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Young Ho Kim - One of the best experts on this subject based on the ideXlab platform.

  • The effect of solder wetting on Nonconductive Adhesive (NCA) trapping in NCA applied flip-chip bonding
    Journal of Materials Science: Materials in Electronics, 2016
    Co-Authors: Sun-chul Kim, Ja Yeon Lee, Tae Young Lee, Jae Yong Park, Young Ho Kim
    Abstract:

    Flip-chip bonding using a Nonconductive Adhesive (NCA) and the effect of solder wetting on NCA trapping were studied. Three different solder materials with different melting point were used for the bonding process: In–48Sn, Bi–42Sn, and Sn–3.5Ag. Additionally, the bonding process was performed at various temperatures. We measured the amount of NCA trapping as functions of the solder material and bonding temperature. The fillers and NCA were easily trapped between the solder and Cu pads. The amount of trapped fillers and NCA increased with softer solder materials. These trapped fillers and NCA could be reduced if the solder melted and reacted to Cu pads during the bonding process. However, if the solder melted after fully curing NCA, the trapped NCA was not reduced due to the low mobility of cured NCA. Therefore, in order to reduce NCA trapping, the solder should be melted before curing NCA. The electrical test results showed that the contact resistance increased with increasing amount of trapped fillers and NCA.

  • review paper flip chip bonding with anisotropic conductive film acf and Nonconductive Adhesive nca
    Current Applied Physics, 2013
    Co-Authors: Sun-chul Kim, Young Ho Kim
    Abstract:

    Abstract Recently, the flip-chip bonding technology using Adhesives has been widely used in the packaging industry because of environmental friendliness (elimination of lead material and flux cleaning), low temperature process (no soldering process), fewer processing steps (no underfill process), and the fine pitch capability. In flip-chip assembly using Adhesives, the electrical interconnection is established by mechanical contact between the bumps on the chip and the corresponding pads on the substrate after the Adhesive is cured. The Adhesive can be categorized into two types with respect to the presence of the conductive particles: anisotropic conductive film (ACF) and Nonconductive Adhesive (NCA). ACF is the Adhesive polymer film with dispersed conductive particles, and NCA is just Adhesive which contains no conductive particles. In this review, the bonding technologies with ACF and NCA are introduced, and the principle and characteristics of each bonding method are discussed.

  • Development of low temperature Chip-on-Flex (COF) bonding process of 100°C
    2012 14th International Conference on Electronic Materials and Packaging (EMAP), 2012
    Co-Authors: Sun-chul Kim, Young Ho Kim
    Abstract:

    Recently, many researchers have introduced low temperature bonding technology using Anisotropic conductive film (ACF) or Nonconductive Adhesive (NCA). In their studies, the bonding temperature is in the range between 150°C and 200°C. In this study, we developed a Chip-on-Flex (COF) bonding process of 100°C by using Sn-Ag bumps and Nonconductive film (NCF). Sn-Ag bumps were formed by electroplating and reflowed to form dome shape. The COF bonding was performed between Sn-Ag bumps and Cu/Polyimide film substrates using a thermo-compression bonder at 100°C for 5 s. The low temperature curable NCF was applied during the bonding process. The Sn-Ag bumps were deformed and direct contact was made between Sn-Ag bumps and Cu/PI substrate during thermo-compression bonding. The initial contact resistance of all joints was less than 30 mΩ, and no COF joints failed electrically. To evaluate reliability of COF joints, Temperature & Humidity (T&H) test (85°C/85% RH) was performed for 1000 hr. The contact resistance was increased during reliability test. However, the failed joints were not observed after T&H test. The contact resistance change will be discussed in terms of microstructure change in the COF joints.

