Research Papers

Advanced Methodologies for Developing Improved Potted Smart Munitions for High-G Applications

[+] Author and Article Information
Nien-Hua Chao

U.S. Army, ARDEC,
Picatinny Arsenal, NJ 07806

John A. Dispenza

Design Results, LLC,
Long Valley, NJ 07853

Mario DeAngelis

U.S. Army, ARDEC,
Picatinny Arsenal, NJ 07806

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received August 20, 2012; final manuscript received April 12, 2013; published online June 4, 2013. Assoc. Editor: Stephen McKeown.This material is declared a work of the US Government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited.

J. Electron. Packag 135(3), 031002 (Jun 04, 2013) (14 pages) Paper No: EP-12-1077; doi: 10.1115/1.4024301 History: Received August 20, 2012; Revised April 12, 2013

Potted electronics are becoming more common in precision-guided smart munitions designs due to the requirements for miniaturization and structural-robustness. In most of these applications, the potted electronics are inactive for most of their lifetime and may be stored without environmental (temperature and humidity) controls for up to 20 yr. The uncontrolled environment for smart munitions however makes the thermal management task especially difficult due to the coefficient of thermal expansion (CTE) mismatch that can exist between the potting material and the electronic components. In this paper, we will do the following: (1) present a methodology being developed for reducing the thermal stresses to the potted electronics used in uncontrolled environments by encapsulating the circuit board assembly (CBA) with a thin polymer layer which has been precisely formed to conform to the imprecisely shaped, as-populated, CBA. The protective polymer layer will be both flexible and soft enough to protect the CBA components from damage caused by thermal expansion mismatches, but not degrade the structural support that the potting provides during high-g force projectile launches, (2) discuss how the protective polymer layer methodology can also be used to lessen in-circuit board crosstalk, improve shielding from external RF interference, control tin-whisker growth, and enhance moisture barrier properties and thermal management for CBAs, and (3) demonstrate how to improve the smart munitions survivability under extreme high-g applications through the use of syntactic foams and material characterization before and after accelerated temperature-cycling and thermal-aging tests.

Copyright © 2013 by ASME
Your Session has timed out. Please sign back in to continue.


