Purpose




The purpose of this paper is to investigate the temperature reliability for a parallel high-efficiency class-E power amplifier (PA).




Design/methodology/approach




To explore the relationship between temperature and direct current (DC) characteristics, output power, S parameters and efficiency of the PA quantitatively, a series of reliability experiments have been designed and conducted to study the temperature reliability for this PA.




Findings




From the results, the prominent performance degradation even failure is found during the testing. Furthermore, the thermal shock test can cause permanent failure, which is a great threat for PA.




Research limitations/implications




Therefore, to ensure the good performance, the influence of temperature on PA reliability should be carefully considered during the stage of PA design.




Practical implications




All these can provide important guidance for the reliability design of PA.




Social implications




All these can give some important guidance for PA application.




Originality/value




In addition, PA is usually designed according to the electrical properties at the room temperature. From the results above, it can be concluded that it may be unable to satisfy the performance requirement at high temperature. In turn, if it is designed according to the electrical properties at low temperature, the transistor often works in the super-saturated state, the reliability of PA will become the new problem. Therefore, to ensure the good performance, the influence of temperature on PA reliability should be carefully considered during the design.

Study of temperature reliability for a parallel high-efficiency class-E power amplifier

The objective of this paper is to provide a systematic investigation to orthogonal experiment design of backplane. The thermoelectricity reliability is systematically investigated by using mixed orthogonal array L9 (3, 4) based on orthogonal experimental design. The experiment results show that the wire width and wire pitch have a significant impact on the thermoelectricity reliability of the backplane, while the wire thickness has an unobtrusive effect. A finite element model of backplane is established based on a sample structure. The results show that the maximum stress occurred in the copper wire, which connected with FR-4 and the polyimide.

Approach on thermoelectricity reliability of board-level backplane based on the orthogonal experiment design

Purpose



– The purpose of this paper is to form copper coin-embedded printed circuit board (PCB) for high heat dissipation. 




Design/methodology/approach



– Manufacturing optimization of copper coin-embedded PCB involved in the design and treatment of copper coin, resin flush removal and flatness control. Thermal simulation was used to investigate the effect of copper coin on heat dissipation of PCB products. Lead-free reflow soldering and thrust tests were used to characterize the reliable performance of copper coin-embedded PCB. 




Findings



– The copper coin-embedded PCB had good agreement with resin flush removal and flatness control. Thermal simulation results indicated that copper coin could significantly enhance the heat-dissipation rate by means of a direct contact with the high-power integrated circuit chip. The copper coin-embedded PCB exhibited a reliable structure capable of withstanding high-temperature reflow soldering and high thrust testing. 




Originality/value



– The use of a copper coin-embedded PCB could lead to higher heat dissipation for the stable performance of high-power electronic components. The copper coin-embedded method could have important potential for improving the design for heat dissipation in the PCB industry.

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Copper coin-embedded printed circuit board for heat dissipation: manufacture, thermal simulation and reliability

This paper presents a new method, based on slotting and folding of rigid printed circuit board (PCB), for creation of 3-D cuboid system in package (SIP) devices. The method, which can create folds at any angle and uses standard manufacturing and design processes and commercial off-the-shelf components, is suitable for making SIPs down to at least 1 cm3 in volume. It offers significant advantages over current approaches to 3-D SIP fabrication, particularly in terms of simplified manufacturing and increased packing density, as it eliminates the need for connectors or flex tapes to form folds. The method involves removing substrate material, using a dicing saw to cut a slot at the area where the fold is to be formed, and then applying heat to the area and forming the fold. Once cooled the fold remains rigid and the electrical tracks remain intact. The optimum parameters for creating a 90° fold in a PCB using this method were identified in a designed experiment with variables including substrate material, temperature, cut depth, and conductor width. Having identified the optimum process parameters, 25-mm × 10-mm × 10-mm × 10-mm cuboid test modules were fabricated and reliability screening involving temperature storage, temperature cycling, temperature-humidity, and shock/vibration was carried out. All of the modules passed reliability screening test. Finally, a functional system-in-cube module was fabricated using the folding method. The module, which combines environmental stress sensors and a microcontroller in a 1 cm3 package, was intended for deployment as a prognostic reliability monitor. The monitor was evaluated over a range of temperature and humidity and underwent shock/vibration testing without failure. This is believed to be the first time that a board-folding approach has been used to fabricate 3-D SIP modules.

