• Proceedings of the KWS Conference
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• 2006.05a
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• pp.21-23
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• 2006

The microstructural investigation and thermo-mechanical reliability evaluation of the Sn-3.0Ag-0.5Cu solder bumped flip chip package were carried out during the thermal shock test of the package. In the initial reaction, the reaction product between the solder and Cu mini bump of chip side was Cu6Sn5 layer, while the two phases which were (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 were formed between the solder and Ni-P layer of the package side. The cracks were occurred at the corner solder joints after the thermal shocks of 400 cycles. The primary failure mechanism of the solder joints in this type of package was confirmed to be thermally activated solder fatigue failure.

• Current Optics and Photonics
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• v.1 no.4
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• pp.389-395
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• 2017

This paper investigates a method to improve the lighting performance of white light-emitting diodes (WLEDs), which are packaged using two separate remote phosphor layers, a yellow-emitting YAG:Ce phosphor layer and a red-emitting ${\alpha}-SrO{\cdot}3B_2O_3:Sm^{2+}$ phosphor layer. The thicknesses of these two layers are $800{\mu}m$ and $200{\mu}m$, respectively. Both of them are examined in conditions where the average correlated color temperatures (CCT) are 7700 K and 8500 K. For this two-layer model, the concentration of red phosphor is varied from 2% to 30% in the upper layer, while in the lower layer the yellow phosphor concentration is kept at 15%. It was found interestingly that the lighting properties such as color rendering index (CRI) and luminous flux are enhanced significantly, while the color uniformity is maintained in a relatively close range to the one of one-layer configuration (measured at the same correlated color temperature). Besides, the transmitted and reflected light of each phosphor layer are revised by combining Kubelka-Munk and Mie-Lorenz theories. Through analysis, it is demonstrated that the packaging configuration of two-layer remote phosphor that employs red-emitting ${\alpha}-SrO{\cdot}3B_2O_3:Sm^{2+}$ phosphor particles provides a practical solution for general WLEDs lighting.

• Composites Research
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• v.34 no.1
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• pp.47-50
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• 2021

In this paper, the Curing process for Epoxy Molding Compound (EMC) Package was developed by comparing the performance of the EMC/Cu Bi-layer package manufactured by the conventional Hot Press process system and Carbon Nanotubes (CNT) Heater process system of the surface heating system. The viscosity of EMC was measured by using a rheometer for the curing cycle of the CNT Heater. In the EMC/Cu Bi-layer Package manufactured through the two process methods by mentioned above, the voids inside the EMC was analyzed using an optical microscope. In addition, the interfacial void and warpage of the EMC/Cu Bi-layer Package were analyzed through C-Scanning Acoustic Microscope and 3D-Digital Image Correlation. According to these experimental results, it was confirmed that there was neither void in the EMC interior nor difference in the warpage at room temperature, the zero-warpage temperature and the change in warpage.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.4
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• pp.69-74
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• 2010

A new package substrate for dynamic random access memory(DRAM) devices has been developed using selective aluminum anodization. Unlike the conventional substrate structure commonly made by laminating epoxy-based core and copper clad, this substrate consists of bottom aluminum, middle anodic aluminum oxide and top copper. Anodization process on the aluminum substrate provides thick aluminum oxide used as a dielectric layer in the package substrate. Placing copper traces on the anodic aluminum oxide layer, the resulting two-layer metal structure is completed in the package substrate. Selective anodization process makes it possible to construct a fully filled via structure. Also, putting vias directly in the bonding pads and the ball pads in the substrate design, via in pad structure is applied in this work. These arrangement of via in pad and two-layer metal structure make routing easier and thus provide more design flexibility. In a substrate design, all signal lines are routed based on the transmission line scheme of finite-width coplanar waveguide or microstrip with a characteristic impedance of about $50{\Omega}$ for better signal transmission. The property and performance of anodic alumina based package substrate such as layer structure, design method, fabrication process and measurement characteristics are investigated in detail.

• Computers and Concrete
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• v.33 no.1
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• pp.13-25
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• 2024

In this study, contact analysis in a functionally graded (FG) layer loaded with two circular punches is solved using the finite element method (FEM). The problem is consisted of a functionally graded layer that resting on an elastic semi-infinite plane and is loaded with two rigid punches of circular geometry. External loads P and Q are transferred to the layer via two rigid punches. The finite element model of the functionally graded layer is created using the ANSYS package program and a 2-dimensional analysis of the problem is analyzed. The contact lengths, obtained as a result of the analysis are compared with the analytical solution in the literature. In the study, the effects of parameters such as distances between punches, loads, inhomogenity parameter on contact zones, initial separation loads and distances, normal stresses, stresses across depth and contact stresses are investigated. As a result, in this study, it can be said that the magnitude of the stresses occurring in the FG layer is less than the homogeneous layer, therefore the life of FG materials will be longer than the homogeneous layer. When the distance between the punches is 2.25, the initial separation distance is 6.98, and when the distance between the punches is 4, the initial separation distance decreases to 6.10. In addition, when the load increased in the second punch, the initial separation load decreased from 55 to 18. The obtained results are presented in the form of graphs and tables.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.1
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• pp.75-81
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• 2015

