Not quite, the leads are (usually) coated with something. If it's pure tin it can grow whiskers from the top or even from under the solder connection, even if y

Not quite, the leads are (usually) coated with something. If it's pure tin it can grow whiskers from the top or even from under the solder connection, even if you use a leaded solder to attach it to the board. That's why even DIP parts come in leaded or lead-free versions. There are packages which come with the solder, like BGA, which can (usually?) safely be reballed to use leaded.