Effect Analysis of High Temperature of Lead-free Welding on Reliability of Components
Lead and its alloy coating has been basic materials of interconnection of electronic products for a long time, which has advantages of good quality and low price, and has been widely applied. In recent years, people have gradually realizes toxicity of lead and its alloy can threat human’s health to some certain degree. Based on this, lead-free welding technology has been promoted, which is main trend of welding technology development. Effect of lead-free welding high tempreture on components’ reliability is analyzed as follows, hoping to help related working staffs.
Current situation of lead-free welding technology:
From the current actual situation, there is no unified standard for lead-free solder. Generally, tin is the main content of welding materials, and then other metals are added to it. In recent years, with the deepening of people's research on lead-free welding technology, the research on lead-free solder has developed rapidly. At present, the common lead-free solder takes Sn AG, Sn Zn and Sn Bi as the matrix, and appropriately adds an appropriate amount of other metal elements to it to form ternary alloy and multicomponent alloy.
Failure of components caused by high temperature of lead-free welding:
For some moisture sensitive devices (MSD), with the continuous rise of process temperature, the components will absorb a large amount of moisture. These moisture will be gasified under the action of high temperature. At this time, the gasification will expand rapidly and eventually form a large pressure. It may cause various adverse phenomena such as cracks and delamination, which will reduce the quality of MSD, and affect its performance.
Another impact of lead-free process on the reliability of components is the impact of weldability and high temperature on the internal links of components.. During the welding process, the internal solder joint will melt and solidify again at the same time as the surface assembly solder joint, which will have a great adverse impact on the reliability of the device. Therefore, the materials used for connection in lead-free components must meet the requirements of the welding process for high temperature. The welding material with higher melting point than that required for secondary assembly welding shall be used to avoid remelting of internal connection points during welding.
3. Using thermal management technology to solve the high temperature thermal failure of lead-free process:
it is important to understand the maximum temperature limit of each element, which is of great significance for welding quality. Some components can meet the specific requirements of RoHS in the welding process. However, from the actual situation, it is difficult to meet the maximum temperature requirements for lead-free welding. For example, if the maximum temperature specified by the component manufacturer is exceeded, it may adversely affect the reliability of the product during application. Element thermal management is a feasible method for welding thermal sensitive elements. Through the application of this method, it can replace manual welding and selective welding.
Thermal management is to reasonably control the temperature curve of each element during reflow soldering. Through the reasonable application of software thermal management, the welding of thermal sensors can be realized by using the standard reflow welding temperature. The reflow soldering curve is determined according to the specific situation of solder joint quality. The thermal failure and damage of lead-free soldering at high temperature are solved through component thermal management.
Lead will cause great harm to human body. Now many electronic products have begun to apply lead-free process. In the process of applying lead-free process, people focus on the reliability of high lead-free solder in the specific welding process.
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