According to Dimock, “When I first considered writing a paper about the effects of belt speed, zone set points and static pressure on a reflow profile, I was hesitant because the concepts are relatively simple and well known by most experienced surface mount engineers.” But the time-proven recipe of providing a clear, crisp easy-to-understand review of the basics proved to be just what the readers wanted.
“After mentioning the data that I had gathered for the paper during a Profiling Techniques Panel discussion hosted by Circuits Assembly Editor Mike Buetow at APEX in 2010, I was convinced to complete the paper. Many industry experts said that surface mount engineers need practical information that can be applied to their current situation. I knew it would also benefit experienced people by reminding them about the basic principles of profile development and help new people understand the adjustments that can be made to a reflow oven to obtain a good profile,” added Dimock. “The response has been great. I am honored and pleased that the paper is helping engineers and technicians.”
The change from eutectic to lead-free solder has required new recipes for the reflow process. Although solder paste manufacturers have developed profile parameters, it remains the responsibility of the assembly engineer to find the correct control settings with a limited number of reflow oven adjustments.
Conventional reflow ovens have two adjustments for profile development. One is the zone set points and the other is belt speed. Some oven manufacturers have added high, medium and low fan speeds as an additional adjustment, and one manufacturer has a closed-loop pressure control.
The paper discusses the findings of a study that was undertaken to determine the effects varied belt speeds, static pressures and zone temperatures have on the peak temperature, time above liquidus (TAL) and temperature uniformity of a 100 and 230 g populated surface mount board.