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I am searching for a method/device for aligning chips with pins/pads underneath, like QFN, LGA, BGA and others. I've been searching the Internet, but I could find anything except expensive (several k€) chip alignment machines.

Is there a method/device for aligning chips, different from the expensive chip alignment machines?

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    \$\begingroup\$ If this is for your personal use, you don't have to be very accurate aligning things by hand, I've seen chips almost rotate into place when you put them in the solder oven. \$\endgroup\$ – jramsay42 Nov 26 '17 at 11:15
  • \$\begingroup\$ @jramsay42 It is for prototyping. \$\endgroup\$ – Cristian M Nov 26 '17 at 11:16
  • \$\begingroup\$ What @jramsay42 is talking about is the surface tension. In an oven everything will automatically snap. As long as the components you are soldering can float on solder. So a 100 gram inductor won't snap. But every IC will more or less snap. \$\endgroup\$ – Harry Svensson Nov 26 '17 at 11:37
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    \$\begingroup\$ If you might eventually use machine assembly, you should add appropriate fiducial marks to the panel, the board and even right next to the component, depending on how fine the pitch of the part is. Something like a 1mm diameter copper pad with the solder mask pulled back to 2mm. \$\endgroup\$ – Spehro Pefhany Nov 26 '17 at 16:00
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There are two stages, the initial alignment, and then keeping alignment during soldering.

Machines are necessary for volume runs, but for prototypes a microscope will suffice for initial alignment. You need to have the board marked with alignment marks. This should be in copper, not legend, so there is no build up of tolerance between different layers.

Solder paste on the pads will be sticky enough to retain most ICs in sufficient alignment in the short trip between the microscope and the oven. As the solder melts, the strong surface tension forces will improve the alignment, pulling the IC terminals into the centres of the copper pads.

An alternative to relying on the stickiness of solder paste is to glue the IC in position. This obviously needs to be done more accurately, as the solder process will not improve the alignment.

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