In the field of electronic manufacturing, lead-free solder balls are widely used due to their environmentally friendly characteristics. However, a humid environment is a common condition in the electronic production process. So does the lead-free solder ball have any effect on the welding quality in a humid environment?
A humid environment will cause moisture to be absorbed on the surface of the lead-free solder ball. When the lead-free solder ball is exposed to humid air, a thin layer of water film will gradually form on its surface. This is like a dry sponge that will slowly absorb water when placed in a humid environment. This layer of water film will cause many problems during the welding process. During welding, high temperature will cause the moisture absorbed on the surface of the lead-free solder ball to vaporize rapidly. Imagine that when water changes from liquid to gas, its volume will expand rapidly. In the narrow space of welding, this rapidly expanding water vapor will generate a large pressure, which may break through the solder joint being formed, resulting in a void in the solder joint. The presence of voids will seriously affect the mechanical strength and electrical performance of the solder joint, just like a bridge with a void in the middle, its load-bearing capacity will be greatly reduced, and the connection between electronic components will become unstable.
A humid environment can also affect the wettability between the lead-free solder ball and the pad. Wettability refers to the ability of a liquid to spread on a solid surface. In welding, good wettability is the key to forming a high-quality solder joint. In a humid environment, the oxide layer on the surface of the lead-free solder ball may be accelerated by the presence of moisture. The oxide layer is like a diaphragm that prevents the lead-free solder ball from making good contact with the pad. Originally, the lead-free solder ball should spread evenly on the surface of the pad like water drops on a lotus leaf to form a tight bond. However, due to the presence of the oxide layer, the lead-free solder ball may not be able to fully wet the pad, resulting in irregular solder joints and even cold solder joints. Cold solder joints are like "time bombs" in the circuit. Although the connection seems normal on the surface, it is easy to disconnect due to vibration, temperature changes and other factors during actual use, affecting the normal operation of electronic equipment.
Moisture may also trigger a chemical reaction between the lead-free solder ball and the pad. Under the high temperature conditions of welding, active substances such as hydrogen ions in the moisture may react chemically with the lead-free solder ball and the pad material. These chemical reactions may change the composition and structure of the solder joint, resulting in a decrease in the performance of the solder joint. For example, some brittle compounds may be generated, making the solder joint brittle and easy to break. This is like an originally strong alloy material that becomes brittle and cannot withstand normal stress due to the mixing of other impurities.
A humid environment will also have an indirect impact on the stability of the welding equipment, which in turn affects the welding quality of the lead-free solder ball. When the welding equipment is in a humid environment, the electronic components inside it may be damp, resulting in unstable equipment performance. For example, inaccurate temperature control, deviation in welding time, etc. These changes in equipment parameters will prevent the lead-free solder ball welding process from being carried out according to the predetermined process, thereby affecting the quality of the solder joint. Just like when a chef cooks, if the heat and time are not well controlled, the taste of the dish will be greatly reduced.
In order to reduce the impact of a humid environment on the welding quality of lead-free solder balls, a series of measures need to be taken during the electronic production process. First, the humidity of the production environment should be strictly controlled, and dehumidification equipment can be used to control the humidity within a suitable range. Secondly, when storing lead-free solder balls, they should be placed in dry, sealed containers to avoid contact with humid air. Before soldering, the lead-free solder ball can also be preheated to remove the moisture adsorbed on its surface.
The lead-free solder ball does have many adverse effects on the soldering quality in a humid environment. From solder joint voids, poor wettability to chemical reactions and equipment stability issues, the mechanical strength and electrical properties of the solder joints will be affected. Therefore, in the electronic manufacturing process, it is necessary to pay attention to the impact of the humid environment and take effective measures to ensure the soldering quality of the lead-free solder ball and ensure the reliability and stability of electronic equipment.
