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Comment by amelius | Hacker News Reader

Why isn't a cellphone filled with epoxy?

How would you do screen replacement? That is a common repair since people drop their phones and currently you can get your phone repaired by some teenager in a booth at the mall. If you fill the phone with epoxy, how are you detaching the screen, and getting a new ribbon cable through the epoxy?

Just like they do it today - a lot of grinding, swearing and overall understanding what the civilization is going in not quite the right direction.

use pogo pins or a board to board connector

Which means air space that can get crushed. Either the phone is solid or it isn't.

> Which means air space that can get crushed

Would note that air isn't the only substance in a phone that compresses under 38 MPa. (Batteries come to mind.)

Air is the only substance that compresses to any significant amount. When you apply pressure to a battery from one side it may deform, but I would expect that the battery wouldn't be crushed because the pressure is from all sides - unless of course there is air in the battery - I'm not a battery chemist so take everything I say with some salt.

Note that I would expect water to seep into a battery at this pressure and that will cause all kinds of issues - including chemical fires underwater. Just not crushed batteries.

So what if you can't replace a screen on an epoxy-filled cell phone? That's a small price to pay for knowing that your camera will survive if you take a one-way trip to crush-depth.

Is this sarcasm? 99.999% people will never take it beyond a meter in a pool.

Poe's Law never fails. I should have accounted for that.

I'm sure there are some companies who want to do that, as long as they can convince people it's better for security or something.

When was the last time your phone stopped working due mechanical PCB damage?

Typically the limiting factor on your phone is the screen breaking, your battery life getting too short, wear and tear on components like buttons or the charging port, and factory defects. Epoxy isn't going to help with any of those. The only thing it would help with is exposure to water, but if other parts of your phone like your screen aren't water proof, what's the point?

Epoxy adds weight and manufacturing cost. It introduces design challenges as you need to balance the thermal expansion of the various parts. It's an extra step that can go wrong, and makes repair of other defects far more difficult. What benefit is there for the typical consumer that outweighs these costs?

To add to that. My son got his phone caught in a reclining chair without realizing it. The fact that the phone bent in half instead of destroying the chair is a nice bonus. Replacing the phone was cheap, replacing a chair would not have been — yes, both are insured, but replacing/repairing a chair takes a hell of a lot longer.

I think most would disagree XD.

Phones these days are often more expensive than the chair and can be pretty inconvenient to replace, especially if you have nonrecent backups.

Yeah not sure about you guys but me and everyone I know buys their stuff in ikea where a chair definitely doesn't cost more than a good cell phone

I got an Eames chair recently and would be devastated if my phone damaged it!

And for just a few bucks per month, it can be insured and replaced for a couple hundred bucks. My chair is also insured through homeowners insurance (the US equivalent name, called something different here in the NL), and they would give me the value of the chair… but now I have to find it again, get it delivered, take my old chair to the dump, etc. The phone was a quick visit to the Apple Store and restore from backup.

The GoPro Session actually took this tack to achieve waterproofness without a secondary case.

The heavy components on a cell phone PCB are reinforced with spot applications of adhesive to the PCB.

Filling the entire cell phone with epoxy wouldn’t help. The parts that break on drops are external like the screen.

This SD card was enclosed in a sealed metal container so it wasn’t exposed to water.

  > Why isn't a cellphone filled with epoxy?

Added cost and weight are two things that would put off consumers. The phone would also be neigh irreparable, but consumers don't seem to care for that other than replacing their screen.

OTOH, adding epoxy on top of everything else would probably only reduce their iFixit repairability score from 1 to 0, so...

A conformal coating wouldn't give much more weight.

A conformal coating isn't "filled with epoxy", which is the concern I was answering.

There is very little empty space in a phone, so conformal coating is practically the same as filling it.

Anyway, I wasn't disagreeing, just reasoning a bit further.

The point of filling it is to remove the compressible empty space so that large pressure gradients won’t crush it.

No, conformal coating and potting are extremely different things done for different reasons.

I'm not talking about which methods are being used, I'm talking about which methods could be used. Further, potting, where you let the epoxy drip off, gives you a conformal coating.

Conformal coating is much less viscous and would leave a layer orders of magnitude thinner then letting potting epoxy drip off. It's not at all comparable.

You are talking about a conventional conformal coating.

Neigh?

I didn't notice that, I was dictating to Gboard. If that's what was heard, then I should probably go eat some hay and get my tail brushed.

I think they meant “nigh on irreparable“.

Some claim we are centaurs, we say Neigh!

This joke seems like it would make more sense if centaurs didn't have human vocal tracts.

Well, most cellphones aren't subjected to the conditions found under three miles of frigid sea water. Epoxy is also really, really expensive.

Filling dive watches with oil (hydro modding) is pretty popular. It mainly helps with visibility but also increases the depth rating.

Because then it’ll become unrepairable. It’s a tricky trade-off that cell phones/tablets-laptops have to deal with. Easy to repair vs durable vs cost/time. And Apple (for example) cares about repairability because they also need/want to repair phones (warranty/trade in for example)

It's just not necessary, while having reliability problems of its own.

Because then it gets a 0/10 repairability score on ifixit :)

That can be avoided by filling it with a fluid that the repairman can simply drain instead.

People hydromod digital quartz wristwatches by filling them with oil. This gives them truly absurd water resistances and even improves the readability of the screen somehow.

“My phone needs an oil change”

“I dropped my phone and all the oil leaked out making a mess”

Yeah that’s not going to happen my dude.

Thermal concerns perhaps - how does epoxy dissipate heat?

Some types of epoxy actually conduct heat quite well.

I don't need any extra grams in my phone!

Shhhh - don't give Apple ideas.

That would be a problem for the mic and speaker, and has relatively few use cases.

Imagine how much drama they could have avoided if they filled the entire submersible.

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