scholarly journals A Novel Method for Characterization of Ultralow Viscosity NCF Layers Using TCB for 3D Assembly

2021 ◽  
Vol 18 (1) ◽  
pp. 12-20
Author(s):  
Giovanni Capuz ◽  
Melina Lofrano ◽  
Carine Gerets ◽  
Fabrice Duval ◽  
Pieter Bex ◽  
...  
Keyword(s):  
Solder Joint ◽  
Flat Glass ◽  
High Viscosity ◽  
Volume Control ◽  
Interface Temperature ◽  
Bond Force ◽  
Fine Pitch ◽  
Solder Bumps ◽  
3D Assembly ◽  
Tool Position

Abstract For die-to-wafer (D2W) stacking of high-density interconnects and fine-pitch microbumps, underfill serves to fill the spaces in-between microbumps for protection and reliability. Among the different types of underfill, nonconductive film (NCF) has the advantages of fillet and volume control. However, one of the challenges is the solder joint wetting. An NCF must have good embedded-flux activation to mitigate Cu UBM pad oxidation due to the repeated TCB cycles that accelerate oxidation on neighboring dice. The flux in the NCF also helps in wetting the solder bumps. To realize efficient solder wetting, one must also understand the NCF deformation quality, which is a function of its viscosity. This parameter has direct impact on the deformation of solder bumps. High-viscosity NCF would be difficult to deform, thus preventing solder contact to pad during TCB reflow temperature. High bond force is required and could lead to reduced alignment accuracy. For a low viscous NCF, it requires low bond force. Solder joint wetting is a challenge with excessive squeezeout due to fast and instantaneous deformation. We seek to demonstrate in this article a creative methodology for NCF material characterization, considering the factors of NCF viscosity, deformation, and solder squeezeout. We use TCB tool position-tracking data to define the deformation curve of the NCF as a function of temperature and time at very fast profile of TCB. We use the NCF viscosity curve as reference in relation to the actual deformation, and predict dynamic deformation in three different configurations. Deformation test configurations were performed on chips with and without microbumps bonded with a rigid flat glass surface and with a bottom Cu UBM pad. The experiments were performed with different heating ramp rates at target above Sn reflow of ~250°C interface temperature. As validation, we applied the optimized TCB process (force, temperature, and ramp rate) on a test vehicle with 20 and 40 μm pitch daisy chains and obtained very good connectivity with good joint and IMC formation.

A novel method for characterization of Ultra Low Viscosity NCF layers using TCB for 3D Assembly

2020 ◽  
Vol 2020 (1) ◽  
pp. 000185-000191
Author(s):  
Giovanni Capuz ◽  
Melina Lofrano ◽  
Carine Gerets ◽  
Fabrice Duval ◽  
Pieter Bex ◽  
...  
Keyword(s):  
Solder Joint ◽  
Deformation Behavior ◽  
High Viscosity ◽  
Interface Temperature ◽  
Parallel Plates ◽  
Bond Force ◽  
Low Viscosity ◽  
Solder Bumps ◽  
Conductive Film ◽  
Squeeze Out

