Pb-Free Solder: New Materials Considerations for Microelectronics Processing

Børgesen, Peter; Bieler, T. R.; Lehman, L.P.; Cotts, E. J.

doi:10.1557/mrs2007.236

Cited by 50 publications

(36 citation statements)

References 38 publications

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“…4 Borgesen and colleagues recently published a detailed examination of solder joint cracking in a BGA test vehicle. 5 The analyses in these publications demonstrated that fracture occurring after approximately 2500 thermal cycles between temperatures of À40°C and 125°C is highly correlated with the dominant crystal orientation present in a solder joint. Many active research efforts aim to understand the general deformation mechanisms of solder joints.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Orientation Evolution of the Sn Phase as a Function of Position in Ball Grid Arrays in Sn-Ag-Cu Solder Joints

Lee

Liu

Bieler

2009

Journal of Elec Materi

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The microstructure evolution of Sn-Ag-Cu solder joints during aging and thermal cycling is studied, with a focus on the Sn grain orientation in plastic ball grid array (PBGA) packages. Thermally cycled PBGA packages with a full array of 196 solder joints were examined after being subjected to various preconditions. Each PBGA package was polished to obtain plan-view crosssections of each solder joint. Solder joints were characterized using both polarized optical microscopy and orientation imaging microscopy (OIM). The observations reveal that the distribution of single and multigrain Sn microstructure as a function of position in the package is dependent on the sample's preconditions and thermal cycle history. Based on distribution maps from polarized optical microscopy observation, thermal aging has a relatively small impact on the overall fraction of single-grained solder joints. Thermal cycling, however, can cause many single-grained joints to transform into multigrained solder joints. The dependence of the grain structure distribution on different preconditions and evolution of the grain structures during thermal cycling are discussed.

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Section: Introductionmentioning

confidence: 99%

Microstructure and Orientation Evolution of the Sn Phase as a Function of Position in Ball Grid Arrays in Sn-Ag-Cu Solder Joints

Lee

Liu

Bieler

2009

Journal of Elec Materi

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“…[19][20][21][22][23] Many studies examine the reliability of solder joints arising from evolution of intermetallic morphology in the interface. [24][25][26][27][28][29] In contrast to lead-tin-based solders, for which the probability of fracture is directly related to the strain amplitude, crystal orientations in initial tin-phase microstructure have a large impact on reliability of lead-free solders, [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] so damage can develop in any region of a package. To predict deformation during the TMF cycling of a solder joint, a deep knowledge of deformation mechanisms in Sn is required.…”

Section: Introductionmentioning

confidence: 99%

“…The deformation of tin-based solders is due to operation of preferred slip systems. 40,[48][49][50][51] The governing constitutive relationships have been investigated many times, e.g., Refs. 52-54, but the role of crystal orientation on deformation has been the primary focus much less frequently.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic Crystal Plasticity Finite Element Modeling of the Effect of Crystal Orientation and Solder Joint Geometry on Deformation after Temperature Change

Zamiri

Bieler

Pourboghrat

2008

Journal of Elec Materi

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The crystal orientation of the tin phase in a Pb-free Sn solder joint has a significant effect on the stress state, and hence on the reliability of the solder joint. A set of crystal plasticity analyses was used to evaluate stress and strain resulting from a 165°C temperature change in a single-crystal joint using two simplified geometries used in practical solder joints. Phenomenological flow models for ten slip systems were estimated based upon semiquantitative information available in the literature, along with known anisotropic elastic property information. The results show that the internal energy of the system is a strong function of the tin crystal orientation and geometry of the solder joint. The internal energy (and presumably the likelihood of damage) is highest when the crystal c-axis lies in the plane of the substrate, leading to significant plastic deformation. When the a-axis is in the plane of the interface, deformation due to a 165°C temperature change is predominantly elastic. The texture of the copper substrate using isotropic Cu elastic properties, or anisotropic elastic properties with [001] k substrate normal direction, does not have a significant effect on the stress or strain in the Sn phase of the joint.

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“…Regarding Pb-free solders, on the other hand, Lee et al (2001) reported, by measuring the displacement of a pre-selected marker, that Sn-3.8Ag-0.7Cu solder has higher electromigration resistance than Pb-Sn eutectic solder. Meanwhile, Borgesen et al (2007) has pointed out problems which arise from the complex nature of the solidification behaviour of Sn-Ag-Cu and related alloys.…”

Section: Introductionmentioning

confidence: 99%

A simple method for testing the electromigration resistance of solders

et al. 2008

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Recently, the size of solder bump interconnects have been significantly reduced with the advent of highdensity packaging, and thus the evaluation of electromigration in solder bumps has become necessary. The present paper proposes a simple method to test the electromigration resistance of Pb-free solders. One of the key points of the present method is the fabrication of a simple solder sample that can produce sufficient current density to cause electromigration. Moreover, the actual local temperature of a small area subjected to electromigration in the sample was measured by a direct method. A right-angled diamondshaped hole was introduced in a thin film of solder using a focused-ion-beam system. A direct current was supplied to the film far from the hole, perpendicular to the diagonal of the hole. In this way, the current density was concentrated near to the corner of the hole, and the value of this was obtained through a theoretical analysis. It was noted that the steady temperature in the film along a line extending from the diagonal, remained constant, although the current density decreased gradually far from the corner. Therefore, the temperature at a position near the corner, where electromigration takes place, can easily be found by measuring the temperature far from the corner. The temperature was measured directly under current flow conditions by utilizing the chemical reagents with known melting points. Finally, by measuring the ratio of hillock volume to the time for the current supply as a measure of the atomic flux divergence due to electromigration, the corresponding resistances of some Pb-free solders to electromigration were evaluated.

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Pb-Free Solder: New Materials Considerations for Microelectronics Processing

Cited by 50 publications

References 38 publications

Microstructure and Orientation Evolution of the Sn Phase as a Function of Position in Ball Grid Arrays in Sn-Ag-Cu Solder Joints

Microstructure and Orientation Evolution of the Sn Phase as a Function of Position in Ball Grid Arrays in Sn-Ag-Cu Solder Joints

Anisotropic Crystal Plasticity Finite Element Modeling of the Effect of Crystal Orientation and Solder Joint Geometry on Deformation after Temperature Change

A simple method for testing the electromigration resistance of solders

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