What problems should be paid attention to when choosing lead-free components for lead-free process?
1. The heat resistance of the components must be considered
Due to the high melting point of lead-free solder, one of the characteristics of the smt lead-free soldering process is the high soldering temperature, which brings about the problem of heat resistance of components. Therefore, when evaluating component suppliers in the PCBA lead-free process, it is not only necessary to evaluate whether they use toxic and harmful substances, but also to evaluate the heat resistance of the components.
Different components have different heat resistance modes. Some are impact-resistant but not high-temperature resistant, and some are high-temperature resistant and not shock-resistant; the temperature resistance curve of components is not equal to the soldering temperature curve. damage a component.
2. The compatibility of solder and component surface coating materials must be considered
In lead-free soldering, the types of component soldering end coating materials are the most and the most complex. The types of lead-free components soldering surface coating are pure Sn, Ni-Au, Ni-Pd-Au, Sn-Ag-Cu, Sn-cu, Sn-Bi and other alloy layers of different solder alloys; their interface reaction speed Different, the resulting brazing seam structure is different, and the reliability is also different.
Due to the variety of electronic components and the complex plating of the component soldering ends, there may be a mismatch between the soldering ends of some components and the solder, causing reliability problems.