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In this paper, the performance of a complete halogen-free (HF) board assembled with five ball grid array components using daisy chains on an 8-layer high density interconnection printed circuit board (PCB) was examined using bending tests. The solder joint was composed of the SAC405 solder ball melted with the SAC105 solder paste on the Cu pad surface of either organic solderable preservative (OSP) or electroless nickel immersion gold (ENIG), and was tested to examine the extent of Ag3Sn intermetallic compound (IMC) formed. A board-level cyclic bending test was executed to the as-reflowed assemblies according to the JESD22-B113 standard to evaluate the reliability of various surface finished HF PCB assemblies under a recommended load condition. By Weibull analyzes the characteristic lives of the assemblies were 99098 and 130290 cycles on OSP soldering system and ENIG system respectively, indicating that the ENIG had a higher bending fatigue endurance as compared to the OSP. The dominant failure mode was the fracture of Cu trace within the micro-via caused by the crack of the resin coated copper layer. At the interface of the solder joint, the IMC formed on both OSP and ENIG was (Cu, Ni)6Sn5 with various Ni contents of 3.9 and 20.1 at%, and different thicknesses of 5.6 and 1.1 \mum, respectively. Numerical simulations showed that both composition and thickness of IMC influenced the stress concentrations and characteristic life of the HF test vehicle as they could slightly increase localized solder joint rigidity and result in more serious pull and drag behaviors at the corner joint. Although the (Cu, Ni)6Sn5 on the ENIG was stiffer than that on the OSP, the thicker IMC layer instead increased the stress on the OSP system due to size effect, and resulted in a lower characteristic life. [ABSTRACT FROM PUBLISHER]

In this article, low-temperature Cu–Cu bonding with the Ag passivation layer was accomplished at 180 °C for 3 min without a postannealing process. The Ag passivation layer effectively prevents Cu from oxidation and assists Cu diffusion to realize low-temperature bonding. The small grain size of the Ag passivation layer controlled by sputtering working pressure is observed to improve bonding quality. Different plasma treatment parameters and bonding conditions were executed to evaluate bonding quality. The diffusion behavior of passivation bonding is investigated, and the corresponding mechanism is discussed as well. In addition, reliability assessments, including thermal cycling, high-temperature storage, and unbiased highly accelerated stress test, indicate excellent stability of this bonding structure, showing the potential for low-temperature bonding technology in 3-D integration applications. [ABSTRACT FROM AUTHOR]

This paper is a theoretical and experimental assessment of the solder joint reliability of an advanced high-density interposer-based 2.5-D IC integration technology on-board under drop impact in accordance with the JEDEC standard. Focus is placed on the influences of underfill on the solder joint reliability. The transient dynamic responses of the packaging technology are simulated using Input-G finite element analysis, with the use of the Johnson-Cook model for describing the constitutive behaviors of the solder interconnect materials. Furthermore, an energy-based model is utilized for predicting the drop impact solder joint fatigue life. The effectiveness of the proposed theoretical models is demonstrated through comparison with the drop test experiment. Finally, the effects of some essential factors including the allowed JEDEC shock pulse tolerances are examined in order to establish a design guideline for enhanced shock resistance capability. Results show that underfill and even partial underfill can significantly improve the drop impact solder joint reliability of the 2.5-D IC integration technology. The solder joint reliability turns out to be considerably affected by the shock pulse tolerances, suggesting that there is a crucial need to regularly calibrate the precision of drop testers for minimizing the prediction uncertainty. [ABSTRACT FROM PUBLISHER]

In this research, thousands of 20-\mum pitch microbumps with a diameter of 10 \mum and a structure of a pure Sn cap on a Cu pillar were electroplated on 8-inch wafers, and those wafers were then respectively singularized as a top chip and bottom Si interposer for stacking. Two methods, namely conventional reflow and solid–liquid interdiffusion (SLID) bonding, were adopted to interconnect the microbumps. In the former case, the as-plated Sn caps were fluxed, and the chip was then placed on the Si interposer. Afterward, the Sn caps on the chip and on the Si interposer were melted and interconnected at a peak temperature of 250^\circC. The flux residues were cleaned after reflow, and the microgap between the chip and the Si interposer was fully sealed by a capillary underfill. In the SLID bonding process, the oxides on the as-plated Sn caps were removed by a plasma etcher first, and then the chip was placed on the interposer with a bonder as well, subsequently, the Sn caps were heated to 260^\circC to react with the Cu pillar to form Cu6Sn5. In the final step, the intermetallic microjoints were protected by the same capillary underfill. After assembly, the Joint Electron Devices Engineering Council preconditioning test was used to screen the test vehicles for reliability assessment, and then a temperature cycling test was performed to predict the lifespan of the microjoints. The test results showed that the microjoints formed by SLID bonding provided a superior reliability performance to those assembled by reflow. The fracture of the microjoints was caused by the volume contraction induced by the growth of Cu6Sn5, but the failure mechanisms of those two microjoints were quite different. [ABSTRACT FROM AUTHOR]