Present and future thermal interface materials for ...

1 Full Terms & Conditions of access and use can be found by: [ ]Date: 01 June 2017, At: 08:26 International materials ReviewsISSN: 0950-6608 (Print) 1743-2804 (Online) Journal homepage: and future thermal interface materials forelectronic devicesKafil M. Razeeb, Eric Dalton, Graham Lawerence William Cross & AnthonyJames RobinsonTo cite this article: Kafil M. Razeeb, Eric Dalton, Graham Lawerence William Cross & AnthonyJames Robinson (2017): Present and future thermal interface materials for electronic devices ,International materials Reviews, DOI: link to this article: online: 27 Mar your article to this journal Article views: 93 View related articles View Crossmark dataPresent and future thermal interface materials for electronic devicesKafil M.

2 Razeeba, Eric Daltonb, Graham Lawerence William Crosscand Anthony James Robinsond,eaTyndall National Institute, University College Cork, Cork, Ireland;bStokes Laboratories, University of Limerick, Limerick, Ireland;cSchool ofPhysics, CRANN nanotechnology Institute, Trinity College Dublin, Dublin 2, Ireland;dDepartment of Mechanical & ManufacturingEngineering, Trinity College Dublin, Dublin 2, Ireland;eCONNECT, Dunlop Oriel House, Trinity College, Dublin, IrelandABSTRACTP ackaging electronic devices is a growing challenge as device performance and power levelsescalate. As device feature sizes decrease, ensuring reliable operation becomes a effective heat transfer from an integrated circuit and its heat spreader to a heatsink is a vital step in meeting this challenge.

3 The projected power density and junction-to-ambient thermal resistance for high-performance chips at the 14 nm generation are >100 Wcm 2and < CW 1, respectively. The main bottleneck in reducing the net thermalresistance are the thermal resistances of the thermal interface material (TIM). This reviewevaluates the current state of the art of TIMs. Here, the theory of thermal surface interactionwill be addressed and the practicalities of the measurement techniques and the reliability ofTIMs will be discussed. Furthermore, the next generation of TIMs will be discussed in termsof potential thermal solutions in the realisation of Internet of HISTORYR eceived 3 August 2016 Accepted 14 February 2017 KEYWORDST hermal interface materials ;solder; carbon structure;polymer composite; thermalconductivity; thermalresistanceIntroductionThermal interface material or TIM can be defined asany material that is applied between the interfaces oftwo components to enhance the thermal couplingbetween these devices .

4 Usually, TIM is used betweena heat generating device ( microprocessor, photonicintegrated circuits, etc.) and a heat dissipating device( heat sink) to remove the heat from the com-ponent. The effective transfer/removal of heat from asemiconductor device is crucial to ensure reliable oper-ation and to enhance the lifetime of these surface roughness and non-planarity ofthe IC/heat spreader and heat sink surfaces result inasperities between the two mating surfaces. These aspe-rities prevent the two solid surfaces from forming athermally perfect contact due to the poor thermal con-ductivity of air that exists in the gaps between two mat-ing surfaces [1]. TIMs are therefore used to provide aneffective heat conduction path between the solid sur-faces due to their conformation (under pressure) tosurface roughness and reasonably high thermal con-ductivity [2].

5 There are different types of TIMs available bothcommercially as well as in the research and develop-ment phase. From an application point of view, thecommercially available TIMs are usually based ondifferent types of filler materials in a polymer matrixor are solder based. In recent years carbon-basedTIMs have also been widely investigated. Broadlyspeaking, these materials can be divided into threedifferent classes: Carbon-based, metal/solder and fil-ler-based TIMs. These again can be divided into solder,alloys, metallic foils, different types of carbon struc-tures (carbon nanotube, graphene, graphite, etc.) andpolymer (grease, phase change materials , adhesives,elastomer, and thermoplastic, etc.)

6 Based the best of our knowledge, a comprehensivereview on TIMs is still missing (except the recentcomplementary review by Hansson et al. [3]), wherethe last review was done in 2013 on Reliability of ther-mal interface materials [4] and in 2012 on Character-ization of nanostructured thermal interface materials A review [5]. Thereby, it is envisage that a thoroughreview on this topical area would benefit new research-ers in this area as well as application engineers who arelooking for the right TIMs for their specific is intended that this review will cover the last decadeor so of research in the area with particular focus onrecent trends and technologies. This review is dividedinto the following section: TIM market, Theoreticalconcept of TIMs and associated phenomena, measur-ing thermal performance of TIM, different types ofTIMs and concludes with a summary and outlook.

7 Itis hoped that this review will enhance the understand-ing of the Present status of TIM technology and helpresearchers and practitioners understand the gapsand opportunities which will allow them to directtheir future research and development to meet therequirements of thermal management of next-gener-ation electronic and photonic devices . 2017 Institute of materials , Minerals and Mining and ASM International Published by Taylor & Francis on behalf of the Institute and ASM InternationalCONTACTK afil M. National Institute, University College Cork, Dyke Parade, Lee Maltings, Cork T12 R5CP,IrelandINTERNATIONAL materials REVIEWS, 2017 marketFuture electronics and photonics systems will faceoverheating problems associated with excess heat aslong as these systems are not monolithic, but arebuilt using different materials , semiconductors,metals, ceramics and polymers.

8 In the vision of theInternet of Things, the rise in power densities due tominiaturisation in electronic and photonics systemswill make effective heat removal a critical issue forthe progress in communication, information, energyharvesting and lighting technologies. The fundamentalproblem will be the reduced performance, reliabilityand lifetime of these electronic devices due to excessheat, which cannot be removed without implementingan effective thermal path between heat generatingdevice ( microprocessor) and the heat removingcomponent such as heat sink. Therefore, the require-ment of effective thermal interface materials within stacked electronics packages is vital to ensure reliableand safe TIM market is now continuously monitored bymajor market research firms such as BCC Research inMassachusetts, USA [6] and IDTechEx of London, UK[7].

9 While the detailed market information is proprie-tary, major trends are provided in free executive sum-maries [8 10], from which we summarise a fewhighlights interface materials are embedded in theoverall thermal management industry consisting ofheat spreaders, heat pipes, substrates and control sys-tems estimated at over US$11B today and expectedto grow to US$16B by 2020. Due to historical chal-lenges of understanding and engineering interfaces,maturing of thermal management technology in thelast decade has been uneven, and has placed the TIMin the position of an increasing bottleneck in the overallcooling solution. This is reflected in future growthexpectations, where higher growth in the TIM sectoris predicted in the next 10 years.

10 The TIM market isdefined by the spectrum of products discussed in thisreview including polymer and polymer composite-based gels, greases, pads, and adhesives, variousmetal-based films, phase change materials , as well asemerging technologies such as carbon-based TIMs dominate with over 80% of themarket today, with the rest forming a small but morerapidly growing set of emerging solutions. Dependingon the extent of inclusion of multi-purpose joiningmaterials such as adhesive tapes, estimates of the mar-ket size range from US$750M to US$ worldwide in2015. There is further general agreement on 7 8%average annual growth leading to a US$ 2B sizemarket by are used in a multitude of industrial sectorsidentified as computers, consumer devices , telecom-munication infrastructure, LED lighting products,renewable energy, automotive, military/industrialequipment, and medical equipment.