Can a Cracked LCD Glass be Repaired or Should I Just Buy a New Clock?

[JT Smith]

TL;DR

Is it possible to reuinite trace with LCD segment?

I have a small LCD clock and a corner of the LCD glass cracked and separated. This small region of the glass lines up with one of the pads on the circuit board and the result is that one of the segments is non-operative. I look at the LCD glass and I can't see any sort of circuit trace. Is the conductive part of the glass LCD element transparent? I don't have a good picture of how this connection works.

More to the point, is there any hope of bridging the gap created by the cracked corner of the glass? Could I put a little solder blob there or something like that?

Or should I just buy another cheap clock? :-)

 

[Jody]

Speaking from a technician point of view, not an engineering one, replacing screens are expensive. When people crack the screens on more expensive items like monitors, laptops or televisions, then the price of repair is comparable to buying a new item. As an engineer I don't work on displays myself neither do I know almost anything about it at all although I've noticed some people... their only job is to engineer displays, and I've heard it's really difficult from people I trust.

 

[DaveE]

Summary:: Is it possible to reuinite trace with LCD segment?

should I just buy another cheap clock?

yes

 

[Averagesupernova]

I used to work for a company that was 'display heavy' in the finished product. Never ever that I was aware of, any display got repaired instead of replaced. The best you could hope for is pushing on the display in a certain way as to make a connection that was broken when the glass cracked. At this point, you would find a way to keep constant pressure on the glass.

 

[JT Smith]

yes

I already know the reasonable answer to my second question. The point of posting was to find out about the first.

The clock is an inexpensive piece of disposable consumer electronics. Fixing it is just for fun, mainly... if it's possible. It's actually usable as is since the missing segment is the bottom one so all ten digits are unambiguous.

I was just wondering how these things actually work. Where is the electrical connection on what appears to simply be a piece of glass?

 

[DaveE]

I already know the reasonable answer to my second question. The point of posting was to find out about the first.

The clock is an inexpensive piece of disposable consumer electronics. Fixing it is just for fun, mainly... if it's possible. It's actually usable as is since the missing segment is the bottom one so all ten digits are unambiguous.

I was just wondering how these things actually work. Where is the electrical connection on what appears to simply be a piece of glass?

It's hard to answer without seeing the real thing. My guess is that the electrical connection is a bit of metalization deposited on the glass, perhaps at the edge between layers. Just because you can't see it easily doesn't mean that there isn't some sort of conductive coating there.

The questions "How does it work?" or "How is it made?" are quite different from "How should I repair it?" or "Should I repair it?". It will be difficult to achieve a lasting repair that is worth the effort for this type of component. It is the nature of our high tech world that many products can only be built to perform well, with high reliability, long life, and at low cost in factories with significant engineering involved. Typically, this works against repairability.

If you do want to attempt a repair, I would suggest a bit of conductive epoxy (like what they sell to repair rear window defrosters in cars, for example). You can try to paint this over the area that was cracked to bridge that gap. The problem is that this may be an internal layer.

 

[DaveE]

Perhaps try a google image search for "lcd display construction" to see some of the complexity in what looks like a simple device.

 

[yungman]

Buy a new one.

 

[JT Smith]

It's hard to answer without seeing the real thing. My guess is that the electrical connection is a bit of metalization deposited on the glass, perhaps at the edge between layers. Just because you can't see it easily doesn't mean that there isn't some sort of conductive coating there...

...If you do want to attempt a repair, I would suggest a bit of conductive epoxy (like what they sell to repair rear window defrosters in cars, for example). You can try to paint this over the area that was cracked to bridge that gap. The problem is that this may be an internal layer.

Thank you. I can provide a photo, and I will if you like, but I suspect it wouldn't help much. Of course there's something conductive there that I can't see. There has to be. I was hoping to figure out a bit more about this invisible conductive trace so that if I attempted a repair I would have something, even if invisible, to kind of aim for.

I did google to try and find out about LCD construction but I didn't find what I wanted. If I had I succeeded I wouldn't be bothering you guys. Getting answers on web forums is less reliable than google. But it does work really well sometimes.

Conductive epoxy seems like a good suggestion. Thanks. I'll look into that.

Of course I should just buy a new one. Duh. A tube of epoxy probably costs more a replacement. That's not the point.

 

[alan123hk]

Once the spatial path through which the liquid crystal fluid flows is cut off due to the breakage and separation of the LCD glass itself, it is basically impossible to re-establish the connection.

Re-connection is only possible if the contact pads of the LCD glass remains at least partially intact. The contact pads is the only interface between the liquid crystal fluid inside the space between the LCD glass layers and the external circuit or connector (such as conductive coating, zebra paper, heat seal, pin, etc.) Even in this case, I don't think that ordinary users without relevant experience and tools can easily complete the task.

So the conclusion and suggestion is that it's better to spend the precious time for research to buy a new and better one.

https://handsontec.com/ezine_category/LED_LCD/LCD Application.pdf

 

[Tom.G]

For what it's worth, that invisible conductive layer could well be Indium Tin Oxide. It is often used on glass windows of electronic equipment when shielding is needed to block electrical interference, usually from escaping the enclosure.

By the way, electrical contact with the Liquid Crystal is not required. It is the electric field that causes the molecules to rotate to pass or block the light transmission. The only current drawn is to charge the capacitance between the front and back electrodes, with the Liquid Crystal being the dielectric.

Cheers,
Tom

 

[256bits]

Conductive epoxy seems like a good suggestion. Thanks. I'll look into that.

