Boards that are used in real products require some method to be affixed to their enclosure or packaging. In many products, the typical method for doing this is to use mounting holes. The mounting holes used in a PCB can be plated or non-plated, depending on the type of fastener and the type of enclosure. If you’re unsure of which type to use and how to quickly change them in the PCB layout, keep reading to learn more.
Plated vs. Non-plated PCB Mounting Holes
Mounting holes can be used in any type of electronics packaging that involves screws or standoffs to support the PCB. This is probably the most common mounting form, with other options being slide mounting, snap-in mounting, or encapsulation. If you are going to include mounting holes, the holes will need to be either plated or non-plated through-holes.
The difference between these two types of holes is largely electrical; there is little mechanical difference between these types of mounting holes (see below for an explanation of this).
Finally, an important point to note is that plated through-holes have only negligible difference in mechanical strength compared to non-plated through-holes. The strength of a mounting hole comes from the rigid materials used to build the PCB stackup. These materials harden during curing and they give the PCB its mechanical strength, and it is their mechanical properties that have to be considered in any kind of mechanical testing or simulation.
Switching Between Plated and Non-plated Holes in OrCAD
One common approach to using plated or non-plated mounting holes in a PCB is to define the holes as a component in the schematics. As the schematics are being captured, any connection between a plated through-hole and ground can be defined as a standard net connection. When the design is imported into the PCB layout, the connection to ground can then be routed as normal, or connected to an internal plane or copper pour with a landing pad.
If you created your OrCAD schematics with plated through holes, you can easily switch these to non-plated through holes and vice versa inside the PCB layout; you won’t need to go back and update the footprint in the library. To do this in OrCAD PCB Editor, hover your mouse over the hole you want to modify and select the Modify design padstack option. To just modify the selected hole, select Single instance, or to modify all holes matching the library entry, select All instances.
This option will open the Padstack Editor. In this window, navigate to the Drill tab and select the Plated or Non-plated option to set the hole type. Other aspects like drill tolerance and dimensions can be set in this window. When the padstack has been edited, select File/Update to design so that the padstack updates in the layout. This is required to ensure the update to the padstack appears in the PCB layout. Note that this will not update the padstack in your library, it will only update the instance used in the PCB layout.
If the padstack update is applied to convert a non-plated through-hole to a plated-through hole, the plated hole can then be connected to a nearby net if needed. The standard practice is to connect the plated hole to a ground net or a copper pour. To do this, select the plated hole, right-click, and select the Net Short option. Next, click the pour where you want to short the plated hole, and then right-click to complete the command. The nearby pour will then connect to the plating on the hole.
This plated through-hole has been shorted to the nearby DGND copper pour.
The alternative option is to use the Replace padstack option, where an existing padstack can be selected from a library. From here you can use the Net Short option to define the net connection on a plated through-hole.
No matter what types of mounting holes or vias you want to use in your PCB layout, you can take full control of your designs with the complete set of CAD tools in OrCAD from Cadence. Only Cadence offers a comprehensive set of circuit, IC, and PCB design tools for any application and any level of complexity.