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. 2019 Nov 29;9(1):17902.
doi: 10.1038/s41598-019-54045-w.

Recycling Waste Circuit Board Efficiently and Environmentally Friendly through Small-Molecule Assisted Dissolution

Zhiqiang Chen  1 , Meng Yang  1 , Qian Shi  1 , Xiao Kuang  2 , H Jerry Qi  3 , Tiejun Wang  4
Affiliations

Recycling Waste Circuit Board Efficiently and Environmentally Friendly through Small-Molecule Assisted Dissolution

Zhiqiang Chen et al. Sci Rep. .

Abstract

With the increasing amount of electronic waste (e-waste) generated globally, it is an enormous challenge to recycle printed circuit boards (PCBs) efficiently and environmentally friendly. However, conventional recycling technologies have low efficiency and require tough treatment such as high temperature (>200 °C) and high pressure. In this paper, a small-molecule assisted approach based on dynamic reaction was proposed to dissolve thermosetting polymers containing ester groups and recycle electronic components from PCBs. This effective approach operates below 200 °C and the polymer could be dissolved in a short time. It has a remarkable ability to recycle a wide range of commercial PCBs, including boards made of typical anhydride epoxy or polyester substrate. Besides, it is environmentally friendly as even the recycling solution could be reused multiple times. In addition, the wasted solution after recycling could be used for board bonding and damage repair. This work also demonstrates the advantage of using polymers containing ester groups as the PCB substrate in consideration of eco-friendly and efficient recycling.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
(a) The process of bond exchange reaction via transesterification. Hydroxy groups in solvent break ester bonds in the polymer network. (b) Mechanism of the small-molecule assisted dissolution method.
Figure 2
Figure 2
(a) Recycling composite board through the small-molecule assisted approach. The composite matrix was MTHPA cured epoxy. (b) The SEM micrographs of the raw glass fiber and the recycled glass fiber.
Figure 3
Figure 3
(a) The circuit board made in the lab. The substrate was the anhydride-epoxy composite. (b) The recycled circuit. (c) The recycled glass fiber. (d) Electrical property of recycled electronic components.
Figure 4
Figure 4
Recycling commercial epoxy PCB through the small-molecule assisted approach. (a) The commercial PCB sample and the recycling treatment. (b) The recycled circuit and the electronic components. (c) The recycled glass fiber and the SEM micrograph.
Figure 5
Figure 5
Recycling flexible polyester PCB through the small-molecule assisted approach. (a) The polyester PCB sample; the inset shows its good flexibility. (b) The degradation process of the polyester matrix. (c) The recycled circuit.
Figure 6
Figure 6
The multilayer board fabrication by using the intrinsic bonding approach. (a) The mechanism of intrinsic bonding through bond exchange reaction between the small molecules in the adhesive solution and the polymer network in the composite surface. (b) Board bonding sample and failure mode in the lap shear test. The composite matrix was GA-cured epoxy. (c) Displacement-shear stress curves of the lap shear tests. (d) Multilayer circuit board bonded by four laminates.
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