Here is a link to a thread I just posted about itchy skin.
http://www.yorkietalk.com/forums/showthread.php?t=25127
As for the micro chip I doubt that is what is making him itch. The micro chip is cased in hyper allergetic materials.
MOST dogs don't get dry skin/coat til they are between 9 and 18 months. Reason being that is about the time they a most or all of their adult coat. That is also the time frame for allergies to develope. (not saying they can't get this before or after that time frame that is just the norm)