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

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The coating material can best be identified through proper documentation; for example, technicalmanuals and engineering drawings. If this information is not available, the experienced technician canusually determine the type of material by testing the, hardness, transparency, thickness, and solventsolubility of the coating. The thermal (heat) properties may also be tested to determine the ease ofremoval of the coating by heat. The methods of removal discussed here describe the basic concept, butnot the step-by-step "how to" procedures.THERMAL REMOVAL.—Thermal removal consists of using controlled heat through speciallyshaped tips attached to a handpiece. Soldering irons should never be used for coating removal because thehigh temperatures will cause the coatings to char, possibly damaging the board materials. Modified tips orcutting blades heated by soldering irons also are not used; they may not have proper heat capacity orallow the hand control necessary for effective removal. Also, the thin plating of the circuit may bedamaged by scraping.The thermal parting tool, used with the variable power supply, has interchangeable tips, as shown infigure 3-1, that allow for efficient coating removal. These thin, blade-like instruments act as heatgenerators and will maintain the heat levels necessary to accomplish the work. Tips can be changed easilyto suit the configuration of the workpiece. These tips cool quickly after removal of power because theirsmall thermal mass and special alloy material easily give up residual heat.Figure 3-1.—Thermal parting tips.The softening or breakdown point of different coatings vary, which is a concern when you are usingthis method. Ideally, the softening, point is below the solder melting temperature. However, when thesoftening point is equal to or above the solder melting point, you must take care in applying heat at thesolder joint or in component areas. The work must be performed rapidly to limit the heating of the areainvolved and to prevent damage to the board and other components.HOT-AIR JET REMOVAL.—In principle, the hot-air jet method of coating removal usescontrolled, temperature-regulated air to soften or break down the coating, as shown in figure 3-2. Bycontrolling the temperature, flow rate, and shape of the jet, you may remove coatings from almost anyworkpiece configuration without causing any damage. When you use the hot-air jet, you do not allow it to3-4
physically contact the workpiece surface. Delicate work handled in this manner permits you to observethe removal process.Figure 3-2.—Hot air jet conformal coating removal.POWER-TOOL REMOVAL DESCRIPTION.—Power-tool removal is the use of abrasivegrinding or cutting to mechanically remove coatings. Abrasive grinding/rubbing techniques are effectiveon thin coatings (less than 0.025 inch) while abrasive cutting methods are effective on coatings greaterthan 0.025 inch. This method permits consistent and precise removal of coatings without mechanicaldamage or dangerous heating to electronic components. A variable-speed mechanical drive handpiecepermits fingertip-control and proper speed and torque to ease the handling of gum-type coatings. Avariety of rotary abrasive materials and cutting tools is required for removal of the various coating types.These specially designed tools include BALL MILLS, BURRS, and ROTARY BRUSHES.The ball mill design places the most efficient cutting area on the side of the ball rather than at theend. Different mill sizes are used to enter small areas where thick coatings need to be removed(ROUTED). Rubberized abrasives of the proper grade and grit are ideally suited for removing thin, hardcoatings from flat surfaces; soft coatings adhere to and coat the abrasive causing it to become ineffective.Rotary bristle brushes work better than rubberized abrasives on contoured or irregular surfaces, such assoldered connections, because the bristles conform to surface irregularities. Ball mill routing and abrasionremoval are shown in figure 3-3.3-5
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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
Page 45 and 46: Figure 1-34.—Manufacturer's Data
Page 47: comparison to the distance between
Page 50 and 51: LEVEL III.—Drawers or pull-out ch
Page 52 and 53: Conductors located several layers b
Page 54 and 55: Figure 1-43A.—Evolution of modula
Page 56 and 57: ENVIRONMENTAL CONSIDERATIONSThe env
Page 58 and 59: SUMMARYThis topic has presented inf
Page 60 and 61: Rapid development has resulted in i
Page 62 and 63: Large DIPs are being used to packag
Page 64 and 65: MINIATURE ELECTRONICS are card asse
Page 66 and 67: Three methods of interconnecting ci
Page 68 and 69: ANSWERS TO QUESTIONS Q1. THROUGH Q5
Page 70 and 71: A43. Conventional printed circuit b
Page 72 and 73: Upon satisfactory completion of a 2
Page 74 and 75: One such improvement in system test
Page 76 and 77: those that should be observed when
Page 78 and 79: Figure 2-2.—Low voltage Handpiece
Page 80 and 81: Figure 2-6.—Rotary-drive machine
Page 82 and 83: Figure 2-9.—Pana Vise.HAND TOOLSF
Page 84 and 85: Figure 2-10a.—Pliers.TweezersView
Page 86 and 87: Even though all the items are not u
Page 88 and 89: Figure 2-14.—Stereoscopic zoom mi
Page 90 and 91: other than eutectic, go through a p
Page 92 and 93: A1. Chief of Naval Operations (CNO)
Page 94 and 95: CAUTIONTHIS SECTION IS NOT, IN ANY
Page 98 and 99: Figure 3-3.—Rotary tool conformal
Page 100 and 101: Figure 3-4A.—Eyelets (interfacial
Page 102 and 103: Figure 3-5B.—Clinched leads. SEMI
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
Page 114 and 115: Figure 3-15.—Component arrangemen
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.
Page 128 and 129: 5. The repair is completed using th
Page 130 and 131: SAFETYSafety is a subject of utmost
Page 132 and 133: OBJECT OR PROCESSWORK SURFACESFLOOR
Page 134 and 135: 8. When moving an ESDS device or as
Page 136 and 137: Power ToolsHazards associated with
Page 138 and 139: dispensers will prevent many accide
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
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MODULAR PACKAGING—Circuit assembl
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APPENDIX IIREFERENCE LISTCHAPTER ON
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Microelectronics—Continuedpackagi
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Assignment QuestionsInformation: Th
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1-7. Which of the following charact
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1-24. Vacuum evaporation and cathod
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___________________________________
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1-49. Ground planes and shielding a
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1-65. Which of the following types
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ASSIGNMENT 2Textbook assignment: Ch
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2-20. Turret, fork, and hook termin
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2-39. Component leads may be clippe
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2-52. To ensure a good mechanical b
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