Six things to consider when passing a PCB schematic to layout. All the examples mentioned were developed with the Multisim design environment, but the same concepts apply when using different EDA tools.
Initial schematic transfer

Device information, meshes, layout information, and initial wire-width Settings are also transferred during the transfer of the schematic to the layout environment via the netlist file.

Here are some recommended steps to prepare for the layout stage:

1. Set grids and units to appropriate values. The device grid, copper-coated grid, through-hole grid and SMD grid can be designed as 1mil to achieve finer layout control of components and wiring.

2. Set the blank area and through hole of the circuit board outer frame to the required value. PCB manufacturers may have specific minimum or nominal recommended values for blind and buried hole Settings.

3. Set the corresponding pad/through-hole parameters according to the PCB manufacturer’s ability. Most PCB manufacturers can support smaller holes with drill hole diameter of 10mil and pad diameter of 20mil.

4. Set design rules according to requirements.

5. Set custom shortcuts for common layers to quickly switch between layers (and create through holes) while wiring.

Handle errors in schematic transfer

In the process of schematic diagram transfer, a common error is the absence or incorrect packaging assignment. Note:

If one of the devices 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 wrapping information is passed to the layout, and the component is simply removed from the layout.

If the wrapper passes, but does not correctly match a valid wrapper shape, an alarm message indicating a mismatch is also generated during delivery.

Correct package allocation in schematic diagram, or create a valid package for any device. After the correction, perform the forward annotation step to update and synchronize the design information.

Update the 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.

To protect the work that has been done, backup and archive the current version schematic and layout files before any significant forward or reverse annotation steps.

Don’t try to make changes in both schematic and layout at the same time. Make changes to only one part of the design (either schematic or 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 label should be sorted from top to bottom, left to right, on the PCB. This makes it easier to locate devices on the board during assembly, testing, and error checking.

Handle last-minute device or netlist changes

Last minute PCB or network table changes are not desirable, but are sometimes necessary because of device availability problems or last minute design errors detected. If you need to change a component or netlist, do so in the schematic diagram and then by pointing it forward to the layout tool.

Here are some tips:

1. If a new device is added after the layout design (such as a pull-up resistor on the leakage output), then add resistance and network to the design from the schematic diagram. After positive marking, the resistor will be displayed as an unlaid element on the outside of the circuit board frame, and the flywire indicates the connection network. Next move the element to the circuit board outer frame and do the normal wiring.

2. Backward labeling and reference label changes can work well together, such as post layout renumbering.

Positioning devices are selected by highlighting

One way to navigate through specific components or wiring in the schematic during PCB layout is to use the ‘highlight selection’ function. This feature allows you to select a component or line (or objects) and see where they are in the schematic.

This feature is especially useful when matching bypass capacitors and their corresponding IC connections. In turn, you can position specific elements or lines in the layout as you navigate through the schematic.