Query: die bond

title: Flip Chip Assembly on Coreless Substrate Challenge with Die Bond Solution
abstract: Flip Chip Packages are the popular packages in many different applications. Flip Chip can provide the ideal solution for low I/O to high I/O, high electrical performance demand in where high frequency, high speed are required. By using coreless substrate with embedded fine trace substrate (ETS) technologies to achieve package miniaturization requirement.Comparing with conventional substrate, coreless substrate technologies eliminate the substrate core, and utilize substrate layers to interconnect the chip and the PCB board. It brings benefits not only with low Z height, lightweight, but also offers short interconnection distance and good signal integrity. The ETS coreless technology is a promising solution for the next generation substrate. To approach these requirements, we would like to discuss the suitable process for laser assisted bonding (LAB) thermal compression bonding (TCB) combining with molding underfill (MUF) technology and comparing with traditional mass reflow (MR) A Flip Chip Package and ETS coreless substrate combination are used for this paper experiment. The major challenge is thinner ETS coreless substrate will induce more warpage concern because of no rigid core material as supporting structure, thus ETS coreless substrate with less stiffness, is easier to bring handling issue during assembly manufacturing process. Thermal compression bonding could offer less stress to reduce CTE mismatch between silicon chip and coreless substrate. The study result of warpage comparison among TCB, LAB and mass reflow process, shows that the TCB could provide less warpage. Furthermore, TCB technology is popular used for thin core, coreless and advance silicon node product field. For LAB, it can provide the better throughput than TCB, and also provide more accuracy fine pitch bonding than MR.

title: Characteristics Study of Die Bond Process of High Power LED Package
abstract: High power light emitting diodes (LEDs) are essential in general lighting applications. Because of the characteristics of semiconductors, the optical and electrical properties of LEDs vary with the operating temperature. To increase the reliability of high power LEDs, this study conducted a shear stress test and examined the thermal dissipation alongside electrical and optical properties. The simulated and experimental trends of the thermal distribution of the LED package overlapped effectively. The results revealed that changing the side glue height from 10% to 100% of die height, which consequently increases the shear stress of 1693 g/mm2, reduces the thermal resistance of 1 degC/W, and reduces the luminous flux of 0.4 lm, can optimize the LED reliability.

title: Analysis of the bond strength of voids closed by open die forging
abstract: Large components, for instance in the energy industry, mining and heavy machinery, are produced from high weight cast as ingots followed by open die forging. Besides achieving a certain final geometry and microstructure, one of the main objectives during the forging process is the elimination of casting defects, like voids from the solidification shrinkage. This process is divided in the two stages of void closure and void healing. During the healing of the closed void a solid bond is established at high temperature. In literature void closure in open die forging is thoroughly investigated. Concerning the healing by solid bond generation there are only few studies related to voids in open die forging but there is substantial literature related to bond formation in roll hot bonding and diffusion bonding. Most of this work however determines the bond strength after cooling to room temperature. Concerning future appropriate modelling of the closure and healing process in open die forging, it is important to decide, whether a bond, which was established in one forging stroke, would be strong enough to withstand the following strokes. As a first step in this direction, this paper experimentally examines the bond strength directly after bond formation under conditions typical for open die forging strokes. The results quantitatively confirm the expected influence of forming temperature, surface enlargement, holding time and oxide films.

title: Die Attach Pre bond Inspection Innovation for Roughened Leadframe
abstract: This paper studies the challenges and behavior of epoxy material between the roughened Leadframe during the Die Attach process. Die bond on the roughened die attach paddle (DAP) of epoxy has been a challenge for its manufacturability in terms of maintaining the target epoxy volume. The study on the roughened Leadframe utilizing the Pre bond inspection parameter causing machine inspection cannot fully detect the epoxy pattern. The uneven contrast of pad's, causing pre bond inspection problem. Hard to teach set up epoxy inspection due to the contrast between leadframe die pad vs. epoxy. The roughened leadframe property has different surface contrast causing Frequent "Bond Align" and epoxy inspection error on the Roughen leadframe. This occurrence leads to risks of insufficient epoxy which is detrimental to product reliability (delamination on die bottom) and can cause manufacturing yield loss due to insufficient epoxy coverage. Using the Design of Experiment (DOE) methodology and its applicable statistical tools, the author to come up with error proofing solutions to resolve and reduce the Insufficient Epoxy. The innovative and breakthrough solutions implemented were the installation of ultra bright light with double sidelights in pre bond inspection which is the key in reducing defects rate.

title: Accessible determination of die to wafer bond strength with the Schwickerath test
abstract: Die to wafer or wafer to wafer direct bonding has been drawing significant attention and undergoing rapid development for its various applications in three dimensional integrated circuits (3D IC) such as image sensors, micro electro mechanical system (MEMS) sensors, and stacked memory products. The bond strength is one of the most considerable factors that affect the reliability of such stacked devices. Measurement of wafer to wafer bond strength is normally performed by the razor blade method, but there was no such well established technique for die to wafer direct bond. To characterize the die to wafer bond strength accurately and conveniently, this work introduced the Schwickerath three point bending test and derived an analytical solution of bond energy, which does not require initial crack preparation. To examine the correctness of applying this method in a novel area, finite element method (FEM) and razor blade experiments on equivalent samples were conducted. Furthermore, the annealing effect on die to wafer bond strength was studied. Top die thickness, loading rate in three point bending test, and the compensation factor of analytical solution are discussed and summarized in this study.

