MICROELECTRONICS

• Microelectronics


  Field of electronics engineering that deals with the design and fabrication of small electronic devices such as microprocessors, using techniques such as photolithography.
• The small electronic devices are typically fabricated using microelectromechanical systems (MEMS) or microelectronic mechanical systems (MEMS).
• Microelectromechanical systems (MEMS)


  These are small structures that can be integrated into electronic circuits.
• Semiconductor materials


  These are the building blocks of microelectronics.
• One key aspect of microelectronics is the use of semiconductor materials, such as silicon, to create the small structures and devices that are needed.
• Benefits of Microelectronics

  1. Miniaturization
  2. Power Efficiency
  3. Advancements in computing
  4. Innovation across industries
  5. Economic impact
• Vacuum Tubes


  Controls flow of electric current; used in transistors for amplifiers
• 1 integrated circuit = m/billions of transistors
• Transistors


  Three terminal device; usually for amplifiers.
• Semiconductor Diode


  Two terminal device
• Vacuum tubes uses metal chassis which weighs 40 to 50 pounds.
• Vacuum tubes required a warm-up time from 1 to 2 minutes, it generated a lot of heat.
• Vacuum tubes required hefty power supply voltages of 300 volts dc and more.
• A circuit could be designed either as a complete system or as a functional part of a larger system.
• In complex systems, such as radar, many separate circuits were needed to accomplish the desired tasks.
• Multiple function tubes, such as dual diodes, dual triodes, tetrodes, and others helped considerably to reduce the size of circuits.
• Weight, heat, and power consumption continued to be problems that plagued designers.
• Point-to-point wiring


  A method of wiring components which is another major problem with vacuum-tube circuits.
• Point-to-point wiring


  This wiring looks like a rat's nest and it often caused unwanted interactions between components.
• Point-to-point wiring

  Usually repaired with general purpose test equipment and common hand tools.
• EINAC


  A completely electronic computer built in 1945 which contained 18,000 tubes. It often required a full day just to locate and replace faulty tubes.
• Cathode-ray tubes


  Used in radar, television, and oscilloscopes do not, as yet, have solid-state counterparts.
• MODULAR PACKAGING


  One concept that eased the technician's job because instead of building a system on one large chassis, it was built of modules or blocks.
• Vacuum tubes


  Basis for electronic technology for many years and some are still with us.
• The emphasis of technology is in the field of microelectronics.
• Applications of Microelectronics

  1. Integrated Circuits
  2. Microprocessors
  3. Memory Devices
  4. Microsensors and Actuators
  5. Microcontrollers
• Solid-State Devices


  Device which electrically flows through solid semiconductor crystals rather than vacuum tubes
• Solid-state chassis


  Considerably smaller and lighter than the older tube chassis.
• Printed Circuit Board (PCB)


  One of the most significant developments in circuit packaging.
• Printed Circuit Board (PCB)


  Usually an epoxy board on which the circuit leads have been added by the photoetching process.
• Photoetching process


  This process is similar to photography in that copper-clad boards are exposed to controlled light in the desired circuit pattern and then etched to remove the unwanted copper.
• Photoetching process leaves copper strips (LANDS) that are used to connect the components.
• Printed Circuit Boards eliminate both the heavy, metal chassis, and the point-to-point wiring.
• Vacuum tubes are easily removed for testing or replacements while PCB components are soldered into place and are not as easily removed.
• Normally, each PCB circuit contains a single circuit or a subassembly of a system.
• Cabling Harnesses


  Groups of wiring or ribbons of wiring.
• All printed circuit boards within the system are routinely interconnected through cabling harnesses.
• Cordwood Module


  Another mounting form that has been used to increase the number of components in a given space.
• In cordwood module, components are placed perpendicular to the end plates.
• The components in a cordwood module are closely packed, appearing to be stacked like a cordwood for a fireplace.