Rong-Sheng Chen

A Note on the Effects of Voids Upon the Hygral and Mechanical Properties of AS4/3502 Graphite/Epoxy

This paper presents the results of an experimental investigation of the effects of voids upon the hygral and mechanical properties of AS4/3502 graphite/epoxy. Simple uniaxial tension tests were employed to determine the effects of voids upon ply moduli E 11, E 22 and G 12, and the Poisson ratio ν12. The matrix dominated moduli E 22 and G12 were found to depend significantly upon void content while little dependence was noted for the fiber dominated properties E 11 and ν12. Moisture conditioning experiments showed that both the rate and the equilibrium level of moisture sorption depend upon void content. In addition, non-Fickian diffusion anomalies were observed in high void content specimens while specimens with low void content displayed classical Fickian behavior.

Application of Taguchi's method on the optimal process design of an injection molded PC/PBT automobile bumper

Abstract The manufacturing process of an injection molded polycarbonate/ poly(butylene terephthalate) automobile bumper was optimized, using Taguchis method, to eliminate silver streaks on the surface of the product. First, a set of process factors was selected and a preliminary experiment was conducted with an L 12 orthogonal array to screen the significant factors, check the validity of the data fitting model, and predict an improved process condition to overcome the filling difficulties. Second, using the selected control factors, a principal experiment was conducted with an L 18 orthogonal array to predict an optimal process condition that solve the quality problem. Finally, the predicted process condition was tested on an 2500-ton injection molding machine to confirm the prediction. The results reveal that the main factors that directly relate to the generation of silver streaks are the mold temperature, the fill time, the fill/ postfill switch over control, and the injection rate.

Transient Submodeling Analysis for Board-Level Drop Tests of Electronic Packages

We present in this paper a submodeling analysis procedure capable of solving transient mechanical responses of board-level electronic packages subjected to drop impact loads, involving large deformations and nonlinear elastoplastic constitutive relationships for the solder alloy. This paper is focused on the verification of this submodeling analysis procedure and to investigate solution deviations caused by several abbreviated global models that involve simplified geometry or material properties for the solder joints

Response spectra analysis for undamped structural systems subjected to half-sine impact acceleration pulses

In this paper, we derive closed-form solutions for transient structural responses of an undamped single degree of freedom structural system subjected to an impact acceleration pulse of a half-sine waveform. The application of the response spectra to a specific printed circuit board is demonstrated. An insight is also provided to analyzing transient structural responses of a multiple degrees of freedom structural system led by the same type of impact acceleration pulses through modal superposition.

Optimal dimension of PQFP by using Taguchi method

Abstract This paper addresses the use of finite element techniques and Taguchi method to optimize package design for plastic quad flat packages (PQFP) with and without a heat slug assembled. Warpage in both types of PQFPs during the curing process of temperature changing from 175°C to room temperature was simulated by using three-dimensional finite element models. Taguchi method was applied to both models to isolate the major control factors that minimize package warpage. Results of this analysis suggest that PQFPs without heat slug should keep the thickness of both mold compound and die pad as smaller as possible. For PQFPs with heat slug assembled, it was found that larger Young’s modulus of heat slug material and smaller values of temperature coefficient of expansions of mold compound, die pad, and die attachment would yield the least warpage.

Finite element model verification for packaged printed circuit board by experimental modal analysis

In this work, the experimental modal analysis (EMA) was performed to establish an equivalent finite element (FE) model for a standard Joint Electron Device Engineering Council (JEDEC) drop test printed circuit board (PCB) mounted with packages in a full array. Material properties of the equivalent FE model of the packaged PCB were calibrated through an optimization process with respect to natural frequencies based on EMA results obtained with a free boundary condition. The model was then applied to determine screwing tightness of the packaged PCB corresponding to a fixed boundary condition with the four corners of the PCB constrained, as defined by JEDEC for a board-level drop test. Modal damping ratios of the packaged PCB were also provided.

Packaging parameter analysis and optimization design on solder joint reliability for twin die stacked packages by variance in strain energy density (SED) of each solder joint

Abstract In accordance with vigorous development of the electronic product market as well as the consumers’ preference for smaller scales, the structure of 3D stacked die package rapidly becomes popular. Hereafter the stacked process of the silicon dies always makes the coupling effect among materials more complicated. Such an issue has been seriously paid attention to and becomes a critical problem to be solved for the product reliability. In this paper, the ANSYS software is adopted to analyze a twin die stacked package under a cyclic thermal loading condition. The viscoplastic finite element analysis and the Darveaux theory are applied to investigate the solder joint reliability (SJR) of the stacked die package. This research will verify a significant dependence between the solder joint fatigue life of the stacked die package and the distribution of the accumulated strain energy density (SED) on the solder joints by proposing a viewpoint of the variance of the strain energy density among solder joints for a 3D-Slice model.

The Effects of Moisture upon the Optimal Temperature Path of the Viscoelastic Symmetric Composite Laminates after Post Cure

Inheriting previous studies on the optimal cool-down path of the compos ite laminate, this article incorporates the consideration of a new element-humidity-to analyze the residual stresses which develop in a composite material laminate after termi nation of cool down due to further exposure to humid environment.

A tiny plastic package of pressure sensors fabricated using the lithographic dam-ring approach

This study presents a novel plastic package for piezoresistive pressure sensors. A photoresist dam-ring patterned using the lithographic process is spin-coated on a piezoresistive pressure sensor to define a sensing channel in the pressure sensor package. Fluid epoxy molding encapsulates the pressure sensor and exposes the sensing channel during a high-temperature molding process at 165°C. Experimental observations reveal that the silicon membrane of the pressure sensor is completely free of epoxy molding compound (EMC) contamination after the transfer molding process. The effectiveness of the dam-ring in shielding the silicon membrane of the pressure sensor during the molding process was confirmed. The packaged pressure sensor exerts a thermo-mechanical stress on the silicon membrane of the pressure sensor, resulting in an undesired output voltage drift. However, employing a package design with a large sensing channel opening can reduce the effect of package-induced stress. The proposed packaging scheme was a small package volume and surface-mount device (SMD) compatible features, making it suitable for portable commercial devices.

Packaging Parameter Analysis on Solder Joint Reliability for Twin Die Stacked Packages by Variance in Strain Energy Density of Each Solder Joint

In this paper, the ANSYS 7.0 software is applied to analyze a twin die stacked package under a cyclic thermal loading condition. The viscoplastic finite element analysis and the Darveaux theory are applied to investigate the solder joint reliability of the stacked die package. Accordingly, a significant dependence between the fatigue life of the solder joint for the stacked die package and the distribution of the accumulated strain energy density on the solder is verified by proposing a viewpoint of the variance of the strain energy density among solders in accordance with a 3-D slice model. As a result, for enhancing solder joint reliability of the twin die stacked package, it is found that thinner top die, thicker bottom die, thicker substrate, and thinner PCB are preferred in the aspect of geometry configurations; while the coefficient of thermal expansion (CTE) of molding compound near upon CTE of substrate which causes minimum package warpage, and lower molding compound Youngs modulus and lower substrate Youngs modulus are preferred in the aspect of material properties