Publications (5)3.33 Total impact
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ABSTRACT: A new cladding process has been developed using the surface activated bonding (SAB) method. In this process, the surfaces of materials to be bonded are cleaned, activated by Ar ion sputter etching, and immediately rolled together with low distortion at room temperature in a vacuum chamber . This process is applicable not only to cladding metals but also to laminating polymer film on metal without adhesives. We focused on laminating liquid crystal polymer (LCP) on copper (Cu) foil using the SAB method , which is different from other conventional methods . We also investigated the chemical state at the interface between the Cu foil and LCP film before and after heat treatment (up to 300°C), by comparing with that on raw LCP film. All laminated materials were etched and cropped out, and the LCP surfaces were analyzed with X-ray photoelectron spectrometer (XPS). After the heat treatment, the ratio of C=O increased with increasing heat treatment temperature. It indicated that, under the high temperature of the heat treatment, the oxidation occurs not only at the Cu foil/sputtered Cu but also the LCP surfaces. We reported previously that the peel strength of laminated material made by the SAB method was improved by using Cu sputtering on the LCP film , . But after a heat-resistance test, the peel strength significantly decreased. This decrease resulted from the oxidation around the interface between the Cu foil/sputtered Cu and the LCP film due to gas permeation through the LCP film, and the softening of the Cu foil by its recrystallization due to high temperature. To prevent this loss of peel strength, we used Cu-0.02%Zr alloy foil with a higher recrystallization temperature and sputter Cu-Ni alloy or Ni-Cr alloy on the LCP film instead of Cu. It is also shown that the Cu/LCP materials produced by the SAB method have excellent electrical properties and etching ability.
Conference Paper: Cu/LCP laminated materials for new generation FPC[Show abstract] [Hide abstract]
ABSTRACT: As future materials for flexible printed circuits (FPCs) with high performance, we have studied copper clad lamination (CCL) materials of liquid crystal polymer (LCP) on copper (Cu) foil using a new laminating process, so called, surface activated bonding (SAB) method [1-5]. In previous report, it was found that the loss of peel strength during the heat-resistance test was improved by using copper-0.02% zirconium (Cu-Zr) alloy foil and a thicker sputter of copper-45% nickel (Cu-45Ni) or nickel-20% chromium (Ni-20Cr) alloys . These improved materials showed excellent interface conductivity at high frequency and etching property. In this report, we tried to produce more improved materials with different sputtering metals and investigated various characteristics of the laminated materials such as scattering parameter (S21), etching property, and dimensional stability for the FPCs. It was clarified that the sputter metal of higher nickel content alloys prevented from the interface oxidation of the Cu-Zr alloy foil/LCP film laminated materials (Cu-Zr/LCP materials) after heat-resistance test. Especially in copper-80% nickel (Cu-80Ni)or nickel-10% chromium (Ni-10Cr) alloy, the peel strength of the laminated materials kept around 500N/m even after 144 hour heating. The S21 of micro-strip line of the laminated materials showed half attenuation when comparing with that produced by the conventional heat bonding method. It is also shown that the Cu-Zr materials produced by the SAB method (SAB material) have excellent etching property and dimensional stability.
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ABSTRACT: A lamination technique for liquid crystal polymer (LCP)/Cu was developed for high speed and high performance printed circuit boards (PCB). This approach was accomplished by using a modified surface activated bonding (SAB) process to achieve enhanced adhesion and a smooth interface. Systematic investigation of peel strength of four categories of samples, namely “as bonded”, “annealed”, “Cu-deposited”, and “Cu-deposited and annealed” showed highest peel strength in the “Cu-deposited and annealed” sample. Significant improvements in adhesion were observed in the samples cleaned with argon-radio frequency (Ar-rf) plasma (“as bonded” samples) followed by Cu deposition on LCP, which were heated after bonding in low vacuum pressure at 240∘C (about 70–75 times higher than that of “as bonded”). XPS analyses on peeled surfaces of the “Cu-deposited and annealed” sample reveal bulk fracture in the LCP. Threefold lower loss in conduction of SAB processed laminate than that of conventional heat laminate was most likely due to smooth interface of the SAB processed laminate (surface roughness was ninefold lower than that of conventional heat laminate). A plausible adhesion mechanism of Cu/LCP might be due to bonding of Cu adhesion sites to plasma induced dangling sites of LCP surface, and thermal reconstruction of Cu deposited layers.
Conference Paper: Low temperature bonded Cu/LCP materials for FPC and its characteristics
Conference Paper: Low distortion cold rolled clad sheets for PWB[Show abstract] [Hide abstract]
ABSTRACT: New cladding process has been developed by means of a surface activated bonding (SAB) technique. In this process, surfaces of materials to be bonded are cleaned, activated by Ar ion sputter etching, and rolled with low distortion at room temperature in vacuum. This is available for cladding not only between heterogeneous metals but also between metal and polymer film. The clad sheets manufactured by this process have advantages over conventional clad sheets. For instance, they have a clean and flat interface without alloy layer. In addition, thickness of each layer is constant, even thin metal foil can be bonded with the metal foil or polymer film. In such respects the clad sheets with those features have been applied to PWB. Metal/metal clad sheets are suitable for selective wet etching working. The developed Cu/Ni/Cu 3-layer clad material makes it possible to form the 3D structure, containing the bumps and circuits, only by means of wet etching process. Metal/polymer clad materials composed of very thin rolled Cu foil and LCP Liquid Crystalline Polymer) film, are superior to the conventional materials from the point of fine etching property and high frequency property because of their smooth bonding interface. This paper reports the features of clad sheets manufactured by SAB and their applications to PWB.