Chao, N. H., Cordes, J., Carlucci, D., DeAngelis, M., and Lee, J., 2011 “The Use of Potting Materials for Electronic-Package Survivability in Smart Munitions,” ASME J. Electron. Packag., 133(4), p. 041003. [CrossRef]
Wu, J., Pike, R. T., Wong, C. P., Kim, N. P., and Tanielian, M. H., 2000, “Evaluation and Characterization of Reliable Non-Hermetic Conformal Coatings for Microelectromechanical System (MEMS) Device Encapsulation,” IEEE Trans. Adv. Packag., 23(4), pp. 721–728. [CrossRef]
Hildreth, O., and Wong, C. P., 2009, “Improved Method to Evaluate the Adhesion Properties of Thin Film Conformal Coatings,” IEEE 59th Electronic Components and Technology Conference (ECTC 2009), San Diego, CA, May 26–29. [CrossRef]
Medgyes, B. K., and Ripka, G., 2007, “Qualifying Methods of Conformal Coatings Used on Assembled Printed Circuit Boards,” 30th IEEE International Spring Seminar on Electronics Technology, Cluj-Napoca, Romania, May 9–13. [CrossRef]
Neidigk, M. A., and Shen, Y. L., 2009, “Nonlinear Viscoelastic Finite Element Analysis of Physical Aging in an Encapsulated Transformer,” ASME J. Electron. Packag., 131, p. 011003. [CrossRef]
Spratt, J. P., Aghara, S., Fu, B., Lichtenhan, J. D., and Leadon, R., 2005, “A Conformal Coating for Shielding Against Naturally Occurring Thermal Neutrons,” IEEE Trans. Nucl. Sci., 52(6), pp. 2340–2344. [CrossRef]
Tomlins, P. E., 2000, “A Method to Quantify the Surface Insulation Resistance Performance of Conformal Coatings Exposed to Different Temperature/Humidity Conditions,” IEEE International Symposium on Electronic Materials and Packaging (EMAP 2000), Hong Kong, November 30–December 2. [CrossRef]
Thomas, B. R., 1992, “Stress-Free Potting,” IEEE Electr. Insul. Mag. (USA), 8(6), pp. 21–24. [CrossRef]
Salmon, E. R., 1988, “Coefficient of Thermal Expansion of Encapsulants—Is It Always a Constant?,” IEEE Electr. Insul. Mag. (USA), 4(5), pp. 26–28. [CrossRef]
Baylakoglu, I., Hillman, C., and Pecht, M., 2003, “Characterization of Some Commercial Thermally-Cured Potting Materials,” International IEEE Conference on the Business of Electronic Product Reliability and Liability, Hong Kong, January 15–17.
Chung, D. D. L., 2001, “Polymer-Matrix Composites for Microelectronics,” Applied Materials Science: Applications of Engineering Materials in Structural, Electronics, Thermal, and Other Industries, Deborah D. L. Chung, ed., CRC Press, Boca Raton, FL, Chap. 3. [CrossRef]
Obitz, D. L., 2005, “Conformal Coating Testing at Vendor Level,” Conformal Coating Task Group, Report No. IPC-CC 830.
Chao, N. H., Dispenza, J. A., and DeAngelis, M. E., “Protective Layering Process for Circuit Boards,” US Patent Pending, No. 13/682,980.
Chao, N. H., Dispenza, J. A., and DeAngelis, M. E., 2012, “Encapsulating Protective Layers for Enhancing Survivability of Circuit Board Assemblies in Harsh and Extreme Environment,” ASME International Mechanical Engineering Congress & Exposition (IMECE 2012), Houston, TX, November 9–15, ASME Paper No. IMECE2012-85959.
IDES Prospector, “ A Material Properties Database,” http://prospector.ides.com
abaqus, version 6.11, Analysis User's Manual, Dassault Systèmes, Waltham, MA.
Leach, R. D., and Alexander, M. B., 1995, “Electronic Systems Failures and Anomalies Attributed to EMI,” NASA Report No. 1374.
Chung, D. D. L., 2000, “Materials for Electromagnetic Interference Shielding,” J. Mater. Eng. Perform., 9(3), pp. 350–354. [CrossRef]
Hannafin, J., 2002, “A Novel Approach to Thermal Management and EMI Shielding Via a Metallic Conformal Coating on a Plastic Housing,” Proceeding of the SMTA/IMAPS Conference and Exhibition on Telecom Hardware Solutions, Plano, TX, May 15–16.
Erbas, C., and Kent, S., 2003, “Shielding Effectiveness of a Rectangular Cavity With Aperture Between 1–3 GHz,” IEEE International Symposium on Electromagnetic Compatibility (EMC'03), Istanbul, Turkey, May 11–16. [CrossRef]
McMillan, T., 2008, “Using Conductive Plastic for EMI Cover Shielding,” IEEE International Symposium on Electromagnetic Compatibility (EMC 2008), Detroit, MI, August 18–22. [CrossRef]
Karim, N., Mao, J., and Fan, J., 2010, “Improving Electromagnetic Compatibility Performance of Packages and SiP Modules Using a Conformal Shielding Solution,” 2010 Asia-Pacific International Symposium on Electromagnetic Compatibility (APEMC), Beijing, China, April 12–16. [CrossRef]
NASA Tin Whisker (and Other Metal Whisker) Homepage, http://nepp.nasa.gov/whisker/index.html
Boguslavsky, I., Bush, P., Kam-Lum, E., Kwoka, M., McCullen, J., Spalding, K., Vol, N., and Willaims, M., 2003, “NEMI Tin Whisker Test Method Standards,” The Proceedings of the SMTA International Conference, Chicago, IL, September 21–25.
Woodrow, T. A., 2005, “Evaluation of Conformal Coating as a Tin Whisker Mitigation Strategy,” IPC/JEDEC 8th International Conference on Lead-Free Electronic Components and Assemblies, San Jose, CA, April 18–20.
Woodrow, T. A., and Ledbury, E. A., 2006, “Evaluation of Conformal Coating as a Tin Whisker Mitigation Strategy, Part II,” Proceedings of SMTA Internal Conference, Rosemont, IL, September 24–28.
Sood, B., Osterman, M., and Pecht, M., 2011, “Tin Whisker Analysis of Toyota's Electronic Throttle Controls,” Circuit World, 37, pp. 4–9. [CrossRef]
Panashchenko, L., 2012, “The Art of Metal Whisker Appreciation: A Practical Guide for Electronics Professionals,” IPC Tin Whisker Conference, Fort Worth, TX, April 17–19.
Rohwer, L., 2012, “Tin Whisker Mitigation,” Joint DOD/DOE Munitions Program, Sandia National Laboratories, Albuquerque, NM, May 2–3.
Oshman, C., Shi, B., Li, C., Yang, R., Lee, Y. C., Peterson, G. P., and Bright, V. M., 2011, “The Development of Polymer-Based Flat Heat Pipes,” J. Microelectromech. Syst., 20(2), pp. 410–417. [CrossRef]
Lee, Y. C., Bright, V., Yang, R., George, S., Li, C., Peterson, G. P., and Rawal, S. P., 2011, “Flexible Thermal Ground Plane With Micro/Nano-Scale Wicking Structure,” DARPA TMT Review, December 1.
Oshman, C., Li, Q., Liew, L., Yang, R., Bright, V., and Lee, Y. C., 2012, “Flat Flexible Polymer Heat Pipes,” J. Micromech. Microeng., 23, p. 015001. [CrossRef]
Gupta, N., and Nagomy, R., 2006, “On the Tensile Properties of Glass Microballoon-Epoxy Resin Syntactic Foams,” J. Appl. Polym. Sci., 102, pp. 1254–1261. [CrossRef]
Ozawa, Y., Watanabe, M., Kikuchi, T., and Ishiwatari, H., 2010, “Mechanical and Thermal Properties of Composite Material System Reinforced With Micro Glass Balloons,” IOP Conf. Ser: Mater. Sci. Eng., 10, p. 012094. [CrossRef]
Quesenberry, M. J., Madison, P. H., and Jensen, R. E., 2003, “Characterization of Low Density Glass Filled Epoxies,” Army Research Laboratory. Aberdeen Proving Ground, MD, Report No. ARL-TR-2938.
3M Scotchlite Glass Bubbles K Series and S Series—Product Information, 3M, St. Paul, MN.
STYCAST 1090/Catalyst 9, Technical Data Sheet, Henkel, Shanghai.
“JESD22-A118–Accelerated Moisture Resistance—Unbiased Highly Accelerated Stress Test (HAST),” JEDEC Solid State Technology Association, March 2011.
Teverovsky, A., 2002, “Moisture Diffusion in Molding Compounds and Quality Assurance of PEMs for Space Applications,” Goddard Operations, NASA. December.
Teverovsky, A., and Sahu, K., 2003, “PEM-INST-001: Instructions for Plastic Encapsulated Microcircuit (PEM) Selection, Screening, and Qualification,” NASA/TP.
Denson, W., Farrell, J., and Nicholls, D., 1996, “Reliable Application of Plastic Encapsulated Microcircuits,” 4th Annual Commercial and Plastic Components in Military Applications Workshop, Indianapolis, IN, November 15–16, Reliability Analysis Center, Rome, NY.
ALCHEMIX® PU&301 data sheet, Alchemie, Kineton, UK.
Arathane 5753-A/B(LV) data sheet, Huntsman LLC, Danbury, CT.
Mates, S., Forster, A., and Haynes, A., 2012, private communication.


