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

Picture of 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

Picture of The Solder and Soldering Iron Tip

Step 2: Cut Tiny Chunks of Solder

Picture of Cut Tiny Chunks of Solder

Step 3: Pick a Piece of Solder

Picture of Pick a Piece of Solder

Step 4: Place the Piece of Solder

Picture of Place the Piece of Solder

Step 5: Melt the Piece of Solder

Picture of Melt the Piece of Solder

Step 6: Place the Component

Picture of Place the Component

Step 7: Solder the Component

Picture of Solder the Component

Now it is fixed in place!

Step 8: Place Next Piece of Solder

Picture of Place Next Piece of Solder

Step 9: Solder the Next Leg!

Picture of Solder the Next Leg!

Step 10: Inspect the Contacts

Picture of Inspect the Contacts

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

Step 11: Repeat the Process!

Picture of Repeat the Process!

Step 12: The Next Completed Piece

Picture of The Next Completed Piece

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

Comments

Victor805 (author)2017-09-27

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

jumson (author)Victor8052017-09-27

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!

Victor805 (author)jumson2017-09-30

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.

drmpf (author)2017-09-24

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.

DavidM496 (author)drmpf2017-09-29

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

drmpf (author)DavidM4962017-09-29

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

DavidM496 (author)drmpf2017-09-29

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

jumson (author)drmpf2017-09-26

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

Jesper MartinS (author)2017-09-27

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.

jumson (author)Jesper MartinS2017-09-27

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

Jesper MartinS (author)jumson2017-09-27

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

EMCguy (author)2017-09-26

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.

jumson (author)EMCguy2017-09-27

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

donpin (author)2017-09-25

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)!

jumson (author)donpin2017-09-26

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

donpin (author)jumson2017-09-26

Here you are Jumson ....

jumson (author)donpin2017-09-27

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

RobertM463 (author)2017-09-26

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.

jumson (author)RobertM4632017-09-27

Thanks for the description, sounds like a good technique I'll have to try!

keesj (author)2017-09-27

Soldering.
Placing the ic on the pc board can be done with a piece of tape in the beginning of soldering the components onto the board.
However when the surface of the pcb becomes not flat for instance with elco's then the tape is useless.
With a piece of a tape with a doublesided adhesive, with the component attached to it and to the tool which brings the component between the components on its place. Then with an uv glue pen and a small drop on the part and pcb board will stick the component to the board. You can now take the tool away with the tape on it.
In this case you work with 2 hands.
The right hand brings the glue on the component and after that the uv light on the glue bubble. Now it can be soldered on the pcb.
When many components have to be soldered choose the flat ones first.
What also helps is to pre solder the component pens and ends of components and copper strips on the pcb. The components are being placed in a hand with magnifying glasses. This method will prevent soldering with to much solder.

Mauricio V (author)2017-09-26

Nice Idea Cutting small pieces of tin solder , brings the exact quiantity of flux inside the solder and also makes rework easy , i fyou have problems with exact positioning you can put a simple little drop of paper adhesive , the simplest one used in kinder, position everything exactly and then the adhesive will mostltly disappear ,afterb soldring , clean then please.

jumson (author)Mauricio V2017-09-26

Good idea using a little paper adhesive -- maybe super glue?

RickL70 (author)jumson2017-09-26

If you use super glue you'd better get the placement right the 1st.time! 0~0

baecker03 (author)2017-09-25

the adafruit pcb ruler is pretty handy for smd identification and measuring.

jumson (author)baecker032017-09-26

good idea, I think i'll get one to show better reference sizes.

gm280 (author)2017-09-25

Nice idea there and that can help control having too much solder on SMD. However, the SMD can get so small that unless you have the exact type soldering equipment needed for the extremely small parts, you're in for some frustrations at best. Once you get down to the 0402 and 0603 sizes, it is near impossible to solder with any typical soldering iron. The parts are so small that without a microscope (or at least an eye monocular), you would have a hard time even identifying the correct sides to actually solder. But you have a good post here.

jumson (author)gm2802017-09-26

Interesting. I'l need to keep an eye out in case those are included in any kind of kit!

jimkindsvater (author)2017-09-25

One huge assistance to this process is a flux pen. When you melt solder - as on the first pad - the solder flux boils off, leaving the solder resistant to further melting. An inexpensive (US$ 5 or so) flux pen with the type of flux in your solder (rosin, water soluble, no-clean) will help you remelt the solder and attach the part. Also, if you have to move the part (correct alignment, etc.) extra flux will again allow the solder to wet, making the process easier.

Another good investment if you're going to do much SMT soldering is a temperature controlled soldering iron with a variety of tips. For about US$60 to $70 you can get a nice unit which won't give you too much heat for smaller parts, but will add heat as needed for heavier parts.

