Weixin Fu

Low-temperature direct heterogeneous bonding of polyether ether ketone and platinum

Direct heterogeneous bonding between polyether ether ketone (PEEK) and Pt was realized at the temperatures lower than 150°C. In order to create sufficient bondability to diverse materials, the surface was modified by vacuum ultraviolet (VUV) irradiation, which formed hydrate bridges. For comparison, direct bonding between surfaces atomically cleaned via Ar fast atom bombardment (FAB) was conducted in a vacuum. The VUV irradiation was found to be effective for creating an ultrathin hydrate bridge layer from the residual water molecules in the chamber. Tight bonds were formed through dehydration of the hydrate bridges by heating at 150°C, which also contributed to enhancing interdiffusion across the interface. The VUV-modified surfaces showed bondability as good as that of the FAB-treated surfaces, and the VUV-modified samples had shear strengths at the same level as those of FAB-treated surfaces. This technology will be of practical use in the packaging of lightweight, flexible biomedical devices.

A study on low temperature SAM modified POM direct bonding affected by VUV/O 3 irradiation

A direct bonding of polyoxymethelene (POM) was feasible at 100 °C by using self-assembled monolayers (SAM) as surface modification method. (3-Aminopropyl)triethoxysilane (APTES) and (3-Glycidyloxypropyl)trimethoxysilane (GOPTS) were applied in our work. Surface modification carried out with different VUV/O3 irradiation conditions showed different bonding strength. In addition, the bonding condition with highest strength had an average strength of 0.37 MPa. This technology was expected to be used in packaging for micro/nano electromechanical systems (MEMS/NMES), such as bio-/medical devices.

Low temperature direct bonding of single crystal quartz substrates for high performance optical low pass filter using amorphous SiO2 intermediate layers

We proposed a HF-assisted single crystal quartz direct bonding method at low temperature using amorphous SiO2 layer for high performance optical low pass filter (OLPF) to improve heat resistance compared with conventional OLPFs using UV-curing adhesive. Amorphous SiO2 was deposited by ion beam sputtering on backside of both infrared reflection and anti-reflection coated substrates. By the etching rate evaluation, amorphous SiO2 deposition is considered to provide high active surface useful for bonding. The HF bonded sample with amorphous SiO2 layer achieved 0.8 MPa in tensile test and 3.3 MPa in shear test, and also nearly 100 % light transmittance was performed, which is as the same level as conventional UV-curing adhesive one. Therefore, the proposed single crystal quartz direct bonding with amorphous SiO2 layers is considered to be a promising technique to realize high performance OLPFs.

Low temperature direct bonding of polyether ether ketone (PEEK) and Pt

The direct bonding between polyether ether ketone (PEEK) and Pt was feasible at 150 °C via the surface modification using vacuum ultraviolet (VUV). This technology will be of practical use in the eco-friendly fabrication of light-weight and bio-inert electronic system, such as a body-implantation medical device. The VUV irradiation helped creating the bridging layers, which consisted of hydroxyl groups due to the residual water molecules inside the bonding chamber, both on PEEK and Pt surfaces. Upon heating at 150 °C, the Pt ions diffused into PEEK side as the micro-grains at the PEEK-Pt interface, and a voidless interface was successfully obtained with the calculated bonding strain release energy of around 4.2 N/m. This energy is higher than the surface energy of both PEEK and Pt.

Low temperature direct bonding of polyoxymethylene (POM) through self assembly monolayer (SAM)

Direct bonding of polyoxymethylene (POM) at 100 °C was feasible using self-assembly monolayers (SAM). The POM substrates were first activated by vacuum ultraviolet irradiation in presence of oxygen gas (VUV/O3) and then modified with SAM: (3-Aminopropyl)triethoxysilane (APTES) and (3-Glycidyloxypropyl)trimethoxysilane (GOPTS), respectively. Fourier transform infrared spectroscopy showed that both APTES and GOPTS modifications were successful. The bonding reached an average bonding strength of 0.37 MPa, and bulk fracture was observed after the debonding test. Surface observation results showed VUV activation process time played an important role in bonding. This technology is expected to be applied in future bio-inert electron devices.