Abstract For die to wafer bonding of high-density interconnects and fine pitch microbumps developing and characterizing suitable underfill materials are required. In general, underfill serve to fill the spaces in-between microbumps for protection and reliability. Among the different types of underfill, Non-Conductive Film (NCF) has the advantages of fillet and volume control, and a built-in flux to aid wetting. However, challenges arise for thin dies and microbumps with fine pitches on film lamination, voiding, transparency, filler percentage, dicing compatibility and most importantly, deformation behavior and possibility to improve solder joint wetting. In a Die-to-Wafer D2W stacking with a Sn solder bump interconnect to Cu UBM, concern is high on the Cu pad oxidation due to the repeated TCB cycles that accelerate oxidation on neighboring dies. Process mitigation is needed to help reducing the oxidation. But even so, an NCF must have good embedded flux activation. Another main factor for an NCF to have efficient TCB process with good solder joint wetting, is the NCF deformation quality in which is a function of its viscosity. This parameter has direct impact on the deformation of solder bumps. High viscosity NCF would be difficult to deform, thus preventing solder contact to pad during TCB reflow temperature. High bond force is required and could lead to reduced alignment accuracy. Filler entrapment is also a subsequent concern for high filler loading, high viscosity NCF. For a low viscous NCF, careful attention in process characterization is needed in TCB with low bond force. Solder joint wetting is a problem with excessive squeeze-out due to fast and instantaneous deformation. With low viscosity, not only the bond force applied should be low, but the deformation behavior should also be understood to enable an effective NCF. We seek to demonstrate in this paper a creative methodology for Non-Conductive Film (NCF) material characterization, considering the factors of NCF viscosity, deformation, and solder squeeze-out. Characterizing NCF viscosity at fast TCB profiles is challenging considering deformation behavior of both the NCF itself and the solder bumps that shaped the solder squeeze-out and wetting. Furthermore, in this paper we use TCB tool position tracking to define the deformation curve of NCF film as a function of temperature and time at very fast profile of TCB. We use material viscosity curve as reference in relation to the actual deformation, and predict dynamic deformation based on Reynold’s equation within TCB profile duration. The experiments were performed with different heating ramp rates at target above Sn reflow of ~250C interface temperature. The deformation analysis is not limited to thin film sandwiched between parallel plates. Deformation test was performed on chips with and without microbumps and with rigid flat glass surface and its combinations. Deformation of underfill is recorded in the readout of TCB tool. As validation, we applied the optimized TCB process (force, temperature, and ramp rate) on a test vehicle with 20 and 40um pitch daisy chains and obtained close to 95% electrical yield with good joint and IMC formation. The cross-section SEM images show good wetting, revealing good activation of built-in flux when the optimized TCB profile was used.

Reballing/Rebumping Ultra-Fine Pitch Packages Less Than 0.5 mm Pitch for FA

2014 ◽  
Author(s):  
Bob Wettermann
Keyword(s):  
Solder Joint ◽  
Failure Analysis ◽  
Joint Strength ◽  
Semiconductor Devices ◽  
X Ray ◽  
Fine Pitch ◽  
Manual Methods

Abstract As the pitch and package sizes of semiconductor devices have shrunk and their complexity has increased, the manual methods by which the packages can be re-bumped or reballed for failure analysis have not kept up with this miniaturization. There are some changes in the types of reballing preforms used in these manual methods along with solder excavation techniques required for packages with pitches as fine as 0.3mm. This paper will describe the shortcomings of the previous methods, explain the newer methods and materials and demonstrate their robustness through yield, mechanical solder joint strength and x-ray analysis.

Combined Temperature and Force Control for Robotic Friction Stir Welding

2013 ◽  
Author(s):  
Axel Fehrenbacher ◽  
Christopher B. Smith ◽  
Neil A. Duffie ◽  
Nicola J. Ferrier ◽  
Frank E. Pfefferkorn ◽  
...  
Keyword(s):  
Control System ◽  
Force Control ◽  
Closed Loop ◽  
Interface Temperature ◽  
Closed Loop Control ◽  
Weld Quality ◽  
Loop Control ◽  
Friction Stir ◽  
Tool Position ◽  
Robotic Friction Stir Welding

The objective of this research is to develop a closed-loop control system for robotic friction stir welding (FSW) that simultaneously controls force and temperature in order to maintain weld quality under various process disturbances. FSW is a solid-state joining process enabling welds with excellent metallurgical and mechanical properties, as well as significant energy consumption and cost savings compared to traditional fusion welding processes. During FSW, several process parameter and condition variations (thermal constraints, material properties, geometry, etc.) are present. The FSW process can be sensitive to these variations, which are commonly present in a production environment; hence, there is a significant need to control the process to assure high weld quality. Reliable FSW for a wide range of applications will require closed-loop control of certain process parameters. A linear multi-input-multi-output process model has been developed that captures the dynamic relations between two process inputs (commanded spindle speed and commanded vertical tool position) and two process outputs (interface temperature and axial force). A closed-loop controller was implemented that combines temperature and force control on an industrial robotic FSW system. The performance of the combined control system was demonstrated with successful command tracking and disturbance rejection. Within a certain range, desired axial forces and interface temperatures are achieved by automatically adjusting the spindle speed and the vertical tool position at the same time. The axial force and interface temperature is maintained during both thermal and geometric disturbances and thus weld quality can be maintained for a variety of conditions in which each control strategy applied independently could fail.

