Component Creation

Good Circuit Boards require good land patterns and good schematics require good components.

4. Attach a Pattern

Now that you have your component drawn, and your pins labeled, it's time to attach a pattern to your part.

You should take the components that you just made and the patterns you made last week, and connect the component pins to the pattern pads.

Pin To Pad

Image of the ATSAMD11 schematic component and land pattern drawing

Once you figure out one component, you'll figure out the rest rather quickly.  Be sure to check the documentation for your EDA for specific instructions.

Possible Pitfalls

A problem occurs with off-board connectors (USB, Battery, etc...) in that the part, and the connector housing, often have pads with no electrical connection.   It's also possible to find pads that are connected to other pads on the same net

For example, our custom battery connector has two separate pads connected to Vdd, two separate pads Connected to ground, and two separate pads that are used as mechanical anchors.  How you deal with that will depend partly on your EDA software, and partly on personal preference.  But one way or another, you need to ensure that the power pins are connected to the rest of your circuit.

Part with multiple Pads

This image from Diptrace is one example of how to assign pad numbers to a pattern.

EDA Software Requirements

Your EDA software likely won't want you to give two pads identical numbers.  Diptrace, for example, requires users to add the "@" symbol on duplicated pads.  You'll have to investigate how to assign duplicate pads in your EDA software.

DipTrace Duplicate Pads

This image from DipTrace Pattern Editor shows the numbering scheme addition of "@" to a second pad

Other Design Options

Pads that will be attached to the same net will have to be connected during the layout process.  You can run traces between the pads now -- or a copper pour.  That leaves you with a single large pad that will be linked to your component outline.  

But if you do that, be sure to use LPI solder mask to limit the solder movement during the reflow process.  If you leave the copper exposed, the solder will wick along the copper trace and spread out from the pad, leaving you with a weak joint.

 

Hard Way HughesOf all the options, I like this last one the best.  But I don't know how well it will work in other EDA programs.