Categories: Global Tech News

Aluminum 7003, Used in Roofing, May be Tapped by Apple for iPhone 6S/6S+

Well you win some, you lose some.  While I contended earlier this year that Apple, Inc. (AAPL) might look to a higher strength 6000 series alloy for its next iPhone, it appears that it indeed stuck with 7000 Series aluminum alloys that it first employeed in the Apple Watch.

With a 0.302 in. (7.1 mm) profile, Apple’s iPhone 6+ was far more slender than the models that came before it.  But that blessing ultimately proved a double-edged sword as the razor-thin device also proved highly susceptible to bending.

The culprit lay in part in the fundamental challenges of the form factor (the phone is basically a big paddle lever in your pocket) and the material (aluminum alloys tend to be more vulnerable to deformation events than plastics).  But it was also partly that Apple chose a really cheap alloy.

With the impending launch of the iPhone 6S/6S+  — the ninth generation flagship phones in Apple’s line — the Cupertino company is looking to correct on the glaring design defect. And likely due to the burdens of rigorously testing its seriously overhauled metallic shell, a number of alleged iPhone 6S casings have leaked make the rounds in the blogosphere.

Somehow, some way, one of the first blogger-cum-iPhone users to report on “Bendgate” — Unbox Therapy video blogger Lewis Hilsenteger (@UnboxTherapy) — managed to get his hands on one of these prototypes.  The good news is that in an effort to dispel skepticism and further insight into the upcoming, unreleased ninth generation iPhone, he put the leaked prototype casing through not only rigorous inspection, but in-depth metallurgic analysis, as well.

Before we get to those result, it’s worth first saying that there’s no way to know with one-hundred percent certainty that the case he received was truly a finalized design prototype from Apple, rather than some eleborate fake or an experimental prototype.  To be fair, Hilsenteger himself offers such a disclaimer.  But I will say that after watching his analyis and following up on the numbers, I believe there’s strong cause to believe this is the real deal.

The first factor working in his favor, though, is the fact that there’s been so many body/shell leaks to date and that they’ve been so consistent.  From these leaks we know:

  • The iPhone 6S/6S+ bodies will likely look almost identical to those of the iPhone 6/6+.
    • They even has the same positioning for internal circuit board mounts!
    • The only major difference is the speaker’s raised screw mount moved upwards to accomodate what’s expected to be a larger speaker (possibly a tie-in to Apple’s recently acquired “Beats” brand).
  • The interior metal is subtly different, as hinted at by a smoother surface, indicative of a higher grade of anodization.
    • This likely indicates that the body has been made more rigid, as was widely expected, to combat bending!

One of the most extensive leaks comes courtesy of Future Supplier who a little over a month ago got their hands on on a prototype iPhone 6S+ shell with anodized with a gold tint.  The body is strikingly similar to the one seen in the Unbox Therapy video. 

[Image Source: Future Supplier]
The prototype is seen on the left above, the iPhone 6+ body is seen on the right.  As the crude red annotations to the image by Future Supplier illustrate, the position of the mounting slots is mostly the same, other than the aforementioned speaker-related shifts.

Here’s a more extensive collage of the images taken by Future Supplier.

[Image Source: Future Supplier]
When compared side by side it’s clear that there are both similarities and differences between the two leaked prototypes.  There’s a good reason for that.  The Future Supplier case is reportedly a leaked iPhone 6S+ prototype.  By contrast Unbox Therapy has a supposed iPhone 6S body.

[Image Sources: Unbox Therapy; iFixit [iPhone 6 Teardown]; iFixit [iPhone 6+ Teardown];
eTrends; Future Supplier]
As you can see both the alleged iPhone 6S and 6S+ prototypes both showcase the same shift in the speaker mounting hole on the upper left of the rear housing.  The iPhone 6S also sees a shift in one of the bottom left mounting holes.  Where as the iPhone 6S saw one of the mounting holes in the bottom right hand quadrant move upwards, slightly, the iPhone 6S prototype sees the elimination of the second mounting hold int the center of the phone towards the bottom.  In its place is a single mounting screw hole.

Unbox therapy examines the composition of the apparent prototype via a technique called X-ray fluorescence (XRF).  

As heavier elements, the transition metals typically have a lot of electrons in their shells.  By blasting a material with X-rays — electromagnetic radiation in the keV energetic range — lower shell electrons can be excited knocking it off the atom.  An electron from the next shell will rush to fill this lower energy position, releasing some energy in a secondary X-ray in the process.

XRF is depicted in diagramatic form. [Image Source: Thermo Fisher Sci.]
The energy of this emitted secondary X-ray versus the power of the input X-ray that triggers it is unique to a certain metal on an atomic metal.  Hence by scanning over a range of X-rays of different intensities and watch the strength of the response, an XRF unit can tell whether a certain kind of metallic atom is present, and if it is, in what quantity (based on the intensity of X-rays returned).

The XRF “gun” detects the incident fluorescence and uses it to ID the composition of the alloy.
[Image Source: Thermo Fisher Sci.]
Hilsenteger borrows a common handheld XRF tool for analyzing metal scrap, Thermo Fisher Scientific Inc.’s (TMO) Niton XL3t.  From the trim, this looks to be the GOLDD+ model, the most reliable of the series.

The composition of the old alloy is estimated at:

  • Alumnium (Al) — 98.85%
  • Iron (Fe) ———   0.064%
  • Magnesium (Mg)-   0.758%
  • Silicon (Si) ——-   0.321%

As Unbox Therapy states, this is the most commonly used type of aluminum alloy — 6063.  It’s a so-called Al-Fe-Mg-Si (Aluminum-Iron-Magnesium-Silicon) 6000 Series alloy, aluminum 6063.  To give an idea how common this alloy is, six pages (pg. 162-167) are devoted to it alone in the tables book Worldwide Guide to Equivalent Nonferrous Metals and Alloys [Google Books] by Frank Cverna.

Gun readouts for the iPhone 6 and 6S, side by side. [Image Source: Unbox Therapy]

A printout of the iPhone 6 reading is also shown in the video. [Image Source: Unbox Therapy]

…as is the readout for the supposed iPhone 6S.  [Image Source: Unbox Therapy]
The ‘AA’ presumably stands for Alcoa Inc. (AA), one of the largest global suppliers of mass sheets and extruded bars of aluminum and other lightweight metals.  Alcoa has been cited as an Apple aluminum supplier in the past, and its strong Chinese presence means this one makes sense.

While aluminum 6063 is not far from pure aluminum (w/ nearly than 99% of the content by weight being aluminum atoms in this blend), small fractional percentages of alloying elements subtly change and improve upon its performance.  The properties of various alloy metals is seen below except for iron, which causes a slight increase in strength [source].  So looking at aluminum 6063, we see that it gets the biggest strength boost from its low level zinc impurities, gets enhanced heat treatability and corrosion from silicon impurities, and gets a tiny strength bump from the iron impurities.

[Image Source: AluminumDesign.net]
Over all this 6000 series aluminum is relatively good when it comes to machinability and corrosion resistance, but it isn’t very strong.

In the Unbox Therapy video, Hilsenteger uses a clamp/scale setup (possibly custom-built) with a digital scale from Smart Weigh Scales.  Another test was performed by Consumer Reports last year on the iPhone 6 and 6+, as well as a variety of other devices.  

That test used a compression test rig from Instron (a Illinois Tool Works Inc. (ITW) subsidiary) to carry out a similar “three-point flexural test”, as the Consumer Reports dubs it.  The key difference is that the Consumer Reports test exerts forces on a single point in the middle, versus two points for the Unbox Therapy test.

The test by unbox therapy is seen on the left; the test by Consumer Reports is on the right.  Arrows indicate the loading points.
But ultimately both tests wind up being governed by the same equation where F is force on the loading pin (or support pin in the Unbox Therapy case).  The simple equation to represent this is:

σ = 3LF/(2bd²) where L – specimen length; F – force applied via loading pin; 
b – specimen width; d – specimen thickness
But that assumes a rectangular cross section.  The phone’s corners are curved, so in reality bending is governed by some more complex equation.

From the Unbox therapy, we see the bending resistance is overcome at around 29.9 lb⋅f (lb of force) (13.6 kg⋅f).  Bending occurs in the volume button weak spot.  With the buttons and circuit boards in place, and the glass screen glued on, bending force increases to 70 lb⋅f (31.8 kg⋅f).  So it appears, based on these numbers, that around three-sevenths of the rigidity comes from the aluminum shell, and the rest comes from the adhered glass plate and internal elements.
The new shell bumps the bending resistance to nearly 80 pounds for the shell alone — nearly a three-fold increase in strength.  Assuming the internals stay roughly the same, that’d give a total bending resistance of around 120 lb⋅f (54.4 kg⋅f), a 71 percent improvement over the old bending resistance.
 
The force to bend the previous generation model was roughly akin to the force required to break three pencils. [Image Source: TabletActiv]
Consumer Reports likened the force needed to bend the iPhone 6S as being “approximately the force required to break three pencils”.  So the new iPhone 6S should stand up to about the force required to break five pencils — a bit harder to do with leverage from your hip.
Unbox Therapy lists the composition of the iPhone 6S case as:

  • Alumnium (Al) — 92.81%
  • Zinc (Zn) ———   6.16%
  • Magnesium (Mg)-   0.911%
  • Iron (Fe) ——-   0.061%

The presence of zinc confirms that this is a 7000 series alloy. The absence of copper (Cu) indictates moreover that this is Al-Zn-Mg, a so-called “copper free” subcategory of the 7000 series.  Copper to the 7000 series adds benefits similar to silicon in the 6000 series, increasing heat treatability, hardness, and strength.  However, it also sharply increases the tendency to corrode.

By dropping copper, Apple gets a 7000 series alloy that’s still substantially stronger than the low grade 6000 series alloy previously used, with only modestly worst corrosion character (zinc also has a tendency to corrode when subjected to stress).  To remedy the corrosion issue, Apple seems to be simply applying a thicker anodization, which has the upside of giving a smoother surface.

Anodization is simply an oxidized outer layer of material that serves as a barrier to corrosion and scratching.  It also offers a medium for Apple to electrolytically deposit various inorganic/metallic dyes into.  Apple is rumored to be prepping a pink dye to add to its dark gray, silver, and gold tones.

Here’s a collection of some of the supposed “pink” iPhone 6S images that have been appearing on Chinese social media (courtesy of WCCFTech):

A final note — Unbox Therapy stated that the new alloy was unable to be identified, but was in the 7000 series.  I actually found two different alloys whose chemical composition it would fall within the limits of– Aluminum 7003 and 7046A.  Of these, aluminum 7003 is fairly common; aluminum 7046A is not (note: 7046A is different from aluminum 7046).  And Alcoa advertises aluminum 7003 in various product brochures.

The body is rumored to be machined by Tainan City, Taiwan-based Catcher Technologies Comp., Ltd. (TPE:2474), based on comments from its CEO who was bragging earlier this year about winning a big order strongly hinting that Apple was involved.

Cost-wise, Aluminum 7003 is selling for around $2,000-5,000 USD per metric ton, on Alibaba.  At $1,000-2,000 untempered aluminum 6063, is as little as half the cost.  So Apple’s material costs will likely rise sharply for the case as will the time required to anodize them, given the thicker layer of oxidization.

Returning to my original suggestion that Apple might opt to use a strong 6000 series alloy instead of a 7000 series one, I still contend this approach would have some advantages.  The alloy Apple is using, based on the testing, appears to be basically the same strength as the aluminum 6013 used by Samsung Electronics Comp., Ltd. (KRX:005930) (KRX:005935) in the Galaxy S6 (GS6) and GS6 Edge.

However, the cost difference between 6013 and 7000 series alloys isn’t ultimately as big as my initial research on Alibaba seemed to suggest.  Ultimately, I suspect that familiarity working with the particular 7000 series alloy and availability (Samsung likely is consuming much of the aluminum 6013 production already) are likely key factors why this route made sense for Apple.  Apple and Samsung both have found different alloy routes to achieve similar strength at similar costs.

Versus the cheap alloy used in the previous two iPhone generations, the benefit is not only increased strengt, but also the opportunity for new dyes, while maintaining the other benefits of the original material.  And in the grand scheme of things the cost of the casing is only one small part of cost of materials for the phone, so this shouldn’t hurt Apple too badly in terms of the overall bill of materials.

To conclude, whether or not Apple is using something it calls aluminum 7003, suffice it to say it’s pretty close to aluminum 7003.  Aluminum 7003 is a pretty impressive alloy.  Thanks to abandoning the copper it’s resistant enought to be used in roofing applications, among other things.  Aluminum 7003 roofs benefit from the alloy’s excellent strength and shapability.

And soon the ninth generation iPhone may enjoy those benefits, as well.

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