Heat sinks aren't just for stopping the expansion of metals, they are instrumental in whisking heat away from devices that are very sensitive to heat problems. Electronics are the best example. Processor chips in you
computer are very sensitive to heat. If they see too much heat, they will start to loose their number crunching abilities, so designers put heat sinks along with fans on the processor to whisk heat away. That is one reason you always hear a fan going when you turn you computer on.
Heat sinks are used for the purpose of preventing something from getting too hot. A typical example is an integrated circuit chip in a computer or a transistor.

Answered by Kajal , an ibibo Master, at 9:17 PM on March 18, 2008

the basics of heat transfer, and thermal resistance, how can we translate this into how a heatsink works?

Well lets overview the set up so far. We have a CPU or other heat generating component, and a block of metal with low thermal resistance. The problem now is how do we efficiently transfer this heat from the component to the heat sink?

The answer is thermal compound, or Thermal Interface Matrial (TIM). This is usually a paste like substance with VERY low thermal resistance, and is usually made with particles of silver. Silver has very low thermal resistance, hence why it is used in TIM's. Also, TIM is designed as a paste so that it fills in the microscopic imperfections (Or valleys) on the surface of the CPU and heatsink so that all of the surface of the CPU is thermally bonded (linked to in a way which allows heat to be transferred) to the base of the heatsink.

Our setup is almost complete. We have a Heat source (Component of some sort), the TIM, and the Heatsink. The dissipation (moving and removal) of heat from the component can now begin. The particles in the component vibrate, causing the particles in the TIM to vibrate. This i turn causes the particles in the heatsink to vibrate.
Thankfully, physics is on our side in this. As most of you will know, hot air is less dense than cold air, because the vibrating particles cause themselves to be spaced further apart (Because they essentially push their neighbouring particles away from them). Because of this, the hot air around or copper fins rises up and away from the heatsink (EG, a hot air balloon. The balloon is filled with hot air, and the balloon rises.) Due to air pressure, cold air from underneath is sucked up into the heatsink. Of course you won't actually notice this, as it is no where near the type of suction you would get from something like a FAN.

Which brings us onto or next point.

Answered by sujata , an ibibo Specialist, at 11:56 AM on March 18, 2008

Hi,
Step 1: Understanding what heat is

This is not as obvious a point as it may first seem. Heat is infact molecular vibrations in any substance. The hotter something is, the more the molecules/particles in that substance vibrate. Temperature is a measurement of these tiny vibrations. The more vigorous the vibrations, the higher the temperature. Because of the transfer of electrons within components inside computer chips, friction is generated and this energy causes the molecules within the component to vibrate (Friction itself is infact a form of heat generated by 2 or more particles rubbing together. EG. Rub you hands together for a few seconds and they will feel warmer. This is friction.)

Step 2: How heat is transferred

Heat is transferred because when a particle vibrates, it stimulates the particles beside it to vibrate. Think of this as holding a piece of rope at one end and shaking it. This causes the rope to shake a fair ammount down aswell depending on the resistance it encounters. EG if you wave it in the air, the rope will likely move all over. If the rope is on the ground, it will likely move alot less. Think of this as an example of particles stimulating neighbouring particles, which is heat transfer, and also as an example of thermal resistance, which is what makes some materials good at conducting heat, such as copper, and some materials bad at conducting heat, such as plastic.

Step 3: Thermally bonding the Heatsink and Component

Now we know the basics of heat transfer, and thermal resistance, how can we translate this into how a heatsink works?

Well lets overview the set up so far. We have a CPU or other heat generating component, and a block of metal with low thermal resistance. The problem now is how do we efficiently transfer this heat from the component to the heat sink?

The answer is thermal compound, or Thermal Interface Matrial (TIM). This is usually a paste like substance with VERY low thermal resistance, and is usually made with particles of silver. Silver has very low thermal resistance, hence why it is used in TIM's. Also, TIM is designed as a paste so that it fills in the microscopic imperfections (Or valleys) on the surface of the CPU and heatsink so that all of the surface of the CPU is thermally bonded (linked to in a way which allows heat to be transferred) to the base of the heatsink.

Our setup is almost complete. We have a Heat source (Component of some sort), the TIM, and the Heatsink. The dissipation (moving and removal) of heat from the component can now begin. The particles in the component vibrate, causing the particles in the TIM to vibrate. This i turn causes the particles in the heatsink to vibrate.

