Frequently Asked Questions

A: Solder wave variation happens. It is by nature a dynamic process caused by the pumping of a liquid. Through various channels, weirs, rudders, and nozzles, all designed to balance flow across the surface of the wave, liquid solder makes its way to the surface and finally breaks one way or the other depending on the wave shape. Lacking the presence of a printed circuit board, this wave looks even and more or less smooth on typical wave solder machines. However, some ripples and eddies are visible as the flow of solder moves toward the spill point. These ripples are everywhere and only some of the bigger ones are pointed out in the picture below.

Typical Ripples and Currents on smooth looking solder waves. Copyright © 1999 ECD

Currents running throughout the wave take on a whole new manifestation when they run into the underside of a printed circuit board. They will cause the crest of the wave to very, much like ocean waves as run up a sandy beach. An ocean wave will never rush up the sand and stop in a perfectly straight line even though the beach may be very flat. Thus the crest of the solder wave as it flows against the underside of a printed circuit board will be very dynamic. You can view this using a tempered glass plate, such as the one called "Lev Chek" by Hexacon Electric, as it runs slowly across the solder wave just like you would solder a printed circuit board. A typical solder wave using this glass plate is pictured below.

Typical wave crest pattern as viewed through tempered glass plate. Copyright © 1999 ECD

The crest of the wave is highlighted to make is more visible. As you can see, the edge is very rough and is constantly changing shape as it progress across the board. It is also noticed that the sides of the wave tend to be narrower than the middle. Based on this snap-shot, one would expect this wave two read parallel with sensors "A" and "C" reading lower contact times than "B." This high in the middle observation is typical in many waves and is not because the glass bent down in the middle. It is most likely due to increased pumping action near the center of the wave, which may also be causing the increased ripple action near the center as seen in the first wave illustration. Also, with this typical wave dynamics one should expect successive measurements to have some variation. In the above illustration, at 4 ft/min conveyor speed, one can expect up to 0.8 seconds variation from sensor to sensor.

The real issue in making exact measurements from your solder wave is to determine what your solder process can tolerate, and not necessarily to make the solder processes perfect. Clearly some parameters are more important, such as conveyor speed, solder temperature, and preheat slopes. But, to expect a pumped liquid as dense as solder to behave with perfect geometry is asking a bit much from the machine manufacture. Also, your solder process is most likely producing good results. If not, a measurement tool will quickly point out the problem. But the goal of measuring a good process is to obtain data which can be used to determine how much variation is acceptable and help predict when a good process is going bad.

Q5.8: How does the WaveRIDER detect a chip wave?