Its actually very easy to solder packages like this and you really don't need paste. Paste is faster and results in less eye strain if your doing a bunch of them, just use a stencil for the paste application (which you can get easily and cheaply online).
The biggest mistake most people make when trying to solder things is thinking they need to do 1 pin at a time. Unless your talking huge pins (DIP-8) you don't want to do this. It is actually worse for the chip going pin by pin, you end up heating it up more and for a longer time.
Instead apply flux to the board, position the chip then "tag" opposite corner pins with solder to hold the chip in place. From there add more flux to the pins and use very fine solder (this is key) + a fairly fat solder tip, like a 1/4" chisel, just drag it down the each side of the chip while applying enough solder to suck onto the pins. You can do the entire chip in about 60 seconds.
Chips that actually suck to hand solder are things like QFN, PLCC (with small pads), and anything with a center pad (especially if its a thermal connection to the ground plane). You can hand solder such packages but its a serious pain and really can only be done correctly with a hot plate and hot air station. Small parts suck also, 0402/0201 or smaller resistors or caps are not fun to do without without paste + reflow.
EDIT: I should add that land pattern makes a big difference too. High density land patterns are much more difficult to solder correctly without paste + hot air or reflow.
It's sort of a moot point with this Cortex A8 IC though, because the RAM it needs only exists in a BGA package.
In the absence of a hot air of infrared source, use a flat chisel tip about 3mm wide and fine solder to do a QFP.
Align the QFP on the pads. Alignment is crucial, since by not heating all pins at once you lose the self aligning of packages aspect of the surface mount process. Maybe tack diagonally opposite pins with a little solder, or lightly hold it in position. If you are right handed, have the iron in your right hand and solder in your left. Have one side of the QFP facing you. Start at the left hand corner and (if you are right handed), sweep from left to right, keeping the flat chisel in contact with the part of the pins, trailing across so it is in contact with the pads. Simultaneously feed the solder into the junction of the pins and iron with your left. It takes some practise to get the speed of the sweep and the rate of solder feed correct, so getting the correct temperature and amount of solder. Get it right and it takes a couple of seconds to solder one side of a QFP, with a single sweep. Turn the board 90 degrees and repeat for the other three sides.
If you get solder bridges, reheat, maybe using a little flux or removing some solder if there is two much. If things are clean and there isn't too much solder, surface tension will "magically" pull the solder from the bridge back onto the pins.
I've used the above technique down to 0.5mm pitch.
(Side note: Essentially had to be able to solder surface mount packages to pass a class in college.)
It's surprisingly easy and i've had no issues on up to tqfp144's.
- Apply the paste to the PCB using the stencil
- Carefully place all the components using the magnifier
and appropriate tweezers or vacuum pickup pencils
- Place in the oven or hot plate
- Carefully ramp up and down the temperature as required
TQFP can be done with common and cheap items like a cheap soldering iron, a flux pen, some copper wick and a pair of tweezers.
Here's someone who wrote about the proposed approach: http://www.instructables.com/id/Toaster-Oven-Reflow-Solderin...
It goes something like this:
- Mask everything around the component to be soldered with masking tape
- Flux as usual
- Place component down and align it
- Tack on the corners in order to ensure alignment
- Don't worry about solder bridging
- Now, apply solder to the pins
- Use a healthy dose
- You actually want an entire row to be brideged
- You should see a solid strip of solder across all pins
- Get all four sides done the same way
- Now, take the iron and heat up one of the beads of solder to the melting point
- Without any delay, hit the board edge-wise on the table
- The molten solder will come flying out
- A small amount of solder (just enough) will remain on the pins
- With practice you can get perfect factory-looking joints with no bridging whatsoever
Obviously, if you have a lot of parts on a single board you are entering territory where reflow soldering in an oven is a far better idea.
Having done boards with FPGA's as large as 1152 balls (definitely not soldered by hand) I can tell you that good board houses produce good product and the difference wouldn't be much, if any between a controlled-impedance board for an A10 project versus an equivalent-sized BGA device.
This is important, so I'll repeat it: The A10 requires a controlled-impedance board.
EDIT: Just learned that the A10 requires DDR3. So BGA's are the order or the day. Hand-soldering with a soldering iron is simply not a reality for such a board. If you want to assemble one yourself you have to use a stencil and an oven or hot plate for reflow. Not that hard for small quantities.
I should also note that I've only done this when absolutely necessary. It makes a lot more sense to pay to have SMT boards assembled. It's not that expensive and assembly shops have all of the right equipment to get it right. With BGA's you really need to have full inspection (including X-Ray) in order to ensure proper attachment. This is particularly true in the case of high-speed boards.
The real advantage here is not the savings in the soldering soldering but the savings in PCB complexity and cost. A small BGA with a few hundred pins will need at least 6 or more layers to be able to "break-out" all the pins from underneath the chip. With the TQFP package, all the pins are already at the edge of the chip, so it's possible to use a 4 layer PCB.
It's an exciting time when more people can have access build thing using this level of hardware. Now the next thing we need is decent documentation to go with these chips.
The biggest savings comes from avoiding blind and buried vias which are still expensive to use but often required for dense BGAs. You can also usually get away with a larger minimum feature size (trace width) with a QFP which can also be a nice cost savings in the PCB construction.