- SAC alloys offer solder joints which are less reflective than 63/37; the contact angles tend to also be higher and spread is less. These are not considered defects but only cosmetic. If air reflow is used, SAC joints will be less bright and show surface effects such as crazing which are due to the intermetallics within the solder and oxidation effects. If nitrogen reflow is used the joints will be more reflective and spread will be enhanced.

- Below are two photos. The one on the left is 63/37, while the other shows joints done with SAC305 alloy.

- Lower peak temperatures and lower times above liquidus will reduce both intermetallic growth but also increase the overall brightness of the solder joints

- Proper training will be required when transitioning to lead-free assembly. Operators will need to be given quality acceptance criteria for solder joints that will look quite different from traditional leaded systems.

SAC Solder
in air