Electronics > Beginners

How to resolder an inductor to PCB?

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weriw:
Hello, I would like to solder inductors that has fallen away back to their place on PCB and would like to ask for some advices.

I have a power board (DC/DC converter and battery charger) from an old laptop and 3 inductors (all 10 uH) have fallen away. Please, take a look at the photos. I'd like to reattach them back to the board (either these 3 or 3 new ones). How should I proceed? I searched for advices about soldering surface mounted component and found suggestion to first solder one pin and then the second one. I don't think that is possible in my case, since pins extend less than 1 mm from the bottom of the inductor.

- Could I solder both pins at the same time by heating two small drops of solder on PCB and then quickly and gently pressing the inductor onto them?
- Do I need to clean the board and the pins? I believe there was solder paste used, but I am not certain.

Ian.M:
Short of reflowing the whole board in a temperature profile controlled reflow oven, there's no hope of fixing that properly without a hot air rework station, preferably with a board preheater as well.   The pads of both the inductors and board must be cleaned, probably best done by re-tinning them with solder using an ordinary iron then brush and wick off as much solder as possible, then finally scrub with IPA or flux remover using a Q tip.  Then you'd be ready to apply solder paste, and position and reflow the inductors.

If there's enough clearance in the housing, you might be able to get away with bodging it by hand-soldering very short jumpers of magnet wire between the board pads and the inductor pads then squishing the inductor into place on a blob of neutral cure silicone sealant or other non-corrosive resilient heat resistant glue.

weriw:
Thank you for the suggestions. Would it make sense to turn the inductors on their side (rotated by 90 deg.) then solder the short jumpers you suggested?

Bud:
Seems to be a sizeable inductance value, just mount in a convenient way and solder with wire jumpers.

Ian.M:
You really should avoid mounting them on top of other parts of the circuit where their magnetic field may induce voltage in nearby tracks, possibly disturbing normal operation.

Due to the close packed components and tracks, there's nowhere good to mount them sideways and still keep the jumpers short, and the PCB pads accessible for soldering, hence my 'squish down in place' suggestion.

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