The solder paste process plays a crucial role throughout the entire PCBA manufacturing process, ensuring reliable electrical connections between surface mount components and PCB pads while providing adequate mechanical strength. Let’s explore the solder paste process, technical requirements, and cleaning solutions.
- Process Objectives: Apply appropriate Sn/Pb solder paste uniformly onto PCB pads to ensure excellent electrical connections with surface mount components and sufficient mechanical strength.
- Technical Requirements:
- Uniform and consistent application of solder paste with clear pad patterns, minimizing adhesion between adjacent patterns, and ensuring alignment between solder paste and pad patterns to avoid displacement.
- Under normal circumstances, the solder paste amount per unit area on the pad should be around 0.8mg/㎜². For narrow-pitch components, it should be around 0.5mg/㎜².
- Acceptable deviation in solder paste coverage compared to the desired weight, with coverage on each pad area exceeding 75%. When using no-clean technology, all solder paste must be on the pads.
- After solder paste printing, there should be minimal collapse, neat and orderly edges, displacement not exceeding 0.2mm (0.1mm for narrow-pitch component pads), and no contamination of the substrate surface by solder paste. When using no-clean technology, adjusting the template opening size can ensure all solder paste is on the pads.
- Cleaning Solution: There are two methods for applying solder paste: dispensing and metal stencil (steel mesh) printing. Manual dispensing is rarely used nowadays due to the superior quality and longer lifespan of metal stencil printing. Cleaning of solder paste from steel mesh typically involves specialized equipment such as the Silman Tech Solder Paste Steel Mesh Cleaning Machine, designed for cleaning various types of PCBs used in the electronics industry. This equipment operates entirely on compressed air, eliminating any fire hazards associated with electrical operation. It features user-friendly design, one-button operation, and efficient drying. The high-performance cleaning equipment operates automatically using compressed air, with low consumption and the ability to recycle cleaning fluid, minimizing waste.