Grahic Jump Location
Fig. 1

(a) Potted munition component and separate housing and CBA before potting and (b) an exploded view of a component

Grahic Jump Location
Fig. 2

A process of forming polymer layer(s) to CBA with vacuum using CBA duplicate

Grahic Jump Location
Fig. 3

A process of layering polymer layer(s) to CBA by using conformal mold

Grahic Jump Location
Fig. 4

A CBA production sample fully populated

Grahic Jump Location
Fig. 5

A protective polymer layer tightly fit to CBA

Grahic Jump Location
Fig. 6

Soft, synthetic rubber, conformal cavity mold

Grahic Jump Location
Fig. 7

FE model of a MEMS attached to PCB, frame, can, cover, and potting materials [1]

Grahic Jump Location
Fig. 8

MEMS device with and without protective polymer (elastomer) layer

Grahic Jump Location
Fig. 9

HALT temperature profile 150 °F to −50 °F Δ = 9 °F/min

Grahic Jump Location
Fig. 10

Seal maximum principal stress comparison (without and with protective layer). (a) MEMS seal without protective layer (stress range: −12420 psi to 7160 psi) and (b) MEMS seal with protective layer (stress range: −80 psi to 5060 psi).

Grahic Jump Location
Fig. 11

Seal Tresca stresses comparsion (without and with protective layer)

Grahic Jump Location
Fig. 12

Temperature cycle profile (°F versus second)

Grahic Jump Location
Fig. 13

Experiment thermal setup and HALT test recorded data

Grahic Jump Location
Fig. 14

Alchemix (unfilled versus filled) tensile stress versus strain (nonthermal conditioning)

Grahic Jump Location
Fig. 15

Alchemix (unfilled versus filled) tensile stress versus strain (after HALT test)

Grahic Jump Location
Fig. 16

Alchemix (unfilled versus filled) tensile stress versus strain (after HAST test)

Grahic Jump Location
Fig. 17

The projectile launch and penetration profiles. (a) Projectile launch profile and (b) projectile penetration profile.

Grahic Jump Location
Fig. 18

Sensitivity analysis of potting material tensile modulus versus density



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In