Unlock The Advantages And Disadvantages of Silicone, Epoxy, And Polyurethane Potting Adhesives

Unlock The Advantages And Disadvantages of Silicone, Epoxy, And Polyurethane Potting Adhesives

I. What is Potting?

Potting (also known as encapsulation) is the process of pouring polyurethane potting compounds, silicone potting compounds, or epoxy resin potting compounds into devices containing electronic components and circuits, either by using specialized equipment or manually. These compounds then cure at room temperature or under heat to form high-performance thermosetting polymer insulating materials. This process is designed to achieve the goals of bonding, sealing, encapsulation, and protective coating.

II. The Functions of Potting

Potting acts like an invisible protective shield for electronic components. It involves the precise injection of liquid compounds into the packaging devices, which then solidify to form a tough thermosetting insulating layer. This process is aimed at enhancing the overall integrity of the device, improving its resistance to shock and vibration, and strengthening the insulation between internal components, thereby promoting the trend of miniaturization and weight reduction. More importantly, the potting process can isolate the components from environmental influences, such as preventing moisture and humidity from corroding the components, significantly enhancing their stability and waterproof performance.

III. The Advantages and Disadvantages of Three Types of Potting Compounds

1. Epoxy Resin Potting Compound

Epoxy resin potting compounds are mostly rigid. Once cured, they become as hard as stone and are difficult to remove, which provides good confidentiality. However, there are also a few types that are soft. The common temperature resistance is around 100°C, while those that cure with heat can withstand temperatures of about 150°C. There are also some that can withstand temperatures above 300°C. They have characteristics such as fixing, insulating, waterproofing, oil-proofing, dust-proofing, theft-proofing, corrosion resistance, aging resistance, and resistance to cold and heat shock. Common types of epoxy potting compounds include flame-retardant, thermally conductive, low-viscosity, and high-temperature resistant types.

• Advantages: They have good adhesion to hard materials, excellent high-temperature resistance and electrical insulation capabilities, simple operation, and are very stable before and after curing. They also have excellent adhesion to a variety of metal substrates and porous substrates.

• Disadvantages: They have weak resistance to temperature changes and are prone to cracking after exposure to thermal shock, allowing moisture to seep into the electronic components through the cracks, resulting in poor moisture resistance. Moreover, after curing, the compound becomes a hard and brittle gel, which can easily damage electronic components. Once potted, it cannot be opened, and the repairability is poor.

• Application Scope: Epoxy resin potting compounds can easily penetrate into the gaps of products and are suitable for potting small and medium-sized electronic components that do not have special requirements for environmental mechanical properties under normal temperature conditions, such as automotive and motorcycle igniters, LED driver power supplies, sensors, toroidal transformers, capacitors, triggers, LED waterproof lights, and the confidentiality, insulation, and moisture (water) protection potting of circuit boards.

2. Silicone Potting Compound

Silicone electronic potting compounds are mostly soft and elastic after curing, which can be repaired, and are commonly referred to as soft gels. Their adhesion is relatively poor. The color of these compounds can generally be adjusted according to needs, either transparent, opaque, or colored. Two-component silicone potting compounds are the most common, including both condensation-curing and addition-curing types. Generally, condensation-curing types have poor adhesion to components and the potting cavity, and volatile low-molecular substances are produced during the curing process, resulting in a noticeable shrinkage rate after curing. In contrast, addition-curing types (also known as silicone gels) have extremely low shrinkage rates and do not produce volatile low-molecular substances during curing, allowing for rapid curing with heat.

• Advantages: They have strong resistance to aging, good weatherability, and excellent impact resistance. They possess outstanding resistance to temperature changes and thermal conductivity, enabling them to be used within a wide operating temperature range. They can maintain elasticity between -60°C and 200°C without cracking and can be used long-term at 250°C. The heat-curing types have even higher temperature resistance. They also have excellent electrical properties and insulation capabilities, with better insulation performance than epoxy resins, capable of withstanding voltages above 10,000V. After potting, they effectively enhance the insulation between internal components and circuits, improving the stability of electronic components. They are non-corrosive to electronic components and produce no by-products during the curing reaction. They also have excellent repairability, allowing for quick and convenient removal and replacement of sealed components. They have good thermal conductivity and flame retardancy, effectively improving the heat dissipation and safety of electronic components. They have low viscosity and good flowability, enabling them to penetrate into small gaps and under components. They can cure at room temperature or with heat, have good self-degassing properties, and are more convenient to use. They have a small curing shrinkage rate and excellent waterproof and shock-absorbing capabilities.

• Disadvantages: They are expensive and have poor adhesion.

• Application Scope: They are suitable for potting various electronic components that operate in harsh environments.

What are the advantages of silicone electronic potting compounds compared to other potting compounds?

• Advantage 1: They provide long-term protection for sensitive circuits or electronic components, offering long-term effective protection for electronic modules and devices, regardless of their simple or complex structures and shapes.

• Advantage 2: They have stable dielectric insulation properties, serving as an effective barrier against environmental pollution. After curing, they form a soft elastomer that eliminates stress caused by impact and vibration within a wide range of temperatures and humidity levels.

• Advantage 3: They can maintain their original physical and electrical properties in various working environments, resisting degradation from ozone and ultraviolet light, and have good chemical stability.

