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Nexus 4′s Glass Back, the Worst Idea Since the Last Phone With a Glass Back (droid-life.com)
32 points by adambyrtek 1784 days ago | hide | past | web | 62 comments | favorite

The problem isn't with glass, it's with the wrong glass.

If anyone hasn't seen the promotional video for Corning's new Gorilla glass, they should:


There is no reason why a glass back needs to be this fragile. Shattering from thermal shock is absurd, and the glass must be under some kind of stress from how it's secured to the phone. You can rightly disagree with the use of glass in an iPhone, because of course it's better if a phone can survive a drop, but at least it's not going to break just from being there.

It's probably more likely that aliens took his phone, broke it, and placed it back on his counter, than the glass having shattered from thermal shock.

Here is a more likely scenario (that my friend the materials engineer gave me):

Gorilla Glass is made by "stuffing" ions into the empty spaces so that the glass is under very high compressive stress. It's really known as "High ion exchange glass" This in turn, gives it very high compressive strength. However, it does have a significant downside that never gets mentioned: Shock absorption and scratches can cause later cracks and shattering. This is just a fact of life. When you place the outer layer under compressive strain, and then begin to compromise part of the outer layer, or begin to stress it, you can eventually cause release of those compressive forces. Once partially compromised, it may seem to be good, but can fail instantly.

>It's probably more likely that aliens took his phone, broke it, and placed it back on his counter, than the glass having shattered from thermal shock.

Completely agreed. That's exactly why I said "shattering from thermal shock is absurd, and the glass must be under some kind of stress from how it's secured to the phone" in the parent comment.

To further your explanation a little, the reason the outermost layer is put into compressive stress is that, when it's scratched, the stress will cause the crack to "close up" and so the glass doesn't shatter. Unfortunately, the interior of the glass is under tensile stress as a result, and so if the scratch happens to be deep enough to reach that tensile-stressed layer then the glass will shatter. Putting the glass in a case which alters this carefully managed stress state, i.e. by trying to attach it to a rim that's acting to pull it slightly apart, is what can cause this kind of failure.

But this is all speculation on my part, and even if true the reality might be more subtle.

Edit: I just found a good article from AnandTech that explains some of this. Take note of the first figure in particular.


For further information and examples, see Prince Rupert's Drops.


I suppose it is a testament to Corning's marketing that they are held in such high regard, but doesn't the Nexus 4 have the new Gorilla glass? Wired claimed it did: http://www.wired.com/gadgetlab/2012/10/nexus-hands-on-with-g...

It does, on the front and back [1].

I took a set of keys, a fork and a pocket knife to the front and back glass panels of the Nexus 4 and couldn't get a scratch to show up anywhere. I also slipped and dropped the phone while pulling it out of my pocket this week, and it showed no signs of my fumble.

Until I see a video, I'm not really convinced, tbh. If he has a granite counter-top, and didn't set it down as gently as the author claims, it's completely probable that it cracked. People are incredibly clumsy with phones. Glass doesn't exactly have a high thermal conductivity (nor does granite/linoleum/plastic), I find it difficult to believe the glass would expand/contract enough from body heat/kitchen counter-tops.

[1] http://www.wired.com/reviews/2012/11/google-nexus-4/

People are incredibly clumsy with phones.

Which seems like a pretty good argument for not wrapping them in glass.

Too often in technology we build things that are fragile, and then blame the user when she breaks them. Tools should be designed to work with the user as they are, rather than as we would wish them to be.


Your comment is wrong from beginning to end.

Normal window glass is Mohs hardness 5.5 or so, as is unhardened steel (your fork and pocketknife); hardened steel (e.g. a metal file) is more like 6.5. That means you can scratch regular steel with glass and vice versa, with some difficulty. (Try it. I just did.) Brass (your key) is around 3 or 4, so it won't scratch glass.

There are lots of things with Mohs hardness above 5.5, including most common metals (except brass, aluminum, copper) and most rocks.