  • The Effect of Fillers in Nonconductive Adhesive on the Reliability of Chip-on-Glass Bonding with Sn/Cu Bumps
    Materials Transactions, 2011
    Co-Authors: Byeung Gee Kim, Sun-chul Kim, Wenguo Dong, Young Ho Kim
    Abstract:

    The effect of a Nonconductive Adhesive (NCA) on the reliability of chip-on-glass (COG) bonding was studied. Double layer bumps consisting of dome-shaped Sn on Cu columns were formed by electroplating and a reflow process, and were used for this study. COG bonding was performed between the reflowed Sn/Cu bumps on the oxidized Si wafer and an indium tin oxide/Au/Cu/Ti/glass substrate using a thermocompression bonder. Three types of NCAs were applied during COG bonding: NCA-A with no fillers, NCA-B with fluoropolymer fillers, and NCA-C with silica fillers. Thermal cycling from 25 C to 125 C for 2000 cycles was performed to evaluate the effect of NCA type on the reliability of COG joints. The initial contact resistance values of the COG joints ranged from 32.2m to 39.3m . The contact resistance increased during the thermal cycling and the trend of contact resistance increment was different among three NCA types. The failure rate was the highest in NCA-C, followed by NCA-B and NCA-A in descending order. After the thermal cycling, the cross-sections of COG joints were observed with scanning electron microscopy to analyze the failure mechanism. The failures occurred primarily due to trapped fillers and NCAs at the interface between Sn/Cu bumps and the ITO substrate. [doi:10.2320/matertrans.M2011207]

  • Non-Conductive Adhesive (NCA) Trapping Study in Chip on Glass Joints Fabricated Using Sn Bumps and NCA
    Materials Transactions, 2008
    Co-Authors: Sang-mok Lee, Byeung Gee Kim, Young Ho Kim
    Abstract:

    Chip-on-glass (COG) bonding using a Nonconductive Adhesive (NCA) and the entrapment of NCA and fillers in the COG joints were studied. Sn was used as a bump material because it has a higher propensity of plastic deformation than an Au bump. Three types of Sn bumps were fabricated, electroplated Sn bumps, reflowed Sn bumps, and coined Sn bumps. Three types of NCAs were applied during COG bonding. The reflowed bump had the least amount of trapped NCA with fillers among the bumps studied. The NCA with the lowest viscosity was trapped the least compared to the other NCAs. The electrical test results showed that contact resistance increased with increasing amounts of trapped NCA with fillers in the COG joint.

Sun-chul Kim - One of the best experts on this subject based on the ideXlab platform.

  • The effect of solder wetting on Nonconductive Adhesive (NCA) trapping in NCA applied flip-chip bonding
    Journal of Materials Science: Materials in Electronics, 2016
    Co-Authors: Sun-chul Kim, Ja Yeon Lee, Tae Young Lee, Jae Yong Park, Young Ho Kim
    Abstract:

    Flip-chip bonding using a Nonconductive Adhesive (NCA) and the effect of solder wetting on NCA trapping were studied. Three different solder materials with different melting point were used for the bonding process: In–48Sn, Bi–42Sn, and Sn–3.5Ag. Additionally, the bonding process was performed at various temperatures. We measured the amount of NCA trapping as functions of the solder material and bonding temperature. The fillers and NCA were easily trapped between the solder and Cu pads. The amount of trapped fillers and NCA increased with softer solder materials. These trapped fillers and NCA could be reduced if the solder melted and reacted to Cu pads during the bonding process. However, if the solder melted after fully curing NCA, the trapped NCA was not reduced due to the low mobility of cured NCA. Therefore, in order to reduce NCA trapping, the solder should be melted before curing NCA. The electrical test results showed that the contact resistance increased with increasing amount of trapped fillers and NCA.

  • review paper flip chip bonding with anisotropic conductive film acf and Nonconductive Adhesive nca
    Current Applied Physics, 2013
    Co-Authors: Sun-chul Kim, Young Ho Kim
    Abstract:

    Abstract Recently, the flip-chip bonding technology using Adhesives has been widely used in the packaging industry because of environmental friendliness (elimination of lead material and flux cleaning), low temperature process (no soldering process), fewer processing steps (no underfill process), and the fine pitch capability. In flip-chip assembly using Adhesives, the electrical interconnection is established by mechanical contact between the bumps on the chip and the corresponding pads on the substrate after the Adhesive is cured. The Adhesive can be categorized into two types with respect to the presence of the conductive particles: anisotropic conductive film (ACF) and Nonconductive Adhesive (NCA). ACF is the Adhesive polymer film with dispersed conductive particles, and NCA is just Adhesive which contains no conductive particles. In this review, the bonding technologies with ACF and NCA are introduced, and the principle and characteristics of each bonding method are discussed.

