Polyimide (PI) was successfully hybridized with silica and PDMS by synchronizing two reactions; imidization of poly(amide acid) (PAA) and sol-gel reaction of tetraethoxysilane (TEOS) and diethoxydimethylsilane (DEDMS). TEOS and DEDMS were used as precursors for the formation of silica and polydimethylsiloxane (PDMS), respectively. The progress of sol-gel reaction was confirmed by IR. It was revealed from the study of scanning electron microscopy that silica has better compatibility than PDMS. The effect of the silica and PDMS on the mechanical and thermal properties of the hybrids was studied. Hybrid containing 3-5 wt% of silica and 3-5 wt% of PDMS gave the highest tensile properties. Dynamic viscoelastic analyses and thermogravimetric analyses revealed that thermal properties were improved by the hybridization.

View full abstract

Three different polymerization methods were studied for the A₂ + B₃ polymerization to provide a TEMPO functionalized polyimides. The one-pot polymerization/imidization and the precipitation polymerization provided a microporous polyimide and a spherical polyimide, respectively; however, the functionalization of the terminals was difficult. In contrast, the solution polymerization with a drop-wise feeding method provided a hyperbranched polyimides and the terminals have been successfully functionalized with TEMPO by the in-situ end-capping reaction. This polymerization and end-capping method will be applicable for the introduction of other various functionalities and might result in the development of various novel polyimide materials.

View full abstract

A diamine, 2,4-diaminophenylethynylbenzene (DAPEB), that have pendant phenylethynyl group, was synthesized. Utilizing DAPEB as one component, a novel soluble polyimide (PI), Solpit-T, that can be thermally cured was synthesized. Solpit-T is soluble prior to curing, but became insoluble in organic solvents after curing, showing improvement in chemical resistance. In addition, cured Solpit-T films revealed large elongation at break; 8% and 39% at 33 mol% and 8 mol% DAPEB in total diamine, respectively, showing that cured Solpit-T has outstanding toughness for thermosetting PI. Cured Solpit-T films have T_g s as high as above 400 °C from the DMA measurement, which is the same as the Solpit-S and PI(PMDA/ODA). Thermogravimetric analyses revealed that 5 % weight loss temperatures were higher than 450 °C.

View full abstract

We fabricated thermosetting maleimide polymers with excellent thermal and optical properties by the sequence-controlled radical copolymerization of N-allylmaleimide (AMI) and N-(2-ethylhexyl)maleimide (EHMI) with diisobutylene (DIB) and postpolymerization reactions. The AAB-type maleimides/DIB copolymers randomly containing an allyl group in the side chain were thermally or photochemically cured using pentaerythritol tetrakis(3-mercaptobutyrate) as a polyfunctional thiol by thiol/ene reaction. The organic-inorganic hybrid was also fabricated by the thiol/ene reaction of the maleimide copolymers containing allyl side groups combined with surface-modified silica nanoparticles. The produced organic-inorganic hybrid was dispersed in tetrahydrofuran. The transparent films of the maleimide copolymers containing the hybrid were obtained by casting and drying. The crosslinked polymers and the organic-inorganic hybrid obtained in this study exhibited excellent thermal stability as well as the high transparency.

View full abstract

Addition-type phenylethynyl-terminated imide oligomers were synthesized from 4,4’-diaminodiphenyl ether(ODA), 4-phenylethynylphthalic anhydride (PEPA) and 3,3’,4,4’-biphenyltetracarboxylic dianhydride (BPDA) or 4,4’-hexafluoroisopropylidene)- dianhydrid (6FDA), and preparation of nanopatterned polyimide was examined by imprinting the melted phenylethynyl-terminated imide oligomer and crosslinking the ethynyl groups. Crosslinked polyimide films were prepared by pressing the melted phenylethynyl-terminated imide oligomers and curing them under pressure at 370 °C afterward, and the properties of the polyimide films were studied for comparison. The crosslnked polyimide films had high glass transition temperature (Tg) above 320 °C, and showed excellent tensile strength more than 100 MPa. Nanopatterned polyimide was prepared by imprinting the melted imide oligomer with a metal mold and curing it under pressure at 370 °C afterward. ZEONOR^(R) film could be imprinted using the imprinted and cured imide oligomer as sub-mold instead of the metal mold.

