Needle-like probe holds fine objects by adhesions without any holding devices. It can not pick up heavy and large objects, because the gravity rivals the adhesions. Referring to electrostatic chucks (ESCs), we fabricated two needle-like probes, of which adhesions are assisted by the electrostatic force, a monopole probe and a dipole probe. The former corresponds to monopolar ESCs and the latter corresponds to dipolar ESCs. By the assistant of an external electric power, both can pick up heavy and large objects. The monopole probe, which is a tungsten needle, can manipulate 40-80μm gold particles on a gold substrate as follows. The probe is lowered until it touches the particle. After 20-50V is applied between the probe and the substrate, the probe is pulled up. Then the particle is picked up with the probe. Once the particle is in the air, it stays at the tip of the probe even if the voltage is reduced to 0. For release of the particle, the probe is lowered until the particle touches the substrate and is pulled up without applying voltage. The dipole probe is made of two electrodes embedded in an epoxy resin. Different from the monopole probe, the dipole probe attract both conductive and dielectric objects over a gap. The probe jumps up a styrene particle of 3mm over the gap of 1mm by applying 2kV, and it jumps up a gold particle of 0.4mm over the gap of 0.5mm by applying 5kV. The release is possible only by turning the applying voltage off. As the gravity is greater than the adhesions, the objects adhered falls. The assistant electrostatic force of the monopole probe is Johnsen-Rahbek force same with the clamping force of monopolar ESCs, and that of the dipole probe is gradient force same with the clamping force of bipolar ESCs.
We fabricated an apparatus for manipulation and welding of fine metal objects using a probe. The apparatus is composed of a work probe of a tungsten alloy needle, stages, a DC power supply, and an observation system. The work probe is held vertically above a gold substrate placed on stages to control the relative position against the work probe. The DC power supply is equipped to apply voltage of 0-10kV between the work probe and the substrate. One application of the apparatus is to repair probe cards. Thousands of contact probes (needles) are mounted on the printed circuit board (PCB) in the probe card. The contact probes are mounted one by one by the hands. Recently, an array of the contact probe on the PCB is produced by the LIGA process in response to narrower semiconductor pitch length. The problem is that there are no methods to repair a wrong contact probe. Whole of the contact probes should be a waste owing to one wrong contact probe. We propose to replace a wrong contact probe with a good one using our apparatus. Experiments to remove a contact probe by the apparatus is carried out using the specimen of a mimic probe card, where a cantilever type contact probes are arranged with a pitch of 25 micrometers. Removal of the wrong contact probe is carried out by a non-contact discharge and a contact discharge using the apparatus. High voltage of about 1-2kV is applied after the work probe is moved to above the target contact probe for the non-contact discharge. While high voltage of about10kV is applied after the work probe is positioned in contact with the target contact probe for the contact discharge. The target contact probe is removed by both methods, though the neighboring contact probes are damaged. The latter method is hopeful for removal for repair of the probe card.
We aim to fabricate microstructure and microdevices by integrating and arranging powder particles, i.e., the particle assemblage. We have developed three assembling techniques of the particles. The details of the assembling techniques and samples of the assembled microstructures are introduced. A manipulator is developed to manipulate and to weld metal particles by using a tungsten probe. Nickel alloy particles of 50 micrometers were piled on a gold substrate by the manipulator, and a leaning tower of the particles is fabricated. The array of the leaning tower is considered to act as an actuator. For the integration of a great number of particles, we developed another method based on the principle with the xerography. An electron beam or an ion beam is irradiated on an insulating substrate. An electrified pattern is formed on the substrate by the doped electron or doped ion. Fine particles are attracted to the pattern by the electrostatic force. Thus, we can arrange particles by immersing the substrate in the suspension of particles. The third is a productive method of ordered mixture by the electrostatic force. A self- thermostatic heater is made from the composite particles of BaTiO3 and In produced by the method.
Probe manipulation of fine particles has been investigated in our laboratory. The feature of our system is that wide range of voltage, 0-10kV, can be applied between the probe and the substrate. In this method, we can pick up a fine particle at the tip of the probe, carry, place and weld the particle at a predetermined point on the substrate by controlling the applied voltage to the probe. When the particle is picked up, 10-50V is applied. And 2-10kV is applied for the welding. Breaking shear stress of welded particles is measured as follows. A sheet spring, where the strain gauges are stuck, is prepared. One end of the sheet spring is held, and moved to push off the welded particle by the free end. The shear stress is calculated from the output of the strain gauges. The breaking shear stress is 44-71MPa for gold particles welded on a gold substrate. Self- sustaining characters, 'NRIM', are formed from gold particles of 40micrometers as an example of microstructure. Preliminary experiments for the application to the ball grid array are carried out. We also fabricated a slant tower of magnetostrictive particles. It will be used as a micro- actuator in the alternative magnetic field.
In the previous paper, preliminary research results on powder particle assemblage technique using a microprobe was reported. It was shown that the technique makes it possible to manipulate powder particles one by one, etch microscopically and weld the powder particle into a substrate or other powder particles. In this work, the welding mechanism of this method and metallurgical properties of welded parts were investigated, and micro- actuators were fabricated by means of powder particle assemblage technique using the microprobe. The results indicated the potentiality of this technique for application to assemblage of micro-machine and micro-devices.
Using a tungsten micro-probe with a tip of 2 micrometers radius, fine metallic powder particles could be manipulated one by one. By applying low voltage (about 10 V) between the probe and a metallic substrate, the powder particle on the substrate was adsorbed to the tip of probe easily, and by cutting off the voltage the powder particle was desorbed from the tip. Therefore it is possible to arrange powder particles as designed by controlling the voltage and movement of the probe. In addition to the powder particle manipulation, powder particles welding was studied. The tungsten micro-probe was contacted with the powder particle on the metallic substrate, and high voltage (about 10 kV) was applied between the probe and the substrate. It was observed that the glow discharge was caused between the powder particle and the substrate. The contacting parts of the powder particle and the substrate were melted and welded each other. By the manipulation and the welding, micro-structures composed of fine powder particles (about 60 micrometers ) were constructed. Powder particle towers and a micro- actuator were fabricated by way of trial. The results demonstrated the potential of the micro- probe assembly for the fabrication of electronic devices, micromachines and intelligent materials.