The advanced consumer electronic gadgets are tending to be miniaturized in size and incorporated with multi-function purposes. The mechanical and electrical reliability of such products has become one of the critical issues. However, delamination under high thermal and moisture environment is prone to happen between copper (Cu) and epoxy compound interfaces due to the weak Cu/epoxy interfacial adhesion.

In solving this problem, thiol-based self-assembled material (SAM) is applied to serve as a coupling agent between the Cu/epoxy interfaces by the formation of covalent bonding. However, the reported thiol-based self-assembled treatment time ranges from 16 to 24 hours which greatly hinders the adoption of thiol-based self-assembled treatment in the high throughput of industri...[ Read more ]

The advanced consumer electronic gadgets are tending to be miniaturized in size and incorporated with multi-function purposes. The mechanical and electrical reliability of such products has become one of the critical issues. However, delamination under high thermal and moisture environment is prone to happen between copper (Cu) and epoxy compound interfaces due to the weak Cu/epoxy interfacial adhesion.

In solving this problem, thiol-based self-assembled material (SAM) is applied to serve as a coupling agent between the Cu/epoxy interfaces by the formation of covalent bonding. However, the reported thiol-based self-assembled treatment time ranges from 16 to 24 hours which greatly hinders the adoption of thiol-based self-assembled treatment in the high throughput of industrial applications.

This thesis starts with investigating the adhesion promotion effect on a Cu/epoxy interface of a thiol-based SAM on a Cu substrate with the aim to minimize the preparation time. Unlike the traditional passive immersion treatment of SAMs, an electric potential was applied on the Cu substrate during the assembly process in a standard three-electrode cell. It was demonstrated that the interfacial adhesion has a 20-fold enhancement as a result of the treatment and the treatment time was greatly reduced by a factor of 32 from 16 hours to 30 minutes.

The effect of the applied electric potential on SAM adsorption kinetic was then investigated. It was demonstrated there existed a chemisorption electric potential threshold of the electrochemical SAM assembled process that was closely related to the potential of zero charge (PZC) of the electrolyte system.

Based on the obtained experimental data, two one-dimension mass transport models were proposed to investigate the effect of elevated temperature as well as the applied electric potential on the SAM adsorption process. The models suggested the increased temperature could not provide sufficient activated energy for the diffusional process and the electrochemical assembly of SAM could not be explained solely based on the transport phenomenon. Certain potential-dependent electrode processes like the SAM desorption and oxidation of the Cu substrate under the electric potential should also be considered for explaining the experimental findings.

The reductive desorption of the SAM from the substrate was studied and investigated experimentally. The Cu oxidation and reduction potential in the electrolyte system were located by the electrochemical method. The results demonstrated that at the SAM desorption potential as well as at the Cu oxidation potential, the kinetics of the SAM adsorption were largely impeded while enhanced kinetics were recorded at the potential region near the PZC. Based on the experimental findings, a mechanistic model for the SAM electrochemical assembly process is proposed at the end of this thesis. Apart from the enhanced mass transport process, the potential-dependent electrode processes such as the SAM reductive desorption and Cu substrate oxidation should also be considered during the electrochemical assembly process.