Electronic paste is a general term for paste-like or fluid electronic materials. It is typically applied through screen printing, inkjet printing, আবরণ, pad printing, or 3D printing. The paste is deposited on substrates such as ceramics, glass, polymer films, silicon wafers, or metal bases. After sintering or curing, it forms functional films or patterns.
It is widely used in thick-film circuits, MLCCs, multilayer chip inductors, photovoltaic cells, semiconductor packaging, display devices, and sensors. The paste carries multiple roles such as conductivity, resistance adjustment, dielectric, protection, and transparent conduction.
At first glance, electronic paste looks like a sticky mass. In essence, it is a multiphase composite system. It usually consists of functional powders, binders, and organic carriers.
In most thick-film pastes, this system specifically includes functional powders, glass powders, and organic carriers. Functional powders determine electrical performance. Glass powders provide structural stability and adhesion. Organic carriers ensure process adaptability. The three components are distinct in roles yet interdependent. Together, they define the final performance of the paste.
In some special cases, glass powders may be absent. Instead, resins or self-sintering metals are used as structural components.
Functional Powder – The Core That Defines Function
In electronic paste, the role of functional powders is to provide electrical properties. The powder type directly determines the paste function in the device. It defines whether the paste conducts, resists, insulates, or transmits light while conducting.
- Conductive paste: Metals such as silver (Ag), copper (Cu), nickel (Ni), or silver-coated copper. They form conductive paths and serve as electrodes.
- Resistive paste: Oxide powders such as ruthenium oxide (RuO₂) or rhodium oxide (RhO₂). They provide controlled resistance.
- Dielectric paste: Powders such as barium titanate (BaTiO₃) or barium strontium titanate (BST). They ensure insulation and charge storage.
- Transparent conductive paste: ITO (indium tin oxide), silver nanowires, or graphene. They allow electrical conduction while maintaining light transmission.
Glass Powder – The “Binder” and “Structural Regulator”
In the paste formula, glass powder is not the star but plays a decisive role. During sintering, it softens and flows. It finally solidifies with the substrate and powders. Glass powder serves as both binder and structural regulator.
Its main roles include:
- Adhesion: Glass softens at high temperature and bonds metals or oxides to ceramic, glass, or silicon substrates. Without it, electrodes may peel off.
- Densification: Its flow fills voids between particles. This increases film density and improves electrical stability.
- Thermal expansion matching: Adjusting glass composition makes its expansion coefficient closer to that of the substrate. This reduces stress and prevents cracks or warping.
Functional powders define electrical properties. Glass powders ensure that these properties remain stable and long-lasting.
Note: Transparent conductive pastes used on glass, PET, or PI substrates often rely on polymers such as epoxy, acrylic, or PU as binders. They cure at low or even room temperature without glass powders.
Main glass systems in electronic pastes
| Glass Type | Representative System | Glass Softening Point (°C) | রাসায়নিক স্থিতিশীলতা | Coefficient of Thermal Expansion (10°C-1) | সুবিধাদি | অসুবিধা |
| Lead glass | Pb0-Si0,、Pb0-B,0:-Si0.PbO-Zn0-B,0:-Si0,等 | 350-600 | Good stability | 70-120 | High resistance, low dielectric loss, low softening temperature, and good chemical stability. | Easily oxidizable AIN ceramics pose significant risks to humans and the environment. |
| Bismuthate glass | Bi,0;-B,0,-Si0₂、BizO:-B₂0:-BaOBi,0:-Zn0-Si0.Bi,0:-B,0:-Zn0.BizO:-Si0z-Sb,Os等 | 350-500 | Good stability | 90-150 | High bismuth oxides, similar to lead glass, have a low softening temperature and good chemical stability. | Easily oxidizable AIN ceramics are costly, prone to bismuth precipitation, and have poor acid resistance. |
| Borate glass | Ba0-B,0:-Si0?Ca0-B,0:-Si0,-Ba0.Si0,-B,0;-AlO;-RO 等 | 300-600 | Not very stable | 90-150 | Low melting point can only be achieved by adding alkali metal, alkaline earth metal glass, or heavy metal ions. | They are chemically unstable, generally have a high coefficient of thermal expansion, and are prone to phase separation. |
| Zinc glass | Zn0-B,0;-Si0.Zn0-Ba0-B,0:Zn0-B,0:-Al0:-Si0,等 | 450-600 | Good stability | 60-90 | They offer stable chemical properties, a low thermal expansion coefficient, high bonding strength, and a low melting point. | They also have poor solderability and poor high-temperature fluxing properties. |
Organic Carrier – The Key to Process Control
The organic carrier is a mixture of solvents (65–98% by weight), thickeners, thixotropic agents, surfactants, and flow modifiers. At minimum, it contains organic solvent and thickener. Common solvents include diethylene glycol ether acetate, tributyl citrate, and dibutyl phthalate.
Although carriers do not contribute to electrical functions, they control processability. They define rheology and initial adhesion to substrates.
The recent trend is toward low-residue, low-odor, and environmentally friendly carriers. Some products even adopt water-based or inorganic colloid systems to meet green manufacturing requirements.
উপসংহার
Functional powders give electronic paste its electrical properties. Glass powders secure these properties in a stable and durable form. Organic carriers ensure processability during fabrication. The three parts are clearly divided in function but interdependent. Together, they form a balanced multiphase system.