Low Speed Impact Resistance of Gradient Encapsulated Circuit Board Structure

doi:10.12382/bgxb.2023.0949

Abstract

Abstract:

Encapsulating protection has been widely used in automobiles, ships and weapons. It can enhance the integrity of electronic equipment and improve the resistance to external shocks and vibrations. However, the traditional homogeneous resin encapsulating materials have insufficient toughness and poor impact resistance. In response to this issue, this paper designs the resin gradient encapsulated materials reinforced with carbon nanotube (CNT) and studies the impact resistance of gradient encapsulated circuit board structure. The enhancing effects of different CNT contents on resin matrix and the impact resistance of gradient encapsulated structures are analyzed through quasi-static tensile tests and dynamic drop hammer impact tests. The energy absorptions of different gradient layers are obtained and the damage and failure of internal circuit boards are evaluated through finite element simulation analysis. The research results show that the encapsulating material with 0.7wt % CNT exhibits a higher tensile strength, which is 16% higher than that of pure epoxy resin; The impact strength and critical failure energy of V-shaped encapsulated gradient plate are higher than those of other gradient types, and are increased by 40% and 15.8%, respectively, compared to the homogeneous plate. The buffering and energy absorption properties of the encapsulating materials have a positive impact on the protection of internal electronic components, with the gradient layer containing a higher CNT content exhibiting an increased energy absorption. The gradient encapsulation method proposed in this paper provides a reference for the protection design of electronic components under impact environment.

Key words: encapsulation protection, gradient material, energy absorption, impact resistance, electronic component

CLC Number:

ZHU Xiufang, ZHOU Hongyuan, ZHANG Hong, CHEN Xinmin. Low Speed Impact Resistance of Gradient Encapsulated Circuit Board Structure[J]. Acta Armamentarii, 2024, 45(11): 3879-3891.

Figures/Tables 20

Fig.1 Preparing process of CNT reinforced epoxy resin gradient encapsulating material

Table 1 Different gradient types of test plates

Fig.2 Quasi-static tensile test

Fig.3 Quasi static tensile stress-strain curves of CNT reinforced composite materials

Fig.4 Dynamic tensile stress-strain curves of CNT reinforced composite materials

Fig.5 Tensile stress-strain curves of PCB

Fig.6 Dynamic impact test system

Fig.7 Comparison of impact responses of different gradient types

Fig.8 Acceleration-time curves of each gradient plate under critical failure energy

Table 2 Material parameters of finite element model

CNT含量	密度/ (g·cm^-3)	弹性模量/GPa	泊松比	极限强度/MPa
纯EP	1.12	5.59	0.32	55.36
0.1%	1.12	6.06	0.32	58.47
0.3%	1.13	6.24	0.32	59.17
0.5%	1.13	6.85	0.32	67.51
0.7%	1.13	7.95	0.32	79.52
PCB	1.97	26.00	0.3	120

Table 3 Brittle fracture model of encapsulating materials with different CNT contents and PCB

CNT 含量	输入点	断裂后直接应力/ MPa	直接断裂应变/ MPa	剪切传递系数	裂纹展开应变
纯EP	1	55.36	0	1	0
	2	0	0.013	0	0.001
0.1%	1	58.47	0	1	0
	2	0	0.015	0	0.001
0.3%	1	59.17	0	1	0
	2	0	0.019	0	0.001
0.5%	1	67.51	0	1	0
	2	0	0.021	0	0.001
0.7%	1	79.52	0	1	0
	2	0	0.023	0	0.001
PCB	1	120	0	1	0
	2	0	0.006	0	0.001

Fig.9 1 Finite element model for drop-hammer impact of encapsulated plate

Fig.10 Force-time curves of Ⅴ-shaped gradient plate under 19J impact energy with different number of elements

Fig.11 Experimental and finite element comparison curves of different gradient types of encapsulated plates

Fig.12 Comparison of experimental and simulated impact parameters for various gradient encapsulated plates

Fig.13 Damage and failure morphology of impact surface of plates (Gradient V)

Fig.14 Stress and strain curves of PCB central unit under 19J impact energy

Fig.15 Energy distribution curves of different gradient types of encapsulated plates

Fig.16 Finite element impact simulation process of EP encapsulated plate under 19J impact energy

Fig.17 Finite element impact simulation process of gradient encapsulated plate V under 22J impact energy

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