How to design a board with overlapping components in Kicad?

Just out of curiosity. I saw a board where a designer cleverly put some SMD components under a THT IC on a socket, see the first photo in the gallery here:

How would that be done in Kicad? Remove some courtyards so the DRC doesn’t complain?

Pretty mutch so, unless you just ignore courtyards, which is not a good idea to begin with.

0402 fit nicely under ordinary DIPs even without a socket.

Or replace dip socket with two inline female headers.

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If space is at such a premium why use tht components at all? Placing components under such a package just makes it harder to debug or fix problems. My suggestion would be to choose a much smaller smd package for the IC and reduce the required space that way.

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But then you have to redo the pin assignments for the IC. :face_with_raised_eyebrow:

I’m the customer here, I get to choose what components I want to use. Perhaps it’s a design that uses an IC that is not available in SMD. Or perhaps the component above is a daughter board that is plugged in later. Whatever the reason, I just want to know how it can be done in Kicad, problems and all. Yours not to reason why. Anyway it was an idle question, I don’t have such a design in mind, just wondering how it would fit in Kicad’s workflow.

That might have been the case in 1990? The market is the other way round nowadays. It is far more likely to get smd components than tht because automated pcb manufacturing is much cheaper with them. I have yet to find a single component (marked active by the manufacturer) that does not at least offer SOIC as an alternative to DIP.

You are right on of course.

Though, it’s mostly for the fun of it to be able to do things like that these days. Could be used to ‘hide’ something, or at least make reversing harder.

Then again, just yesterday I stumbled across this lot Mikatech

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I have some components from the 70s. :wink: But I would probably not mix THT and SMT this way; I would use a larger board. I was just curious how it would be done if that designer were to use Kicad today. I design for fun; I don’t have to earn a living with it.

I just remembered a nixie clock design that might have needed this hack. The designer had put a blue LED under the tube socket. Very nice effect.

Turn courtyard check off in the board settings.

Some amateurs prefer to use ICs in DIP, but at the same time has nothing against using R and C in SMD. To place a blocking capacitor with as short as possible connection between VCC and GND when they are at opposite IC ends the best can be to put it under IC.

That makes no sense at all a 0603 (or 0402 package like suggested by @bobc) is harder to solder than a SOIC with 1.27mm pitch.

You are right, but …
What if you are amateur and in your design ICs like to be burnt and from your experience you know that you often have to replace them. Some amateurs prefer to have all ICS in sockets just because of it, but they rather don’t need to replace R and C.
About 15 years ago we got to redesign the Time and attendance control device which were offered by one firm in GB. We got it because it “frequently gets overheating and stops to work”. There were Touch-button used and central pin of its socket was directly connected to microcontroller pin with absolutelly no protection. So the problem was not overheating but latch-up and then getting as much current as 7805 allows so it was warmed till its thermal protection. And they noticed the box is hot.

When we started our firm (1988) then our first devices were all THT. But an year or two later we used to use ICs THT and resistors and capacitor SMD (1206) till few years later we moved to all SMD. With THT IC we were able to cut it from PCB (and then remove each pin one by one). We had no so precision cutters to do it with SOIC. Our device was EPROM programmer so had many pins user can touch and ESD can reach our ICs.

An SOIC (or any gullwing) package is quite easy to exchange. Use a sharp knife to cut the leads near the package. (Take care not to damage the pcb or yourself. Wear your protective equipment. At least safety glases would be a good idea.) You don’t even need precision tools here. Just hold your knife at an angle such that you cut into the package instead of the PCB and you should be good to go.

Take a solder iron and remove the legs one by one. Clean the pads with solder wick. Solder the new part onto the pcb as usual. (Takes a few minutes at most. Especially for large pitch parts like SOICs that are offered as a typical alternatives to DIP.)

In the end it is nearly the same workflow as you explained for DIP with the cleaning of the solder pads being much easier. (THT pads are sometimes quite hard to get completely free of solder on the inside. Especially if the pad is connected directly to a large inner plane.)

Or invest into a good hot air “gun” with rework nozzles for SOIC. (Something like with

Such a setup really is overkill for SOIC but becomes essential for QFN or BGA rework.

Hint: check the fablab, hackerspace or any similar organization near you as they might have such a tool.

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Nowadays everything is simple as you can buy whatever you need.
I was writing about times when we (Poland) just went out of socialism (the system in which you bravely fight with problems don’t even known in other systems). The only soldering irons we had in firm were 25W/220V without temperature regulation and with tip made of 4mm diameter copper rod. From time to time you used file to repair its shape as copper is ‘eaten’ by soldering. Soldering stations were don’t known for us or out of reach.

So my arguments don’t fit to nowadays amateurs but from my watching the usenet group pl.misc.elektronika I remember from time to time someone that from his posts you see he prefers DIP.

It’s a shame that a “How do I do this?” question has generated so many “You don’t want to do this!” replies. That’s not the question being asked.

There are valid reasons for nesting footprints. One is to allow different parts to be fitted to a board during assembly. This can be especially important for hobby kits where certain components may be hard to find. For example, some SPI Flash ROM chips often are out of stock for long periods. There are suitable alternates, but they have different footprints.

So… if you’re going to attack someone instead of answering the question, just don’t comment.


As I don’t work with soldering frequently, and our production is 230km avay from me I don’t have here any modern equipment. There are no many holes in our PCBs (as we use SMD), but when I have to remove solder from hole I use the surgeon steel hook-needle (I don’t know how to name it better) we have since always. I push it from backside hitting with soldering iron (110W trafo iron) from front.
THT metalised pads are much much more robust to be destroyed during not professional desoldering.

I put at PCB the ferrite plate footprint (no pads) and on that footprint I put the RFID antenna footprint.
I put the FFC flat cable footprint (no pads - to show where it is) and on it the ferrite to be put on that cable.
But in my program DRC don’t looks at courtyards. I have read that V5 looks at it but it can be swithced off - I was not at the stage of DRC in V5 yet.

I actually had to do this recently, there were no other practical options. Client had a tiny (16 x 16mm) PCB that was originally designed to carry only an electromechanical sensor and a connector. Sourcing issues necessitated a change of sensor, which in turn necessitated the addition of a couple of ICs and a handful of passives. No changes to the footprint of the PCB were permissible. Thankfully, the sensor mounting pins are such that they leave .050" under the body of the part, and I was able to put a number of components under it, including one of the ICs. It simply would not have been possible otherwise.