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I have downloaded symbols, footprints and 3D models from DigiKey's website for all the components used in my PCB. Now I am double-checking the footprints with what the datasheets are specifying but I am seeing differences.

An example is for the USBLC6-2P6's SOT666 format. This blog post explains the differences I saw: https://www.atomic14.com/2026/03/15/is-sot666-standard It was simple enough to fix by re-doing the footprint manually.

Revisiting other components on the PCB reveals more differences. For example, I downloaded the symbol, footprint and 3D model for a GRM32ER71E226KE15L capacitor. The footprint actually comes from SnapMagic. Here's what the footprint looks like in KiCad (10.0.0). Note that I added dimensions for reference: GRM32ER71E226KE15L's footprint from SnapMagic

Now if I look at the datasheet, I see two different diagrams. The first one from page 4: datasheet page 4 and the second one from page 25: datasheet page 25 Below the last diagram there is "Table 2 Reflow Soldering Method" where we can see the info for the GRM32 series: enter image description here enter image description here

The footprint I have in KiCad (from SnapMagic) doesn't seem to match the datasheet's... And the two diagrams in the datasheet doesn't even seem to match together! For example the width c is different (2.9mm vs 1.8-2.3mm).

So my question is, is the SnapMagic footprint I have in KiCad sufficient or should I follow more closely the datasheet? And in that case, which dimensions should I use?

Edit:

  • I plan to have the PCB printed and assembled for me (for example by PCBWay).
  • I created a footprint from the datahseet, it looks like this: from datasheet
  • Here's what it looks like in 3D: 3D. The upper left is using the SnapMagic footprint, the bottom right uses the measurements from the datasheet.
  • I superimposed the datasheet pads (light red/pink) over the SnapMagic footprint superimposed. The datasheet's measurements are definitely smaller than the SnapMagic's ones.
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  • \$\begingroup\$ How do you solder the components? Especially for hand soldering your footprint doesn't provide much space for the iron. \$\endgroup\$ Commented Apr 4 at 15:45
  • \$\begingroup\$ The PCB is meant to be assembled by PCBWay (or an equivalent). I'm not planing to solder this by hand. \$\endgroup\$ Commented Apr 4 at 15:52
  • \$\begingroup\$ 3D image: If you want to compare footprints you have to make sure not to connect components directly to copper planes. \$\endgroup\$ Commented Apr 4 at 16:03

2 Answers 2

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The two diagrams in the datasheet have different purposes. The second one is what they recommend to be used and shows a range of optimal values.

The first table is not a recommendation, but shows what they used to test durability and mechanical stability - for sure they made the pads larger to get better results.

Your footprint is wider than the recommendation, and has more copper underneath the component. The width might make the component moving a bit more during reflow soldering. The smaller length makes this footprint a bit difficult to work with using a manual soldering iron.

In general one should try to stick closely to the recommendation of the component manufacturer. Your PCB assembly company might also have recommendations for the dimensions they get the best results with. And third, for many generic component sizes there are defined footprints in an ISO standard.

Nevertheless, it's very unlikely that any of the footprints will result in any serious problems. Only if you go for large scale production it's worth to have a closer look into the footprints of these simple components (as opposed to fine-pitch components or connectors which can very well completely fail using the wrong footprint).

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I would go with the manufacturer's recommendation and check it against JEDEC recommendations. Using a footprint from unknown sources needs to be vetted to be sure the footprints are acceptable. I also use LP Viewer, but I'm not sure if it is maintained.

The height of the part dictates the footprint dimensions so you get a proper solder fillet (toe). A generic library may not take this into consideration.

IPC-7351 has information on proper zero degree orientation of the part in the library. Adhering to this means the operator of the pick & place machine doesn't need to waste time with non-standard zero degree orientations.

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