# Reliable Method to Detect Alloy Soldering Fractures under Accelerated Life Test  
[PERSON]. [PERSON]  
1 Engineering Department, Universidad del Valle de Mexico, 76230 Queretaro, Mexico  
A soldering alloy is one of the most important elements of an electronic assembly as it carries the electric current that makes the assembly work, because the components, as part of the assembly, are joined to the motherboard, allowing the conduction of electrons. A failure in the soldering joint is a critical problem, because it will not allow current flow and the operation of the system will not work properly [2; 3; 4; 5]. Some of the most common failures are open circuit, short circuit, cold weld, splash, weld bridges, porosity, and refluxes. All these problems can be caused by human error, random systems, or wasted material. [PERSON] [4] indicated that an electronic assembly would fail if the soldering joints deteriorated to a critical level and decreased the reliability of the system. An open circuit could be caused by both thermal and mechanical stress, causing a ductile fracture in the soldering alloy. [PERSON] [3] indicated that a fracture appears due to impurities or phenomena originating during the welding process, e.g., the nucleation of micro-hollows or fractures for intergranularity. These impurities, scratches, or the remaining stress located on the surface of the weld cause the appearance of fractures. Therefore, it is important that the cleaning and finishing of the welding surface should be prepared in accordance with norms and codes. A ductile fracture occurs when the soldering alloy is exposed to plastic deformation due to stress caused by damage including excessive tensions such as thermal variation or mechanical effort. In some research [6; 7; 8; 9; 10; 11; 12; 13], it is mentioned that mechanical effort causes parallel cracks, and thermal variation generates a network of multiple fissures. Furthermore, there have been fracture analyses using measures of resistance and visual inspection. [PERSON] et al. [5] carried out a microstructural analysis of an electronic circuit that allowed visual identification of the propagation route of the fractures. In addition, they obtained micrographics using a high-resolution microscope. Certain authors have analyzed the different failures originating in soldering alloy. [PERSON] et al. [6] observed that fluctuation in temperature caused expansions in the soldering alloy, generating additional stress and degradation. Due to this, there have been development tests that determine the capacity of a soldering alloy to resist thermal fatigue. [PERSON] et al. [7], [PERSON] et al. [8], and [PERSON] [14] mentioned that electronic systems are a dynamic object susceptible to vibration. Their investigations demonstrated that a soldering alloy is a place of failure caused by vibrations. These authors used a criterion of failure as the identification of fracture propagation, which had a progressive increase of 20% of the initial resistance. The literature does not report many cases of tests with different combinations of tin that have been used in the development of this research: SnPb and SnAg are the most commonly used alloys in the market for the type of components presented in the present work. In the development of this research, 17 electronic assemblies with dimensions of 2 cm \(\times\) 2 cm were fabricated, where components such as leads and electric resistors were used. This had the objective of analyzing the characteristics of the soldering alloy; see Figure 1. These types of electronic components are the most used worldwide in all types of electronics components, including TVs, cell phones, tablets, computers, resistors, diodes, LEDs, and capacitors.  
Figure 1: Electronic component assembly. Type Diode-LED. (**a**) shows SnPb Alloy. (**b**) shows SnAg Alloy.