How to Make Design Easier With Eagle CAD

Eagle is a PCB CAD program by Autodesk; it is one of the many popular PCB design tools and is a great tool for beginners.

Eagle has both a free version intended for use by hobbyists and a more capable paid version for professionals.

The free version has a limitation of the number of layers and maximum board size.

This article will cover the techniques needed to make your PCB design process simpler while using Eagle CAD.

1、Main Challenges While Designing PCBs

1.1 Component Placement
Component Placement is an essential part of any PCB Layout. Good placement on design leads to low noise, easier routing, and also better board assembly and cuts down on time taken.

It is essential to place devices such as decoupling capacitors properly. Improper placement may cause signal integrity issues, and the design may not work as intended.

1.2 Routing
Routing traces is one of the most time consuming and mentally demanding tasks.

Routing ease is dependant on the type of components one uses, the size of the board, and component placement.

With correct component placement, routing becomes much easier.

In some cases of very high-density boards, the board may not be possible to route completely in case of improper component placement.

Image 1: PCB with a large number of traces

1.3 Thermal Management
In cases of medium and high power boards, the components may produce a good amount of heat.

Some of the common heat-producing components are Mosfets, linear regulators, resistors, and transformers.

While designing a PCB, it is important to place sensitive circuitry away from heat-producing components.

Components such as electrolytic capacitors can fail if subjected to too much heat.

1.4 Board Layer Stack
When using a multi-layer design, there can be many different options for the layer stack.

Choosing the right one is important and is essential for good signal integrity.

A detailed guide about the layer stack for Eagle CAD can found here:

https://www.autodesk.com/products/eagle/blog/getting-layer-stack-right-first-time/

2.1 Schematic Guidelines
To make everything more organized and easy to read, the following guidelines should follow.

1. Eagle supports multiple schematic files for a single project. It means you can put separate circuit sections into different schematic files for better organization.

2. Adding relevant text and drawing boxed sections for each subcircuit. It helps reduce the chances of any confusion and also allows a third party to do a review easily.

Image 2: A typical Schematic View

2.2 Grouping Subcircuit Blocks
Eagle CAD has an option to create groups and make objects move as a group. It enables a user to group all subcircuits in a project and add them to a group.

While placing components during the PCB layout stage, Select the group to move all objects simultaneously and place them together.

It makes placement and routing easier.

2.3 Subcircuit Placement
While placing subcircuits, a group should be created out of the components.

Then arrange those components in a way such that.

1. They occupy the least amount of area on a board

2. Placement is such that all traces are short and straight.

3. Avoid changing layers during routing and minimize vias.

2.4 Routing Guidelines
Since routing is the most time consuming and demanding task, it needs to be done efficiently.

Follow the rules below while routing:

1. Traces between components need to be as short as possible.

2. Avoid using vias wherever possible.

3. Run Traces on multiple layers perpendicular to each other. If your bottom layer traces run left to right, then the top layer should ideally run top to bottom.

4. There is a solid ground plane either over or under any signal layers with controlled Impedance traces.

Eagle doesn't have an impedance calculator built-in, so you need to use a 3rd party tool. After calculating parameters, Rules can be set up along with net classes for controlled impedance traces.

3、Advanced Guidelines and Features

3.1 Design Rules
Eagle allows users to set up specific design rules. It helps make sure that all features on a PCB are manufacturable and to the specification.

Design rules usually contain the following definitions:

1. Trace widths and clearances

2. Via diameters and hole sizes

3. Component and silkscreen clearances

4. Specific settings for differential pair impedance controlled traces.

Setting up these rules can take some time but saves a lot of design time, especially on large boards.

3.2 Layer Sets
A powerful tool in Eagle is the ability to group and show or hide specific layers. It makes routing much easier as only the relevant signal layers can be enabled and everything else hidden.

This process is also especially useful when doing finishing touches like adding silkscreen art and logos.

The link below gives detailed information on all layers available and their functions in Eagle.

3.3 Design Rule Checker
One of the last steps that every PCB has to go through before finishing the design phase is design rule check or DRC.

The design rule checker in Eagle checks all features on the board and highlights any issues it comes across.

The most important things that a DRC will check are the following:

1. Short Circuits

2. Unconnected Traces

3. Component Clearances

The video below explains in detail how to use the Eagle design rule checker.

https://www.youtube.com/watch?v=FJeAfN_vBYo

4、Making the Design Process Faster

4.1 Block Diagrams
It is one of the primary processes which skipped. Before making the actual schematic, a block diagram in one schematic sheet that explains the circuit's basic functionality must be present.

Eagle allows users to do this by using the drawing tools to make blocks and add text.
A block diagram of design is especially important if the design will be reviewed or worked on by another person.

4.2 Autorouting
Eagle contains an Autorouter. An Autorouter will automatically draw and route traces according to the specified rules. While an Autorouter isn't the best thing to use in complex designs, it works well with simple boards. Boards that have few components are one use case of an Autorouter.

Autorouting saves a lot of time and is a good option for beginners who want simple boards.
Another tip is to autoroute a small section of the board, which has straightforward connections.

Image 3: Eagle CAD

4.3 Auto fanout of high pin count packages
Certain packages like BGAs can be hard to route or "fanout."

Eagle contains specific tools for fanning out BGA pads. One of them is the BGA autoroute.

With the correct design rule setup, the BGA Autorouter can save a large amount of time. It is very helpful in large designs with lots of high pin count packages.

Image 4: A footprint for a BGA Package

Advanced Board Features
OurPCB offers boards from simple two-layer to much more complex multi-layer boards.

OurPCB is also capable of trace and line widths down to 3mils and impedance control and rigid-flex boards.

We also have an expedited service where your board will manufacture within 24- 48 Hours.

For full technical capabilities, please visit https://www.ourpcb.com/capabilities.

High-Resolution Silk Screen
OurPCB also offers to manufacture panels containing multiple PCBs, the customer can provide their panel design, and we manufacture. It is perfect for high quantity boards.

Online Quotation System
Finally, OurPCB also has an online quotation system that automatically calculates the price of your PCB after you upload your Gerber files and input the required data.

You can export your Gerber files from Eagle straight onto OurPCB for an instant quote.

It results in a very fast order generation time and causes your board to manufactured in the shortest possible time.

Image 5: High-Resolution Silk Screen

6、Conclusion

Eagle CAD is a great tool for designing PCBs. It’s good for both beginners as well as professionals.

Eagle contains lots of features that help make the design process easier and faster.

OurPCB supports Gerber files exported directly from Eagle and can help you transform your design into a real working board.