After soldering THT components, soldering SMD components is the supreme discipline among the soldering challenges. The difficulty increases with the decreasing size of the components.
SMD stands for “Surface Mounted Devices” and is sometimes referred to as “SMT”, which means “Surface Mounted Technology”. Both terms refer to an assembly technique in which electronic components are soldered to the surface of the PCB. In contrast to THT components, SMD components are not inserted through the circuit board, but only placed on them and soldered in the correct position.
What sounds daunting at first is actually not. Of course, most SMD components are a bit smaller and the handling of tweezers also. Even a magnifying glass is sometimes necessary. But in addition, SMD components can sometimes be soldered even faster and easier than THT components. Easier and faster because there is no longer the annoying “insert component, fix component, turn over the circuit board, solder component …”-game that you may already know from THT components, needed. This will result in a “put on, solder, and finished”.game. So once you are skilled in “SMD soldering” you save a lot of time. In addition, many components are now only available in SMD form. This also saves space in the design of the circuit board.
So you can already tell: SMD technology offers several advantages. So that getting started is not that challenging, here are a few tips for soldering SMD components.
Hints for our lovely english readers: Basically, many of the articles on Nerdiy.de are translations from the original german articles. Therefore, it may happen here and there that some illustrations are not available in english and that some translations are weird/strange/full of mistakes or generally totaly wrong. So if you find some obvious (or also not obvious) mistakes don't hesitate to leave us a hint about that in the comment section.
Also please don't get confused, that instead of a "dot" often a "comma" is used as decimal separator. 🙂
Inhalte
- 1 Safety instructions
- 2 Affiliate links / advertising links
- 3 Requirements
- 4 Size or housing shape of SMD components
- 5 Solder paste
- 6 SMD soldering with solder and soldering iron
- 7 SMD soldering with solder paste and soldering iron
- 8 SMD soldering with solder paste and hot air station
- 9 Storage of SMD components or how to prevent the popcorn effect
- 10 Which is not/very difficult to solder by hand
- 11 Additional information
- 12 Have fun with the project
Safety instructions
I know the following hints are always a bit annoying and seem unnecessary. But unfortunately, many people who knew it "better" from carelessness lost their eyes, fingers or other things or hurt themselves. In comparison, a loss of data is almost not worth mentioning, but even these can be really annoying. Therefore, please take five minutes to read the safety instructions. Even the coolest project is worth no injury or other annoyance. https://www.nerdiy.de/en/sicherheitshinweise/
Affiliate links / advertising links
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Requirements
Helpful articles:
You can find more helpful information on the basics of soldering in the following article:
Electronics – My friend the soldering iron
Electronics – Loosen, clean and remove components
Required material:
In the following list you will find all the parts you need to implement this article.
Tools required:
In the following list you will find all the tools you need to implement this article.
Size or housing shape of SMD components
Not all housing shapes are shown in the following article. Only the most common
ULN2003A in SO-16 housing
Information about the housing shape: https://en.wikipedia.org/wiki/Small_Outline_Integrated_Circuit
WS2812B in 5050 housing
Information on the housing shape can always be found in the data sheet of the respective component. In this case, the name already indicates the dimensions: the first 50 in the name means that the first edge of the housing is 5.0mm long. The second 50 is analogous: the second side of the housing is 5.0mm long.
