0402 footprint for inductor


#1

Newbie question

Is the 0402 footprint which is in the Kicad library, is it based on inch or mm?

For an inductor with a 0402 inch footprint should I use a capacitor footprint or resistor footprint - in Kicad there are two separate 0402 footprints one for capacitor which is larger vs resistor which is smaller


#2

If you look at the footprint in the editor, you will see that the properties dimensions are metric.

You may want to increase the courtyard around smd inductors to avoid side by side parts coupling, they are not shielded.

edit
Here is a link on mutual coupling of chip inductors:
http://dkc1.digikey.com/ch/it/tod/JohansonTechnology/couplingeffects/couplingeffects.html


#3

Many thanks for the reply, the capacitors are listed with Inch codes in the library but inside- the pad size of 0402 capacitor in the library is 0.6mmx0.5mm which matches with 1005 size metric code.

Thanks for the link about inductor coupling, it was informative.

I will create an inductor footprint separately as per the manufacturer datasheet as it is easier than searching the right footprint in the capacitor list.


#4

Good choice.

Name it after manufacturer and inductor family.

Lots of problems avoided.


#5

No one seems to follow any particular scheme to discriminate between imperial and metric codes, but many use a convention where a metric code has “M” at the end and no M means imperial. But since the practice varies, you always need to check yourself.


#6

Standards are sometimes hard to find. The recommended naming convention for surface mount devices (SMD) is specified in IPC-7351.

  1. Open the IPC-7351 file.
  2. Use the find function to search for RLC or other device name. There may be more than one, is a big doc.
  3. Construct the suggested naming convention for your device.
  4. Open Footprint Editor.
  5. New footprint.
  6. Draw the component landing pattern according to the datasheet/drawing.
  7. Save footprint in active library / or / Create new library and save current footprint.
    This will make a .pretty folder to save kicad_mod files, the footprints.

That should keep your library organized and standardized for use in ISO/ASME/IEEE convention.

An old footprint example of IPC-7351 for KiCad can be found on github here ipc-7351.mod.

Hope that helps anyone else with a question about SMD Inductor footprints and how to compose and name them. I also hope we will see this convention implemented in future commits of the kicad github .pretty’s.


#7

You might like to take a quick look at QEDA (https://github.com/qeda/qeda). This is a node.js library that will produce internally consistent and matching .lib, dcm pairs, a 3d model (box only .wrl at present) AND a IPC7351 compliant footprint (correctly named), all from a basic .yaml component template. It is quite a simple to install and under active development. You can adjust various settings for a consistent house ‘style’ e.g. extra extension for hand soldering, round rectangle pads etc.

For instance, the 0402 inductor (included in the extensive standard library) is defined as follows in a l0402.yaml file

name: L0402
description: Chip inductor 1x0.5 mm
keywords: Inductor

schematic:
  symbol: inductor

housing:
  pattern: chip
  bodyLength: 0.95-1.05
  bodyWidth: 0.45-0.55
  height: 0.45-0.55
  leadLength: 0.15-0.35

You can adjust any of the parameters according to the spec from the manufacturer, set any house parameters (individually per component, or as a ‘house style’) and generate your custom component lib, dcm, 3dshape and kicad_mod.


#8

Thanks for clarifying my response and setting focus on the ops question of 0402.

I’ll take a look at the QEDA git, “automating” any of the process will be helpful.


#9

look into the datasheet for recommended footprint of the inductor you plan to use.