Step 4: But how does that make the CPU cooler? If more particles are vibrating, surely that means the component gets hotter?

Everytime a vibrating particle causes a neighbouring particle to vibrate, it transfers energy. We know that energy cannot be created from nothing, and in the case of a heatsink, the energy is generated from the power (Voltage and Current) being supplied to the component being cooled. When this energy is transferred, the particle which causes the neighbouring particle to vibrate loses energy. It vibrates less. Infact, this occurs to the point where the particle vibrates near enough as much as it neighbouring particle.

Within this theory lies the fundamentals to the Heatsinks operation. By spreading the heat accross a large piece of material, we can reduce the temperature of the component.

Step 5: Optimizing the heatsinks design

So we have a block of lets say copper thermally bonded to a heat producing component. How can we increase the efficiency of this block? Well for a while the block will work reasonably well (not nearly as good as todays heatsinks though) but there is a problem. Heat is only being spread accross the materials. Think of this exam

Answered by Khursheed , an ibibo Master, at 11:19 AM on March 18, 2008

Well Gurtel , To know the working of Heat sink you need to some basic terms and it is a lengty process too.

Step 1: Understanding what heat is :

This is not as obvious a point as it may first seem. Heat is infact molecular vibrations in any substance. The hotter something is, the more the molecules/particles in that substance vibrate. Temperature is a measurement of these tiny vibrations. The more vigorous the vibrations, the higher the temperature. Because of the transfer of electrons within components inside computer chips, friction is generated and this energy causes the molecules within the component to vibrate (Friction itself is in fact a form of heat generated by 2 or more particles rubbing together. EG. Rub you hands together for a few seconds and they will feel warmer. This is friction.)

Step 2: How heat is transferred :

Heat is transferred because when a particle vibrates, it stimulates the particles beside it to vibrate. Think of this as holding a piece of rope at one end and shaking it. This causes the rope to shake a fair amount down as well depending on the resistance it encounters. EG if you wave it in the air, the rope will likely move all over. If the rope is on the ground, it will likely move alot less. Think of this as an example of particles stimulating neighbouring particles, which is heat transfer, and also as an example of thermal resistance, which is what makes some materials good at conducting heat, such as copper, and some materials bad at conducting heat, such as plastic.

Step 3: Thermally bonding the Heatsink and Component
Well lets overview the set up so far. We have a CPU or other heat generating component, and a block of metal with low thermal resistance. The problem now is how do we efficiently transfer this heat from the component to the heat sink?

The answer is thermal compound, or Thermal Interface Matrial (TIM). This is usually a paste like substance with VERY low thermal resistance, and is usually made with particles of silver. Silver has very low thermal resistance, hence why it is used in TIM's. Also, TIM is designed as a paste so that it fills in the microscopic imperfections (Or valleys) on the surface of the CPU and heatsink so that all of the surface of the CPU is thermally bonded (linked to in a way which allows heat to be transferred) to the base of the heatsink.

Our setup is almost complete. We have a Heat source (Component of some sort), the TIM, and the Heatsink. The dissipation (moving and removal) of heat from the component can now begin. The particles in the component vibrate, causing the particles in the TIM to vibrate. This i turn causes the particles in the heatsink to vibrate.

Step 4: But how does that make the CPU cooler? If more particles are vibrating, surely that means the component gets hotter?

Everytime a vibrating particle causes a neighbouring particle to vibrate, it transfers energy. We know that energy cannot be created from nothing, and in the case of a heatsink, the energy is generated from the power (Voltage and Current) being supplied to the component being cooled. When this energy is transferred, the particle which causes the neighbouring particle to vibrate loses energy. It vibrates less. Infact, this occurs to the point where the particle vibrates near enough as much as it neighbouring particle.

Within this theory lies the fundamentals to the Heatsinks operation. By spreading the heat accross a large piece of material, we can reduce the temperature of the component.

Step 5: Optimizing the heatsinks design

So we have a block of lets say copper thermally bonded to a heat producing component. How can we increase the efficiency of this block? Well for a while the block will work reasonably well (not nearly as good as todays heatsinks though) but there is a problem. Heat is only being spread accross the materials. Think of this example. You are butter

Answered by alokgupta14 , an ibibo Guru, at 11:01 AM on March 18, 2008