SMD Inductor Soldering Tips wanted - Page 1
Forum section: electronics / beginners

author: laus
author_rank: Contributor
timestamp: June 15, 2019, 09:51:07 pm
content: I had these little boards to solder. The inductors were a pain since the soldering pads on them are on the bottom side. On top of that, the PCB didn't allow for any exposed pads on it either. Capacitors were easy, The PCB had extra large pads for them and the component has the pads on all sides as well.Are there any tips to solder these inductors with an iron or do I need to invest into a hot air gun for that kind of work? Package size of these are 1008 (2520 metric).

author: cur8xgo
author_rank: Regular Contributor
timestamp: June 15, 2019, 09:55:46 pm
content: pads look like they are on the bottom and a little bit on the sideregardlessput a bump of solder on ONE of the padsclean tip very welltweezer on inductor hold onto padsbroadside tip onto pad that has bump of solder, once it flows drag tip along joint until its freeon other pad, put a small blob of solder onto tip then immediately touch to pad/pin jointfeed small amount of solder into that joint if neededEDIT: looks like your joint on those other parts are pretty cold lumpy. practice your broadside on them so they are smooth and shiny"broadside drag" that isEDIT2: As a separate strategy: could pre-blob solder onto the inductor pins and then hold them down onto the pads and broad side each to flow..but I wouldnt do this unless you had no choice

author: thinkfat
author_rank: Unknown
timestamp: June 16, 2019, 08:19:44 am
content: A hot air station is not an investment, it's a 50 bucks delivered on Amazon. Do yourself a favor and get one.Gesendet von meinem Nokia 6.1 mit Tapatalk

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 16, 2019, 12:33:42 pm
content: Pretty general advice should pay off I think.In addition to the above:Use flux liberally. Practice with leaded solder if possible (the lower melting point and viscosity help greatly).After tinning one pad, position the part with tweezers, and solder that pad. This way the part sits flat on the board, you can center it perfectly over its footprint, and complete one solder joint. Move to the other side and solder that.If you're doing the PCB design as well, prefer longer pads -- more open soldering area means more contact for the iron's tip. This is less important on side-metallized parts (most chip R/L/Cs), but bottom-metallized parts like this (and a lot of LEDs, and some diodes) absolutely require it -- else you need a hot-air machine.Also, get a soldering iron tip that's wedge shaped rather than rounded or conical. The larger radius rounded tips won't even reach smaller pads!If you're doing a lot of SMT, seriously consider a hot air machine. The cheap ones are quite affordable (if sketchy as hell to operate*..), and being able to shove around parts without having to poke an iron at it, without wasting solder, and without burning anything, is so much better. (By all means, do get good with the soldering iron first, though!)*Thin wiring, poor grounding -- safety stuff like that. Expect it to burst into flames at any time, and plan accordingly.Tim

author: laus
author_rank: Contributor
timestamp: June 16, 2019, 01:44:42 pm
content: Quote from: cur8xgo on June 15, 2019, 09:55:46 pmThat's what I tried to do first. That solders the inductor nicely to the first pad. But the second pad is totally covered. The soldering iron tip now has no chance to touch and head up the second pad. I could't get heat and solder onto it, even with flux pre-applied to the pads.QuoteThe first one (top center R100) I messed to long with it and melted the top cover. That's why I was afraid applying heat for to long. I've been using 650 degrees Fahrenheit, pre-soldered both pads, and put them kind of angled on there so I could touch some of the soldering location.I'm now thinking of getting a hot air station, heat the inductors and move them into place. In my head it sounds easy and looks much nicer. I don't have a clue if the reality plays out like that.

author: KL27x
author_rank: Super Contributor
timestamp: June 17, 2019, 07:50:29 am
content: QuoteYou already have and use flux? Oh dear.Hot air is very handy, and it can be very inexpensive. 858D.To solder this in a pinch? If there is absolutely no sidepad and zero exposed pcb pad*, and all you have is an iron, you can try leaving a small airgap on the second pad (or.. just pre-tin both pads), and then use a tip with a sharp edge while feeding solder. Many chisels are rounded like a Fisher Price toy. They often intentionally have a trapezoidal/screwdriver tip that is a bit radiused/melted; even if it had crisp edges, those TWO edges at the tip would each be > 90 degrees and can't truly get into a corner. Knife tips and bevels tend to have crispy edges that are <90 degrees at the tip.And use more flux.*The inductor at the top right appears to have a bit of exposed pcb pad around the edges. I think you might be able to solder those normally with a crispy bevel or a knife.

author: cur8xgo
author_rank: Regular Contributor
timestamp: June 17, 2019, 04:10:16 pm
content: Quote from: KL27x on June 17, 2019, 07:50:29 amI second this.Another strategy:Assuming there is zero side pad (looks like there is though?), just put big bumps on both pads. Then put the inductor on top and reflow the pads. Bump size needs to be big enough to where you can transfer heat broadside with the tip. Will likely end up tilted or a bit wonky but way better than buying a hot air setup.Also..a poor mans hot air setup is a $15 heat gun with some tinfoil to direct the heat where you want it.Another poor mans setup is a garage sale toaster oven with some tinfoil. If you are lucky could put bumps on all the pads, place your parts, then reflow for 2 minutes and everything will settle so you dont have to get paste and make a stencil. Might have to spread some flux around first. If you make a minor amount of effort you can evolve this setup into a fully functional reflow oven (and I don't mean spending months on a reflow oven project..I mean a couple days adding a off the shelf PID controller for temperature and placing a thermocouple near the work to close the loop)Even if you did have to get paste, its very cheap on ebay in a syringe, but will take a few days to arrive. Stencils are cheap these days too, but if you are doing a low parts count board, could possibly use a syringe or toothpick and just tab paste where it needs to go.

author: KL27x
author_rank: Super Contributor
timestamp: June 17, 2019, 11:19:18 pm
content: QuoteYes. But if there's any tip that will be able to flow both joints at the same time, I imagine it's a knife tip.