Best design method for PCB: six things to consider when transferring PCB schematics to layout design.
Initial schematic transfer
In the process of transferring schematic diagram to the domain environment through the network table file, device information, network table, domain information and initial wire-width Settings will also be 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 detailed layout control for components and wiring, the device grid, copper coated grid, through hole grid and SMD grid can be designed as 1mil.
2. Set the blank area and 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/hole parameters according to the PCB manufacturer's ability.Most PCB manufacturers can support smaller overholes with bore diameter of 10mil and pad diameter of 20mil.
4. Set design rules as required.
5. Set custom shortcut keys for common layers to quickly switch layers (and create via holes) when wiring.
Handle errors in schematic transfer
A common mistake in schematic transmission is the nonexistent or incorrect packaging assignment.Note:
If a device is not enclosed in the schematic, a warning message is displayed indicating that the virtual component cannot be exported.In this case, no default encapsulation information is passed to the domain, and the component is simply removed from the domain.
If the wrapper passes through, but does not correctly match the valid wrapper shape, an alarm message indicating mismatches is also produced during the transfer.
Corrects package assignments in schematics, or creates an effective wrapper for any device.After the correction, the forward labeling step is performed to update and synchronize the design information.
Update the design through annotations
Annotation is the process of passing design changes from schematic to schematic or from schematic to schematic.Backward labeling (map to schematic) and forward labeling (map to schematic) are the key to keep the design accurate.
To protect what has been done, backup and archive the current version of schematic and layout files before any important forward or reverse annotation steps.
Don't try to change the schematic and layout at the same time.Change only one part of the design (either the schematic or the layout), and then perform the correct annotation steps to synchronize the design data.
Renumber the device
Device renumbering is a function that renumbers components on a PCB in a specific order.Reference labels should be ordered from top to bottom, left to right, above the PCB.This makes it easier to locate the device position on the board during assembly, testing and error checking.
Handles last-minute device or network changes
Last-minute changes to PCB devices or network tables are not desirable, but sometimes have to be done due to device availability problems or last minute design errors detected.If the component or network table needs to be changed, it should be done in the schematic and then through the forward marking 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 output), the resistance and network are added to the design from the schematic diagram.After the forward labeling, the resistance will be displayed as an unlaid component outside the circuit board frame, and the flywire indicates the connection network.Next move the component to the circuit board frame and wire it properly.
2. The backward labeling and reference label change can work well together, such as the post-layout renumbering.
Locate the device by highlighting it
One way to navigate a particular component or line in a schematic diagram during a PCB layout is to use the 'highlight selection' feature.This allows you to select a symbol or a walkway (or multiple objects) and see where they are in the schematic.
This feature is particularly useful when matching by-pass capacitors with their corresponding IC connections.In turn, you can locate specific elements or lines in your map as you navigate through the diagram.