TABLE OF CONTENTS Although soldering is such a well known joining method and has been in general use for so many years, the average engineer and user of this process finds difficulty in defining it properly. However, on the basis of the information presented in this book, it is possible to define soldering as follows:
Soldering. A metallurgical joining method using a filler metal (the solder) with a melting point below 600 F (315 C), [a] soldering relies on wetting for the bond formation and requires neither diffusion nor intermetallic compound growth with the base metal to achieve bonding.
Let us analyze this definition a bit further. Metallurgical bonds are connections between metals only. In general, they are those bonds in which metallic continuity from one metal to the other is established. The other bonafide metallurgical joining methods are brazing, welding, and some of the more recent developments that are a combination of these, e.g., diffusion bonding and thermal-compression bonding. The limit of 600 F was set arbitrarily, and many people consider 800 F (425 C) the cutoff point for soldering. The author, however, prefers to place solder alloys in the 600 800 F in a subgroup of "hard solders," while the lower-temperature alloys would be "soft solders." In comparison with soldering, brazing is defined as follows:
Brazing. A metallurgical joining method using a filler metal that melts over 800 F (425 C) and that relies on wetting as well as diffusion for the bond strength.
Under the same conditions, welding could be defined as follows:
