dc.description.abstract | As electronic products continue to develop towards miniaturization, lightness, mul-ti-functionality, and high density, the density of components assembled on circuit boards for functional integration between devices is also increasing. This leads to higher power consumption and heat generation in high-density circuit boards. If the impedance of the metal used for conducting signals is too high, it will result in poor heat dissipation on the circuit board, causing the components to overheat, which in turn reduces the efficiency, lifespan, and reliability of the products. To address this issue, Copper Clad Laminate (CCL) has become a key material in the manufacturing of Printed Circuit Boards (PCBs). CCL is made by impregnating glass fibers and other reinforcing materials in resin and then coat-ing one or both sides with copper. It is widely used in electronic products such as televi-sions, broadcasting, computers, and mobile communications. With technological ad-vancements, the application scope of CCL has also expanded in fields like aerospace, communication equipment, consumer electronics, and LED lighting, providing strong support and foundation for electronic products in various industries.
In the PCB process that uses CCL as the Redistribution Layer (RDL), the edge sealing between the copper foil layers relies on a wet etching process to protect and fix the copper foils from separation in the subsequent processes. This method mainly involves protecting the selected area with a photoresist, and after exposure and development, the upper layer of approximately 5 μm thick copper foil and part of the lower copper foil are etched away. The etched surface is then sealed to protect the polymer material of the separation layer, preventing separation in subsequent processes.
This study aims to develop a laser welding method that uses infrared laser sealing on thin copper foil substrates, examining its feasibility as a replacement for the aforemen-tioned wet process to facilitate subsequent Embedded Trace Substrate (ETS) processing. The research focuses on welding two layers of copper foil with thicknesses of 5 μm and 18 μm, comparing the welding effects using a pulsed laser with a wavelength of 1064 nm and a maximum power of 20 W and a continuous wave laser with a wavelength of 1070 nm and a maximum power of 500 W. The goal is to minimize the heat-affected zone and avoid damaging the organic material beneath the copper foil while forming a stable and uniform weld at a welding speed of 100 mm/s.
To ensure bonding strength, samples were characterized and tested using a micro-scope and welding strength tester. The results show that the peel strength after pulsed laser welding can reach 2.54 N/cm, and the maximum peel strength with continuous wave laser welding can reach 0.98 N/cm. Both results are higher than the peel strength of polymer glue, demonstrating that direct laser welding of thin copper foil can meet the requirements of actual processes in terms of strength and durability. In addition to providing precise and efficient sealing of thin copper foil, this method is also relatively more environmentally friendly. | en_US |