Surface Mount Technology ran a piece titled Parallel Processes: Simultaneous Lead and Lead-free Soldering with a Single Reflow System written by Hans Bell of Rehm Thermal Systems GmbH. Hans details a study where by controlling conveyor speed of each lane of a dual-lane system, it is possible to run both a lead and lead free product simultaneously.
The devil of course is always in the details:
Definition of the process window must always be based on the “weakest link,” namely the component with least amount of thermal stability during the soldering process. If two different processes are to be set up next to each other in the same reflow system, and if thermally sensitive components are included on the PCB, great flexibility is required for parameters configuration.
The ability to develop process windows for each product leaving enough room for each to call upon the same oven zone set points is key and of course taking into account special temperature tolerant components on each board. Hans’ idea is intriguing. Based on my experience in a world were many PCBs manufacturers struggle to profile or perhaps do not profile at all, this is certainly a tall order. Nevertheless his idea is do’able for perhaps many processes, since changing just the conveyor speed to reduce product changeover on a single lane oven is being done today (click here for an excellent application note using KIC product’s to achieve this end). Why this couldn’t be adopted to a dual lane system running both lead and lead free simultaneously has its merits.
