An assessment of the applicability of embedded resistor trimming and rework (original) (raw)
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In this work environmental behavior of resistors embedded into Printed Circuit Boards (PCBs) and discrete chip resistors assembled to standard PCBs are co mpared. The investigations were based on the thin-film resistors made of NiP alloy, thick-film resistors made of carbon or carbon-silver inks as well as chip resistors in 0402 and 0603 packages. Thin-and thickfilm resistors were made in the bar form. In addition, poly mer thick-film resistive films were screen-printed on the several types finishing materials of contact terminations such as copper, silver, and gold. To determine the sensitivity of embedded resistors versus s tandard assembled chip resistors on environmental exposure the climatic chamber was used. The measurements of resistance were carried out periodically during the tests, and after the exposure cycles.
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IEEE Transactions on Advanced Packaging, 2005
Embedding passive components (capacitors, resistors, and inductors) within printed wiring boards (PWBs) is one of a series of technology advances enabling performance increases, size and weight reductions, and potentially economic advantages in electronic systems. This paper explores the reliability testing and subsequent failure analysis for laser-trimmed Gould subtractive nickel chromium and MacDermid additive nickel phosphorous embedded resistor technologies within a PWB. Laser-trimmed resistors that have been "reworked" using an inkjet printing process to add material to their surface to reduce resistance have also been considered. Environmental qualification testing performed included: thermal characterization, stabilization bake, temperature cycling, thermal shock and temperature/humidity aging. In addition, a pre/post-lamination analysis was performed to determine the effects of the board manufacturing process on the embedded resistors. A failure analysis consisting of optical inspection, scanning acoustic microscope (SAM) and environmental scanning electron microscope (ESEM) imaging, and PWB cross-sectioning was employed to determine failure mechanisms. All the embedded resistors were trimmed and the test samples included resistors fabricated both parallel and perpendicular to the weave of the board dielectric material. Material stability assessment and a comparison with discrete resistor technologies was performed.
Stability of thin-film resistors embedded in printed circuit boards
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Long-term stability of embedded passives is very important issue. To determine this matter an aging process can be used, where test samples are exposed to environmental conditions. Objecti ve of this research was analyzing reliability of thin-fil m resistors based on Ohmega-Ply® technol ogy. Resistive material was a nickelphosphorus (Ni-P) alloy (wi th sheet resistance 25 Ω/sq or 100 Ω/sq) on FR-4 substrate. A number of vari ables were considered in this study (sheet resistance, geometry of resistor, type of cl adding, l aser trimming, pulse stress and environmental conditi ons). Two di fferent accelerated ageing processes-Ex-Situ (samples exposed to elevated temperature and/or rel ati ve humi di ty but resistance measurements made at room temperature) and In-Situ (resistance of test samples performed directly at the ageing condi tions) were carried out to perform long-term behavior analysis. The results revealed a significant influence of thickness of resistor, type of cladding and temperature on stability of investigated structures. Signification of other factors was negligible.
Selected properties of multi-terminal resistors embedded in printed circuit boards
Electron Technology Conference 2013, 2013
Modern electronic devices are more and more complex and multifunctional. It could be done by producing faster and more reliable active components and increasing number of passives and interconnections' density. To form such complex devices one can embed components in substrate of printed circuit board (PCB) or build multilayer boards. The other way is to form multi-terminal passive components to spare free surface and decrease number of interconnections. Authors created three-terminal thin-film (TF) resistors embedded in PCBs and investigated their selected properties such as resistance repeatability, long term stability, pulse durability and thermal characteristics.
