Fatigue life of lead-free solder thermal interface materials at varying bond line thickness in microelectronics

2014 ◽  
Vol 54 (1) ◽  
pp. 239-244 ◽  
Author(s):  
Mathias Ekpu ◽  
Raj Bhatti ◽  
Michael I. Okereke ◽  
Sabuj Mallik ◽  
Kenny Otiaba
Keyword(s):  
Fatigue Life ◽  
Bond Line ◽  
Lead Free ◽  
Thermal Interface Materials ◽  
Lead Free Solder ◽  
Thermal Interface ◽  
Line Thickness ◽  
Bond Line Thickness ◽  
Free Solder ◽  
Interface Materials

Reliability analysis of SnAgCu lead-free solder thermal interface materials in microelectronics

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mathias Ekpu
Keyword(s):  
Fatigue Life ◽  
Heat Sink ◽  
Flip Chip ◽  
Lead Free ◽  
Thermal Interface Materials ◽  
Lead Free Solder ◽  
Thermal Interface ◽  
Content Type ◽  
Free Solder ◽  
Interface Materials

Purpose In microelectronics industry, the reliability of its components is a major area of concern for engineers. Therefore, it is imperative that such concerns are addressed by using the most reliable materials available. Thermal interface materials (TIMs) are used in electronic devices to bridge the topologies that exists between a heat sink and the flip chip assembly. Therefore, this study aims to investigate the reliability of SAC405 and SAC396 in a microelectronics assembly. Design/methodology/approach In this paper, SnAgCu solder alloys (SAC405 and SAC396) were used as the TIMs. The model, which comprises the chip, TIM and heat sink base, was developed with ANSYS finite element analysis software and simulated under a thermal cycling load of between −40°C and 85°C. Findings The results obtained from this paper were based on the total deformation, stress, strain and fatigue life of the lead-free solder materials. The analyses of the results showed that SAC405 is more reliable than SAC396. This was evident in the fatigue life analysis where it was predicted that it took about 85 days for SAC405 to fail, whereas it took about 13 days for SAC396 to fail. Therefore, SAC405 is recommended as the TIM of choice compared to SAC396 based upon the findings of this investigation. Originality/value This paper is centred on SnAgCu solders used as TIMs. This paper demonstrated that SAC405 is a reliable solder TIM. This can guide manufacturers of electronic products in deciding which SAC solder to apply as TIM during the assembly process.

Bond Line Thickness of Thermal Interface Materials With Carbon Nanotubes

2005 ◽  
Author(s):  
Senthil A. G. Singaravelu ◽  
Xuejiao Hu ◽  
Kenneth E. Goodson
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Volume Fraction ◽  
Bond Line ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Line Thickness ◽  
Bond Line Thickness ◽  
The Impact ◽  
Interface Materials

Increasing power dissipation in today’s microprocessors demands thermal interface materials (TIMs) with lower thermal resistances. The TIM thermal resistance depends on the TIM thermal conductivity and the bond line thickness (BLT). Carbon Nanotubes (CNTs) have been proposed to improve the TIM thermal conductivity. However, the rheological properties of TIMs with CNT inclusions are not well understood. In this paper, the transient behavior of the BLT of the TIMs with CNT inclusions has been measured under controlled attachment pressures. The experimental results show that the impact of CNT inclusions on the BLT at low volume fractions (up to 2 vol%) is small; however, higher volume fraction of CNT inclusions (5 vol%) can cause huge increase in TIM thickness. Although thermal conductivities are higher for higher CNT fractions, a minimum TIM resistance exists at some optimum CNT fraction for a given attachment pressure.

Two-Medium Model for the Bond Line Thickness of Particle Filled Thermal Interface Materials

2004 ◽  
Author(s):  
Xuejiao Hu ◽  
Senthil Govindasamy ◽  
Kenneth E. Goodson
Keyword(s):  
Filler Particle ◽  
Bond Line ◽  
Thermal Interface Materials ◽  
Heterogeneous Structure ◽  
Thermal Interface ◽  
Line Thickness ◽  
Medium Model ◽  
Bond Line Thickness ◽  
The Impact ◽  
Interface Materials

Thermal interface materials (TIMs) are widely used in electronics packaging. Increasing heat generation rates require lower values of the TIM thermal resistance, which depends on the material thermal conductivity and the TIM thickness, or the bond line thickness (BLT). The variation of the TIM thickness is not well understood. The major difficulty comes from the complexity of TIMs as condensed particle systems, especially when the TIM thickness is squeezed to several multiples of the filler particle diameter. This confined heterogeneous structure makes the behavior of TIMs different from that of homogeneous fluids. In this study, we propose a two-medium model for the BLT. The variation of BLT with attachment pressure is modeled using two parameters: the viscidity of the fluids and the interactions of particles. The predictions are compared with the measurements for TIMs made of aluminum oxide particles (sizes: 0.6–6 microns, volume fractions: 30%–50%) and silicon oil (kinematic viscosity: 100 cst and 1000 cst). Reasonable agreement is obtained for different applied pressures. Results indicate that the impact of the particle interactions is an important factor governing the variation of the TIM BLT, especially when the BLT is small.

