Designing Your PCB

Placing Components

It is best to place all the components on the top side of the board.  This makes the boards easier to handle when they are assembled.

External Components

If you have components that need to interface with external cases or objects, you will want to add them first as this will determine the spacing for other items.  These types of components might include switches or LED's that will appear through a case.  Of course there are a number of other items that you might consider such as heat sinks, mounting holes, connectors, etc...

Component Proximity

If two components are going to be connected, you generally want them to be placed close to each other.  This reduces the amount of tracing and imporves the qulity of the board.

Be sure to consider the impedance for the distance of the trace and the thickness of the board.  Our consultant can help you if you have questions or need assistance.

Orientation

Integrated Circuits and Polarized parts should have the same orientation.  This means that they should all run up and down or left to right.  You want to place Pin 1 for IC parts or the positive lead for polarized parts in the same position for every component.  This helps with testing and debugging.

Spacing for Traces

When designing your board, make sure to leave enough room between components for traces.  Especially for IC's.  The minimum for IC's is about .4".

Trying Your Design

The simplest way to try out your design is to make a print out and then physically place your components on the paper. If every part can rest on the paper without touching, you are 90% on your way.

Getting Power to the Components

The main power and ground traces are larger than normal.  You don't want a lot of turns in the power traces and all the parts should be fed in parallel, not daisy chained.

Traces

A plated hole can be used to move signals from one layer of the board to another.  These are called vias.

For simplicity and ease of testing (as well has improving quality) try to run vertial traces on one side of the board and vertical ones on the other.  Trace width for low current digital and analog signals is 0.010".

The trace width formulas are:
I = 0.0150 x dT 0.5453 x A0.7349 for internal traces
I = 0.0647 x dT0.4281 x A0.6732 for external traces
where:
I = maximum current in Amps
dT = temperature rise above ambient in ┬░C
A = cross-sectional area in mils2;

You can use an online calculator here: Printed Circuit Board Trace Widths Calculator.

Pre-Production Engineering Consulting

We have deep resources that can help answer any questions that you may have concerning your design or the process.  Contact us at (713) 666-1976 to speak with a consultant.

Help from Electro Circuits

Electro Circuits is ready to help you make your design a realiable blueprint for manufacturing.  Our experts know all the common and the not-so-common issues with board design and are ready to help.  We are happy to discuss your project while you are in the design phase to provide you with guidance on best practices.

Call today: (713) 666-1976

 

  
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