What is Silkscreen？ After manufacturing a PCB, you’d need to place your components in their proper positions. But what if you end up using the wrong component placement? After all, a standard PCB can use multiple resistors with different references, so how do you find the perfect positions to place components?
In such scenarios, what you need for your PCB is a silkscreen. Undoubtedly, you may never get the proper component placement without it. But don’t worry if you don’t know much about silkscreens.
This article will show everything about silkscreen and what to do when designing a PCB with one.
What is Silkscreen in PCB?
Silkscreen on PCB (Edited)
Source: Wikimedia Commons
The point of using a silkscreen is for easy component identification. Silkscreen is the topmost layer of a PCB that identifies parts of the PCB, marks, references, components, symbols, and test points.
You’ll usually find silkscreens on the component side of any PCB, but it’s also possible to use them on the solder side (though it’s more expensive).
Indeed, silkscreens use non-conductive epoxy ink that won’t interfere with your board’s performance. The more common colors for silkscreen texts are yellow, black, and white. Also, you can choose from various fonts, but ensure the values stay legible.
Additionally, the traditional method for silk-screening requires you to stretch a polyester screen on aluminum frames, use a laser photoplotter, curing ovens, and spray developer.
Why is Silk-screening Important?
As we mentioned earlier, silkscreens don’t affect a board’s functionality. But, they help provide manufacturers and engineers with helpful information. They include;
1. Reference indicators: silkscreen helps show reference indicators that help identify components through BOM. Under this, we have the Pin 1 indicator and polarity indicator. The Pin 1 indicators show you how to connect component pins on a footprint pad. In contrast, the polarity indicators show you how to place polarized arrows.
2. Warning symbols: As the name implies, warning symbols tell you what voltage points you shouldn’t cross or handle.
3. Silkscreens can help you quickly identify your boards’ unique numbers and test points.
4. Also, with a silkscreen, it’ll be easy to locate your components through reference designators.
5. Additionally, Silkscreens can help manufacturers and technicians identify board issues quickly with test points. These test points also provide information that makes testing and troubleshooting easier.
6. It also helps provide a device’s information, so you won’t be lost if you don’t have a datasheet.
Methods of SilkScreen Printing
There are three ways you can apply silk screen on your PCB. They include:
1. Direct Legend Printing (DLP)
Direct legend printing is the most expensive method among the three. It’s a process that requires acrylic ink and an inkjet projector.
That’s not all that makes it expensive. First, you’ll have to apply the ink on your board via CAD software. After that, you must expose the ink to some UV light.
Furthermore, avoid using acrylic ink on PCBs with silver finishes because it’s not a suitable match-up.
2. Liquid Photo Imaging (LPI)
LPI is your go-to method if you’re printing lines that are more than four miles. It’s similar to applying a solder mask and offers high accuracy.
Moreover, the method requires you to coat your laminate with epoxy and expose it under UV light. After that, you’ll need to cure inks and develop the board.
Source: Wikimedia Commons
However, LPI uses more ink than the other imprint methods and has a long set-up time. Plus, it only uses white colors.
3. Manual Screen Printing
You can use manual screen printing If your board’s track width is more than 0.007” or its registration tolerance is 0.005”. In essence, it’s a process that requires stencil printing for traces and texts. It also makes the traces with nylon and directs ink via the stencil on the board’s laminate or layer.
Then, you’ll cure the ink by baking it in an oven. It’s a simple way to create silkscreen layers, and you can make large-sized texts. However, you’ll need some level of craftsmanship to master this method.
Considerations when Designing the PCB with a Silkscreen
Here are some things to consider when designing silkscreens for your PCB:
Silkscreens are tricky to make. Since it’s an artistic application, a DIY silkscreen won’t give you the results you’d get from a manufacturer, especially if you don’t have the required skillset. So, please leave it to the professionals and order a silkscreen along with your PCB.
Use Monochrome Colors
It’s not necessary to use fancy colors on your PCB’s silkscreen. Instead, use black and white only. Plus, you can adjust the shades to create a sharp contrast with your solder mask color. But, your silkscreen won’t be visible if the contrast is insufficient.
Not all Fonts Work
Some fonts won’t work during the manufacturing process. Even if these fonts are easy and fast for your software to create, you should consider using only fonts approved by your contract manufacturer (CM). Also, these fonts must be easy to read.
Stick to your Contact Manufacturer’s Requirements
Ensure you meet all your CM’s clearance and dimension requirements. Failure to do so, you’ll end in obscured silkscreen values. And, a silkscreen won’t be effective if you can see all the items.
Silkscreen in Components vs. Silkscreen in the PCB Layout
PCB design software usually designates the silkscreen as the top overlay or bottom layer (depending on your silkscreen type). You can place your silk screen directly on your PCB layout or in your components with your design software.
By PCB layout, we mean placing your silkscreen manually. On the other hand, component silk-screening happens if your silkscreen applies automatically after importing your components into your designs.
Here are the different items you should place manually on a PCB layout or automatically through components:
Table Showing silkscreen Items
How to Clean up Silkscreen
There’s a chance of overlap in your silkscreen markings. When such situations occur, you’ll need to rearrange and clean some markings for more unambiguous indication and readability.
Thankfully, it’s not a severe problem, and you can use a good design tool to clean mistakes on your silkscreen (as long as you have the Gerber files). Be sure to choose an easy tool so you don’t encounter problems while cleaning up your silkscreen.
PCB Silkscreen vs. Solder Mask
Solder mask and Silkscreen
Source: Flickr (edited)
PCB silkscreen is simply a way to show various information on your board without affecting its functionality. Solder mask, on the other hand, increases PCB functionality by shielding the board from electrical shorts and corrosion. Plus, it ensures solder stays on the pads and not for bridges by flowing to traces or planes.
PCB Silkscreen Colors
There are four colors we recommend using for your silkscreen. White is universal and won’t cause problems during the manufacturing process. Yellow, black and red is also great colors for silkscreen.
Although some designers use colors like pink, we don’t recommend it because of its unique characteristics. It would also cause problems during the manufacturing process.
How to Choose a PCB Silkscreen Manufacturer
You’ll need a reliable PCB manufacturer if you don’t want any problems with your silkscreen production. While many PCB experts have enough knowledge on this subject, you still need to consider some factors before making a choice.
First, think about the visual aspect of silkscreens. You’ll need to choose the clearance spacing, font size, color, and other silkscreen design options at this stage. Remember that it affects the production cost, so you’ll need a reliable manufacturer to help select these aspects correctly.
Then, you can check out your manufacturer’s capabilities by stating your requirements. If that manufacturer is reliable, they’ll be confident and willing to walk you through the process. Choosing an experienced and dedicated PCB manufacturer will make the process easier.
PCB with Silkscreens Items
PCB silkscreens are a process that requires skill and can affect your PCBs overall quality. Interestingly, silkscreens exist, so you don’t have to draw outlines on your copper layer.
Silkscreens don’t directly influence PCB performance, and it’s a great way to write on your PCB. However, you must watch the kind of color you use so your silkscreen items remain visible.
Contact us if you’re ready to manufacture your silkscreens design. We’ll be sure to offer the best low-cost and dedicated PCB services.