A question of mechanical philosophy

I repair computers for a living. This includes laptop computers. Therefore, I disassemble a lot of laptop computers.

The first step in disassembling most laptops is to remove the keyboard. (Or, to remove a small piece of plastic and then remove the keyboard.)

When the keyboard is removed, this then reveals the heat sink.

The heat sink is a piece of metal who's job is to get warmed up by the CPU chip. (Depending on the design, the heat may then be conducted to a heat pipe, or to some fins which a fan blows air over, or just somewhere else. But the first part in the chain is always a chunk of metal against the CPU chip.

This piece of metal must he held in very close contact with the CPU (so that heat can easily travel to the metal chunk.)

Typically, this heat sink is held in contact with the CPU by four screws. (Often the screws actually compress four springs, and the springs hold the heat sink against the CPU. Such screws have a "shoulder" on then, so that they can only be tightened so far, and no further.)

Often, the four screws are numbered, 1 through 4, by numbers stamped into the metal of the heat sink.

Now, at this point in the disassembly of the laptop, I'm always struck by a question. It's not mentioned in the service manual. There doesn't seem to be anybody I can ask the question to who I'd trust the answer I got. (I could call the special, super-duper, tech support line for people who are factory authorized technicians, but frankly, the folks in India wouldn't have this question on their script, know considerably less about laptop computers than I do, have likely never actually disassembled a single laptop, and likely don't speak enough English to even understand the question.)

So I figured I'd ask ExtremeSkins.

I don't think it's likely that I'll put a lot of faith in the answer I get, here, either (but I'll admit that there's a chance). But I do figure that

1. The people on ExtremeSkins will speak English.
   
2. Their answers, while they may not be technically accurate, might be funny.
   

So, my question, concerning the four screws, numbered 1-4, which hold the heat sink to the CPU, is:

Is 1-4 the order that the screws go in, or the order they come out?

4-1, inverse order

However a call to super duper tech line is called for,the resulting rise in blood pressure is almost as healthy as throwing things against the wall for exercise. :cool:

How may I help you? :redpunch: :shot: :chug: :finger:

Is 1-4 the order that the screws go in, or the order they come out?

Yes.

They had to be put in before they could come out. So if your forced to make a decision based on so little info that's as good a indication as any.

They had to be put in before they could come out.

I thought of that, but I also suspect that they're put in by a robot. (Although, it could be a "third world robot".)

We shouldn't be numbering the screws, it might hurt there fragile emotional systems. Rename them all screw 1 so that they are filled with self-esteem and hand them all a ribbon certifying they are extra special screws.

The screws come out in descending order: 4,3,2,1. And they go back in in ascending order: 1,2,3,4.

Here's a link from a guy who also takes them out 4,3,2,1.

Intuitively, it makes the most sense that the numbers are ordered to aid assembly. Every laptop is guaranteed to be put together at least once, but might never have to be taken apart -- so there's no point in forcing assembly in an unintuitive order just to make it intuitive for a potential disassembly.

Are you sure it's the order that they're installed? Are the screws the exact same size? Could the screws be numbered not for the purpose of installation but to go into a particular hole?

On main bolts on an automotive crank they're numbered to go back into the right hole but they're tightened in a different pattern completely. That's why I ask.

That thought crossed my mind. But I saw other guides out there that called out the sizes of the screws, and they all appeared to be identical.

I'm not sure why you'd have a need for different screw sizes in this situation, but then again I'm not a laptop heat sink designer guy.

Actually, it's 4, then 1, then 3, then 2 for removal and then reverse the procedure to do it backwards.

Are you sure it's the order that they're installed? Are the screws the exact same size? Could the screws be numbered not for the purpose of installation but to go into a particular hole?

That thought crossed my mind. But I saw other guides out there that called out the sizes of the screws, and they all appeared to be identical.

I'm not sure why you'd have a need for different screw sizes in this situation, but then again I'm not a laptop heat sink designer guy.

In the link that you gave the pic showed that the numbers are on the heatsink not the screws, so it's order and location (according to him)

"The screws are each numbered, remove the screws in order from 4,3,2, to 1. The numbers are usually etched into the ceramic heatsink."

and btw, I agree with the order 1-4 during assembly but I'd bet that it wouldn't make a difference and Larry is much more anal than I previously thought.:laugh:

In the link that you gave the pic showed that the numbers are on the heatsink not the screws, so it's order and location (according to him)

"The screws are each numbered, remove the screws in order from 4,3,2, to 1. The numbers are usually etched into the ceramic heatsink."

and btw, I agree with the order 1-4 during assembly but I'd bet that it wouldn't make a difference and Larry is much more anal than I previously thought.:laugh:

In the very small number of times when I've disassembled a laptop heatsink or seen someone else do it, those screws themselves were never numbered. So the assembly order was easy by looking at the heatsink's numbers, but the location would have been a challenge unless you tracked the screw locations separately. Anyway...