Also, be sure to clean your tip a lot during the process. There is so little solder involved that contaminants can negatively affect the joint easily.

Good luck!

jumson (author)jimkindsvater2017-09-26

Yes, I've heard flux can make everything easier! I use this somewhat cheap Weller station: https://www.amazon.com/gp/product/B000AS28UC which lets you control the heat, but not as clear what the temp is, only you can go higher or lower.

frarugi87 (author)2017-09-25

When I was working at university, I usually had two choices of solder. I always opted for the bigger one rather than the smaller one, since there was more flux and so the solder went much smoother. Also the tip size, as long as it is a reasonable size, is not so much important.

When you arrive at a very fine pitch (e.g. 0.5mm), what I found was the easiest was to make a Big Blob(TM) of solder on all the pins, then remove the solder in excesswith the tip. If the solder has a good flux inside and the board has silkscreen, it is very easy to solder even very fine pitch ICs.

At home I also have a desoldering gun, so removing the excess solder is really easy. Make a Big Blob(TM), suck up all the solder you can, touch each pad with the solder again so you make a Good Looking Solder Blob(TM).

jumson (author)frarugi872017-09-26

Thanks for the tip. Why do you write Big Blob with the (TM)?

abell21 (author)frarugi872017-09-26

My process was much the same as yours, but I used flux pen, then ran the iron across the legs to get Big Blob(TM) at the end, then solder wick to remove.

krn1978 (author)2017-09-26

I never tried to cut solder into pieces. I solder one of contacts (corner one), after it I heat it again, placing IC on its place. After it I solder other corner leg of IC. After it my IC is placed well and doesn't move when I solder it. I use flux that makes my solering easy. Because my english isn't good (I don't trust my knowledge of it) it's better to show you a movie (not mine, but, imho, the best): https://www.youtube.com/watch?v=b9FC9fAlfQE&t=1123s

jumson (author)krn19782017-09-26

Your English is good enough for me! Thanks for the suggestion, I know I need to get some flux as I hear it makes everything easier.

hareeshgs (author)2017-09-26

Thumbs Up.

jumson (author)hareeshgs2017-09-26

Thanks!

mgoyard made it! (author)2017-09-26

I would say that the main issue is to block the component before and during the soldering process. I experienced it in two ways : a paperclip for the IC, bend and unfold for medium boards, and small bits of double-face adhesive tape (those from 3M do not melt) on the opposite pad of the one of the component to be soldered.
I prefer using a large but sharp iron tip, this gives a swift and constant melting result as well as very precise when well oriented. See 7mm T-K shape. I also tried the so called soldering cream to stick component to board but it appeared to me that it melts at a too high temperature to be really effective.

jumson (author)mgoyard2017-09-26

The paper clip sounds like a good idea -- really any little thing to keep the piece down. I've not yet acquired solder paste.

crowling63 (author)2017-09-26

I use a piece of scotch tape to hold smd to the pcb and solder right through the tape.One corner at a time.Also depending on how many pins on the ic you can bridge all the pins together and then use solder wick to remove excess solder.

jumson (author)crowling632017-09-26

That sounds like a great idea! I'll try the tape. I have not mastered the art of using solder wick, so I steer away from it.

JimG50 (author)2017-09-26

Neat idea to solder only one contact then place part first. Thanks.

econjack (author)2017-09-26

If you can find it, Radio Shack sold .022" solder which had 2% silver in it. Great stuff. I also found some .015" online which also works well.

KingAveGarage (author)2017-09-26

Very helpful, thanks for posting

BeachsideHank (author)2017-09-24

Making solder precuts is a smart move, I think I see a future Instructable on an automatic cutter. ☺

jumson (author)BeachsideHank2017-09-24

That would be neat. I'll be interested to see that.

Tanbam (author)2017-09-24

I do a LOT of soldering, part of my job. These components would be very easy to solder, compared to what I have to work with. On the other hand, I have professional tools.

I've got a simple soldering setup at home, but until now, I normally would bring anything even slightly complicated to my work and do it there. This might change after seeing this instructable.

Normally, I go with the method of putting too much solder on, then using wick to remove the excess. Easy enough to do on my lab bench, with a microscope and a huge assortment of solder tips to choose from, but not so easy on the kitchen table.

Cutting the solder into surface-mount-size pieces ahead of time is genius. I'll be trying this method out in the near future.

jumson (author)Tanbam2017-09-24

Thanks! I appreciate the comments and encouragement!

gada888 (author)2017-09-24

Nice Tutorial

jumson (author)gada8882017-09-24

Thanks!

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