title: Development of Low Temperature Direct Bond Interconnect Technology for Die To Wafer and Die To Die Applications Stacking, Yield Improvement, Reliability Assessment
abstract: The Direct Bond Interconnect technology (DBI) commonly referred to as low temperature hybrid bonding, is an attractive bonding technology with the potential of much finer pitch and higher throughput than any solder based microbump bonding. Dielectric bonding takes place at ambient temperatures while the metal interconnection (usually Cu to Cu) forms at low annealing temperatures ranging from 150degC to 300degC. A $6 \mu \mathrm{m} pitch process is currently in high volume production for wafer to wafer (W2W) hybrid bonding.Die to wafer (D2W) and die to die (D2D) assembly has been in development at Xperi. The unique challenges include producing shallow, uniform and well controlled Cu recess on Cu bond pads of 5 um or greater, which is substantially larger than what is normally used in W2W bonding and particle minimization on die surface prior to bonding. Xperi designed daisy chain dies and wafers consist of chains ranging from 2 to 31356 interconnects. Die size is 7.96 mm by 11.96 mm, which is similar to a typical high bandwidth memory (HBM) die. The bonding studies include $10 \mu \mathrm{m} and $15 \mu \mathrm{m} diameter bond pads on $40 \mu \mathrm{m} pitch and $5 \mu \mathrm{m} diameter bond pads on $10 \mu \mathrm{m} pitch. The die thickness is either $50 \mu \mathrm{m} or $200 \mu \mathrm{m}.In this paper, we present the latest development of our chemical mechanical polish (CMP) technology to produce uniform shallow Cu recess on $15 \mu \mathrm{m} circular bond pads. The large pad size allows for a relaxed alignment accuracy requirement similar to manufacturing high throughput flip chip bonders available today. Additionally, high volume production ready process for bonding and D2W multi layer stacking are explored as well as bonding yield and reliability improvement results.

title: Die Another Day, James Bond's smoking over six decades
abstract: We aimed to examine smoking related content in all 24 James Bond movies in the Eon Productions series from 1962 to 2015. There were favourable downward trends for any smoking by James Bond (p=0.015 for trend) and for tobacco related spy gadgetry (p=0.009) Around 20% of Bond's 60 sexual partners smoked in each decade, and most recently in 2012. There were regular mentions of smoking risks to health (starting from 1967) and product placement of branded packs was present in two movies. Overall, the persisting smoking content remains problematic from a public health perspective, especially given the popularity of this movie series.

title: Bond Line Thickness Characterization for QFN Package Robustness
abstract: The paper focused on the evaluation of quad flat no leads (QFN) semiconductor package with small silicon die on different machine platforms to achieve a higher bond line thickness (BLT) of greater than 30 mm. The characterization or evaluation was narrowed down into two main diebonding machines with the objective of attaining a higher BLT for small die. High BLT capability is desired to generate clearance for the shrinkage of the glue, henceforth mitigating the glue voids. Diebond Machine 2 was able to achieve the target BLT with 30.89 mm average compared to 18.25 mm for Machine 1. Moreover, the target BLT range could only be achieved in Machine 2 only. For future works, the machine and configuration could be used for devices with comparable requirement.

title: Regulations in the U.S. and Bond Market Liquidity
abstract: This paper investigates the impacts of financial regulations on bond market liquidity, focusing on the U.S. regulations such as the Dodd Frank Act and the Volcker Rule. Our analyses at market level and bond level suggest that the mentioned regulations do not harm the liquidity of the bond market as a whole. It is evident that the regulations actually improve the bond market liquidity, especially for investment grade bonds. Non investment grade bonds are not affected by changes in regulations. These findings are also evident in the event study of announcement effects regarding regulations milestones. The analysis also suggests that the transaction costs are affected by the changes in regulations more than the price impacts. Additionally, the event study indicates that the anticipation of regulatory changes do lead to lower liquidity but these impacts only occur for big milestones and eventually die out.

title: Ultrafast electron diffraction imaging of bond breaking in di ionized acetylene
abstract: Acetylene's scission visualized by selfie Can molecules take pictures of themselves? That is more or less the principle underlying laser induced electron diffraction (LIED) A laser field strips an electron from a molecule and then sends it back to report on the structure of the remaining ion. Wolter et al. applied this technique to acetylene to track the cleavage of its C H bond after double ionization (see the Perspective by Ruan) They imaged the full structure of the molecule and also distinguished more rapid dissociative dynamics when it was oriented parallel rather than perpendicular to the LIED field. Science, this issue p. 308; see also p. 283 An electron transiently stripped from a molecule is used to image that molecule's dissociation. Visualizing chemical reactions as they occur requires atomic spatial and femtosecond temporal resolution. Here, we report imaging of the molecular structure of acetylene (C2H2) 9 femtoseconds after ionization. Using mid infrared laser induced electron diffraction (LIED) we obtained snapshots as a proton departs the [C2H2]2+ ion. By introducing an additional laser field, we also demonstrate control over the ultrafast dissociation process and resolve different bond dynamics for molecules oriented parallel versus perpendicular to the LIED field. These measurements are in excellent agreement with a quantum chemical description of field dressed molecular dynamics.