Conductive Paste Dispensing on Polypropylene 3D Parts
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Solution Overview
Problem
Current methods for integrating electronics into 3D parts face limitations, such as restricted 3D geometries, material compatibility issues, and the need for altering conventional manufacturing processes, particularly in the automotive industry, where achieving sharp corners and deep embedments of electronic components is challenging.
Innovation Solution
A method involving micro-dispensing of conductive, dielectric, and adhesive inks onto 3D injection-molded polypropylene-based parts using a robotic system, allowing for the direct printing of electronic assemblies, including conductive paths, sensors, and components, without altering the existing manufacturing process, by selecting specific ink compositions and dispensing parameters tailored to the part's geometry and surface characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If functional printing is performed on a 3D part made of polypropylene-based material, then electronic assemblies can be directly integrated on complex geometries, but adhesion of conductive paste to the substrate is extremely low
Solution Approach 1:
A polymeric binder is used as an intermediary substance between the conductive metallic particles and the polypropylene substrate. The binder adheres to both the substrate and the metallic particles, creating a strong bond that overcomes the naturally low adhesion between metal and polypropylene. This mediator enables reliable electrical connections on complex 3D geometries without requiring substrate modification.
2Reliability
If high temperature sintering is applied to obtain high electrical conductivities, then conductivity improves, but most plastics being targeted in the automotive sector are damaged
Solution Approach 1:
The sintering temperature parameter is reduced from conventional high temperatures (which damage plastics) to a lower temperature range of 80°C to 150°C. This parameter change enables the formation of conductive pathways through metallic particles without exceeding the thermal tolerance of polypropylene and other automotive plastics, thus achieving both conductivity and substrate integrity.
3Ease of manufacture
If molten metal jetting is used to deposit electric circuit, then circuit formation is achieved, but line resolution control is difficult due to dependence on drop size
Solution Approach 1:
The mechanical jetting process that deposits molten metal is replaced with a microdispensing process that applies viscous conductive paste containing metallic particles. This substitution eliminates the drop-size-dependent resolution issues of jetting, as the paste can be precisely controlled through viscosity management and dispensing pressure, enabling accurate line formation even on complex 3D surfaces.
4Adaptability or versatility
If conventional injection molding process is altered to integrate electronics, then electronic integration is achieved, but manufacturing complexity and process time increase
Solution Approach 1:
The manufacturing process is segmented into distinct sequential steps: first, the polypropylene 3D part is injection molded using conventional processes; second, conductive paste is microdispensed onto the finished part; third, the paste is sintered at low temperature; and fourth, additional electronic components are attached. This segmentation allows each step to be optimized independently and maintains compatibility with existing injection molding lines without requiring process integration that would increase complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the creation of 3D parts with complex geometries and electronic assemblies on polypropylene-based materials, ensuring good adhesion and conductivity, while maintaining the integrity of conventional injection molding processes, allowing for a wide variety of electronic assemblies on diverse geometries with high accuracy and without the need for additional processing steps.
Implementation Method 1
a fluid dispensing technique (also referred to as micro-dispensing), in which beads of ink, such as conductive paste, form a filament when they are continuously deposited on the surface of the 3D part
Implementation Method 2
The printing process is performed using a robot or robotic system that may handle different types of printing modules using different heads (fluid dispensers) with corresponding dispensing nozzles, through which a material, such as functional ink or adhesive, is applied, and curing modules to sinter the inks
Data Source
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AI summary
A method of applying an electronic assembly on a 3D part made of a polypropylene-based material, the electronic assembly comprising at least one electrically conductive path having width between 0.1 and 4 mm, the method comprising: providing a 3D part made of a polypropylene-based material; selecting a conductive paste (128) comprising: metallic particles comprising silver, a binder and an organic solvent; the amount of binder being between 1 to 5 wt%; the amount of metallic particles being between 74 to 90 wt%, the metallic particles having an average size between 50nm to 50µm; wherein the viscosity of the conductive paste is between 75 and 425 Pa-s measured with a rheometer at a temperature of 25°C at 1/s shear rate; providing a fluid dispensing system (11) for applying the conductive paste (128) onto a surface of the 3D part; selecting and attaching a nozzle (125) to the fluid dispensing system (11), through which the selected conductive paste is to be dispensed, wherein the nozzle (125) is selected such that its inner diameter is as close as possible to the width of the conductive path to be applied, the inner diameter of the nozzle (125) being smaller than the width of the conductive path to be applied; dispensing the selected conductive paste (128) on to the surface of the 3D part through said nozzle (125) by applying a pressure between 0.2 and 13 bar, while maintaining a maximum distance of 900 µm between the nozzle (125) and the surface of the 3D part; curing the deposited conductive paste; depositing a dielectric ink on the printed conductive path; curing the deposited dielectric ink; attaching at least one electronic component on the conductive path.