New Developed Copper Electroplating Process for BMV Filling with the Special Feature of a Very Bright Cu Deposition on Flex and Flex-Rigid PCB ApplicationsAuthors: Mustafa Özkök Dipl.-Ing; Peter Haack, Dr; Vera Peldinski, Dipl.-Ing.; Thomas Huelsmann Dipl-Ing., Dr; Grigory Vazhenin, Dr.; Henning Hübner, Dipl.-Ing.
Company: Atotech Deutschland GmbH
Date Published: 9/22/2019 Conference: SMTA International
For example the choice of the appropriate Cu foil has a substantial impact on the further processing as well as on costs. While electrodeposited (ED or ECD) Cu foils are cheaper, a higher performance of the resulting devices can be achieved using rolled and annealed (RA) or High Performance Rolled Annealed (HA) Cu foils. Compared to ED Cu foils the special crystal structure of RA and HA Cu foils features crystals of a big size providing a far higher copper elongation and flex ductility. This allows for tighter bending angles as well as a higher numbers of repetitions. Though, this special crystal structure is also known to cause a matt surface after the electrolytic Cu plating step, but FPC makers prefer a shiny surface presumably due to AOI and/or to have a flat copper surface in order to minimize the so called skin effect for high frequency applications. It is known that a rough surface is not beneficial for high frequency signal transmission because of the skin effect .
copper electrolyte, Copper plating, Flex PCB, RA Foil, HA Foil, high frequency, skin effect, shiny copper
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