[SOLVED] How are CPUs cooled underneath the IHS without shortcircuit

[WiseElf]

Hi!

I just read the following article about how CPUs are manufactured at the following link:

https://www.tomshardware.com/picturestory/514-intel-cpu-processor-core-i7.html

One part that got my attention is near the end of the article, it says that once the transistors are built, interconnects are created to form what will be the CPU architecture:

"Multiple metal layers are created to interconnects (think wires) in between the various transistors. How these connections have to be “wired” is determined by the architecture and design teams that develop the functionality of the respective processor (for example, Intel’s Core i7 processor). While computer chips look extremely flat, they may actually have over 20 layers to form complex circuitry.[..] "

What I understand is that afterward, once the CPU die is fully constructed, a gold/indium soldering is applied so heat can be transfered to the IHS. (and I hear that sometimes people delid their CPU and apply some liquid metal TIM) Since the transistors interconnects are made out of copper and the soldering is made out of gold/indium, how do Intel makes it so only heat is transfered and no short circuit occurs? The article did not mention anything about this, and I assume the soldering sits directly on the transistors interconnects?

Thanks!

 

[drea.drechsler]

@WiseElf : The top surface/layer of the CPU die, the surface that comes in contact with the metallic heat spreader, is a solid layer of electrically insulating silicon with no exposed circuits. The bottom surface/layer of the die has the interconnects to the substrate for I/O, power and ground.

 

[WiseElf]

@WiseElf : The top surface/layer of the CPU die, the surface that comes in contact with the metallic heat spreader, is a solid layer of electrically insulating silicon with no exposed circuits. The bottom surface/layer of the die has the interconnects to the substrate for I/O, power and ground.

So if we follow the steps of the article I quoted, is it true to say that after etching is performed and the copper interconnects are created, we have this final step where a protective silicon layer is applied on top of the die right before the soldering and IHS are applied? Thanks!

 

[drea.drechsler]

So if we follow the steps of the article I quoted, is it true to say that after etching is performed and the copper interconnects are created, we have this final step where a protective silicon layer is applied on top of the die right before the soldering and IHS are applied? Thanks!

As I understand it, the doping, electro-depositing, etching, copper interconnects and etc. are layered on top of the silicon wafer, the bottom surface receives none of these treatments and so remains bare. After being diced out of the wafer, the chip is 'flipped' over to mount on the substrate. What was the bottom...a bare silicon surface...is now on top.

 

[WiseElf]

As I understand it, the doping, electro-depositing, etching, copper interconnects and etc. are layered on top of the silicon wafer, the bottom surface receives none of these treatments and so remains bare. After being diced out of the wafer, the chip is 'flipped' over to mount on the substrate. What was the bottom...a bare silicon surface...is now on top.

oh ok thanks for the clarification! Re-reading your first post now and it's pretty obvious the die HAS to be flipped over and I just didn't catch on 😉