Areal Wetting Degree

The wetting angle tells you how well the solder has spread and wetted the surface. If it's too low, the solder beads up and you won't get a durable joint – you'll see gaps and weak spots. If wetting is too high, be careful that the solder doesn't run too thin and cause unnecessary stress in the part. Just make sure the solder flows cleanly and evenly over the area and adheres well, then it's fine.