scholarly journals Demonstration of fine pitch FCOB (Flip Chip on Board) assembly based on solder bumps at Fermilab

2009 ◽  
Vol 4 (11) ◽  
pp. T11001-T11001
Author(s):  
E Skup ◽  
M Trimpl ◽  
R Yarema ◽  
J C Yun
Keyword(s):  
Flip Chip ◽  
Fine Pitch ◽  
Solder Bumps

Process Characterization and the Effect of Process Defects on Flip Chip Reliability

1999 ◽  
Author(s):  
Brian J. Lewis ◽  
Hilary Sasso
Keyword(s):  
Process Parameters ◽  
Flip Chip ◽  
Failure Modes ◽  
Shock Testing ◽  
Fine Pitch ◽  
Process Characterization ◽  
Solder Bumps ◽  
Optimum Height ◽  
High Yields

Abstract Processing fine pitch flip chip devices continues to pose problems for packaging and manufacturing engineers. Optimizing process parameters such that defects are limited and long-term reliability of the assembly is increased can be a very tedious task. Parameters that effect the robustness of the process include the flux type and placement parameters. Ultimately, these process parameters can effect the long-term reliability of the flip chip assembly by either inhibiting or inducing process defects. Therefore, care is taken to develop a process that is robust enough to supply high yields and long term reliability, but still remains compatible with a standard surface mount technology process. This is where process optimization becomes most critical and difficult. What is the optimum height of the flux thin film used for a dip process? What force is required to insure that the solder bumps make contact with the pads? What are the limiting boundaries in which high yields and high reliabilities are achieved, while maintaining a streamlined, proven process? The following study evaluates a set of process parameters and their impact on process defects and reliability. The study evaluates process parameters including, flux type, flux application parameters, placement force and placement accuracy to determine their impact. Solder voiding, inadequate solder wetting, and crack propagation and delamination in the underfill layer are defects examined in the study. Assemblies will be subjected to liquid-to-liquid thermal shock testing (−55° C to 125°C) to determine failure modes due to the aforementioned defects. The results will show how changes in process parameters effect yield and reliability.

Lead Free Paste with under 3um Solder Particles for Fine Pitch C4 bumping and pre-coating solder applications

2013 ◽  
Vol 2013 (DPC) ◽  
pp. 000862-000889
Author(s):  
Hironori Uno ◽  
Masayuki Ishikawa ◽  
Akihiro Masuda ◽  
Hiroki Muraoka ◽  
Kanji Kuba
Keyword(s):  
Chemical Reduction ◽  
Average Particle Size ◽  
Average Particle ◽  
Solder Paste ◽  
Chemical Reduction Method ◽  
Property Evaluation ◽  
Fine Pitch ◽  
Solder Bumps ◽  
Size Of Particles ◽  
Average Size

The work to be detailed in this paper is our development of 96.5mass%Sn-3.0mass%Ag-0.5mass%Cu fine solder particles with an average particle size of under 3um (D50), using a chemical reduction method. An evaluation was conducted on the properties of the particles. The average size of particles appeared to be under 3um with a higher yield compared to particles using the conventional gas atomization method. The melting temperature of fine solder particles using this method was its eutectic temperature, which is same as using the gas–atomized particles. 120um pitch solder bumps from the solder paste using the above mentioned fine solder particles were created on the substrate. As a result of property evaluation, it was turned out that the solder paste created a superior printing shape and coplanarity compared to the conventional paste with gas-atomized particles. In order to investigate the superior printing property generated by the paste with fine solder particles, the rheology of the paste was evaluated.It was verified that the anisotropic shape of particles has contributed to prevent the printed paste from slumping, which has resulted in the improvement of printed shape. It also shows that the filling characteristic of the paste was improved by the smaller particles and the better coplanarity was observed. The importance of finer solder particles for finer pitch assembly will be presented.

