Most welding cases use a square welding pulse as shown below. However there are a few applications where the use of pulse shaping can enhance welding. There are numerous pulse shapes, however, two basic pulse shapes are most commonly used. The first is for overcoming highly reflective material such as copper and aluminum, and the other is to minimize the thermal cycling experienced by the part during welding for materials susceptible to cracking.
Some common pulse shaping options for welding.