In the field of electronic product manufacturing, SMT patch processing is a vital process. Welding is an integral part of it, and the choice of solder plays a vital role in product quality and reliability. In this article, we will delve into the selection method of solder for SMT patch processing to help you create high-quality electronic products.
1. Selection of the solder type
In SMT patch processing, common solder types include lead-free solder and leaded solder. Lead-free solder has advantages in environmental protection, but its soldering performance is relatively poor.
In comparison, leaded solder has better soldering performance, but its use is somewhat limited due to the environmental and health concerns of lead. Therefore, when selecting solder type, it is necessary to comprehensively consider product performance requirements and environmental protection requirements to find a balance point.
2. Selection of solder alloy
The composition of solder alloy directly affects the quality and reliability of the welding process. Common solder alloys mainly include Sn63Pb37, Sn60Pb40 and SnAgCu.
Sn63Pb37 is a traditional leaded solder alloy with good soldering performance and reliability.
Sn60Pb40 is a leaded solder alloy with stable soldering performance and suitable for most application scenarios.
SnAgCu is a lead-free solder alloy with excellent mechanical strength and good thermal fatigue properties, and is suitable for soldering high-reliability products.
When selecting a solder alloy, you need to select a suitable solder alloy based on the application scenarios and requirements of the product.
3. Selection of solder viscosity
Solder viscosity refers to the fluidity of solder in the molten state. For SMT patch processing, the choice of solder viscosity directly affects the pad coverage and welding quality.
Under normal circumstances, solder viscosity that is too low will lead to insufficient pad coverage and weak solder joints; while solder viscosity that is too high will lead to over-coverage of the pads, resulting in problems such as short circuits. Therefore, when selecting solder viscosity, it is necessary to find a suitable viscosity range based on the welding process requirements and the design characteristics of the PCB board.
4. Selection of soldering temperature
Solder temperature directly affects the speed and quality of the welding process. If the temperature is too high, it will cause thermal damage to the pads and solder joints, and even damage the assembled components; if the temperature is too low, the soldering will be insufficient and the pads will not be strong. For example, the melting temperature of lead-free solder paste is usually between 217-227℃, while the melting temperature of leaded solder paste is lower, generally between 183-190℃.
Therefore, when selecting the soldering temperature, it is necessary to combine the melting point of the solder alloy and the characteristics of the PCB board to find a suitable temperature range to ensure welding quality and product reliability.
Conclusion
In SMT chip processing, choosing the right solder is the key to ensuring product quality and reliability. By selecting solder type, solder alloy, solder viscosity and solder temperature, welding quality can be effectively improved, the occurrence of welding defects can be reduced, and the performance and reliability of electronic products can be ensured.
