Silicone Potting Mistakes and How to Avoid Them
When kicking off a new development or production project, selecting the perfect protection for your product is crucial. This is where choosing silicone potting solutions comes into play. In this article, we will go over the process of avoiding costly mistakes by choosing the best product for your application, and helping your team avoid unfortunate situations that might set you back.
Each silicone potting solution comes with highly specific characteristics. Before investing in a potting or encapsulating compound, make sure that you match your product with the right kind of protection, from conception to field application.
Electronic components and assembly:
Your first consideration should be the type of electronics you need to protect. Is it a single component? An open or an encased circuit? Does your device have exposed connectors? Your choice of the circuit board and the materials you use to build it are an essential detail to consider as well. Copper, silver, lead, gold, and nickel will each react differently under mechanical and chemical stress and heat, thus impacting not only the choice of the silicone potting itself but also the curing method each solution offers.
Will your product be a part of a bigger appliance, or is it completely encased? How fully do you want to cover your circuit board? Keep in mind that bigger silicone potting volumes can suffer some shrinkage. Significant shrinkage could have two undesired effects: loose adhesion to the side of your casing and excessive pressure on components soldered on your circuit board. This can be mitigated by augmenting the grip in the form of pull surfaces inside your casing, using primer or undercuts. A slower, longer curing time will also minimize this effect. The right blend of materials, design, and the curing process will set you up for success. You need to choose wisely.
Silicone potting and external conditions
Once the key characteristics of your devices are well-defined, you should consider the exterior factors. Most likely, you need a silicone potting solution that will act as a thermic barrier. Be it for the heat or the cold – the right product will answer your needs in a wide range of conditions.
The next things to identify are the type of chemical agents your product might be exposed to. This will help you define the chemical stability criteria of your selected silicone potting material. It is essential to find a product compatible with your components, and the soldering solution you chose in your design. What we want to avoid is a situation where your chosen silicone protects your product from acid but makes your board’s silver solders brittle.
Humidity factors are important to take into account. Will your device be submerged? Is it a medical framework application that is washed intensively? Humidity can also be caused by condensation, atmospheric pressure changes, or simply from prolonged exposure to elements like rain. Choose your solution to match all of those.
- Mechanical aspects
What type of shock, pressure, or vibration will your device be subjected to? Will your product be exposed to cuts or possible perforations? Silicone potting has self-repair properties that vary with the level of viscosity maintained after curing. Choose the product that meets your mechanical needs.
When it comes to encapsulation, conductivity is not always a desirable trait. Each type of silicone potting has its own conductivity rating. Some products are made for conductive purposes and include graphite or silver in their compound. Your supplier will be able to find the best choice for you.
Curing process considerations
This is very important, as curing impacts many aspects of your silicone potting choice. Curing of silicone is the process where a liquid compound solidifies. This reaction can be heavily affected by ambient temperatures that may speed the process. Some silicone have the ability to cure in cold temperatures or even underwater.
Curing releases energy in a chemical reaction. That energy mainly manifests itself under the form of heat, thus being qualified as an exothermal reaction. Depending on your selected silicone potting compound, the heat level of the reaction could interact with your electronic components or the soldering material binding them together. Some compounds harden with just light exposure, and some can be slowed down with controlled room temperature. Different levels of curing are available for you when you find the right manufacturer to work with. To avoid unwanted heat generation, make sure you choose the right material for your product.
The quantity of silicone potting is another factor to consider when discussing exothermic risks. The bigger the amount of the potting material, the more heat it will generate. Learning how to calculate and handle large quantities of silicon for curing is an important issue to consider, and one your supplier will be happy to help you with.
Temperature changes can result in inflation or shrinkage of your chosen compound. A common reaction of silicon for potting is shrinkage, but only if it does not have the appropriate fillers (non-shrinkable components). Speed is also a factor playing on the elasticity of the potting, as the faster the curing happens, the more intense the reaction you will get, resulting in energy release and possible shrinkage.
Outside temperatures have an important effect on the solidity of silicone potting compounds. Generally, the colder it is, the harder the silicone gets, making it more brittle. Extreme heat exposure will not make your silicone go back to a liquid state, but using the wrong kind of silicone for your application might make it combust.
Overall, you can easily avoid silicone potting mistakes. Just make sure to identify your device characteristics, what it needs to be protected against, and what are its vulnerabilities. Let your supplier help you with choosing a product to match all your specifications. From heat resilience and a stable curing method to better adhesion and seal, your manufacturer will guide you to the right product for your success.