Which Kind Of Potting Compound Is Good For Pouring On Electronic Components?

With the rapid development of electronic products, the precision of electronic products has been continuously improved, and many electronic components will generate a lot of heat during use. If this heat is not dissipated in time, it is easy to cause high temperature and overheating of electronic components, resulting in failure and affecting electronic and electrical products. service life.

Therefore, efficient heat dissipation has become the focus of the design, especially on chip processors, LEDs, and power packs. In order to solve this problem, electronic thermal conductive potting compound is generally poured into electronic products as a thermal conductive material, so as to efficiently conduct the heat inside the electronic product to the heat dissipation shell, thereby improving the safety and service life of the electronic product.

There are generally three kinds of potting compounds suitable for pouring on electronic components, namely: epoxy resin potting compound, polyurethane material potting glue and silicone material potting glue (here we call it electronic thermal conductivity potting). Plastic closures). Among them, the most suitable for potting in electronic products is silicone potting compound, because other materials have some unavoidable defects.

The potting compound of epoxy resin material has weak resistance to cold and heat changes. Once it is impacted by cold and heat, the colloid will crack, and moisture such as rainwater and condensation will easily penetrate into the electronic components through the cracks, resulting in electronic components. The device is disconnected, which seriously affects the use of electronic products. Polyurethane potting glue, because of its high toxicity, is easy to cause allergic symptoms, so it is necessary to pay great attention to the production and production.

The silicone-based potting compound has excellent electrical properties and insulating properties. It can be used in electronic components to ensure that the components will not interfere with each other, which can effectively improve the stability of electronic products, and can also play a role in thermal conductivity and flame retardant. , Waterproof and shockproof.

Under normal circumstances, the indicators for measuring electronic thermal conductive potting compounds mainly include the following aspects:

Firstly: Thermodynamic properties – thermal conductivity

Thermal conductivity is an important parameter to measure the thermal conductivity of thermally conductive materials. The higher the thermal conductivity, the better the thermal conductivity and heat dissipation effect, and the heat generated by the components can be quickly dissipated. When other conditions are constant, the higher the thermal conductivity, the better the electronic thermal conductive thermal potting compound.

Secondly: Electrical Properties – Dielectric Strength, Volume Resistivity and Dielectric Constant

Of the three properties of interest are dielectric strength (sometimes also expressed in terms of breakdown voltage) and volume resistivity.

Dielectric strength is a measure of the electrical strength of a material as an insulator. It is defined as the maximum voltage a unit thickness can withstand when a specimen is broken down, expressed as volts per unit thickness. The greater the dielectric strength of a substance, the better its quality as an insulator.

Volume resistivity is the resistance of a material to current per unit volume, which is used to characterize the electrical properties of a material. Generally, the higher the volume resistivity, the higher the effectiveness of the material as an electrically insulating component.

The dielectric constant is used to measure the ability to interfere in electromagnetic fields.

Thirdly: Physical properties – fluidity, density and adhesion

Because the electronic thermal conductive potting compound is fluid, it has a certain fluidity, and the popular thermal potting compound can be used to fill the gap with smaller pores and increase the volume of the thermal conduction and heat dissipation contact surface.

Density (specific gravity) is also an indicator of special concern for electronic thermal conductive potting compounds. Generally, under the same thermal conductivity, the lower the specific gravity, the better. The lower the proportion, it is used in industries such as automotive power supply, which can effectively improve energy efficiency.

The electronic thermal conductive potting compound has a certain viscosity, which can firmly bond the heating device and the heat sink together, so the viscosity is also an important indicator to consider the performance of the thermal conductive electronic potting compound.

What is sealant? What are the types of sealants? Classification of sealants

What is sealant?

Sealant refers to a sealing material that deforms with the shape of the sealing surface, is not easy to flow, and has a certain adhesiveness. It is an adhesive used to fill configuration gaps for sealing. It has the functions of anti-leakage, waterproof, anti-vibration, sound insulation and heat insulation.

Classification of sealants

One. Classification by sealant base material

Rubber type: This type of sealant is based on rubber, and commonly used rubbers include polysulfide rubber, silicone rubber, polyurethane rubber, neoprene rubber and butyl rubber.

Resin type: This type of sealant is based on resin, and commonly used resins include epoxy resin, phenolic resin, polyacrylic resin, unsaturated polyester resin, polyvinyl chloride resin, etc.

Oil-based type: This type of sealant is based on oil, and the commonly used oils are various vegetable oils (such as linseed oil, castor oil, and tung oil, and animal oil, etc.).