Sand is almost never made up of glass particles. It's often made up of crystalline quartz (Mohs hardness 7) which can scratch regular glass easily. Gorilla Glass has Mohs hardness of about 9, so quartz won't scratch it.

Notable, then, is the fact that Apple felt the need to make their lens covers out of sapphire (Mohs hardness of 9). If they were using Gorilla glass on the back, and it has the hardness you claim, then surely that isn't necessary?

I have no idea if Apple was using Gorilla Glass on the back, nor did I know whether GG is harder or softer than sapphire. I'd assume softer, since it's just a glass, right?

http://www.corning.com/docs/specialtymaterials/pisheets/PI23... gives its Vickers hardness as 701 kgf/mm^2, which http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness#... would seem to place in the 5-6.5 range of the Mohs scale, nowhere close to 9. However, Vickers is a scale of resistance to plastic deformation, while Mohs is a (highly nonlinear!) scale of resistance to abrasion, so perhaps take that with a gram of potassium chloride.

Other random places suggest sapphire's Vickers hardness is around 1800-2200 kgf/mm^2, which is substantially harder than the number Corning's brochure gives for Gorilla Glass.

Optical sapphire has different properties than gorilla glass. There can be reasons other than hardness for using a material as a lens cover.

Agreed; but Apple did state specifically that they were using it because it was more durable. In regards to optical properties, some people are speculating the sapphire is the cause of the iPhone 5's worse susceptibility to lens flare.

Deleted. Thanks for making your comment standalone so nobody else has to waste their time reading mine.

I'm glad it is helpful!

It's not unlikely that they only went with Gorilla glass for the screen-side of the device to cut costs, though I know the article says otherwise, so maybe not. They could've also mounted it in a way other than what was designed (i.e. put it under tensile stress).

As for Corning, in fairness to them they were instrumental in the development of this type of glass and own a fair few patents, so it's not just marketing. They developed it originally in the 60s, though I imagine a lot has changed since then.

Scratch resistance and toughness are orthogonal to each other. Even diamonds will crack when applied with a certain force.

From what I understand, Gorilla Glass is only scratch-proof, not tough.

I disagree. It's how the glass is attached to the phone.

This is just a theory, but I've discussed it with People Who Know Things (TM) and they all have agreed that it's more than likely a small sliver of plastic or glass (or maybe just a tiny dirt particle) has become lodged in the space between the glass and the phone during fabrication. 9/10 phones don't have these defects, but when you're manufacturing millions of phones 90% still leaves a lot of bad phones.

I've never seen anybody use an iPhone 4 without a bumper due to AntennaGate. The bumper keeps the glass from coming into full contact with a surface, and that's probably why the iPhone 4 seems to be less affected by this problem. The lesson appears to be to always use a bumper with glass backed phone.

Not sure whereabouts you're from, but in the UK AntennaGate wasn't particularly concerning and I know plenty of people that kept their iPhones case-free, myself included, without glass shattering issues. Unless they were really, really silly and dropped it onto concrete from high up.

This is complete conjecture. Plenty of people use their 4s 4Ss without bumpers or cases with no problem, including me. It has be a design flaw outside of the base materials involved.

That's anecdotal though. My wife broke her 4S twice. What does that say?

I don't think you necessarily need a case to benefit: I don't use a case but slipped on a marble floor once and dropped the phone straight onto the floor, causing it to bounce a few times. The rim of the glass dented (what looks to be a thin plastic coating on the side of the glass?) but nothing shattered.

In any case, IIRC, speculation is that only the screen side of the iPhone uses Gorilla glass, but I'm not sure if that's changed with recent generations. But even without Gorilla glass, you can still use "standard" toughened glass that, correctly mounted, should never shatter just from the sort of thermal shock described in the article.

I have a 4S that slipped from my pant pocket onto a rough concrete floor from sitting height. The rough surface dented the plastic trim, causing the glass to shatter. I believe they went with the plastic trim due to the problems of joining glass and metal. But the plastic trim is the iPhone 4's Achilles' heel.

