Milpitas, CA, United States
Milpitas, CA, United States

Time filter

Source Type

Suhir E.,Physical science and Engineering Research Division | Suhir E.,University of California at Santa Cruz | Suhir E.,University of Maryland University College | Suhir E.,Vienna University of Technology | And 3 more authors.
Journal of Applied Mechanics, Transactions ASME | Year: 2013

Low-temperature thermally induced stresses in a trimaterial assembly subjected to the change in temperature are predicted based on an approximate structural analysis (strength-of-materials) analytical ("mathematical" ) model. The addressed stresses include normal stresses acting in the cross-sections of the assembly components and determining their short- and long-term reliability, as well as the interfacial shearing and peeling stresses responsible for the adhesive and cohesive strength of the assembly. The model is applied to a preframed crystalline silicon photovoltaic module (PVM) assembly. It is concluded that the interfacial thermal stresses, and especially the peeling stresses, can be rather high, so that the structural integrity of the module could be compromised, unless appropriate design for reliability measures are taken. The developed model can be helpful in the stress analysis and physical (structural) design of the PVM and other trimaterial assemblies. Copyright © 2013 by ASME.


Ha T.H.,KLA Tencor | Wu C.-T.,Purdue University | Majewicz P.,Flextronics Inc. | Bengtson K.R.,Hewlett - Packard | Allebach J.P.,Purdue University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

The quality of images of objects with significant 3D structure, captured at close range under a flash, may be substantially degraded by glare and shadow regions. In this paper, we introduce an imaging system and corresponding algorithm to address this situation. The imaging system captures three frames of the stationary scene using a single camera in a fixed position, but an illumination source in three different positions, one for each frame. The algorithm includes two processes: shadow detection and image fusion. Through shadow detection, we can locate the area of shadows. After getting the shadow maps, we generate a more complete final image by image fusion. Our experimental results show that in most cases, the shadow and glare are markedly reduced. © 2013 SPIE.


Lei Y.,Purdue University | Majewicz P.,Flextronics Inc. | Bengtson K.R.,Hewlett - Packard | Li L.,Hewlett - Packard | Allebach J.P.,Purdue University
International Conference on Digital Printing Technologies | Year: 2012

The use of mobile phone camera technology in systems for capture of documents or 3D objects by a single exposure is becoming increasingly popular. Compared to conventional flat-bed scanner technology, such systems pose special image quality concerns due to the relatively uncontrolled environment within which they operate. In particular, it is not possible to control ambient lighting, and there is more variability with the internal illumination source and the placement of the document or object to be captured. This leads to higher levels of noise and greater non-uniformity across the image plane. In addition, since the underlying camera and internal illumination technologies are inherently low-cost, each unit is designed to operate closer to the threshold of acceptable quality and there is greater unit-to-unit variability. This makes it necessary to inspect each individual product for acceptable image quality as it comes off the manufacturing line. In order to maintain efficiency in the manufacturing process, this inspection must be completed as autonomously as possible. This paper proposes a specially designed hybrid target and an automatic analysis tool for image quality inspection of camera-based document/object capture systems. The tool can be used in both the research laboratory and on the manufacturing line. The criteria and thresholds for final production are chosen based on visual inspection of image data from hundreds of preproduction units. Currently, our solution is used in mass manufacturing, and shows effectiveness in failing units with low image quality, as well as saving manufacturing time. ©2012 Society for Imaging Science and Technology.


Suhir E.,University of California at Santa Cruz | Shangguan D.,Flextronics Corporation | Bechou L.,University of Bordeaux 1
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

