Light DIY on my 1240 accelerator

[mikeymike]

I mentioned a while back (on which thread I'm not sure) that the heatsink/fan had come off of the CPU on my 1240 accelerator card.  I believe a hot glue gun was advised as part of the solution.  I checked the temperature that it works on, it brings the glue up to at least 120C, so I seriously doubt that the processor is going to do the same, unless the processor is planning on melting too

My plan is to use a bit of thermal compound that I have for x86 CPUs on the centre underside of the HSF, give it a small bit of squelching around on the CPU, bearing in mind that it has to be in a particular position in order to fit in the trapdoor, then use the hot glue gun I recently bought to place blobs on three out of four sides (I believe one side would be sticking to the RAM if I did that) of the HSF.

Thoughts?

I suppose one other precaution I should take is to use a pencil to mark the boundaries of the ideal position of the HSF.

[Tension]

using a glue gun is a seriously bad idea

[tone007]

Maybe a combination of heatsink paste and that double-sided "heatsink" tape?  Though keeping the two from mixing could be a trick.

[ddniUK]

I have used glue guns with great success...

[Daedalus]

It's very, very important that whatever you do to secure the heatsink applies pressure to it so that it sits firmly and evenly on the surface of the chip. Heatsink paste/thermal compound isn't made to fill in any gaps other than the tiny grain you get on flat surfaces. The hot glue on the corners might be ok but it won't put any pressure on the heatsink, and therefore could easily let it move a small amount from the chip over time, or if it got a jolt or something. I'd be pretty wary of it!

[cv643d]

LOL it does look professionall though

But seriously, glue gun for the heatsink? Come on...

[mikeymike]

I intend to have the trapdoor closed (it's the trapdoor sent with the 1240, so it has a hole for the fan to blow air through), so wouldn't that provide the pressure you describe?

People have said that a glue gun for this job is a bad idea, but haven't said why, apart from the point about applying pressure, which hopefully is addressed by the custom trapdoor (which doesn't expose the whole HSF, just the fan).

[Daedalus]

I intend to have the trapdoor closed (it's the trapdoor sent with the 1240, so it has a hole for the fan to blow air through), so wouldn't that provide the pressure you describe?

People have said that a glue gun for this job is a bad idea, but haven't said why, apart from the point about applying pressure, which hopefully is addressed by the custom trapdoor (which doesn't expose the whole HSF, just the fan).

I think people's main concern is the initial thought that the glue is being used *between* the CPU and heatsink, which is would be worse than having no heatsink at all. The thing is, like I said, that the glue itself is soft and easily deformed once in place, moreso because the heatsink will get hot, and any movement off flat at all can be catastrophic for a hot processor. The 040, while hot, can probably tolerate a bit of abuse, but even so... I guess if the trapdoor applies enough pressure _evenly_ it should be fine, but you'd want to be sure it can't creep away from the CPU on one side, and that the board itself is flat and supported from behind.

I'm reminded of a time when I used to sell PC components over the counter in an electronics store. We had one guy return a motherboard/CPU combo for a refund, claiming it only worked for a few seconds. A quick examination found that he had put the heatsink on with a piece of self-adhesive foam padding, right over the heatsink contact surface on an Athlon XP chip... An excellent insulator! Needless to say he didn't get the refund as the CPU was working fine until he cooked it!

[Karlos]

Oddly enough, no 040 I have owned has ever gotten that hot. I remember touching the completely heatsinkless 040 on my BPPC and noticing that it was fairly warm but not hot.

Nevertheless, I attached a heatsink, just to be on the safe side.

[ddniUK]

@Karlos, yes this is true. My 040 chips got very warm but not HOT.
My reason for a heatsink on an Apollo 040 is that the CPU faces up into the A1200 desktop case and as such gets very little airflow.

[Daedalus]

Interesting... I've never owned an 040 board so I don't know how hot they get, but I thought they got almost too hot to touch. Maybe some revisions are hotter? It doesn't do any harm anyway to have a heatsink in such situations...

[mikeymike]

I think people's main concern is the initial thought that the glue is being used *between* the CPU and heatsink

Er, no

I planned to put a small bit of thermal compound (I was thinking about the size of a cooked grain of rice) in the centre underside of the HSF, then put it in the right place, then use the hot glue gun to put small blobs on each corner of the HSF, not so much that it goes under the HSF but beside it and on the CPU.

A couple of pics of the accelerator card:
http://lorien.legolas.com/040%20HSF%20off.jpg
http://lorien.legolas.com/040%20HSF%20on.jpg

Re: heat from 68040 - the HSF gets hand-hot after cooling the processor for a while (half an hour?).  I would guess its temp as 40 - 50C.

[pyrre]

IMHO thermal glue is the only valid option for adding heatsiks to a cpu without having clips or sockets...

[Damion]

Personally I would use a dab of good thermal compound in the center, then a small amount of thermal glue in two (or more) of the corners. Add a small weight (like a paperback) on the heatsink while the glue dries.

[rkauer]

About the '040 heat: only the last revision 040 is almost cold to touch (MC68040RCxx). Notice those are hard to see in the wild and highly desirable.

 Not-so-good old XC '040 really needs heatsinks and fans, specially the 25Mhz ones (dunno why).