Some remarks about relations between processing conditions and microstructural, electrical as well as stability properties of LTCC resistors (original) (raw)
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DC and AC electrical properties and long-term stability of LTCC resistors
There is an interesting problem to become familiar with mutual dependencies between various DC and AC electrical properties as well as with correlation between electrical characteristics and long-term stability of electronic components. This paper presents wide and systematic investigations of electrical and stability properties of buried and surface Low Temperature Co-fired Ceramics (LTCC) resistors. Various resistors were made from commercially available 100 kΩ/sq. resistive ink on/in three different LTCC tapes (from various manufacturers). The influence of resistor/tape combinations (kind of LTCC green tapes, position of resistors) as well as resistor aspect ratio on sheet resistance, temperature dependence of resistance in a wide temperature range, low frequency noise, voltage nonlinearity, AC impedance spectra and long-term stability of thermally aged resistors were measured, analysed and discussed. Many interesting relations were found. For example it was proved, that LTCC resistors (made from the same resistive ink but in different technological variants) with significant dimensional effect were characterised by larger 1/f noise and larger nonlinearity. But dimensional effect did not affect AC properties and long term stability of such resistors.
As-fired thick-film resistors have the resistance tolerance within ±20% and this tolerance is increased for smaller components. Therefore the novel trimming methods are necessary for microresistors, especially when they are embedded in LTCC substrate. This paper compares electrical (normalized temperature dependence of resistance, low frequency noise) and stability properties (relative resistance drift, changes of current noise index) of untrimmed, voltage pulse trimmed and laser trimmed unglazed thick-film resistors after step-increased long-term thermal ageing at 162°C, 207°C and 253°C. Moreover the effect of long term exposure (1000 h, 125°C) and thermal shocks (1000 shocks between À55°C and 125°C) is analysed for untrimmed and voltage pulse trimmed buried LTCC resistors.
Microelectronics Reliability, 2001
This paper presents systematic investigations of electrical and stability properties of various low temperature co-®red ceramics (LTCC) resistors. One of the goals of this work was to check the compatibility of LTCC materials (tapes, resistive and conductive inks) from various manufacturers. Three commercially available green tapes and three LTCC resistor/conductor systems were examined. The resistive inks with 1 kX=sq. nominal sheet resistance were used. Buried (inside) and surface resistors were laminated and ®red according to the tape manufacturersÕ recommendations. The in¯uence of dimensional eect on sheet resistance and hot temperature coecient of resistance, the temperature dependence of resistance in a wide temperature range (from À180°C to 130°C), long-term stability of thermally aged as-®red resistors (150°C, 500 h) and durability to high-voltage micro-or nanosecond pulses (50 ns pulses with 4000 V/mm maximum electric ®eld or 10 ls ones with 700±1000 V/mm electrical ®eld) were carried out for electrical and stability characterisation of LTCC resistors. Non-destructive scanning acoustic microscope diagnostics was applied for structure investigation and estimation of lamination and co®ring process quality of buried LTCC resistors. Ó
LTCC resistors and resistive temperature sensors - chosen electrical and stability properties
28th International Spring Seminar on Electronics Technology: Meeting the Challenges of Electronics Technology Progress, 2005., 2005
This paper presents the correlation between processing conditions and electrical (sheet resistance, resistance vs temperature dependence) and long-term stability (relative changes in resistance (∆R/R 0 ) as well as changes in the temperature coefficient of resistance (∆TCR) or thermistor constant (∆B)) properties of surface and buried LTCC resistors as well as NTC and PTC thermistors. All analyzed components (made from 100 ohm/sq. resistor ink and 1 kohm/sq. PTC or NTC thermistor inks) were fired at standard firing profile (850 o C/15 min, 875 o C/15 min) or overfired (950 o C/15 min, 950 o C/180 min).
2009 32nd International Spring Seminar on Electronics Technology, 2009
The series of lead-free thick film resistors were elaborated by Institute of Electronic Materials Technology (ITME) in Warsaw. The paper presents investigations oftwo pastes: R-100 with resistivity 100 Q/a and R-l OOk with resistivity 100 kQ/a. The pastes were screen printed on alumina substrate with AgPd lead-free terminations. Then fired at several temperatures in the range 750-950°C for 10 minutes and 6 hours at highest temperature. Sheet resistivity and thermal coefficient of resistance (TCR) were measured. X-Ray diffractogramms were taken. The conductive phase that was RuG 2 maintained initial crystal structure regardless firing conditions. No devitrification was observed in lead-free resistors glasses. The lattice constants ofRuG 2 were uniform at temperatures over 800°C. The resistors matched the desired resistivity and the TCR was least temperature dependent at the firing temperatures around 850°C.
