What Is a PCB Footprint? Easiest Guide to Understand Basic Concepts

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The pcb footprint shows where components need to be placed in the pcb layout, and they become part of the production file that is sent to the manufacturer once you start production. Since part of your footprint becomes part of the stencil used for resist printing and etching, they must be very precise, right down to the solder mask footprint and pad spacing.

We will explain how to create a footprint pattern "footprint" for parts. This time, I will use an existing library.

Prepare a board pattern for soldering in advance for the parts placed on the circuit diagram. When designing a board, the board is completed by arranging those patterns and designing the copper foil that connects the pads (the soldered parts of the terminals of the parts).

How to create pcb footprints?

Many CAD libraries, including KiCad, already have a library of footprints. The fastest way to easily create a board is to use the footprints that are included as standard. This time, we will collect footprints of LEDs and capacitors that can be used immediately and set them up.

What's included in the pcb size checklist is more important than the location of the pads on the component. Courtyard areas, component designators, and more are coded in your component model, and once you've placed the footprints, they'll show up directly on the pcb layout.

 If the footprint isn't right, you might go through part of the manufacturing process before someone notices a problem with your board. Don't be caught off guard by an incorrect footprint, use our pcb footprint checklist to help you avoid problems and build a smooth design workflow.

PCB packaging problem

Every component that appears on the board layout will have a pcb footprint. Whenever you start a new project and jump into a layout, the schematic symbols and pcb footprint must be correct before creating a single design file.

 In my experience, pcb footprints are more prone to some sort of problem than schematic symbols. This is why you should develop a pcb footprint inventory and process for validating component pcb footprints.

The footprint of each pcb will contain the following elements:

l Location of pads or holes. This shows the location of the mounting pads (for SMD components) or mounting holes (through-hole components). These locations are used for welding and must be designed accurately.

l Courtyard and profile. This is like a reserved area in your pcb footprint, i.e. no other components can be placed in the pcb footprint courtyard.

l Reference code. This alphanumeric** provides a unique identification symbol for a component in schematics and pcb layouts.

Pin-1 code name: Some elements may have arbitrary orientations (eg qfp and dip elements). Pin 1 indicates the correct orientation for the assembler.

Mechanical Elements in PCB Footprints

 Some elements may have mechanical elements or overhangs that may extend over the element and collide with other elements. An example is a heat sink that has no electrical connections to the pcb. These can be defined in the mechanical layer of the pcb layout.

Link to 3d models and symbols. Each pcb footprint has a corresponding schematic symbol and may require a 3d model (usually a step file). This enables you to visualize the board in 3d and enables 3d clearance checking between components.

Many designers have a proven set of pcb libraries for building layouts, or services that can be built with packages. In many cases, customers send libraries with some pre-made pcb footprints to house proprietary components or cots parts. Sometimes you might be using a library from a reference design. 

Even though these designs are from a major manufacturer, it's quite common for them to have an incorrect footprint. Regardless, it's important to go through the basic pcb footprint checklist to make sure your footprint matches the actual components that will be placed on the board during pcb assembly.

PCB

My pcb footprint list

When we receive a new library from a customer, we go through the components to make sure the packaging is correct. The pcb placeholder checklist I've shown below is a good place to start validating the placeholder. After coming up with some datasheets, here are some things I've been hoping to check in the component data for before starting the pcb layout.

mpn/footprint matching

Some components come in multiple packages, and there will be a specific ** at the end of the mpn to specify a specific package. You should check that the packaging in the package matches the manufacturer's packaging specified in the part number.

Basic footprint matching

This is used to quickly catch incorrect footprints on components. For example, ferrites, couplers, and many other components do not have standardized packages, so it is easy to quickly spot package mismatches.

 Dimensions In this check, you don't need to go crazy, just use cad tools to check the basic pad size, pad spacing, and outline. If the dimensions do not match, it is often possible to detect incorrect components. For standardized SMD passives, this will help you determine if the wrong package is set in the package (eg 0603 vs 0402).

Reference and 1 pin code. Here you can visually check if these elements are in the pcb footprint.

Lifecycle and revision status

 Most designers don't check these points. They only include components found from distributors. For repeat production, avoid nrnd, obsolete, or end-of-life (eol) components entirely. Also, make sure the component footprint matches the latest version from the manufacturer.

Once the pcb layout is complete and ready for signoff, the dfm checklist should be traversed to address any outstanding manufacturability issues. Going through these checklists takes extra time on the front end, but this small investment can help you prevent manufacturing failures (and unhappy customers) on the back end.

What to Include in a PCB Footprint Checklist

The pcb footprint shows where components need to be placed in the pcb layout, and they become part of the production file that is sent to the manufacturer once you start production. Since part of your footprint becomes part of the stencil used for resist printing and etching, they must be very precise, right down to the solder mask footprint and pad spacing.

What's included in the pcb size checklist is more important than the location of the pads on the component. Courtyard areas, component designators, and more are coded in your component model, and once you've placed the footprints, they'll show up directly on the pcb layout.

 If the footprint isn't right, you might go through part of the manufacturing process before someone notices a problem with your board. Don't be caught off guard by an incorrect footprint, use our pcb footprint checklist to help you avoid problems and build a smooth design workflow.

pcb packaging problem

Every component that appears on the board layout will have a pcb footprint. Whenever you start a new project and jump into a layout, the schematic symbols and pcb footprint must be correct before creating a single design file.

In my experience, pcb footprints are more prone to some sort of problem than schematic symbols. This is why you should develop a pcb footprint inventory and process for validating component pcb footprints.

The footprint of each pcb will contain the following elements:

Location of pads or holes: This shows the location of the mounting pads (for smd components) or mounting holes (through hole components). These locations are used for welding and must be designed accurately.

Courtyard and profile: This is like a reserved area in your pcb footprint, i.e. no other components can be placed in the pcb footprint courtyard.

Reference code: This alphanumeric** provides a unique identification symbol for a component in schematics and pcb layouts.

pin-1 code name. Some elements may have arbitrary orientations (eg qfp and dip elements). Pin 1 indicates the correct orientation for the assembler.

Mechanical: Some elements may have mechanical elements or overhangs that may extend over the element and collide with other elements. An example is a heat sink that has no electrical connections to the pcb. These can be defined in the mechanical layer of the pcb layout.

Conclusion

Circuit board design has traditionally been a very time-consuming and difficult process due to the wide variety of product configurations and standards. However, by following the tips and tricks in this blog on PCB footprints and symbols, users can avoid footprint errors and design smarter increases.

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