Definition
A laboratory glue applicator is a precision device used to prepare uniform and controllable thickness coatings on the surface of substrates. It mechanically or automatedly coats adhesives, photoresists, pastes, or other liquid functional materials to substrates such as glass, silicon wafers, metals, or polymers to meet experimental needs such as subsequent curing, bonding, lithography, or functional testing. The equipment plays a key role in research and development in the fields of materials science, electronics manufacturing, optical coatings, and new energy.
How it works:
The core working principle of a laboratory glue applicator is based on a combination of fluid dynamics and precision motion control. Common operating modes include rotary coating and scraper coating. In rotary coating, the substrate is vacuum-adsorbed on the rotating table, and after the adhesive droplets are added to the center of the substrate, the adhesive is diffused to the edge through the centrifugal force generated by high-speed rotation, and the solvent volatilizes to form a uniform film. The film thickness h can be approximately described by the following formula:
h = k · (η/ω²)1/2
where η represents the viscosity of the glue, ω is the angular velocity of rotation, and k is the constant related to the properties of the glue. Scraper coating is applied evenly to the surface of the substrate through a squeegee with adjustable gap, and the thickness is directly determined by the gap between the squeegee and the substrate.
Measurement method
The evaluation of adhesive quality mainly focuses on coating thickness and uniformity. Non-contact methods are often used for thickness measurement, such as ellipsometer calculating the thickness and refractive index by analyzing the reflection characteristics of polarized light on the coating surface. The white light interferometer measures the film thickness by using the change of optical interference fringes. The step meter uses a probe to scan the height difference of the coating step for contact measurement. Uniformity can be assessed by calculating thickness standard deviation or thickness distribution charts after multi-point thickness measurements. The measurement process should refer to relevant industry standards, such as SEMI guidelines for semiconductor processes or ASTM related coating test standards.
Influencing factors
The quality of the coating is affected by multiple factors. In terms of adhesive properties, viscosity, surface tension, solids content and solvent volatilization rate directly affect the spreading and film formation behavior. In the process parameters, the rotation speed curve of rotary coating (including the initial low-speed spreading and high-speed homogenization stage), acceleration, rotation time, and ambient temperature and humidity all play a key role in the thickness uniformity. The equipment factors include the dynamic balance accuracy of the rotary table, the stability of vacuum adsorption and the parallelism of the scraper. The surface energy, roughness, and cleanliness of the substrate can also change the wetting properties of the adhesive, which in turn affects the quality of the coating.
Applications:
Laboratory gluing machines are widely used in various industrial and scientific research fields. In microelectronics and semiconductor research, it is used for photoresist coating for circuit patterning. In the photovoltaic sector, conductive pastes or passivation coatings are used to prepare solar cells. In optical experiments, functional coatings such as reflection enhancement film and reflective film are coated. In adhesive research, it is used to prepare standard adhesive specimens to test bonding properties. In addition, in the research and development of flexible electronics, display technology, biosensors and packaging materials, glue applicators also provide a basic platform for the development of new coating processes.
Selection considerations
When choosing a laboratory glue applicator, it is necessary to comprehensively evaluate the technical requirements and experimental conditions. First of all, the coating method is clear: rotary glue coating is suitable for uniform coating of small substrates and thin layers; Squeegee gluing is more suitable for high-viscosity materials or large substrates. In terms of equipment accuracy, pay attention to the speed control range and stability, the reliability of the vacuum adsorption system and the program control function. Compatibility considers the substrate size range, material resistance (e.g., chemical resistance), and integration capabilities with peripherals such as glove boxes. In terms of safety and ease of use, the protection design, cleaning convenience and software operation logic are examined. Finally, the decision was made with reference to the technical indicators and verification data recognized by the industry, combined with the repeatability requirements of specific experimental scenarios.