Description of Task:Oil drilling reachesusually a depth of 2 to 3 km.
The drill heads containing a sophisticated sensorelectronic, which is collecting data permanently during the drilling process.Due to the friction temperature up to 300? may occur, only selected electroniccomponents may resist for a limited time. The circuit board (PCB) cannot bemade of brittle ceramic materials, because of the heavy vibrations are molded,to protect them against vibrations and ambient influences. Find, compare andevaluate materials and technologies for the printed circuit substrateencapsulating materials, to ensuring the function for a limited time.Problems in oil drilling:· Due to high temperature and pressure normal Ceramic brittlePCB cannot withstand that much of temperature.· Because of the high vibration PCB may physically damage.
· It may affected from chemical resistance· It lowers mechanical work ability and life span of PCB.Solutions of problems: In market there arevarious solutions for this problems is available, which are listed below:· Thick film technology· Thin film technology · Direct copper bonded technologyMaterials which are usedfor above listed technologies are listed here:· Alumina (Al2o3)· Aluminum Nitride (AIN) · Beryllium oxide (BeO), which is very toxic and dangerous forhuman so to use this technology, we must take care of hazardous effect of thismaterials. Definitions of various technologies:Thickfilm technology:The “ThickFilm” refers to the thickness of conductor layer on Ceramic PCB. Normallythe thickness will be at least exceeds 10 micron (um), around 10~13um, morethick than spurting technology in Thin Film Ceramic PCB. Of course thickness isless than DCB ceramic board or FR4 board. At the same time, usingthick film technology, we can put resistor, electric capacity, conductor,semi-conductor, and interchangeable conductor on ceramic board, aftermanufacturing steps of printing and high temperature sintering. We can make allthe resistors with the same value, or different value for different resistor onthe same board.
Thin filmtechnology:The “ThinFilm” refers to the thinner thickness of conductor layer on Ceramic PCB,comparing with “Thick film PCB”. Normally the thickness of thin film CeramicPCB will be less than 10 micron (10 um). That thin film was parting on ceramicsubstrate/core. In the same substrateusing evaporation, sputtering, electroplating process, and other thin filmmanufacturing technology to produce passive network, and assemble onmicro-components, devices separately, plus the hybrid integrated circuit formedby packaging. According to thecomponents parameters concentration and distribution situation in passivenetwork, thin film ceramic PCB is divided into lumped parameter and distributedparame- ter. The former appliesto low-frequency to microwave band, and later only applies to the microwaveband.
Directcopper bond technology (DCB):DCB (Direct Copper Bonded) sometimesalso named as DBC (Direct Bonded Copper) technology denotes a special processin which the copper foil and the Al2O3 or AIN (one orboth sides) are directly bonded under appropriate high temperature. The super-thin DCB substrate hasexcellent electrical isolation, high thermal conductivity, fine solder abilityand high bonding strength. It can be etched like normal FR4 PCB, but has a highcurrent loading capability. Therefore DCB ceramic PCB has become the basematerials of construction and interconnection technology of high powersemiconductor electronic circuits and also have been the basis for the”Chip On Board” (COB) technology which represent the packaging trendin the future.Importance of PCB(Film technology) compare to MCPCB (multilayer):Apart from MCPCB if we want to use PCBin high pressure, high insulation, high frequency, high temperature, and highreliable and minor volume electronic products, then Ceramic PCB will be ourbest choice.
