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I don't have any experience with hot-air soldering. Would it be possible for a complete newbie to solder this kind of package using a hot-air station:

sim900 http://www.soselectronic.pl/a_info/img_data/c/SIM900.jpg

I only need to solder pads closer to the edges (the round pads closer to the middle should not be soldered).

To give you an idea about how small are the pads the whole package is 24x24mm.

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    \$\begingroup\$ Is the PCB one you're designing yourself? Just for prototyping I've had success just extending the pads out further than usual and a regular iron on fairly similar packages if the copper runs out to the edge. \$\endgroup\$ – PeterJ Feb 22 '15 at 13:15
  • \$\begingroup\$ Is the round bit the antenna connection? If so, you need to solder that as well, which to me says to use a reflow oven. \$\endgroup\$ – Simon Richter Feb 22 '15 at 14:00
  • \$\begingroup\$ @SimonRichter No, the bigger round bit and 9 smaller round pads are not meant to be soldered. They are test points used during module manufacturing. The datasheet even mentions that these areas on the PCB should not contain copper. \$\endgroup\$ – rubix_addict Feb 22 '15 at 14:24
  • \$\begingroup\$ @PeterJ Yes, I'm going to design the PCB myself. \$\endgroup\$ – rubix_addict Feb 22 '15 at 14:26
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Without the BGA pads, that's just a QFN package with 1 mm pitch. Yes, you can solder that with a hot air station.

The way I usually do this is to use a soldering iron to put a bead of solder on all the pads. Then smear paste flux over everything and position the chip over the pads as accurately as you can. A mag light is handy for this. The paste flux acts like goo to hold the chip in place.

Now heat with hot air at around 700°F. Make sure you have reasonable air flow, but no so much that the force of the air can move things around. For a package this large, you need to have one of those nozzles that has a long and thin vent for each side of the package. Be careful to hold the hot air wand steady and centered over the package. It may take 5-10 seconds, but you should see the solder melt. Make sure it is melted all around on all four sides, give it maybe another 2 seconds like that to be sure, and remove the air.

It is important that the solder on all pads be molten at the same time. Molten solder has significant surface tension. In the beginning, some of the pads will be molten, which pulls the chip down against the remaining pads harder. This is how the process deals with the inevitable mismatch of a higher solder beads than others. Once the solder on all pads is melted, they all pull together to line up the chip nicely with all its pads.

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It is actually possible to solder it with a standard soldering station. We used the SIM900 in a project last year, we hand soldered 25~ of them, It worked perfectly fine. Both with soldering wire and soldering paste.

I tried to "answer" this as a comment but I dont have enough rep.

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It can be done with the use of solder paste and hot air method. I have soldered a number of these in the past i usually perform a preheat method as well as the hot air to ensure solder paste will flow evenly.let me know if you need help

a little bout my soldering skills http://www.turbotronicstech.net/work-history.html

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