View full abstract

A novel terphenyl diamine monomer, 4-[3,5-Bis(3-aminophenyl)benzophenone] phenyl 3,4,5-tris(decyloxy)benzoate (TerKetone) having three long-chain alkyl groups connected by phenylester and benzophenone linkages was synthesized via several step reactions from Gallic acid methyl ester. The novel polyimides and copolyimides were synthesized from 3,4’-ODPA as a dianhydride, TerKetone, and 4,4’-diaminodiphenylether (DDE) as a diamine co-monomer by two step polymerization systems. The thin films of obtained polyimides were irradiated by UV light (λmax; 254 nm), and the contact angles for the water decreased from near 100° (hydrophobicity) to near 40° (hydrophilicity) in proportion to irradiated UV light energy. From the result of surface analyses (ATR, XPS, AFM), it is recognized that the hydrophobic long-chain alkyl groups on the polyimide surface decrease and the hydrophilic groups such as hydroxyl groups and carboxyl groups generate on their surface. Furthermore, it was observed that the incorporation ratios of TerKetone in copolyimides affected the changes of wettability by UV light irradiation.

View full abstract

The alicyclic dianhydride having cyclopentanone bis-spironorbornane structure (CpODA) was polycondensated with aromatic diamines at room temperature to give poly(amic acid)s having an inherent viscosity (η_inh) range of 1.3-0.54 dL/g. The poly(amic acid)s were imidized by three methods. The imidization ratio of PI(CpODA+3,4’-DDE) reached 100% at 200 °C using a combined chemical and thermal imidization method. All the polyimide films possessed excellent thermal stability and most of the polyimides had Tg’s over 330 °C. The CTE value of thermally imidized PI(CpODA+4,4’-DABA) was as low as 15 ppm/K. The polyimide films exhibited λ_cut-off’s shorter than 336 nm, and the T_vis value of each polyimide film was over 85%. Especially, PI(CpODA+3,4’-DDE) prepared by a combined chemical and thermal method had outstanding optical properties (T_vis:88 %, λ_cut-off’s:278 nm) due to the low temperature film-fabrication.

View full abstract

There can be two kinds of de-bonding options in the aspect of the releasing interface, one is carrier release and the other is device wafer release. Thermoplastic adhesives are used in most cases for carrier release because the materials can easily be cleaned by solvent. On the other hand, device wafer release is usually selected for thermoset adhesives, which is difficult to remove by solvent.

View full abstract

Poly(p-phenylene benzobisoxazole) (PBO) has excellent thermal stability and mechanical properties because of its rod-like rigid structure. Preparing nanofibers of PBO using ordinary methods is difficult (e.g., electrospinning) because PBO is not soluble in organic solvents. Herein, we report the preparation of PBO nanofibers with an average diameter of approximately 50 nm via crystallization from a dilute solution in sulfuric acid. In addition, a PBO nanofiber mat was prepared that exhibited extremely high thermal stability and high thermal diffusivity, etc.

View full abstract

Aromatic polyimides are considered to be a class of high performance polymers, and they have found a wide range of applications in electronics, aerospace and other industries. They were developed in the 1960s owing to intensive research on heat-resistant polymer. Polyimides in various forms (film, composite matrix, adhesive, plate, etc) were developed now. However, the particle of polyimides were studied only a little until the latter half of the 1990's. Even if polyimides are processed to the particle shape, the particles can be expected to show excellent features. Then, we zealously examined the preparative procedure of polyimide particles, and established the following two methods. (1) Several kinds of polyamic acid particles were prepared using diamines and anhydrous tetracarboxylic acids through precipitation polymerization in organic solvent under ultrasonic irradiation. These polyamic acid particles were heated by about 140-200 °C, and the polyimide particles were obtained. The polyimide particles of an arbitrary size were able to be prepared by this method within the range of submicron order. Moreover, it was also possible to support functional groups to surfaces of the polyimide particles. (2) Polyimide particles of micron order were obtained by heating polyamic acid varnish at about 140-200 °C that induced the thermal imidization of polyamic acids in aproticpolarsolvent. Similarly, it was also possible to support functional groups to surfaces of the polyimide particles by this method.

