*5.2.2 EDAX analysis*

EDAX analysis for both the alloys is presented in **Figures 13–16**. In both cases, the leaf-shaped morphology showed no intermetallics, whereas the needle-shaped morphology showed intermetallics.

Rod-like zinc-rich phases have been observed when cerium and lanthanum of the order of 0.1 wt.% are added [18]. In the current work, since the weight % of rare earth element indium added is relatively high, in all probability, the needle-like phase is rich in indium (72 and 66.36%, respectively) and zinc percentage is lesser,

**Figure 13.** *Chemical composition of the leaf-shaped specimen-alloy 1.*

#### **Figure 14.**

*Chemical composition of the needle-shaped specimen-alloy 1.*

#### **Figure 15.**

*Chemical composition of the leaf-shaped specimen-alloy 2.*

#### **Figure 16.**

*Chemical composition of the needle-shaped specimen-alloy 2.*

agreeing with published literature on cerium and lanthanum addition. Gadolinium addition has been found to refine grains of Mg**▬**5Sn**▬**Zn**▬**Al [19].

In some cases, there have been reports of intermetallic formation suppression as a result of the addition of rare earth metals. A study by Huan Lee et al. showed that addition of praseodymium reduced the formation of intermetallics at the junctions of a Sn**▬**Zn**▬**Ga solder [20].

## **5.3 Microstructural analysis of Sn▬Cu lead-free solders**

**Figure 17(a, b)** shows the dendritic structure of 87Sn**▬**7Cu**▬**3.0Mn**▬**3Ag. The dendrite structure is not seen in the second sample. We can infer that the dendrites are broken down in the second sample. Han et al. [10] and Yang et al. [21] also have reported the influence of Ni-coated carbon addition on the microstructure of Sn3.5Ag0.7Cu nanocomposite solder. It is found that the morphology of Ag3Sn and Cu6Sn5 was

**19**

**Figure 18.** *Sample 1.*

*Role of Intermetallics in Lead-Free Alloys DOI: http://dx.doi.org/10.5772/intechopen.85515*

phase and melting of primary β-Sn.

**6. SEM fractography**

**Figure 17.**

graphs of SnCu alloys.

uniformly distributed in the solder matrix. But the addition of another fourth element to form a quaternary changes the microstructure. Some researchers produced intermetallics, which react with Sn, thus refining the microstructure of Sn, Ag and Cu solder. Other researchers chose to add some low solubility and diffusivity in Sn, such as Al2O3, TiO2, SiC and POSS. In general, it was found that until a critical value of alloying element content, properties are enhanced, and above this % age, it becomes detrimental to the alloy. So, addition of Manganese seems to have increased the melting point. The slight difference in melting temperatures could be due to the difference in alloying elements in each sample. Addition of 0.2% iron to SnAg Cu alloys results in two exothermic peaks at 220 and 235°C. When adding 0.6 wt.% Fe, only a single endothermic peak at 221.35°C was found, showing that it has a eutectic composition [22]. Based on the ternary SnAgCu phase diagram [23], there are two steps in the DSC. This could be because of melting of ternary eutectic β-Sn + Ag3Sn + ηCu6Sn5

*Microstructures of (a) 87Sn▬7Cu▬3.0 Mn ig. 5. Microstructures of (b) 87.5Sn▬7.5Cu▬2.5Mn▬2.5Ag.*

SEM micrographs are generally used to give information about the type of fracture. Here, since tensile tests have not been done, SEM has been used to identify Sn whiskers. There have been some studies showing Sn whiskers in the SEM micro-

The abovementioned SEM micrographs are of two samples of slightly varying chemical composition. **Figures 18** and **19** show the absence of tin whiskers in both *Lead Free Solders*

**Figure 14.**

**Figure 15.**

**Figure 16.**

*Chemical composition of the needle-shaped specimen-alloy 1.*

*Chemical composition of the leaf-shaped specimen-alloy 2.*

*Chemical composition of the needle-shaped specimen-alloy 2.*

**18**

of a Sn**▬**Zn**▬**Ga solder [20].

agreeing with published literature on cerium and lanthanum addition. Gadolinium

**Figure 17(a, b)** shows the dendritic structure of 87Sn**▬**7Cu**▬**3.0Mn**▬**3Ag. The dendrite structure is not seen in the second sample. We can infer that the dendrites are broken down in the second sample. Han et al. [10] and Yang et al. [21] also have reported the influence of Ni-coated carbon addition on the microstructure of Sn3.5Ag0.7Cu nanocomposite solder. It is found that the morphology of Ag3Sn and Cu6Sn5 was

In some cases, there have been reports of intermetallic formation suppression as a result of the addition of rare earth metals. A study by Huan Lee et al. showed that addition of praseodymium reduced the formation of intermetallics at the junctions

addition has been found to refine grains of Mg**▬**5Sn**▬**Zn**▬**Al [19].

**5.3 Microstructural analysis of Sn▬Cu lead-free solders**

**Figure 17.** *Microstructures of (a) 87Sn▬7Cu▬3.0 Mn ig. 5. Microstructures of (b) 87.5Sn▬7.5Cu▬2.5Mn▬2.5Ag.*

uniformly distributed in the solder matrix. But the addition of another fourth element to form a quaternary changes the microstructure. Some researchers produced intermetallics, which react with Sn, thus refining the microstructure of Sn, Ag and Cu solder. Other researchers chose to add some low solubility and diffusivity in Sn, such as Al2O3, TiO2, SiC and POSS. In general, it was found that until a critical value of alloying element content, properties are enhanced, and above this % age, it becomes detrimental to the alloy.

So, addition of Manganese seems to have increased the melting point. The slight difference in melting temperatures could be due to the difference in alloying elements in each sample. Addition of 0.2% iron to SnAg Cu alloys results in two exothermic peaks at 220 and 235°C. When adding 0.6 wt.% Fe, only a single endothermic peak at 221.35°C was found, showing that it has a eutectic composition [22]. Based on the ternary SnAgCu phase diagram [23], there are two steps in the DSC. This could be because of melting of ternary eutectic β-Sn + Ag3Sn + ηCu6Sn5 phase and melting of primary β-Sn.
