Typically, we configure the reflow profile to work with the available solder and components, to give the highest tensile strength possible. So, we know what the end goal is, and we adjust what we have to achieve that goal. Besides tensile strength, some secondary goals are good wetting, solid intermetallic formation, homogeneous solder joint and a small, tight crystal structure. All of these are achieved through process management of the reflow process.
There are four parts of the reflow process that are adjusted to achieve the goals we have in mind, namely highest possible tensile strength. They are ramp rate, time above liquidus (TAL) peak temperature and cool down rate. Each one of these has its own effect on the final solder joint, and each one is important.