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Comment by digitalsushi | Hacker News Reader

There is an alternate universe where every time he took his computer apart, he skipped the reflow heat stuff and just put it back together... and it worked identically for identical periods of time between failures. I'm not saying it's this universe, I'm just saying there is one out there.

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Are you in my living room?

A few months ago I disassembled and cleaned a grape juice damaged MBP. Tried it afterward and no dice. Tried it yesterday on a bored whim and I now have a working MBP with a sticky keyboard. Why? I have no idea.

Most of the actual logic board is sealed. So unless you spill something corrosive that goes through that seal and damages the logic board liquid can only get to and damage[0] actual connectors between components and physically moving entities. In case of MBP physically moving entities are mostly fans and keyboard.

My guess would be that grape juice shorted some of those connectors. After few months it dried sufficiently, such that when you reseated them short went away.

[0] And by damage I mean mostly short and/or corrode the metal.

Heh. I caught in the rain with my MacBook Air, and it worked fine for a day, but then wouldn't boot up at all and wouldn't hold charge. Three weeks later and rice and all that jazz and nothing. A couple months later, the charger showed a light, but it wouldn't boot and never lit up green.

Six months from the first incident, and I randomly plugged it in and it booted instantly - I was ecstatic. It lasted two weeks before it wouldn't boot up again. A week later, it booted up again, and has been fine ever since.

Beats me man. Apple "Geniuses" wouldn't touch it and wanted me to buy a new one.

Again, this was likely due to the minerals in the water causing a short, and after a long period of time, the mineral "bridges" broke/wore-away, resolving the short, and allowing your macbook to boot.

Regarding the "Apple Geniuses", I doubt there would of been anything they could do for you, other than sit there with a cuetip and attempt to wipe down your entire mainboard after a full disassembly. Not to mention water damage probably isn't covered...

That sounds plausible, though I thought any power running through it would've caused it to burn out. I was actually going to do a full disassembly with a mate of mine who was an EE, but never got round to it. We attempted to do it with my iPhone (which was dunked into a toilet in an unrelated incident), but even cleaning everything with isopropyl alcohol it wouldn't work. I didn't hold high hopes for the MacBook.

And no, water damage wasn't covered by warranty, but it was out of warranty anyhow. I just didn't want to pay another $2K for a MacBook Air (maxed out specs at the time).

Would you have preferred they tell you to leave it alone for a couple of months and maybe it would work again?

How about attempting to fix the issue instead of confirming what I already knew and telling me to buy a new computer? That's what technicians are supposed to do.

They did the same to me, when I dropped my first iPad and cracked the screen. They looked at it, and said "We'll sell you a new one at half price". Oh thanks, not even going to pretend to try to fix it?

But I did buy the new one and let them have the cracked one.

Sounds pretty great, actually. On these modern devices where the LCD is bonded to the glass screen, replacing the screen can cost as much as the device itself.

As a rule of thumb never take a thing to be repaired by someone who's main business is selling new versions of that thing.

Car dealers make more money from servicing cars than selling new cars, though.

Unfortunately rice is mostly placebo. It's something to give your brain a reason to leave the device alone for a while.

Use an actual dessicant. Which might also not work, but then your problem is less likely leftover wetness.

Rice does certainly work as a mild desiccant. Admittedly it is not a terribly effective desiccant, but it still has those properties.

One weird trick I remember from alt.hackers was using WD-40 to remove the water from soaked electronics, and then using high-purity isopropyl(?) alcohol to clean off the WD-40. (You'd want to remove the WD-40 since it would attract dust.)

That's interesting, I'd think you'd just use rubbing alcohol (isopropyl) of >95%, since it will evaporate very rapidly by itself, taking any moisture with it. It also has great cleaning properties by itself (often used to eat the thermal paste gunk off heatsinks). Isopropyl alcohol is what "Swimmers Ear Drops" are mostly made of (for when you get water stuck in your ear).

If it's not water (coffee etc) shower the motherboard with no battery the wash it with distilled water let it dry.

And that works :)

Butane works well too, as long as you don't spray too much and cause condensation.

I wondered that, too. I wonder whether he actually reflowed solder in the oven. Wikipedia gives a sample profile that heats to over 200 degrees Celsius for a minute or so. This uses around 170 degrees Celsius, which is used for preheating in the Wikipedia example. Also, a Google image search gives me reflow heats above 200 degrees for the 5 images I checked.

Also "The speed holes worked: The boot chime rang. The screen glowed. The fans blew." doesn't make sense to me. The extra holes may help and may even fix his problem, but I find it hard to believe that successful booting shows that. Yes, it is a 'little' early for a final verdict.

https://duckduckgo.com/?q=solder+aging

From what I know about heat treat ageing of metals something similar may be happening. Because he is pushing his system through above average temperature cycles, this causes microcrystalline changes in the solder. Ageing at even a temperature below reflow/melt temperatures can help restructure the grain.