Reliability of SAC 105 and SAC1205N under Drop Tests

2016 ◽  
Vol 2016 (1) ◽  
pp. 000106-000110
Author(s):  
Jia-Shen Lan ◽  
Stuwart Fan ◽  
Louie Huang ◽  
Mei-Ling Wu
Keyword(s):  
Fatigue Life ◽  
Solder Joint ◽  
Simulation Model ◽  
Drop Test ◽  
Test Execution ◽  
Fine Pitch ◽  
Mechanical Shocks ◽  
Drop Tests ◽  
Solder Joint Fatigue ◽  
Package Reliability

Abstract In this paper, the solder joint failure and the solder joint fatigue life in the Thin-profile Fine-pitch Ball Grid Array (TFBGA) Package was investigated by performing the drop test, and implementing a simulation model. Owing to the need to meet the increasing demands for functionality, microelectronic package reliability can be compromised and has become the key issue when executing drop tests. During impact in drop test, the deformation of PCB due to bending and mechanical shocks can cause solder joint crack. While this is a well-known issue, observing the solder joint responses during the test execution can be a challenge. Therefore, in this work, a simulation model approach has been developed to investigate the stress and strain of the solder joint during the drop test. In this research, the JEDEC Condition B drop test was simulated, characterized by 1500G peak acceleration and 0.5 ms duration. The drop test simulation model was successful in predicting the solder joint fatigue life with different solder joint materials, such as SAC105 and SAC1205N, while also facilitating result comparison to identify the most optimal structure.

Thermomechanical Design for Fine Pitch 3D-IC Packages

2012 ◽  
Vol 2012 (1) ◽  
pp. 001001-001009 ◽  
Author(s):  
Akihiro Horibe ◽  
Sayuri Kohara ◽  
Kuniaki Sueoka ◽  
Keiji Matsumoto ◽  
Yasumitsu Orii ◽  
...  
Keyword(s):  
Coefficient Of Thermal Expansion ◽  
Low Cost ◽  
High Stress ◽  
High Viscosity ◽  
Thermomechanical Properties ◽  
Design Parameters ◽  
Element Analysis ◽  
Package Design ◽  
Fine Pitch ◽  
Silicon Vias

Low stress package design is one of the greatest challenges for the realization of reliable 3D integrated devices, since they are composed of elements susceptible to failures under high stress such as thin dies, metal through silicon vias (TSVs), and fine pitch interconnections. In variety of package components, an organic interposer is a key to obtain low cost modules with high density I/Os. However, the large mismatch in coefficient of thermal expansion (CTE) between silicon dies and organic laminates causes high stress in an organic package. The major parametric components in 3D devices are dies with /without Cu-TSVs, laminates, bumps, and underfill layers. Especially, the die thicknesses and underfill properties are ones of the parameters that give us some range to control as package design parameters. In general, the underfill material with a high modulus and a low CTE is effective in reducing the stress in solder interconnections between the Si die and the laminate. However, the filler content of underfill materials with such mechanical properties generally results in high viscosity. The use of high viscous materials in between silicon dies in 3D modules can degrade process ability in 3D integration. In this study, we show that the interchip underfills in 3D modules have a wider mechanical property window than in 2D modules even with fine pitch interconnections consisting mostly of intermetallic compounds (IMCs). Also the finite element analysis results show that the optimization of the structural or thermomechanical properties of organic laminates and interchip underfill contributes to reduction of stressing thinned silicon dies which may have some risks to the device performance.

scholarly journals Reliability Study of Solder Paste Alloy for the Improvement of Solder Joint at Surface Mount Fine-Pitch Components

Materials ◽  
2014 ◽  
Vol 7 (12) ◽  
pp. 7706-7721 ◽  
Author(s):  
Mohd Rahman ◽  
Noor Zubir ◽  
Raden Leuveano ◽  
Jaharah Ghani ◽  
Wan Mahmood
Keyword(s):  
Solder Joint ◽  
Solder Paste ◽  
Reliability Study ◽  
Surface Mount ◽  
Fine Pitch
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