In this paper, numerical analysis by finite element method and parameter design by the Taguchi method were used to reduce warpage of a two passive components embedded double side substrate for PoP(Package on Package). The effect of thickness of circuit layers (L1, L2) and thickness of solder resist (SR_top, SR_BTM) were analyzed with 4 variations and 3 levels(minimum, average and maximum thickness) to find optimized thickness conditions. Also, paste effect of solder resist on unit area of top surface was analyzed. Finally, experiments was carried out to prove numerical analysis and the Taguchi method. Based on the numerical and experimental results, it was known that circuit layer in ball side of substrate was the most severe determining deviation for reducing warpage. Buried circuit layer in chip side, solder resist and were insignificant effects on warpage relatively. However, warpage decreased as circuit layer in ball side thickness increased but effect of solder resist and circuit layer in chip side thickness were conversely.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4757-4761
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• 2012

LED chip on board(COB) package has been fabricated using aluminum substrate and aluminum anodization process. An alumina layer, used as a dielectric in COB substrate, is produced on aluminum substrate by selective anodization process. Also, selective anodization process makes it possible to construct a thermal via with a fully-filled via hole. Two types of the COB package are fabricated in order to analyze the effects of their substrate types on thermal resistivity and luminous efficiency. The aluminum substrate with the thermal via shows more improved measurement results compared with the alumina substrate. These results demonstrate that selective anodization process and thermal via can increase heat dissipation of COB package in this work. In addition, it is proved experimentally that these parameters also can be enhanced using efficient layout of multiple chip in the COB package.

• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.370-376
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• 2014

We optimized the design of the flat encapsulant of a light-emitting diode (LED) package to obtain higher light output power (LOP), both by experiment and simulation using three-dimensional ray-tracing software. In the experiment, the refractive index of the encapsulant was varied (1.41 and 1.53). In addition, double-layer structures with these refractive indices (1.41/1.53) were investigated by varying the shape of the interface between the two among flat, concave, and convex. The experiments showed that the LOP of the double-layer encapsulant with convex interface increased by 13.4% compared to the single-layer encapsulant with a refractive index 1.41, which was explained by the increase of the light extraction efficiency (LEE) in connection with the increase of the critical angle (${\theta}_c$) and the decrease of the Fresnel reflection.

• Structural Engineering and Mechanics
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• v.82 no.3
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• pp.401-416
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• 2022

The aim of this study is to examine the frictionless double receding contact problem for two functionally graded (FG) layers pressed with a uniformly distributed load and resting on a homogeneous half plane (HP) using analytical and numerical methods. The FG layers are made of a non-homogeneous material with an isotropic stress-strain law with exponentially varying properties. It is assumed that the contact at the FG layers and FG layer-HP interface is frictionless. The body force of the FG layers and homogeneous HP are ignored in the study. Firstly, an analytical solution for the contact problem has been realized using the theory of elasticity and the Fourier integral transform techniques. Then, the problem modeled and two-dimensional analysis was carried out by using the ANSYS package program based on FEM. Numerical results for contact lengths and contact pressures between FG layers and FG layer-HP were provided for various dimensionless quantities including material inhomogeneity, distributed load width, the shear module ratio, and the heights of the FG layers for both methods. The results obtained using FEM were compared with the results found using the analytical formulation. It was found that the results obtained from analytical formulation were in perfect agreement with the FEM study.

• Steel and Composite Structures
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• v.50 no.1
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• pp.77-87
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• 2024

In this study, the two-dimensional crack problem was investigated by using the finite element method (FEM)-based ANSYS package program and the artificial neural network (ANN)-based multilayer perceptron (MLP) method. For this purpose, a half-infinite functionally graded (FG) layer with a crack pressed through two rigid blocks was analyzed using FEM and ANN. Mass forces and friction were neglected in the solution. To control the validity of the crack problem model exercised, the acquired results were compared with a study in the literature. In addition, FEM and ANN results were checked using Root Mean Square Error (RMSE) and coefficient of determination (R²), and a well agreement was found. Numerical solutions were made considering different geometric parameters and material properties. The stress intensity factor (SIF) was examined for these values, and the results were presented. Consequently, it is concluded that the considered non-dimensional quantities have a noteworthy influence on the SIF. Also FEM and ANN can be logical alternative methods to time-consuming analytical solutions if used correctly.