Thermal effects in embedded thin- and thick-film resistors in comparison to chip resistors
Circuit World, 2014
In this work environmental behavior of resistors embedded into Printed Circuit Boards (PCBs) and discrete chip resistors assembled to standard PCBs are co mpared. The investigations were based on the thin-film resistors made of NiP alloy, thick-film resistors made of carbon or carbon-silver inks as well as chip resistors in 0402 and 0603 packages. Thin-and thickfilm resistors were made in the bar form. In addition, poly mer thick-film resistive films were screen-printed on the several types finishing materials of contact terminations such as copper, silver, and gold. To determine the sensitivity of embedded resistors versus s tandard assembled chip resistors on environmental exposure the climatic chamber was used. The measurements of resistance were carried out periodically during the tests, and after the exposure cycles.
Trimming and stability of thick-film resistors with reduced dimensions
2001
The increase of packaging density in electronic modules demands miniaturisation of passive components. This is related also to thick-film resistors, which are non-equilibrium heterogeneous systems. The as-fired resistors have the resistance tolerance within 20% range. Therefore they have to be trimmed in majority of thick-film hybrid circuits. The most appropriate trimming method is looked for thick-film microresistors at this very moment. This paper presents long-term stability of laser or high-voltage pulse trimmed cermet thick-film microresistors made on alumina substrate using 100 /sq. or 10 k /sq. inks from Du Pont or Institute of Electronic Materials Technology, Warsaw. The as-fired and laser (increase of resistance by about 30-40%) or pulse voltage trimmed (resistance increase by about 10%) resistors were thermally aged for 500 h at 180 o C or 100 h at 300 o C. There are no significant differences in long-term stability between as-fired, laser trimmed and high voltage pulsed components. The level of fractional resistance changes is dependent mainly on kind of resistive inks. In general Du Pont resistors prevail IEMT ones. Resistors aged at 180 o C exhibit slight resistance increase versus ageing time whereas the resistance of those aged at 300 o C is decreased.
Microelectronics Reliability, 2012
Embedding passive components into multilayer printed wiring boards (PWBs) meet electronic device requirements concerning the necessity of saving the surface board area for active elements, reducing board's size, improving device functionality and safety as well as overall product cost reduction. Since embedded components cannot be replaced after the board is completed, a long term stability and reliability are the important concerns for manufactures. This paper presents the results of examinations of embedded thin-film NiP resistors and polymer thickfilm resistors during their continuous operation and the influence of temperature on the resistance values after the simulation of a lead-free soldering process and after the temperature cycling test (À40 C/+85 C).
Microelectronics Reliability, 2005
In this paper a new approach to laser trimming is investigated and compared with traditional trimming. It relies on creating an additional contact for lowering resistance values thus simplifying the design and widening resistance trimming ranges. This enables to achieve a correction with shorter cut length of, so it can lead to a faster and cheaper fabrication process of hybrid integrated circuit. This paper analyses trimming range and trimming characteristics computed for different shapes of added contact using a new, very fast and easily programmable method. Moreover the experimental verification of such approach is presented. The relative trimming range and sensitivity are analyzed as a function of additional contact shape and cut length. Next long-term stability, pulse durability and low frequency noise are compared for two-and three-contact resistors versus trim pathway length.
Structure and properties of resistors and capacitors embedded into printed circuit board
The integration of electronic components with Printed Circuit Board (PCB) is now one of the main directions of electronic technology development. Until now many materials that can be used for embedded passives were created. But this technology is used mostly in military applications as well as in aviation and space electronics. Due to the growing number of passives that are now statistically required for proper operation of single integrated circuit, passive components become quickly a serious obstacle in miniaturization of electronic circuits and systems. Embedding of passive components into Printed Circuit Board allows further miniaturization and can lead to cost reduction. M oreover embedded passives are characterized by smaller parasitic effects. In this paper the results of material and electrical investigations of thin-and polymer thick-film resistors and planar capacitors embedded into PCBs are presented. The roughness investigations of laminates and each layer of the structure and the phase structure of used dielectric, resistive and conductive films are discussed. The cross-sections of the embedded structure obtained by scanning electron and optical microscopy are shown and discussed. The functional models contained embedded components and preliminary research of multicontact resistors is presented.