In today’s world, protection is always a welcome asset. Whether it be protection from the rain above your head (mitigated by a roof), protection from the sun (mitigated by sunscreen), or protection from electromagnetic currents (mitigated by current isolation techniques amongst others).
With resins and coatings for your PCB, you can think about the forces that attack your PCB from a physical (environmental) standpoint - beyond EMI. Environmental concerns are more prevalent than ever in the world of PCB design. Each device that is created nowadays must meet steep market demands of making each device withstand as much as we do (and in most cases, even more!).
So how are we to keep our PCBs protected from the harsh environment we plan to release them into? Well after considering the non-visible EMI fields that could drain your design, a typical next step might be to start to consider resins or coatings. Literally covering the PCB in a separate material conforming to each tiny crevasse on your PCB, these additional assembly steps can be a lifesaver for those who plan to implement their devices into harsh climates.
But which one is correct for your application? As it always seems to be, the choice depends on what you need.
Coatings: The Short-Term PCB Protection Solution
Typically, coatings are applied as a clear, thin film. This adds minimal weight to the PCB and keeps the components visible. Pairing the visibility through the film along with extremely thin nature of the film (25-100 microns) allows for easy post-application modifications and repairs if necessary.
Coatings keep good thermal and chemical protection throughout short-term exposure to harsh environments. Any prolonged exposure introduces greater risk of failure, which should obviously be considered.
Additionally, the stress the coating applies on components is little to none, which is beneficial when dealing with thin pins or legs.
Applying these coatings is very simple. It can be applied via spray, brush or even hand-dipped. The nature of the single component coatings means that there is only one material (one step) required to apply. This keeps things simple for the manufacturer.
Coatings can often be sprayed straight on to the circuit making them a manufacturing-friendly option.
For Longer-Damaging Environments, Think Resins
Compared to the thin film coatings, resins offer superior protection against environmental forces with the trade-off of added weight and thickness. Applications tip the ruler at 0.5mm at the thinner end of the spectrum and often are applied much thicker.
The gobs of thickness will obviously add weight which may be a deterrent to some designs. Additionally, this thickness makes it extremely difficult, if not impossible, to conduct any post-application modifications or repairs. This certainly won’t allow for devices protected with resin to adapt to a circular design.
On the plus side, resin will grant you plenty of protection from prolonged exposure to the harshest of elements. Protection against shock will also be a benefit that a thicker resin can offer as it will dissipate through the material rather than a concentrated dose of volts. Resins often are applied in two stages with two compounds. This will certainly complicate the manufacturing process slightly since cure times for each will need to be accounted for.
If you are in the market of ‘keeping your PCB design secret and keeping it safe,’ a design practice is to add a dark colored or black resin to your design regardless of if you need the environmental protection. If anyone were out to unveil your PCB, the removal of the resin would utterly destroy the PCB, rendering it unable to be studied or copied.
Resins typically are a more aggressive form of protection against environmental forces.
Choosing Coating vs Resins for Your PCB
To find the right choice for our application, we can begin to ask some simple questions to supplement the info from above.
- What role will the housing play in environmental protection of the PCB? Is it simply a housing that looks nice to the end consumer (that will require resin level protection within), or will the housing already offer substantial protection (that will require a minimal coating if any extra protection)?
- Does your design deal with high-voltage of any kind that would benefit from added protection? Resin will help you here.
- Is weight a factor in the end goals of your design? Resin will add more, while coatings far less.
- Will manufacturing capabilities limit your decisions? Coatings are much more manufacturer friendly than resins, but any quality manufacturer should have capabilities to handle both.
The questions above are to get your mind churning while going along the design journey. You will likely have a plethora of your own design requirements, but keeping the listed info of the differences in resin and coatings in mind will keep your design on track to get the correct amount of protection required against whatever conditions you plan to release your design in.
Utilizing proper design planning and analysis software such as Altium Designer® can keep you ahead of the game in your design for protection. From power distribution analysis to component placement, any planning required to employ a resin or coating can be mitigated by Altium software. If you would like to know more about how Altium can assist in your design, talk to an Altium expert today.
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