XYMer's Home away from Home

Did you know that if you count the key scissors and key caps separately, there are no less than ten individual layers of parts inside a MacBook Pro keyboard? It's true!

I didn't know that until I spilled about 1/3 of a cup of coffee in to mine.

The keys on the far right hand side of the keyboard stopped worked as the electrical traces on the plastic sheets inside the keyboard became soaked. After painstakingly disassembling the entire keyboard, all ten layers, everything that can be removed without cutting, and then cleaning the mess with 70% isopropyl alcohol, I found that the exposed pads had corroded and were no longer conductive.

Most of the traces are safe from moisture beneath a waterproof slip, but they have to be exposed under each key so that when the key is pressed the pads will create a circuit. The pads appear to be a metallic paint, maybe nickel flake in a binder, and are very susceptible to losing conductivity when exposed to moisture.

I tested many different pairs of pads with a multimeter to see which retained their conductivity. In general, any pads that were black rather than silver, no longer fully conducted.

A new MacBook Pro keyboard from a reputable dealer costs about $90 shipped. I didn't have time to wait, so I bought $17 worth of automobile rear window defroster repair kit, and applied very tiny amounts of the metallic paint to the faulty traces. This paint dries in just a couple minutes. I then tested again with a multimeter and the nonconductive pads and traces were working again.

The trick with this is that laptop keyboards are very thin; the conductive pads inside the keyboards are very, very thin -- they have almost no profile at all. The pads are printed on a very thin layer of plastic with two halves as mirror images of one another, both in the shape of the keyboard, such that when one half is folded over the other the pads line up and the plastic represents the key layout. Between these mirror-image layers is another very thin layer of plastic that serves to separate the halves so the conductive pads touch only when you press a key.

If you try to repair a keyboard this way it's critical that the conductive paint you apply is also very, very, thin. If it's not, where "not" is thicker than sheet of tissue paper, then the paint will have too much profile and make unwanted contact with the pad above, causing a key to get stuck "down" and you won't be able to type anything other than backslashes, or whatever. \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\

To avoid this pitfall, after applying an already very thin layer of paint and letting it dry, I scraped and rubbed down the surface of the pad wit the metal tip of a mechanical pencil. After doing so I verified it was still conductive (that I hadn't scraped off too much) with a multimeter.

Sure enough, when I reassembled everything, it worked. And it only took seven hours! Although in fairness it probably wouldn't have taken longer than four if I had decided that was what I needed to do immediately after the accident and already had the conductive paint.

- Anonymous

Nice rescue! Didn't even know that existed. If I'd known, I could have fixed the rear defroster in my Corolla years ago. Good to know about it in case I scratch out any of the lines in my rear window defroster now. Is there enough so you can paint a thin line around your entire apartment to use as a radio antenna? Must be other creative uses.

I wonder if sanding the bad pads a bit to remove the corrosion would have done the job. The trick would have been to remove just enough to get it work without sanding through the layer.

Eric

It doesn't appear that it would. They're so incredibly thin, thin like paper vellum, and may have very high surface area (if they really are just conductive ink made from metal particles in a meager binder) that when they get wet the entire pad corrodes all the way through. I scratched at them with the multimeter leads and it didn't help get a connection. It also ended up scraping away most of one of the pads. If they were sheets of foil that might work, and the pads would be more resistant to water in the first place.

- Anonymous

Thats great stuff. I used to use that and also conductive paint (from any electronics shop) to mod xboxs years ago.

I wanted a tube of the conductive paint, but I couldn't find anyone in town stocking it. I went to one place and they said, "oh yeah, that's stuff's great, every time we order some it sells out immediately." To which I wanted to respond, "then why don't you keep ordering it?" But I didn't.

- Anonymous

In a box somewhere I have a conductive pen that I used once on a Mac CPU, back when they used resistors to bridge pads for the purposes of determining the clock multiplier. I suspect that would work fine, though I have no idea where I bought it... or even which box it's in. As I recall it's kind of a conductive marker more a pen, really.

Yeah, that's what I was after. I had one about a hundred years ago, but it dried up and became useless about 99.75 years ago and I no longer have it. They are sold online, but I wasn't in the mood to wait.

If I had an electronics store, well first of all I'd be bankrupt, but I'd also stock those pens since they're so darned useful, at least before they dry up.

- Anonymous

Cool fix Anon, not having seen what the traces look like my first thought
would have been using a carbon based paint, the contact pads on TV remotes
are carbon I believe and I had used a carbon base conductive paint when
I dabbled in electroforming. They make a product called ELECTRODAGTM PR-800TM
used in - "Cross-overs, key pad, copper contact protection on PCB. "

Acheson Colloids

Note: Acheson Colloids seemed to have swallowed up by a larger company Henkel

I wasn't in a good mood while performing the repair, or I would have taken pictures. I'll try to take apart another old, dead, keyboard sometimes soon and post some pics. My guess is most keyboards use the same key actuation tech, since I've seen very, very, similar designs inside every keyboard I've disassembled -- excluding the nice, old, mechanical key switch varieties like the Apple Keyboard II.

I was first going to use a conductive glue I have that uses carbon for its conductive material, but in pre-application testing it was too thick, or if I worked very hard to make it thin enough it was insufficiently conductive.

The defroster repair paint is both very thin and highly conductive. My guess is it's based on particles of copper.

- Anonymous

wow, 7 hours, that's impressive. there's something to be said for that DIY sense of accomplishment

For all I know my pen has dried up, but last I saw it the cap was still firmly on top so I would hope it still works. I know it worked a couple years after I bought it when I stumbled across it in a drawer.

Ah, I remember that stuff. It was the bomb for overclock resistor mods on anything from a 603 to a G4. I must've gone through several bottles of it.

where in the bloody hell can I get some of that stuff!!
any online places or part numbers or brand names??
I have had missing lines on the dodge rear window for years thanks to an over exuberant use of a plastic window scraper to remove frost from the window by one of my over exuberant kids.
However the 95 micra has one of these mylar printed circuits for the instrument panel and parts of it have failed in the extreme cold and heat and need to be touched up.

-v

type in http://www.partco.fi/ click the haku/search button and type in hopeamaali/silverpaint?

Are there any auto parts stores around you?

Everyone of the small shops here carries it.

vilppu,

If you can't find any around there, let me know. I can drop a kit in the mail...

- Anonymous

thanks Miero, I will try to see if I can get some at one of the local shops, now that I have a name of the product and one brand someone probably has some around here.


-v