Best Practices in PCB Design: Routing
With the integrated capture, simulation and layout environment of the National Instruments Circuit Design Suite, engineers have a complete PCB design and validation environment. With the integration with NI LabVIEW, measurements can be easily introduced into the design flow,with simulation results improved with real-world data (a concept called virtual prototyping), and the transfer of simulation data to the test environment to compare real vs. theoretical. In this series of Best Practices articles, National Instruments provide a number of new resources to show you how to use various features in NI Multisim and NI Ultiboard in the most advantageous way to save timeand maximize resources. Table of Contents 1. 2. 3. 4. 5. 6. 7. 8. Introduction Routing of Copper Traces Getting Started Method 1 Manual Trace Placement Method 2 Follow-Me Router Method 3 Connection Machine Method 4 Autorouter Best Practices: Maximizing the Use of Your Routing Methods
Introduction In this introductory article we will investigate the various techniques available for copper routingin NI Ultiboard, how to use them, and when to use them.
Routing of Copper Traces In Printed Circuit Board (PCB) design, there are three fundamental tasks that allow you to prepare a board for prototype and manufacture. First the board outline must be created for the form factor of the design. Second in consideration is part placement. In part placement various landpatterns (or footprints) ofdesign devices are configured on the board. Each placed part consists of pins which are terminals that need to be connected in order to complete the design. A PCB design tool represents the necessary connections between parts with a wire. These wires are called nets. Therefore the third fundamental task in board design is to route these net connections between various parts. The routing processturns these various net connections into copper traces which connect parts in the physical prototype with current carrying connections. The net acts as a design guide indicating that two pins must be connected, while the copper trace is the actual physical connection which will be made as a part of your PCB. NI Ultiboard allows you to define copper traces using a number of different methods. Eachmethod provides varying degrees of control that allow an engineer to balance precise copper definition with automated speeds in order to effectively design a PCB. The routing methods available to engineers are: 1. 2. 3. 4. Manual Trace Placement Follow-Me Router Connection Machine Autorouter
In this article we will investigate how and when to use each of these routing methods.
Getting StartedTo assist in the steps outlined in this article, we will use the attached example file to practice routing. 1. 2. 3. 4. 5. Download the attached 6880_Example_Design.ewprj file to your desktop. Select Start > All Programs > National Instruments > Circuit Design Suite 10.0 > Ultiboard to open Ultiboard. Select File > Open. Browse to the desktop where you saved 6880_Example_Design.ewprj. Click on theOpen button to view the file (as seen in Figure 1 below).
Figure 1: 6880_Example_Design.ewprj
Follow the next steps to ensure that your work area is correctly setup: 1. Notice that on the left side of the NI Ultiboard screen you have the Design Toolbox (if you cannot see this currently you can view it by selecting View > Design Toolbox). 2. On the bottom of the DesignToolbox select the Layers tab. Whenever you are placing copper routes in the work-area you must first select the layer upon which the route will be defined. In this example we will be using the Copper Top however any of the copper layers (Top, Bottom, Inner) can be selected in the Design Toolbox. 1. Double click on the Copper Top layer in the Layers tab (it will now be highlighted in red as seen...