Thermal Cycling Simulation and Sensitivity Analysis of Wafer Level Chip Scale Package with Integration of Metal-Insulator-Metal Capacitors

2019 ◽  
Author(s):  
Yi Zhou ◽  
Liangbiao Chen ◽  
Yong Liu ◽  
Suresh Sitaraman
Keyword(s):  
Sensitivity Analysis ◽  
Thermal Cycling ◽  
Wafer Level ◽  
Metal Insulator ◽  
Metal Insulator Metal ◽  
Chip Scale Package

Impact of Conformal Coating Induced Stress on Wafer Level Chip Scale Package Thermal Cycling Performance

2020 ◽  
Vol 33 (2) ◽  
pp. 7-13
Author(s):  
Andy Hsiao ◽  
Mohamed Sheikh ◽  
Karl Loh ◽  
Edward Ibe ◽  
Tae-Kyu Lee
Keyword(s):  
Thermal Cycling ◽  
Salt Spray ◽  
Cycling Performance ◽  
Cycle Performance ◽  
Wafer Level ◽  
Cycle Number ◽  
Chemical Contaminants ◽  
Conformal Coating ◽  
Chip Scale Package ◽  
Tension And Compression

Conformal coating is commonly used for harsh environment to protect electronics from moisture and chemical contaminants. But the stresses imparted by the conformal coating can cause degradation to the package thermal cycle performance. Full coverage of the component with conformal coating material can prevent potential corrosion induced degradation but imply a local compression stress during thermal cycling, resulting a different thermal cycling performance compared to non-coated components. In this study, 8x8mm2 wafer level chip scale packages (WLCSP) were subjected to 5% NaCl aqueous spray test with and without full conformal coating, then thermal cycled from -40ºC to +125ºC. Weibull reliability statistics indicated that fully conformal coated components experience characteristic life cycle number reduction from 404 cycles to 307 cycles, a 24% lifetime reduction, comparing to no conformal coated, no salt spray test applied components. The correlation between crack propagation and localized recrystallization were compared in a series of cross section analyses using polarized imaging and electro-backscattered diffraction, which revealed that the conformal coating induced a z-axis tension and compression strain during thermal cycling, resulting in an accelerated degradation at the solder interconnect. Linear Laser profilometer measurements showed that fully conformal coated samples experienced a higher z-axis height displacement change relative to non-conformal coated samples when exposed to 125 °C with 10 minutes dwell. To prevent this z-axis strain a reworkable edgebond adhesive was applied with full conformal coating configuration, which demonstrate an increase of characteristic lifecycle number to 2783 cycles, suggesting that the mitigation of the z-axis strain can vastly enhance the thermal cycling performance.

LORD SolderBrace™ Wafer Applied Coating for Improved Reliability and Throughput in WLCSP

2013 ◽  
Vol 2013 (1) ◽  
pp. 000055-000060 ◽  
Author(s):  
George Sears ◽  
Guoyun Tian ◽  
Duy Le ◽  
Heather Bradley
Keyword(s):  
Thermal Cycling ◽  
Polymer System ◽  
Cost Effective ◽  
Wafer Level ◽  
Material Technology ◽  
Joint Stress ◽  
Chip Scale Package ◽  
New Material ◽  
Solder Fatigue ◽  
Applied Coating

As more manufacturers look to increase the size of Wafer Level Chip Scale Package (WLCSP) dies and also look to decrease the ball pitch, the susceptibility of the die to fail during thermal cycling and drop shock testing increases. The stress conditions introduced during thermal cycling from the mismatches in Coefficients of Thermal Expansion (CTE) lead to solder fatigue. The failure of WLCSPs during drop shock is found at the solder/pad interface. The general solution to address solder fatigue during thermal cycling and solder joint stress at the copper pad interface has been capillary underfilling the chips after chip attachment. To address these issues, a new material from LORD Corporation – SolderBrace™ wafer applied coating, can be used to partially underfill the WLCSP die at the wafer level. This type of technology can be applied using existing equipment and processing techniques making these materials a more cost effective solution. This new material technology has enabled thermal cycling reliability improvements by replacing the final passivation layer with a new low CTE material as the partial underfill. This wafer applied partial underfill material technology has been successfully used to provide increased thermal cycling and drop shock reliability in WLCSPs using a number of different methods that have been previously described. The method to be discussed in this paper is a production process using a screen printed, photo defined polymer system that does not require any in-process post cure.

