From SMD tactile switch to 4 pin connector - Page 1
Forum section: electronics / projects

author: georgeflr
author_rank: Newbie
timestamp: May 05, 2023, 12:08:42 pm
content: Hello,I have a LCD Board for a Raspberry Pi and it has a few pushbuttons on the side. They are SMD tactile switches.I want to move them into a separate location, either a PCB Board or a mounting place.My question is that if I cand find compatible connectors, that can pe soldered on the old pushbuttons pads and not leaving soldered wires directly on the old pads. This way I can connect the buttons and disconnect them as I please.Thank you.

author: barshatriplee
author_rank: Regular Contributor
timestamp: May 05, 2023, 12:57:48 pm
content: The solution will depend on the configuration of the board. A picture may help you get more fruitful responses.

author: thm_w
author_rank: Super Contributor
timestamp: May 05, 2023, 11:21:47 pm
content: 0.1" headers will work if you bend them a tiny bit, JST XH, etc. just look around in your component box to see what you have that would fit. Solder the legs and put some glue around it.Or solder wires and have the connector on the other side where you are making a PCB.

author: Nominal Animal
author_rank: Super Contributor
timestamp: May 06, 2023, 08:55:35 am
content: Me hobbyist! Me know nothing. But..For many of the common 6mm×6mm tactile switches, standard male SMD 2×3 pin headers can be easily soldered to the same footprint, with the two center pins unused (I'd remove them altogether).See e.g. LCSCC780054orC178294, MouserAmphenol 10129383-906001ALF.Of course, you only need to connect two pins (either diagonally, or next to each other, assuming typical 6x6mm 4-pad SMD tactile switches) per switch. I like to use all four pads, since it makes the pins stay put a bit better – although a dab of e.g. UV-curing glue wouldn't hurt. You can easily check this with a multimeter.Amphenol EconoStikseries of unshrouded 2.54mm header pins has an SMD version with every other SMD "leg" in the other direction; for exampleAmphenol 10129380-902001ALF(Mouser). This can be cut/snapped just like normal male pin headers. Three consecutive pins, with the middle pin unused (or removed), should fit the close pair of 4-pin 6x6mm tactile button pads. This can help, if you don't want extra pins sticking out, or feel the 2×3 take too much room; but then I'd definitely use some UV-curing glue to glue the plastic shroud to the board, so I won't accidentally rip out the pads when pulling the female standard header (1x3-pin female, middle pin unused, 2.54mm pitch) out.In either case (2x3 or 1x3 pin headers, with middle pins removed or unused), the female side is a standard 1x3 female 2.54mm terminals, also with the middle pin unused. Of course, you can also use wires with single female terminals, like female jumper wires, in pairs.I would use standard HarwinM20-1060300 3-pin 2.54mm pitchfemale terminal housings from Mouser (the image is from a 5-pin housing, but the product is the 3-pin one), with compatiblecontacts(for AWG 30 to 22 wire). The wire is just crimped to the contacts (using crimping pliers). The typical crimpers for these have a ω (or rounded W) -shaped anvil (female side), with the center bit pushing the open side of the contacts into the wire, while stopping the rectangular-U cross-section contacts from widening out.With a good crimper (no need to splurge too much; the cheap JX-1601 ones are quite okay for hobbyists like me), and a kit of Harwin (or "Dupont") male and female wire headers, you can make any other similar cables to whatever length you want._ _ _If there are many buttons, you can also check which pin is the common one among all buttons, thus only needing 1+Nwires forNtactile buttons. You can pick a suitable connector, glue it to your LCD board in a suitable place, and run wires to the button pads from the connector.Just make sure the connector is glued so that ripping out the connector won't rip out an entire layer off the PCB.There is minimal current running in these wires, so you can use very thin flexible wires. I like to use ribbon cables (which you can split to a suitable width from a wider cable), so I personally would prefer having a single ribbon cable between the LCD board and the buttons. Single wires tend to get snagged or pinched.

author: ajb
author_rank: Super Contributor
timestamp: May 06, 2023, 03:58:52 pm
content: Rather than shoehorning a connector into the button footprints, you could mount a connector of your choice somewhere on the board and run bodge wires to the button pads. You can mount the connector with glue only, but if there’s a ground plane you can scrape some soldermask from and solder a few pins to, and then reinforce with glue, that would be better.Or if you want to overdo it, you could design a small PCB that solders to the board in place of the buttons and provides a single connector. You could use through holes for the switch pads, but castellated holes would be easier to solder. Or since there are services that do flex PCBs relatively cheap now, you could do a flex PCB with smt pads on the bottom and solder them down like a hot bar connection. That would be the most versatile option, as you could design it to jump over or wrap around the board and other obstructions, or even design it with an integrated FPC tail to serve as your cable to the new buttons