Silicone Potting and Encapsulation Materials for Electronic and Electrical Devices

Designed to Perform when the heat is on

Our Silicone RTVs are used extensively in the Electronic and Electrical industries to ensure long-term, reliable performance of critical components and electronic circuit assemblies. Silicone adhesives, sealants, conformal coatings, potting gels, encapsulants, and thermal management materials play a vital role in many of today’s demanding electronic applications.

Definitions :

Potting and Encapsulation is the covering of an electronic or electrical device to protect it from the surrounding environment. Most of the time it is for protection from water or moisture and /or to electrically insulate it so that it will operate as designed. This can be done by two methods: potting and encapsulation. Many names have been used interchangeably so there is some confusion of the terms.

Potting

Potting is the process of partially or completely filling or embedding an enclosure with a compound for providing resistance to shock and vibration, as well as creating a seal against moisture, solvents, and corrosive agents. Potting compounds are also used to aid with electrical insulation, flame retardency and heat dissipation.

Encapsulation

Encapsulation is a process similar to Potting. With encapsulation instead of filling a mold with a compound like during the potting process, the electronic assembly is impregnated inside the compound with the help of a reusable mold. Typically the reusable mold is made out of hard to adhere to materials such as PTFE or Silicone. The purpose of encapsulation is to create a protective “shell” around the assembly.

Encapsulation provides resistance to shock and vibration, as well as creating a seal against moisture, solvents, and corrosive agents. Encapsulation is also used to help with electrical insulation, flame retardency and heat dissipation.

Potting Compound Options

The most common types of potting and encapsulating compounds are silicone, polyurethane, acrylic, epoxy resin. These materials vary in hardness from very soft to hard and rigid, and are designed to withstand many different types of environments. Each of these types does have its own strength and weaknesses. Determining which compound is best for your application will be based on operating and environmental conditions, material physical properties, and processing needs.

Each of the types have strengths and weaknesses with them, so the selection of the type is a trade off of several factors. Below is a brief description of each of the types, their categories and the strong and weak characteristics.

I. Epoxy

Strengths - Epoxy resins are very stable materials before and after hardening. They are easy to use and are predicable. They have good high temperature resistance up to 150oC and excellent chemical resistance except for some acids. They give excellent strength and excellent adhesion to metals and porous surfaces. The epoxy resins are hardened with many chemical which gives them a full range of hardened properties. This include amines, acids and anhydrides.

Weaknesses - They are notch sensitive, which means that a small crack will easily spread though the whole hardened piece. This cracking problem limits the use in high impact situations unless special techniques are used The bond to some plastics is not very good because the epoxy is too hard and does not "give" so when the plastic bends the bond is easily broken. Epoxy is also a high energy material and some plastics are low energy so they are not "wet" by the epoxy. Also they are not resistant to strong acids.

II. Urethane

Urethane or Polyurethane are a class of materials that form a urethane bond to make a polymer.

Strengths: Urethanes give a broad range of hardness from Shore D of 80 to Shore 000 of 50. Since they can have Tg below -40°C they are a good selection for SMT PC board potting. Since their gel time can be easily changed with an accelerator without changing the properties, they can easily be modified by the supplier to meet you speed of hardening requirements.

Weaknesses: Resistance to elevated temperatures are limited to 130°C continuous use and intermittent use at 150°C. The chemical resistance is not as good as epoxy but will stand splashes of chemicals but not immersion.

III. Silicone

Strengths: Excellent high temperature 200°C and low temperature properties. Have low temperature usage up to -40°C, so they are a good selection for SMT PC board potting.

Weaknesses: The cost is an important factor to consider. Adhesion to parts can sometimes be a problem and primers may have to be used.

RTV Silicone (Room-Temperature-Vulcanization silicone) is a type of silicone rubber made from a two-component system (base plus catalyst; A+B) available in a hardness range of very soft to medium--usually from 15 Shore A to 40 Shore. RTV silicones can be cured with a catalyst consisting of either Platinum or a Tin compound.. Applications include low-temperature over molding, potting, encapsulation, and lens applications for some optically clear applications.

Features of Silicone Potting Compounds

• Wide operating temperature range
• Excellent flexibility
• Good resilience
• Good chemical resistance
• Optically clear materials for LED applications

Performance Polymers offers a wide range of tailor made products under the brand “Encapsil” to meet these industry requirements.

Condensation (Tin) Cure Systems for Potting and Encapsulation

Addition (Platinum) Cure Systems for Potting and Encapsulation