dmh wrote:The tip I am using now turn almost black after on a couple of solders on microSD board. That just seemed kinda strange to me.
Sounds like you are not cleaning it and keeping it tinned. If you don't do this the tip will keep oxidizing and eventually become useless as you will wreck the plating.
To clean off the old solder and flux, wipe it against a damp (not soaking wet) sponge or one of those curly brass tip cleaners.
Tinning just means adding some fresh solder to the tip!
You can see all this and more here: https://www.youtube.com/watch?v=I_NU2ruzyc4
Lastly, don't file a tip to clean it, as you will file the plating off and the tip will deteriorate MUCH faster. If your tip is in such bad shape that you'd need to file it, it's stuffed anyway and you'll need a new one.