Technical Paper

Introduction of Thermal Interface Materials (TIMs) In Thermal Management Solution

Prepared by Ng Hooi Hooi.

Presented at BiTS Workshop (Poster Session) on March 5 – 8, 2017

What is Thermal Interface Material (TIM)?

TIM is a heat conductive material that is inserted in between two components (such as semiconductor devices and heat sink) to enhance the thermal coupling and heat flow by reducing or filling the air gaps.

When two surfaces are in contact, an air void will be formed due to roughness and unevenness of the contact surfaces. The air void is a very poor thermal conductor where it represents significant resistance to heat flow and it will decrease the efficacy of the heat transfer to the ambient environment.

 

Basic Type of TIMs

Thermal Grease

Advatanges

  • High thermal performance
  • Thinnest thermal join with minimal pressure
  • No delamination issue

Disadvantages

  • Difficult to apply/ remove
  • Excessive grease need to clean up after application
  • Grease join dry out with time, resulting thermal resistance increased

Phase Change Material (PCM)

Advantages

  • Easy handling and installation
  • No delamination issue
  • No curing required
  • Prevent leaking while maintain high thermal resistance

Disadvantages

  • Attachment pressure required (moderate contact pressure for rework ability)
  • Pre- heating treatment necessary

Gap Filler Pad

Advantages

  • Die-cut preforms in the precise shape needed for the application
  • Assembly is very simple

Disadvantages

  • High pressure are needed
  • Applications are limited to those with modest thermal requirements

Thermal Tape & Film

Advantages

  • No pump put or migration concern
  • No curing required

Disadvantages

  • Attachment pressure required
  • Thermal conductivity is moderate (can only match or be slightly better than a direct contact of heat sinks and component)
   Thermal Epoxy, Gel & Solder

Advantages

  • Thermal performance close to thermal grease
  • Provide more secure (or permanent) joint between the heat sinks and component.)

Disadvantages

  • Hard to use because of the curing or reflow processes
  • Difficult to rework
 

Metal Tims

Advantages

  • Easy to apply and remove
  • Mechanical compliance

Disadvantages

  • Attachment pressure required
  • Costly

 

Conclusion

This study highlighted how critically the TIM can be used to improve heat transfer efficiency in a thermal solution. TIM thermal performance is pressure sensitive. Compression force must be applied when TIM in used to obtain the best performance. It is important to understand function and target application for each type of TIM due to it’s different material characteristics and thermal properties. Thermal resistance is an important factor to determine how well the thermal stack up design is. By utilizing the TIM as part of the thermal solution, it is proven that it can help to address critical thermal issues in order to optimize device performance while provide long-term reliability performance.