Two. Classification by sealant vulcanization method

Wet air vulcanized sealant: This type of sealant is vulcanized with moisture in the air, and it mainly includes one-component polyurethane, silicone rubber and polysulfide rubber. The polymer base material contains active groups, which can react with water in the air to form cross-linking bonds, so that the sealant is vulcanized into a network structure.

Chemical vulcanization sealants: Two-component polyurethane, silicone rubber, polysulfide rubber, neoprene and epoxy resin sealants belong to this category, and are generally cured at room temperature; some one-component chlorosulfone Polyethylene and neoprene sealants and polyvinyl chloride sol paste sealants must be vulcanized by chemical reaction under heating conditions.

Heat transfer sealant: PVC resin dispersed with plasticizer, and sealant with bitumen-containing rubber are two different types of heat transfer systems. Vinyl plasticizers are liquid suspensions at room temperature and harden by heating to solidify, while rubber-asphalt sealants are hot-melt.

Oxidation-hardening sealant: Surface-drying sealant for inlaying or mounting glass, based on dry or semi-dry vegetable or animal oils, which may be refined polymerized, blown or chemically modified.

Solvent volatilization coagulation type sealant: sealant based on non-viscous polymer after solvent volatilization. This type of sealant mainly includes butyl rubber, high molecular weight polyisobutylene, acrylate with a certain degree of polymerization, chlorosulfonated polyethylene And sealants such as neoprene.

Three. According to the performance of sealant after construction

Curing sealant: It can be divided into two types: rigid sealant and flexible sealant;

a) Rigid sealants form hard solids after vulcanization or solidification, and rarely have elasticity; some varieties of such sealants play both sealing and bonding functions, and their representative sealants are epoxy resin, polyester resin Resin-based sealants such as polyacrylates, polyamides and polyvinyl acetate.

b) Flexible sealants remain soft after vulcanization, and they are generally based on rubber elastomers; the flexibility varies greatly, and the hardness is in the range of 10 to 80. Some varieties of this type of sealant are pure rubber, and most of them have good adhesive properties.

Non-curing sealant: This type of sealant is a soft setting sealant that remains non-drying after construction. Usually a paste, it can be applied to the joint with a scraper or a brush, and many sealants of different viscosities and different properties can be formulated.

Four. Classification by sealant form

Paste sealant: This type of sealant is basically used in static joints, and the service life is generally 2 years or more. Three main materials are usually used: oil and resin, polybutene, and asphalt.

Liquid Elastomeric Sealants: Includes liquid polymers that vulcanize to a true elastic state, which have the ability to withstand repeated seam deformation. The polymer elastomers used in elastomer sealants include liquid polysulfide rubber, mercapto-terminated polypropylene ether, liquid polyurethane, room temperature vulcanized silicone rubber, low molecular weight butyl rubber, etc.​

Hot melt sealant: Hot melt sealant, also known as thermal construction sealant, refers to a sealant based on a blend of elastomer and thermoplastic resin. This type of sealant is usually extruded directly into the seam through a certain mouth model under heating (150 ~ 200 ℃); thermal construction can improve the wetting ability of the sealant to the bonded base material, so it is suitable for most bonded bases. The material has good adhesion. Once in place, it cools to form or form a film into a strong elastomer with little shrinkage. The main materials of thermal construction sealants are mainly isobutylene polymers, EPDM rubber and thermoplastic styrene block copolymers.

Liquid sealant: This type of sealant is mainly used for the sealing of mechanical joint surfaces to replace solid sealing materials, namely solid gaskets, to prevent the leakage of mechanical internal fluids from joint surfaces. This type of sealant is usually made of polymer materials such as rubber, resin, etc. as the main material, together with fillers and other components. Liquid sealants are usually divided into four categories: non-drying adhesive type, semi-drying viscoelasticity, dry adhesion type and dry peelable type.

Why Thermal Potting Compounds Do Not Cure?

The main function of thermal potting compound (also known as “ab glue”) is to strengthen the overall performance of electronic components, improve practicability, enhance resistance to external shocks, and achieve the purpose of safe use and enhanced service life. thermal potting compound is a liquid glue with fluidity. After normal curing, it isolates dust, moisture, moisture, etc., can withstand changes in high and low temperature, and protect components to work stably. Once it cannot be cured normally, it must be solved immediately.

The non-curing of silicone encapsulant is divided into internal and external causes. Once this type of adhesive does not cure, it will not be able to effectively play the role of waterproof, moisture-proof and insulation in electronic products.

The internal cause of the non-curing of the potting compound

The bond strength of solvent-based adhesives is affected by the amount of residual solvent in the adhesive layer. When the amount of solvent is large, although the wettability is good, the cohesive strength of the adhesive decreases because the cohesive force of the adhesive decreases. When the affinity between the adhesive polymers is large, the adhesive strength increases with the volatilization of the solvent. When there is no affinity between the two, the adhesiveness of the adhesive is relatively large when some solvent is left, and the strength decreases with the volatilization of the solvent.

