BoardSurfers: PCB Electronics - Component Placement - Get Set and Go!

You have prepared your design for placement; the design environment and technology processes are set, the padstacks and package symbols are ready, the board outline is there, the layer stackup is defined, and the netlist is in, as we discussed in our earlier post on preparing for placement. Now is the time to start placing components on the board. You are already on your mark if you have done the preparation tasks. Now's the time to get set and go!

Get Set

 As a good practice cross-check if the following are available:

• Symbols: The package symbols and padstacks required for parts in the netlist must exist.
• Netlist: A schematic netlist must be loaded into the PCB Editor design file.
• Alternate Package Symbols: These are required if alternate footprint symbols are to be used during placement.
• Floorplanning (optional): Rooms can be specified for part placement.
• Package Keepouts (optional): Package keepouts should be added prior to component placement. 

Let PCB Editor know where the pads and symbols are by setting the paths for library pads and library symbols in the User Preferences dialog. PCB Editor will use these paths to search for symbols and pads as you go along placing the components.

Go!

How do you want to place your components today? It's almost like that for PCB Editor placement. You have choices, one for every occasion. 

First thing you will like to do is get into the Placement Edit application mode. Like the other intuitive application modes in PC Editor, in the Placement Edit application mode simply select a relevant object on the canvas and choose the appropriate action from the right-click pop-up menu. 

Do you want to place the components manually? You can do that of course. Select components individually or by groups, and interactively determine their locations. You can place parts by reference designator, class (say IC, IO, or DISCRETE), room, or net group. You can also place mechanical symbols (such as board outlines) or format symbols (assembly and fabrication drawings). What's more, while placing the components you can rotate or mirror them, say, to place parts on the bottom layer instead of the default top (you can also change the default, of course). 

And, yes, PCB Editor can place elements automatically based on controls that you specify before activating automatic placement. You choose the elements to be placed and define an area in which to place them. You can specify additional placement controls by defining placement parameters, and properties assigned to functions and elements. For example, you can use Quickplace, which will automatically place parts outside the board outline or inside their designated rooms. You can then move the parts interactively to their final locations.

Here are a few tips to make placement a piece of cake for you (PCB Editor really spoils with choices):

• Dynamic Alignment: Align components during movement using the dynamic component alignment guidelines. These guidelines can be configured for either component origins, place-bound edges, or both.
• Ratsnest Display: Identify congested areas and evaluate flow within and between functional blocks of logic by displaying ratsnests, which are lines displayed between the pins of an unconnected net. They show the relationship between pins having the same net name.
• DFA Constraint SPreadsheet: Get real-time feedback on minimum clearance requirements based on the package’s side-to-side, end-to-end, side-to-end, or end-to-side profiles using real-time package-to-package clearance checking during interactive component placement.
• Circuit Replicate: Replicate and resue designs and circuits to increase productivity.

At the Finish Line: Check Your Board Using 3D Canvas

You have placed the components but is it all good? How will it look and behave when it is manufactured? It's time to open the design and verify it in 3D Canvas. Allegro® 3D Canvas lets you visualize and analyze a three-dimensional model of a design as a manufactured output. You can visually check the symbol placement, position, and proximity to other symbols. 3D Canvas also lets you view mechanical objects such as shields, fans, heat sinks, and housings, and run checks for verifying collisions or other placement issues.

Allegro 3D Canvas displays in its own canvas, letting you continue to work with the two-dimensional view in the main canvas. You can interactively zoom, pan, and rotate the 3D design.
Enabling the interactivity between the 2D design window and the 3D canvas lets you edit the design in the 2D design window and display the changes in 3D Canvas in real-time.

Conclusion

After you have placed the components, you will start with setting electrical, physical, and spacing constraints and the actual routing of the board. But before doing that if you think trying out the different features we discussed in this post, will give you more insight, click here to try a Rapid Adoption Kit on Placement and Shapes. This Rapid Action kit provides an overview of different component placement techniques and copper areas (shapes) in Allegro PCB Editor with a test database for you try out the steps.

Note: The above link can only be accessed by Cadence customers who have a valid login ID for https://support.cadence.com