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

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Figure 3-15.—Component arrangement.When possible, component identification markings should be visible after installation. If you mustchoose between identification and electrical value markings, the priority of selection is as follows: (1)electrical value, (2) reliability level, and (3) part number.Components are normally mounted parallel to and on the side opposite the printed circuitry and incontact with the board.FORMATION OF PROPER LEAD TERMINATION.—After component leads are formed andinserted into the board, the proper lead length and termination are made before the lead is soldered.Generally, if the original manufacturer clinched (either full or semi) the component leads, the replacementpart is reinstalled with clinched leads.When clinching is required, leads on single- and double-sided boards are securely clinched in thedirection of the printed wiring connected to the pad. Clinching is performed with tools that preventdamage to the pad or printed wiring. The lead is clinched in the direction of the conductor by bending thelead. The leads are clipped so that their minimum clinched length is equal to the radius of the pad. Underno circumstances does the clinched lead extend beyond the pad diameter. Natural springback away fromthe pad or printed wiring is acceptable. A gap between the lead end and the pad or printed wiring isacceptable when further clinching endangers the pad or printed wiring. These guidelines ensure uniformlead length.Q14. To what standards should a technician restore electronic assemblies?Q15. How is oxide removed from pads and component leads?Q16. Leads are formed approximately how many degrees from their major axis?Q17. When you replace components, identification marks must meet what requirements?3-22
Q18. In what direction are component leads clinched on single- and double-sided boards?Soldering of PCB ComponentsThe fundamental principles of solder application must be understood and observed to ensureconsistent and satisfactory results. As discussed in topic 2, the soldering process involves a metal-solventaction that joins two metals by dissolving a small amount of the metals at their point of contact.SOLDERABILITY.—As the solder interacts with the base metals, a good metallurgical bond isobtained and metallic continuity is established. This continuity is good for electrical and heat conductivityas well as for strength. Solderability measures the ease with which molten solder wets the surfaces of themetals being joined. WETTING means the molten solder leaves a continuous permanent film on the metalsurface. Wetting can only be done properly on a clean surface. All dirt and grease must be removed andno oxide layer must exist on the metal surface. Using abrasives and/or flux to remove these contaminantsproduces highly solderable surfaces.HEAT SOURCE.—The soldering process requires sufficient heat to produce alloy- or metal-solventaction. Heat sources include CONDUCTIVE, RESISTIVE, CONVECTIVE, and RADIANT types. Thetype of heat source most commonly used is the conductive-type soldering iron. Delicate electronicassemblies require that the thermal characteristics of a soldering iron be carefully balanced and that theiron and tip be properly matched to the job. Successful soldering depends on the combination of the irontip temperature, the capacity of the iron to sustain temperature, the time of iron contact with the joint, andthe relative mass and heat transfer characteristics of the object being soldered.SELECTION OF PROPER TIP.—The amount of heat and how it is controlled are critical factorsto the soldering process. The tip of the soldering iron transfers heat from the iron to the work. The shapeand size of the tip are mainly determined by the type of work to be performed. The tip size and thewattage of the element must be capable of rapidly heating the mass to the melting temperature of solder.After the proper tip is selected and attached to the iron, the operator may control the heat by usingthe variable-voltage control. The most efficient soldering temperature is approximately 550 degreesFahrenheit. Ideally, the joint should be brought to this temperature rapidly and held there for a shortperiod of time. In most cases the soldering action should be completed within 2 or 3 seconds. Whensoldering a small-mass connection, control the heat by decreasing the size of the tip.Before heat is applied to solder the joint, a thermal shunt is attached to sensitive component leads(diodes, transistors, and ICs). A thermal shunt is used to conduct heat away from the component. Becauseof its large heat content and high thermal conductivity, copper is usually used to make thermal shunts.Aluminum also has good conductivity but a smaller heat content; it is also used to conduct heat,especially if damage from the physical weight of the clamp is possible. Many types, shapes, and sizes ofthermal shunts are available. The most commonly used is the clamp design; this is a spring clip (similar toan alligator clip) that easily fastens onto the part lead, as shown in figure 3-16.3-23
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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
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 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 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
Page 149: APPENDIX IIREFERENCE LISTCHAPTER ON
Page 152 and 153: Microelectronics—Continuedpackagi
Page 155: Assignment QuestionsInformation: Th
Page 158 and 159: 1-7. Which of the following charact
Page 160 and 161: 1-24. Vacuum evaporation and cathod
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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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