May 25, 2019 by Emily Gray-Fow
Throughout industry and the automotive sector, the effects of EMI and RFI (electromagnetic interference and radio frequency interference) are becoming more of an issue as technology evolves.
Considering the rapid increase in the number of wireless technologies and frequency-based sensors, being able to protect your circuits from interference now matters more than ever—whether or not your circuit produces any of this interference itself.
Failing to protect your product from interference signals can end up reducing the number of use cases where it is effective, ultimately dragging down your bottom line and letting competitors with properly shielded products become the go-to choice for your customer base.
Signals Everywhere
If your product is likely to be used near any systems that put out EMI or RFI then shielding is rapidly becoming a must.
Automotive
As smart and autonomous vehicles become the norm, the number and frequency of the signals put out by their various systems continue to increase, both inside and outside the vehicle.
Industrial
Similarly, as industrial IoT becomes more commonplace, wireless networks are springing up in what would have been unlikely places just a few years ago. Making sure your product will carry on working in such environments is something that can make or break your chances of success.
In fact, the advent of the IoT means it’s virtually impossible to guarantee a signal-free place for any product.
The most effective way to shield your circuit in place is by mounting a Faraday cage directly on the PCB where needed. When using a Faraday cage mounted directly to the PCB, you can save space in the final product as it allows you to mount PCBs and components much more closely whilst still preventing EMI/RFI.
There are a few different ways to go about this, and they all have their own benefits and pitfalls.
Shield directly soldered to the PCB
This is the cheapest option but also the least flexible. Not only does it increase the amount of heat stress on the PCB (which can lead to early failure through deformation or cracking), it’s also permanent, making it impractical if you need further access to the circuit under the shield for rework, repairs, or to add extra parts.
Two-part shield soldered directly to the PCB
Options with a hatch or door in the shield allow for future access under the shield but are the most expensive option.
Clip-on shield held in place with shield clips
The most flexible and cost-effective option that allows for future access under the shield. Simple clips are soldered to the PCB, allowing a choice of different shields to be easily clipped and unclipped as needed.
It doesn’t take much to realize the clip-on option is going to be best for most applications. Brands like Harwin, Laird, and Autosplice offer clip-on shielding ranges that come with the clips in tape-and-reel format, enabling automated placement of the clips at high speeds.
Harwin EZ shield clips. Image courtesy of Harwin.
There are several different brands offering clips and shield cans for this purpose, and they all offer clips on a roll and several options for shielding cans, perforated and unperforated. Beyond that, which one you choose will depend very much on your specific needs.
Think about whether you need your shield can to be steel or copper—bearing in mind how much faster copper conducts heat—and whether you’ll need to special order certain sizes or can make do with the dimensions available from existing suppliers. If you need a flexible solution for prototyping, consider Harwin’s Shield Can Kit with its adjustable can sizes. It’s also important to work out which frequencies you need to protect against, as this has a bearing on clip geometry.
Comparison of signal shield products from Harwin, Laird, and Holland Shielding Systems.
So, how does all of this save space on your PCB designs?
By letting you fit components closely together without worrying about EMI/RFI, you gain the ability to make your designs much more compact. The flexibility of shield placement that you get from clip-on designs means you can always find a solution that suits your design.
The ability to remove and replace shields repeatedly during the manufacturing process without risking fatigue-related cracks to the PCB also saves you time and resources.
Having the shield in place between manufacturing operations also makes the workpiece more robust between operations. This gives you confidence in the quality of workmanship coming off the final production line. All of this is in addition to time savings to be had from the automatic placement of the shield clips.
No matter the size of your manufacturing operation, you should seriously consider using clip-on EMI/RFI shields on your PCBs. By reducing the space needed between components and increasing the protection your circuits have from nearby electromagnetic and radio interference sources, you can help ensure that your designs will stand the test of time.
