Six things to consider when transferring PCB schematic diagram to PCB layout
design. All the examples mentioned are developed in Multisim design environment, but the same concept is applicable when using different EDA tools!
In the process of transferring schematic diagram to layout environment through netlist file, device information, netlist, layout information and initial routing width setting are also transmitted.
Here are some recommended steps for the layout design phase:
1. Set the grid and units to appropriate values. In order to achieve more precise layout control of components and wiring, device grid, copper grid, via grid and SMD grid can be designed as 1mil.
2. Set the blank area and vias in the outer frame of the circuit board to the required values. PCB manufacturers
may have specific minimum or nominal recommended values for blind and buried hole settings.
3. Set corresponding pad / via parameters according to PCB manufacturer's capability. Most PCB manufacturers can support smaller vias with a hole diameter of 10mil and a pad diameter of 20MIL.
4. Set design rules according to requirements.
5. Set custom shortcut keys for common layers to quickly switch layers (and create vias) when routing.
Handling errors in schematic transfer
A common mistake in the process of schematic diagram transfer is that there is no or incorrect package assignment. It should be noted that:
If an electronic component in the schematic diagram is not encapsulated, an alarm message will pop up indicating that the virtual electronic component cannot be exported. In this case, no default package information will be passed to the layout, and the electronic components will be simply deleted from the layout.
If the package is passed, but the valid package shape cannot be matched correctly, an alarm message indicating mismatch will also be generated during the transmission.
Correct the package assignment in the schematic or create a valid package for any electronic component. After correction, perform the forward annotation step to update and synchronize the design information.
Update design with annotations
Annotation is the process of transferring design changes from schematic to layout or from layout to schematic. Backward labeling (layout to schematic) and forward labeling (schematic to layout) are the key to keep the design accurate.
In order to protect the completed work, it is necessary to back up and archive the current version of schematic and layout files before any important forward or backward labeling steps.
Do not attempt to make changes in both schematic and layout. Make changes to only one part of the design (either schematic or layout), and then perform the correct tagging steps to synchronize the design data.
Renumber electronic components
Electronic component renumbering is a function of renumbering electronic components on PCB in a specific order. The reference labels should be sorted from top to bottom and from left to right on the PCB. This makes it easier to locate the electronic components on the board during assembly, testing and error checking.
Dealing with last-minute electronic components or netlist changes
It is not advisable to change PCB components or netlist at the last moment, but sometimes it has to be done because of usability problems of electronic components or detection of last-minute design errors. If you need to change an electronic component or a netlist, you should do it in the schematic diagram, and then mark it to the layout tool by forward annotation.
Positioning electronic components by highlighting selection
During PCB layout, one way to browse specific electronic components or wiring in schematic diagram is to use the "highlight selection" function. This function allows you to select an electronic component or a routing (or multiple objects), and then view their position in the schematic diagram.
This function is particularly useful for matching bypass capacitors and their corresponding IC connections. In turn, you can also locate specific electronic components or wiring in the layout while browsing the schematic diagram.