Silicone Rubber Keypads 1

[kjoiner]

Hello,

I saw a previous post regarding the use of silicone rubber keypads and have considered them in the past for products we produce but after having some troubles with remote controls, I have a few question:

Like a lot of people, I have too many remote controls. Of those I have, over time, the keys become non responsive. I have one remote with a volume control that no longer works, and another remote where several buttons no longer work. A while back, I purchased one of the fancy Sony remotes with an LCD touchscreen, but for volume, channel, and menu functions, it has silicone keys and they started giving me trouble. I have taken remotes apart and cleaned them and have noticed a recurring issue. Last night, I became fed up with the non-working keys on the Sony remote and opened it up. Underneath the volume and channel keys, I noticed an oily substance on the silicone, and also on the PCB. Interestingly, the buildup was underneath the most frequently used keys. I got some alcohol and swabs and cleaned both the keys and the traces on the PCB. They now work again. I have another remote with a similar problem and symptom, but cleaning did not fix the volume.

Since remotes are hand held, could the warmth of a hand cause condensation inside the remote? One obvuious culprit of moisture could be spilling someting on the remote but I'm very careful to keep liquids away from the touchscreen remote. Again, the buildup is right around the most frequently used keys.

Also, I have had failure of silicone keypads in cordless telephones.

Could there be a mold release agent leaving the silicone or could there be some silicone leaching out of the keypad?

It's a strange problem. Any ideas?

Thanks,

Kyle

 

[itsmoked]

Not sure what that substance is...
I have the same problem with slowly failing remote buttons. Of course this is because they all use the totally abhorrent, cheap graphite, garbage, buttons.

Vinyl products often bleed. Are you sure that the keypads aren't really vinyl since silicon is umm... not-cheap?

 

[kjoiner]

itsmoked,

It could be some other type of material besides silicone. It's whatever is prevalent in most remote controls these days. I'm assuming it's silicone based on the rubbery feel of it and from what I've seen when investigating keypads for industrial products but in the end, I'm not really sure.

I'm going to open up the other remote I have and see if there is any liquid between the keypad and PCB. This control is in the bedroom and has never had the chance to be exposed to drinks. If I find liquid in this one, I'll really be suspicious of the materials.

Kyle

 

[IRstuff]

It has a lot to do with how the actual contactor surfaces are constructed. The PC keyboards that I've dismantled also use "silicone" (note the "e" at the end ;-) ), but the contactors are separated from silcone by a plastic membrane. Only if you get seriously liquid contamination down into the keyboard will the contactors get fubarred.

TTFN

 

[kjoiner]

IRstuff & Itsmoked,

I just found this site related to remote control repair:

http://an.hitchcock.org/repairfaq/sam/irrfaq.htm

Scroll down about 1/3 of the way and look for a heading called "dirt, spills, gunk and oily buildup inside"

It seems there is a problem with this oily material coming from the keypad and it's characteristics are described almost exactly as I've seen them. Apparently, it's somewhat tough to remove and then comes back from time to time and no one is exactly where it comes from. There are several comments about the silicone rubber keys and how to clean them with varied success. There is also a link to a site that lists more characteristics of silicone, but unfortunately it doesn't work.

Kyle

 

[kjoiner]

Hello,

Here is another quote from a discussion group relating to troublesome keypads. An article regarding silicone rubber keypads mentions oil in the silicone and it's tendancy to "excrete" out from the keypad. I did not see the author's name mentioned by the other person, but if I do find it I will definitely provide credit because the author probably has the best information so far. Here is the quote:


The silcone rubber in keypads is so soft because it is a matrix -
like a sponge with many microscopic chambers. When this material
is created, the chambers are filled with silicone oil. (In fact,
this may be how they make the chambers to being with.) The
manufacturer then has to "bake" the oil out so that the chambers
are empty (filled with gases). However, getting the oil out
takes time and adds cost to the manufacturing process. So,
many companies skimp here and do not do a good job baking
out the oil. Note that, like a sponge, heat AND/OR pressure
can squeeze the oil out - it only takes ONE of the two.