The external cause of the encapsulant not curing

  1. When the two-component potting compound is proportioned, the electronic scale is not accurate enough, resulting in the incorrect content of AB agent. When the A agent is too much and the B agent content is small, it cannot be cured normally.
  2. There is no stirring before use, or there is no layering of pigments and fillers during storage, resulting in curing failure.
  3. The curing time is not long enough, and the next step is carried out in a hurry.
  4. After opening, the airtightness is not good, resulting in moisture absorption and crystallization.
  5. Changes in ambient temperature lead to changes in the curing speed and fluidity of the adhesive; if the curing temperature is too low, the adhesive cannot be cured for a long time. Especially in winter, the temperature is lower and the curing time needs to be extended.
  6. Apparent curing failure affected by the treatment of bubbles on the surface of the cured product.
  7. Light-colored cured products will change in color due to the influence of curing temperature, ultraviolet light and other conditions.
  8. Various changes in the effect of curing temperature changes on the curing properties of materials.
  9. The operators of the adhesive potting glue may not design accelerated destructive aging life experiments according to the characteristics of the glue and the needs of electrical products.
  10. The adhesive has expired. After the expiration date, it may undergo qualitative changes and cannot be used normally. Check the expiration date before using and don’t use expired products.

How to solve the problem of not curing?

  1. Regularly calibrate the electronic scale, accurately weigh the AB agent, and stir evenly.
  2. After winter, the adhesive can be preheated or cured by heating.
  3. Arrange the adhesive according to the length of the shelf life, and use up the products that are about to expire to avoid waste.
  4. Keep the working environment safe and keep away from products that will react with silicone potting compounds.
  5. Store in accordance with the instructions in the manual and maintain good ventilation conditions.

In addition, every time the silicone potting compound is used, the material should be stirred evenly. Curing is a step-by-step process that will only become stronger until the surface and interior are fully cured.

What is the difference between sealant and general-purpose sealant?

Both sealant and general-purpose sealant have bonding function. Although both are glues, they are very different. They are mainly reflected in the following aspects. Let’s take a look!

Product structure is different

Sealant: often based on dry or non-dry viscous materials such as asphalt, natural resin/rubber or synthetic resin/rubber, combined with inert materials such as carbon black, titanium dioxide and talc, and then adding curing agent, Accelerators, etc.

General-purpose sealant: the main components are water-soluble sodium silicate and acetic acid and organic silicone.

Different application areas

Sealant: The first purpose of sealant is bonding and sealing, and it is often used in the sealing of construction, transportation, electronic instruments and parts.

General-purpose sealant: mainly used for bonding glass, bonding various glass with other materials, it is the core of building materials, mainly used for waterproof and moisture-proof exterior wall, indoor bathroom anti-mildew, flame retardant, high and low temperature resistance, etc. multiple uses. It is also widely used in home decoration, such as: sanitary ware, toilets, cosmetic mirrors in the bathroom, and the back of the wooden line.

Product works differently

Sealant: easy to flow, seal, and have certain adhesiveness. It is used to fill the configuration gap to achieve a sealing effect. It has the functions of anti-leakage, waterproof, anti-vibration, sound insulation and heat insulation, and has certain anti-aging properties. It has high bonding strength and good weather resistance.

General-purpose sealant: It dries quickly, has a heavy sour taste, is not environmentally friendly, and has poor anti-aging properties, but it will not corrode objects and has strong adhesion.

Obviously, the difference between sealant and glass glue is still very big. Only by understanding the characteristics and uses of sealant and glass can we better choose the appropriate sealant or general-purpose sealant.

What is a high temperature sealant? How long does the high temperature sealant take to dry? Basic overview of high temperature sealant

Basic overview of high temperature sealants

High temperature sealant, as the name suggests, is used for bonding and sealing protection in the environment under high temperature conditions. It is a one-component silicone paste sealant, industrial use, high-quality sealing compound, suitable for smooth and flat sealing surface ( Butt joints) with high temperature and pressure conditions.

Silicone high temperature sealant is a high temperature sealing adhesive made of organic silica gel as the main body, defoamer, leveling agent, curing agent and other polymer materials.

