UV Light Bonding in Manufacturing of Transparent Displays
Kristiansson, Sonja (2023)
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-202303153618
https://urn.fi/URN:NBN:fi:amk-202303153618
Tiivistelmä
The goal for this thesis was to research the capability of the new bonding process for attaching the electroluminescent display (ELD) and the flexible printed circuit (FPC) together as well as to optimize the bonding process parameters. Process is executed with UV light bonder machine using a conductive UV light cured adhesive. This project was done for Lumineq Oy, which is specialized in manufacturing transparent displays using a thin film electroluminescent display technology.
Experimental part of this thesis consisted of tests, which were designed to research suitable parameters for the new bonding process. Design of experiment (DOE) was executed following a full factorial design 3^3. Conductive particle concentration, force of the bonding blade and UV light curing time were selected as factors on the basis of their impact on the most important properties of bonding process: conductivity, adhesion, and mechanical strength of the bond line.
Samples were visually inspected, and functionality was tested by connecting samples to power and straining them in high temperatures. The factors did not show any major impact to functionality, due to full function of the displays in all samples, including temperature effect. The conductivity of the bond line was evaluated with resistance measurements, and a tensile strength test was performed to evaluate the strength of the bond line. DOE with results were analysed using general factorial regression test. Model results showed that force as a single factor and particle concentration combined with force have the most impact on resistance and therefore the conductivity. Higher forces led to lower resistance values. Particle concentration had the largest impact on strength. Lower concentrations in the adhesive led to higher strength on the bond line.
The experiment provided information about the capability of UV light bonding process and the behaviour of the parameters. The process is feasible, reliable, and scalable based on this initial experiment and research. More research should be conducted to determine the process limits for parameters and to specify the process window. In addition, more research is required to obtain more data about the process behaviour.
Experimental part of this thesis consisted of tests, which were designed to research suitable parameters for the new bonding process. Design of experiment (DOE) was executed following a full factorial design 3^3. Conductive particle concentration, force of the bonding blade and UV light curing time were selected as factors on the basis of their impact on the most important properties of bonding process: conductivity, adhesion, and mechanical strength of the bond line.
Samples were visually inspected, and functionality was tested by connecting samples to power and straining them in high temperatures. The factors did not show any major impact to functionality, due to full function of the displays in all samples, including temperature effect. The conductivity of the bond line was evaluated with resistance measurements, and a tensile strength test was performed to evaluate the strength of the bond line. DOE with results were analysed using general factorial regression test. Model results showed that force as a single factor and particle concentration combined with force have the most impact on resistance and therefore the conductivity. Higher forces led to lower resistance values. Particle concentration had the largest impact on strength. Lower concentrations in the adhesive led to higher strength on the bond line.
The experiment provided information about the capability of UV light bonding process and the behaviour of the parameters. The process is feasible, reliable, and scalable based on this initial experiment and research. More research should be conducted to determine the process limits for parameters and to specify the process window. In addition, more research is required to obtain more data about the process behaviour.