• Journal of the Microelectronics and Packaging Society
• /
• v.18 no.4
• /
• pp.85-90
• /
• 2011

With regard to reliability of solder joint, the significant failures include open defects that occurs from alignment problem, Head in Pillow by PCB's warpage, the crack of solder by CTE mismatch, and the crack of IMC layer by mechanical impact. Especially as PCB down-sizing and surface finish is under progress, brittle failure of IMC layer between solder bump and PCB pad becomes a big issue. Therefore, it requires enhancing the level of difficulty in the existing assessment method and improving the measurement through the study on the mechanism of IMC formation, growth and brittle failure. Under this circumstance, this study is intended to suggest the direction of research for improving the reliability on the crack such as improvement of IMC brittle fracture.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.39-39
• /
• 2008

이동통신 시스템의 소형화, 다기능화 추세에 따라 이동통신 부품들의 모듈화, 고집적화 추세로 급진전되고 있어, 고집적 세라믹 기판 모듈 제작을 위한 핵심공정 기술인 그린시트의 층간 정밀도 및 소성후 수축율 제어의 중요성이 증대되고 있다. 본 연구에서는 일축가압 이용한 PAS(Pressure Assisted Sintering) 법과 Al2O3를 희생층으로 이용한 Constrained Sintering법을 혼합하여 저온 동시소성 세라믹 기판의 x-y 축 수축율을 zero로 제어하고자하였다. $Al_2O_3$/LTCC/$Al_2O_3$인 샌드위치 구조로 세라믹 시트를 적층하여 Load 값과, LTCC 두께에 따른 x-y축, z축 소성 수축율 및 Edge Curvature의 Radius와 warpage 현상을 관찰하고, 이때 미세구조 및 밀도를 측정하였다. 그 결과 symmetic한 구조일 때 소성온도 $900^{\circ}C$에서 $Al_2O_3$ 두께가 $30{\mu}m$ 이상일 때 LTCC의 글라스가 $Al_2O_3$에 Infiltration 되는 두께는 $30{\mu}m$를 나타내었다. 또한 $Al_2O_3$ 두께 $500{\mu}m$, LTCC 두께 $2,000{\mu}m$, Load값이 800g/$cm^2$ 일 때 x-y 축 수축율<1%, z축 수축율 40%, 소결밀도는 2.99g/$cm^3$로 우수한 무수축 기판 특성을 나타내었다.

• Journal of the Microelectronics and Packaging Society
• /
• v.15 no.1
• /
• pp.7-18
• /
• 2008

This paper reviews the current development of an ultra-slim SiP for Radio Frequency (RF) application, in which three flip chips, additional passive components and Surface Acoustic Wave (SAW) filters are integrated side-by-side. A systematic investigation is carried out for the design optimization, process and reliability improvement of the package, which comprises several aspects: a design study based on the 3D thermo-mechanical finite element analysis of the packaging, the determination of stress, warpage distribution, critical failure zones, and the figuration of the effects of material properties, process conditions on the reliability of package. The optimized material sets for manufacturing process were determined which can reduce the number of testing samples from 75 to 2. In addition the molded underfilling (MUF) process is proposed which not only saves one manufacturing process, but also improves the thermo-mechanical performance of the package compared with conventional epoxy underfilling process. In the end, JEDEC's moisture sensitivity test, thermal cycle test and pressure cooker tests have also been carried out for reliability evaluation. The test results show that the optimized ultra-slim SiP has a good reliability performance.

• Journal of the Microelectronics and Packaging Society
• /
• v.23 no.4
• /
• pp.43-48
• /
• 2016

3-Dimensional System in Package (3-D SiP) structure (Amkor calls it mPossum-molded Possum) using double side Surface Mount Technology (SMT) and double side molding was evaluated in order to achieve small/thin form factor as well as good functionality by integration and double side layout. As the new platform on laminate substrate basis, molding process was challenge in mold flow balance at top and bottom side and package warpage control over the overall assembly process. There were two types of different molding process evaluated with 1) 1-step molding which was done at both side at the same time and 2) 2-step molding which was done at the conventional molding process twice. Mold simulation helped to narrow down the material selections and parameters available before actual sample build. There were many challenges for this first trial in design/ parameter and material types but optimized them to enable this structure.

• Journal of the Microelectronics and Packaging Society
• /
• v.20 no.1
• /
• pp.21-26
• /
• 2013

This study presents new analysis method to predict bending behavior of packaging substrate structure by comparing finite element method simulation and measured curvature using 3D scanner. Packaging substrate is easily bent and deflected while undergoing various processes such as curing of prepreg and copper pattern plating. We prepare specimens with various conditions and measure contours of each specimen and compute the residual stresses on deposited films using analytical solution to find the principle of bending. Core and prepreg in packaging substrate are made up of resin and bundles of fiber which exist orthogonally each other. Anisotropic material properties cause peculiar bending behavior of packaging substrate. We simulate the bending deflection with finite element method and verify the simulated deflection with measured data. The plating stress of electrodeposited copper is about 58 MPa. The curing stresses of solder resist and prepreg are about 13 MPa and 6.4 MPa respectively in room temperature.

