The Best Methods of Calculations for Pad Size in PCB Design

December 27, 2017 Altium Designer

Young woman at home on couch watching television in suspense

 

 

 

In our family we have a phrase that we use to describe when a person is surprised, we call it a “Spielberg moment.” Think back to movies like Poltergeist, or Close Encounters, where the characters in the movie would stare with their mouths hanging open at something that was surprising, shocking, or horrifying. This is what I mean by Spielberg moment. The other day while teaching her third graders, my wife gave the kids a Spielberg moment when she used the word ‘amalgamation,’ in a sentence. Every mouth hung wide open until she quickly substituted the word ‘mish-mash,’ instead.

 

I feel like I have a Spielberg moment every week these days, with new technology and unbelievable news breaking so frequently. One of those times came to me when I first started designing printed circuit boards and was asked to create a new PCB footprint. Since I hadn’t done this before, I didn’t know where to look for the information that I needed or how to go about creating the part. With my mouth hanging wide open, I’m sure I could have been cast perfectly for any of those mouth-hanging moments.

 

While I’m sure we could talk about enough CAD library parts, specific footprint types, or land pattern sizes to leave any passerby with their mouths gaping, it’s important to know, first, resources you can turn to for information on how to build your PCB footprints. With the knowledge of available online data, as well as automated tools, you’ll be able to understand how to calculate pad sizes for your PCB with enough ease and comfort to keep your Jaws from completely hanging open.

Industry Standards for Calculating PCB Design Pad Sizes

PCB footprints are the CAD models of the physical parts on a printed circuit board. The layout of the circuit board will contain the footprints on it, which means that the footprints themselves need to be built first. Each footprint has one or more pads, or land patterns, where the leads of the part will be soldered to on the completed circuit board.

 

There are many resources out there that provide information on PCB footprints. You will be able to find footprint specifications from the part vendors for their components, and there are also standards offered by different groups within the printed circuit board industry. The IPC organization is one such group and it has many standards and other forms of data that will give you a wealth of knowledge. PCB manufacturers themselves often offer their recommended footprint specifications on their websites.

 

 

Picture of a calculator

You can find component footprint calculators online

 

 

 

 

Library Part Vendors and Calculators

Many years ago PCB designers had to create their footprints using information from data sheets along with general pad and land size formulas. This was error prone and not always consistent with current data for all PCB manufacturers. Fortunately, there is more error-free and productive options available to you these days.

 

One such option would be to register with a company that specializes in creating footprints for the specific CAD tools that you use. They have many years of experience doing this kind of work and can be very cost-effective in saving you the time needed for footprint research and development. Another option is to use a land pattern calculator. You can find these online and they will help you to create land patterns and footprints according to the latest available standards.

You May Have the Best Solution for Building Parts in Your CAD Tools Already

The best method of creating footprints that I have found is to use the part building functionality that comes with your PCB layout tools. Many CAD systems today come with a footprint building tool that does the heavy lifting of part creation for you. Some of these tools also come with industry standard specifications already pre-loaded.

 

With these footprint builders as part of your PCB layout tools, you can save yourself a lot of time that you used to spend on library creation. With the footprint specifications already loaded in the footprint builder, you can use it to build your parts according to the industry standards or make minor manual adjustments as needed. This will save you the time of having to research all of these specifications for yourself. The footprint builder also will create the parts for you with every pad and/or landing patterns, while adding necessary part outlines for silkscreen or assembly drawing shapes. This time your jaw might be dropping in wonder, not horror.

 

Picture of the IPC compliant footprint wizard within Altium Designer

Component footprint building tools within your CAD system are a tremendous help

 

 

Using the footprint building tools within your PCB layout tools is a tremendous benefit. It can save you a lot of time and effort building your library parts, and get you into the heart of your PCB design sooner with the confidence that you are using industry correct footprints.

 

PCB design software, like Altium Designer, has a footprint wizard with IPC standards pre-loaded into it. This will help you to create a library of PCB component footprints that are built according to the most current industry standard specifications.

 

Would you like to find out more about how Altium can help you in the creation of your PCB component footprints? Talk to an expert at Altium.

 

About the Author

Altium Designer

PCB Design Tools for Electronics Design and DFM. Information for EDA Leaders.

More Content by Altium Designer
Previous Article
Boats With The Current: Microstrip and Stripline Transmission Line Trade-offs
Boats With The Current: Microstrip and Stripline Transmission Line Trade-offs

Jay Gatsby might have lost quite a bit in his story; however, you don’t need to suffer through transmission...

Next Article
Old Wisdom: Best Schematic Software Simplifies Schematic to PCB Synchronizing
Old Wisdom: Best Schematic Software Simplifies Schematic to PCB Synchronizing

The best schematic software combines schematic capture and PCB layout in one unified design environment eas...

Get My Altium Designer Free Trial Today.

Get Free Trial