MICROELECTRONIC SYSTEM DESIGN CONCEPTS

1-32 Q32. On DIP and flat-pack ICs viewed from the top, pin 1 is located on which side of the reference mark? Q33. DIP and flat-pack pins are numbered consecutively in what direction? Q34. DIP and flat-pack pins are numbered consecutively in what direction? Q35. Viewed from the bottom, TO-5 pins are counted in what direction? Q36. The numbers and letters on ICs and schematics serve what purpose? MICROELECTRONIC SYSTEM DESIGN CONCEPTS You should understand the terminology used in microelectronics to become an effective and knowledgeable technician. You should be familiar with packaging concepts from a maintenance standpoint and be able to recognize the different types of assemblies. You should also know the electrical and environmental factors that can affect microelectronic circuits. In the next section of this topic we will define and discuss each of these areas. TERMINOLOGY As in any special electronics field, microelectronics terms and definitions are used to clarify communications. This is done so that everyone involved in microelectronics work has the same knowledge of the field. You can imagine how much trouble you would have remembering 10 or more different names and definitions for a resistor. If standardization didn't exist for the new terminology, you would have far more trouble understanding microelectronics. To standardize terminology in microelectronics, the Navy has adopted several definitions with which you should become familiar. These definitions will be presented in this section. Microelectronics Microelectronics is that area of electronics technology associated with electronics systems built from extremely small electronic parts or elements. Most of today's computers, weapons systems, navigation systems, communications systems, and radar systems make extensive use of microelectronics technology. Microcircuit A microcircuit is not what the old-time technician would recognize as an electronic circuit. The old- timer would no longer see the familiar discrete parts (individual resistors, capacitors, inductors, transistors, and so forth). Microelectronic circuits, as discussed earlier, are complete circuits mounted on a substrate (integrated circuit). The process of fabricating microelectronic circuits is essentially one of building discrete component characteristics either into or onto a single substrate. This is far different from soldering resistors, capacitors, transistors, inductors, and other discrete components into place with wires and lugs. The component characteristics built into microcircuits are referred to as ELEMENTS rather than discrete components. Microcircuits have a high number of these elements per substrate compared to a circuit with discrete components of the same relative size. As a matter of fact, microelectronic circuits often contain thousands of times the number of discrete components. The term HIGH EQUIVALENT CIRCUIT DENSITY is a description of this element-to-discrete part relationship. For example, suppose you have a circuit with 1,000 discrete components mounted on a chassis which is 8 ´ 10 ´ 2 inches. The equivalent circuit in microelectronics might be built into or onto a single substrate which is only 3/8 ´ 1 ´ 1/4 inch. The 1,000 elements of the microcircuit would be very close to each other (high density) by