I. Introduction

One of the most important parameters and starting points for the development of epoxy resin formulations is the epoxy resin curing mechanism and the selection of the specific curing agent to be used. Dicyandiamide is one of the most widely used catalysts for curing one-component epoxy adhesives. This type of adhesive has a long shelf life at room temperature, but offers relatively fast curing at temperatures above 150°C. Dicyandiamide cured epoxy adhesives have a wide range of uses, especially in the transportation, general assembly and electrical/electronic markets.

II. Dicyandiamide

Dicyandiamide (also known as “dicy”) is a solid latent curing agent that reacts with both the epoxy group and the secondary hydroxyl group. This curing agent is a white crystalline powder that is easily incorporated into epoxy formulations. Figure 1 is a graphical representation of the dicyandiamide molecule.

This curing agent cures through nitrogen-containing functional groups and consumes the epoxy and hydroxyl groups in the resin. The advantage of dicyandiamide is that it reacts with the epoxy resin only when heated to the activation temperature, and the reaction stops once the heat is removed. It is widely used in epoxy resins and has a long shelf life (up to 12 months). Longer shelf life can be obtained by refrigerated storage.

Due to its delayed cure (long shelf life) and excellent properties, dicyandiamide is used in many “Class B” film adhesives. Dicyandiamide is also one of the main catalysts for one-component, high-temperature curing epoxy adhesives.

In adhesive formulations, dicyandiamide is used in quantities of 5-7 pph for liquid epoxy resins and 3-4 pph for solid epoxy resins. it is generally dispersed with epoxy resins by ball milling. Dicyandiamide forms very stable mixtures with epoxy resins at room temperature because it is insoluble at low temperatures. The particle size and distribution of the epoxy-dicyandiamide system is critical for extending its shelf life. In general, the best performance is produced when the particle size of the dicyandiamide is less than 10 microns. Fumed silica is commonly used to keep the dicyandiamide particles suspended and evenly distributed in the epoxy resin. When formulated as a one-component adhesive system, epoxy dicyandiamide is stable when stored at room temperature for six months to one year. It is then cured by exposure to 145-160°C for approximately 30-60 minutes. Because of the relatively slow reaction rate at lower temperatures, the addition of 0.2% ~ 1.0% phenyl dimethylamine (BDMA) or other tertiary amine accelerators is sometimes used to reduce the cure time or lower the cure temperature. Other common accelerators are imidazole, substituted urea and modified aromatic amines. Substituted dicyandiamide derivatives can also be used as epoxy curing agents with higher solubility and lower activation temperatures. These techniques can reduce the activation temperature of epoxy-dicyandiamide mixtures to 125°C. Dicyandiamide-cured epoxy resins have good physical properties, heat and chemical resistance. Liquid epoxy cured with 6 pph dicyandiamide has a glass transition temperature of about 120°C, while high temperature curing with aliphatic amines will provide a glass transition temperature of no greater than 85°C.

III. One-component adhesive formulations

In one-component epoxy adhesives, the curing agent and resin are compounded together as a single material through an adhesive formulation. The curing agent system is selected so that it reacts with the resin only under appropriate processing conditions. Dicyandiamide-cured epoxy resins are very brittle. Through the use of toughening agents, such as terminated carboxybutyronitrile (CTBN), it is possible to formulate very elastic and tough adhesives without sacrificing the good properties inherent in unmodified systems. With toughened dicyandiamide-cured epoxies, peel strengths are approximately 30 lb/in and tensile shear strengths are in the range of 3000-4500 psi. Toughened dicyandiamide-cured epoxy adhesives also exhibit good resistance to heat cycling. The most effective accelerators for dicyandiamide systems are probably substituted ureas because of their synergistic effect on the performance of the adhesive and their exceptionally good latent delay. It has been shown that the addition of 10 pph of substituted urea to 10 pph of dicyandiamide will produce a bisphenol- a (DGEBA) epoxy liquid diglycidyl ester binder system that cures in only 90 min at 110 °C. However, this adhesive has a shelf life of three to six weeks at room temperature. If longer curing times are acceptable, curing can even be achieved at temperatures as low as 85°C.

A dielectric is any insulating medium between two conductors. Simply put, it is non-conductive material. Dielectric materials are used to make capacitors, to provide an insulating barrier between two conductors (e.g., in crossover and multilayer circuits), and to encapsulate circuits.

Dielectric Properties

Epoxy resin usually has the following four dielectric properties:VR, Dk, Df and dielectric strength.

