How to Solder SMD / SMT Components With a Soldering Iron

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Introduction: How to Solder SMD / SMT Components With a Soldering Iron

Surface-Mount Technology (SMT) and Surface-Mount Devices (SMD) are essentially just tiny little components that are soldered to the surface of the PCB, not through it like many larger components. The Radio-Electronics website and, of course, Wikipedia, have some good overviews of these kind of components.

The purpose of this Instructable is to show how I've successfully soldered some SMD components without any special tools, and to show some techniques you can try. I am not an expert; I'm simply a hobbyist without training; I appreciate all constructive feedback and tips in the comments below!

These pictures were taken as I assembled an ATMEGA328P based Transistor Tester - which I have documented in full, here: https://www.instructables.com/id/Circuit-Circus-in-Depth-Tech/

I thought a more focused Instructable might be helpful for those wanting only this specific information.

Instructables.com automatically compresses the pictures in the Instructable. Viewing the full sized picture may be more helpful in some cases; just click the picture, click it again, and you should see a way to view the "original image".

**Edit - 3 OCT: Be sure to read through the comments for additional great tips and pointers!

Step 1: The Solder and Soldering Iron Tip

Step 2: Cut Tiny Chunks of Solder

Step 3: Pick a Piece of Solder

Step 4: Place the Piece of Solder

Step 5: Melt the Piece of Solder

Step 6: Place the Component

Step 7: Solder the Component

Now it is fixed in place!

Step 8: Place Next Piece of Solder

Step 9: Solder the Next Leg!

Step 10: Inspect the Contacts

I'll provide one more example below, but this is basically how I've done it.

Step 11: Repeat the Process!

Step 12: The Next Completed Piece

And this concludes the Instructable. I hope it is helpful for your projects!~

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49 Comments

I recommend investing in a cheap hot air station and some quality solder paste and flux.

2 replies

I probably will one day, but this instructable was to show a technique for simply using a soldering iron. I do need to get some flux and learn how to use soldering paste, but i've not yet done that. I hear it makes things easier!

I've soldered components with solder paste and hot air and it's really easy, the solder melts and components just stick into place. For IC's with many legs it's also a really fast process.

A few tips:

i) For very small smd, and those with earth pads underneath I use a temperature controlled heat gun (Bosch PHG 630 DCE) set to 320 degC and solder paste. I apply the gun to the underside of the board until I see the solder paste melt and then finish off with a bit of heat from the top.

ii) You often end up with bridged pins after soldering. Clean the soldering iron well and wipe it across the pins so that is picks up the excess solder and removes the bridges

iii) These small chips are easier to handle if you first solder them to a DIP adaptor e.g. https://www.sparkfun.com/products/717 or search "smd to dip adaptor" on digikey.

4 replies

Any idea, where I would get a 100pin smd to dip adapter (Its for a C8051F020)

Go to digikey, enter smd to dip adaptor in the search bar and then, when Adapter, Breakout Boards page shows up, click in the "No of Positions" filter col. scroll down and click on 100

You sir, are a legend and I thank you :)

Great tips, thanks! I'll look into the DIP adapter idea, sounds helpful.

Hi

I´am sorry to say , but you have way too mutch solder on you transistors or IC, it should never end up on the upper side. this will remove the flexibillity in the legs of the component.

4 replies

Thanks, I'll look into that. What do you recommend to fix it? Cut smaller pieces? Or wick/desolder it?

Use tinner solder. If there too much, desolder. But be careful with the amount of heat. Don't exceed 360 degree tip temperature.

Excellent reply, @jumson. And I am TOO, an ELECTRONICS ENGINEER, and I can say that to this day, they still DO NOT teach how to solder SMT components by hand in schools - after having tried (and failed) countless times trying to find a less messy way, I give you my kudos.

Looks like the 'be nice and constructive' policy failed. As a retired electronics engineer myself I applaud the principle behind this instructable. It's just a shame that my eyesight and steadiness of hand are failing or I would try this just for fun...

Soldering at work is a breeze with a zoom microscope and teeny-tiny irons and tweezers. At home I have a standard adjustable temp Weller and a nice flip down Donegan Opti-Visor magnifying visor. If you can spring for the glass lenses, they are worth the money.

The other thing I use is round wooded toothpicks and a block of beeswax. I have terrible luck with parts jumping out of tweezers, so I stroke one end of the toothpick lightly across the beeswax and I can pick up anything 0805 or smaller and transfer it to the board. Just roll the toothpick off the part and use the un-waxed in to push it around. Tweezers have a nasty habit of getting magnetized and dragging your tiny part away when you want to let go of it.

1 reply

thanks for the tips! I'll need to try that. I've launched several parts through the air with my clumsy tweezer handling.

I solder 0204 (1mm x 1/2mm) resistors and other small smd components (on DIY boards with no mask) using a .5mm tip & a 13w Goot iron and one or two goose-neck magnifying glasses stacked.

Lightly pre-solder the pads, then place the resistor and put a light weight on it with a canter-levered weight (a round head pin pressed through a 50mm length of plastic works just fine) to stop the resistor tomb-stoning (suddenly flicking upright). Touch the iron to the pad/resistor to remelt the pre-soldered pad. Clean and tidy.

(PS: If you drop an 0204 resistor do not even bother looking for it)!

3 replies

thanks for the tip. Do you have a picture of what you mean with the canter-levered weight?

Here you are Jumson ....

SMD 0204 Canterlevered hold-down while soldering.jpg

ok I see what you mean now. That should help prevent me pressing too hard and the part goes flying off....

Interesting tutorial. Everyone eventually comes up with their own process that works for them. I've been working with SMD components for about a year now as a hobby and my technique is different:

1. I use a 80W temp controlled iron with a 2.2mm chisel tip, set at 600-670*F, and 0.039" diameter solder, the smallest size possible.

2. When I design a board, I choose footprints with largest pads possible. In Eagle, these are referred to as kits.

3. I use plenty of liquid flux (flux pen or syringe) on the pads, set the part on the pads and align by pushing with tweezers

4. Once in place, I touch the solder to the iron tip (just a little), hold the part in place by pressing it down onto the board with the tweezers and touch the iron tip to the pad. Max. 3 seconds the solder has flowed around the part and I remove the iron.

5. If it's a cap or resistor, I solder the remaining end to the pad. If it's an IC, I repeat the tacking procedure in 4. to another pin to secure the IC to the board and then proceed to apply solder to the iron and touch the iron to the pins.