Board-Folding Method for Fabrication of 3-D System in Package Devices

This paper aims to study the effect of the thermoforming process on the assembly of a newly developed stretchable material for electric circuit and LEDs for manufacturing of automotive lighting. The thermoforming process was conducted using a mould developed based on commercially available automotive lighting product. The circuit was initially printed on a flat thermoplastic substrate using screen printing technique prior to the thermoforming process. The quality of the product was investigated before and after thermoforming process through quantitative measurement and visual inspection in terms of the circuit’s resistivity and the electrical conductivity, respectively. The resistivity measurement was conducted by using four point probes instrument to compare the resistivity of the circuit which depends on stretch level of circuit and substrate during the thermoforming process. The stretch level was found to be different along the geometry due to the unsymmetrical geometry of the mould. The electrical conductivity of the circuit was also tested by LEDs illumination through power supply connection. This study shows promising results in applying thermoforming process in the fabrication of 3-dimensional shape product with lower cost equipment.This paper aims to study the effect of the thermoforming process on the assembly of a newly developed stretchable material for electric circuit and LEDs for manufacturing of automotive lighting. The thermoforming process was conducted using a mould developed based on commercially available automotive lighting product. The circuit was initially printed on a flat thermoplastic substrate using screen printing technique prior to the thermoforming process. The quality of the product was investigated before and after thermoforming process through quantitative measurement and visual inspection in terms of the circuit’s resistivity and the electrical conductivity, respectively. The resistivity measurement was conducted by using four point probes instrument to compare the resistivity of the circuit which depends on stretch level of circuit and substrate during the thermoforming process. The stretch level was found to be different along the geometry due to the unsymmetrical geometry of the mould. The electrical con...

/pdf/a-study-on-thermoforming-process-of-stretchable-circuit-and-xtf42r5gli.pdf

A study on thermoforming process of stretchable circuit and its performance in manufacturing of automotive lighting

Purpose – Seeks to answer the question: have the reasons for using flex‐rigid circuit boards changed through the years?Design/methodology/approach – The paper presents the development of flex‐rigid circuit board construction techniques from the first applications to the current status of a modern interconnection system. The paper discusses that it was the military and avionic industry that in the past required an interconnection technique that was reliable under environmental stress but compact and lightweight. Today it is the automotive and communication industry that is driving the development of printed circuit board technology.Findings – Finds that wiring and interconnection must be cheap, reliable, light in weight, and must fit into very small housings. The demand for complex interconnection solutions like the flex‐rigid circuit technique is rising with the increased level of integration of more functions into electronic devices. The reasons for using flex‐rigid circuitries are nearly still the same ...

Evolution of a wiring concept – 30 years of flex‐rigid circuit board production

Purpose – The purpose of this paper is to present methods for dissipating heat from RF circuit boards.Design/methodology/approach – The paper describes various models developed by RUWEL in this respect.Findings – The integration of heat removal systems in the structure of printed circuit boards is a proven and reliable technique, and ideally suitable for RF circuit boards.Originality/value – In addition to using conductive adhesive films to bond RF circuit boards to heat sinks, new methods have been developed to integrate local heat removal systems in the form of Cu coins. These techniques give the circuit designer flexibility in terms of board design and choice of materials. The models presented are already being used for various RF components in base stations for cellular telephone networks and WiMax services.

Markus Wille

Papers

Evolution of a wiring concept – 30 years of flex‐rigid circuit board production

Methods for dissipating heat from RF circuit boards