• Volume resistivity (VR): It is defined as the resistance measured through the material when a voltage is applied for a specific period of time. According to ASTM D257, for insulation products, it is usually greater than or equal to 0.1 tera ohm-meter at 25°C and greater than or equal to 1.0 mega ohm-meter at 125°C.
• Dielectric constant (Dk): it is defined as the ability of the material to store charge when used as a capacitor dielectric. According to ASTM D150, it is usually less than or equal to 6.0 at 1KHz and 1MHz, and is a dimensionless value because it is measured as a ratio.
• The dissipation factor (Df) (also known as the loss factor or dielectric loss): defined as the power dissipated by the medium, usually less than or equal to 0.03 at 1KHz, less than or equal to 0.05 at 1MHz.
• Dielectric strength (sometimes called breakdown voltage): is the maximum electric field that the material can withstand before breakdown. This is an important characteristic for many applications that require running high currents or amperages. As a general rule of thumb, the dielectric strength of epoxy resins is about 500 volts per mil at 23°C for insulating products. As a practical example, if an electronic circuit needs to resist 1000 volts, a minimum of 2 mils of dielectric epoxy is required.

Volume resistivity, dielectric constant, and dissipation factor can be determined experimentally by the adhesive manufacturer; however, dielectric strength depends on the application. Users of epoxy resins should always verify the dielectric strength of the adhesive for their particular application.

Variability of dielectric properties

Many dielectric properties will vary with factors unrelated to the properties of the host material, such as: temperature, frequency, sample size, sample thickness and time. Some external factors and how they affect the final results.

• VR and Temperature

As the temperature of the material increases, the VR decreases. In other words, it is no longer an insulator. The main reason for this is that the material is above its glass transition temperature (Tg) and the molecular motion of the monomers entangled in the polymer network is at its highest level. This not only means lower insulation compared to room temperature, but also leads to lower strength and sealing.

•  Dk and temperature

The dielectric constant of room temperature cured epoxy resins increases with temperature. For example, the value is 3.49 at 25°C, becomes 4.55 at 100°C, and 5.8 at 150°C. In general, the higher the value of Dk, the less electrically insulating the material is.

• Dk and frequency (Rf) 

In general, Dk decreases with increasing frequency. As described in the effect of temperature on Dk, room temperature cured epoxy resin has a Dk value of 3.49 at 60Hz, a Dk value of 3.25 at 1KHz and a Dk value of 3.33 at 1MHz.

In other words, as Rf increases, the insulating properties of the adhesive increase. Therefore, the lower the Dk value, the more the material acts like an insulator.

 Common Applications

Dielectric adhesives are used in most semiconductor and electronic packaging applications. Some examples include: semiconductor flip chip underfill, SMD placement on PCBs and substrates, wafer passivation, spherical tops for ICs, copper ring dipping and general PCB potting and encapsulation. All of these areas require maximum insulation to eliminate and prevent any electrical shorts.

 Insulation Products

Epoxy Technologies offers a wide range of products for dielectric applications that have structural, optical and thermal properties as well as good dielectric properties. All dielectric products are electrical insulators, but many are also heat conductors.

In the front-end-of-line (FEOL) processes of semiconductor manufacturing, wafers undergo various processing steps, particularly being heated to a specific temperature with strict requirements, as temperature uniformity has a crucial impact on product yield. Additionally, semiconductor equipment must operate in environments where vacuum, plasma, and chemical gases are present, which necessitates the use of ceramic heaters. Ceramic heaters are critical components in semiconductor thin-film deposition equipment, applied in process chambers where they directly contact the wafer, providing stable and uniform process temperatures and enabling high-precision reactions on the wafer surface to form thin films.

Ceramic heaters, due to their involvement with high temperatures, typically use ceramic materials based primarily on aluminum nitride (AlN). This is because aluminum nitride has electrical insulating properties and is an excellent thermal conductivity ceramic material. Additionally, its coefficient of thermal expansion is close to that of silicon, and it possesses excellent plasma resistance, making it highly suitable for use as a component in semiconductor equipment.

