Search results

The application of laser technology has recently become economically viable for microelectronics and surface mount technology. Semiconductor laser technology may prove to be the only technology capable of solving the assembly problems that will accompany further advances in microelectronics. Some characteristics of Nd‐YAG and CO2 lasers are compared with the performance of semiconductor diode lasers for soldering purposes. The early stages of evaluation of semiconductor diode lasers in an experimental soldering station at the University of Hull suggest that these lasers serve as an efficient selective, controllable and compact high power density heating source capable of meeting present and future microelectronics soldering requirements.

To design a flexible integrated robotic assembly and rework (remanufacturing) cell for assembly, selective assembly and rework of advanced surface mount components (SMCs) using the generic methodology developed in this paper.

Manual rework procedures are investigated for all advanced SMCs. General and specific component‐related rework considerations are obtained and necessary tooling candidates for automation are determined. This is followed by determination of the specific automated rework procedure and selection of suitable tooling for automated robotic rework and generation and evaluation of design concepts.

The developed methodology, which considers the reflow tool at the centre of the development process, has worked well in designing a flexible integrated robotic assembly and rework cell.

This study identified the rework requirements for advanced SMCs, the essential features for rework reflow tools, criteria for comparing reflow tools, and a generic procedure for design and concept selection.

It provides valuable knowledge for designers of flexible integrated robotic assembly and rework cells for assembly, selective assembly and rework of advanced SMCs.

The latest developments in the use of lasers for welding plastics are reviewed. Lasers were demonstrated as being suitable for welding plastics in 1970. However, it is only now that they are finding wide application following technical developments in transmission laser welding and ClearWeld™, and the availability of small, economic diode laser systems.

Trials using high powered laser arrays recently available, have shown that a range of joining and surface treatment processes are possible. These range from transmission welding of polymeric materials to surface hardening, soldering and welding of steels.

High‐powered diode lasers are becoming increasingly used in manufacturing for transmission welding of thermoplastic materials. This process can replace many of the traditional techniques such as ultrasonic welding. Benefits include being a non‐contact process that can encapsulate sensitive electronic housings without damage. This is described in an electronic throttle assembly case study.

This paper aims to improve the device performance from the perspective of reducing ohmic contact resistance; the effects of different electrode structures and alloying parameters on the series resistance and power-current-voltage of laser diodes (LDs) have been investigated in this paper.

Four groups of p-GaAs side metal electrodes with different metal layer arrangements and thicknesses are fabricated for the investigated LDs. The investigated p-GaAs side electrodes are based on Ti/Pt/Au material and the n-GaAs side metal electrodes all have a same structure of Ni/Ge/Ni/Au/Ti/Pt/Au. The LDs with different electrodes were alloyed at 380°C for 60 s and 420°C for 80 s.

The experimental results show that the series resistance decreases by 14%–20%, the output power increases by 2%–2.2% and the conversion efficiency increases by 1.69%–2.16% for the LDs prepared with optimized alloying parameters (420°C for 80 s). The laser diode with p-GaAs side Ti/Pt/Au electrode of 30/70/100 nm has the best device characteristics under both annealing conditions.

The utilization of this improvement on ohmic contact property in electrode is not only very important for upgrading high-power LDs but also helpful for GaAs-based microelectronic devices such as HBT and monolithic microwave integrated circuit.

The aim of the research was to evaluate the concept that utilizes structured planar substrates based on low temperature co‐fired ceramics (LTCC) as a precision platform for the passive alignment of a multimode fiber and wide‐stripe diode laser.

Presents the manufacturing process for realisation of 3D precision structures, heat dissipation structures and a cooling channel into the LTCC substrate. The developed methodology for 3D modelling and simulation of the system was used to optimize structures, materials and components in order to achieve optimal performance for the final product and still maintain reasonably low fabrication costs. The simulated optical coupling efficiency and alignment tolerances were verified by prototype realization and characterization.

The achieved passive alignment accuracy allows high coupling efficiency realisations of multimode fiber pigtailed laser modules and is suitable for mass production.

Provides guidance in the design of LTCC precision platforms for passive alignment and presents a hybrid simulation method for photonics module concept analysis.

The three‐dimensional shape of the laminated and fired ceramic substrate provides the necessary alignment structures including holes, grooves and cavities for the laser to fiber coupling. Thick‐film printing and via punching can be incorporated in order to integrate electronic assemblies directly into the opto‐mechanical platform.

Introduces the LTCC 3D precision structures for photonics modules enabling passive alignment of multimode fiber pigtailed laser with high efficiency optical coupling. Demonstrates the hybrid simulation methodology for concept analysis.

Studies the effects of exposure to light of the laser diode Melles Griot (λ = 670nm), He‐Ne laser (λ = 632.8nm) and argon laser (λ = 514nm) on selected soil micro‐organisms, fungi that destroy old manuscripts, pictures, stone, etc. and on humification and mineralization of soil samples. Also studies exposure effects on seed growth and biomass production of a few species of cultivated plants and on Chlorella cells and animal spermatozoa. Finds significant changes in comparison to control material (including results of the preliminary measurement of bio‐photon emission). Suggests a fruitful direction for studies on the synergistic effects of Se, laser and white light, as well as on the optimal level of exposure of living material to laser light. Concludes that the data obtained seem to be useful both for land reclamation and for the protection of the indoor environment against toxicogenic moulds and bacteria.

The advances in miniaturisation and ever increasing complexity of integrated circuits frequently mean an increase in the number of connections to a component with simultaneous reduction in pitch. For these emerging smaller contact geometries, micro‐laser connection technologies are required. The reliability of the connection plays a decisive rôle. The implementation and reproducibility of laser connections technology in micro‐electronics depend on good thermal contact between the two parts and high quality absorption of the material surface used. Laser energy can cause local melting due to overheating of the lead because of the low distance between lead and bump. This effect influences the reproducibility of the contacts. Even the slightest interruption in the thermal contact of the parts can cause non‐reproducibility of the contacts. Materials with a higher quality of absorption, for example Sn(32% ), can be soldered with a good level of reproducibility. This clearly differs from gold (4% ) or copper(7% ) surfaces. Due to the low absorption of these materials it is necessary to use a laser with a higher intensity to produce the same energy. Irregularities in the quality of absorption, laser instability and thermal contact can not guarantee reproducibility of the interconnections with this high laser intensity. The FPC (fibre push connection) system offers several solutions to the problems mentioned. This system enables the laser to be transported by fibre to the contact parts. The end piece of the fibre serves at the same time as a pushing unit. The advantage of this system is that the attenuation heat of the fibre end surface is also available for the connection. This improves the use of laser energy. As part of the laser energy at the end surface of the fibre is transformed into thermal energy, independently of the absorption quality of the material used, connection of a gold‐plated contact part is possible. By pressing the connecting parts with the tip of the fibre, optimal coupling is achieved. The reproducibility of different metallisations and the reliability of connections with a pitch below 100 μm are presented as well as further applications of this system.

With the ever‐decreasing size of electronic components, examines the use of laser soldering, particularly of fine‐pitch, high value devices. Discusses the advantages and disadvantages of using lasers and the applications to which they are suited. Looks at the different types of lasers and how their different wavelength of operation affects the soldering process. Describes an experimental laser soldering station and its ability to solder circuit boards. Concludes that modern electronic component packaging technology is demanding new techniques for the interconnection of devices, and that the application of lasers to the traditional technique of soldering will enable this tested process to be applicable to the very fine pitch devices now being introduced.