Effect of Load and Interface Materials on Thermal Contact Resistance between Similar and Dissimilar Materials

2014 ◽  
Vol 592-594 ◽  
pp. 1493-1497 ◽  
Author(s):  
Swamy R. Narayana ◽  
Prabhu K. Narayan
Keyword(s):  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Dissimilar Materials ◽  
Lead Free ◽  
Thermal Interface Materials ◽  
Lead Free Solder ◽  
Thermal Interface ◽  
Free Solder ◽  
Interface Materials

The thermal contact resistance (TCR) between similar and dissimilar materials (copper, aluminium, brass and type 304 stainless steel) was assessed. Copper foil, aluminium foil, lead and Sn-9Zn lead free solder were selected as thermal interface materials (TIMs). The interfacial contact pressure was varied by application of load on materials in contact. The interfacial heat flux was estimated by solving the inverse heat conduction problem (IHCP). At higher load, the temporal variation of thermal contact resistance showed early occurrence of peak and lower values of TCR. The use of thermal interface materials reduced the contact resistance between the hot source and cold sink materials. Among the interface materials used, Sn-9Zn lead free solder showed the lowest contact resistance. This was attributed to the solid to liquid phase transformation at higher temperatures and the conformance of the interface material to surfaces in contact. Factorial experiments were carried out to determine the significance of experimental variables on TCR. The analysis showed that the effect of applied load on TCR was significant compared to other parameters.

Thermal Resistance of Bond-Lines Formed With Composite Thermal Interface Materials

2005 ◽  
Author(s):  
Gary Lehmann ◽  
Hao Zhang ◽  
Arun Gowda ◽  
David Esler
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Thermal Resistance ◽  
Bond Line ◽  
Surface Conductance ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Bond Line Thickness ◽  
Matrix Surface ◽  
Interface Materials

Measurements and modeling of the thermal resistance of thin (< 100 microns) bond-lines are reported for composite thermal interface materials (TIMs). The composite TIMs consist of alumina particles dispersed in a polymer matrix to form six different adhesive materials. These model TIMs have a common matrix material and are distinguished by their particle size distributions. Bond-lines are formed in a three-layer assembly consisting of a substrate-TIM-substrate structure. The thermal resistance of the bond-line is measured, as a function of bond-line thickness, using the laser flash-technique. A linear variation of resistance with bond-line thickness is observed; Rbl = β · Lbl + Ro. A model is presented that predicts the effective thermal conductivity of the composite as a function of the particle and matrix conductivity, the particle-matrix surface conductance, the particle volume fraction and the particle size distribution. Specifically a method is introduced to account for a broad, continuous size distribution. A particle-matrix surface conductance value of ∼10W/mm2K is found to give good agreement between the measured and predicted effective thermal conductivity values of the composite TIMs.

scholarly journals Effect of Elevated Temperatures on SAC305 Solder Alloy Thermal Interface Material in a Microelectronic Assembly

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Mathias Ekpu
Keyword(s):  
Fatigue Life ◽  
Elevated Temperature ◽  
Elevated Temperatures ◽  
Electronic Devices ◽  
Thermal Interface Material ◽  
Lead Free ◽  
Lead Free Solder ◽  
Sac305 Solder ◽  
Thermal Interface ◽  
Free Solder

In microelectronics assemblies, Thermal Interface Materials (TIMs) are vital to the reliability of the devices in operation. Some electronic devices operate in elevated temperature environments such as military and industrial applications. Hence, the need to evaluate the reliability of such devices at elevated temperatures. Tin-Silver-Copper lead-free solder TIMs have been used during the assembly process of some electronic devices operating under harsh temperature environments. In this study, the reliability of SAC305 lead-free solder TIM was considered at elevated temperatures ranging from 100 oC to 200 oC at 25 oC interval, and aged for about an hour. ANSYS finite element analysis software was employed for the design and evaluation of SAC305 lead-free solder model. The findings of the investigation demonstrated that the higher the harsh temperature environment, the lower the reliability of the SAC305 solder TIM. In addition, the highest fatigue life (36735 or 4.2 years) was recorded at 100 oC, while 200 oC recorded the lowest fatigue life (1014 or 0.12 years). The fatigue life is an indication of the lifespan of the TIM when in operation. This research will be beneficial to engineers assembling microelectronic products.  Keywords— elevated temperature; fatigue life; microelectronics; reliability; SAC305 solder  

Rheological Study of Micro Particle Laden Polymeric Thermal Interface Materials: Part 1 — Experimental

2002 ◽  
Author(s):  
Ravi S. Prasher ◽  
Jim Shipley ◽  
Suzana Prstic ◽  
Paul Koning ◽  
Jin-Lin Wang
Keyword(s):  
Thermal Conductivity ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Electronics Cooling ◽  
Bond Line ◽  
Rheological Parameters ◽  
Thermal Interface Materials ◽  
Particle Volume ◽  
Thermal Interface ◽  
Interface Materials

Particle laden polymers are one of the most prominent thermal interface materials (TIM) used in electronics cooling. Most of the research groups have primarily dealt with the understanding of the thermal conductivity of these types of TIMs. Thermal resistance is not only dependent on the thermal conductivity but also on the bond line thickness (BLT) of these TIMs. It is not clear that which material property(s) of these particle laden TIMs affects the BLT. This paper discusses the experimental measurement of rheological parameters such as non-Newtonian strain rate dependent viscosity and yield stress for 3 different particle volume fraction and 3 different base polymer viscosity materials. These rheological and BLT measurements vs. pressure will be used to model the BLT of particle-laden systems for factors such as volume fraction.

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