**2. Synthesis of nanocomposites solders**

In olden times, various wires and cables are used to connect the different components into an electric box. With the passage of time, printed circuit boards (PCB), or printed wire boards (PWB) invented near 1950s as a great revolution among electronics industries. Moreover, the invention of transistors and integrated circuits (ICs), analog-to-digital electronics in 1947 made luxurious life style of the common public. This technology of interconnecting various IC's and other electronic component devices like transistors, capacitors, inductors, and resistors within circuits over a PCB substrate to form a compact electronic device is known as microelectronic packaging.[1, 2] The common packages in a personal computer are shown below (Fig. 1).

Since the civilization, the most commonly used solder is lead–tin (Sn–Pb) solder in electronic packaging. However, the toxicity of Pb is a serious concern among the electronic manufactur‐ ers. Pb containing solders are in use so far due to their indispensable properties. The effect of Pb contamination on human beings is a serious threat nowadays. Therefore, Pb and its compounds in electronic devices are now being restricted on account of the bans and regulation imposed by European organizations such as restriction of hazardous substances and waste electrical and electronic equipments.[3–5] It is also to be noted that, though Pb is cost effective, available in abundance, and provides no undesirable reaction with the substrate, yet it shows some technical problems like inferior bonding strength which is important for microjoining.[1– 6] Therefore, composites solders are now being regarded as an alternative to conventional Sn–

Large number of Pb-free solder alloys have been developed and studied where Sn is the major fraction. The most popular Pb-free alloy system candidates are narrated in detail in a review

**Figure 1.** Micropackaging assemblies inside a personal computer.

Pb solders and developed to resolve these concerns.

**1.3. Lead free packaging materials**

**1.2. Microelectronic packaging materials**

254 Electrodeposition of Composite Materials

Although enormous amount of research activities are being done all around the world for a better lead-free solder alloy, no solder alloy is able to completely replace the conventional Sn– Pb solder in terms of performance, economy, availability, solderability, simplicity, mechanical strength, and substrate reaction.[4, 17]

In current research scenario, the development of solder alloys reinforced with nanoceramic particles is being paid more attention toward designing a lead-free solder. Such reinforced solder alloys are generally termed as nanocomposite solders. Nanocomposite solders have shown excellent solderability and reliability. Most of the solder matrix composites are reinforced with ceramic particles like ZrO2, Al2O3, TiO2, SiC, Cu2O, SnO2, La2O3.[7, 18, 19, 21– 25] The reinforcing particles suppress growth of intermetallic compounds (IMC) and provide uniform stress distribution in the matrix.[8, 18, 19] This method of nanotechnology would provide high strength and reliable solders for microelectronic packaging devices.[18, 20]

Various processing routes like melting and casting, powder metallurgy, high-energy ball milling/mechanical alloying, physical vapor deposition, sol–gel, plasma sprayed deposition, chemical methods, and electroplating have been employed to produce solder materials.[9–10, 26–31] Powder metallurgy and mixing methods have been often used to fabricate the lead-free solders reinforced with nanoparticles: Cu, SiC, ZrO2, Al2O3, SnO2, Y2O3, TiB2, carbon nanotube (CNT), rare earth.[9, 21–22, 25, 32–36] There is also a limit on the amount of nanoreinforcement addition in the solder matrix; otherwise, it will deteriorate the solderability and strength. In literature, there is a limited research on solders produced by electrodeposition with a few studies on Sn–CNT and Sn–Bi–SiC solders.[37, 38] Electrodeposition has been already shown to improve reliability of microelectronic devices in 3D Through Silicon Via interconnection packaging.[39, 40] Recently, Sharma *et al*. developed CeO2 nanoparticle reinforced Sn–Ag alloy by pulse co-electrodeposition technique and found a great enhancement in strength, micro‐ structure, and successfully manipulated the residual stress to mitigate of dangerous tin whiskers.[41]
