Study of Thermo-Mechanical Reliability of TSV for 8-Layer Stacked Multi Chip Package

Through silicon via (TSV) technology is becoming a hot topic for three dimensional integration in IC packaging industry. However, TSV technology raises several reliability concerns particularly caused by thermally induced stress. In this study, the thermo-mechanical reliability of copper TSV technology for the multi chip packaging was investigated using finite element method. For the multi chip package design, the 8-layer stacked chip packaging with TSV structure has been constructed as our test vehicle. The numerical analysis of stress/strain distribution and thermal fatigue life prediction were performed in order to study the impact of several design parameters such as via diameter, via pitch, die thickness, bonding pad geometry. The effects of various underfill materials which have different Young¡¯s modulus and coefficients of thermal expansion (CTEs) were also investigated. The DOE (design of experiment) analysis was performed to find the optimal design conditions for 8-layer multi chip package. The most influential factors for the stress reduction are TSV diameter and the coefficient of thermal expansion of underfill material. The larger via diameter and lower CTE showed the smaller stress distribution. On the other hand, thermal fatigue life increases with via diameter, and becomes maximum at via diameter of 20 um, then decrease with increasing via diameter. The presence of underfill material significantly increased the thermal fatigue life of TSV structure. The bonding pad design is also important for TSV durability. The smaller bonding pad showed less stress and higher thermal fatigue life. The characteristics of warpage for 8-layer multi chip package were also investigated.

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Design of Experiments in Ball Grid Array Thermal Fatigue Life Tests

Materials: Processing, Characterization and Modeling of Novel Nano-Engineered and Surface Engineered Materials ◽

10.1115/imece2002-32827 ◽

2002 ◽

Cited By ~ 1

Author(s):

T. E. Wong ◽

C. Y. Lau ◽

L. A. Kachatorian ◽

H. S. Fenger ◽

I. C. Chen

Keyword(s):

Fatigue Life ◽

Thermal Fatigue ◽

Solder Joints ◽

Ball Grid Array ◽

Temperature Cycling ◽

Design Parameters ◽

Physical Analysis ◽

Printed Wiring Board ◽

Thermal Fatigue Life ◽

The Impact

The objective of the present study is to evaluate the impact of electronic packaging design/manufacturing process parameters on the thermal fatigue life of ball grid array (BGA) solder joints. The four selected parameters are BGA under-fill materials, conformal coating, solder pad sizes on printed wiring board, and BGA rework, with each having either two or three levels of variation. A test vehicle (TV), on which various sizes of BGA daisy-chained packages are soldered, is first designed and fabricated, and then subjected to temperature cycling (−55°C to +125°C) with continuous monitoring of solder joint integrity. The total of 15 experimental cases is used in the present study. Based on monitored results, a destructive physical analysis is conducted to further isolate the failure locations and determine the failure mechanisms of the solder joints. Test results indicate that the influence of these design parameters on fatigue life is dependent on the particular package, in some instances improving the fatigue life tenfold.

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Carbon fiber reinforced tin-lead alloy as a low thermal expansion solder preform

Journal of Materials Research ◽

10.1557/jmr.1990.1266 ◽

1990 ◽

Vol 5 (6) ◽

pp. 1266-1270 ◽

Cited By ~ 20

Author(s):

C. T. Ho ◽

D. D. L. Chung

Keyword(s):