Why Ceramic PCB has such excellentperformance? we can have a brief view on its basic structure and then we willunderstand.96% or 98% Alumina (Al2O3), Aluminum Nitride (AIN), or Beryllium Oxide (BeO). Conductors material: For thin, thick film technology, it’ll be silver palladium (AgPd), gold palladium (AuPd); For DCB (Direct Copper Bonded) it’ll be copper only. Thermal conductivity value: 24W~28W/m-K (Al2O3); 150W~240W/m-K for AIN , 220~250W/m-K for BeO; Max compression strength: >7,000 N/cm2 Application temperature 55? – 850?Breakdown Voltage (KV/mm): 15/20/28 for 0.25mm/0.63mm/1.0mm respectivelyThermal expansion coefficient(ppm/K): 7.4 (under 50~200C)Applications of PCB (by using above technologies): Oil drilling technologyHigh-accuracy clock oscillator, voltage controlled oscillator (VCXO), temperature compensated crystal oscillators (TCXOs), oven controlled crystal oscillators (OCXOs);Electric power electronic control module;Power hybridIndustrial electronic componentHigh insulation & high pressure device;High temperature (up to 800C) High power LEDHigh Power semiconductor modulesSolid state relay (SSR)DC-DC module power sourcesUnder water off-shore applicationsElectric power transmitter modules Solar-panel arrays Comparisons of various technologies: Parameters Thick film technology Thin film technology Direct copper bonded technology (DCB) Thickness of conductor layer 0.
01(mm) – 0.02(mm) Less than 0.01 (mm) 0.1(mm) – 0.3(mm) Temperature range Up to 500? Lower than Thick film 55? – 850? Cost (for same stack up) Lower than DCB Lower than Thick film Highest Conducting material Silver palladium, gold palladium, Mo/ Mu + Ni Same as thick film Al2O3, AIN Applications Oil drilling, high power LED,ensor Solar cell, Injection system, Automotive light system Industrial electronics, Power hybrids, Solid-state relays Parameters of designing PCB:Thick film technology: · Substrate can be 96% or 98% Alumina (Al2O3) or Beryllium Oxide (BeO), thickness range: 0.25, 0.38, 0.
50mm, 0.635mm (default thickness), 0.76mm, 1.0mm.
Thicker thickness such as 1.6mm or 2.0mm can be customized too. · Conductor layer material is silver palladium, gold palladium, or Mo/Mu+Ni (for Ozone); · Thickness of conductor >= 10 micron (um), and Max can be 20 micron (0.
02mm) · Min trace width and space for volume production: 0.30mm & 0.30mm, 0.20mm/0.20mm is also okay but cost will be higher, and 0.15mm/0.
20mm only available for prototype. · Tolerance for final trace layout will be +/-10% · Both gold and silver palladium is workable for gold-wire bonding, but customer need to mention that so that we will use special silver palladium which is suitable for that artwork. · Gold palladium is much more expensive than silver, about 10~20 times higher · More different resistor value on the same board, more expensive board will be · Normally layers are 1L and 2L (with plated through hole (PTH), and plated material is the same like the one used for conductor), and maximum layers can be 10 layers · Only board with Rectangle shape can be shipped via single piece, or via panel · Solder mask is also available upon request, working temperature >500 C, and color is semi-transparent. · For same stack up, cost lower than DCB, higher than MCPCB Thin film technology: · Compared to thick-film ceramic PCB, the major characteristics of thin-film circuits is the smaller size. However, the manufacturing equipment used is more expensive and the cost of production is higher. · Thin-film Ceramic PCB is suitable for a variety of circuits, especially for analog circuit which need high accuracy, great stability, and excellent performance. Compared with other circuit’s board, it is more suitable for microwave circuits. · There’re a number of ways to produce thin film layer, such as the normal physical vapor deposition (PVD), and less popular anodic oxidation or electroplating.
· In the physical vapor deposition (PVD) method, the most commonly used are evaporation process and the sputtering process. · Both two processes are carried out in a vacuum chamber, therefore, so they are called by a joint name as “vacuum film-forming method”. Using these two methods, passive components, interconnects trace, insulation film and protective film can be produced in passive network. · Interconnects trace, insulation film and protective film can be produced in passive network. · In manufacturing microwave hybrid integrated circuits, electroplating method can be used to increase the thickness of thin-film micro-strip line, in order to reduce power consumption. · Using anodic oxidation method, a dielectric film can be produced and resistance value of film resistor can be adjusted. Direct copper bonded technology (DCB): · High mechanical strength, mechanically stable shapes.
