The requirement to make low profile ohmic contacts to a piezo-resistive MEMS pressure sensor has highlighted
limitations of ultrasonic wire bonding technology. Wire bonding typically uses 25-50 μm diameter gold or aluminium
wire and ultrasonic welding to the contact pads of micro-electronic devices results in a contact wire proud of the pad
surface. If the application involves the MEMS pressure sensor and contacts being encapsulated, then repetitive changes
in pressure flexing the contact wires can lead to fracture.
A possible solution is to scale down laser welding technology to fuse materials at the micron scale. For this purpose a
precision ophthalmic surgical laser system has been modified to investigate optimum conditions for laser welding, both
at the micron scale and for the typical geometries involved. Typical requirements involve a cylindrical contact wire to
be bonded to a thin contact pad on the MEMS device. Since the pad size is of similar dimension to the wire, and the
requirement for a low profile stable configuration, a keyhole welding strategy is required.
The Nd:YAG based ophthalmic laser has been modified, the Q-switch removed and the output pulse width and energy
controlled principally via control of the flashlamp.
Although coordinate metrology has reached a very high state of development concerning versatility and accuracy for
common engineering parts, a high precision capability with nano scale resolution and accuracy is often hard to achieve
when it is required to measure very small parts and features. The limiting component is the bulky probing system of
traditional coordinate measuring machines (CMMs). In order to satisfy increasing demand for highly accurate
geometrical measurements on small parts and small structures, a new measuring probe of high sensitivity and small
geometrical dimension with low contact forces needs to be developed. In this paper, a probing system, which combines a
Fibre Bragg grating (FBG) embedded optical fibre tactile probe with an optical sensing technique, has been used. A
novel simple wavelength shift demodulation system is tested which incorporates using the single mode light launched
from a laser diode (LD) forming an external cavity between the LD and the FBG sensor to detect the Bragg wavelength
shift induced by the strain on the FBG sensor. This demodulation method can be used to detect the strain-induced
wavelength shift of the FBG. A strain resolution of 0.6 με is achieved. With the sensor elements integrated into the probe
tip directly, the system sensitivity can be increased significantly.
With the reduction in dimensions of products in the last decade, the need for highly accurate dimensional inspection and measurement increases, which requires down scaled measuring tools. The key element for a powerful down scaled dimensional measuring tool coordinate measuring machine is the downscaled probe. In order to satisfy the ongoing increasing demand for highly accurate geometrical measurements on small parts and small structures, a new measuring probe having high sensitivity and small geometrical dimension with low contact forces needs to be developed. In this paper, a novel probing system, which combines a FBG (Fibre Bragg Grating) embedded optical fibre tactile probe with an optical sensing technique, is proposed for down scaled 3D micro-CMMs. The Bragg wavelength shifts with the strain developed along the fibre once the fibre touches the surface of the part. With high-resolution interferometric wavelength demodulation technology, a resolution of 5nm could be achieved by the FBG integrated system. With the sensor elements integrated into the probe tip directly, the system sensitivity can be increased significantly for 3 dimensional measurements.
In the last decade the general miniaturisation of complex products has lead to an increased importance of high precision machining and assembly. Together with increasing precision of products, the need for highly accurate dimensional inspection increases. CMMs (Coordinate Measuring Machines), as a versatile and widespread dimensional metrology tool, can efficiently perform complex measurement with a resolution of about 0.1μm and a repeatability of about 0.3μm. The existing probes for CMMs tend to be very bulky and result in high probing forces for geometrical measurements of high accuracy on small parts. In this paper, an economical flexible method, which is based on optical fibre splicer, is proposed to fabricate an integrated micro scale silicon probe with spherical tip for micron CMMs. Based on Taguchi method, a combination of optimised process parameters has been obtained to control the fabrication conditions that will ensure the manufacturing of tips of a high and consistent quality. With proper control of the process parameters, an optic fibre probe tip with the diameter dimension in the range of 200 to 400μm is achieved and there is a great potential to fabricate a smaller tip with a diameter of 50-100μm in the future.
Lumogen Yellow S0790 is a commercial azomethine based pigment and is used for enhancing CCD devices for detecting ultraviolet radiation. In this work we report on the crystal structure and morphology of the raw material, as-deposited and post-annealed films, as well as the influence these have on the subsequent optical properties. Our measurements of physical vapour deposited (PVD) Lumogen films indicate that commercial Lumogen powder is crystalline in its as-received state, with a melting point of 273.3°C and boiling point of 328.6°C. Furthermore, we have found that as-deposited films on room temperature substrates possess an inherent crystalline structure, which has not been reported previously, but also that the material’s structure changes into a completely different crystalline form upon annealing for 90 hours at 80°C.