Although reflow ovens may not have been dramatically changed during the last decade the reflow process changes step by step. With the introduction of lead-free soldering not only operation temperatures increased, but also the chemistry of the solder paste was modified to meet the higher thermal requirements. Miniaturization is a second factor that impacts the reflow process. The density on the assembly is increasing where solder paste deposit volumes decreases due to smaller pad and component dimensions. Pick and place machines can handle more components and to meet this high through put some SMD lines are equipped with dual lane conveyors, doubling solder paste consumption. With the introduction of pin in paste to solder through hole components contamination of the oven increased due to dripping of the paste.
The iNemi Roadmap identified seven key metrics for the reflow process:
- Temperature delta performance
- Inerting capability
- Cooling rates
- Flux management
- Cost of operation
- Changeover time
The current flux collection systems need to focus on improvements to minimize maintenance downtimes. Flux management and cost of operation will benefit from an efficient oven cleaning method. The filter and condensation systems that were successful running in SnPb processes have to be reviewed and new technology is introduced to have a more efficient removal of solder paste, board and component gasses.