6mm Tact Switch Height - do you have a typical preference? - Page 1
Forum section: electronics / projects

author: sleemanj
author_rank: Super Contributor
timestamp: May 11, 2019, 02:42:17 am
content: So, 6x6 tact switches, they come in various heights, from 4.3 up to 20mm, obviously the tall ones are dictated by design usually to show through a panel or whatever, but at the bottom level we have 4.3mm, 4.5mm, 5mm all really close together but with slightly different feel.Are there any opinions here, anybody have an actual preference for say a 4.3mm over a 5mm, or vice-versa?With a 4.3 your fingertip tends to contact the whole surface area of the top of the switch including the 4 posts, while with the 5mm your finger tends only to press the button itself, I can't decide if I prefer the feel of the force being spread out (4.3) or the more direct feel of pressing the button only (5mm)...Maybe I should split the difference at 4.5mm.

author: floobydust
author_rank: Super Contributor
timestamp: May 11, 2019, 05:48:28 am
content: Nobody pushes the raw button, just on muh Arduino shield with no product enclosure.It's kinda ugly, no ESD protection and the post is around 3.5mm dia. which is small. What configuration are you are thinking of?I've seen a front-panel membrane overlay, or a button cap on the stem is most common.With the taller posts, a sideways bump can bust it off the PCB as the SMT pads aren't much.I use Omron pushbuttons with the square post which locks the button to the post, instead of the primitive press-fit.

author: ajb
author_rank: Super Contributor
timestamp: May 11, 2019, 06:21:17 am
content: Quote from: floobydust on May 11, 2019, 05:48:28 amOr, as we've seen on a recent batch of boards with 13mm high switches, the little heat-formed nubbins that retain the metal top plate pop off, then then the plate and stem fall out, followed shortly after by the switch guts. Another item on the intake acceptance listAt least this way the boards aren't damaged, and the switch can simply be replaced.Anyway, as floobydust says, the proper height is whatever it needs to be easy pushed through whatever panel/actuator it sits behind. Our 13mm switches come up just to the bottom of a printed overlay, but for other applications, I would want the actuator to be about 1mm proud of the surrounding surface.

author: sleemanj
author_rank: Super Contributor
timestamp: May 11, 2019, 06:26:32 am
content: Quote from: floobydust on May 11, 2019, 05:48:28 amWhich is the use case, no/minimal enclosure.Fair point on not pressing directly in commercial devices.

author: KL27x
author_rank: Super Contributor
timestamp: May 11, 2019, 08:50:36 pm
content: I have used all of them, and I think 4.3 or 4.5 is probably the most comfy, naked, anyway. And you don't want to go taller (naked) if durability matters.Aside from height, another important factor for durability is the press force. The stiffer the switch, the lower the cycles, and it is quite dramatic.I wouldn't call it a hard rule... you have to check the datasheets.... but IME the lowest force and highest press cycles come in black. White is in the middle. Red is on the stiffer end. Then there are other colors between those.I find if you are not using any enclosure or button cap, that the lowest force feel fine.Using the 5mm's naked AND with the higher stiffness, these buttons can quickly become faulty, internally, with no external damage. Worse than simply quitting, they will start to function, intermittently. Esp on a widget with a lot of buttons on it, this will be a big annoyance.

author: floobydust
author_rank: Super Contributor
timestamp: May 11, 2019, 10:18:08 pm
content: The tall-stem parts must be terrible for reflow, I imagine them falling over?I'm fine with the short stems, like on these Arduino TM1638 shields.I frequently zap ESD hits to the aluminium plate. The 5-pin pushbutton variant with a (ground) ESD shield or ESD diodes it what I use.

author: sleemanj
author_rank: Super Contributor
timestamp: May 11, 2019, 10:45:14 pm
content: Quote from: KL27x on May 11, 2019, 08:50:36 pmInteresting, I had assumed that the only difference would have been in how tall the cap injection mould would be, that the switch mechanism itself would be identical between them (within a given manufacturer/range).

author: KL27x
author_rank: Super Contributor
timestamp: May 12, 2019, 07:49:21 pm
content: QuoteIt might be. Some switches will tolerate being pushed off axis better than others. Some will not last as long without being guided by an enclosure. At 5mm, this is tall enough that your finger is floating on the button without any other support, and it's short enough that lateral movement results in a large degree of tilt. You might find switches that work and last just fine. If you want to avoid potential issues, and it doesn't really matter one way or the other, I suggest you stick with the shorties with low button force.I don't have enough experience that it qualifies as much more than anecdote, but the worst switch life I have experienced is using5mm6mm height 6mm switches of medium force (white) without an enclosure. 2-3 out of 8 switches went bad (unreliable/unstable) after very little use. They worked sorta when you pressed them hard enough. I replaced them all. I am 90% sure these are the same white buttons that are in one of my oldest DIY PSU's, which seems to last fine when in an enclosure with the buttons sticking through a hole in a front panel..

author: floobydust
author_rank: Super Contributor
timestamp: May 12, 2019, 09:31:35 pm
content: Quote from: KL27x on May 11, 2019, 08:50:36 pmI've had problems with pushbutton switch plastics deforming during reflow or even hand soldering.Symptoms are the click goes mushy and soft, the operating force drops way down.No, I'm not melting them outside, but the internal spring cap seems to be made of plastic now or the body changes dimensionally. The pins move a fraction of a mm and it's a different switch.A certain switch manufacturer sent me samples of 260g high operating force parts, and I experienced a 40% failure rate, where they worked but went soft and mushy and the click became pretty quiet.I stay clear of that brown resin plastic, it can't take heat.

author: ajb
author_rank: Super Contributor
timestamp: May 13, 2019, 01:25:11 am
content: Quote from: floobydust on May 11, 2019, 10:18:08 pmOur assembler hasn't complained, and we had no problems building the prototypes in house. I think our CM may also wind up reflowing them twice, since the other side of the board has heavier components on it so I would guess that they do the button side first, but I've never asked.Quote from: floobydust on May 12, 2019, 09:31:35 pmWe've had hundreds of the tall stem switches reflowed in a lead-free process (possibly twice as mentioned above), and nothing like that. The spring discs are metal, though. I did see two switches fail, and those had clearly been improperly reworked, with some heat distortion to the plastic bodies and discolored spring discs. The switches are either Wurth or Apem depending on what's available when we order.

author: Tek Tech
author_rank: Contributor
timestamp: May 13, 2019, 05:01:29 am
content: Off-axis tilt is the killer. So, the shorter the push rod - the better reliability and longer life.Notice that almost all commercial products (TVs etc) have minimal hight tactile switches being pressed indirectly by some sort of guided pushbuttons.For home projects I get switches with the longest buttons (20-25 mm), stick them thru a hole in the enclosure to prevent tilt, and trim to size.