Mass soldering technology

Abstract

The first method to be used for mass soldering was a static solder bath operated at around 260 degrees Celsius (Figure 13.1). The circuit board was held in a fixture and fluxed by dipping or brushing, and then it was lowered at an angle of about 20°, held flat on the solder surface for at least two to five seconds then gently lifted from the bath in a swinging or sweeping action, allowing excess solder to drain back into the solder bath. This method was widely used to improve production output — but hand soldering was of course still required for re-work and post-soldering operations. The major breakthrough for mass soldering came with the mechanization of the manual DIL process. Conveyor rails were fitted over the solder bath and carriers were then conveyed at selected speeds through an adjustable entrance and exit angle to allow the solvent gases from the flux to escape and the solder to drain back into the solder bath. The wave soldering machine invented by Fry’s Metals of Mitcham was introduced in 1956. This new soldering process comprised a horizontal conveyor mounted over a foam fluxing unit, a pre-heater and solder bath with a parabolic shape wave; this simple arrangement was the forerunner of today’s modern complex systems some of which are now fully computer controlled (Figure 13.2).