Initial schematic transfer
Device information, netlist, layout information, and initial trace width settings are also passed through the netlist file when passing the schematic to the layout environment.
Here are some recommended steps for the layout design phase:
1. Set the grid and units to the appropriate values. To achieve finer layout control for components and traces, the device grid, copper grid, via grid, and SMD grid can be designed to be 1mil.
2. Set the blank area of ??the circuit board and the vias to the required values. PCB manufacturers may have specific minimum or nominal recommended values ??for blind and buried hole settings.
3. Set the appropriate pad / via parameters based on PCB manufacturer's capabilities. Most PCB manufacturers are able to support smaller vias with 10 mil holes and 20 mil holes.
4. Set design rules on request.
5. Set custom shortcuts for common layers to quickly switch layers (and create vias) when routing.
Process schematic transmission error
One of the common pitfalls in schematic transfer is the absence of or incorrect package assignments. Have to be aware of is:
● If a device in the schematic is not encapsulated, an alarm message will be displayed indicating that the virtual component can not be exported. In this case, no default package information is passed to the layout, and the components are simply deleted from the layout.
● If the package passes but does not match the valid package shape, an alert message indicating mismatch may also be generated during delivery.
● Correct the package distribution in the schematic or create a valid package for any device. Correct and execute forward labeling steps to update and synchronize design information.
Update the design through annotations
Annotations are the process of passing design changes from the schematic to the layout or from the layout to the schematic. Backward dimensioning (layout to schematic) and forward labeling (schematic to layout) are the keys to maintaining design accuracy.
To protect the work that has been done, you need to back up and archive the current version schematics and layout files before any significant forward or reverse labeling steps.
Do not attempt to make simultaneous changes in schematics and layouts. Make changes to only one part of the design (either a schematic or a layout) and then perform the proper annotation steps to synchronize the design data.
Renumber the device
Device renumbering is the ability to renumber the components on the PCB in a specific order. The reference marks should be sorted from top to bottom on the PCB and from left to right. This makes it easier to position the device on the board during assembly, testing, and troubleshooting.
Handle last-minute changes to the device or netlist
Last-minute PCB device or netlist changes are not desirable, but sometimes have to do with device usability issues or the detection of last minute design errors. If you need to change the component or netlist, it should be done in the schematic and then labeled to the layout tool in the forward direction. Here are some tips:
1. If you add a new device (such as adding a pull-up resistor to the open drain output) after the layout design begins, add a resistor and network to the design from the schematic. After the positive mark, the resistance will be displayed as a non-layout of components outside the circuit board frame, at the same time display fly line to connect to the network. Then move the components into the circuit board frame and carry out normal wiring.
2. Backward annotation and reference mark changes work well together, such as post-renumbering.
Select the positioning device by highlighting
One way to view specific components or traces in a schematic during PCB layout is to use the 'Highlight Select' 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 target specific components or traces in a layout as you navigate the schematic.