Epiphany-III chip airgap / heat-spreader height differences!

Hardware related problems and workarounds

Epiphany-III chip airgap / heat-spreader height differences!

Postby deviantlamb » Mon Sep 29, 2014 5:49 am

Okay so shortly after receiving my board, imaging up a usb and successfully ssh'n into the unit I was amazed at the heat the chip was reporting back. so amazed I immediately halted, inspected the TDP and likewise specks closer and went off and got myself a more suitable heat sink. see here if your keen: alphanovatech > http://goo.gl/t7dB2H

So long story short here are some photos, static wise i'm earthed by an ankle strap to the bare metal of a fridge foot. :lol:
Now that I am aware that there is uneven/ziltch/no heatsink contact on the hotter chip I will need to get myself a copper spreader of the ideal thickness to equal this out. Do all owners of this board know that they are potentially looking at running a bare chip? have you checked yours? for those that this is ooold news, how did you solve this issue?Again for those that don't, go check yours!

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That last pic: [topic] that damn air-gap/height difference :(
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Re: Epiphany-III chip airgap / heat-spreader height differen

Postby deviantlamb » Tue Sep 30, 2014 7:47 am

:!: updated to actually show the images
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Re: Epiphany-III chip airgap / heat-spreader height differen

Postby greytery » Tue Sep 30, 2014 11:09 am

Nice (alternative) sink!

I upgraded to a 4-way cluster by adding a pair of the later 7010 headless microservers with the newer slab sink.
So I also noticed the air gap above the Epiphany. That's the cooler chip BTW, but I agree that it's a bit scary.

However, I'm using diamonds instead of the adhesive tabs. I applied a slightly more generous amount of the paste to the Epiphany than to the Zynq - so no visible gap.

Note: the paste is very thick - warm it under your armpit for a while to make it easier to apply. Your climate and body temperature may vary.

Cheers
tery
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Re: Epiphany-III chip airgap / heat-spreader height differen

Postby AndyC » Tue Sep 30, 2014 2:50 pm

Hi Deviant lamb,

I had a look at mine and as far as I can see the pads supplied with my heatsink are in contact ok with both chips.

As Greytery says though it is the zynq that gets very hot, for mine there is no way even with the large heatsink provided that you can run it without a fan.

I'm running a 12V 6cm fan at 5V attached to the top of the heatsink pulling air through the heatsink, this keeps mine at 55-57C. Just incase something goes wrong I also have a daemon running monitoring the temp that sends messages to the console incase it gets too hot. Unfortunately there is no way to power down the board from software if this happens.

Cheers

Andy
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Re: Epiphany-III chip airgap / heat-spreader height differen

Postby deviantlamb » Wed Oct 01, 2014 2:39 am

greytery wrote:Nice (alternative) sink!

Thanks, it should be reasonably over effective than necessary.
greytery wrote: warm it under your armpit for a while to make it easier to apply

Its those beautiful tips that you never find on wiki's :D

Greytery, I was going to grab a 0.5mm thermal pad and buff the gap but might just go the paste path. I'm aware its the cooler chip but still a tad puzzled why its been mounted at a varying height to its neighbor. I have 3 more boards on route with matching sinks. I do intend to mount these vertically in a case (when I can source acrylic in Aus that isn't overblown cost wise) for that part, how are you maintaining reasonable contact/pressure between the chip and sink?

Cheers for your great reply(s)
Last edited by deviantlamb on Wed Oct 01, 2014 2:47 am, edited 1 time in total.
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Re: Epiphany-III chip airgap / heat-spreader height differen

Postby deviantlamb » Wed Oct 01, 2014 2:45 am

AndyC,

Yea a service I started to poll chip temperatures alerted me to the initial high temps at idle. I have since modified the thresholds to suit spec. I will get around to making it send me notifications via mutt or a LAN message service at some point. (I might pastebin my handiwork)

Cheers.
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Re: Epiphany-III chip airgap / heat-spreader height differen

Postby greytery » Wed Oct 01, 2014 8:57 pm

deviantlamb wrote:I'm aware its the cooler chip but still a tad puzzled why its been mounted at a varying height to its neighbor.

Different packaging material of the chips - always something to look out for.
I note that the HDMI chip is slightly taller than the Zynq - but the thermal pad on the Zynq should even it out. Nevertheless, there is then no airflow over the HDMI chip - and no way to check the temp of the chip - so another small dab of diamonds there might help. (Note I don't have that problem on my large sink/micro-server/headless boards, so that is just a comment and something I can't verify).
deviantlamb wrote:I have 3 more boards on route with matching sinks. I do intend to mount these vertically in a case (when I can source acrylic in Aus that isn't overblown cost wise) for that part,

Even though I see Adapteva's advice that a singleton Parallella should be mounted vertically, I believe you will still get better temp reduction with a fan. In which case, note the other examples over on the Show'n tell thread and go with the (air) flow. Get the xtemp utility loaded as soon as you can.
I need a new case too - now that I have 4 boards. My son just showed me his new toy - a laser cutter bed. We're in negotiations about what I can get him to do with acrylic off-cuts ;) . You might take a look at the abopen cluster case, at least for ideas. Your postage may vary.
deviantlamb wrote:..how are you maintaining reasonable contact/pressure between the chip and sink?

I have an A'Level in Physics, Cap'n. Gravity and viscosity. I mount them horizontally - but with a 8cm fan. And I don't touch!! The paste is sticky enough to hold the sinks in place. If you were in NZ you'd be concerned with tremors, but in Aus (Oz?) or Aus (tria?) you should get away with it.

Cheers
tery
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