Hello Bachman. SAC305 is the most common lead-free solder alloy, not only for wave soldering but also selective. Most of our selective customers (especially automotive) are using SAC305.
What is more important than the alloy to consider is the flux. Your flux supplier should be able to give you a sample of a flux suitable for selective.
On most selective machines today, flux is applied via microdrop fluxer because it is more precise and provides excellent coverage.
At EBSO, we recommend a halogen free, low solid, alcohol base flux because it has great hole filling and little flux residue left behind. Interflux and Alpha Metals provide good flux products.
Flux is a key parameter for 100% good through hole filling. With selective, the flux must cope with moderate pre-heat.
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