electrical, Routing, Signal Integrity, etc. The editor window will look like the following: Then, open the PCB Rules and Constraints Editor by clicking Design -> Rules… To get an idea of the range of design rules available within the Altium PCB Editor, open an existing design or start a new PCB project. Luckily this is a straightforward process in Altium, and we’ve developed some best practices that you can use to get going quickly. The standard rules that have been developed cover a large chunk of the playing field, but the designer of any reasonably complex board will need to refine these default rules to match the application.
The downside is that there isn’t a single set of design rules that can play nicely with every PCB design. As a result, tools like Altium are made to be as flexible as possible. The range of possible applications for a printed circuit board is amazingly broad. Depending on the user’s preferences, errors can either be reported in the background or prevented in real-time. As the designer places and routes components, Altium will check the board against this rule set. An example rule might be that the minimum distance between two copper board features (like a trace and the annular ring of a via) must not be closer than 5 mils (5 thousandths of an inch). In the context of PCB design, Design Rules are a set of requirements, restrictions, and constraints that the board must meet in order to be considered a valid design. The most fundamental of these safeguards are the Design Rules.
#ALTIUM PCB DESIGN ROOMS SOFTWARE#
Luckily, many modern software tools provide safeguards to catch critical mistakes before they’re sent out to your favorite PCB fabricator. Unfortunately, none of them apply to PCB design.ĭesigning and developing printed circuit boards can be an unforgiving process: placing a critical analog line just a few millimeters closer to a noisy clock line might be the difference between a functional widget and an expensive drink coaster.
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