  • Development of low temperature Chip-on-Flex (COF) bonding process of 100°C
    2012 14th International Conference on Electronic Materials and Packaging (EMAP), 2012
    Co-Authors: Sun-chul Kim, Young Ho Kim
    Abstract:

    Recently, many researchers have introduced low temperature bonding technology using Anisotropic conductive film (ACF) or Nonconductive Adhesive (NCA). In their studies, the bonding temperature is in the range between 150°C and 200°C. In this study, we developed a Chip-on-Flex (COF) bonding process of 100°C by using Sn-Ag bumps and Nonconductive film (NCF). Sn-Ag bumps were formed by electroplating and reflowed to form dome shape. The COF bonding was performed between Sn-Ag bumps and Cu/Polyimide film substrates using a thermo-compression bonder at 100°C for 5 s. The low temperature curable NCF was applied during the bonding process. The Sn-Ag bumps were deformed and direct contact was made between Sn-Ag bumps and Cu/PI substrate during thermo-compression bonding. The initial contact resistance of all joints was less than 30 mΩ, and no COF joints failed electrically. To evaluate reliability of COF joints, Temperature & Humidity (T&H) test (85°C/85% RH) was performed for 1000 hr. The contact resistance was increased during reliability test. However, the failed joints were not observed after T&H test. The contact resistance change will be discussed in terms of microstructure change in the COF joints.

  • The Effect of Fillers in Nonconductive Adhesive on the Reliability of Chip-on-Glass Bonding with Sn/Cu Bumps
    Materials Transactions, 2011
    Co-Authors: Byeung Gee Kim, Sun-chul Kim, Wenguo Dong, Young Ho Kim
    Abstract:

    The effect of a Nonconductive Adhesive (NCA) on the reliability of chip-on-glass (COG) bonding was studied. Double layer bumps consisting of dome-shaped Sn on Cu columns were formed by electroplating and a reflow process, and were used for this study. COG bonding was performed between the reflowed Sn/Cu bumps on the oxidized Si wafer and an indium tin oxide/Au/Cu/Ti/glass substrate using a thermocompression bonder. Three types of NCAs were applied during COG bonding: NCA-A with no fillers, NCA-B with fluoropolymer fillers, and NCA-C with silica fillers. Thermal cycling from 25 C to 125 C for 2000 cycles was performed to evaluate the effect of NCA type on the reliability of COG joints. The initial contact resistance values of the COG joints ranged from 32.2m to 39.3m . The contact resistance increased during the thermal cycling and the trend of contact resistance increment was different among three NCA types. The failure rate was the highest in NCA-C, followed by NCA-B and NCA-A in descending order. After the thermal cycling, the cross-sections of COG joints were observed with scanning electron microscopy to analyze the failure mechanism. The failures occurred primarily due to trapped fillers and NCAs at the interface between Sn/Cu bumps and the ITO substrate. [doi:10.2320/matertrans.M2011207]

L Elaadil - One of the best experts on this subject based on the ideXlab platform.

  • multiwalled carbon nanotube film for strain sensing
    Nanotechnology, 2008
    Co-Authors: Xifei Li, C Levy, L Elaadil
    Abstract:

    We have studied the possibility of using multiwalled carbon nanotube (MWCNT) films as strain sensors. The MWCNT films were prepared by a solution/filtration method and were bonded directly onto specimens by a Nonconductive Adhesive. For comparison, conventional foil strain gages were also bonded to the structure on the opposite side. The specimens then underwent a uniaxial tensile load–unload cycle to evaluate them as strain sensors. To ensure good electrical contact between carbon nanotube film and the wires, a thin layer of copper was thermally deposited on both ends of the film as electrodes, and the wires were connected to the electrodes by silver ink. Wheatstone bridges were used to convert the resistance changes of the MWCNTs to voltage output. Results indicated that the output voltages were proportional to the strain readings from the stain indicator. The effect of temperature on the resistance was measured and the MWCNT film resistance was found to be independent of temperature over the range 273–363 K. The optimal film dimension for strain sensing was evaluated as well. Dynamic tests suggest that the MWCNTs were able to extract the structural signature. Our results indicate that MWCNT film is potentially useful for structural health monitoring and vibration control applications.

