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Teardown: Apple MacBook Pro ‘Butterfly’ keyboard mechanism

Apple has made yet further tweaks to its controversial laptop keyboard

Last year, Apple acknowledged users were still having problems with the innovative ‘butterfly’ keys it introduced on higher-end laptops in 2015 – and put them through a third design rev as covered in our December 2018 Teardown.

With the release of an updated generation of MacBook Pros in May, the company said that it had made further improvements. It also extended its four-year keyboard service programme to all butterfly models (some of those with later fixes were not originally covered).

With the overall hardware design crossing over from the 2018 models in essentially every significant way (though with a shift up to Gen 8 and Gen 9 Intel Core processors), the keyboard is our focus. There too, the physical design remains unchanged but there have been changes to the materials. An iFixit teardown, aided by the Materials Engineering Department at Cal Poly and Niebuhr Metallurgical Engineering (NME), has identified some, possibly all, the areas that Apple has addressed.

 

Here is a recap of why the key mechanism matters, how it works and its main constituents.

The ‘matters’ part is simple enough. Compared with the traditional ‘scissors’ design, butterfly keys have a lower profile, enabling a 40 per cent reduction in the thickness of the keyboard. It’s all about a parallel Moore’s Law for laptops: reduce the product’s weight and thickness every 12-18 months but maintain performance and you get to increase your margin.

Butterfly keys contribute to this goal through a patented design that has four main elements: the key cap, a mechanical frame that controls and regulates downward pressure, a dome switch cover made of a flexible material and a metal dome switch that makes contact to signal the keystroke.

 

The biggest problem with earlier iterations was contamination. This has been progressively reduced by measures such as the addition of a single die-cut silicon membrane to reduce ingress and the redesign of some of the more sensitive or frequently trafficked keys, notably the space bar. However, users have continued to complain of double entries or no response at all. Within much of the laptop press, the feeling is that while the controversy may have been stoked by a social media pile-on, Apple’s brand in computing is nevertheless being damaged.

An important factor is that there are likely as many if not more customers willing to pay extra for Apple products because of their perceived reliability and longevity as their ease-of-use and aesthetics.

Apple’s bind over whether to fold or double down has been well captured by Eric Beaton from the Cal Poly team. “That is a very hard question to ask an engineer because, as engineers, we can always make it better,” he says.

“But it takes time, test, and, as a company, you don’t want your customers doing your testing for you – which is sort of what’s going on right now.”

So what’s in the double down?

The iFixit comparison of last year’s third-generation assembly and today’s highlights two areas.

First, there is the dome switch cover. “The cover in the 2018 model is semi-opaque, somewhat tacky, and feels like silicone. The new model is clearer and smooth to the touch,” notes iFixit (see opposite).

Second, there is the dome switch itself. Because this is arguably the most vulnerable of each key’s components – facing damage due to everything from fatigue and dust to heat, moisture and more – it is an obvious candidate for some kind of materials upgrade. Differences in the surface finish between last year’s and this year’s model again suggest that has happened.

 

Through the use of Fourier Transform Infrared (FTIR) spectroscopy at Cal Poly, iFixit believes it has identified the materials change on the covers. By exposing the two models to IR light and analysing how the cover polymers absorbed the light, it has concluded that the change has been from either polyacetylene or thermoplastic polyurethane to polyamide (better known as nylon).

 

“It makes sense that they would go to a nylon if they were having issues with the prior polymer not performing, ripping or just failing anyway,” David V Niebuhr of NME explains. “I know from experience that nylons are fairly robust as polymers go from a structural standpoint. They have good mechanical strength.”

 

Improvements made to the switch, though, are harder to detect explicitly, even for an expert in metallurgy like Niebuhr. His thinking is that Apple had two options here: to increase protection around the switch and make another materials change: “My gut says they’re probably doing both, saying this is a big enough issue that we’re going to attack it from every direction we can.”

The iFixit conclusion is, therefore: “The difference in surface finish from the 2018 version to the 2019 indicates Apple may be using a revised heat treatment, or alloy, or possibly both.”

 

The strange thing about all this is that Apple is being very coy about exactly how it is addressing a problem that comes up as a ‘Watch out’, even if a potential customer undertakes a cursory product search online. Having gone through four revisions of the design, and suffered criticism on each, one might have expected more. The issue is not just about building more confidence in a particular innovation, but also in what are high-end, and therefore expensive, laptops.

Instead, as Eric Beaton suggests, this feels a bit too much like a particularly pricey pay-to-play beta.

Meanwhile, iFixit reviewed the broader repairability of the 2019 15-inch MacBook Pro Touch Bar, which featured the latest key revisions.

It found that upgrades and repairs to the processor, RAM and flash memory will be “impractical at best”, as are individual replacement of the battery, speakers, Touch Bar and main keyboard assembly. Meanwhile, the integration of the Touch ID sensor, with the power switch and the T2 security chip, means that something as basic as fixing that switch “may require help from Apple, or a new logic board”. One out of 10.

Key components: Butterfly assembly (see images above)

1. Dome switch

2. Dome switch cover

3. Butterfly frame

4. Key cap

5. 2018 dome switch cover (TPU/polyacetylene)

6. 2019 dome switch cover (Nylon)

7. 2018 dome switch

8. 2019 dome switch

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