Six tips for passing PCB schematics to layout design

PCB Best Design Method: Six things to consider when passing a PCB schematic to a layout design. All of the examples mentioned in this article were developed using the Multisim design environment, but the same concepts apply when using different EDA tools.

Initial schematic transfer

The device information, netlist, layout information, and initial trace width settings are also passed during the pass of the schematic to the layout environment through the netlist file.

Here are some recommended steps for the layout phase:

1. Set the grid and units to the appropriate values. For finer layout control of components and traces, the device grid, copper grid, via grid, and SMD grid can be designed to be 1 mil.

2. Set the blank area and vias of the board outline to the required values. PCB manufacturers may have specific minimum or nominal recommendations for blind and buried via settings.

3. Set the appropriate pad/via parameters according to the PCB manufacturer's capabilities. Most PCB manufacturers can support smaller vias with a hole diameter of 10 mils and a pad diameter of 20 mils.

4. Set the design rules as required.

5. Set custom shortcuts for common layers to quickly switch layers (and create vias) when routing.

Handling errors during schematic transfer

One common mistake in schematic delivery is the absence or incorrect packaging assignment. have to be aware of is:

● If a device in the schematic is not encapsulated, an alarm message will pop up indicating that the virtual component cannot be exported. In this case, no default package information is passed to the layout and the component is simply removed from the layout.

● If the package is passed, but the valid package shape is not matched correctly, an alert message indicating mismatch will also be generated during the transfer.

● Correct the package assignment in the schematic or create a valid package for any device. Correct the process and then perform the forward labeling step to update and synchronize the design information.

Update design by annotation

Annotation is the process of passing design changes from a schematic to a layout or from a layout to a schematic. Backward labeling (layout to schematic) and forward labeling (schematic to layout) are key to maintaining accurate design.

In order to protect the work that has already been done, it is necessary to back up and archive the current version of the schematic and layout files before any important forward or reverse labeling steps.

Do not attempt to make changes in both the schematic and the layout. Make changes to only one part of the design (either a schematic or a layout) and then perform the correct annotation steps to synchronize the design data.

Renumber the device

Device renumbering is a function of renumbering components on a PCB in a specific order. The reference numbers should be sorted from top to bottom and left to right on the top of the PCB. This makes it easier to position the device on the board during assembly, testing, and troubleshooting.

Handling last minute device or netlist changes

Last-minute PCB device or netlist changes are not advisable, but sometimes they have to be due to device usability issues or detection of last-minute design errors. If you need to change the component or netlist, you should do it in the schematic and then mark it in the forward direction to the layout tool. Here are some tips:

1. If adding a new device after the layout design begins (such as adding a pull-up resistor to the open-drain output), add resistors and networking to the design from the schematic. After being forward-labeled, the resistor will appear as an unlayout component outside the board's outer frame, and a flying lead will indicate the connection to the network. Next move the components into the board's outer frame and route them normally.

2. Backward labels and reference label changes work well together, such as renumbering the back layout.

Selecting the positioning device by highlighting

One way to view specific components or traces in a schematic during PCB layout is to use the 'highlight selection' feature. This feature allows you to select a component or a trace (or multiple objects) and then view their position in the schematic.

This feature is especially useful when matching bypass capacitors and their corresponding IC connections. Conversely, you can also locate specific components or traces in the layout while browsing the schematic.