Kyeong-Won Seol

Effects of plasma treatment on the peel strength of Ni on polyimide

In microelectronics packaging, the reliability of the metal/polymer interface is an important issue because the adhesion strength between dissimilar materials is often inherently poor. This paper reports the peel strength and surface morphology of a Cu/Ni/PI structure flexible copper clad laminate (FCCL) based on polyimide(PI) according to the pre-treatment atmosphere and times. Field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) were used to analyze the surface morphology, crystal structure and interface binding structure, respectively, of the sputtered Ni, Cu, and electrodeposited copper foil layers. The surface roughness of the Ni and Cu sputtered deposition layers and the crystal structure of the electrodeposited Cu layer changed according to the pre-treatment atmosphere and times of PI. The PI surface etching speeds and surface shapes differed according to the gas used in plasma preprocessing. The highest peel strength (mean 15.8 gf/mm) can be obtained in a preprocessing process for 400 seconds in an O2 atmosphere due to the increase in mechanical binding force and change in chemical binding structure caused by the increase in polyimide surface roughness.

Effect of Electrolyte Compositions on the Physical Property and Surface Morphology of Copper Foil

This study examined the effect of copper and sulfuric acid concentrations on the surface morphology and physical properties of copper plated on a polyimide (PI) film. Electrochemical experiments with SEM and a four-point probe were performed to characterize the morphology and mechanical characteristics of copper electrodeposited in the composition of an electrolyte. The resistivity and peel strength were controlled using a range of electrolyte compositions. A lower resistivity and high flexibility were obtained when an electrolyte with 20 g/l of copper was used. However, a uniform surface was obtained when a high current density that exceeded 20 mA/cm was applied, which was maintained at copper concentrations exceeding 40 g/l. Increasing sulfuric acid to >150 g/l decreased the peel strength and flexibility. The lowest resistivity and fine adhesion were detected at a Cu: H2SO4 ratio of 50:100 g/l. (Received March 23, 2010)

The effect of additives and current density on mechanical properties of cathode metal for secondary battery

Electrolyte copper foils used as a cathode material in secondary cells require the mechanical characteristic of high elongation ratios. In this study the effects of additives, current densities, and concentrations of sulfuric acid used in electrolyte plating on the mechanical characteristics of copper foils are analyzed. In the case of additive A, no significant changes in tensile strength and crystal structure were observed, but the elongation ratio is reduced by 43% when 100 ppm of additive is added. For additive B, the elongation ratio is rapidly decreased even though the growing orientation of crystals becomes parallel to the faces of (111) and (220) from the face of (200). In the case of decreasing current densities or increasing concentrations of sulfuric acid, the elongation ratio is respectively increased by 74% and 54%, and the growing orientation of crystals is directed from (200) to (111). Also, for additive A at low current densities, the increase in crystal sizes differed from that of high current densities. This approach represents a possible method for additionally improving elongation ratios by properly controlling the amount of the additive A.

The Effect of Hydroxy Ethyl Cellulose(HEC) on the Surface Morphology and Mechanical Characteristis of Copper Electrodeposition

The purpose of this study is to identify the effect of additives and composition on copper surface morphology and mechanical characteristics by copper electrodeposition. Additives such as hydroxy ethyl cellulose(HEC), chloride ion were used in this study. Electrochemical experiments allied to SEM, XRD, AFM and four- point probe were performed to characterize the morphology and mechanical characters of copper in the presence of additives. Among various electrodeposition conditions, the minimum surface roughness of copper foil was obtained when electrodeposited at the current density of 200 mA/ for 68 seconds with 2 ppm of HEC. The minimum value of surface roughness(Rms) was 107.6 nm. It is copper foil is good for electromigration inhibition due to preferential crystal growth of Cu (111) deposited in the electrolyte containing chloride ions(10 ppm) and HEC(1 ppm).

The influences of AlxGa1-xN layer on the characteristics of UV LED structure

Abstract We have studied growth characteristics of AlxGa1−xN/GaN epilayers which were grown with various x values and their effects on the characteristics of UV LED chips fabricated by AlxGa1−xN/GaN double heterojunction having different band offset. The van der Pauw technique, double crystal X-ray diffractometry (DCXRD), optical microscope and photoluminescence (PL) were used to characterize crystallographic, electrical and optical properties of each AlxGa1−xN epilayer. The device characteristcs of the fabricated UV LED chips were evaluated by measuring current – voltage (I–V) and light power–current (L–I) measurements were carried out. The PL spectra and the DCXRD results show that the dislocation density of AlxGa1−xN epilayer resulted from the difference of lattice mismatch between AlxGa1−xN and GaN and the FWHM increases by raising the Al incorporation. The turn-on voltage of the UV LED chips fabricated by AlxGa1−xN/GaN double heterojunction is less dependent on both the x value of AlxGa1−xN cladding layer and the related band offset (ΔEg). It was found that the optical power is strongly dependent on the dislocation density of each AlxGa1−xN cladding layer related to the individual x value.

