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A Research Effort to Evaluate the Effectiveness of Conformal Coatings and to Determine the Probability of Tin Whisker Induced Shorts By Dr. H. Aglan, Tuskegee University David Burdick, The Boeing Co.

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A Research Effort to Evaluate the Effectiveness of Conformal Coatings

and to Determine the Probability of Tin Whisker Induced Shorts

By Dr. H. Aglan, Tuskegee University

David Burdick, The Boeing Co.

TUSKEGEE UNIVERSITY

1881

Overview

The Calling of Education at Tuskegee: a holistic approach for performance-ready talent:

� HEAD - requisite knowledge for one’s field (Competence)

� HANDS - ready and willing to translate into practical experience within a specified field (Capability)

� HEART - personal sense of passion and integrity toward one’s work (Character)

Our Philosophy

3

Presenter
THERE ARE FEW PEOPLE WHO HAVE NOT HEARD OF TUSKEGEE UNIVERSITY (INSTITUTE) THIS MESSAGE CAPTURES THE HISTORY (POSITIVE AND NEGATIVE)

Tuskegee University Overview

¾Independent and state-related institution of higher education ¾The academic programs are organized into five colleges and two schools ¾The curricula for these colleges and schools currently offer over 50 degrees including 39 Bachelor's, 13 Master's, 3 Doctor's of Philosophy: Materials Science and Engineering, Integrative Bio-Sciences, Interdisciplinary Pathobiology and the Doctor of Veterinary Medicine. ¾Tuskegee enrolls more than 3,000 students and employs approximately 900 faculty and support personnel. ¾Physical facilities include more than 5,000 acres of forestry and a campus on which sits more than 100 major buildings and structures.

Aerospace: experimental aerodynamics, vortex-dominated flows, flight simulation, configuration aerodynamics, human interface.

Chemical: bio-fluidics, corrosion, carbon capture, bio-fuels, electrochemical catalysis, environmental, water & wastewater, nuclear reactor materials, bio-chemical engineering, chemical process modeling.

Electrical: electronic warfare and technology; systems engineering; control systems, wireless sensors and data gathering networks, information assurance; integrated circuits; cyber; power/energy.

Mechanical: fracture and fatigue evaluation, proton and ion conductive membranes, corrosion and coatings, environmental aging of materials, dislocation dynamics in materials, fuel cells.

Materials Science & Engineering: synthesis and chemical analysis of materials, processing/manufacturing of bio materials, performance and nondestructive evaluation, and modeling.

College of Engineering-Core Strengths & Capabilities

5

Summary of College of Engineering-Highlights

¾Number of students: ~650 undergraduate and ~50 graduate ¾ Number of Faculty: 35 ¾Annual Research Awards: ~ $ 12 M

CE 2014-2015 Publications

Departments AE Ch.E EE MSEG ME Refereed

Publications 8 17 10 25 25 85 Book Chapters 0 0 0 2 0 2 Non -Refereed 1 0 2 21 2 26

National Conferences 5 11 4 36 9 65

International Conf. 0 3 10 23 4 40 Total 14 31 26 107 40 218

Selective Research Capabilities

Additive Manufacturing

� Tuskegee is a member of the Institute for Advanced Composite Manufacturing Innovation (IACMI), a consortium consisting of Oak Ridge National Lab, UTK, Industrial and Academic Institutions.

� Tuskegee 3D Printing Research and Educational Facilities: ¾ 3D printing of antimicrobial packaging films and tissue

scaffolds ¾ Developing of polymeric based filaments with various nano

and micro additives for 3D printing ¾ Tuskegee/Chevron Additive Manufacturing Laboratory (part

design, 3D scanning and reverse engineering, functional models)

8

3D printing head with polymer solution

3D printed anti microbial films with silver nanoparticles for wound healing

3D film Printing for Biomedical Applications

9

Manufacturing of Printer Mediums (functionalized materials)

10

Detection and Assessment of Low Cycle Fatigue Damage

Fatigue Crack Propagation Kinetics of Bainitic and Pearlitic Rail Steels

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

0 10 20 30 40 50 60 70Energy Release rate, J* (kJ/m2)

Cra

ck G

row

th r

ate,

da/

dN

(m/c

ycle

)

