*Active Solders and Active Soldering DOI: http://dx.doi.org/10.5772/intechopen.82382*

*Fillers - Synthesis, Characterization and Industrial Application*

melting point of about 750–850°C. Brazing is conducted at temperatures generally higher than 800°C. For some applications, the brazing temperature is so high that it causes hot cracking or functional degradation of the ceramics. Moreover, due to the difference in the thermal expansion coefficients of the metal and ceramic materials, high residual stress will develop upon cooling from the elevated temperature. Hence, the bonding temperature should be as low as possible to minimize the residual stresses. To solve this problem, low melting point filler metals containing titanium, such as Sn10Ag4Ti and Pb4In4Ti, have been developed, and they exhibit excellent wettability on ceramic substrates at 850°C. Unlike the widely used Ag–Cu-based active filler metals, the low melting point filler metals possess a melting range below 300°C. However, brazing ceramics with low melting point active filler metals is always conducted above 850°C, such as the Ag–Cu–Ti brazing temperature, owing to the decent thermodynamic activation [21–23]. Although the act of brazing with low melting point filler metals must be conducted at elevated temperatures far above

*Schematic of the spreading process of solder with the formation of reaction layer [9].*

*Contact angle of sessile drop configurations (a) wetting and (b) nonwetting [2], where θ is the contact angle, γSV is the solid-vapor interfacial energy, γLV is the liquid-vapor interfacial energy, and γSL is the solid-liquid* 

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**Figure 3.**

**Figure 2.**

*interfacial energy.*

