The First 7,000 Years of Soldering, Part I

early a million years ago, mankind’s technological march through time beN gan after fire was mastered. Metalworking, which evolved into metallurgy, is the oldest and most successful technology. It spans at least 12,000 years (Figure 1). Soldering, a key metal joining technology, was probably developed about 7,000 years ago when lower melting, naturally occurring metal alloys were placed in the blowpipe-fanned fires of that day.* Early man used these precious metal alloys to join castings made of gold or silver. The earliest solders were based on gold and included gold alloys of silver or tin. All early metallurgy was developed in the name of art. The earliest solders, of course, were leadfree and environmentally friendly. The Romans developed soft solders for utilitarian purposes, such as plumbing, and these joining materials also found use in the artwork of the bronze age. They gave us eutectic tin-lead solder, which is now the workhorse alloy of modern electronic assembly (Figures 2, 3).