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Which factors will directly affect thermal pad thermal conductivity or performance 9/20/2017
 Thermal conductive pad is a natural sticky, high thermal conductivity, high insulation, high compression sheet type thermal interface material, which commonly used as gap filller in electronic products between the heat source and the radiator or rear shell. It's a ploymer material which used to conduct heat. Alumina is mainly thermal powder, and silica gel as the carrier, and then made by rolling machine through special process. Thermal pad has stable thermal conductivity and long life, simple assembly, wide range of thermal conductivity and thickness, which is widely accepted by many electronic products customers.

Which factors will directly affect thermal pad thermal conductivity or performance?

1: Thermal impedance 

In fact, there has been a kind of phenomenon in industry: Purchasers see thermal conductivity, while Engineers see thermal impedance. That means if customer is purchaser staff, they are most concerned about thermal conductivity; if customer is engineer staff or R&D personnel, they are more concerned about thermal pad thermal impedance. We can judge that thermal impedance is very important for conductivity.
Same thermal conductivity, same thickness of two different thermal pad, lower thermal impedance one has much better thermal conductivity performance than higher impedance one. Sometimes, low thermal conductvity, low thermal impedance thermal pad has better performance on heat conduct than high thermal conductivity, high thermal impedance thermal pad. The higher thermal impedance, the higher thermal resistance when heat conduct, and affect conductivity greatly. If very little resistance on heat conducting, it has better thermal conductivity. Thermal grease is the best example. We all know that thermal grease has good thermal conductivity, because it has much lower thermal impedance than thermal pad.

2: Thermal conductivity

Different thermal conductivity has different filling thermal powder, and different thermal formulations. Normally thermal pad conductivity below 3w/m-k is filled with alumina as thermal powder, while high conductivity thermal pad must add boron nitride powder inside to increase thermal conductivity. Boron nitride powder is much expensive than alumina, that's why high conductivity thermal pad is much expensive than normal thermal pad. Of course, same thickness, same thermal impedance, higher conductivity thermal pad working performance is much better than normal thermal pad.

3: Thermal pad hardness

Harder thermal pad gap filling ability is poor, which will add thermal impedance and affect thermal conductivity finally. Lower hardness thermal pad is a good gap filler which add effective contacting area of thermal pad and heat source or heatsink, and lowered thermal impedance and increased thermal conductivity. But, it doesn't mean lowest hardness is the best, because if too soft, it will easily deform when assembly and can not paste well. The larger size of thermal pad is more obvious. Common used hardness among 40-70 Shore 00.

4: Thermal pad thickness

Thermal pad has wide range of thickness, which can be made from 0.5mm to 15mm, the thinner thickness, the shorter path of heat conduct, thermal impedance is smaller and faster thermal conducting speed, so better thermal conductivity. In the contrary, the thicker thickness will increase thermal resistance and cause bad thermal conductive performace.