Tensile Strength ◽

Thermal Expansion ◽

Fatigue Life ◽

Carbon Fibers ◽

Thermal Fatigue ◽

Solder Joints ◽

Solder Matrix ◽

Direction Parallel ◽

Thermal Fatigue Life ◽

Low Thermal Expansion

Tin-lead (40 wt. % Pb) solder-matrix composites containing 8–54 vol.% continuous unidirectional copper plated carbon fibers were fabricated by squeeze casting for use as low thermal expansion solder preforms. The low thermal expansion greatly increased the thermal fatigue life for solder joints between materials with low thermal expansion coefficients. For example, for 29 vol.% fibers, the thermal expansion coefficient was 8 ⊠ 10−6/°C (25–105°C) in the direction parallel to the fibers compared to a corresponding value of 24 ⊠ 10−6/°C for plain solder. The thermal fatigue life for cycling 2 cm long alumina-to-alumina solder joints between 25 and 100°C was increased from 98 to 183 cycles by using 29 vol.% carbon fibers in the composite solder. The fibers also increased the tensile modulus and tensile strength of the solder, but the ductility was decreased. The copper coating on the carbon fibers increased the tensile strength and ductility of the composite.

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Thermal Fatigue Life Prediction of Ni Base Alloy Ceramic Composite Coating

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.280-283.1775 ◽

2007 ◽

Vol 280-283 ◽

pp. 1775-1778 ◽

Cited By ~ 2

Author(s):

Xie Quan Liu ◽

Xin Hua Ni ◽

Jun Ying Wang

Keyword(s):

Thermal Expansion ◽

Fatigue Crack ◽

Thermal Stress ◽

Fatigue Life ◽

Composite Coating ◽

Thermal Fatigue ◽

Base Alloy ◽

Thermal Expansion Coefficients ◽

Thermal Fatigue Life ◽

Expansion Coefficients

Ni base alloy ceramic grain composite coating is used mostly in high temperature condition, so thermal fatigue failure will be easy. If the thermal expansion coefficients and elastic modulus of Ni base alloy and ceramic grain are different, there will be thermal stresses between grain and matrix in thermosyphon. The thermal stress will arouse the initiation and growth of thermal fatigue crack. We use Eshebly-Mori-Tanaka method to study the thermal stress field in matrix and grain. It can be shown that the more difference of thermal expansion coefficients between Ni base alloy and ceramic grain is, the bigger the thermal stress is. The thermal stress relates to volume fractions and elastic constants of Ni base alloy and ceramic grain. Based on low-cycle fatigue crack growth rate formation, the thermal fatigue life was computed. The bigger thermal stress is, the smaller thermal fatigue life is. Thermal life is an exponential function of crack initiation length and critical length.

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Development of Highly Reliable BGA and Flip-Chip Structures by Using Cu-Cored Solder Ball

ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems, MEMS and NEMS: Volume 2 ◽

10.1115/ipack2011-52115 ◽

2011 ◽

Cited By ~ 2

Author(s):

Hisashi Tanie ◽

Nobuhiko Chiwata ◽

Motoki Wakano ◽

Masaru Fujiyoshi ◽

Shinichi Fujiwara

Keyword(s):

