Thermal interface materials (TIMs) play a vital role in the performance of electronic packages by enabling improved heat dissipation. These materials typically have high thermal conductivity and are designed to offer a lower thermal resistance path for efficient heat transfer. For some semiconductor components, thermal solutions are attached directly to the bare silicon die using TIM materials, while other components use an integrated heat spreader (IHS) attached on top of the die(s) and the thermal solution attached on top of the IHS. For cases with an IHS, two TIM materials are used—TIM1 is applied between the silicon die and IHS and TIM2 is used between IHS and thermal solution. TIM materials are usually comprised of a polymer matrix with thermally conductive fillers such as silica, aluminum, alumina, boron nitride, zinc oxide, etc. The polymer matrix wets the contact surface to lower the contact resistance, while the fillers help reduce the bulk resistance by increasing the bulk thermal conductivity. TIM thickness varies by application but is typically between 25 μm and around 250 μm. Selection of appropriate TIM1 and TIM2 materials is necessary for the reliable thermal performance of a product over its life and end-use conditions. It has been observed that during reliability testing, TIM materials are prone to degradation which in turn leads to a reduction in the thermal performance of the product. Typical material degradation is in the form of hardening, compression set, interfacial delamination, voiding, or excessive bleed-out. Therefore, in order to identify viable TIM materials, characterization of the thermomechanical behavior of these materials becomes important. However, developing effective metrologies for TIM characterization is difficult for two reasons: TIM materials are very soft, and the sample thickness is very small. Therefore, a well-designed test setup and a repeatable sample preparation and test procedure are needed to overcome these challenges and to obtain reliable data. In this paper, we will share some of the TIM characterization techniques developed for TIM material down-selection. The focus will be on mechanical characterization of TIM materials—including modulus, compression set, coefficient of thermal expansion (CTE), adhesion strength, and pump-out/bleed-out measurement techniques. Also, results from several TIM formulations, such as polymer TIMs and thermal gap pads, will be shared.

References

References
1.
Mahajan
,
R.
,
Chiu
,
C. P.
, and
Chrysler
,
G.
,
2006
, “
Cooling a Microprocessor Chip
,”
Proc. IEEE
,
94
(
8
), pp.
1476
1486
.
2.
Sauciuc
,
I.
,
Prasher
,
R.
,
Chang
,
J. Y.
,
Erturk
,
H.
,
Chrysler
,
G.
,
Chiu
,
C. P.
, and
Mahajan
,
R.
,
2005
, “
Thermal Performance and Key Challenges for Future CPU Cooling Technologies
,”
ASME
Paper No. IPACK2005-73242.
3.
Humpston
,
G.
, and
Jacobson
,
D. M.
,
2005
, “
Indium Solders
,”
Adv. Mater. Processes
,
163
, pp.
45
47
.
4.
Due
,
J.
, and
Robinson
,
A. J.
,
2013
, “
Reliability of Thermal Interface Materials: A Review
,”
Appl. Therm. Eng.
,
50
(
1
), pp.
455
463
.
5.
Uppal
,
A.
,
Peterson
,
J.
,
Chang
,
J. Y.
,
Guo
,
X.
,
Liang
,
F.
, and
Tang
,
W.
,
2018
, “
Thermo-Mechanical Interaction Between Thin Bare-Die Package and Thermal Solution in Next-Generation Mobile Computing Platforms
,”
ASME J. Electron. Packag.
,
141
(1), p. 010803.
6.
He
,
Y.
,
2002
, “
DSC and DMTA Studies of a Thermal Interface Material for Packaging High Speed Microprocessors
,”
Thermochim. Acta
,
392–393
, pp.
13
21
.
7.
Rubinstein
,
M.
, and
Colby
,
R. H.
,
2003
,
Polymer Physics
,
Oxford University Press
, New York, p.
291
.
8.
Chiu
,
C.-P.
,
Chandran
,
B.
,
Mello
,
K.
, and
Kelley
,
K.
,
2001
, “
An Accelerated Reliability Test Method to Predict Thermal Grease Pump-Out in Flip-Chip Applications
,”
IEEE Electronic Components and Technology Conference
(
ECTC
), Orlando, FL, May 29–June 1, pp.
91
97
.
9.
ASTM,
2018
, “
Standard Test Methods for Rubber Property—Compression Set
,” ASTM International, West Conshohocken, PA, Standard No.
ASTM D395-18
.https://www.astm.org/Standards/D395.htm
10.
Lacombe
,
R.
,
2006
,
Adhesion Measurement Methods: Theory and Practice
,
CRC Press
, Boca Raton, FL.
11.
da Silva
,
L. F. M.
,
Dillard
,
D. A.
,
Blackman
,
B. R. K.
, and
Adams
,
R. D.
,
2012
,
Testing Adhesive Joints: Best Practices
,
Wiley
, Weinheim, Germany.
12.
Sankarasubramanian
,
S.
,
Cruz
,
J.
,
Yazzie
,
K.
,
Sundar
,
V.
,
Subramanian
,
V.
,
Alazar
,
T.
,
Yagnamurthy
,
S.
,
Cetegen
,
E.
,
McCoy
,
D.
, and
Malatkar
,
P.
,
2017
, “
High Temperature Interfacial Adhesion Strength Measurement in Electronic Packaging Using the Double Cantilever Beam Method
,”
ASME J. Electron. Packag.
,
139
(
2
), p.
020902
.
13.
Dai
,
X.
,
Brillhar
,
M. V.
, and
Ho
,
P. S.
,
2000
, “
Adhesion Measurement for Electronic Packaging Applications Using Double Cantilever Beam Method
,”
IEEE Trans. Compon. Packag. Technol.
,
23
(
1
), pp.
101
116
.
14.
James
,
J. D.
,
Spittle
,
J. A.
,
Brown
,
S. G. R.
, and
Evans
,
R. W.
,
2001
, “
A Review of Measurement Techniques for the Thermal Expansion Coefficient of Metals and Alloys at Elevated Temperatures
,”
Meas. Sci. Technol.
,
12
(
3
), pp.
R1
R15
.
15.
Koohbor
,
B.
,
Valeri
,
G.
,
Kidane
,
A.
, and
Sutton
,
M.
,
2015
, “
Thermo-Mechanical Properties of Metals at Elevated Temperatures
,”
Advancement of Optical Methods in Experimental Mechanics
, Vol. 3, Springer, New York, pp. 117–123.
You do not currently have access to this content.