Forums

Looking for a switch

Started by Jim Stewart October 27, 2012
Does anyone know of a pushbutton switch
that can be surface mounted to the back
side of a PCB with the actuator button
protruding through a hole in the PCB?
On 27.10.2012 20:33, Jim Stewart wrote:
> Does anyone know of a pushbutton switch > that can be surface mounted to the back > side of a PCB with the actuator button > protruding through a hole in the PCB?
I would hope that such devices do not exist, because they would be doomed to fail mechanically. SMD means you have only the solder joints to keep your part in place. For the setup you're looking at that would mean every push of the button exerts exactly the kind of force solder joints to PCB pads really can't stand: shear-pull away from the board. That mechanical setup practically begs for the pad and a piece of track to be torn loose off the base material, leaving your whole button dangling in the wind. SMD push buttons exist, but there's a reason they always go on the front, where the push force can be passed via the back of the switch housing directly to the PCB, without stressing the solder joints.
On 28 Okt., 11:28, Hans-Bernhard Br&#2013266166;ker <HBBroe...@t-online.de> wrote:
> On 27.10.2012 20:33, Jim Stewart wrote: > > > Does anyone know of a pushbutton switch > > that can be surface mounted to the back > > side of a PCB with the actuator button > > protruding through a hole in the PCB? > > I would hope that such devices do not exist, because they would be > doomed to fail mechanically. > > SMD means you have only the solder joints to keep your part in place. > For the setup you're looking at that would mean every push of the button > exerts exactly the kind of force solder joints to PCB pads really can't > stand: shear-pull away from the board. &#2013266080;That mechanical setup > practically begs for the pad and a piece of track to be torn loose off > the base material, leaving your whole button dangling in the wind. > > SMD push buttons exist, but there's a reason they always go on the > front, where the push force can be passed via the back of the switch > housing directly to the PCB, without stressing the solder joints.
yep reverse mount smd wouldn't work unless they were glued down or something you can get reverse mount: http://www.e-switch.com/product/tabid/96/productid/9/sename/tl1107-series-tact-switches/default.aspx but it is through hole and you'll need a milled hole for the switch -Lasse
On 10/28/2012 7:50 AM, langwadt@fonz.dk wrote:
> On 28 Okt., 11:28, Hans-Bernhard Br&#2013266166;ker<HBBroe...@t-online.de> wrote: >> On 27.10.2012 20:33, Jim Stewart wrote: >> >>> Does anyone know of a pushbutton switch >>> that can be surface mounted to the back >>> side of a PCB with the actuator button >>> protruding through a hole in the PCB? >> >> I would hope that such devices do not exist, because they would be >> doomed to fail mechanically. >> >> SMD means you have only the solder joints to keep your part in place. >> For the setup you're looking at that would mean every push of the button >> exerts exactly the kind of force solder joints to PCB pads really can't >> stand: shear-pull away from the board. That mechanical setup >> practically begs for the pad and a piece of track to be torn loose off >> the base material, leaving your whole button dangling in the wind. >> >> SMD push buttons exist, but there's a reason they always go on the >> front, where the push force can be passed via the back of the switch >> housing directly to the PCB, without stressing the solder joints. > > yep reverse mount smd wouldn't work unless they were glued down or > something > > you can get reverse mount: > http://www.e-switch.com/product/tabid/96/productid/9/sename/tl1107-series-tact-switches/default.aspx > but it is through hole and you'll need a milled hole for the switch > > -Lasse
I have seen transformers mounted with part of the unit protruding through the board, but still soldered on the top side. Maybe a switch like this exists, it recesses into the board from the top, not stressing the solder joints but is very low profile on the top side. Rick
In article <k6k1eg$sbb$1@dont-email.me>, gnuarm@gmail.com says...
> On 10/28/2012 7:50 AM, langwadt@fonz.dk wrote: > > On 28 Okt., 11:28, Hans-Bernhard Br&#2013266166;ker<HBBroe...@t-online.de> wrote: > >> On 27.10.2012 20:33, Jim Stewart wrote: > >> > >>> Does anyone know of a pushbutton switch > >>> that can be surface mounted to the back > >>> side of a PCB with the actuator button > >>> protruding through a hole in the PCB? > >> > >> I would hope that such devices do not exist, because they would be > >> doomed to fail mechanically. > >> > >> SMD means you have only the solder joints to keep your part in place. > >> For the setup you're looking at that would mean every push of the button > >> exerts exactly the kind of force solder joints to PCB pads really can't > >> stand: shear-pull away from the board. That mechanical setup > >> practically begs for the pad and a piece of track to be torn loose off > >> the base material, leaving your whole button dangling in the wind. > >> > >> SMD push buttons exist, but there's a reason they always go on the > >> front, where the push force can be passed via the back of the switch > >> housing directly to the PCB, without stressing the solder joints. > > > > yep reverse mount smd wouldn't work unless they were glued down or > > something > > > > you can get reverse mount: > > http://www.e-switch.com/product/tabid/96/productid/9/sename/tl1107-series-tact-switches/default.aspx > > but it is through hole and you'll need a milled hole for the switch > > > > -Lasse > > I have seen transformers mounted with part of the unit protruding > through the board, but still soldered on the top side. Maybe a switch > like this exists, it recesses into the board from the top, not stressing > the solder joints but is very low profile on the top side.
Personally if the switch is so close to the outside, that you need to save height, I would be looking at touch sensors anyway, just areas of PCB track. -- Paul Carpenter | paul@pcserviceselectronics.co.uk <http://www.pcserviceselectronics.co.uk/> PC Services <http://www.pcserviceselectronics.co.uk/fonts/> Timing Diagram Font <http://www.gnuh8.org.uk/> GNU H8 - compiler & Renesas H8/H8S/H8 Tiny <http://www.badweb.org.uk/> For those web sites you hate
On 28.10.2012 21:34, Paul wrote:

> Personally if the switch is so close to the outside, that you need to > save height, I would be looking at touch sensors anyway, just areas of > PCB track.
But those come with their own can of worms attached that's bigger and heavier than an entire PC keyboard's worth of conventional push buttons. SMD push buttons are routinely below 4 mm in height, and can be had down to 1.2 mm. Rubber-mat-with-conductor-pads type buttons are of similar height. If you can fit neither of those, then your PCB is entirely too close to the front panel ;-P
On 10/28/2012 5:53 PM, Hans-Bernhard Br&#2013266166;ker wrote:
> On 28.10.2012 21:34, Paul wrote: > >> Personally if the switch is so close to the outside, that you need to >> save height, I would be looking at touch sensors anyway, just areas of >> PCB track. > > But those come with their own can of worms attached that's bigger and > heavier than an entire PC keyboard's worth of conventional push buttons. > > SMD push buttons are routinely below 4 mm in height, and can be had down > to 1.2 mm. Rubber-mat-with-conductor-pads type buttons are of similar > height. If you can fit neither of those, then your PCB is entirely too > close to the front panel ;-P >
You could use the Forth methodology. If the problem is too hard to solve, solve a different problem. Rick
On 28 Okt., 22:53, Hans-Bernhard Br&#2013266166;ker <HBBroe...@t-online.de> wrote:
> On 28.10.2012 21:34, Paul wrote: > > > Personally if the switch is so close to the outside, that you need to > > save height, I would be looking at touch sensors anyway, just areas of > > PCB track. > > But those come with their own can of worms attached that's bigger and > heavier than an entire PC keyboard's worth of conventional push buttons. > > SMD push buttons are routinely below 4 mm in height, and can be had down > to 1.2 mm. &#2013266080;Rubber-mat-with-conductor-pads type buttons are of similar > height. &#2013266080;If you can fit neither of those, then your PCB is entirely too > close to the front panel ;-P
my immediate guess is that he wants to use the pcb as the front panel All components on the back side, button actuators protruding through holes in the PCB, add some reverse mount leds silkscreen what ever text needed -Lasse
On Saturday, October 27, 2012 1:33:36 PM UTC-5, Jim Stewart wrote:
> Does anyone know of a pushbutton switch > > that can be surface mounted to the back > > side of a PCB with the actuator button > > protruding through a hole in the PCB?
I saw a patent for a tact switch like this, but it was not listed as being assigned to anyone. You didn't mention if you needed push-push or momentary. For momentary, how about a snap dome, they are pretty low profile. I've used a few from snaptron on prototypes and I think Omron also makes them.
langwadt@fonz.dk wrote:
> On 28 Okt., 22:53, Hans-Bernhard Br&#2013266166;ker<HBBroe...@t-online.de> wrote: >> On 28.10.2012 21:34, Paul wrote: >> >>> Personally if the switch is so close to the outside, that you need to >>> save height, I would be looking at touch sensors anyway, just areas of >>> PCB track. >> >> But those come with their own can of worms attached that's bigger and >> heavier than an entire PC keyboard's worth of conventional push buttons. >> >> SMD push buttons are routinely below 4 mm in height, and can be had down >> to 1.2 mm. Rubber-mat-with-conductor-pads type buttons are of similar >> height. If you can fit neither of those, then your PCB is entirely too >> close to the front panel ;-P > > my immediate guess is that he wants to use the pcb as the front panel > > All components on the back side, button actuators protruding through > holes in the PCB, add some reverse mount leds silkscreen what ever > text > needed
Close. Using the PCB as an end panel for an extruded enclosure. Small LCD mounted on the inside pointing out through a hole. Switches mounted on the backside poking through holes, laser cut Mylar overlay on the front. Hans concern about the switch lead fragility is something I haven't thought about and needs to be considered.