Growth of electrical vehicles and 5G technologies may impact the landscape of soldering equipment used for printed circuit board (PCB) assemblies. These applications require large multi-layer PCBs that contain small surface mounted devices (SMD) together with heavy transformers and capacitors. This mismatch of thermal mass creates challenges for reflow process and specifically for convection ovens. Large or heavy components usually require long total heating time which may cause small  components to overheat. The paper includes comprehensive research to identify alternative technologies or viable modifications/additions to existing convection reflow process that can provide more uniform heating and meet high throughput requirements. 

The study identifies the limits of traditional convection ovens. What mass components can’t be soldered together with small packages like 01005 within the required process window using lead-free alloys. All considering solder pastes properties and limitations, maximum peak temperature and Time Above Liquidus (TAL) requirements as well as fan speed limitations (no component movement). 

Statistical techniques such as “Box Behnken” have been performed to determine the limits of this soldering process. An investigation of available commercial solutions and emerging technologies that may help mitigate above technical challenge and enable future opportunities in convection reflow was part of the research. Experiments to improve the heat transfer in convection reflow included combination of reflow and conduction heating. The results of these process optimizations are presented.