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Jake

What to do about a PCB pad that is narrower than device???

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I got my PCB for the LM 3414 led drivers in and made one little mistake on the board. I built the foot print per the inductor manufacturer guideline, but there too narrow and I can't get it soldered down. I think my inductor was meant for reflow. I had thought some copper foil could be soldered to the pad then solder the inductor down. The inductor is a 15uh Eaton smd inductor, I guess this is part of the learning curve with PCB! I could scratch my Trace and move the inductor down a bit and then I think I can hit both, but I start getting real close to other parts then.

 

Any ideas or recommendations?

 

Thanks!

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I was using flux, and solder, pads are just to small and to close. I fixed the layout file for the pads to go to the edge of the circle and I made the pads bigger than the inductor pads. But I have 36 of these and don't want to can $90 worth of boards over this. I laid it out per Eaton's layout. I should have verified the component instead of the docs. I know now!

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To make the pad bigger, just scratch off the green solder mask on the track of the bottom connection to the inductor, flux it then tin it with solder. Then solder down the inductor.

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Ah - I see. It's not do much that the pads are too small but that they are too close together. It looks like you'll have to use the upper pad and as Zeke said you'll have to carefully scratch off the solder mask and use the track as a pad for the lower. Maybe also do the same with the top pad and rotate it if that helps. It's not going to look pretty whatever you do.

 

The other option for the lower pad would be a short wire to the through hole it connects to.

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In addition to scraping the lower trace clean, you can also solder a short bare lead to the upper pad before soldering the inductor down. The inductor will then not sit flat. I have done similar with 30ga wire. A drop of epoxy under the component after the board is tested improves durability a lot.

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Thanks guys, at least these are for my use so a bit of extra work shouldn't be a problem. I have a place for 20~ of them. I'm going to tweak the layout to use a bigger rdim resistor as that 0402 sucks.

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In addition to scraping the lower trace clean, you can also solder a short bare lead to the upper pad before soldering the inductor down. The inductor will then not sit flat. I have done similar with 30ga wire. A drop of epoxy under the component after the board is tested improves durability a lot.

That was my other thought some wire or foil so it's still in its circle. I made the new pads go all the way to the circle.

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Can you scrape the green off the traces, tin them, then rotate the inductor into a position where it can contact both traces, even if it does end up slightly off-center from the silk?

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