I have noticed that whenever I try to solder a component with many pins close together (like an IC), I get tiny bridges of solder, which shorts the pins. Is there any easy way to solder SMDs without solder bridges?
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asked Jul 19, 2017 at 0:12
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4\$\begingroup\$ Use a thinner tip, and thinner and less solder. It's useless on top of the pins anyway. You can use solder wick to remove those bridges. \$\endgroup\$– JankaJul 19, 2017 at 0:16
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6\$\begingroup\$ Flood the area with thin Flux (either rosin or no-clean). Make sure that the soldering iron tip is clean and well-tinned. Hold the board at a slight angle and let the molten solder flow onto the tip. \$\endgroup\$– Dwayne ReidJul 19, 2017 at 0:16
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11\$\begingroup\$ One approach is to intentionally flood the pins with solder then use solderwick [sometimes also called desoldering braid] to remove the excess and bridges all at once. \$\endgroup\$– Kevin WhiteJul 19, 2017 at 0:25
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4\$\begingroup\$ Flux, Flux, Flux, IMHO after you tack one corner pin, drag soldering is the easiest way to solder leaded SMD by hand \$\endgroup\$– sstobbeJul 19, 2017 at 1:05
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1\$\begingroup\$ As mentioned, the key is liquid flux. See this video on "drag-soldering" \$\endgroup\$– TutJul 19, 2017 at 11:53
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8 Answers
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When soldering by hand, it is easier and faster to just ignore the bridges while you solder the part and then clean it up.
Just put some desoldering wick on the bridge, heat with your soldering iron (may need a bigger tip or more heat) and the excess solder will happily flow into the wick leaving perfect solder joints.
With practice the cleaning of even large parts just takes a few seconds.
answered Jul 19, 2017 at 0:28
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\$\begingroup\$ For some reason almost all instructions on using solder wick miss the crucial bit. It works properly on spots that already have solder in it. So the first thing I do is to actually melt some solder directly on the wick and after I'm finished I have a length of thoroughly impregnated solder wick. \$\endgroup\$ Jul 19, 2017 at 11:56
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5\$\begingroup\$ @Barleyman that is not necessarily true. In my experience it is enough to put a clean spot of the wick onto a joint and press down with the iron so the joint is heated through the wick. As soon as the solder becomes liquid, it will flow into the wick. If it doesn't work first time, a little bit of flux on the joint will help. You do need a good bit of patience and of course YMMV when using non-leaded solder tin. \$\endgroup\$ Jul 19, 2017 at 12:03
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\$\begingroup\$ @iFreilicht Yes, you can do it without "wetting" the braid first but since it's so much easier to do by pre-tinning it, why not do it? \$\endgroup\$ Jul 19, 2017 at 12:04
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7\$\begingroup\$ By putting solder into your braid you can't remove as much solder before it becomes saturated. I always use clean desoldering braid and have never had a problem with it. \$\endgroup\$– user103993Jul 19, 2017 at 12:05
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7\$\begingroup\$ Personally I put a small amount of flux on the wick rather than solder. It helps the heat transfer from the iron to the wick and cleans the copper on the wick so that it'll work better but without diminishing its solder holding capabilities. \$\endgroup\$– AndrewJul 19, 2017 at 16:02
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There are three golden rules in hand soldering: 1. Use a lot of flux; 2. Use more flux; 3. Use even more flux.
Rosin-based mildly-activated flux (RMA type) helps a lot.
And, of course, right iron power, clean tinned tip, sharp tip (I prefer), and right iron temperature for the solder you are using.
answered Jul 19, 2017 at 0:44
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Forget the old soldering iron method.
Solder paste (and a heat gun) is your friend. This method is MUCH easier and faster than soldering each connection!
Assuming you're soldering components on one side of a bare board:
- Put a small (appropriate) quantity of solder paste on each pad; for ICs, you can put a continuous line of paste across all the pads on both sides.
- Carefully place all the SMD components over the paste
- Heat the underside of the board with a heat gun.
All the components will be simultaneously and neatly soldered in seconds, with no solder bridges and much better looking than with an iron!
I bought mine from http://kd5ssj.com/solderpaste. The technique.
A video there showing how it's done, but there are much better videos on YouTube.
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1\$\begingroup\$ This, plus if you are doing a lot of re work you could use a skillet and a small iron to combine to the melting temperature. sparkfun.com/images/tutorials/ReflowToaster/… \$\endgroup\$– danielJul 20, 2017 at 9:16
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If you design the PCB by yourself you could make a "solder thief pad" also used in wavesoldering. this extrapad will take all the excess tin.
In addition you should use lot of flux. I would recommend you to try diffrent brands and find the best one for you.
You can also try to use gull wing soldertips. I have one by myself and with the right flux i rarely have to clean up with solder braid. But when i have to, it isn't the end of the world.
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\$\begingroup\$ I'll second the mention of gull wing solder tips. The tips with dimples make this really easy. \$\endgroup\$– JDBJul 20, 2017 at 4:07
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In addition to the excellent suggestions already provided. Solder bridges are a fact of life even for the most experienced tech. I find that cleaning the iron tip and then drawing the bridge away in a perpendicular motion to the IC (parallel to the pin/pad) is most effective for me. Oh and regardless of how much flux you use, always clean it afterwards, even the "no clean" flux. Your boards will be much more reliable and long lived.
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\$\begingroup\$ +1 for cleaning afterwards, especially the "no-clean" part. The no-clean fluxes tend to be hydrophobic and may become conductive, unpredictably, under elevated humidity, and with typical high-impedance CMOS ICs this usually causes lots of odd behavior. \$\endgroup\$ Jul 20, 2017 at 7:28
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Clean the tip from excess solder, add flux and just slide iron over all the pins in one slow motion. Tip will pick up some excess tin and deposit it onto the next one which could use more.
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As pointed out, you can clean that up afterwards. Just be sure to put some solder on the desoldering wick first.
Lead-based solder has much lower melting point so it's easier to work with. That's obviously quite toxic so don't chew on it or leave it where kids have access to it. Solder joints are obviously pretty inert so handling it is ok. The fumes from soldering that normally reach your nose are not dangerous, it's mostly flux. Heavier than air part is the bad stuff so do not use a fan to blow the smoke all over the room.
You would likely benefit from a decent magnifying lamp. 5x lamp makes everything bigger so you can actually see what you're doing. They're not that expensive if you shop around a bit.
Don't touch soldering iron tip with the solder wire. Heat the pin/pad and touch solder wire to another part of the pin/pad.
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Besides flux, I'd also recommend using a soldering heat gun for this type of component. Here are some steps you could follow to solder with a heat gun:
- Apply flux on component's pads from PCB.
- Apply tin solder to all pads with soldering iron.
- Apply flux (Again).
- Place component.
- Apply heat with a soldering heat gun (Typically around 15 seconds with 270°C but this depends on the type of tin solder and heat characteristics from the component, which can usually be found on the data sheet).
answered Jul 19, 2017 at 15:10