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

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Figure 3-19.—TO mounting techniques.The procedure for removal of plug-in TOs (with or without conformal coatings) is the same as thatused for a similarly mounted DIP or discrete component. The conformal coating is removed if required.Leads are desoldered and gently lifted out of the board. Then board terminals and component leads arecleaned.In some plug-ins, the leads must be formed before they are placed in a circuit. Care should be takento ensure that seal damage does not occur and that formed leads do not touch the TO case. This wouldresult in a short-circuit.When the new part or the one that was removed is installed, the leads are slipped through the spacerif required, and the part is properly positioned (reference tab in the proper location). The leads are alignedwith the terminal holes and gently pressed into position. The part is soldered into place and visuallyinspected. Then the card is tested and the conformal coating is replaced if required.The removal of an imbedded TO package varies only slightly from the removal of other types ofmountings. First, the work area is masked and the conformal coating is removed if required. Then thedesoldering handpiece is used to remove the solder from each lead. When all leads are free, the TO ispushed out of the board. If all the leads are free, the TO should slip out of the board easily. The packageshould not be forced out of the board. Excessive pressure may cause additional damage. If the leads arenot completely free, the leads must be clipped and removed after the package is out of the board. Thisprocess is shown in figure 3-20.3-28
Figure 3-20.—Imbedded TO removal.The most critical part of replacing an imbedded TO is the lead formation. The leads are formed tomatch the original part as closely as possible. Once the body and leads are seated, the leads can besoldered and the board inspected.REMOVAL AND REPLACEMENT OF FLAT PACKSUp to this point, all of the components discussed have had through-the-board leads. In addition, theremoval and replacement of discrete components, DIPs, and TOs have been similar.PLANAR-MOUNTED COMPONENTS (FLAT-PACKS)Different techniques are used in the removal and replacement of flat packs and devices with on-theboardterminations. Lap-flow solder joints require that the technician pay particular attention toworkmanship. Some of the standards of workmanship will be discussed later in this section.Flat-Pack RemovalPrior to the removal of a flat pack, as with other ICs, a sketch should be prepared to identify theproper positioning of the part. The conformal coating should be removed as required.To remove the flat pack, the 2M technician carefully heats the leads and lifts them free withtweezers. If the part is to be reused, special care is taken not to damage or bend the leads. The work areaaround the component should then be thoroughly cleaned and prepared for the new part.Flat-Pack ReplacementFlat packs attached to boards normally have formed and trimmed leads. Manufacturers form and trimthe leads in one operation with a combination die. However, most replacement flat packs are received in aprotective holder (figure 3-21) and the leads must be formed and trimmed by hand. Cost preventsequipping the repair station with the variety of tools and dies to form leads because of the variety ofcomponent configurations.3-29
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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
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 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 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
Page 162 and 163: ___________________________________
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
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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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