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Journal ArticleDOI

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

01 May 2006-Circuit World (Emerald Group Publishing Limited)-Vol. 32, Iss: 2, pp 12-17
TL;DR: In this article, the development of flex-rigid circuit board construction techniques from the first applications to the current status of a modern interconnection system is discussed, showing that the demand for complex interconnection solutions is rising with the increased level of integration of more functions into electronic devices and that wiring and interconnection must be cheap, reliable, light in weight and must fit into very small housings.
Abstract: 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 ...
Citations
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Journal ArticleDOI
TL;DR: In this paper, the authors provide a systematic investigation to orthogonal experiment design of backplane and investigate the thermoelectricity reliability of the backplane by using mixed orthogonality array L9 (3, 4).
Abstract: 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.

10 citations

Journal ArticleDOI
TL;DR: In this article, the authors presented 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.
Abstract: 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.

5 citations

Proceedings ArticleDOI
04 Dec 2017
TL;DR: In this paper, 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 was investigated through quantitative measurement and visual inspection in terms of the circuit's resistivity and electrical conductivity.
Abstract: 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...

5 citations

Proceedings ArticleDOI
01 Oct 2016
TL;DR: In this article, low resistance was found between the neighboring pins on failure sample which connected with flexible printed board and rigid printed board, but the pins on good sample were insulated with the others.
Abstract: Function failure was found successively in one type of smart remote controls when using a period of time With preliminary investigation by electric circuit, low resistance was found between the neighboring pins on failure sample which connected with flexible printed board and rigid printed board, but the pins on good sample were insulated with the others After peeling off the flexible printed board, black materials which looked like migration were found by stereomicroscope and metallography microscope With the help of scanning electron microscope and energy dispersive spectroscope (SEM&EDS), it was detected that the materials mainly contained the elements of Cu (about 50 at%) and S (about 30 at%), and the two short pins were almost connected with the black materials As a result, the black materials which connected to the two pins should be copper sulfide (CuS) and cuprous sulfide (Cu 2 S) The failure process was as the follows Some active sulfide was on the surface of board, with the bias voltage and moisture, the copper on the pads of board was sulfurized and migrated with electrochemical reaction The migration materials which connected to the neighboring pins cause micro-short circuit However, there was no element of Cu on the clean solder mask, and the element of S could not come from the filling material barium sulfate (BaSO 4 ) because barium sulfate were difficult to break down and the element of Ba had not been detected in the black materials Finally, with further investigation for the manufacturing process of the assembly, the element of S was detected on copper foil after soldering with the solder paste which used in the failure sample, but the element of S could not be detected with the other type of solder paste It could conclude that the active sulfide should come from some sulfur-containing materials in the flux of solder paste breaking down in soldering When soldering, the solvent in the flux was difficult to volatilize due to the flexible printed circuit board (FPC) on the top Some sulfur-containing materials in the solvent would decompose to active sulfide So, in order to avoid the failure of micro-short, the solder paste without sulfur containing should be used in soldering

2 citations

Proceedings ArticleDOI
01 Oct 2012
TL;DR: In this paper, a semi-flex printed circuit board (PCB) was manufactured by using buried material to prevent resin of high-flow prepreg from flowing into the flexible area in lamination process.
Abstract: In this paper, the semi-flex Printed Circuit Board (PCB) was manufactured by using buried material to prevent resin of high-flow prepreg from flowing into the flexible area in lamination process. Windows in which the buried materials were imbedded were shaped in advance in prepreg and cores. The circuit in flexible area was protected by polyimide (PI) cove layer. The preventing capability of resin for the three different buried materials including epoxy resin base material, silicon sheet and Teflon (PTFE) were studied by microsection manufacture and Optical Critical Dimension, and the results showed that the silicon sheet was the most appropriate one. Manufacturing processes such as the heating rate in lamination process, sizes of silicon sheet and windows of prepreg were studied by the orthogonal tests and the optimal manufacturing parameters were analyzed and achieved by Minitab Software. Several demonstration tests were conducted under optimal manufacturing condition and the results including resin length and flexural ability were acceptable. The reliability of semi-flex PCB was evaluated by solder float test, thermal shock test and salt spray test. The results showed that the flexible area had substantially no defects such as bubbles, separation and flaws occurred and delamination had not occurred in the rigid-flex joint of the products, and the resistance value change was 5.37% in thermal shock test. The reliability of semi-flex PCB was acceptable.

2 citations


Additional excerpts

  • ...for installation, rework and maintenance ([1])....

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