In the current work, a test scheme to evaluate solder joint interface fracture toughness using double cantilever beam (DCB) test has been successfully demonstrated. The obtained results, in terms of critical energy release rate, predict the joint failure based on the principle of fracture mechanics. The results can be used as a materials property in the reliability design of various types of solder-ball joined packages. DCB specimens made of 99.9 wt% copper were selected in the current work. Eutectic Sn-37Pb and lead-free Sn-3.5Ag-0.5Cu solders were used to join two pieces of the copper beams with controlled solder thickness. The test record showed steady propagation of the crack along the solder / copper interface, which verifies the viability of such a testing scheme. Interface fracture toughness for as-joined, extensively-reflowed and thermally aged samples has been measured. Both the reflow treatment and the thermal aging lead to degradation of the solder joint fracture resistance. Reflow treatment was more damaging as it induces much faster interface reaction. Fractographic analysis established that the fracture has a mixed micromechanism of dimple and cleavage. The dimples are formed as a result of the separation between the hard intermetallic compound (IMC) particles and the soft solder material, while the cleavage is formed by the brittle split of the IMCs. When the IMC thickness is increased due to extended interface reaction, the proportion of IMC cleavage failure increases, and this was reflected in the decrease of the critical energy release rate.

For the past several years, the semiconductor industry has been responding to the RoHS directive to eliminate certain hazardous substances from electronic components. One of the areas where work is still ongoing to comply is in the area of flip chip interconnects. Currently, leaded flip chip interconnects are allowed under an exemption in the RoHS directive due to a perceived lack of a technically viable solution. Recently, a number of Pb-Free flip chip interconnects have been introduced to the industry and have been in high volume production for a few years. Electromigration is an area which has received quite a bit of attention over the years. There is a large body of data in the area of High-Pb and Sn/Pb eutectic flip chip interconnect systems, but there is still a relatively small database with regard to Pb-Free flip chip interconnects. This paper addresses relative electromigration performance on different base surface finishes of organic laminates, which is one of the key aspects where additional knowledge is needed to understand the proper implementation direction for Pb-Free flip chip interconnects. The impact of ENIG, ENEPIG, and bare Cu on Sn/Ag bump electromigration including FA results is presented.

Conventional assessment of solder joint reliability uses either ball shear test or solder ball pull test. The test results are reported in terms of materials strength in either shear or tensile mode, and the strength values are size-dependent. Therefore these test results are largely useful only for qualitative comparison and qualification of the products. In the current effort, we aim at developing an assessment scheme for solder joint interface fracture toughness. The obtained results, in terms of critical energy release rate, predict the joint failure based on the principle of fracture mechanics. The results can be used as a materials property in the reliability design of various types of solder-ball joined packages. Double cantilever beam (DCB) specimens made of 99.9 wt% copper were selected in the current work. Eutectic Sn-37Pb solder was used to join two pieces of the copper plates with controlled solder thickness. The test record showed steady propagation of the crack along the solder / copper interface, which verifies the viability of such a testing scheme. Interface fracture toughness for as-joined, extensively-reflowed and thermally aged samples has been measured. Both the reflow treatment and the thermal aging lead to degradation of solder joint fracture resistance. To understand the degradation, fractographic analysis by scanning electron microscopy (SEM) has been carried out from both top and cross-sectional views of the fractured surfaces.

Interfacial delamination is a common failure mode in multilayered IC packages. In this paper, an experimental technique using Brazil-nut specimens is employed to determine the interfacial fracture toughness of an adhesively sandwiched joint with the introduction of edge interfacial crack. The design of experiments (DOE) is applied to study variations in strain rates and the thickness of the sandwich structure. In addition, the effects of moisture content and temperature on the interfacial adhesion are investigated. For the DOEs conducted, as the loading angle increases from 20° to 90°, the interfacial fracture toughness decreases. The fracture toughness and its corresponding mode mixity are determined from the measured critical load by finite element modeling computation.

Insufficient bonding between mufti-wall carbon nanotubes (MWCNTs) and the matrix reduces the effectiveness of MWCNT reinforcements in sol-gel silica dielectric composites. This paper investigates the efficacy of various surfactants in improving the bonding through morphological and mechanical characterization of MWCNT-reinforced sol-gel silica dielectric films. It is found that use of some surfactants while dispersing MWCNTs improves the modulus and hardness. The improved mechanical properties possibly reduce the delamination problem of Cu/low-k films during flip-chip packaging and wirebonding. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.