For clarification. What do you mean by colonization? i know, it's semantics, and the question is perfectly valid, but the assertion that colonizing africa became a big thing in the 1400's seems out of place considering the brunt of the colonization happened in the latter half of the 19th century.

Do you mean why they didn't establish settlements like later in America, or why they didn't establish trading posts before the fifteenth century, or why they didn't just go in and conquer the region , like they did later in the 19th century? all of these are examples of "colonization" with different reasons and capabilities.

Hope this gets an answer!

Generally speaking no, the Europeans generally stayed around the Mediterranean, as the Sahara was not worth crossing for them. Early exploration was more about finding trade than simply exploring for exploring sake, which is incredibly expensive, ,however the general geography of Northern Africa was known to the Romans, but they did not venture further South, as the Empire faced inward rather than outward. The Romans had no reason to look outside themselves as all the trade they could want was already within their empire, and the Mare Nostrum was much easier to traverse when it was always Roman water. The Europeans were often blocked from exploring by the more powerful Ottoman empire. The Europeans did not really have the military power to expand beyond Europe until the gunpowder era. The European nations generally were otherwise busy fending off the Muslims in Spain and the Balkan until the age of discovery. The muslim states of North Africa also were powerful foes and passing their realms was required to explore around Africa which was not easy. The Pax Mongolica reigned across the land and European traders much preferred to travel across the Mongol Empire to the East rather than risk the seafaring past hostile Muslim states. Only after the defeat of the Muslims in Spain did Portugal and Spain begin exploring the African continent.

The Muslim nations of Northern Africa and the Levant would have prevented any attempts at colonization. Not to mention colonization was not on Europe's mind until they discovered America and found sources of gold. Colonies were simply too difficult to maintain and defend pre-gunpowder era, thus trade was much easier than conquest. Only after the natives of America were subdued by massively superior weapons did the Europeans mobilize their by then tremendous power to divide up Africa. This didn't occur until the Victorian era as the Europeans did not want African land until the Industrial Revolution fed a need for raw resources and more markets, leading Europeans to forcibly acquire these by colonizing the African continent, which had before seemed useless as it lacked large amounts of Gold and Luxury Goods. Things which China and the Levant had. There was no reason before the need for raw resources to colonize the continent, trade sufficed until the resources of the area were needed. The Americas were different as the Europeans felt the land was uninhabited, unlike in Africa where the land was often divided up by Kings. The Europeans would take opportunistic lands such as the seemingly free lands in America ( that didn't require going past the Barbary states to reach ), but did not make a concerted effort until their industries needed Africa.

Hope that answers that. As always let me know with questions/concerns. Sorry for the bad english, am not a native speaker.