Well... maybe
Think with me: The fan sucks air over the coils... and blows this cold air out the top. In many cases, the temp of that air is below freezing. So where do you think the ice will form first?
May be different on different machines...
This is why I prefer a Demand rather than a Timer defrost board. They tend to catch this sooner... yet not defrost until it is needed.
GA-HVAC-Tech
Your comfort, Your way, Everyday!
GA's basic rules of home heating and AC upgrades:
*Installation is more important than the brand of equipment
*The duct system keeps the house comfortable; the equipment only heats and cools (and dehumidifies)
*The value of comfort, over the long term; leave economic choices behind!
Choose your contractor wisely!