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Although the use of ultrasonic agitation on quartz crystal devices during PCB cleaning has long been suspected to be detrimental, little or no data exist to substantiate…
Although the use of ultrasonic agitation on quartz crystal devices during PCB cleaning has long been suspected to be detrimental, little or no data exist to substantiate or quantify the resultant effects. This paper summarises the results of a limited study into these effects for a range of quartz crystal devices, using both CFC and aqueous solvents. The variations with exposure time, and the types and mechanisms of failure are discussed. The results are encouraging and suggest that, although these devices are more susceptible to damage than ICs, once manufacturing defects have been screened out they will withstand ultrasonic exposure without deleterious effects for periods several times longer than those used for cleaning PCBs.
Non‐corrosive rosin fluxes have historically been used for telephone communications assemblies because they provide a measure of reliability even if the flux is not…
Non‐corrosive rosin fluxes have historically been used for telephone communications assemblies because they provide a measure of reliability even if the flux is not totally removed from the assembly. While cleaning is not always necessary from a reliability standpoint, testing issues, product appearance, operating performance and customer requirements must also be considered when making the decision whether or not to clean. As the electronics industry packages more and more functionality on less and less real estate, soldering yields need to increase in order for the assembly process to remain profitable. This requires not only attention to the product's design for manufacturing but it may also require aggressive fluxes to be used in the assembly process. When aggressive fluxes are employed, the necessity for cleaning is greatly increased. The particular combination of flux and cleaning option depends on product design, process capabilities, end point requirements, and environmental considerations. Pending restrictions on the production and use of chlorofluorocarbons (CFCs), and the potential for tighter controls on chlorinated solvents and aqueous detergent effluents, are certain to add to the cost of standard processes. For these reasons alternative cleaning processes have been explored. The evaluation and subsequent use of water soluble flux with ‘water only’ cleaning, terpene cleaning of rosin flux residues, low solids flux ‘no‐clean’ wave soldering and ‘no‐clean’ assembly using reflowed rosin based solder pastes within AT&T are reviewed. A user's assessment of aqueous and semi‐aqueous cleaning is presented which indicates that there are acceptable alternatives to CFCs.
APART FROM ESTIMATES of book losses there appears to be little or no information available on the value of items stolen from libraries. This article is intended to provide an overview of the security problems they face while mentioning some of the devices available to protect individual items or library areas.
The development of the INSPEC vocabulary system which comprises a unified indexing and classification scheme is described together with the reasons for its adoption. The…
The development of the INSPEC vocabulary system which comprises a unified indexing and classification scheme is described together with the reasons for its adoption. The vocabulary system uses a hierarchical classification and a vocabulary development file with thesaurus structure which is linked to the classification. This file has been designed and is used as a controlled‐language thesaurus and as a free‐language aid in the formulation of search profiles.
GaAs electronic devices are becoming increasingly used in the microelectronics industry especially in solid state microwave, ultra high speed digital processing and optoelectronic applications. However, in the manufacture of the GaAs devices, problems due to the inherent brittleness of the GaAs and batch to batch variability of the bond pad metallisation have commonly been experienced. This has resulted in some difficulties in wire bonding to GaAs devices with ultrasonic and thermocompression wire bonding techniques. This paper describes a programme undertaken to investigate Au wire bonding techniques to GaAs devices. Specifically, bonding trials have been performed on a range of GaAs substrates using pulse tip and continuously heated thermocompression bonding and ultrasonic bonding. The results of this work have shown that thermocompression and ultrasonic wire bonding techniques are cabable of producing acceptable bonds to GaAs devices, although some of the advantages and limitations of each technique have been demonstrated. Thermocompression bonding with a continuously heated capillary gave the most tolerant envelope of bonding conditions and highest bond strengths. Pulse tip thermocompression bonding gave a less tolerant envelope of acceptable bonding conditions, required a longer bonding time and the wire was weakened above the ball bond. Ultrasonic bonding did not require any substrate heating to give acceptable bonds. However, the choice of equipment can be critical if damage to the device is to be avoided.