Basic structure of the heater

The ceramic heater consists of a ceramic base that supports the wafer and a cylindrical support body on the back that provides support. Inside or on the surface of the ceramic base, there are not only heating elements (heating layer) for heating, but also RF electrodes (RF layer). To achieve rapid heating and cooling, the thickness of the ceramic base needs to be thin, but making it too thin would reduce its rigidity. The support body of the heater is typically made of a material with a coefficient of thermal expansion similar to that of the base, which is why the support body is often made of aluminum nitride. The heater adopts a unique shaft structure to join the bottom, which protects the terminals and wires from the effects of plasma and corrosive chemical gases. The support body is equipped with gas inlet and outlet channels for thermal conduction, ensuring uniform temperature distribution across the heater. The base and the support body are chemically bonded together with a bonding layer.

The ceramic heater base contains embedded resistive heating elements. These elements are formed by using a screen-printing method with conductor paste (such as tungsten, molybdenum, or tantalum) to create spiral or concentric circular circuit patterns. Alternatively, metal wires, metal meshes, or metal foils can also be used. In the screen-printing process, two ceramic plates with the same shape are prepared, and conductor paste is applied to the surface of one of them. The paste is then sintered to form the resistive heating element. The second ceramic plate is then used to sandwich the resistive heating element, completing the process of embedding the resistive element within the base.

When preparing thin films using Plasma-Enhanced Chemical Vapor Deposition (PECVD) equipment, the main factors affecting film uniformity and thickness are the plasma characteristics and process temperature. First, the density and distribution of the plasma directly affect the uniformity of the film and the deposition rate. A uniformly distributed plasma ensures that the reactive gases fully react on the substrate surface, forming a uniform film. The uniformity of the plasma distribution is closely related to the RF Mesh embedded in the heater. Secondly, a specific process temperature ensures excellent thermal uniformity. The ceramic heater ensures that the wafer surface temperature fluctuates within ±1.0%. For example, heaters produced by NGK Insulator in Japan have a temperature fluctuation of less than 0.1%, which is considered an excellent performance indicator.

When manufacturing ceramic heaters, there are also requirements for high purity of aluminum nitride (AlN) materials. Slight changes in composition can alter the color of the heater under certain conditions, and may also change the electrical properties of the heater. Naturally, this also affects the characteristics of the coupled plasma. In addition, the density, thermal conductivity, and bulk resistivity of the aluminum nitride material all influence the performance of the heater.

Literature indicates that the bulk resistivity of the heater at 500°C needs to be within the range of 5.0E+9 to 1.0E+10 Ω·cm, and at temperatures between 600°C and 700°C, the bulk resistivity should be within the range of 1.0E+8 to 1.0E+9 Ω·cm. The bulk resistivity of typical aluminum nitride ceramic heaters tends to decrease rapidly starting from 500°C, which can lead to leakage current.

According to a market research report, the global market size for aluminum nitride ceramic heaters for semiconductors was $33 million in 2022, and it is expected to reach $78.53 million by 2031, with a compound annual growth rate (CAGR) of 10% during the forecast period. Major manufacturers of aluminum nitride ceramic heaters for semiconductors include NGK Insulator, MiCo Ceramics, Boboo Hi-Tech, AMAT, Sumitomo Electric, CoorsTek, Semixicon LLC, and others. In 2023, the top five companies accounted for approximately 91.0% of the market share. In terms of product types, 8-inch heaters currently dominate the market, accounting for about 45.9% of the share. In terms of application, chemical vapor deposition (CVD) equipment is the primary demand source, accounting for approximately 73.7% of the share.

Aluminum nitride crystals, when used as a substrate material, demonstrate unique advantages in the semiconductor manufacturing field, directly impacting the performance and reliability of final electronic devices. Below is a detailed analysis of the advantages of aluminum nitride crystals as a substrate material:

High Thermal Conductivity Ceramic Material and Heat Dissipation Performance:
Aluminum nitride has extremely high thermal conductivity, making it an ideal choice for heat dissipation. In high-temperature operating environments, its high thermal conductivity can quickly transfer heat away from the device, effectively reducing operating temperatures. This is crucial for high-power electronic devices such as high-frequency power amplifiers and lasers, significantly improving their stability and lifespan.

Lattice Matching and Low Defect Growth:
The lattice constants and thermal expansion coefficients of AlN are closely matched with those of III-nitride materials (such as GaN), meaning that epitaxial growth on these materials can reduce lattice mismatch, which in turn minimizes dislocations and lowers defect density in the device. Dislocations are key factors affecting the performance of semiconductor devices. Reducing dislocations enhances the efficiency and reliability of devices, particularly in applications like LEDs, laser diodes, and microwave electronics.

