Technical Library | 2022-04-28 06:42:19.0
I. Chip capacitors(MLCC) The full name of chip capacitors: multilayer (multilayer, laminated) chip ceramic capacitors, also known as chip capacitors, chip capacitance.
Technical Library | 2013-03-28 16:18:22.0
For the last couple of years, the main concerns regarding the electrical performance of blank PCB boards were impedance and ohmic resistance. Just recently, the need to reduce insertion loss came up in discussions with blank board customers (...) The paper describes the test vehicle and the testing methodology and discusses in detail the electrical performance characteristics. The influence of the independent variables on the performance characteristics is presented. Finally the thermal reliability of the boards built applying different copper foils and oxide replacements was investigated.
Technical Library | 2015-08-18 17:48:53.0
Why Selectively Conformal Coat the Electronic Assembly? Printed circuit boards (PCBs) are employed in a variety of products and devices, and this means that it might be necessary for your PCBs to be moisture resistant. It is important to choose the right type of conformal coating so you need not worry about the durability of your product. Fortunately, there are several options available that can help, and you can even use selective conformal coating robots to provide proper application of the coating.
Technical Library | 2022-01-26 15:26:56.0
In this work an attempt is made to improve the fracture toughness and electrical conductivity of epoxy/glass fiber based laminates by the inclusion of carbon nanotube (CNT) fillers. The fiber orientation of the epoxy/ glass fiber (GF) fabric laminates was optimized based on estimation of mechanical properties. The carboxylic acid functionalized CNTs were incorporated into epoxy matrix by ultra-sonication method. The nano filled epoxy resin was used to prepare laminates with 30/45 GF fabric orientation. The CNT content was varied and its effect on the tensile properties was determined. The fracture toughness of multiphase composites was estimated using single edge notch bend (SENB) test. The presence of CNTs improved the fracture toughness by a crack bridging mechanism. The volume resistivity of multiphase composites was found to be superior to the conventional epoxy/CNT composite. The presence of glass fabric reduces the number of inter-tube contacts contributing to the reduction in volume resistivity.
Technical Library | 2023-03-13 19:27:13.0
10%) and mean strains (>30%). A trace width effect is found for the fatigue behavior of 1 mm vs 2 mm wide specimens. The input specimen-characteristic curves are trace-width dependent, and the model predicts a decrease in Nf by a factor of up to 2 for the narrower trace width, in agreement with the experimental results. Two different methods are investigated to generate the rate of normalized resistance increase curves: uninterrupted fatigue tests (requiring ∼6–7 cyclic tests), and a single interrupted cyclic test (requiring only one specimen tested at progressively higher strain amplitude values). The results suggest that the initial decrease in normalized resistance rate only occurs for specimens with no prior loading. The minimum-rate curve is therefore recommended for more accurate fatigue estimates.
Technical Library | 2018-07-11 22:46:13.0
For a demanding automotive electronics assembly, a highly thermal fatigue resistant solder alloy is required, which makes the lead-free Sn-Ag-Cu type solder alloy unusable. Sn-Ag-Bi-In solder alloy is considered as a high reliability solder alloy due to significant improvement in thermal fatigue resistance as compared to a standard Sn-Ag-Cu alloy. The alloy has not only good thermal fatigue properties but it also has superior ductility and tensile strength by appropriate addition of In; however, initial results indicated a sub-par performance in joint reliability when it is soldered on a printed circuit board (PCB) with Electroless Nickel Immersion Gold (ENIG) surface finish. Numerous experiments were performed to find out appropriate alloying element which would help improve the performance on ENIG PCBs. Sn-Ag-Bi-In solder alloys with and without Cu additions were prepared and then tests were carried out to see the performance in a thermal fatigue test and a drop resistance test.to investigate the impact of Cu addition towards the improvement of joint reliability on ENIG finish PCB. Also, the mechanism of such improvement is documented.
Technical Library | 2015-05-21 18:46:31.0
In this work the reliability of an embedded planar capacitor laminate under temperature and voltage stress is investigated. The capacitor laminate consisted of an epoxy-BaTiO3 composite sandwiched between two layers of copper. The test vehicle with the embedded capacitors was subjected to a temperature of 125oC and a voltage bias of 200 V for 1000 hours. Capacitance, dissipation factor, and insulation resistance were monitored in-situ. Failed capacitors exhibited a sharp drop in insulation resistance, indicating avalanche breakdown. The decrease in the capacitance after 1000 hours was no more than 8% for any of the devices monitored. The decrease in the capacitance was attributed to delamination in the embedded capacitor laminate and an increase in the spacing between the copper layers.
Technical Library | 2015-07-14 21:32:04.0
The PCB industry is ever changing and adapting to new technologies. OEM specifications and requirements have also advanced due to these technologies. In some cases the OEMs are asking for a low resistance test to be performed on some or all electrical test nets of the PCB or on the holes of the PCB. This requirement is typically not well defined on the fabrication drawing and that leads to misleading conclusions by the fabrication house (...) This paper will use the data gathered by the company’s operations to outline what a 4-wire Kelvin test is and how it can be used. Several examples will be illustrated of what the 4 wire Kelvin test can and cannot do. A clear definition of what limitations are present during the testing operation will be defined. The paper will assist designers in understanding how the low resistance test can assist them and also identify causes that can identify unwanted concerns/issues.
Technical Library | 2015-08-13 15:52:40.0
Pad cratering has become more prevalent with the switch to lead free solders and lead free compatible laminates. This mainly is due to the use of higher reflow temperature, stiffer Pb-free solder alloys, and the more brittle Pb-free compatible laminates. However, pad cratering is difficult to detect by monitoring electric resistance since pad cratering initiates before an electrical failure occurs. Several methods have been developed to evaluate laminate materials' resistance to pad cratering. Pad-solder level tests include ball shear, ball pull and pin pull. The detailed methods for ball shear, ball pull, and pin pull testing are documented in an industry standard IPC-9708. Bansal, et al. proposed to use acoustic emission (AE) sensors to detect pad cratering during four-point bend test. Currently there is an industry-working group working on test guidelines for acoustic emission measurement during mechanical testing.
Technical Library | 2021-07-27 14:59:56.0
With increasing focus on reliability and miniaturized designs, Conductive Anodic Filament (CAF) as failure mechanism is gaining a lot of attention. Smaller geometries make the printed circuit board (PCB) susceptible to conductive anodic filament growth. Isola has carried out work to characterize the CAF susceptibility of various resin systems under different process and design conditions. Tests were carried out to determine the effect of various factors such as resin systems, glass finishes, voltage bias and hole and line spacings on the CAF resistance. This work was intended to provide information to the user on the suitability of various grades for specific end use applications. The focus of the work at Isola is to find the right combination of process and design conditions for improved CAF resistant products.
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