Thursday, August 18, 2011

More updates, assembled board and testing in progress

As above, pictures below, those 0402 decoupling capacitors were kinda hard to get in place. A good magnifying glass really speeds things up.

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I assembled the LMZ power modules 1st, they have a huge thermal pad on the back that need serious heat to solder them down.

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Here’s the rest of the power supply section tested. Then I metered the output voltages, all within design limitations, before I proceeded (1.2v and 2.5v, measured was 1.18v and 2.48v).

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Some noise figures, scope was at 0.2mV/div with an X10 probe, 0% load, I need to retest this again at full load and with a better scope, current scope has a bandwidth limit of 20Mhz, which might not be showing everything.

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Then I assembled the rest of the stuff, including the Spartan-6 FPGA, I left some of the capacitors around the sides unassembled so I can visually inspect the BGA soldering quality (didn’t take a picture though).

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Next I tackled the underside, which has some 0402 decoupling capacitors. These were insanely hard to do naked eyed.

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Here’s a closeup comparison with a 0.5mm ball point pen tip.

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This is how I did it by hand (mostly), a good magnifier and strong light helps a lot, you don’t want weird shadows obscuring your view.

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A shot of the completed board through the magnifier. It looks good doesn’t it?

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Here it’s connected to my cheapie Ebay chinese Xilinx platform cable clone, resting on my messy as hell table.

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