If we want to get anecdotal I used my iPhone 4 from launch with no bumper (even after I got the free one). I even dropped the phone three feet directly on it's top left corner and only the dented the metal band.

Twice I've dropped my un-cased iPhone 4s from a height of around 1 meter onto a solid tiled floor, and to my surprise not even a scratch.

Maybe I just got lucky, but in my limited experience, the case is not needed to protect the glass.

Most phones will usually survive such a drop. It all depends on how it lands. Phones with a glass back have double the number of ways that they can break when they fall, but it's still less likely to break than not. Drop it enough times and it will eventually break.

But the OP is talking about breakage due to thermal shock, not to physical shock.

The glass on the iPhone is actually quite resilient. The problem is the drop on one of the 4 corners (technically 8). At least that is my theory. All of the broken glasses I've seen have started at one corner and radiate out.

The sound design on that video was brilliant.

Another easy to correct mistake is the micro-USB cable they included. It doesn't have the USB logo on it to indicate which end is up, which is in violation of the USB spec.

Better USB cables emboss the logo so that one can tell which end is the top even in the dark.

But the absolute best is Logitech's solution: http://www.ebay.com/itm/Original-Logitech-Micro-USB-Cable-/2...

Logitech's solution ensures that you always effortlessly plug your cable in correctly on the first try. No need for reversible connectors like lightning, just use a well designed cable.


it appears most people aren't seeing the innovation. Check out the last picture in the linked set. There's a very large bump on the micro USB end of the cable that ensures that it's pretty much impossible to pick up the cable with the top end down.

> just use a well designed cable

Regardless of what you do with it, there's no way a USB cable can be called "well designed." A square connector is still a square connector, and no amount of embossing will change that. Attempts to make USB connectors reversible* are well-intentioned, but will always be more fragile and expensive than a connector that's either designed to be reversible from the start or breaks the symmetry such that you can't even attempt to put it in the wrong way.

*e.g. http://www.flipperusb.com

The Micro-USB connector is not square.

With normal USB, true, it can be annoying to find the right orientation, but they still seem to be zillions of times more sturdy than the cables before them. Remember PS2 with those tiny pins inside?

Agreed. The fact that we managed to get a versatile, standardised cable is a miracle and one I'm grateful for. But just because PS2 was bad, doesn't mean USB couldn't be better.

Sadly, every micro USB cable needs a "normal" (Male A) USB connector at the other end.

Sure, I have nothing against improvements :-)

The problem I have with USB cables isn't fixed with letting me know which side of the cable is right-side-up. The problem is that different computer manufacturers have different ways of installing USB ports. On some computers, they're right-side-up. On some, they're upside-down. Most of my fumbling comes in not knowing which way the port is flipped on the physical machine.

At least on my Thinkpad, the interior plastic is bright yellow rather than black. This makes it a bit easier. Still, switching machine to machine as often as I do becomes frustrating.

On ThinkPads the bright yellow USB ports are ones that are powered even when the computer is turned off. You can use these as charging ports for phones and other devices. Usually only a subset of the ports are powered like this and marked yellow, so this isn't a feature primarily designed to make it easy to plug stuff in correctly.

I've been a loyal Thinkpad user for how long and I never knew this? Thanks for the heads up.

The best solution is to have an omnidirectional connector like Apple's lightning port.

  But the absolute best is Logitech's solution: http://www.ebay.com/itm/Original-Logitech-Micro-USB-Cable-/2...
Which is? It looks like a regular USB cable with an embossed logo.

On the USB side, yes, but the micro-USB side has a HUGE bump on it. The pictures make it hard to see. The last picture in the set is the clearest.

I see it now. Yup, that's a bump. I hope my picky Nexus 7 likes it.

The Nexus 7's connector is upside down so the bump makes it sit on an angle, but it does work.

There's a limited amount of polishing you can apply to any USB turd.

I feel for the little metal tabs that hold the micro-USB connector in, the longer side is scrapey while the shorter side is not.