Dielectric Properties for High-Frequency Applications:
Aluminum nitride has a low dielectric constant, making it an excellent material for high-frequency circuits by reducing signal loss during transmission. This is especially important for high-frequency communication devices and radar systems. The low dielectric constant helps improve device operating frequencies and enables more efficient signal processing.

Preferred Material for Ultraviolet Optoelectronic Devices:
With a wide bandgap of 6.2 eV, aluminum nitride has high transparency in the ultraviolet (UV) region, making it an ideal substrate for the fabrication of ultraviolet LEDs, lasers, and detectors. This property allows AlN-based devices to play a key role in applications such as UV blind detection, UV curing, sterilization, and optical communication.

High-Temperature and Chemical Stability:
Aluminum nitride crystals maintain excellent physical and chemical stability at high temperatures, allowing them to withstand extreme temperatures without undergoing structural changes. This is crucial for high-temperature electronic devices and applications that require thermal shock resistance. Furthermore, its chemical stability makes it resistant to environmental corrosion, making it suitable for use in harsh environments.

Piezoelectric Properties and Acoustic Applications:
AlN exhibits piezoelectric effects, making it an ideal material for the manufacture of surface acoustic wave (SAW) devices. These devices are widely used in filters, sensors, and wireless communication systems, utilizing their acoustic properties for high-performance signal processing.

Environmental Friendliness and Sustainability:
Compared to some traditional substrate materials, aluminum nitride is non-toxic and environmentally friendly, aligning with the growing demand for eco-friendly materials. This makes it an attractive option for sustainable technology development.

In summary, aluminum nitride crystals, as a substrate material, provide a solid foundation for the development of high-performance electronic and optoelectronic devices through their excellent heat management capabilities, compatibility with III-nitride materials, superior optical and electrical properties, and stability under extreme conditions. These advantages drive advancements in related technologies and expand their application fields.

Polyacrylamide (PAM) is a polymer commonly used in various industrial and environmental applications. It can exist in different ionic states based on the type of ions associated with the polymer backbone. The two main forms of polyacrylamide based on ionic charge are anionic polyacrylamide (APAM) and cationic polyacrylamide (CPAM). Here are the key differences between the two:

1. Ionic Charge:

   - APAM: Anionic polyacrylamide carries a negative charge on its polymer backbone due to the presence of anionic functional groups, such as carboxylate (-COO-) or sulfonate (-SO3-) groups. These groups dissociate in water, resulting in negatively charged polymer chains.

   - CPAM: Cationic polyacrylamide possesses a positive charge on its polymer backbone due to the presence of cationic functional groups, such as amino (-NH2) or quaternary ammonium groups (-N+(CH3)3). These groups dissociate in water, resulting in positively charged polymer chains.

2. Applications:

   - APAM: Anionic polyacrylamide is primarily used in applications where flocculation, clarification, and sedimentation of negatively charged particles or suspended solids are required. It is commonly utilized in wastewater treatment, sludge dewatering, mining, and oil field applications.

   - CPAM: Cationic polyacrylamide is used when flocculation and solid-liquid separation of positively charged particles or suspended solids are necessary. It is often employed in industries like papermaking, textile, water treatment, and as a retention aid in paper manufacturing.

3. Flocculation Mechanism:

   - APAM: Anionic polyacrylamide interacts with the negatively charged particles or colloids in the suspension through electrostatic attraction. The negative charges on the APAM polymer chains attract and neutralize the particles, resulting in the formation of larger flocs and aiding in their sedimentation or removal.

   - CPAM: Cationic polyacrylamide interacts with the positively charged particles or colloids in the suspension through electrostatic attraction. The positive charges on the CPAM polymer chains attract and neutralize the particles, leading to the formation of larger flocs and facilitating their settling or separation.

4. Efficiency in Different pH Ranges:

   - APAM: Anionic polyacrylamide is more effective in neutral to alkaline pH ranges (pH 6-10), where the negative charge on the polymer remains stable.

   - CPAM: Cationic polyacrylamide is more efficient in acidic to neutral pH ranges (pH 4-8), where the positive charge on the polymer remains stable.

It's important to note that there are also non-ionic polyacrylamides that carry no ionic charge. These non-ionic PAMs are often used for applications such as lubrication, friction reduction, and enhanced recovery.

——Manufactured by Yangchen Tech Factory

1. What is the chemical composition of the copolymer?

The product is a styrene-N-phenylmaleimide-maleic anhydride copolymer, which combines:

• Styrene for improved impact strength and processability.
• N-phenylmaleimide (N-PMI) for enhanced heat resistance.
• Maleic anhydride (MAH) for excellent adhesion and chemical reactivity.

