scholarly journals Joining of Electrodes to Ultra-Thin Metallic Layers on Ceramic Substrates in Cryogenic Sensors

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4919
Author(s):  
Marcin Lebioda ◽  
Ryszard Pawlak ◽  
Jacek Rymaszewski
Keyword(s):  
Cryogenic Temperatures ◽  
Thermal And Mechanical Properties ◽  
Reflow Soldering ◽  
Ceramic Substrates ◽  
Temperature Range ◽  
Wave Soldering ◽  
Materials Used ◽  
Standard Designs ◽  
Electrical Connections ◽  
Method Show

Microjoining technologies are crucial for producing reliable electrical connections in modern microelectronic and optoelectronic devices, as well as for the assembly of electronic circuits, sensors, and batteries. However, the production of miniature sensors presents particular difficulties, due to their non-standard designs, unique functionality and applications in various environments. One of the main challenges relates to the fact that common methods such as reflow soldering or wave soldering cannot be applied to making joints to the materials used for the sensing layers (oxides, polymers, graphene, metallic layers) or to the thin metallic layers that act as contact pads. This problem applies especially to sensors designed to work at cryogenic temperatures. In this paper, we demonstrate a new method for the dynamic soldering of outer leads in the form of metallic strips made from thin metallic layers on ceramic substrates. These leads can be used as contact pads in sensors working in a wide temperature range. The joints produced using our method show excellent electrical, thermal, and mechanical properties in the temperature range of 15–300 K.

Root Cause Analysis of a Connector Time-Delayed Fracture

2015 ◽  
Author(s):  
Prabjit Singh ◽  
Ying Yu ◽  
Robert E. Davis
Keyword(s):  
Printed Circuit Board ◽  
Ceramic Substrate ◽  
Circuit Board ◽  
Delayed Fracture ◽  
Ceramic Substrates ◽  
Printed Circuit ◽  
Root Cause ◽  
Chip Carrier ◽  
Electrical Connections ◽  
Grain Boundary Grooves

Abstract A land-grid array connector, electrically connecting an array of plated contact pads on a ceramic substrate chip carrier to plated contact pads on a printed circuit board (PCB), failed in a year after assembly due to time-delayed fracture of multiple C-shaped spring connectors. The land-grid-array connectors analyzed had arrays of connectors consisting of gold on nickel plated Be-Cu C-shaped springs in compression that made electrical connections between the pads on the ceramic substrates and the PCBs. Metallography, fractography and surface analyses revealed the root cause of the C-spring connector fracture to be plating solutions trapped in deep grain boundary grooves etched into the C-spring connectors during the pre-plating cleaning operation. The stress necessary for the stress corrosion cracking mechanism was provided by the C-spring connectors, in the land-grid array, being compressed between the ceramic substrate and the printed circuit board.

Joining of Sintered Alumina Substrates and LTCC Green Tapes via Cold Low Pressure Lamination

2013 ◽  
Vol 2013 (CICMT) ◽  
pp. 000268-000274
Author(s):  
Michael Hambuch ◽  
Frieder Gora ◽  
Karin Beart ◽  
Frieder Wittmann ◽  
Andreas Roosen
Keyword(s):  
Heat Conductivity ◽  
Heat Dissipation ◽  
Low Pressure ◽  
Adhesive Tape ◽  
Sintered Ceramic ◽  
Multilayer Systems ◽  
Ceramic Substrates ◽  
Adhesive Film ◽  
Lamination Process ◽  
Materials Used

In microelectronics there is a continuous trend for devices of higher integration and improved heat dissipation. For the manufacture of ceramic based microelectronic devices the following technologies can be applied. Thick-film hybrid technology uses sintered ceramic substrates, mostly Al2O3, which are screen printed with functional pastes, followed by firing at 850 °C. Alumina substrates provide very good heat conductivity (25 W/mK), but there are only two sides to carry a metallization. An improved miniaturization can be accomplished by multilayer systems using the LTCC technology. LTCC devices are manufactured by screen-printing, stacking and lamination of ceramic green tapes, followed by co-firing. A drawback of LTCCs is their low heat conductivity (3 W/mK) due to their high glass content. By combining hybrid and LTCC technology the advantages of both methods like good thermal conductivity and high multilayer integration, can be joined. Because the failure rate is too high to laminate green tapes on sintered ceramic substrates via thermo compression, Cold Low Pressure Lamination (CLPL) has been used as an alternative lamination process. CLPL is a lamination method, where the joining of the components is performed at room temperature by application of very low pressure (<5 MPa) by using a double sided adhesive tape. During heat treatment the adhesive film keeps the tapes together until the adhesive is completely decomposed; during further temperature increase the tapes are joined by sintering. The paper describes the materials used and processing steps to join the sintered material with the green tapes and discusses effects which occur during firing. These effects like edge curl and crack formation are mainly due to stresses which occur during constrained sintering. Their control can be influenced by changing process parameters.