This is exactly what I do. I don't even have to look at the connector

It'll be interesting watching how the Android community deals with this, as they poured scorn on the fragile iPhone 4/4S glass back (note, happy, clumsy, ex-iPhone 4 owner, didn't break for me). They're right though, I'm surprised they didn't learn from the example of Apple and how many people did break their back glass.

Although glass cracking from a temperature shift is pretty odd, I would have thought it'd have gone through testing to isolate faults like that.

I love Android and want a Nexus 4 but this was goddamn stupid and pointless.

I'm so glad I spent four hours reloading the Google Play store page for the privilege of buying a Nexus 4.

Man, I feel like a jack ass.

I ended up throwing together a script that pressed the "proceed" button repeatedly until it worked. Took around 45 minutes even then.

I bought knowing the hissing noise problem and plan to watch how that (and now this) develop in the 4 weeks waiting period an cancel if it gets too absurd...

The great thing about Android is that I can use the platform on top of the line hardware without buying this phone if I want. Glad I went Samsung Galaxy S3.

I've got a Nexus 4 (with the official bumper on it though), dropped it numerous times, bumper has scuffs and dents in it. I'm in Boston, it's cold outside and room temp indoors.

Both front and back glass are still pristine.

Isn't the glass back fluff anyway, because there is still plastic underneath? I hate superfluous ornaments on utility devices...

I always love these stories, because everyone pretends to be a materials science engineer in the comments.

Yet none of them know the difference between hardness and brittleness. Even a noob (real) machinist knows more metallurgy than that.

We have to face facts. Modern american cell phones are basically the same economic era as pre-imports american cars. Much as domestic cars were value engineered to rust out in two years, at least until the Japanese conquered the market, we're going to have to tolerate expensive phones that are designed to fall apart until the (Chinese?) import phones that survive twenty years and everyone else has to catch up to them. A glass back is to cell phones as tail fins are to cars.

What are these "american cell phones"? All Nexuses (Nexii?) have been Korean or Taiwanese.

The great thing about Hacker News is that usually somebody comes along with a proper schooling, like I did here:


Nothing brings out the experts like something being wrong on the internet.


I had heard that one upside to the glass back is the RF transparency. How much of a difference this makes however I have no information on.

I was one of the people mocking the glass on the iPhone 4, and also sorely disappointed when I saw it on the Nexus 4. Hasn't stopped me from ordering one though... and a silicone full case to put it in.

New rule of thumb in mobile... 4th gen, try a glass back, 5th gen... bail on that idea?

You need glass or plastic. That's why the iPhone has those glass parts at the top and bottom still.

I have absolutely nothing to back this up, but I feel like the glass back is a emotional and subjective tactile distinction. My iPhone 5 feels cheaper than my iPhone 4. One of the biggest reasons (aside from weight), is the aluminum back. I don't know why, but it just feels cheaper. Maybe because I know glass is fragile, therefore I subconsciously place higher value on it.

Can't nobody get nothing right. Plastic is too cheap and flimsy, glass is too heavy and fragile. Maybe the optimal solution is what Apple's doing now with the mostly-aluminum (or should I say, aluminium) back.

That being said, seems like the author of this story was just incredibly unlucky. The unfortunate thing is, if your phone had a defect in the glass, you could never convince the manufacturer to replace it under warranty, since they'd just assume you dropped it.

Someone needs to rebrand plastic. Is there any actual objective problem that plastic phones have? Is it really impossible to achieve a "premium" feel, or does no-one bother because it's so much easier to brag about using 'diamonds' for cutting (how innovative!) or 'aircraft-grade aluminum' and confuse the average consumer.

Those Nokia devices look pretty good to me, even they had to call them "polycarbonate" to avoid the dreaded "plastic" word.

I've had the Nexus 4 for over a week now. For me the glass shattered where the speaker hole is located. I checked the mall everyday for a Nexus 4 case. Pretty annoying. Aside from that I really love the phone and 4.2. There should be cases available the day you buy a new phone though.

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