Where should I be looking for custom footprints in KiCad?

For custom components, you relly need to look outside of KiCad's default libraries. The best bet is usually starting with the manufacturer's own website or a large distributor's resource area. Many component makers host libraries that contain accurate symbols, footprints, and even 3D models for thier specific parts. If you can find that library from the source, you've got the most accurate dimensions posible. And if they don't have a library, using a major component search site like Octopart or ComponentSearchEngine is a good start, as they often aggregate this component metadata. When you're dealing with a chip that isn't widely documented, you often have to go the manual route. You need the component's official datasheet becuase that is the only place that lists the precise physical dimensions of the package. If KiCad doesn't have a ready-made footprint, you must draw it yourself based on that datasheet. Just make absolutely certain the footprint matches the datasheet dimensions, especally for connectors or headers that aren't standard rectangular shapes. It's easy to eyeball it wrong, and that leads to huge layout errors later.

There are also specific tools and community resources that help automate some of this. For example, if you are ordering through some specific PCB fabrication houses, they might have import tools for certain component databases. Sometimes finding a Python script or a small utility can help convert component data from one system into a format that KiCad can read. It really depends on what specific part you are dealing with, but tracking down the manufacturer's resource page is almost always the most reliable method to get clean data for complex packages.

Look, I remember when we were just drawing everything on graph paper before KiCad even came along. You can find a lot of these parts in shared community repositories, but you always have to treat those footprint libraries with suspicion. A quick manual check against the datasheet is always wise because some of those shared files are based on old specs that don't match newer hardware. What exactly is the package type for the IC you're struggling with?

Actually, when you are manually tracing those package dimensions from a specification sheet, I find people often focus solely on the main body outline and completley ignore the neccessary keep-out areas and the thermal pad footprints associated with larger chips. It is fundamentally important to account for the component's surrounding physical requirements, not just its primary bounding box, because that omission is what leads to signal crosstalk or even thermal throttling on the final PCB.

For example, when I dealt with a particlar high-power switching component, the official library simply lacked the thermal relief details, so I had to verify the copper connectivity specifications directly from the manufacturer's application note. This precise detail is far more critical than getting the exact center-to-center pin pitch, which is usually straightforward to find anyway, so I suspect the package footprint itself is often less of a concern than the surrounding copper management.

I am trying to draw the footprint myself because the pre-made libraries are too generic for my special parts. Looking at the datasheet, I can see the pins and the shape of the chip, but it is really hard to know where exactly the metal pads should sit versus the empty space around the plastic body. It is tricky figuring out which lines on the page translate into actual traces on the board. Do you have any tips for picking the right measurements when you are drawing it all by hand?

Quick update — I was looking at the datasheets and realized I was only measuring the body outline. I needed to pay more attention to those keep-out zones you mentioned for the thermal pad. It’s making the tracing process a lot more complicated than I thought it would be.