View full abstract

A series of polyimide (PI)/silver composite films incorporating μm-sized metallic silver particles (Ag-MPs) were prepared using matrices of sulfur- (SD), fluorine- (TF), and silicon-containing (SIM) PIs as well as an immiscible blend of SD- and TF-PIs (b-SF). The thermal conductivity (λ_⊥) of the composited films accords well with the calculated value (λ_cal) based on the Bruggeman model below the particle contents (φ) of 30 vol%, whereas the composite films of SD/Ag and b-SF/Ag exhibited extraordinarily larger λ_⊥ values than λ_cal in the range of φ>30 vol%. Moreover, the λ_⊥s of SD/Ag films with uniform dispersion of Ag-MPs are almost equivalent to those of b-SF/Ag films in which Ag-MPs are selectively dispersed in the SD phase. In contrast, the λ_⊥s of SIM/Ag films with homogeneous dispersion accord well with the λ_cal and much smaller than those of SD/Ag and b-SF/Ag. These facts indicate that effective thermal conductive paths were spontaneously generated in SD/Ag films as well as in b-SF/Ag films.

View full abstract

A series of composite films composed of μm-sized aluminum nitride (AlN) particles and polyimides (PIs) were fabricated using (a) rigid-chain sBPDA-PPD (sBPPD) PI and (b) flexible-chain sBPDA-ODA (sBPOD) PI as matrices. The relationship between their morphological structures and thermophysical properties were investigated by analyzing cross-sectional SEM images and by measuring out-of-plane thermal conductivity (TC_⊥) and in-plane coefficients of thermal expansion (CTE_//). The sBPPD chains exhibited a better polymer-filler packing behavior due to their rigid structure having small free volume. Both TC_⊥ and CTE_// of AlN-filled sBPPD films showed positive deviations from theoretical predictions, whereas no such behavior was observed in AlN/sBPOD composites or in sBPPD films filled with highly anisotropic hexagonal boron nitride (hBN) flakes. The enhanced TC_⊥ and CTE_// observed for the sBPPD composites can be attributed to a significant change in the orientational state of the PI chains; in-plane orientated sBPPD chains in the pristine PI film become distorted by incorporation of isotropic AlN particles.

View full abstract

In recent years, novel electronic products have become dramatically smaller and more highly functionalized. Based on these market trends, packaging structures for semiconductors are also required to become smaller, thinner and more complicated. To satisfy various requirements, packaging technologies such as WL-CSP, FO-WLP. 2.5D interposer, 3D-TSV, and so on, are used. For these packaging structures, the photo-sensitive organic materials used for buffer coating, passivation layers, and insulators for re-distribution are required to exhibit low temperature curability and low residual stress. To meet these requirements, we have developed a low temperature curable (around 200°C) photo-sensitive insulator. The design concept of our photo-sensitive insulators is based on phenolic resins as the main component to perform good lithography and cross-linkers containing epoxy functional units. Moreover, our photo-sensitive insulators contain naphtoquinone diazide (DNQ) compounds commonly used in positive tone resists. Specifically, we have developed new phenolic resins containing flexible units. Our photo-sensitive insulators containing the new polymer showed low residual stress, low elastic modulus, good chemical resistance and good lithography performance.

View full abstract

The novel negative-type photosensitive polyimide precursor to protect ELK for Flip-chip package was developed. High modulus was achieved by the rigid structure of main polymer, and film transparency was achieved to modify the side chain unit by tuning the ratio of particular non-acryloyl groups and acryloyl groups. This polyimide composition showed high modulus value (nearly 6.0GPa) and could pattern by i-line. This polyimide composition also showed high chemical resistance property. Thus, this polyimide composition will be suitable for Flip-chip package to protect ELK as surface protective and interlayer dielectric film.

View full abstract

An alkaline-developable positive-type photosensitive polyimide (PSPI) based on fluorinated poly(amic acid) (FPAA) and fluorinated diazonaphtoquinone (FDNQ) as a photoactive compound has been successfully developed as a promising material for use in microelectronics. The FPAA was prepared from 4,4’-(hexafluoroisopropylidene)diphtahlic anhydride and aromatic diamines, 4,4’-oxydianiline (80 mol%), and 4,4’-oxybis(4-phenoxyaniline) (20 mol%). The PSPI consisting of FPAA, catechol (3 wt% to FPAA), and FDNQ (25 wt % to FPAA) showed a high sensitivity of 45 mJ/cm² and a high contrast of 10 when it was exposed to a 365 nm line (i-line), and developed with 2.38 wt % TMAHaq for 10 seconds at room temperature. A clear positive image of a 6-μm line and space pattern was printed on a film, which was exposed to 80 mJ/cm² of i-line by a contact printing mode. Thus, this system will be a good candidate for next generation PSPIs.

