Kailh hot swap socket commonly found problems

[Rico]

Hi all,

I recently designed a PCB using Kailh hotswap sockets for my personal hobby project.

But after having read various problems using them in this forum I'd like to know from you guys the experience you had using them, both from a user and PCB creator perspective.
These feedbacks may be useful in the future to potentially solve commonly found problems by doing new footprint designs, or at least to understand the limitations of using these hotswap sockets.

The problems I heard the most seem due to the force applied when inserting a switch:
- Kailh socket could pop out of the PCB due to bad or too light soldering.
- Kailh socket PCB copper pad could detach itself from the PCB FR4 plate.

Any of you experienced these kind of problems?
Do they happen often?
Is there other problems that I forgot to describe in this thread?

 Thanks in advance for your help

[ILWrites]

Hi there, Riko.

I'm also new to Kalih HotSwap sockets, but I've designed PiKeeb with the hot swap in mind (here is the link to the thread: https://geekhack.org/index.php?topic=99682.0)

If my understanding is correct, you need a plate or 5-pin switches to mitigate those problems.
Plus, consider using PCB no less than 1.6mm in thickness.

Also, those issues are fixable with a little bit of solder, unless you go crazy on them and break the pads by lifting them from PCB.

[Rico]

Hi ILWrites,

Very nice PCB that you did!

I already did as you mentioned: key switches are plate mounted and the PCB is 1.6mm thick.

Jut to mention that I already have soldered a PCB with QMK firmware that if working just fine
Also just like you I used JLCPCB service that did a wonderful job at a cheap price

My biggest concern is the pad lifting problem that would ruin the PCB, just having to resolder the Kailh socket is not a big issue.
To my taste having to apply a significant force on small pads that are just glued to the PCB substrate is not the best thing to do.
I don't know how often it happened to people, but saw some guidances by PCB manufacturers to maintain a finger on the socket while insterting a switch :S

If pad lifting is really a problem then I would make another PCB revision with new Kailh socket footprints that would be less prone to that kind of problem.

Thanks for you feedback,


 

[ILWrites]

My biggest concern is the pad lifting problem that would ruin the PCB, just having to resolder the Kailh socket is not a big issue.
To my taste having to apply a significant force on small pads that are just glued to the PCB substrate is not the best thing to do.
I don't know how often it happened to people, but saw some guidances by PCB manufacturers to maintain a finger on the socket while insterting a switch :S

If pad lifting is really a problem then I would make another PCB revision with new Kailh socket footprints that would be less prone to that kind of problem.

Thanks for you feedback,

If you are feeling too anxious about it, you can put just a dab of hot glue between the PCB and those sockets. Just make sure that glue does not touch the metal contacts on those sockets or the pads. That way you'd spread the applied force and therefore reduce risk of it braking and lifting the pads. And if you are using hot air to solder/desolder those sockets, hot glue is the way to go as it would melt when the heat is applied, thus giving you time to remove sockets, if any of them goes bad.

[Rico]

Thanks to the good advice, hot glue seems the way to go for an individual soldering it's PCB at home.

It is just too bad that Kailh didn't thought about this potential mecanical problem, I do love there hotswap approach otherwise.

My PCB does not suffer this problem as of now and I played quite a bit inserting and removing switches already.
I may be paranoiac, or lucky
That being said as I soldered them by hand using a soldering iron (and not my heat gun) I put quite a bit of solder on them, at least much more than doing it by reflow soldering.

I did a few tries with reflow soldering and lead free solder paste and saw that to melt the solder I had melted the socket plastic casing a little bit also.
This plastic does not seem to tolerate high temperatures (260-270°C range), maybe ABS?
Maybe PCB manufacturers have to rely on low melting point solder paste in order not to damage the socket.
These are kown to be much more brittle than standard ones, that could explain why sometimes the socket pops out.