Best Practices for Using Generic Components in Your PCB Project
Anytime you need to create a new design, you’ll start your search for the perfect components to give your new product the functionality it needs. Everything from resistors to complex ICs and powerful processors need to have component footprints and schematic symbols. The strategy is often to start by selecting specific components from the supply chain first, then place them into design documents.
One strategy to approach a new design is to place generic components into the schematic, rather than selecting specific MPNs for your BOM. However, designers need to be careful with this strategy and carefully plan out their designs before placing a large number of generics. If you want to make the most of generic components in your PCB projects, pay attention to these guidelines to help you avoid redesigns and streamline your design process.
Best Ways to Use Generic Components
Generic electronic components are schematic symbols, PCB footprints, and 3D models that can be used as CAD data for many different parts. Physically, there are no “generic” electronic components per se; generic components only truly appear in CAD documents and design files. However, there are many components that have the same land patterns, mechanical outlines, and electrical ratings as this ensures compatibility between different components.
To get started with generic components in your PCB projects, it helps to understand which components are best used as generics. Before you start adding generics into your schematics, remember that you may need to place these same generics in your layout before you decide on specific MPNs for your parts. Determining which components are best used as generics first lets you push back your sourcing tasks until later in the design process.
A Process for Using Generic Components
The ideal process for using generic components in a PCB project involves working with generics during front-end design, and ultimately source the components once the design is finished and has received signoff. Here’s an overview of the best process for using generic components:
- Determine which components will be placed as generics based on package size, pin count, land pattern, and availability (check the supply chain first!).
- Place the chosen generics in your schematics and, if necessary, in your PCB layout.
- Once the layout is finished, assign MPNs and supplier information to the component in the properties panel.
- In the event that you need to use an alternate with a different package size, locate this with a parts search engine and download the CAD data into your project.
Doing this properly requires success in the very first step; using generic symbols and footprints for some components will set you up for unnecessary redesigns. Let’s look at some components that are prime candidates for placement as generic before looking into the supply chain.
Choosing Generic Components
It’s usually best to stay away from using generic components in a PCB layout and confine yourself to the schematic. However, if you do plan to use generic components in your PCB layout, here are some of the best candidates for placement in your design:
- SMD passives, diodes, LEDs, and other 2-terminal devices with standard packaging
- Discrete transistor packages (both SMD and through-hole)
- Common connectors, such as pin headers or other standardized connectors
- Simpler ICs with low pin count
- Components that have generic part numbers (e.g., 74 series logic)
One point you’ll notice here; generics are best used when they have low pin count, when they come in standard packages, or when already have a generic part number. More complex components with non-standard footprints or complex pinouts should probably not be used as generics. Passives are prime candidates for placement as generics; if a desired part is unavailable there are hundreds of alternative options. Other packages like through-hole or SMD discrete transistors come in standard packages (SOT, TO, etc.) and there are many readily available components with comparable specs.
Why does the complexity of a footprint matter? Placing a footprint with an unstandardized pinout or simply a high pin count can create a risk of a later redesign. If the desired component is unavailable, an alternative might have a different pinout, which can require significant rerouting if pin count is high. When the pin count is low, it’s usually an easy matter to reroute as long as the package is similar. SMD passives are great as generics because swapping out for a different package is simple; all that changes is the land pattern.
Using Generics in Your Design Libraries
One way designers can create generic components is to cobble together library data from past projects. In essence, they have to create components that have symbols, footprints, and 3D models from specific parts in an old project. The old CAD data is extracted from an existing library, then it’s assigned to the new component. Some libraries of generic components do not include any footprints and are only useful in the schematic, so check for available footprints if you plan to place generics in your PCB layout.
Altium Designer and the Altium 365 platform make this process easy by allowing design data to be stored on a managed cloud server. Component libraries can be migrated to your Altium 365 Workspace, and specific components can be created quickly from existing CAD data. This is much faster than recreating CAD data from scratch or manually extracting CAD data from old libraries.
The easiest way to access generic footprints, symbols, and 3D models from commercially available components is to use the Altium Content Vault within Altium Designer. When creating a new component, accessing the Content Vault will open the Manufacturer Part Search panel in Altium Designer, and existing CAD data for COTS components can be instantly imported into a new component. The image below shows an example for creating a generic component with the same footprint as a 2N7002W transistor. Note that the supplier and manufacturer information does not appear in this generic component, but it has a common SOT footprint that can be assigned to many COTS transistors.
Support for Generics in Altium Designer and Altium 365
The newest version of Altium Designer and Altium 365 now offer a set of generic components you can start using in any project. Generics can be accessed from the Components Panel in Altium Designer, or a generic component can be created through the web instance in Altium 365. These can then be imported into a new design just like any other component, but you’ll save time as you don’t need to create these generics on your own. You can read more about working with generic components in the Altium Designer documentation.
When you want an easy way to create, access, store, and share data for generic components, Altium Designer® and Altium 365™ create an ideal environment for collaborative PCB design and data management. You can make data available to collaborators, track revisions, and manage all aspects of your design data through Altium Designer®.
Thanks to the integration between Altium Designer and Altium 365, designers have everything they need to track and share project data with a single platform. We have only scratched the surface of what is possible to do with Altium Designer on Altium 365. You can check the product page for a more in-depth feature description or one of the On-Demand Webinars.