Thermally induced stresses in a pre-framed silicon-based photovoltaic module (PVM) are addressed using analytical ("mathematical") model. The emphasis is on the role of the backsheet thickness on the induced stresses. The developed model is the modification of some predictive models suggested earlier for various electronic and opto-electronic assemblies and packages. The considered stresses include normal stresses acting in the cross-sections of the assembly components (glass, encapsulant with embedded Si devices, and the backsheet) and the interfacial (shearing and peeling) stresses. We show that the normal stresses in the glass increase, and the stresses in the encapsulant composite and in the backsheet decrease with an increase in the backsheet thickness, and that very thin backsheets result in high stresses in it. The interfacial shearing stresses at the glass-encapsulant and at the encapsulant-backsheet interfaces increase with an increase in the backsheet thickness. This means that, if thick backsheets are considered, special attention should be paid to the adhesive strength at these interfaces. We found also that the normal bending stresses in the glass were significant and overwhelmed the compressive stresses in this material. Because of that, the total tensile stress in the glass increases considerably with an increase in the backsheet thickness. Since glass is a brittle material, special attention should be paid therefore that this stress does not exceed the allowable value. The total maximum normal stress in the backsheet material, on the contratrry, reduces with an increase in the backsheet thickness, and is due primarily to the axial, not bending, stresses. Based on the computed data, it is concluded that the thermal stresses of all the categories might be quite high, so that the PVM's structural integrity might be compromised, unless adequate design-for-reliability (DfR) measures are taken. The developed model can be helpful in the stress-analysis and physical design of the PVMs of the type in question. It can be used also in other areas of engineering, where ti-material assemblies subjected to thermal stresses are employed. © 2012 SPIE.


O'Hara G.,Flextronics Corporation | Vandiver M.,Flextronics Corporation | Crilly J.,Flextronics Corporation | Brinkhoff N.,North Star Imaging
SMT Surface Mount Technology Magazine | Year: 2012

Flextronics Inc. and North Star Imaging Inc. are working together to correlate current X-ray imaging and cross-section analysis of BGA voiding with state-of-the-art high-resolution CT scan imaging. The group hopes to validate the void measurements obtained from non-destructive imaging techniques with the physically measured void measurements of cross-sectioning and to characterize void properties before and after reflow.


Raju R.,Flextronics Inc. | Asokan C.Raj.,k-Technology
2012 National Conference on Communications, NCC 2012 | Year: 2012

In this paper a detailed study of the effect of strip line on truncated ground plane of a small Ultra Wide Band (UWB) patch antenna is described. The radiator and ground plane of the antenna are etched onto a piece of Printed Circuit Board (PCB) with an overall size of 25x25x1.5 mm. The results obtained from the simulation of the proposed antenna are compared with that of the results of a patch having regular truncated ground plane. The simulation results show that the antenna not just achieved a broad operating bandwidth of 6.2-11.6 GHz for a 10-dB return loss; in addition it provided a constant return loss of -20 dB for a bandwidth of 6.4 - 10.6 GHz, this indicated a constant Gain for the entire UWB. © 2012 IEEE.


O'Hara G.,Flextronics Corporation | Vandiver M.,Flextronics Corporation | Crilly J.,Flextronics Corporation | Brinkhoff N.,Flextronics Corporation
IPC APEX EXPO 2012 | Year: 2012

A joint project between Flextronics Inc. and North Star Imaging Inc. is being conducted to correlate current x-ray imaging and cross-section analysis of BGA voiding with state of the art high resolution CT-Scan imaging. Our primary objective is to validate the void measurements obtained from non-destructive imaging techniques, with the physically measured void measurements of cross sectioning. A secondary goal is to characterize void properties before and after reflow. Typical AXI inspection equipment provides one to three horizontal planes of reference for BGA void measurements. CT Scan imaging provides a full 3D volumetric representation of the BGA void, allowing for size, volume, and void position data. Information that can be used in failure analysis and process characterization projects, without physical destruction of the printed circuit board. Five 50.0 mm FCBGA devices and five 52.5mm FCBGA devices, with known voiding, are being used in the study. The voiding for each device has been measured on a 3D AXI machine (Figure 1), a2D off-axis high resolution x-ray machine (Figure 2), and CT-Scan system (Figure 3). The devices will then be placed and reflowed onto printed circuit boards. After reflow, all the voiding will be measured again using each piece of equipment. In addition, select voids will be cross-sectioned, polished, and measured using a high magnification digital microscope and correlated to the other x-ray imaging tools.

Loading Flextronics Inc. collaborators
Loading Flextronics Inc. collaborators