How to choose the right electroplating silver powder for silk screen printing?
Matching Particle Size and Mesh Size to the Silk Screen
The mesh size of the silk screen (e.g., 80-300 mesh) must be compatible with the silver powder particle size. The finer the mesh size (e.g., 200-300 mesh), the finer the silver powder (typically 1-10μm) should be used to prevent silver powder particles from clogging the mesh and causing "ink breakage." Coarser mesh sizes (e.g., 80-120 mesh) can be used with slightly coarser silver powder (10-20μm), but be careful to avoid excessively large particles, which can cause rough edges on the printed pattern.
If you're looking for a high-mirror finish, it's recommended to choose spherical or quasi-spherical electroplating silver powder (rather than flakes) for enhanced light reflectivity. If you're looking for a matte metallic finish, you can opt for silver powder with an irregular morphology.
Preferably, choose silver powder with a "silicone-specific" surface treatment. Ordinary electroplating silver powder may contain oil or an oxide layer on its surface, and adding it directly to silicone can easily cause "agglomeration" (silver powder clumps and becomes difficult to disperse). It's recommended to choose silver powder treated with a silane coupling agent (such as KH-550 or KH-560) or fatty acid. The surface of this type of silver powder can form chemical bonds with the silicone molecules, improving dispersion and strengthening the bond between the silver powder and the silicone, reducing subsequent shedding.
Pretreatment before use: Impurity removal and activation
If silver powder has been stored for an extended period, it should be dried at 80-100°C for 1-2 hours to remove any surface moisture. This prevents moisture from causing bubbles during silicone vulcanization.
If the silver powder is slightly agglomerated, pre-disperse it in a high-speed disperser (1000-2000 rpm) for 5-10 minutes before adding it to the silicone system.