If he didn't run his system at such a high temp and then eventually turn it off to cool so much then he might not have the problem to begin with. As a side note, personal experience building pcs for many years has shown me that pcs that sleep/get powered off don't last as long as ones that stay powered on 24/7.

Why do you doubt the temperature did not reflow the board?

When I solder electronics, I'm usually somewhere between 500F to 650F, but that's so things get hot enough quickly enough to not burn. I don't doubt a slow bake at 340F would do the same thing... some online googling shows people doing reflows with toaster ovens in the same temperature range (340F-450F).

It's likely the solder joints were not completely disconnected, but rather simply cracked. So heating them a bit would allow the crack to reconnect, at least for a short while (seems to explain his symptoms of repeated failures after extreme system temperatures during operation).

Is it not true that baking it makes any "cracking" in the soldering smooth out since this is similar to what is done to boards at the factory during construction?

Right. And the reason why it keeps breaking? Well, the solder on the board might not have any flux left, so it might have trouble flowing properly. There could be a cold joint, etc.

If it fails again, one possible next step would be to grab a multimeter and test the resistance across each component on the board. If the resistance is infinite, that might be your problem component.

There's more than resistors on logic board. Also, by even touching component leads with multimeter probes is sometimes enough to connect the joint back thus fooling you to think connection was ok.

Also, the problem might as well be one of the numerous chips in BGA packages whose connection points you can't even see, let alone- probe.

Don't you have to isolate components from the circuit to check resistance? Otherwise, you're looking also the other components look like the other arm(s) of a parallel circuit.

You know what, you're right. I saw a video of someone testing that a chip had been soldered on correctly with a multimeter, but he was testing for the lack of a connection. Testing for a connection would not be done this way.My bad.

physics, 340F will NOT melt solder

Got a source for that? According to Wikipedia, 340F is not far from the melting point for solder. Depending on the solder used, it may have melted, or just gotten soft enough to heal any gaps or cracks.

https://en.wikipedia.org/wiki/Solder#Lead-free_solder

The link you attached lists a few different lead-free solder alloys with the lowest melting at 412F(211C) well above 340F(171C). Eutectic tin/lead solder has a melting point of 361F(183C), also above 340F.

I'm not sure whether or not cracks can heal at temperatures below the melting point, but I would be surprised if that were possible.

So it turns out that home oven manufacturers don't care too much about precision when it comes to oven temperature (and it doesn't matter usually).

A high end home oven will easily swing between +- 25 degrees of the temperature that you have dialed in, and that's if it's well calibrated.

If he didn't dial in "340" quite right, and his oven was average, I can easily see it hitting temperatures of 412+, and that could also account for his varied results.

Not to mention we don't need the solder to completely melt, only soften (depending how badly cracked the joint(s) were).

If this were Mythbusters, we'd call it "Plausible".

It's possible that he did reflow the board. Consumer ovens usually reach 250C, slightly more when in autoclean mode. Lead-free reflow happens above 250C (normally 255-275C).

The whole procedure is wild, though, and I wouldn't recommend trying it out. He was lucky that the board didn't get destroyed. Most SMD components can withstand temperatures above 250C for tens of seconds, not necessarily for nine minutes.

But he writes "and turned the oven up to 340 F". That's about 170 Celsius. The oven probably isn't very precise, but I doubt that's in the 250 Celsius range.

As an anecdata point, mine says it goes to 300. I get 230-250. Bread likes it hot.

I'm guessing he put the board in and then started the oven which took a while to preheat. Industrial reflow heats up the board gradually based on the solder paste manufacturer's suggested heat profile or experimentation/trial and error (e.g. when dealing with small pitch BGAs). 250C for even a few minutes would do quite some damage even to the fire retardant laminate and smell horrible.

He stated he was using a temperature of 340F, which is roughly 170C. Would that temperature also be harmful to SMD components when exposed for several minutes?

Doubtful. As a reference point, typical guidelines for baking out moisture (prior to assembly) are 24 hours at 150C.

I can assure you that it does work. Not sure about 340f though.

I baked a Nvidia GTX470 at 390f for 10 minutes and it eliminated the artifacts/crashing and has been working fine for months.

It probably won't work forever, but it is at least a temporary fix.

I did an oven reflow on an RRoD Xbox motherboard years ago. Worked like a charm. I was a little worried about bursting the caps, but a little insulation and aluminum foil protection apparently kept them cool enough. Lasted for about a year.

I had the same thought after I reflowed the GPU from my iMac. It didn't work before, and it did work after, but it may simply be that dismounting and remounting the heat sink put enough pressure on the cracked solder ball to make it work again. I will never know, short of xray inspection, but it's been working fine for half a year now.

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