Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [surface-mount]

Surface-Mount Technology (SMT) refers to the way components are mounted on a PCB: SMDs (Surface-Mounted Devices) have pins or contacts which lay on top of the PCB's pads, without the need for holes in the PCB.

SMT in PCB production became widely used in the late '80s.

SMT advantages:

  • Space-saving: since the components don't need mounting holes, both sides of the PCB can be maximally used.

  • Miniaturization: saves space. Components can be as small as 0.4 mm (01005 resistors) or 5 mm2 16-pin ICs, e.g. the LPC1102UK:
    enter image description here

  • Cost-saving: smaller components use less materials, and SMT needs less holes to be drilled in the PCB.

  • Less inductance: shorter connections have less inductance than PTH components, which increases maximum frequency.

Wikipedia: Surface-mount technology

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Why are power supplies almost always made using through hole components?

Why are power supplies almost always made using through hole components? Every computer PSU I've taken apart uses through hole components, though occasionally (not in all cases) surface mount components are found on the bottom. Don't these have to…
Thomas O
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Why are SMD resistors marked with their value, but SMD capacitors are not?

Why are SMD resistors marked with their value, but SMD ceramic (and similar) capacitors are not? Most SMD resistors, even the very small 0402 and 0603 ones, have their values written on them. Most SMD ceramic caps are not, I haven't to date seen a…
Thomas O
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How to assemble PCBs when SMT machine doesn't have enough feeders?

I just got access to an SMT machine in a DIY fablab. I have a board that has about 50 unique components that I wish to assemble and test drive this new machine. I intend to make 20 of these boards. How should I go about it? Do I load the 15 of the…
ankitm
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TSOT-23-6 vs SOT-23-6

What is the difference between a TSOT-23-6 and a SOT-23-6? I know one is thinner. But in what dimension? I have looked in my PCB editor and they both have the same footprint. Any clarity appreciated!
Thomas O
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SMD package size chart

Is there a scale drawing of SMD package sizes as a design aid? This could be useful in schematic/layout stages of a project in when deciding to trade off size vs. cost.
Vanush Vee
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What are the disadvantages or advantages in using larger SMD resistors and capacitors?

Are there tradeoffs associated with usinng SMD resistors or capacitors larger than a 0805 footprint? As the footprint becomes larger what considerations should be made?
JeremiahOgletree
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How do you know which way round a 6-pin SOT23 goes?

Well, I have a 6-pin SOT23 and it is absolutely tiny. When I say tiny I mean it. Anyway, it is unclear which way it goes around as it has no indicator, so I don't know how I can install them on my boards. It has some writing on it but that is the…
Thomas O
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Voltage rating for SMD Resistor

Is it safe to use the 330K, 1206 pack as shown or to use 2x of 115k,1206 resistors in series? Input is 230v AC.
John
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0402 Land Pattern

I'm working on the second iteration of a board which uses quite a lot of 0402 caps for decoupling around processors. On the first version of the board I had complaints from the subcontractor that there was a lot of tombstoning on these caps, not in…
Redeye
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Advantage of using SMD components

I know that SMD components are smaller in size compared to their through-hole equivalents. They enable a designer to reduce overall pcb size. Is there any other advantage of using SMD over through-hole components ? By other advantage i mean benifits…
Fern24
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Mount SMD component raised 45 degree from board

My challenge is, how can mount a SMD component in a 45 degree angle raised from the PCB. I am doing a temperature sensing device, which is intended to be mounted on a wall, hence the PCB will be parallel to the wall, but is going to measure the…
JPRV
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Why do these SMD switches have keepout zones?

This type of switches comes with keepout zones. This is the default footprint used in Kicad (specifically it's Button_Switch_SMD:SW_SPST_SKQG_WithStem). Why are there keepout zones for this switch?
bask185
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Desolder solder via deep fryer?

I was reading this post and came up with a wonderful, horrible idea. Can electronics survive in cooking oil? Has anybody heard of using hot oil as a medium to transfer for the purpose of soldering/desoldering? It'll be a single uniform temperature…
Emmanuel Lopez
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Identify Mystery SMD component code 470C

I have a BLDC driver board and am having trouble identifying a component. Its PCB label is X3 so I initially assumed it was a fuse of some type. However it is connected in 3 spots. I searched smd code tables etc but can't find it. Looks like 470C is…
bobox
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Pick and place machine + AAA battery holder?

Say I design a two-sided PCB. I want the bottom side to have just a 2xAAA battery holder. Could a pick and place machine handle this or is it out of the question? What happens when the top side is flipped over - wouldn't the board "wobble" depending…
David Högberg
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