Bainitic Pearlitic

Fatigue crack propagation kinetics correlation with fracture surface morphology, fast crack region

bainitic

pearlitic

Rail Steel Repairs

Rail Steel after Welding

Slot weld Continuous Weld

Hypervelocity Impact Analysis of Aerospace Materials

Aluminum Alloy Phenolic Resin Silicon Carbide

Plasma Drag Hypervelocity

Particle Accelerator

Nanostructured Polymeric and Cementitious Materials

Dispersion of Nanoparticles

Well dispersed Acid treated MWCNTs

Mechanical Performance of Nanostructured MWCNT Tetrafunctional Epoxy Systems

020

406080

100120140160

180200

0 0.2 0.4 0.6 0.8 1 1.2Deflection, mm

Fle

xura

l Str

ess,

MP

a

nano

neat

MWCNT dispersed in epoxy matrix A considerable enhancement in the

flexural strength has been achieved with MWCNT reinforcement.

Testing and evaluation of Materials and Components under Extreme Conditions

¾Salt fog &SO2 exposure ¾Salt fog ¾Sand cloud exposure ¾UV aging ¾A combination of the above tests

Aerospace, Defense & High Performance Electronics are affected by this legislation

Aerospace, Defense and High Performance Electronics are affected at the component level

Since the RoHS legislation Component terminations are now plated with Tin

Tin plating material has a long history of growing Tin whiskers

Tin Whiskers are electrically conductive single crystalline tin structures that grow from pure tin-plated surfaces

What are Tin Whiskers?

Tin Whiskers are very small

Picture courtesy of NASA Goddard Space Flight Center

Components are getting smaller and the gap between terminations

is narrowing

Gap spacing is decreasing

Tin Whiskers closing the gap

The uniqueness of Tin Whiskers

So what are the implications when they close the gaps?

Galaxy IV Satellite Failure

What are Conformal Coatings and can they help

Below is a conformal coated circuit board

Above is a circuit board prior to conformal coating

Tin Whiskers versus Conformal Coatings

Tin Whiskers will grow through conformal coatings

Tin Whiskers versus Conformal Coatings

Conformal coatings protect circuits from corrosion on Naval

Vessels

Tin plated brass coupons coated with Epoxy, Acrylic, Urethane and silicon conformal coatings are submerged in a salt solution waiting for the growth of Tin Whiskers

The search for Tin Whiskers

The Olympus G5000 Optical Microscope

Students at Tuskegee start the search with an Optical Microscope

The students start their search for whiskers using the Microscope and a

grid

The Test Coupon The Grid

A B C D

1

2

3

4

5

6

7

The they take the Coupon and examine the locations under a Scanning Electron Microscope

Dr. Aglan and graduate students examining a Tin Whisker growth

The Hitachi S3400N Scanning Electron

Microscope

Tuskegee Students uses a Scanning Electron Microscope and XRD to

confirm it is a Tin Whisker

SEM micrograph showing salt crystals on acrylic coating from scratched flat coupon after 9500 hour exposure to corrosive environment (aqueous NaCl); magnification is 400X (a); XRD is shown on right (b). The percentages of tin and oxygen are 4.38% and 11.08%, respectively.

SEM micrograph showing conjoined whiskers from scratched flat coupon after 7000 hours of exposure to corrosive environment (aqueous NaCl); magnification is 4000X. The percentages of tin and oxygen are 56.34% and 34.61% respectively.

With patients and a lot of searching students at Tuskegee are growing and

finding Tin Whiskers

Conformal Coated Coupons in a Thermal Chamber

Coupons going through a Thermal

Cycling process to accelerate the

growth of Tin Whiskers.

A coupon half covered with a

conformal coating and the other

half exposed.

Conformal Coated Coupons in a Thermal Chamber

A coupon half covered with a conformal coating and the other

half exposed. Determining the effectiveness of the various

conformal coatings to inhibit the growth of Tin Whiskers

Probability of a Tin Whisker Shorting between two Adjacent

Leads

David Burdick and graduate students reviewing the progress and the next steps

The Next Steps ¾ The study to determine if one conformal coating is better at

mitigating the effects of corrosion is still underway.

¾ The study to calculate the probability of a Tin Whisker causing

a short is still underway.

¾ The study to determine if one conformal coating it better at

mitigating the risk of a Tin Whisker short is still underway.

¾ A new effort is being considered to improve the effectiveness

of preventing penetration of conformal coatings by Tin

Whiskers by using nanoparticles.

Questions?