Thanks for your response.We are thinking to use 1206 SMD Package type.Is it large enough?
It's too big, unless you really need it (power resistors, large caps).
You lose the benefits of SMD (dense integration).
Going beyond 0805 doesn't make it easier anymore, but more difficult IMO. Thermal mass increases. The easy part in soldering SMD is that the solder flows so quickly, due to small thermal masses, that it's not easy to fail in the way that many people fail through-hole components - not heating enough, or not heating all parts (pad + component lead) at the same time.
When designing PCB, don't connect pads directly to planes but use thin and long enough thermal reliefs, and a 0603 or 0805 SMD is actually easier to solder than through hole. The reason is that even without proper connection between iron, component and traces, any solder that melts will touch the trace and component, transfer heat and heat up parts in < 0.5 seconds, way before flux has burned away, providing proper wetting and solder in less than a second.
Going bigger increases thermal masses and also increases the risk of ceramic caps stress cracking when not solder
just right.
IMO, 0603 is a very good size, even for a beginner. 0402 is too small for most beginners. 0805 is generous, and some beginners do prefer it over 0603.
0805 is really the sweet spot from the ease of soldering viewpoint, given properly designed PCB. Easiest component type to solder, ever. Beats through-hole.