Electronic paste is a general term for electronic material products in paste or fluid form. They are typically applied onto substrates such as ceramics, glass, polymer films, silicon wafers, and metal bases via screen printing, inkjet printing, coating, pad printing, or 3D printing. After sintering or curing, they form functional layers or patterns. It’s widely used in thick-film circuits, MLCCs, multilayer chip inductors, photovoltaic cells, semiconductor packaging, display devices, and sensors. These pastes serve various functions including conduction, resistance adjustment, dielectric properties, protection, and transparent conduction. They are a key material system for achieving high performance and reliability in modern electronic components.
While electronic paste may resemble a simple “paste” in appearance, it is essentially a multi-phase composite system, typically composed of three parts: functional powder, binder, and organic vehicle. In most thick-film pastes, this system specifically consists of three main components: functional powder, glass frit, and organic vehicle. The functional powder determines the electrical properties, the glass frit ensures structural stability and adhesion, and the organic vehicle enables process adaptability. These three components have distinct roles yet are interdependent, collectively determining the final performance of the paste. It is worth noting that in some special applications, alternative systems exist that may omit glass frit, using resins instead or relying on metal self-sintering.
Functional Powder
In electronic pastes, the functional powder provides the required electrical characteristics. The type of powder selected directly determines the role the paste will play in the device. It acts as a conductor, resistor, dielectric, or transparent conductor. In short, the functional powder dictates the ultimate function of the electronic paste. Common types of functional powders in electronic pastes include:
Glass Frit
Although not the “star” component in electronic paste formulations, glass frit plays a critically supportive role. During the sintering process, it softens, flows, and ultimately consolidates together with the substrate and functional powder, serving a dual role as a “binder” and “structure modifier.” Its main functions are:
① Adhesive Bonding: The softened glass at high temperatures effectively “welds” the metal or oxide powders firmly to the surface of ceramics, glass, or silicon wafers. Lack of glass frit can lead to insufficient adhesion or even peeling of the electrode.
② Densification: The flowability of glass helps fill pores between particles, increasing the density and integrity of the fired layer, thereby improving electrical stability.
③ Thermal Expansion Matching: By adjusting the glass composition, its coefficient of thermal expansion (CTE) can be matched to that of the substrate, buffering stress and reducing the risk of cracking or warping after sintering.
If the functional powder determines the electrical performance of the electronic paste, the glass frit determines whether these properties can exist “firmly and durably.” The main glass systems used in electronic pastes are as follows:
Glass Systems in Electronic Pastes
Note: Transparent conductive pastes, often used on glass substrates, PET, PI, and other transparent/flexible substrates, more commonly rely on polymers (such as epoxy, acrylic resin, PU, etc.) as the binder phase instead of glass frit, curing at low temperatures or even room temperature.
Organic Vehicle
The organic vehicle consists of an organic solvent. It’s comprising approximately 65% to 98% of the vehicle’s total weight. Common examples include diethylene glycol monoethyl ether acetate, tributyl citrate, tributyl phthalate, etc.), thickeners, thixotropic agents, surfactants, and leveling agents. At a minimum, a vehicle includes an organic solvent and a thickener.
Although the organic vehicle does not contribute to the electrical function of the final fired layer, it determines the processability of the paste during preparation. Its fundamental role is to provide the paste with the rheological properties suitable for different application processes and initial adhesion to the substrate. In recent years, the trend in organic vehicle development has been towards low residue, low odor, and environmental friendliness. Some products even attempt to use water-based or inorganic colloidal systems to meet the demands of green manufacturing.
Resumo
The functional powder provides the required electrical properties for the electronic paste. The glass frit ensures these properties remain stable and durable. Last, the organic vehicle guarantees the processability of the paste during manufacturing. These three components have clear divisions of labor yet are interdependent, forming a balanced multi-phase system.
The application of air jet mills and classificador mills is indeed highly suitable for preparing the functional powders and glass frits used in electronic pastes. For functional metal powders like silver, copper, or nickel, air jet milling provides an contamination-free method. It can achieve the precise particle size distribution (PSD) and spherical morphology critical for ensuring high conductivity and printability. Similarly, classifier mills excel in processing brittle materials like glass frits. The controlled fracturing can yield a consistent, fine powder with the specific surface area necessary for optimal sintering activity and binding strength. The ability to precisely control top cut size and distribution width through integrated classificação is vital. These parameters directly influence paste rheology, sintering density, and ultimately, the performance of the fired electronic film.
Pó épico
No Maquinário de Pó Épico, we specialize in providing tailored grinding and classification solutions. Our range of air jet mills and classifier mills is designed to deliver the precise particle characteristics essential for high-performance electronic pastes. Contact us to learn how our expertise can help you optimize your powder production process.