Fatigue Life ◽

Impact Strength ◽

Solder Joint ◽

Thermal Fatigue ◽

Flip Chip ◽

Bending Test ◽

Insulating Layer ◽

Thermal Fatigue Life ◽

Impact Bending ◽

The Impact

A Cu-cored solder joint is a micro-joint structure in which a Cu sphere is encased in solder. It results in a more accurate height and has low thermal and electrical resistance. In a previous paper, we examined the thermal fatigue life of a Cu-cored solder ball grid array (BGA) joint through actual measurements and crack propagation analysis. As a result, we found that the thermal fatigue life of a Cu-cored solder BGA joint is about twice as long as that of a conventional joint. In this paper, we describe the impact strength of a Cu-cored solder BGA joint determined by conducting an impact bending test. This test is a technique to measure the impact strength of a micro-solder joint. This method was developed by Yaguchi et al., and they confirmed that it is an easier and more accurate method of measuring impact strength than the board level drop test. First, we simulated the impact bending test by finite element analysis (FEA) and calculated solder strains of both Cu-cored solder joints and conventional joints. The results indicated that the maximum solder strain of a Cu-cored solder joint during the impact bending test was slightly smaller than that of a conventional joint. The solder volume of the Cu-cored solder joint was also smaller than that of a conventional joint. On the other hand, joint stiffness of the Cu-cored solder joint was larger than in a conventional joint. The former increases the solder strain of the Cu-cored solder joint, and the latter decreases it. By balancing these phenomena, it is possible to obtain a maximum solder strain in the Cu-cored solder joint that is slightly smaller than in a conventional joint. Based on these phenomena, the impact strength of the Cu-cored solder joint is predicted to be the same as or higher than that of a conventional joint. Therefore, we measured the impact strengths of a Cu-cored solder joint and a conventional joint using the impact bending test. As a result, we confirmed that the impact strength of the Cu-cored solder joint was the same as or higher than that of a conventional joint. Accordingly, a Cu-cored solder BGA joint is a micro-joint structure that makes it possible to improve thermal fatigue life without decreasing impact strength. Moreover, we investigated whether the use of Cu-cored solder in a flip-chip (FC) joint improved its reliability. As a result, we found that the stress of an insulating layer on a Si die surface was reduced by using a Cu-cored solder FC joint. This is because bending deformation of the Cu land occurs, and the difference in thermal deformation between the Si chip and the Cu land becomes small. Accordingly, the Cu-cored solder FC joint is a suitable structure for improving reliability of a low-strength insulating layer.

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Thermal fatigue reliability for Cu-Pillar bump interconnection in flip chip on module and underfill effects

Soldering & Surface Mount Technology ◽

10.1108/ssmt-03-2014-0008 ◽

2015 ◽

Vol 27 (1) ◽

pp. 1-6 ◽

Cited By ~ 4

Author(s):

Jae B. Kwak ◽

Soonwan Chung

Keyword(s):

Fatigue Life ◽

Thermal Fatigue ◽

Life Prediction ◽

Flip Chip ◽

Solder Bump ◽

Mechanical Reliability ◽

Content Type ◽

Thermal Fatigue Life ◽

Cu Pillar ◽

Cu Pillar Bump

Purpose – The purpose of this paper is to assess the thermo-mechanical reliability of a solder bump with different underfills, with the evaluation of different underfill materials. As there is more demand in higher input/output, smaller package size and lower cost, a flip chip mounted at the module level of a board is considered. However, bonding large chips (die) to organic module means a larger differential thermal expansion mismatch between the module and the chip. To reduce the thermal stresses and strains at solder joints, a polymer underfill is added to fill the cavity between the chip and the module. This procedure has typically, at least, resulted in an increase of the thermal fatigue life by a factor of ten, as compared to the non-underfilled case. Yet, this particular case is to deal with a flip chip mounted on both sides of a printed circuit board (PCB) module symmetrically (solder bump interconnection with Cu-Pillar). Note that Cu-Pillar bumping is known to possess good electrical properties and better electromigration performance. The drawback is that the Cu-Pillar bump can introduce high stress due to the higher stiffness of Cu compared to the solder material. Design/methodology/approach – As a reliability assessment, thermal cyclic loading condition was considered in this case. Thermal life prediction was conducted by using finite element analysis (FEA) and modified Darveaux’s model, considering microsize of the solder bump. In addition, thermo-mechanical properties of four different underfill materials were characterized, such as Young’s modulus at various temperatures, coefficient of temperature expansion and glass transition temperature. By implementing these properties into FEA, life prediction was accurately achieved and verified with experimental results. Findings – The modified life prediction method was successfully adopted for the case of Cu-Pillar bump interconnection in flip chip on the module package. Using this method, four different underfill materials were evaluated in terms of material property and affection to the fatigue life. Both predicted life and experimental results are obtained. Originality/value – This study introduces the technique to accurately predict thermal fatigue life for such a small scale of solder interconnection in a newly designed flip chip package. In addition, a guideline of underfill material selection was established by understanding its affection to thermo-mechanical reliability of this particular flip chip package structure.

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