Xifei Li - One of the best experts on this subject based on the ideXlab platform.

  • multiwalled carbon nanotube film for strain sensing
    Nanotechnology, 2008
    Co-Authors: Xifei Li, C Levy, L Elaadil
    Abstract:

    We have studied the possibility of using multiwalled carbon nanotube (MWCNT) films as strain sensors. The MWCNT films were prepared by a solution/filtration method and were bonded directly onto specimens by a Nonconductive Adhesive. For comparison, conventional foil strain gages were also bonded to the structure on the opposite side. The specimens then underwent a uniaxial tensile load–unload cycle to evaluate them as strain sensors. To ensure good electrical contact between carbon nanotube film and the wires, a thin layer of copper was thermally deposited on both ends of the film as electrodes, and the wires were connected to the electrodes by silver ink. Wheatstone bridges were used to convert the resistance changes of the MWCNTs to voltage output. Results indicated that the output voltages were proportional to the strain readings from the stain indicator. The effect of temperature on the resistance was measured and the MWCNT film resistance was found to be independent of temperature over the range 273–363 K. The optimal film dimension for strain sensing was evaluated as well. Dynamic tests suggest that the MWCNTs were able to extract the structural signature. Our results indicate that MWCNT film is potentially useful for structural health monitoring and vibration control applications.

C.p. Wong - One of the best experts on this subject based on the ideXlab platform.

  • Conductive Adhesives for Flip-Chip Applications
    Advanced Flip Chip Packaging, 2013
    Co-Authors: Daoqiang Daniel Lu, C.p. Wong
    Abstract:

    Significant progress has been made to improve electrically conductive Adhesive (ECA) and Nonconductive Adhesive (NCA) technology. Recent material development of various anisotropic conductive Adhesives/films (ACAs/ACFs) and their applications in flip chip are reviewed first. Then research achievements in material development and in electrical and mechanical aspects of isotropic conductive Adhesives (ICAs), and their applications in flip chip and advanced packages are reviewed in details. In addition, latest advances of NCA technology for flip-chip applications are also reviewed.

  • Novel lead free nanoscale Nonconductive Adhesive (NCA) for ultra-fine pitch interconnect applications
    56th Electronic Components and Technology Conference 2006, 2006
    Co-Authors: Kyoung-sik Moon, C.p. Wong
    Abstract:

    Recently, non-conductive Adhesive (NCA) bonding technology has attracted increasingly research interests as lead-free interconnect due to the fine pitch capability and low cost. The NCA usually requires no conductive tillers, but needs a relatively high pressure for bonding between the IC chip and the substrate coupled with heat. During bonding, the heat and pressure are applied for some time and the direct physical contact between the two surfaces of the IC bump and the substrate bond pad can be made with NCA resin curing/solidification. Contact of bottom and top pads/electrodes, via their up-and-hill (represents the uneven bond pads surfaces) surface structures, leads to the electrical conduction of NCA joints. In order to create the electrically conductive NCA joints, relatively high pressure and high degrees of the solidification of the polymer resin are required. This paper introduces a novel lead-free nanoscale NCA interconnect material with trace amount of in-situ formed nanoconductive fillers. These uniformly distributed nanosized conductive fillers were in-situ formed in the epoxy resin and were well dispersed within the polymeric matrix. As such, the novel NCA joints were formed with lower bonding pressures and exhibited an improved electrical performance without sacrificing the fine pitch advantages of NCAs. The dramatic improvement was attributed to the enhanced interface properties by the nanoconductive fillers, which assisted the electrons tunneling and current flow.