An investigation of the use of ultrasonic agitation for cleaning printed circuit boards using CFC‐based solvents has shown that, under the standard conditions required to…
An investigation of the use of ultrasonic agitation for cleaning printed circuit boards using CFC‐based solvents has shown that, under the standard conditions required to produce clean assemblies, no damage will occur to the components studied. Damage can only be induced by use of anomalously longer times or higher power densities. In all cases in which damage has been induced, it is of a purely mechanical nature due to fatigue, and is located on the device bond‐wires and/or the package legs. Cleaning using CFC‐based solvents under standard ultrasonic conditions of power density and time etc. is readily achieved within 2 minutes, even with a minimum stand‐off height.
The effect of ultrasonic agitation on hybrid devices during PCB cleaning has long been suspected as leading to device malfunction. However, little or no data exist to…
The effect of ultrasonic agitation on hybrid devices during PCB cleaning has long been suspected as leading to device malfunction. However, little or no data exist to substantiate or quantify these effects. This paper describes a limited study into these effects using both test vehicles and commercial products, and discusses their variation with exposure time, the types and mechanisms of failure, and the rle of the hybrid package construction. It is demonstrated that the design of the hybrid package is critical in determining its susceptibility to ultrasonic damage.
The effects of ultrasonic agitation on electronic components during PCB cleaning has long been the subject of controversy. This paper summarises the results of a series of…
The effects of ultrasonic agitation on electronic components during PCB cleaning has long been the subject of controversy. This paper summarises the results of a series of studies into these effects for a range of components using CFC, aqueous and semi‐aqueous cleaning media. The variations with exposure time and power density under various ultrasonic stress conditions (loose, mounted on PCBs, or on purpose‐built test boards) are discussed. The results are encouraging and suggest that there is a large margin of safety when employing currently accepted regimes of operation and good quality components. However, the strong dependence of the damage accumulation on power density emphasises the need to specify and tightly control the power density used.
Purpose – The purpose of this research is to design and build a wild animal pest repellent device with combination of passive infrared (PIR) sensor and ultrasonic signal…
Purpose – The purpose of this research is to design and build a wild animal pest repellent device with combination of passive infrared (PIR) sensor and ultrasonic signal based on microcontroller as system controller. The PIR sensor is used to detect the presence of wild animal objects and ultrasonic signals to interfere with the hearing.
Design/Methodology/Approach – The design of the system is built based on microcontroller as the system controller. The system as a whole includes hardware and software. The design of hardware consists of the system design on the transmitter side and the system design on the receiver side, while the software in the of system are algorithms using C language programming.
Findings – The resulting repellent device can detect animals approaching up to a distance of 5 m and may interfere with its hearing with a 40 kHz ultrasonic frequency up to a distance of 20 m. The system also uses remote monitoring devices using 433 MHz radio frequency up to a distance of 60 m.
Research Limitations/Implications – Each animal has different hearing frequencies, as well as some wild animals, but the hearing frequencies of wild animals are generally at ultrasonic frequencies. The frequency of animal hearing may vary from audio frequency to ultrasonic frequency, so ultrasonic wave emission testing with varying frequencies is required.
Practical Implications – This research combines systems on transmitters and receivers, with real-time monitoring of wild animal positions, and it can be possible to monitor the position of more detailed animals by installing more types of sensors as well as increasing the number of sensors.
Originality/Value – This paper may provide additional insight into the hearing frequencies of animals and may also serve as comparable papers for similar studies.
During the past decades, several researchers have introduced devices that use sonar systems to detect and/or to determine the object location or to measure the distance to…
During the past decades, several researchers have introduced devices that use sonar systems to detect and/or to determine the object location or to measure the distance to an object using reflected sound waves. The purpose of this paper is to use sonar sensor with textile structure and to test it for detection of objects.
In this study, a sonar system based on intelligent textiles approach for detection of objects has been developed. In order to do this, ultrasonic sensor has been integrated to textile structures by using conductive yarns. Furthermore, an electronic circuit has been designed; PIC 16F877 microcontroller unit has been used to convert the measured signal to meaningful data and to assess the data. The algorithm enabling the objects detection has also been developed. Finally, smart textile structure integrated with ultrasonic sensor has been tested for detection of objects.
Beam shape is presented related to identified object and compared with the actual one given in sensor's datasheet in order to test the efficiency of the proposed method of detection. The achieved results showed that the determined beam pattern matches with the actual one given in its datasheet. Therefore, it can be concluded that the integration of sensor was successful.
This is the first time in the literature that a sonar sensor was integrated into textile structure and tested for detection of objects.