I have a very fine PCB (illustrated in an answer to Soldering with a delicate looking board) but I have discovered that the screwdriver like tip I have seems to be too clumsy to clear solder from so tiny a hole.
If I go and buy an alternative tip what am I looking for?
Firstly, "very fine" is quite subjective when it comes to PCBs. However, the picture you point to
seems to look like components around the 1206 or 0805 size, so I'll answer based on that basis.
Different tips can work well for this size of component depending on the operator and what other tools available. However for a general hobbyist, the a conical (or B series/type) tip with a width of around 0.5 mm to 1.0 mm width is probably the best investment as it will work for most components around this size.
Examples of that type of tip for sale for different soldering iron types can be found with this Farnell UK search. Similar will be available from other element14 countries and other suppliers.
This article Use for different soldering iron tips gives a pretty good round-up of the common tips available and is definitely worth a read.
I'd also say that a fine pair of tweezers to hold components still, a magnifying glass to check the joints and always keeping your tip clear are as important as the tip you use.
It's more than just about the size of the soldering tip. Certainly, as you scale in component size you need smaller soldering tips. The main problem with this however that is that as the tips scales the ability to get heat into the tip and its thermal mass also drops. In an ideal world you really want to have a whisper thin temperature stable soldering tip.
There are a series of precise and very well temperature controlled soldering irons like the MetCal style that work on the skin effect. They deliver the electrical energy to the outer layer of the tip and as a result the outer skin of the tip heats up much more rapidly than trying to heat up the whole mass of the tip. It also places the heat precisely in the zones that can be controlled.
Unfortunately these do tend to be very expensive or much more expensive. But they are well worth the investment especially if you're doing and soldering of SMD. If you're doing this professionally it is worth the investment.
{Note: I do not and have never worked for MetCal I have only used their equipment}
