Instead of using adhesives to glue the back side SMD components and wave soldering them together with the through hole components, our manufacturing engineers choose to process the back side components through reflow oven without adhesives and process the topside components through reflow oven. After through hole components are inserted into the panels, the panel utilizes a wave solder pallet to protect the SMD components that are located at the back side of the panels when going through the wave soldering bath. I thought that the process is very efficient. However, the no clean flux started to build up at the opening of the wave pallets. One of the production runs had some leads not being soldered. Some people started to question the process. Can some one help me to do a comparison of this method vs using adhesive to clue the back side components? Are both processes widely utilized in the industry? What are known issues to either of the processes?