Improving WLCSP Reliability Through Solder Joint Geometry Optimization

2013 ◽  
Vol 2013 (1) ◽  
pp. 000546-000550 ◽  
Author(s):  
Boyd Rogers ◽  
Chris Scanlan
Keyword(s):  
Solder Joint ◽  
Thermal Cycling ◽  
Printed Circuit Board ◽  
Geometry Optimization ◽  
Circuit Board ◽  
Wafer Level ◽  
Joint Geometry ◽  
Chip Scale Package ◽  
Large Platform ◽  
Board Level

The effects of solder joint geometry on wafer-level chip-scale package reliability have been studied both through simulations and board level reliability testing. In reliability tests on a 3.9×3.9mm2 die, an enhancement of nearly 2× in thermal cycling reliability was achieved by optimizing the solder joint and under-bump pad stack. In particular, undersizing the printed circuit board pad to produce a more spherical solder joint and reducing the polymer via size under the bump appear to be very important for improving thermal cycling results. Data collected here shows that joint geometry changes can be implemented without compromising drop performance. Methods learned were applied to the qualification of a 6.0×6.0mm2 die, a large platform for WLCSP applications.

Sample Preparation Challenges In WLCSP Epoxy Underfill Coating Removal

2012 ◽  
Author(s):  
Jason H. Lagar ◽  
Rudolf A. Sia
Keyword(s):  
Sample Preparation ◽  
Failure Analysis ◽  
Vital Role ◽  
Fault Isolation ◽  
Wafer Level ◽  
Chip Scale Package ◽  
Coating Removal ◽  
Customer Returns ◽  
Preparation Techniques ◽  
Mechanical Defect

Abstract Most Wafer Level Chip Scale Package (WLCSP) units returned by customers for failure analysis are mounted on PCB modules with an epoxy underfill coating. The biggest challenge in failure analysis is the sample preparation to remove the WLCSP device from the PCB without inducing any mechanical defect. This includes the removal of the underfill material to enable further electrical verification and fault isolation analysis. This paper discusses the evaluations conducted in establishing the WLCSP demounting process and removal of the epoxy underfill coating. Combinations of different sample preparation techniques and physical failure analysis steps were evaluated. The established process enabled the electrical verification, fault isolation and further destructive analysis of WLCSP customer returns mounted on PCB and with an epoxy underfill coating material. This paper will also showcase some actual full failure analysis of WLCSP customer returns where the established process played a vital role in finding the failure mechanism.

Modeling, Fabrication, and Electrical Testing of Metal-Insulator-Metal Diode

2011 ◽  
Author(s):  
Terrance O'Regan ◽  
Matthew Chin ◽  
Cheng Tan ◽  
Anthony Birdwell
Keyword(s):  
Metal Insulator ◽  
Metal Insulator Metal

scholarly journals Hyperspectral Molecular Orientation Mapping in Metamaterials

2021 ◽  
Vol 11 (4) ◽  
pp. 1544
Author(s):  
Meguya Ryu ◽  
Yoshiaki Nishijima ◽  
Shinya Morimoto ◽  
Naoki To ◽  
Tomoki Hashizume ◽  
...  
Keyword(s):  
Molecular Orientation ◽  
Field Enhancement ◽  
Chemical Mapping ◽  
Metal Insulator ◽  
Orientation Mapping ◽  
Metal Insulator Metal ◽  
Finger Printing ◽  
Thermal Emitter ◽  
Ir Bands ◽  
Sub Wavelength

The four polarisation method is adopted for measurement of molecular orientation in dielectric nanolayers of metal-insulator-metal (MIM) metamaterials composed of gold nanodisks on polyimide and gold films. Hyperspectral mapping at the chemical finger printing spectral range of 4–20 μμm was carried out for MIM patterns of 1–2.5 μμm period (sub-wavelength). Overlay images taken at 0,π4,π2,3π4 orientation angles and subsequent baseline compensation are shown to be critically important for the interpretation of chemical mapping results and reduction of spurious artefacts. Light field enhancement in the 60-nm-thick polyimide (I in MIM) was responsible for strong absorption at the characteristic polyimide bands. Strong absorbance A at narrow IR bands can be used as a thermal emitter (emittance E=1−R), where R is the reflectance and A=1−R−T, where for optically thick samples the transmittance is T=0.

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