• Advantage 4: They are easy to clean and remove after potting, facilitating the repair of electronic components, and new potting compound can be re-injected into the repaired areas.

3. Polyurethane (PU) Potting Compound

Polyurethane potting compound, also known as PU potting compound, is mostly soft and elastic after curing, which can be repaired, and is commonly referred to as a soft gel. Its adhesion lies between that of epoxy and silicone, with moderate temperature resistance, generally not exceeding 100°C. More bubbles tend to appear after potting, and the potting process must be carried out under vacuum conditions. Its adhesion is also intermediate between epoxy and silicone.

• Advantages: It has good low-temperature resistance and the best shock-absorbing performance among the three types. It features low hardness, moderate strength, good elasticity, water resistance, mildew resistance, shock resistance, and transparency. It also has excellent electrical insulation and flame retardancy, is non-corrosive to electrical components, and has good adhesion to metals such as steel, aluminum, copper, and tin, as well as to materials like rubber, plastic, and wood.

• Disadvantages: It has poor high-temperature resistance. The surface of the cured gel is not smooth and has poor toughness. It has weak aging resistance and UV resistance, and the gel is prone to discoloration.

• Application Scope: It is suitable for potting indoor electrical components with low heat generation. It can protect properly installed and adjusted electronic components and circuits from the effects of vibration, corrosion, humidity, and dust, making it an ideal potting material for moisture and corrosion protection of electronic and electrical parts.

IV. Issues to Consider When Selecting Potting Materials

1. Performance Requirements After Potting: Operating temperature, thermal cycling conditions, internal stress on components, whether for outdoor or indoor use, stress conditions, requirements for flame retardancy and thermal conductivity, color requirements, etc.

2. Potting Process: Manual or automatic, room temperature or heated, complete curing time, gelling time of the adhesive after mixing, etc.

3. Cost: The specific gravity of potting materials varies greatly. We must consider the actual cost after potting, rather than simply looking at the selling price of the material.

Adhesives for potting are classified by function into thermal conductive potting adhesive, bonding potting adhesive, and waterproof potting adhesive. By material, they are categorized into polyurethane potting adhesive, silicone potting adhesive, and epoxy resin potting adhesive. Both soft and hard adhesives can be used for potting and waterproof insulation. If high-temperature resistance and thermal conductivity are required, it is recommended to use silicone soft adhesive. If low-temperature resistance is needed, polyurethane soft adhesive is suggested. If there are no specific requirements, epoxy hard adhesive is recommended, as it has a faster curing time than silicone.

Epoxy resin potting adhesive has a wide range of applications and diverse technical requirements, with many varieties. It is divided into two categories based on curing conditions: room temperature curing and heated curing. In terms of formulation, there are two-component and one-component types. Generally, room temperature curing epoxy potting adhesive is two-component. Its advantage lies in the fact that it can cure without heating after potting, with low equipment requirements and convenient use. However, the drawbacks include high working viscosity of the adhesive mixture, poor impregnation, short pot life, and relatively low heat resistance and electrical properties of the cured product. It is usually used for potting low-voltage electronic devices or in situations where heating curing is not suitable.

V. Potting Process

At present, potting technology is mainly divided into manual and mechanical methods. Manual vacuum potting is relatively simple to operate, with low equipment costs and maintenance expenses. Mechanical vacuum potting, on the other hand, is more advanced and is divided into two processes: potting after mixing and degassing of components A and B, and degassing before mixing and potting. Although the initial investment in mechanical potting is higher, it significantly surpasses manual potting in terms of product consistency and reliability, making it particularly suitable for production scenarios with high quality requirements.

Process Details

1. Manual Vacuum Potting: The traditional manual method, relying on manual operation to achieve precise injection, is suitable for small-scale projects.

2. Mechanical Vacuum Potting:

• Potting after Mixing and Degassing of Components A and B: An advanced process that ensures thorough degassing of the material, improving product quality.

• Degassing Before Mixing and Potting: Each step is carefully controlled to ensure the perfect integration of the potting material.

As a core technology for the protection of electronic products, potting not only resists the erosion of moisture, mold, and salt fog but also significantly enhances the survival capability of electronic products in extreme environments. The progress of science and technology continuously drives the innovation of potting materials, with high-performance new materials emerging constantly. This has led to an increasingly broad range of applications for potting technology, making it an indispensable part of electronic device protection.

In summary, potting is not only a key link in the design of electronic products but also an important guarantee for improving product durability and reliability. In the future world of electronic devices, potting will play an increasingly important role, bringing more stable and reliable technological experiences to our lives.

In conclusion, YINSU Flame Retardant Company's RP-EP, red phosphorus slurry, is an effective flame retardant for epoxy resins, offering several advantages such as high phosphorus content, non-halogenated nature, and good environmental and health properties. It can be used in various applications, including adhesives, battery cases, electronic connectors, electric vehicle components, foam materials, gaskets, electrical equipment housings, flame retardant insulation, high voltage insulation, flame retardant sheathing, and sealants. Additionally, RP-EP can be used in the production of epoxy resins and polyurethanes, as well as in pultrusion molding and other advanced technologies. For better handling, especially flow properties, the product can be heated up to 50°C to a maximum of 80°C. It is equivalent to Exolit RP6500.