• Composites Research
• /
• v.29 no.1
• /
• pp.7-15
• /
• 2016

The quality of polymeric automotive parts depends highly on an injection molding process, which causes various defects, such as warpage, sink marks, weld lines, shrinkage, residual stress, etc. This study is to determine the optimum processing parameters, such as packing pressure, mold temperature, melting temperature, and packing time for the manufacture of polycarbonate buttons in cars on the basis of FEM, the Taguchi method, and analysis of variance (ANOVA). As a result, the optimum processing parameters of buttons made of polycarbonate material were obtained as follows: 140 MPa of packing pressure, $105^{\circ}C$ of mold temperature, $292.5^{\circ}C$ of melting temperature and 1 second of packing time. A gain of S/N (signal to noise) ratio, 10.2, was obtained with the optimum values. Moreover, the melting temperature was found to be the most significant factor followed by the mold temperature.

• Composites Research
• /
• v.33 no.4
• /
• pp.220-227
• /
• 2020

When curing the composite, the fibers have little thermal deformation, but the resin changes its properties with time and temperature, which leads to residual stress in the product. Residual stress is caused by the difference in the coefficient of thermal expansion of the fibers and resin during the curing process and the chemical shrinkage of the resin. This difference causes thermal deformation such as spring-in and warpage. Thermal deformation of composite structure is important issue on quality of product, and it should be considered in manufacturing process. In this study, a subroutine was developed to predict thermal deformation by applying 3-D viscoelastic model. The finite element analysis was verified by comparing the results of the plate analysis of the 2-D viscoelastic model. Spring-in of L-shaped structure was predicted and analyzed by applying the 3-D viscoelastic model.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.16 no.6
• /
• pp.63-68
• /
• 2017

The purpose of this study is to improve the whitening phenomenon around the PET preform gate for blow molding. CAE analysis of plastic injection molding has been applied to design of preform shape and select the injection molding conditions. A ceramic insulation gate with lower thermal conductivity than metal is applied to improve the whitening phenomenon created around the gate in the injection molding process. According to the results of CAE analysis, the warpage deformation at the square corner was estimated to be about 0.34 mm at the bottom. From the results of the temperature history analysis, it was confirmed that the resin near the gate cooled more rapidly than the cavity. Ceramic insulated gates were fabricated to reduce the cooling rate and experiments were conducted to confirm the effectiveness of the whitening phenomenon improvement. As a result of the ceramic insulation gate experiment, it was confirmed that the whitening phenomenon was significantly reduced around the gate.

• Journal of the Microelectronics and Packaging Society
• /
• v.16 no.2
• /
• pp.11-19
• /
• 2009

Thermo-mechanical behaviors of wire-bond plastic ball grid array (WB-PBGA) package assemblies are characterized by high-sensitivity moire interferometry. Using the real-time moire setup, fringe patterns are recorded and analyzed for several temperatures. Experiments are conducted for three types of WB-PBGA package that have full grid pattern and perimeter pattern with/without central connections. Bending deformations of the assemblies and average strains of the solder balls are investigated, with an emphasis on the effect of solder interconnection grid patterns, Thermal strain distributions and the location of the critical solder ball in package assemblies are quite different with the form of solder ball grid pattern. For the WB-PBGA-PC, The largest of effective strain occurred in the inner solder ball of perimeter closest to the chip solder balls. The critical solder ball is located at the edge of the chip for the WB-PBGA-FG, at the most outer solder ball of central connections for the WB-PBGA-P/C, and at the inner solder ball closest to the chip for the WB-PBGA-P.

• Journal of the Microelectronics and Packaging Society
• /
• v.23 no.3
• /
• pp.43-49
• /
• 2016

Reliability characteristics of thin package-on-packages were evaluated using T/H (temperature/humidity) test at $85^{\circ}C/85%$ for 500 hours, TC (temperature cycling) test at $-40{\sim}100^{\circ}C$ for 1,000 cycles, and HTS (high temperature storage) test at $155^{\circ}C$ for 1,000 hours. The average resistance of the solder-bump circuitry between the top and bottom packages of 24 package-on-package (PoP) samples, which were processed using polyimide thermal tape, was $0.56{\pm}0.05{\Omega}$ and quite similar for all 24 samples. Open failure of solder joints did not occur after T/H test for 500 hours, TC test for 1,000 cycles, and HTS test for 1,000 hours, respectively.