| Size Code (inch) according to the EIA standard | length in mm | width in mm | length in inch | width in inch |
|---|---|---|---|---|
| 01005 | 0,4 | 0,2 | 0,016 ± 0,0008 | 0,008 ± 0,0008 |
| 0201 | 0,6 | 0,3 | 0,024 ± 0,002 | 0,012 ± 0,001 |
| 0402 | 1,02 ± 0,10 | 0,50 ± 0,10 | 0,040 ± 0,004 | 0,020 ± 0,004 |
| 0504 | 1,27 ± 0,15 | 1,02 ± 0,15 | 0,050 ± 0,006 | 0,040 ± 0,004 |
| 0603 | 1,60 ± 0,10 | 0,80 ± 0,10 | 0,063 ± 0,004 | 0,031 ± 0,004 |
| 0805 | 2,00 ± 0,15 | 1,25 ± 0,15 | 0,079 ± 0,006 | 0,050 ± 0,006 |
| 0907 | 2,29 ± 0,20 | 1,78 ± 0,20 | 0,090 ± 0,008 | 0,070 ± 0,008 |
| 1008 | 2,50 ± 0,15 | 2,00 ± 0,15 | 0,098 ± 0,006 | 0,078 ± 0,006 |
| 1206 | 3,20 ± 0,15 | 1,60 ± 0,15 | 0,126 ± 0,006 | 0,063 ± 0,006 |
| 1210 | 3,20 ± 0,15 | 2,50 ± 0,15 | 0,126 ± 0,006 | 0,098 ± 0,006 |
| 1411 | 3,50 ± 0,20 | 2,80 ± 0,20 | 0,138 ± 0,008 | 0,110 ± 0,008 |
| 1515 | 3,81 ± 0,38 | 3,81 ± 0,38 | 0,150 ± 0,015 | 0,150 ± 0,015 |
| 1608 | 4,00 ± 0,20 | 2,00 ± 0,20 | 0,157 ± 0,008 | 0,078 ± 0,008 |
| 1812 | 4,60 ± 0,20 | 3,20 ± 0,20 | 0,181 ± 0,008 | 0,126 ± 0,008 |
| 1825 | 4,60 ± 0,20 | 6,30 ± 0,20 | 0,181 ± 0,008 | 0,248 ± 0,008 |
| 2010 | 5,08 ± 0,13 | 2,54 ± 0,08 | 0,200 ± 0,005 | 0,100 ± 0,003 |
| 2220 | 5,70 ± 0,20 | 5,00 ± 0,20 | 0,224 ± 0,008 | 0,197 ± 0,008 |
| 2312 | 6,00 ± 0,20 | 3,20 ± 0,20 | 0,236 ± 0,008 | 0,126 ± 0,008 |
| 2512 | 6,35 ± 0,13 | 3,20 ± 0,08 | 0,250 ± 0,005 | 0,126 ± 0,003 |
| 2515 | 6,30 ± 0,20 | 3,81 ± 0,20 | 0,248 ± 0,008 | 0,150 ± 0,008 |
| 2716 | 7,00 ± 0,20 | 4,00 ± 0,20 | 0,275 ± 0,008 | 0,157 ± 0,008 |
| 2824 | 7,20 ± 0,20 | 6,10 ± 0,20 | 0,283 ± 0,008 | 0,240 ± 0,008 |
| 2917 | 7,30 ± 0,20 | 4,30 ± 0,20 | 0,287 ± 0,008 | 0,170 ± 0,008 |
| 2920 | 7,30 ± 0,20 | 5,00 ± 0,30 | 0,287 ± 0,008 | 0,197 ± 0,012 |
| 3111 | 8,00 ± 0,20 | 2,80 ± 0,20 | 0,315 ± 0,008 | 0,110 ± 0,008 |
| 3931 | 10,00 ± 0,20 | 8,00 ± 0,20 | 0,394 ± 0,008 | 0,315 ± 0,008 |
| 4018 | 10,16 ± 0,20 | 4,60 ± 0,20 | 0,400 ± 0,008 | 0,181 ± 0,008 |
| 4040 | 10,2 ± 0,50 | 10,2 ± 0,50 | 0,400 ± 0,020 | 0,400 ± 0,020 |
| 4320 | 11,00 ± 0,20 | 5,00 ± 0,20 | 0,433 ± 0,008 | 0,197 ± 0,008 |
| 4335 | 11,00 ± 0,20 | 9,00 ± 0,20 | 0,433 ± 0,008 | 0,352 ± 0,008 |
| 4349 | 11,00 ± 0,20 | 12,50 ± 0,20 | 0,433 ± 0,008 | 0,492 ± 0,008 |
| 4424 | 11,10 ± 0,81 | 6,10 ± 0,40 | 0,435 ± 0,032 | 0,240 ± 0,015 |
| 4527 | 11,50 ± 0,20 | 7,00 ± 0,20 | 0,455 ± 0,008 | 0,275 ± 0,008 |
| 4540 | 11,4 ± 0,58 | 10,2 ± 0,50 | 0,450 ± 0,023 | 0,400 ± 0,020 |
| 4723 | 12,00 ± 0,20 | 6,00 ± 0,20 | 0,472 ± 0,008 | 0,236 ± 0,008 |
| 4825 | 12,20 ± 0,20 | 6,35 ± 0,20 | 0,480 ± 0,008 | 0,250 ± 0,008 |
| 5550 | 14,00 ± 0,71 | 12,70 ± 0,63 | 0,550 ± 0,028 | 0,500 ± 0,025 |
| 5727 | 14,40 ± 0,20 | 7,00 ± 0,20 | 0,567 ± 0,008 | 0,275 ± 0,008 |
| 6145 | 15,50 ± 0,20 | 11,50 ± 0,20 | 0,610 ± 0,008 | 0,455 ± 0,008 |
| 6561 | 16,50 ± 0,20 | 15,50 ± 0,20 | 0,651 ± 0,008 | 0,610 ± 0,008 |
| 7565 | 19,10 ± 0,96 | 16,50 ± 0,83 | 0,750 ± 0,038 | 0,650 ± 0,033 |
Solder paste
Correct storage of solder paste:
The storage of the solder paste is a thing that makes the handling of solder paste a little more difficult than that of commercially available solder. While you can normal solder just leave it lying around, solder paste is a little more difficult. In contrast to solder, the flux contained in solder paste evaporates over time. This means that the solder paste will no longer appear as “liquid” over time and can therefore be applied more poorly. In addition, the solder contained in it then also bonds poorly to the respective metal surfaces.
