FIREBAR Heaters Make New Wave Soldering Possible
The printed circuit board industry has many uses for electric heat including coating the boards with solder. A manufacturer of wave soldering equipment had circuit boards travel along a conveyor system that passed over a solder pot. As the boards pass over, they're coated with a silver solder #6637, commonly used on PC boards. The solder is heated to approximately 500°F (260°C).
Watlow approached this application from two angles. First, six FIREBAR® elements were spaced across the bottom of the solder pot. This turned out to be a very effective way to get an even heat pattern across the entire pot. This solved the application for the most part, but more heat was needed along the pot's sides. The element was formed around protrusions on the pot's sides, with a WATROD tubular element used to provide the extra heat. A FIREBAR could not be used in this instance because the required bend radius was too small.
The FIREBAR was made with an Incoloy® sheath and formed in a basic "L" shape. It was single-ended termination with lead wires and bracket attached to one end only. This application allowed 28 W/in2 (4.3 W/cm2) with a total of 1750 watts. The WATROD heater was dual ended with an Incoloy sheath. The formation was a rectangle that fit the pot's outer dimensions. Though it sounds simple, this formation was very difficult with side heater application requiring 24 W/in2 (3.7 W/cm2) with a total of 4300 watts.
Watlow was able to keep the total price down because fewer FIREBAR heaters replaced an even greater number of round tubulars. This fact, plus the ability to make difficult formations, convinced the customer to buy from Watlow.