Navy Electricity and Electronics Training Series - Historic Naval ...

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SAFETYSafety is a subject of utmost importance to all technical personnel. Potentially hazardous situationsexist in almost any work area. The disregard of safety precautions can result in personal injury or in theloss of equipment or equipment capabilities.In this section we will discuss two types of safety factors. First, we will cover damage that can occurto electronic components because of electrostatic discharge (ESD) and improper handling and stowage ofparts and equipment. Second, we will cover personal safety precautions that specifically concern thetechnician.ELECTROSTATIC DISCHARGEElectrostatic discharge (ESD) can destroy or damage many electronic components includingintegrated circuits and discrete semiconductor devices. Certain devices are more susceptible to ESDdamage than others. Because of this, warning symbols are now used to identify ESD-sensitive (ESDS)items (figure 3-31).Figure 3-31.—Warning symbols for ESDS devices.Static electricity is created whenever two substances (solid or fluid) are rubbed together or separated.This rubbing or separation causes the transfer of electrons from one substance to the other; one substancethen becomes positively charged and the other becomes negatively charged. When either of these chargedsubstances comes in contact with a conductor, an electrical current flows until that substance is at thesame electrical potential as ground.You commonly experience static build-up during the winter months when you walk across a vinyl orcarpeted floor. (Synthetics, especially plastics, are excellent generators of static electricity.) If you thentouch a door knob or other conductor, an electrical arc to ground may result and you may receive a slightshock. For a person to experience such a shock, the electrostatic potential created must be 3,500 to 4,000volts. Lesser voltages, although present and similarly discharged, normally are not apparent to a person'snervous system. Some typical measured static charges caused by various actions are shown in table 3-2.3-38
Table 3-2.—Typical Measured Statics Charges (in volts)RELATIVE HUMIDITYITEMLOW (10-20%) HIGH (65-90%)WALKING ACROSS CARPET 35,000 1,500WALKING OVER VINYL FLOOR 12,000 250WORKER AT BENCH 6,000 100VINYL ENVELOPES FOR WORK INSTRUCT. 7,000 600POLY BAG PICKED UP FROM BENCH 20,000 1,200WORK CHAIR PADDED WITH URETHANE FOAM 18,000 1,500Metal oxide semiconductor (MOS) devices are the most susceptible to damage from ESD. Forexample, an MOS field-effect transistor (MOSFET) can be damaged by a static voltage potential of aslittle as 35 volts. Commonly used discrete bipolar transistors and diodes (often used in ESD-protectivecircuits), although less susceptible to ESD, can be damaged by voltage potentials of less than 3,000electrostatic volts. Damage does not always result in sudden device failure but sometimes results indevice degradation and early failure. Table 3-2 clearly shows that electrostatic voltages well in excess of3,000 volts can be easily generated, especially under low-humidity conditions. ESD damage of ESDSparts or circuit assemblies is possible wherever two or more pins of any of these devices are electricallyexposed or have low impedance paths. Similarly, an ESDS device in a printed circuit board, or even inanother pcb that is electrically connected in a series can be damaged if it provides a path to ground.Electrostatic discharge damage can occur during the manufacture of equipment or during the servicing ofthe equipment. Damage can occur anytime devices or assemblies are handled, replaced, tested, or insertedinto a connector.Technicians should be aware of the many sources of static charge. Table 3-3 lists many commonsources of electrostatic charge. Although they are of little consequence during most daily activity, theybecome extremely important when you work with ESD material.3-39
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NONRESIDENTTRAININGCOURSESEPTEMBER
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PREFACEBy enrolling in this self-st
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TABLE OF CONTENTSCHAPTERPAGE1. Micr
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Module 11, Microwave Principles, ex
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INSTRUCTIONS FOR TAKING THE COURSEA
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THIS PAGE LEFT BLANK INTENTIONALLY.
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CHAPTER 1MICROELECTRONICSLEARNING O
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VACUUM-TUBE EQUIPMENTVacuum tubes w
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SOLID-STATE DEVICESNow would be a g
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FILM INTEGRATED CIRCUITS are broken
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Development of a microelectronic de
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Figure 1-9.—Crystal furnace.The c
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Figure 1-12.—Planar-diffused tran
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Figure 1-14.—Vacuum evaporation o
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Figure 1-17.—Cathode-sputtering m
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Q23. How do the two types of monoli
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Figure 1-21A.—TO-5 mounting PLUG-
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Dual Inline PackageThe dual inline
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wafer, as shown in figure 1-27. Thi
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Figure 1-29.—J-K flip-flop discre
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Figure 1-31.—Lead numbering for a
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Figure 1-34.—Manufacturer's Data
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comparison to the distance between
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LEVEL III.—Drawers or pull-out ch
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Conductors located several layers b
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Figure 1-43A.—Evolution of modula
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ENVIRONMENTAL CONSIDERATIONSThe env
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SUMMARYThis topic has presented inf
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Rapid development has resulted in i
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Large DIPs are being used to packag
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MINIATURE ELECTRONICS are card asse
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Three methods of interconnecting ci
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ANSWERS TO QUESTIONS Q1. THROUGH Q5
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A43. Conventional printed circuit b
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Upon satisfactory completion of a 2
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One such improvement in system test
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those that should be observed when
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Figure 2-2.—Low voltage Handpiece
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Page 82 and 83: Figure 2-9.—Pana Vise.HAND TOOLSF
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Page 88 and 89: Figure 2-14.—Stereoscopic zoom mi
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Page 98 and 99: Figure 3-3.—Rotary tool conformal
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Page 104 and 105: Figure 3-8A.—Terminals. PIN AND T
Page 106 and 107: Figure 3-8E.—Terminals. SOLDER CU
Page 108 and 109: Figure 3-10.—Solder wicking.This
Page 110 and 111: Figure 3-12B.—Motorized vacuum/pr
Page 112 and 113: INSTALLATION AND SOLDERING OF PRINT
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Page 116 and 117: Figure 3-16.—Thermal shunt.APPLIC
Page 118 and 119: Removal of Plug-In DIPsTo remove pl
Page 120 and 121: Figure 3-19.—TO mounting techniqu
Page 122 and 123: Figure 3-21.—Flat pack in protect
Page 124 and 125: Figure 3-23.—Pcb conductor damage
Page 126 and 127: REPAIRING DELAMINATED CONDUCTORS.
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Page 134 and 135: 8. When moving an ESDS device or as
Page 136 and 137: Power ToolsHazards associated with
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Page 140 and 141: A GOOD SOLDER JOINT is bright and s
Page 142 and 143: ANSWERS TO QUESTIONS Q1. THROUGH Q3
Page 145 and 146: APPENDIX IGLOSSARYALLOWANCE PARTS L
Page 147 and 148: MODULAR PACKAGING—Circuit assembl
Page 149: APPENDIX IIREFERENCE LISTCHAPTER ON
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Page 160 and 161: 1-24. Vacuum evaporation and cathod
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Page 164 and 165: 1-49. Ground planes and shielding a
Page 166 and 167: 1-65. Which of the following types
Page 168 and 169: ASSIGNMENT 2Textbook assignment: Ch
Page 170 and 171: 2-20. Turret, fork, and hook termin
Page 172 and 173: 2-39. Component leads may be clippe
Page 174 and 175: 2-52. To ensure a good mechanical b
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