I solder very rarely and quite badly, but switching to non-lead solder just made it impossible to get good joints. I had to get a better iron, nothing fancy but with higher effect, meaning I can get to a higher temperature faster without turning the whole PCB into mush.
I felt a little puzzled about this but then it hit me that you probably meant Fahrenheit.
To spare others the conversion: 675 °F is roughly equal to 350 °C.