View full abstract

We investigated mechanism of the dissolution of HBPE-NO₂ films to the developer by analysis of the developer after development. A HBPE-NO₂ film containing BADNQ2 was irradiated with 500 mJ/cm² of exposure dose and developed with 25wt% TMAHaq. The developer was then neutralized by HClaq. and the solution was evaporated and dried at 90 °C in vacuo. ¹H-NMR spectrum of the resulting product after development is shown in Fig. 3. The 1H-NMR spectrum shows signals assigned to the monomers, terephthalic acid derived from TPC and THPE, and 4-nitrobenzoic acid derived from the end groups. However, no signal that can be assigned to the original HBPE-NO₂ protons was observed. This result suggests that RDP of HBPE-NO₂ is not based on solubilization of the polymer by the reaction at the end groups but on decomposition of the polymer induced by nucleophilic attack of the OH^- to the ester linkages to give low-molecular-weight products.

View full abstract

We developed PBG 2 that generates radical and primary amine by UV irradiation. PBG 2 worked effectively for radical polymerization of methacrylate groups and base-catalyzed cross-linking reactions of alkoxysilyl groups in MA-PS.

View full abstract

The authors concluded in this paper that the proton of the ethenylene with the chemical shift at higher magnetic field is located next to sulfur referring the experimental results reported by Klemm et al. with 4-nitro-thienopyridine derivatives. However it is notable that assignments of H-2 and H-3 may be reversed. In cases of ¹³C NMR, the results from HSQC indicate the carbons directly attaching to hydrogen atoms and those from HMBS indicate long range coupling in 2-3 carbon sequences. Especially, even in 1D spectroscopy, the carbons locating at distinctively low magnetic field, around 161 ppm for C-9a and 145-147 ppm for C-8a, showed good match with the results previously reported and are key to determine the baseline structure of the products. Authors finally conclude that a 4-cyanothienoquinoline base-structure reasonably explains the experimental results obtained without any contradiction and that the chemical structure of Product A and B.

View full abstract

TBzM and DBzM were newly prepared as novel photolabile crosslinkers. The crosslinkers were photopolymerized to form networked structure that were able to decrosslink on irradiation at 254 nm.

View full abstract

Cost of silicon carbide (SiC) wafer has been improved owing to the development of larger and higher quality wafer technologies, while the process stays long and complicated. In this paper, we propose a novel short process of ion implantation and fabricate model SiC schotky barrier diodes (SiC-SBDs) devices. Currently common mask layer of ion implantation employs high heat resistant materials such as metal oxides. Because the ion is implanted to SiC wafer at high temperature between 300 °C and 800 °C due to avoiding the damage of SiC crystal structure. The process using oxide layer tends to became long and complicated. On the other hand, our proposal process uses a heat resistant photoresist material as the mask instead of the oxide layer. The heat resistant photoresist is applied to newly developed “SP-D1000” produced by Toray Industries, Inc.. We demonstrated to fabricate the model SiC-SBDs devices based on our proposal process with “SP-D1000” and confirmed the device working as same as a current process.

View full abstract

Laser resist stripping for the ion-implanted novolak resist was successfully performed without occurring laser damage to the Si wafer. In order for the advanced　laser resist stripping method to be successful, it is important for the pulsed laser beam to pass though the ion-implanted resist and absorb into the Si wafer surface. The novolak resists which are implanted with B, P, and As ions, respectively, were irradiated with a pulsed 532nm laser. Regardless of the implanted ion species and density, more than 74 % of the laser power was found to absorb into the Si wafer surface. For the laser irradiation of 1 pulse, the ion-implanted resist with a density of 5.0 X 10¹³ atoms/cm² was completely stripped in the same way as that of a non-implanted resist. The optical absorption of the resist surface increased as the density of the ion-implantation increased. In case of the ion-implanted resist with a density of 5.0 X 10¹⁵ atoms/cm², the resist was stripped by 20 pulses irradiation without occurring laser-induced surface damage. A scanning removal of the highly ion-implanted resist was also successfully stripped by using an optimized irradiation condition. A highly ion-implanted resist was continuously stripped by the scanning laser irradiation with 20 pulses.