As an experiment , try a drop of conductive NaCl solution between the cracked glass interface to test if a connection for the bad segment can be made between the two parts. As long as the drop does not spread over to the connectors of the other segments, so its going to have to be a very small drop of liquid - tip of a needle is way bigger than 5 microns.

If it does connect, I have no idea how corrosive or destructive the NaCL ( or other conductive fluid ) would be towards the ITO or liquid crystal - maybe some other conductive fluid would be better, but you would have to find a way for the fluid to not dry out, with a coating or some sort on the cracked glass.You are looking at a sandwiched layer 5 microns thick for the liquid crystal, and way way less than that for the ITO thin film conductor.

Typical LCD sandwich

Note that the segments are also a transparent thin film ITO.

 

[JT Smith]

Thank you for the additional information. It sounds iffy at best. I can't easily do a salt water experiment given how the clock assembles. Backup plan is to draw in the missing segment with a permanent marker. Then 7 of the 10 possible digits will appear correct and I'll eventually get used to "J"=1, "y"=4, and "]"=7.

Or maybe I'll buy another clock. I can purchase a similar clock on Amazon for about $8, free shipping. The rear window fogger epoxy is $12. This is not a rational pursuit though.

I tried to fix our fancy toaster when the microprocessor on it started acting up. Had it all worked out, a schematic drawn, parts identified, and I was ready to implement my repair... then I hastily connected two wires I should really have known not to connect. POOF! I bought a much simpler toaster for $25, works great.

 

[DaveE]

The salt water is a great idea for an experiment. However, IMO, it's a terrible idea if you want a reliable repair.

 

[JT Smith]

Postscript: I fixed the thing.

It sat on the shelf for a while. Then I thought that rather than buy conductive epoxy I'd make some. I didn't have any silver sitting around, not that I could think of anyway. Nor graphite power. Pencil leads seemed to be poor conductors. So I sanded down a piece of 14 gauge copper wire and added the particles to some two-part epoxy.

When it dried my ohmmeter indicated no conductance. Huh. I was kind of wondering how a suspension of conductive particles in an insulating epoxy was supposed to end up as a conductor.

I broke down and spent the $12 on the rear window defogger repair kit that has conductive epoxy. I glued the piece of glass back onto the LCD and also left a little to dry on a piece of cardboard. Later I tested the sample on the cardboard and again, no conductance. WTF?

So I just put the clock back together and the missing segment was lighting up! I guess my ohmmeter test was faulty somehow. Maybe my homemade epoxy actually was conductive? The problem was that a different segment was now missing and with some digits the whole screen went blank.

I guessed I was too sloppy with the epoxy and shorted out a neighboring column in the matrix. So I scraped off as much epoxy as I could and rebroke the glass. I tested it like that, with the missing piece of glass removed, just to see that I was back where I'd started with the one missing segment. Instead I found, much to my surprise, that it worked perfectly! I must have fixed the short but left just enough epoxy to connect the previously missing trace.

So now I have my 25 year old $8 clock working again. It only cost me $12 and a few hours of fiddling. It's very silly, I know, but it feels good.

 

[Jody]

So now I have my 25 year old $8 clock working again. It only cost me $12 and a few hours of fiddling. It's very silly, I know, but it feels good.

Worth every penny :) one heck of a success story thanks for sharing!

 

[256bits]

Postscript: I fixed the thing.
So now I have my 25 year old $8 clock working again. It only cost me $12 and a few hours of fiddling. It's very silly, I know, but it feels good.

I am totally impressed!

 

[DaveE]

More than $12 worth of entertainment and learning. I'd still buy a new clock though.

 

[Keith_McClary]

$12 on the rear window defogger repair kit

I figured that paint cost $10,000 per gallon.

 

[Keith_McClary]

(The video is about cakes, not repairing screens.)

 

[JT Smith]

More than $12 worth of entertainment and learning. I'd still buy a new clock though.

Yeah, it was kind of a crummy clock. I had to adjust the time more than just twice a year because it ran slow. And the adjust buttons were a little cranky. But still, it mostly did what I wanted it to do.

I say that in the past tense because this morning it was blank. I looked at it in shock and disappointment for a minute or so. I'm not sure how long because I didn't have a clock to time it. Then I wiggled the battery, pushed it's buttons, and stared at it some more. Finally, and unceremoniously, I tossed it into our big box of consumer electronics junk.

 

[JT Smith]

So I couldn't resist one last crack at it. I dug the clock back out of our electronics recycle box and opened it up again, cleaned it some more, fiddled with it, got it working again. And then it failed again. And started working again. And again. After several days it was clear that it cycled daily, on in the morning, off by evening.

So I put it in the refrigerator and it's been working perfectly ever since. I'm not sure where to go with it from here, other than back into the recycle box. The fact that slightly warmer temperature kills it is a clue but to what exactly I can't say. For now we know what time it is when we open the fridge.

 

[DaveE]

So I couldn't resist one last crack at it. I dug the clock back out of our electronics recycle box and opened it up again, cleaned it some more, fiddled with it, got it working again. And then it failed again. And started working again. And again. After several days it was clear that it cycled daily, on in the morning, off by evening.

So I put it in the refrigerator and it's been working perfectly ever since. I'm not sure where to go with it from here, other than back into the recycle box. The fact that slightly warmer temperature kills it is a clue but to what exactly I can't say. For now we know what time it is when we open the fridge.

Obviously, the next step is to buy a refrigerator with a glass door and put it next to your night stand.