High strength, fine thermal conductivity, excellent electrical isolation. Good adhesion, corrosion resistant; · Excellent thermal cycling capabilities (up to 50,000 cycles), high reliability; · No contamination, free of environmental problem; · Wide application temperature: -55C~850C. The thermal expansion coefficient is closed to that of silicon, simplify the production technology of power module. · Compared to thin or thick film ceramic board, DCB has much thicker conductor (copper) which thickness will be 0.1mm~0.3mm.
Here are more advantage to use DCB Ceramic printed circuit board. Design of Thick film technology in details: · Conductive, resistive and dielectric films are selectively deposited by screen printing on ceramic substrates, · Mostly on 96 % alumina substrates. These films are dried and fired. They are of a fired thickness between 5 to 20?m in one print according to the type of the paste used. · If there is a requirement for thicker films it is necessary to use either special pastes or to print several times. The films are generally fired at temperatures higher than 500 °C. Standard substrate -alumina ceramic (Al2O3 ): · It is chemically resistant printed film pattern carrier that is resistant to high temperatures.
· It is outstanding electrical insulator and thermal conductor as well. It uses 96 % alumina ceramics made by own company process. · It is also possible to provide other ceramic materials, e.g. alumina 99 %, AlN or ZrO2. Printed substrates: · This is usually a ceramic substrate printed with conductive, dielectric or resistive films.
Maximum external substrate dimensions of are 200 by 200 mm, thickness can vary between 0.1 mm and 1 mm. · The substrates can be printed on one or on both sides. The patterns on both sides can be connected by metallized through-holes. · Each substrate side can be provided with more film levels (one-sided or double-sided multilayer film structure). Screen printing: · Technological process where conductive, resistive and dielectric pastes are applied using screen masks.
· The screen is made mostly of a stainless mesh. In some cases printing stencils made of thin stainless sheet are used. Screen: · A stainless mesh mask is fixed in a metallic frame. The mesh mask is photo-processed using a light sensitive emulsion. · The emulsion covers openings in the mesh and thus it masks the part of the substrate that should not be covered by the paste. · Open part of the meshes allows the paste deposition.
For each film pattern deposition one screen is needed. Thick film resistor: · Resistors are made by resistive paste printing, drying and firing. The resistance of a resistor is set by its dimensions and the paste type. Resistor trimming: · The precise resistance value is set by laser trimming. The resistor geometry is modified by sophisticated cuts.
· It is possible to attain precision of 0.5 % or better from nominal value of the resistor’s resistance. CO2 laser: · Laser system designed for machining fired alumina substrates (scribing, cutting and drilling). This procedure enables cutting out almost any pattern needed. When designing theprinted substrate customer should specify: 1. External dimensions of the substrate,other important dimensions and their tolerances.
2. Number and material of the films for theTOP and the BOTTOM side, minimum line width.3. Geometry of resistors, nominal resistorresistance, tolerance of this value, nominal power load of this resistor.4. Surface treatment of the printedsubstrate: passivation, tinning and pads solder ability, size of the pads forwire bonding, etc. 5.
Screens and printing templatesproduction, working out programs, production data.6. Special customer requirements. Conclusion:Many PCB technologies available on themarket, along with their individual benefits and disadvantages, are suitablefor its applications. As discussed above problem of oildrilling and its solution, we can conclude that:· By using PCB with special type of technology such as thickfilm technology, thin film technology and direct copper bonded technology(DCB), we can get more advantages than Multilayer PCB. · Advantages like temperature limit up to 850?, also it cangive protect to vibration (no breakdown of PCB), more life span, avoid problemsof corrosion etc.
· Cost of this film technology is also economically good andaccordingly application we can design thickness of conducting material andprice can be also vary according to applications.Nevertheless, all PCB types have theirbenefits, and which is best depends on the respective application withindividual requirements and conditions. Since PCB design, construction andmaterial are essential for optimized thermal designs, it is thereforerecommended to verify the total system. Hence, by using filmtechnology we can overcome problem arises to PCB due to high temperature whileoil drilling.