Flux is a big help there since it makes the solder flow a lot better so you get a more even amount of solder on each pad. To tin the pads i just put flux on the board and drag a soldering iron across all of them with plenty of solder on the tip. A multimeter on diode test can be used to check for any pins that did not connect properly (To fix that you can sometimes just heat it up using a hot air station and tap the top of the chip gently) If there is enugh room around the chip you can even shine a light trough the space between the balls from the other side to check there are no bridges. When you did it right you can see nice round balls that are squashed down to about half there height by the weight of the chip, they should not be dragged off to the left or right too much as that shows the chip is not aligned all that well. Once you are done you can peek under the chip by looking from the side.
#Hot air reflow manual#
Then finally put it trough a reflow soldering oven (But a hot plate is fine too once you 'dial in' your manual temperature profile).
Carefully place the BGA in its location since you don't want to move it around too much or the paste will get messed up underneath. Buy a paste mask for the PCB (They are pretty cheap from china), lay it on the board, squeegee some qood quality leaded paste across to print it onto the board. My preferred method of doing it is what user "cgroen" said. I did that for 0.5mm BGA chips before and had it work, but does take a little bit of practice and some magnification to make sure its centered well enough. Heat it with a hot air gun until it moves over a bit as the surface tension centers it, gently tap it down with tweezers to make sure its down properly and let it cool back down. Its possible to reflow a BGA onto a board by tinning the pads while making sure the bump you leave on each one is the same size, rub a small amount of flux over the board, place the chip as precisely aligned as you can. The flux you want is usually the more liquid stuff in a syringe. First of all don't duplicate your treads over the forum, and try to edit your previous post when you have something to add rather than adding a reply No problem in mixing it, just use lead where ever possible because it makes things easier.
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