Effect of Pulse and Pulse-Reverse Current on Surface Morphology and Resistivity of Electrodeposited Copper

Recently, requirement for the ultra thin copper foil increases with smaller and miniaturized electronic components. In this study, we evaluated the surface morphology, crystal phase ana surface roughness of the copper film electrodeposited by pulse method without using additives. Homogeneous and dense copper crystals were formed on the titanium substrate, and the optimum condition was 25% duty cycle. Moreover, the surface roughness(Ra), , is the smallest value in this condition. It is thought that this copper foil is good for electromigration inhibition due to the preferential crystal growth of Cu (111)

An Investigation of the Stability of Y 2 O 3 and Sintering Behavior of Fe-Based ODS Particles Prepared by High Energy Ball Milling

Abstract Fe-based oxide dispersion strengthened (ODS) powders were produced by high energy ball milling, fol-lowed by spark plasma sintering (SPS) for consolidation. The mixed powders of 84Fe-14Cr-2Y 2 O 3 (wt%) weremechanically milled for 10 and 90 mins, and then consolidated at different temperatures (900~1100 o C). Mechani-cally-Alloyed (MAed) particles were examined by means of cross-sectional images using scanning electron micros-copy (SEM). Both mechanical alloying and sintering behavior was investigated by X-ray diffraction (XRD) and highresolution transmission electron microscopy (HR-TEM). To confirm the thermal behavior of Y 2 O 3 , a replica methodwas applied after the SPS process. From the SEM observation, MAed powders milled for 10 min showed a lamellastructure consisting of rich regions of Fe and Cr, while both regions were fully alloyed after 90 min. The results ofsintering behavior clearly indicate that as the SPS temperature increased, micro-sized defects decreased and the den-sity of consolidated ODS alloys increased. TEM images revealed that precipitates smaller than 50 nm consisted ofYCrO

Effect of additives on the elongation and surface properties of copper foils

We report on the effects of additives on the mechanical properties of electrodeposited copper foils. Additives A (leveler), B (brightener) and C (Coll-A) are used in this study, and additive D is used as a Cl− ion. The study results show that there are large differences in surface roughness and elongation, according to whether the additives are added singly or in combination. In the case of additive D, its addition exhibits a high tendency to grow crystals in a (220) direction, and leads to increased elongation; however, it also exhibits the disadvantage of increasing surface roughness. The addition of all four additives results in a low surface roughness of less than 1 um, and shows low tensile strengths and uniform grain sizes. Here, the elongation is 15.6%, which represents an increase in elongation by 34% when compared to that of not adding additives.

Effect of Plasma Treatment Times on the Adhesion of Cu/Ni Thin Film to Polyimide

This study represents the results of the peel strength and surface morphology according to the preprocessing times of polyimide (PI) in a Cu/Ni/PI structure flexible copper clad laminate production process based on the polyimide. Field emission scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopywere used to analyze the surface morphology, crystal structure, and interface binding structure of sputtered Ni, Cu, and electrodeposited copper foil layers. The surface roughness of Ni, Cu deposition layers and the crystal structure of electrodeposited Cu layers were varied according to the preprocessing times. In the RF plasma times that were varied by 100-600 seconds in a preprocessing process, the preprocessing applied by about 300-400 seconds showed a homogeneous surface morphology in the metal layers and that also represented high peel strength for the polyimide. Considering the effect of peel strength on plastic deformation, preprocessing times can reasonably be at about 400 seconds. (Received March 4, 2011)

Effect of Kind and Thickness of Seed Metal on the Surface Morphology of Copper Foil

This study aimed to investigate the effects of the seed layer with copper electroplating on the surface morphology of copper foil. Three kinds of seed metal such as platinum, palladium, Pt-Pd alloy were used in this study. Electrodeposition was carried out with the constant current density of 200 for 68 seconds. Electrochemical experiments, in conjunction with SEM, XRD, AFM and four-point probe, were performed to characterize the morphology and mechanical characteristics of copper foil. Large particles were observed on the surface of the copper deposition layer when a copper foil was electroplated on the 130 nm thickness of Pd, Pt-Pd seed layer. However, a homogeneous surface, low resistivity was obtained when the 260 nm thickness of Pt, Pt-Pd alloy seed layer was used. The minimum value of resistivity was 2.216 at the 260 nm thickness of Pt-Pd seed layer.