Low Temperature Direct Bonding between PEEK (Polyetheretherketone) and Pt via Vapor-Assisted Vacuum Ultraviolet Surface Modification

Direct bonding between PEEK (polyetheretherketone) and Pt was achieved at 150 °C via a vapor-assisted VUV (vacuum ultraviolet) surface modification method. X-ray photoelectron spectroscopy confirmed that the PEEK and Pt outer surfaces were modified with hydrate bridge layers. A model calculation of gas content during VUV irradiation suggested that the water vapor molar concentration should be optimized to no more than 0.088 mol/m. The strain energy release rate calculation indicated that the energy required to debond the PEEK-Pt interface reached 270 mN/m, which was higher than the energy required to break the bulk PEEK (42 mN/m). SEM observation of fractured PEEK-Pt bonding agreed well with the calculation result that the fracture occurred within PEEK substrate. Thus, the PEEK-Pt bonding was considered strong enough. This technology is expected to be applied in biomedical MEMS applications.

VUV/O3 assisted single crystal quartz bonding with amorphous SiO2 intermedicate layer for manufacturing optical low pass filter

We proposed a single crystal quartz direct bonding method utilizing amorphous SiO2 intermediated layers, which can improve heat resistance of the optical low pass filter (OLPF) by novel fabrication method. An amorphous SiO2 was deposited on the opposite sides of both infrared reflection and anti-reflection coated substrates to prepare the highly activated surfaces. The substrates were bonded at 200 °C after the vacuum ultraviolet (VUV) /O3 pre-treatment. The bonded sample with amorphous SiO2 layer shows 5 times higher tensile strength than that without amorphous SiO2 layer while it keeps nearly 100% of light transmittance. These results indicate that amorphous SiO2 layer could prepare activate surface even in low vacuum bonding condition. This single crystal bonding method will be useful for realizing high performance OLPFs

Low temperature direct bonding of PEEK and Pt through VUV/FAB surface treatments

A direct hybrid bonding of PEEK-Pt is feasible at low temperature of 150 °C through surface treatment technologies of vacuum ultraviolet (VUV) and fast atom bombardment (FAB). The X-ray photoelectron spectroscopy showed the VUV treatment was capable of creating hydrate bridge layers on both PEEK and Pt surfaces, which were considered to form a robust bond through dehydration reactions. Shear strength test showed that the VUV-treated samples were stronger than the FAB-treated ones, and the highest strength reached 0.91 MPa, which was comparable with conventional PEEK-based direct bondings. This technology is expected to be applied in future body implantable medical micro electromechanical system devices.

Low Temperature Bonding between Polyether Ether Ketone (PEEK) and Pt through Vapor Assisted VUV Surface Modification

The direct bonding between polyether ether ketone (PEEK) and Pt was feasible at low temperature of 150 °C through vapor assisted VUV treatment. This technology was expected to be applied in future body implantable devices for medical applications. The carboxyl functional groups were created on the PEEK surface during the vapor assisted VUV treatment, as well as the hydrate compound was formed on Pt surface. The highest bonding strength and surface release energy reached 1.15 MPa and 4.6 × 10-1 N/m, respectively, which was considered strong and comparable with conventional PEEK-based direct bonding.

Low temperature and low pressure bump bonding realized by single-micrometer Ag-nanoparticle bumps

A bonding method using single-micrometer bumps, which were formed by Ag nanoparticle, had been realized under low bonding temperature and low compressive stress. The bump diameter is 8 μm and the pitch is 16 μm. The bonding temperature was 250°C under compressive stress of about 41.4 MPa. A shear test was carried out and the strength of the bond could reach 5.89 MPa.