SMD Caps

Hello everybody,
How can I realize the capacitance of an SMD Capacitor without pulling it out of it's circuit board? Are they coded with their colors? I htink both color and size are standard.
Thanks a lot in advance.

alisarhangpour said:

Hello everybody,
How can I realize the capacitance of an SMD Capacitor without pulling it out of it's circuit board? Are they coded with their colors? I htink both color and size are standard.
Thanks a lot in advance.

Click to expand...

Physical sizes ARE standard for SMD devices.

Color is NOT standard. Personally, I've seen brown to beige to light grey with known values all over the place. Sometimes you will find a marking that indicates the value but most often, you won't.

they are typically not marked or color coded in any way... your only hope is to use a capacitance meter to read them on the board, however that will be inaccurate as it will take into account the capacitance of all the other components that are connected to it.

The only way you'll be able to get real values is to desolder them and measure them off the board. if you get SMD "tweezers", which are basically like two soldering irons put together with a hinge so they are like a pair of tweezers, it is very easy to remove SMD caps and resistors.

Would these SMT tweezers be useful in reverse? Like are they good for mounting and re-mouting SMT parts, or is it only good at removal

I haven't had any luck using them for installing parts... for one, they aren't exactly up to par with the precision of regular tweezers, so actually holding onto the part well enough to position it would be an exercise in futility... when you are removing parts that doesn't matter, because you just drop the part as soon as it comes off.

also, I don't know about some of the more expensive ones, but mine only has a temp sensor in one of the tips. that means that the two tips don't stay quite the same temp, so one usually melts solder faster than the other. again, that's not a huge problem for removing parts, but makes installing parts difficult.

DigiTan said:

Would these SMT tweezers be useful in reverse? Like are they good for mounting and re-mouting SMT parts, or is it only good at removal

Click to expand...

No, they are no use for that, but it's VERY simple to install SM resistors and capacitors with a simple soldering iron - a pair of small tweezers in your other hand helps, but you can use a small screwdriver to position them as well, then use the end of the screwdriver to clamp the part in position before tacking one end with the soldering iron.

As I've mentioned previously, using liquid flux makes the entire procedure MUCH easier - and looking at evandudes tutorial, he would benefit greatly from using it! - the joints in his pictures are rather 'lumpy' and over soldered (no disrespect, but while they will work fine, it's not a very good job!).

Nigel Goodwin said:

and looking at evandudes tutorial, he would benefit greatly from using it! - the joints in his pictures are rather 'lumpy' and over soldered (no disrespect, but while they will work fine, it's not a very good job!).

Click to expand...

Oh, I know :lol: that board is a prototype, not a final product, so I wasn't too concerned... as you can see, i wasn't very careful, since I soldered the chip on AFTER the other components...

part of the reason I didn't care too much is that when I printed off the toner pattern, a couple pieces of cat hair made their way into the printer and got fused into the toner (I really need to cover my printer when I'm not using it...) so the board came out a little ugly anyway, because I was too lazy to just print off a fresh toner pattern when I realized the first one was messed up :wink:

but hey, as the most important part of any prototype, it worked fine, and building the board from start (bare board) to finish (working board) took me under an hour

I'll get some better pictures when I build a board I actually care about :wink: