Teardown: Samsung foldable smartphones

The foldable phone has been trying to make a comeback for nearly four years. There are new clamshell designs that recall the classic Motorola Razr but now fold out to offer the size of touchscreen seen as standard today. And there are book designs that open out to offer a small tablet – or ‘phablet’ – experience, while retaining a standard screen on the outside. The segment’s unquestioned leader is Samsung.

Its latest entries are the Galaxy Z Flip 4 (clamshell) and Z Fold 4 (phablet). At £999 and £1,649 respectively, these are premium-priced handsets, although they come with aggressive bargain options. Samsung will accept any smartphone as a minimum £250 trade-in against the Flip 4 and trade-ins of up to £580 against the Fold 4. You can also get a year’s worth of Disney+ streaming.

The deals reflect how hard it has been proving for foldables to get traction among consumers. The main problem has been reliability, particularly around the inner display.

Samsung itself postponed the launch of the first Fold from April 2019 to September when the first reviewers found the devices were easily damaged. Build quality also haunted launches from rivals such as Huawei and Motorola.

Flexible glass technology has come a fair way in the last three years. The latest types can be less than the thickness of a human hair. Handset manufacturers have also taken steps to provide better overlay protection for the inner displays. More recently, however, concern has moved from panels (though some remains) to egress by contaminants and their potential impact on the hinges. Once these start to fail, the inner screen will, again, not be far behind.

For its two new foldables, Samsung has taken two main steps to address these concerns.

With a further view towards consumers’ wallets, it has slashed the cost of screen replacement for foldables from $249 (£215) to $29, if you also take out a three-year Samsung Care+ plan.

However, as Sam Goldheart of repairability specialist iFixit has noted: “Let’s not forget the cost of the insurance. The basic package over three years will cost you $396. That’s essentially a total of $425 plus tax for a screen repair. We’re getting awfully close to that $499 figure for a standalone screen replacement.

“Still, three years’ coverage isn’t terrible, and if you’re accident-prone, it’ll only be about two uses before it pays for itself.”

Then, in addition to using the latest flexible glass technology, Samsung has also redesigned the hinges on both the Flip 4 and Fold 4.
Zack Nelson, who runs the JerryRigEverything YouTube channel on handset teardowns, describes what Samsung has sought to achieve in a recent posting.

“The new hinges are sectionalised, with metal plates connecting three separate hinge components. Last year and each year before that, Samsung gave us a complex construction of miniscule, little spur gears that helped guide open and close the fold uniformly. This time around, the metal halves are guided through little channels using grooves and joints instead of gears,” Nelson explains.

“The centre hinge constrains and locks the motion of the two halves as it rotates into itself. It looks like there is a darker graphite-looking lubricant in here as well, which is important for the metal-on-metal stuff.

“The top and bottom pieces are rather similar, although I assume these are more constructed to provide the resistance or holding force to keep the phone open or partially closed. But there is still a much smaller channel keeping the whole operation straight. Either way, neither of the three hinge components this time around have any gears.”

Samsung says that the hinges can go through 200,000 cycles. Given that flagship phones tend to undergo a two-to-three-year replacement cycle, that would imply owners checking inside their devices (notwithstanding notifications on the outer displays) a maximum of 180 to 270 times a day – that should do for almost all of us.

A question mark remains over ingress. Both iFixit and JerryRigEverything subjected the phones to durability tests, iFixit with fluorescent dust and JerryRigEverything with dirt. The results were mixed.

The iFixit test resulted in a click from the hinge. “That crunching is better understood as a death knell,” said Goldheart. The JerryRigEverything test did not, with the phone passing its durability probe.

The reality is that nothing can be made ingress-proof. For the latest Flip and Fold, Samsung only claims IPX8 water resistance and explicitly warns that the phones are “not dust-​resistant”, even though it has taken steps to mitigate the risk further, largely though its use of adhesives and gaskets.

However, this was not enough to break iFixit’s scepticism. “At the end of the day, the protection against dust ingress was improved, but imperfect. Which, in an ordinary phone, is to be expected – nothing is perfectly ingress-proof. But when you’ve got this many points for ingress, and that many pieces of precision engineering to protect – well, let’s say we’re expecting a bit more from the future of phones,” says Goldheart.