If any one wants to create a mechanical keyboard and use the controller board of the logitech k120 , there are some extra keys on the keymap that are not present on the actual keyboard but was present in the matrix , like the shortcut keys and the volume up and down keys , as well as the power and sleep keys.
Yea the black thing is just graphite on top of copper pad , on the first pin i have scraped it off and the copper is visible so just need to scrape the graphite off and good to solder :)