Exploring On The Mechanical Strength Of Polymer-metal Composites For The Additive Manufacturing Of Threedimensional Electronics

A hybrid additive manufacturing technology based on fused deposition molding(FDM)3D printing process is proposed in this paper.This technology combines the dual-material FDM3 D printing process with the selective electroless plating process to manufacture the polymermetal composite structure and realize three-dimensional electronic circuit products.In the process of promoting the practical application of this technology,it is found that the mechanical strength of polymer-metal composite structure largely determines the application field of this technology.At present,the research on the mechanical strength of FDM 3D printing is mostly concentrated on a single material,and the research on the strength of polymer-metal composite is rare.Therefore,this paper systematically studies the mechanical strength of polymer-metal composite structure,and promotes the practical application of hybrid additive manufacturing technology in the field of 3D electronic circuit manufacturing.This study mainly completed the following works:1.The polymer-polymer mechanical strength in the polymer-metal composite structure.After sample preparation and testing,the mechanical strength of ABS and PLA,PETG,and PC three groups of dual-materials printed in both horizontal and vertical directions was obtained.Combined with microscopic characterization,different materials and different printing directions(horizontal/vertical)were compared and analyzed.The mechanical strength test results show that the mechanical strength between polymer and polymer is anisotropic,not only the mechanical strength of horizontal/vertical printing is different,but also the difference in the printing order of materials in the vertical direction will also affect the final strength.It is found that ABS and PETG dual-material printing has the best bond strength.In addition,we also found that the electroless plating process in hybrid additive manufacturing has almost no effect on the polymer-polymer mechanical strength,which proves that the hybrid additive manufacturing process we use has good material compatibility.2.The mechanical strength between the polymer and the metal in the polymer-metal composite structure.Based on the combination of ABS and PETG,the mechanical strength between the metal plating layer and the base printing material and between the metal plating layer and the upper printing material was tested.The test found that the mechanical strength of the two interfaces is quite different.Combined with SEM characterization,it is found that the base material has been roughened to form a large number of micropores on the surface,and the metal plating "roots" penetrated into the base printing material to form an "interlocking" structure,so the mechanical strength is relatively high.However,the metal plating layer-upper printing material is only the adhesion of the molten FDM plastic to the metal surface after cooling and solidification,so the bonding strength is less than 10% of the metal plating layerbase printing material.3.Put forward the important principles of polymer-metal composite structure in terms of mechanical strength.(1)Regarding the choice of matrix material,since PETG and ABS dualmaterial printing have the best mechanical strength,these two materials are preferred as matrix materials;(2)The bonding strength between the metal plating layer and the upper printing material is the lowest,which affects the overall structural strength,so the circuit graphic design should be optimized to reduce the area ratio of the circuit area to ensure the overall structural strength.4.Designed,manufactured and tested application samples such as strain self-sensing intelligent structural parts and temperature self-sensing intelligent water pipes.The sensitivity factor of the strain self-sensing smart structure is 1.99,which meets the standard of commercial metal foil strain gages.The resistance temperature coefficient of the smart water pipe is 0.0035,which is sufficient to meet the temperature measurement needs.The above two application samples fully prove the practicability of the hybrid additive technology proposed by this research group in the research and development of 3D electronic circuits.