The limit of high temperature resistance of sealant

  1. High temperature resistant sealant is a high temperature resistant silicone sealant, which can be continuously maintained at -65°C without affecting performance. It can withstand high temperature intermittently, has long-lasting elasticity, good high temperature sealing function and high electrical insulation function , Excellent anti-oil, anti-grease and anti-vibration properties, it is a special colloid that has strong interstitial ability, wide operating temperature range, high pressure resistance, corrosion resistance and oil-carrying conditions.
  2. A variety of special additives are added to the high temperature-resistant sealant, and the inorganic structural adhesive with high temperature resistance to 538 ℃ is prepared by mixing. Drops or shortens due to changes in heat and cold.
  3. The fully cured silicone sealant can continue to be useful when the temperature reaches 204°C (400oF), but when the temperature is as high as 218°C (428oF), the useful time will be shortened.
  4. It is a silicone structural sealant, and its construction temperature range should be controlled between 5-40 °C. After full curing, its useful temperature should be kept at 204 degrees, and its useful life will be shortened when it exceeds 218 degrees.
  5. The high temperature sealant can be used in the temperature range of -55℃ to 200℃, and the higher temperature should not exceed 250℃ in a short time.

How long does the high temperature sealant take to dry?

  1. Sticking time

Different properties of silicone surface dry time and curing time are not the same. Acid glue, neutral transparent glue should generally be 10 minutes, neutral variegated glue should generally be 30 minutes.

  1. Curing time

(1) The curing time of the high temperature sealant increases with the increase of the bonding thickness. For example, the acid sealant with a thickness of 12 mm may take 3 to 4 days to fully solidify, but in this process, it is generally 24 hours The inner 3mm outer layer is cured.

(2) If the place where the sealant is used is partially or completely closed, the curing time is determined by the tightness of the seal. In an absolutely airtight place, it is possible to remain uncured forever.

How to use high temperature sealant

  1. Put the rubber nozzle on the hose, and then cut the nozzle obliquely;
  2. Clean the surface of the product material, and apply glue on the bonding and sealing position of the product;
  3. Aim at the bonding part and paste it, and press it to fit tightly;
  4. The initial positioning time is about 15-30 minutes, and the test is done after 24 hours.

What should I pay attention to when using high temperature sealant?

  1. The bonding surface should be kept dry and tidy, and there should be no residue of dust or oil.
  2. Cut the beak according to the actual needs, try not to cut it as large as possible, so as to avoid waste.
  3. The adhesive layer needs to be scraped flat before the surface is dry. Once cured, it will not be able to be scraped.
  4. After the sealant is completely cured, cut off the excess part directly with a blade.

Some industries do not have special requirements for the temperature resistance of sealants, and ordinary sealants can be selected. If the temperature of the working environment is too high, ordinary products cannot resist high temperature, and high temperature sealant can be used. It can be used for a long time at high temperature and will not be easily melted.

What is a potting compound? What are the benefits of pouring potting glue for electronic products?

Potting compound is to pour the liquid resin compound into the device equipped with electronic components and circuits by mechanical or manual methods, and solidify it into a thermosetting polymer insulating material with excellent performance under normal temperature or heating conditions.

Potting glue is used for bonding, sealing, potting and coating protection of electronic components. The potting glue is liquid before curing and has fluidity. The viscosity of the glue varies according to the material, performance and production process of the product. The potting compound can realize its use value only after it is completely cured. There are many types of electronic potting adhesives. According to the material type, there are mainly three types of the most commonly used ones, namely epoxy resin potting adhesive, silicone resin potting adhesive, and polyurethane potting adhesive. These three materials Potting glue can be subdivided into hundreds of different products. Potting glue has been widely used in the electronic device manufacturing industry and is an indispensable and important insulating material in the electronic industry.

With the rapid development of electronic products, the precision of electronic products is also constantly improving. In order to reduce the failure of electronic products and improve the service life of electronic products, manufacturers will pour electronic potting glue into electronic products. What are the benefits of encapsulation for electronic products?

  1. Drop resistance: If an electronic product is dropped, it is likely to cause the electronic product to be reimbursed. Electronic products use electronic potting glue, which can increase the elasticity of electronic products and improve the anti-drop performance of electronic products.
  2. Water resistance: Electronic products filled with electronic potting glue have better waterproof function. Even if the electronic product slips into the water, it can prevent moisture from invading the main board of the electronic product, preventing water from entering the interior and damaging the battery, memory, main board, etc.
  3. Seismic performance: Some electronic products are used together in environments with a high vibration ratio. Electronic potting glue has good elasticity, and pouring electronic potting glue can effectively improve the seismic performance of electronic products. In a relatively large vibration environment, electronic products still maintain good performance.
  4. Extend the service life: Electronic potting glue not only has waterproof function, but also has the functions of heat conduction, dustproof and heat dissipation, so as to ensure that electronic products can adapt to various use environments.

What is the above-mentioned potting glue? What are the benefits of pouring potting glue for electronic products? If you have a demand for potting glue, you can contact the online customer service of CoolThermo potting glue official website for the latest information and quotation!

Language »