This volatilization of the solder paste flux can be stopped. To do this, you must keep the solder paste at low temperatures – for example in the freezer. But make sure that you keep the solder paste either separately from food or very well packaged in the freezer. Remember that solder paste often contains lead and other substances that you definitely don’t want in your food!
SMD soldering with solder and soldering iron
The soldering of SMD components with solder and soldering iron actually always works on the same principle.
1. Tin a free solder pad – preferably one that is not connected to a large copper surface – with a little solder.
2. Heat the solder on the tinned pad, at the same time attach the component and thus establish a first solder connection between the circuit board and the component.
3. Check whether the component has been correctly oriented / correctly polarized.
4. Solder the remaining contacts of the component.
Resistors/capacitors
Headers
To be added.
Post sockets
To be added.
ESP8266 ESP-12
ICs
The soldering of ICs in the SOP package also works according to the similar principle.
The soldering of THT pushbuttons – pushbuttons that are inserted through the circuit board – is described in the article Electronics – THT soldering components by hand.
SMD buttons can also be easily soldered with solder and soldering iron.
5050 LEDs
LEDs like the “famous” WS2812B also have contacts that are reasonably accessible from the outside. However, the majority of these contacts are located on the underside of the LED housing. For this reason, these LEDs cannot be reliably soldered (with solder and a soldering iron) to the circuit board in this type of housing. Even an initially stable connection can easily break later by bending the circuit board or vibrations.
Therefore, you should better solder components in this type of housing with solder paste.
SMD soldering with solder paste and soldering iron
The procedure for soldering SMD components with solder paste and soldering iron is almost always similar and can be summarized as follows.
1. Coat all solder pads of the desired component with solder paste.
2. Position the component, align it correctly and check whether it is correctly oriented.
3. Without touching the component leg (this could cause the component to slip), heat the solder pad of the first component leg until the solder paste liquefies and the component leg is soldered to the solder pad
4. Check again whether the component is still correct and aligned and oriented.
5. Solder the remaining contacts of the component according to the same scheme.
Resistors/capacitors
To be added.
Headers
To be added.
Post sockets
To be added.
ESP8266
To be added.
ICs
To be added.
The soldering of THT buttons is described in the section THT buttons in the article Electronics – THT component soldering by hand.
5050 LED’s
SMD soldering with solder paste and hot air station
Soldering with solder paste and hot air is really fun once you know how to do it. The big advantage is that you only have to apply the solder paste and roughly insert the component into it. The component, the solder paste and the circuit board/solder pads are then heated in one go by hot air. Due to the resulting surface tension of the liquid solder, the respective component is then “automatically” pulled into the correct position. Components soldered in this way look very professional and save a lot of time, especially with larger numbers of components.
The procedure for soldering with solder paste and hot air can be roughly divided into the following steps.
1. Coat all solder pads of the desired component with solder paste.
2. Position the component, align it correctly and check whether it is correctly oriented.
3. Heat the component, solder paste and circuit board with hot air to the melting temperature of the solder paste until the component “floats” completely.
4. Let the component and PCB cool down.
IMPORTANT: When soldering with hot air, it is important that you make sure that the components you soldered have not absorbed too much moisture beforehand. Otherwise it can happen that this moisture expands strongly during the heating and thereby “blows up” the housing, which would ultimately destroy the component. You can find out more about this problem in the following section “Storage of SMD components”.
