Conductive paste is a high-concentration multi-phase suspension dispersion system composed of conductive filler (usually metal powder), binder phase, solvent and auxiliary agent. It is used to prepare conductive wiring on different substrates by screen printing or other printing techniques Or thick-film electronic materials with surface electrodes are widely used in various thick-film electronic components, sensitive components, touch screens, radio frequency identification tags (RFID), solar cells, membrane switches, flexible circuits and other fields.
The conductive paste is an intermediate product, which needs to be screen-printed into a wet film according to the designed pattern and then undergo a certain curing process to obtain the final conductive film layer. An ideal conductive film should have two main characteristics: one is that the geometry and thickness of the film are strictly controllable; the other is that the resistance of the film (usually expressed in square resistance) is as small as possible.
The conductive film layer is solid (without volatile organic compounds), and its square resistance is affected by the properties of the components in the film layer, including the volume fraction and morphology of the binder (resin) and the functional phase (such as silver powder) , Size, distribution and interface, etc. In contrast, the theory and practice of the relationship between the composition, structure and performance of multiphase solid materials can be used to guide their research. The strict control of the geometric shape and thickness of the conductive film layer mainly depends on the good screen printing characteristics of the conductive paste. In other words, the conductive paste has good screen printing properties, that is, the paste obtains a strictly controllable geometric shape and thickness of the film through screen printing. The so-called conductive paste with good screen printing characteristics is a qualitative description. The various physical and chemical phenomena in the process of screen printing the conductive paste into a wet film pattern should be decomposed and analyzed to find the quantification that affects the conductive paste screen printing characteristics Parameters can guide the research of conductive paste and evaluate its performance.
The physical phenomena of the conductive paste in each stage of the storage, screen printing, film formation (wet film) and curing process are different, and the paste is required to have specific rheological properties. In fact, the quality of the film, especially the geometric dimensions such as the thickness and width of the film, are closely related to the rheological properties. Similarly, various undesirable performances of the film, such as film widening, edge “screeding”, flying ink, burrs, local expansion, etc. can also be analyzed from the rheological characteristics of the conductive paste. Simulating the rheological properties of the conductive paste under specific conditions through appropriate rheological parameters can provide a basis for the formulation design of the conductive paste and the selection of the screen printing process.
Conductive paste is also a major type of product for Youshuo’s R&D, sales and service. For more questions about the preparation of conductive paste and related applications, please contact youshuo.