View full abstract

Bottom-up self-assembly has the capacity to overcome the limitation of top down nanofabrication. Recently, nanoparticles or molecules are expected to use as the building blocks. By using them it is desirable to place nanometer sized components such as nanopartilces in exact positions for nano-fabrication with high precision and reproducibility. In particular, gold (Au) nanoparticles, which covalently linked to biomolecules such as DNA, peptides, nucleic acids, proteins, and cell have attracted much attention for biosensing application, bioimaging application and so on. In this study, we present a novel and simple method of position control of Au nanoparticles on a nanopattern by self-assembly techniques such as block copolymer phase separation and self-assembled monolayers. Spherical Au nanoparticles were immobilized above the Au nanopatterns with a gap of a few nanometers. We believe this method will contribute to studies on the observation of single biomolecules such as DNA, peptides, nucleic acids, proteins, and so on.

View full abstract

A novel process for the fabrication of flexible, semitransparent, and meshed gold electrodes on a polyethylene terephthalate (PET) substrate utilizing transfer printing from a self-organized microporous polycarbonate mold is described. The mold, with honeycomb structures, was fabricated by casting a chloroform solution of poly(bisphenol A carbonate) and polyacrylamide to form selforganized arrays of water bubbles and drying them. The meshed Au electrode was transferred on a PET substrate coated with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) using the Au-coated mold. The measured transmittance of the electrode at the photon wavelength of 500 nm was 34%, and the sheet resistance was 3 Ω/square. Fabricated Au mesh electrode showed a much greater flexibility than the ITO electrode, and it can be bent to 7.5 mm radius of the curvature with 10% reduction of the conductance.

View full abstract

A new method for fabricating metal dies for the use of micro-lens array molding or stamping was proposed and investigated. As a metal, nickel was used, and the nickel dies were fabricated by replicating the primary resist molds that were directly printed using projection lithography on silicon wafers coated with approximately 10-μm thick positive resist PMER P-LA900PM. Lens array patterns with quasi-spherical cross sections were printed by selecting a wavelength of 405-nm, defocuses between +100 and +200 μm and exposure times of 20-30 min. After printing resist mold patterns of a lens array, a thin gold film was spattered on it, and nickel was electroplated next. The aimed nickel dies were obtained by removing the resist molds from the electroplated nickel blocks. The diameters of nickel dies were faithfully corresponded to those of the resist molds. In addition, the surfaces of nickel dies were very smooth, and the peak-to-valley roughness was almost less than a quarter of visible light wavelengths. The new method will be promisingly effective for fabricating micro-lens arrays.

View full abstract

The dual site silane coupling agent was synthesized by thiol-ene reaction. Zirconia nanoparticles could be dispersed effectively by using it. Surface bonded phtalic acid esters acted as a plasticizer to provide a good compatibility with photo-curable acrylates. High refractive index hybrid thin film indicated high transparency even though high nanoparticle contents. Therefore, hybrid thin films with photo-cured acrylates are possible to control their refractive index, and they will be expected to apply to optical materials.

View full abstract

Novel photoresponsible emission switching molecules were prepared, and their photochemical and photophysical properties were determined.

View full abstract

Novel photoresponsible chiral supramolecule 4SES was prepared and its chiral switching and thermal stability were measured. 4SES shows reversible CD change up on photoirradiation, due to face angle change of binaphthyl group induced by trans-cis photoiromerization. The cis isomer of 4SES has high thermal stability whose absorption does not change even by heating at 100 ° for 2 hours, which is quite contrast to the case of 3RAA. 4SES is expected as the potential materials for chiral optical data storage, asymmetric synthesis, and so on.

View full abstract

Photo-mechanical gels containing sensiteizes were prepared and their volume change by photoirradiation was investigated. The volume change of the gels was induced by the photoirradiation via photosensitization. The induced photochemical change was memorized in αCD-Azo gels which continue to volume change even after photoirradiation in dark.

View full abstract

The conditions around the AuNPs in a solution could be controllable by changing the method that is used to wash them. However, the ZP measure- ments indicated the presence of negative charges, which indicates that the number of anions located within the HD of the NPs should be larger than the number of cations. In this study, AuNPs were initially coated with CTAB(1). To maintain the negative ZP of the AuNPs after they have been coated with neutral PEG(3), the NP surface must contain more anions than cations. Br mapping is observed to be an ineffective method for tracing CTAB(1) cations (counter ion is Br^-) because of polymer-CTAB(1) or polymer-Br^- interactions. SDS(4) showed strong interactions with CTAB(1) partly aggregated on the TEM grids. Based on these results, we observed some interesting relationships between polymer and particle charges. We expect to improve the mixing and washing procedures in future.

View full abstract