Storage of SMD components or how to prevent the popcorn effect
If you want to solder SMD components now or in the future using hot air or reflow processes, you should make sure that they are always packed airtight and in low moisture atmosphere.
Why is that a problem?
Unfortunately, SMD components and the plastic used for them, absorb moisture very easily. The moisture contained in the normal ambient air is sufficient for this. This is absorbed by the plastic of the SMD components and enclosed in such a way that it cannot escape again so quickly. If the component is now heated quickly during the soldering process, the stored moisture expands faster than it can escape from the component. This leads to the concerned components bursting open. That is why this phenomenon is colloquially called “popcorn”-effect.
To prevent this error, it is important that you always store your SMD components in a dry and airtight place. In professional use, there are special drying cabinets for this purpose, in which the air humidity is kept constant at a low level.
Of course, this is a little exaggerated for hobby use. Good results can also be achieved here by storing the components together with a few dehumidifier bags in a sealed plastic bag.
You can also see how sensitive to moisture the components you are using from the – mostly printed on the packaging – MSL value. This MSL (Moisture Sensitivity Level) indicates how long the respective components can be processed after opening the packaging without any damage being expected.
The MSL is divided into the following levels according to the current version of the J-STD-020D standard.
| MSL-Level | “Lifetime” after removal from the packaging | |
|---|---|---|
| duration | conditions | |
| 1 | unbegrenzt | 30 °C / 85 % RH |
| 2 | 1 Jahr | 30 °C / 60 % RH |
| 2a | 4 Wochen | 30 °C / 60 % RH |
| 3 | 168 Stunden | 30 °C / 60 % RH |
| 4 | 72 Stunden | 30 °C / 60 % RH |
| 5 | 48 Stunden | 30 °C / 60 % RH |
| 5a | 24 Stunden | 30 °C / 60 % RH |
| 6 | „time on label“ (TOL) |
30 °C / 60 % RH |
How do you get components that have “become damp” dry again?
In the event that the “child has already fallen into the well” and your SMD components with MSL-6 have been flying around openly on your desk for weeks, there is still some hope. In professional use, you would now let these components dry in the drying cabinet for a certain time. As a home user, you can also let these components dry in a normal oven at 100 ° C for approx. 24 hours.
This costs you some energy costs but can be cheaper than having to order the components again.
IMPORTANT: Make sure to place at least one pad in your oven. The components could be loaded with harmful materials, which should not necessarily end up on your favorite baking sheet. If you want to play it safe here, you can also get a pizza oven and use it exclusively as a drying oven.
Which is not/very difficult to solder by hand
Unfortunately, not every component can be soldered in a controlled manner on the desk at home. For example, there are certain SMD housing forums such as BGA housings have their connection contacts on the underside of the component. This has the advantage that you can accommodate a lot of contacts in a relatively small space.
Unfortunately, this also has one and a half major disadvantages for home users: These components cannot be soldered with a soldering iron, but only with hot air or using the reflow process. In addition, the solder joints cannot be checked or only with great difficulty. In production lines, printed circuit boards with BGA housings are checked after being fitted with an X-ray device. Unfortunately, most home users do not have this option.
Additional information
https://de.wikipedia.org/wiki/Moisture_Sensitivity_Level
http://www.netzmafia.de/skripten/hardware/SMD/index.html
https://makerfab.blogspot.com/2018/09/w-hy-ws2812sk6812-failures-after-smt.html
https://de.wikipedia.org/wiki/Chip-Bauform
https://de.wikipedia.org/wiki/Surface-mounted_device
Have fun with the project
I hope everything worked as described. If not or you have any other questions or suggestions, please let me know in the comments. Also, ideas for new projects are always welcome. 🙂
P.S. Many of these projects - especially the hardware projects - cost a lot of time and money. Of course I do this because I enjoy it, but if you appreciate it that I share these information with you, I would be happy about a small donation to the coffee box. 🙂
Für mich als Einsteiger im Bereich smd bauteile löten ein sehr lesenswerter Ratgeber, vielen Dank.
Super, freut mich. 🙂
Danke für dein Feedback!
Beste Grüße
Fabian
Klasse! Genau so eine Einführung habe ich gesucht. Herzlichen Dank!
Super, freut mich. 🙂 Danke für Dein Feedback!
Beste Grüße
Fabian