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Research Papers

The Use of Potting Materials for Electronic-Packaging Survivability in Smart Munitions

[+] Author and Article Information
N. H. Chao, J. A. Cordes, D. Carlucci, M. E. DeAngelis, Jyeching Lee

 U. S. Army, ARDEC, Picatinny Arsenal, NJ 07806-5000

J. Electron. Packag 133(4), 041003 (Dec 08, 2011) (10 pages) doi:10.1115/1.4005375 History: Received December 14, 2010; Revised July 07, 2011; Published December 08, 2011; Online December 08, 2011

Potted electronics are becoming more common in precision-guided artillery due to demands for increased structural-robustness. In field artillery applications, the potted electronics are inactive for most of their lifetime. Projectiles may be stored in a bunker without environmental (temperature and humidity) controls for up to 20 years. In contrast, the electronics for most commercial applications tend to be active for most of their lifetime and the operating environment is more predictable. This difference makes the thermal management task for the artillery application challenging. The ability to accurately analyze these designs requires the use of fully coupled thermal-stress transient-analysis with accurate material properties over the full temperature range. To highlight the thermal-stress transient effects, the potted configuration of a typical electronics assembly is analyzed. The thermal analysis indicates that significant stresses can develop in critical locations as a result of temperature cycles. The structural dynamic responses of unpotted and potted assemblies, subjected to gun-launch environments, are also compared. The results indicate that for the potted design, the dynamic response of the processor board is attenuated by the potting material.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

FEM model of a MEMS attached to PCB, frame, can, cover, and potting material

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Figure 2

FE meshes for LCC, PCB, support frame, and potting material

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Figure 3

HALT temperature profile

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Figure 4

Shear stresses at the seal layer at time-step 459.5 s during the HALT process

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Figure 5

Shear stresses at the seal layer at time-step 5158 s during the HALT process

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Figure 6

Deformation-magnitude differences (Y-direction) at time-step 459.5 s during the HALT process

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Figure 7

Deformation-magnitude differences (Y-direction) at time-step 5158 s during the HALT process

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Figure 8

ARDEC Picatinny soft recover system [16]

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Figure 9

Model includes a processor board, one MEMS device packaging mounted on a PCB, and a frame structure (can, cover, and steel support-ring not shown)

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Figure 10

Gun launch acceleration boundary conditions [17]– applied to the can bottom entire surface

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Figure 11

Axial-Y, balloting (radial-1) X, balloting (radial-2) Z accelerations

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Figure 12

Dynamics simulation displacement data collection points

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Figure 13

The acceleration responses (y-axis) for the processor board for both with/without potting material cases

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Figure 14

The relative distance changes between the processor board and the bottom of the can for both with/without potting material cases

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Figure 15

The acceleration responses (y-axis) for the accelerometer lid for both with/without potting material cases

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Figure 16

The relative distance changes between the accelerometer lid and the bottom of the can for both with/without potting material cases (the bottom of the can is constrained by the applied accelerations)

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Figure 17

Overlay displacements of the processor boards from Fig. 1

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Figure 18

Overlay displacements of the accelerometer lids from Fig. 1

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