So, after many years of pressing on silicone keys, a nontrivial
amount of oil can become squeezed out - and this oil, unlike
regular oil, will interfer with the keypad contacts. Of course,
by this point, the user will not blame the company for this
problem, but himself - "Somebody must have spilled something
on it." You can tell it is silicone oil because it resists
detergents much more than normal oil, so cleanup takes a
little scrubbing (with a toothbrush and strong detergent like
409) - not just a simple spray and rinse.

end quote


This kind of reminds me of the plasticizers used in plastic fishing worms - put them in a tackle box made from the wrong kind of plastic and they will eat a worm shaped recess into the plastic.

Kyle

 

[kenvlach]

Re "oily material coming from the keypad."

It's the plasticizer, an oil that gets between the polymer molecules to make the plastic more supple. E.g., makes vinyl flexible instead of rigid PVC. Also gives the 'new car smell.'

Maybe ask "Plasticizer used in flexible keypads?" in the
Polymer engineering Forum
forum334

 

[itsmoked]

Wow kjoiner! Nice find. Most interesting and informative.

Thanks too kenvlach.

So what is the stuff that comes out of vinyl binders when you stick a label on them and a month later they fall off and leave a big slimy sticky mess that cannot be remedied,
plasticizer?

 

[kenvlach]

Thousands of different plasticisers are used.
Pretty irritating when you print a nice cover for a clear-covered binder & have the ink get lifted off by the vinyl film. This seems to happen more with the cheapo rather than name brand binders, so must depend upon the cost & choice of plasticiser.

There is also a big health controversy over the long-term effects of phthalates, a common class of plasticizers. Now found everywhere: Arctic seals, mothers' milk, etc. Greenpeace wants them banned.

"In Western Europe about one million tonnes of phthalates are produced each year, of which approximately 900,000 tonnes are used to plasticise PVC (polyvinyl chloride). The most common are: di-2-ethyl hexyl phthalate (DEHP, sometimes also referred to as DOP), diisodecyl phthalate (DIDP) and diisononyl phthalate (DINP)."

From Plasticisers

http://www.ecpi.org/index.asp?page=5

 

[kjoiner]

Quote:

Also gives the 'new car smell.'

End quote:


I read an article recently where they're trying to eliminate the new car smell because it might be a health hazard. Where does it end? It's better than the old car smell

Kyle

 

[zeitghost]

You know that misty stuff that you find on the inside of the windscreen at the end of the summer?

That's the plasticiser that's come out of the plastics while the car is hot in the sun... (not too much of a problem in the UK since the sun very rarely shines...).

 

[itsmoked]

That windshield stuff is nasty to try to clean off.. I hate it! I only see it after hot days.. I figured the seats and the dash were the cause. I have also suspected it is b a d for people and have since trained all my family to air out hot cars before entering them.

 

[kjoiner]

If you treat your dashboard with protectants such as Armor All, it will tend to do the same thing. It's kind of a catch 22 - don't treat your dash and the sun will eventuall kill it or treat it and deal with the film.

While I'm on the subject, I've noticed over the years that with the lower rake windshields in cars today, if you use some of the glossy protectants, you can get a nasty suprise at night or other inopportune times when you suddenly find yourself looking at a reflection of your dash in the windshield that blocks your view. Kind of like an uplanned heads up display.

 

[kenvlach]

Yep, the stuff that comes out of baked vinyl is a heavy, oily type of phthalate. Cleans off glass pretty easy with ammonia (in water).

Agree with itsmoked about airing out cars that have been sitting in sunlight -- It's pretty difficult to clean your lungs out with ammonia!

 

[analogkid2digitalman]

I live in Phoenix were when it is 112F out in the day, it can reach 170+F inside the car. I finally bought my first new car 5 years ago, along with it came the new car smell and the fogged up winshield. It still fogs up, stock windex with a good dose of ammonia and vinegar cuts through it pretty well.

Never had remote keys go on the blink though.

Wheels within wheels / In a spiral array
A pattern so grand / And complex
Time after time / We lose sight of the way
Our causes can't see / Their effects.

 

[itsmoked]

I had a Renault R10 with after market reupholstered seats in it. On hot days it actually had a fog in it.... That was when I formulated the don't breath that garbage philosophy. I took razor blade scrapings off the windshield to my college organic chemistry lab for a fellow student to analyse. Don't know what the result was. Must have been the 17 units I was carrying.