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

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Figure 3-3.—Rotary tool conformal coating removal.CUT AND PEEL.—Silicone coatings (also referred to as RTV) can easily be removed by cuttingand peeling. As with all mechanical removal methods, care must be taken to prevent damage to eithercomponents or boards.CHEMICAL REMOVAL.—Chemical removal uses solvents to break down the coatings. Generalapplication is not recommended as the solvent may cause damage to the boards by dissolving the adhesivematerials that bond the circuits to the boards. These solvents may also dissolve the POTTINGCOMPOUNDS (insulating material that completely seals a component or assembly) used on other partsor assemblies. Only thin acrylic coatings (less than 0.025 inch) are readily removable by solvents. Mildsolvents, such as ISOPROPYL ALCOHOL, XYLENE, or TRICHLOROETHANE, may be used toremove soluble coatings on a spot basis.Evaluations show that many tool and technique combinations have proven to be reliable andeffective in coating removal; no single method is the best in all situations. When the technician isdetermining the best method of coating removal to use, the first consideration is the effect that it will haveon the equipment.Conformal Coating ReplacementOnce the required repairs have been completed the conformal coating must be replaced. To ensurethe same protective characteristics, you should use the same type of replacement coating as that removed.3-6
Conformal coating application techniques vary widely. These techniques depend on material type,required thickness of application, and the effect of environmental conditions on curing. These procedurescannot be effectively discussed here.Q1. What material is applied to electronic assemblies to prevent damage from corrosion, moisture,and stress?Q2. What three methods are used to remove protective material?Q3. What chemicals are used to remove protective material?Q4. Abrasion, cutting, and peeling are examples of what type of protective material removal?Q5. Why should the coating material be replaced once the required repair has been completed?REMOVAL AND REPLACEMENT OF DISCRETE COMPONENTSTo properly perform the required repair, the 2M technician must be knowledgeable of the techniquesused by manufacturers in the production of electronic assemblies. The techniques, materials, and types ofcomponents determine the repair procedures used.Interconnections and AssembliesAssemblies may range from simple, single-sided boards with standard-sized components to doublesidedor multilayered boards with miniature and microminiature components. The variations incomponent lead termination and mounting techniques used by manufacturers present the technician with acomplex task. For example, the 2M technician is concerned about the type of solder joints on the module.To determine the solder joint type, the technician must consider the board circuitry, hole reinforcement,and lead termination style.Recall the discussion from topic 1 on printed circuit board construction and the types ofinterconnections used. Single-sided and some double-sided boards have UNSUPPORTED HOLES wherecomponent leads are soldered to the pad. The clearance-hole method is also an interconnection with nohole support. SUPPORTED HOLES are those that have metallic reinforcement along the hole walls.In addition to the plated-through hole you studied earlier, EYELETS, shown in figure 3-4, view (A),view (B), and view (C), are also used in both manufacturing and repair. These hole-reinforcing devicesare usually made of pure copper, but are often plated with gold, tin, or a tin-lead alloy. The copper-basedeyelet is pliable; when set, it reduces the possibility of circuit board damage. Eyelets may be inserted intosingle-sided or double-sided boards and are of three different types - ROLL SET, FUNNEL SET, andFLAT SET. All three are types referred to as INTERFACIAL CONNECTIONS. Interfacial connectionsidentify the procedure of connecting circuitry on one side of a board with the circuitry on the other side.3-7
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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
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 96 and 97: The coating material can best be id
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
Page 147 and 148: 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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