Actively Cooled Current Leads for Superconducting Electronics Using Mixed-Gas Joule-Thomson Refrigeration

2004 ◽  
Author(s):  
Gregory F. Nellis ◽  
John M. Pfotenhauer ◽  
Sanford A. Klein
Keyword(s):  
Superconducting Magnets ◽  
Pure Substance ◽  
Genetic Optimization ◽  
Mixed Gas ◽  
Thermal Generation ◽  
Reliable Technique ◽  
Temperature Range ◽  
Current Leads ◽  
Gas Cooling ◽  
Materials Used

Electrical leads used for the supply of current to superconducting magnets and electronics must span the temperature range from room temperature to cryogenic temperatures. Because the conventional materials used for such purposes (e.g., copper and aluminum) have both a finite electrical resistance and a significant thermal conductivity, operation of the leads results in both thermal generation and conductance. The resulting thermal loads must be removed from the cryogenic environment. This paper describes a method for integrating cryogenic refrigeration technology with current leads in an efficient and practical manner. The key to this concept is the use of a mixed-gas cooling cycle that absorbs the distributed refrigeration load continuously over the temperature range that it is generated, as opposed to allowing it to pass down to the cold end of the lead where the same energy flow constitutes a much higher entropy load on the cryocooler. Additional benefits of this technology include a more isothermal electronic package, as well as improvements in reliability, and reduction in size and mass. Mixed-gas working fluids can be used within Joule-Thomson devices to achieve a greater refrigeration effect for the same pressure span than is possible with a pure substance. This paper describes a computational tool that allows the composition of gas mixtures to be optimized for the case where the refrigeration load is not completely concentrated at the cold end, as is typically the case, but rather the refrigeration load is distributed over the entire temperature range. A genetic optimization algorithm was found to be the most robust and reliable technique for identifying optimum gas mixture composition. The thermodynamic advantage associated with accepting the refrigeration load at the temperature of its origin, rather than at the cold end, is quantified.

scholarly journals Fluorescence quantum efficiency of Ti3+:Al2O3 at cryogenic temperatures and excitation by laser diodes

2021 ◽  
Vol 2067 (1) ◽  
pp. 012010
Author(s):  
A Gribanov ◽  
G Nikolaev ◽  
M Mosin ◽  
D Yakovin ◽  
M Yakovin
Keyword(s):  
Quantum Efficiency ◽  
Cryogenic Temperature ◽  
Laser Diodes ◽  
Czochralski Method ◽  
Sapphire Crystal ◽  
Cryogenic Temperatures ◽  
Temperature Range ◽  
Temperature Dependences ◽  
First Time

Abstract In this work the temperature dependences of the fluorescence of a titanium-sapphire crystal excited by radiation with λ=507 nm, λ=454 nm and λ=405 nm are measured. The quantum efficiency of fluorescence is determined. It was found for the first time that the quantum efficiency of fluorescence exceeds 100% in the cryogenic temperature range when the crystal is excited by radiation with λ = 454 nm. It is equal to (117 ± 5) % and (114 ± 5) % at T = 77 K for crystals grown by the Czochralski method and by gradient of temperature one, respectively.

scholarly journals Hybrid Fly Ash-Based Geopolymeric Foams: Microstructural, Thermal and Mechanical Properties

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2919 ◽  
Author(s):  
Giuseppina Roviello ◽  
Laura Ricciotti ◽  
Antonio Jacopo Molino ◽  
Costantino Menna ◽  
Claudio Ferone ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Circular Economy ◽  
Coal Fly Ash ◽  
Silicate Solution ◽  
Thermal And Mechanical Properties ◽  
Blowing Agent ◽  
Materials Used

This research investigates the preparation and characterization of new organic–inorganic geopolymeric foams obtained by simultaneously reacting coal fly ash and an alkali silicate solution with polysiloxane oligomers. Foaming was realized in situ using Si0 as a blowing agent. Samples with density ranging from 0.3 to 0.7 g/cm3 that show good mechanical properties (with compressive strength up to ≈5 MPa for a density of 0.7 g/cm3) along with thermal performances (λ = 0.145 ± 0.001 W/m·K for the foamed sample with density 0.330 g/cm3) comparable to commercial lightweight materials used in the field of thermal insulation were prepared. Since these foams were obtained by valorizing waste byproducts, they could be considered as low environmental impact materials and, hence, with promising perspectives towards the circular economy.

A large anisotropic plasticity of L-leucinium hydrogen maleate preserved at cryogenic temperatures

2019 ◽  
Vol 75 (2) ◽  
pp. 143-151 ◽  
Author(s):  
S. G. Arkhipov ◽  
E. A. Losev ◽  
T. T. Nguyen ◽  
D. A. Rychkov ◽  
E. V. Boldyreva
Keyword(s):  
Organic Compound ◽  
Structural Changes ◽  
Cryogenic Temperatures ◽  
Ambient Conditions ◽  
Anisotropic Plasticity ◽  
Temperature Range ◽  
Cryogenic Conditions

L-Leucinium hydrogen maleate crystals are very plastic at ambient conditions. Here it is shown that this plasticity is preserved at least down to 77 K. The structural changes in the temperature range 293–100 K were followed in order to rationalize the large anisotropic plasticity in this compound. To the best of our knowledge, this is the first reported example of an organic compound remaining so plastic at cryogenic conditions.

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