2. What are the key properties of this copolymer?

• Heat Resistance: Superior thermal stability due to N-phenylmaleimide.
• Good Solubility: Facilitates easy blending with resins.
• Excellent Adhesion: Functional groups improve compatibility with substrates like ABS and PVC.
• Versatile Modifier: Ideal for heat-resistant applications in engineering plastics and adhesives.

3. What are the common applications?

• ABS Heat-Resistant Modifier: Enhances thermal stability and mechanical strength in ABS resins.
• PVC Modifications: Improves rigidity and thermal properties in PVC materials.
• Adhesives: Provides better bonding strength and heat resistance.
• Engineering Plastics: Acts as a key performance enhancer for polycarbonate, acrylic, and other advanced materials.

4. What industries use this product?

• Automotive manufacturing.
• Electronics and electrical applications.
• High-performance adhesives.
• Construction materials.
• Packaging solutions.

5. What are the available product specifications?

• Appearance: White or light yellow powder/granules.
• Packaging: Customizable packaging (standard: 25 kg bags).
• CAS Number: Provided upon request.

6. How does it enhance ABS resin properties?

• Improves heat distortion temperature (HDT).
• Boosts mechanical strength and dimensional stability.
• Enhances weatherability and chemical resistance.

7. Is the product customizable?

Yes, Yangchen Tech specializes in providing customized solutions to meet client-specific requirements, including tailored formulations for unique applications.

8. What are the storage and handling recommendations?

• Store in a cool, dry, and ventilated environment.
• Avoid exposure to moisture and direct sunlight.
• Use protective gear during handling to prevent inhalation of dust.

9. Does Yangchen Tech provide technical support?

Yes, we offer comprehensive technical consultation to assist in optimizing product usage for your applications.

10. How can I place an order or request samples?

You can:

• Visit our official website for inquiries and order placement.
• Contact our sales team directly for product details, pricing, and samples.

For additional information, please feel free to contact Yangchen Tech Factory. Let us assist you in finding the perfect solution for your material needs!

Hot melt adhesive is solvent-free, almost odorless, pollution-free, and easy to apply, so it is widely used in many fields. Hot melt adhesive with ethylene-vinyl acetate random copolymer (EVA) as the base resin is one of the most important varieties of hot melt adhesive, which can be used in packaging materials, book binding, wood processing and other industries.

The development of EVA hot melt adhesive in my country began in the early 1970s. In the 1980s, due to the rapid development of related industries and industries such as printing, food and beverage, wood processing, and electronics, various production lines were introduced to stimulate the rapid growth of new product development and production capacity of EVA hot melt adhesive. EVA hot melt adhesive is mainly used in the following fields in my country.

1 Book binding

EVA hot melt adhesive is used for wireless binding, which changes the cumbersome processes of threading round backs, gluing, and covering the cover used in the past for binding books with latex, greatly shortening the book publishing cycle and improving work efficiency and book binding quality.

2 Wood processing

In wood processing, EVA hot melt adhesive is mainly used in combination with panel furniture edge banding machines for furniture edge banding, which has changed the backward appearance of manual operation in the past, and is easy to fold and assemble, which improves labor efficiency.

3. Clothing lining

EVA and EVAL powders are inexpensive and have good adhesion. They are suitable for various coating processes such as powder coating, powder dot coating, and slurry coating. The hot melt lining made of EVA hot melt adhesive can make the clothing beautiful, crisp, non-deformed, and low-cost.

4 Packaging

The bonding ability of EVA hot melt adhesive is relatively stable, not affected by changes in temperature and humidity in the working environment, and eliminates the inherent gluing and peeling problems of packaging machinery. Therefore, EVA hot melt adhesive can be used in the packaging industry in the fields of cardboard and cardboard boxes, cement bags, labeling, food packaging, protective packaging, and packaging container sealing.

EVA hot melt adhesive is also used in the manufacture of electrical appliances such as televisions, air conditioners, refrigerators, as well as the shoemaking industry, PET blow molding bottles, cigarette filter winding, outer packaging tear strips, cable joint sealing, oil pipeline anti-corrosion and other fields.

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ElephChem Holding Limited, professional market expert in Polyvinyl Alcohol(PVA) and Vinyl Acetate–ethylene Copolymer Emulsion(VAE) with strong recognition and excellent plant facilities of international standards.