In situations like this, even though it doesn't seem terribly important, it's usually best to remember the location and order and replicate them during reassembly. Just in case. If that's too detail-oriented, then oh well. I agree that location probably doesn't matter, unless you want to capture the unique physical match between screw and hole (like pistons in an engine, where it's far more important). But at least you can rule out improperly located screws later, if your reassembled laptop fails to work.

Oh, and also I'd like to remind everyone that Dallas sucks, at least in principle. Thank you.

Oh, and also I'd like to remind everyone that Dallas sucks, at least in principle. Thank you.

It's really comforting to know that rocket scientists have a sense of humor. Exactly why? I don't know.

Rocket scientist? Me?!?

I don't even believe in the Space Shuttle!

We shouldn't be numbering the screws, it might hurt there fragile emotional systems. Rename them all screw 1 so that they are filled with self-esteem and hand them all a ribbon certifying they are extra special screws.

And we should let them all play screwy sports like AYSO (American Youth Screw Organization) Soccer. We won't keep score, and no matter how bad any of the little screws screw up, we'll give them a trophy.

:laugh:

And we should let them all play screwy sports like AYSO (American Youth Screw Organization) Soccer. We won't keep score, and no matter how bad any of the little screws screw up, we'll give them a trophy.

:laugh:

:laugh: To steal your line from another thread...screw you guys! :rotflmao:

Rocket scientist? Me?!?

I don't even believe in the Space Shuttle!

Me neither, even though I saw the moon landing live in '69, it was all a fake. Check it out it's a holywood set with lots of styrofoam, a cardboard flag, the "astronauts" had springs on their feet and the footage was in slow motion. The Russians believed it so that's all that matters.

Tell me about it. And these days, the Space Shuttle's main engines are supposed to run on tap water.

WATER.

Gimme a break. As I sit here posting this, apparently I'm drinking a tall glass of rocket fuel.

Hoax Alert!

Tell me about it. And these days, the Space Shuttle's main engines are supposed to run on tap water.

WATER.

Gimme a break. As I sit here posting this, apparently I'm drinking a tall glass of rocket fuel.

Hoax Alert!

Tell me about it. And these days, the Space Shuttle's main engines are supposed to run on tap water.

WATER.

Gimme a break. As I sit here posting this, apparently I'm drinking a tall glass of rocket fuel.

Hoax Alert!

Actually, I think most of the thrust comes from rust.

Tell me about it. And these days, the Space Shuttle's main engines are supposed to run on tap water.

WATER.

Gimme a break. As I sit here posting this, apparently I'm drinking a tall glass of rocket fuel.

Hoax Alert!

I thought the Shuttle ran on dihydrogen monoxide?

I thought the Shuttle ran on dihydrogen monoxide?

i thought it ran on hydrogen and oxygen and that dihydrogen monoxide was the resultant exhaust.

I don't know about laptop computers, but I know in many mechanical applications the order has more to do with the tightening pattern producing the desired end result. So I might venture that dissassembly order is possibly irrelevant, and reassembly order of 1-4 starting in the right spot, produces the right tightening effect for the best contact for the heat sink surface in the end. If there is a fan, it may also have to do with how the screws tend to loosen from the fan vibrations, or from heat contraction and expansion of the pieces. That is just a guess based on other mechanical procedures that are common throughout many industries. That is all assuming the screw are all exactly the same.

Good point. I just looked more closely at the pattern of the numbers and they always seem to go diagonally across the heat sink, instead of clockwise or counterclockwise.

Of course, the quality of contact between the heat sink and processor is key to dissipating heat. So some endeavoring engineers determined that the internal stress pattern and final quality of contact between the surfaces is ideal when the screws are tightened in that order -- particularly given the range of temperatures and the corresponding expansion/contraction that occur across those components.

The springs also are probably not just useful, but essential to keeping the surfaces flush and in strong contact after a few hundred heating/cooling cycles. Installing the screws in diagonal order offers an additional assurance that the stress states the surfaces pass through during installation (and the corresponding tightening/relaxation of the screws that have already been installed) won't cause an inferior level of contact when installation is complete, hampering heat flux across that boundary.

Or to put it another way, you tighten them like the lugnuts on a car wheel, across the wheel instead of in a circle, so the thing is on there good 'n tight.

i thought it ran on hydrogen and oxygen and that dihydrogen monoxide was the resultant exhaust.

I'm gonna start a website to reduce dihydrogen monoxide emissions. I think that **** is the REAL danger facing the planet.

I know the more dihydrogen monoxide a hurricane has in it, the more dangerous it is. Jus' sayin'.