The printer is the front-end process equipment of the SMT production line, mainly used to print solder paste onto PCB pads. An important component required for printing onto the pads is the stencil. The stencil, essentially a template matching the PCB pads, contains holes corresponding to the PCB pads and is primarily used by the printer’s squeegee for solder paste application. Below is a brief introduction to common types of stencils and their cleaning methods:
- Fine-Pitch Stencil:This stencil is suitable for resistive screens, mobile phone protective films, and UV oil printing for isolating points in mobile phone protective covers.
- Dual-Process Dual-Circuit Stencil:This stencil combines solder paste and red glue on a single screen, making the process somewhat complex, and it is challenging for factories to implement.
- Red Glue Stencil:Also known as SMT adhesive or SMT red glue, this is a red paste evenly distributed with adhesives, hardeners, pigments, solvents, etc. It is mainly used to fix components on printed boards, usually applied by dispensing or stencil printing. After component placement, it is heated and cured in an oven or reflow soldering machine. Unlike solder paste, once heated and cured, the hardening process of SMT adhesive is irreversible. The performance of SMT adhesive varies depending on curing conditions, bonded materials, equipment used, and operating environment. Selection of SMT adhesive should be based on production processes.
- Solder Paste Stencil:Similar to the process for solder mask printing on rigid boards, this involves applying a layer of solder paste to be used for subsequent component soldering.
- Silver Paste Stencil:Silver paste finds various applications in the electronics industry, such as manufacturing PTCs, NTCs, varistors, disk resistors, buzzers, solar cells, and other component external electrodes.
In the electronic manufacturing process, the conventional cleaning method for SMT stencils typically involves using Silman Tech pneumatic spray stencil cleaning machines. This method ensures safe equipment operation and achieves a perfect SMT water-based cleaning process with one-touch operation.
