Don’t Be Surprised By Markings on a PCB
In the days of the old Model T Ford, you could get any color you wanted – as long as it was black. Not that long ago it was the same way for printed circuit boards, of course, the only color available was green.
Today, there are many color options for both solder mask and silkscreen. Green, blue, red and every color combination in between. Some designers, in fact, go the extra mile to make the final look of the PCB quite aesthetically pleasing. That is why it can be very disappointing when the board shows up with unexpected markings on it.
Markings on a board serve a specific purpose. However, it is ultimately dictated by the customer whether they are used and where they are placed.
How can you avoid unwanted markings?
Here are some basic instructions on how to get the desired look for your board. First, understand that there are a few markings that are typically added to every PCB including:
- The PCB Manufacturers Logo or Mark
- Date Code of Manufacturing
- Flame Rating (94-V0)
- Electrical Test Verification
The PCB vendor logo is used to show who manufactured the PCB. A PCB vendor views this as important for warranty and tracking purposes (since a single PCB design produced by multiple manufacturers can be difficult to differentiate). However, if undesirable, there are a couple of options available.
First, the logo can instead be added as a copper feature or on the silkscreen. Many customers will request a logo in silkscreen rather than copper for electrical reasons; interference with antenna function being one of them.
Second, it can be requested of the PCB vendor that the logo not be used at all. But be aware that this may interfere with the PCB manufacturer’s ability to warranty the PCBs. And, if UL is a requirement then the PCB vendor logo is required as well. If you request that the logo not be included, it will affect the UL compliance of the PCB. It’s also worth noting that the logo can be used without the flame rating so if the flame rating is required, be sure to request it.
The date code will show the year and the week that the board was manufactured. This can be helpful to establish a timeline for boards, especially for designs that are ordered periodically, in order to track any issues that arise.
To ensure you receive exactly what you need, include notes in the fab drawings to communicate with your PCB vendor. These notes might look like the following:
- “No vendor markings allowed”
- “Vendor markings on bottom side only”
- “Vendor markings in silkscreen only”
- “Locate vendor logo as indicated by (symbol)” – place the symbol in the design where the vendor logo will be placed
- “Vendor logo may not be located in “keep out” areas as indicated by (symbol)”
The options are endless, but what matters is that you get exactly what you need to make your next project a success.