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This work presents the results of the thermal analysis of cermet resistors made on alu mina or LTCC substrate and polymer thick-film resistors embedded in FR-4 substrate. The research was carried out with an addit ional consideration of such factors as sheet resistance (which depended on the type of resistive paste), the size and topology of element and the kind of contact material (Cu, Ag or Ni/Au). A few key points on the element were specified fo r wh ich a mo re thorough analysis were carried out. The results were approximated by physically acceptable function which allowed to determine the influence of different mechanis ms of heat transfer, and determine their t ime and thermal constants .
Electrical properties of thin-film resistors in a wide temperature range
Circuit World, 2015
Purpose -The purpose of this paper is to characterise electrical properties of Ni-P thin-film resistors made on FR-4 laminate in a wide range of temperature (fro m -180 to 20ºC). Design/methodolog y/approach -The study was performed using resistors made of nickel-phosphorus (Ni-P) foil with two different thicknesses (0.1 μm or 0.05 μm) and the same different sheet resistances (100 oh m/sq or 250 ohm/sq). The resistance rectangular resistors had length and width fro m the range between 0.59 and 5.91 mm. The resistance vs temperature characteristics and their distribution as well as resistors durability to low-temperature thermal shocks were investigated.
Microstructure and Phase Development of Buried Resistors in Low Temperature Co-fired Ceramic
Journal of Electroceramics, 2000
Embedded resistor circuits have been generated with the use of a Micropen system, Ag conductor paste (DuPont 6142D), a new experimental resistor ink from DuPont (E84005-140), and Low Temperature Co-fired Ceramic (LTCC) green tape (DuPont A951). Sample circuits were processed under varying peak temperature ranges (835°C–875°C) and peak soak times (10 min–720 min). Resistors were characterized by SEM, TEM, EDS, and high-temperature XRD. Results indicate that devitrification of resistor glass phase to Celcian, Hexacelcian, and a Zinc-silicate phase occurred in the firing ranges used (835–875°C) but kinetics of divitrification vary substantially over this temperature range. The resistor material appears structurally and chemically compatible with the LTCC. RuO2 grains do not significantly react with the devitrifying matrix material during processing. RuO2 grains coarsen significantly with extended time and temperature and the electrical properties appear to be strongly affected by the change in RuO2 grain size.
Environmentally sustainable composite resistors with low temperature coefficient of resistance
Microelectronic Engineering, 2009
Temperature coefficient of resistance (TCR) of thick film resistors are based on fired conducting grains and glass composites. Many analog sensor and control circuits require low (<100 ppm/°C) TCR value. To prepare resistors with low TCR value, knowledge of processing conditions and conduction mechanism parameters are of particular importance because TCR is finalised during firing and cannot be trimmed in the latter stage to a target value as resistors can be. This paper reports the preparation and properties such as microstructural and electrical in particular to sheet resistance, TCR (hot and cold) of eco-friendly composite resistor paste compositions. Our resistor compositions showed the sheet resistance in the range of 1.18-1.38 KX/h and the hot and cold TCR of the compositions reduced substantially from 360 to 100 ppm/°C and 175 to 60 ppm/°C with the addition of TCR modifier.
Materials Chemistry and Physics, 2007
Perovskite ruthenates, viz. CaRuO 3 , SrRuO 3 , BaRuO 3 , etc. although exhibit many interesting physical properties, have been seldom used in thick film resistors. In the preliminary attempts, we have formulated lead free thick film resistor paste compositions using CaRuO 3 . Five different paste compositions by varying the ruthenate concentration were prepared. Thick film resistors were screen printed onto an alumina substrate. Different thick film firing conditions were adopted to fire the resistors. Although, for TFRs, the standard conventional firing cycle is 850 • C, our TFR compositions can be fired even at a peak temperature of 800 • C. The evolution of microstructure and electrical performance of these resistors were studied. The resistors fired in conventional thick film firing furnace (BTU make) were found to be morphologically more uniform than the resistors fired in normal tube furnace. However, the sheet resistance value 'R s ' is lower (54-1.36 k / ) in case of resistors fired in tube furnace. On the other hand, resistors fired in thick film firing furnace exhibit higher range of sheet resistance (1.36-800 k / ). The hot and cold TCR range is 180-560 ppm/ • C in case of tube furnace fired resistors and 120-235 ppm/ • C for BTU furnace, which is comparatively lower than those reported earlier (>600 ppm/ • C) for other lead free resistors.