Module 14 - Introduction to Microelectronics
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![Card holder and magnifier - RF Cafe](images/14211img67.gif)
Figure 2-7. - Card holder and magnifier.
High-INTENSITY LIGHT The high-intensity light provides a variable, high-intensity,
portable light source over the work area. The two flexible arms permit both front and back lighting of the
workpiece and provide a balanced light that eliminates shadows (figure 2-8).
![High intensity lamp - RF Cafe](images/14211img69.gif)
Figure 2-8. - High intensity lamp.
The high-intensity light uses 115-volt, 60-hertz input power. One brightness knob controls a flood- type bulb,
and the other knob controls a spot-type bulb. PANA VIsE This nylon-jawed,
multiposition vise can rotate and tilt. With this flexibility the technician can achieve any compound angle for
holding a workpiece during assembly, modification, or repair (figure
2-9).
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![Pana Vise - RF Cafe](images/14211img6B.gif)
Figure 2-9. - Pana Vise.
Hand TOOLS Figure 2-10, views (A) through (C), shows some representative types of hand
tools used in 2M repair procedures.
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![Pliers, tweezers, and dental tools - RF Cafe](images/14211img6D.gif)
Figure 2-10. - Pliers, tweezers, and dental tools.
Pliers In view (A), the figure shows the pliers preferred for 2M repair procedures.
These precision pliers have a long and useful life if handled and cared for properly. The flush-cutting pliers are used to cut various sizes of wire and component leads. The needlenose, roundnose, and flatnose pliers are used for
forming, looping, and bending wires and component leads. They are also used for gripping components and leads
during removal or installation.
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![Pliers - RF Cafe](images/14211img6F.gif)
Figure 2-10a. - Pliers.
Tweezers View (B) shows tweezers contained in the 2M repair set. The top two pairs of
tweezers are used to hold small components during installation and repair procedures. The other pairs are
anti-wicking tweezers used to tin and solder stranded wire leads. Dental Tools
View (C) shows some of the dental tools contained in the 2M repair set. They are used for picking, chipping,
abrading, mixing, and smoothing various conformal coatings used on printed circuit boards and other general pcb
repair techniques.
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![Dental tools - RF Cafe](images/14211img71.gif)
Figure 2-10c. - Dental tools.
Eyelet-Setting Tools Among the repair procedures required of the 2M repair technician
is the replacement of eyelets. Eyelets must sometimes be replaced because of the damage caused by incorrect repair
procedures or complete failure of a printed circuit board. Figure 2-11 illustrates the tools used to replace these
eyelets. Eyelets will be discussed in topic 3.
![Eyelet-setting tools - RF Cafe](images/14211img73.gif)
Figure 2-11. - Eyelet-setting tools.
Miscellaneous TOOLS and SUPPLIES An assortment of some of the miscellaneous items used
in 2M repair are shown in figure 2-12. a variety of brushes, files, scissors, thermal shunts, and consumables,
such as solder wick, are included.
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Even though all the items are not used in every repair procedure, it is extremely important that they be
available for use should the need arise.
![Miscellaneous tools and supplies - RF Cafe](images/14211img75.gif)
Figure 2-12. - Miscellaneous tools and supplies.
Safety Equipment The nature of 2M repair requires items to be included in the tool kit
for the personal safety of the technicians. The goggles and respirator illustrated in figure 2-13 have been
approved for use by the technician. These should be worn at all times where dust, chips, fumes, and other
hazardous substances are generated as a result of drilling, grinding, or other repair procedures.
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![Safety equipment - RF Cafe](images/14211img77.gif)
Figure 2-13. - Safety equipment.
STEREOSCOPIC-ZOOM MICROSCOPE The stereoscopic-zoom microscope provides a versatile
optical viewing system. This viewing system is used in the fault detection, fault isolation, and repair of complex
microminiature circuit boards and components. Figure 2-14 shows the microscope mounted on an adjustable stand. The
microscope has a minimum of 3.5X and a maximum of 30X magnification to detect hairline cracks in conductor runs
and stress cracks in solder joints.
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![Stereoscopic zoom microscope - RF Cafe](images/14211img79.gif)
Figure 2-14. - Stereoscopic zoom microscope.
TOOL CHEST The tool chest (not shown), provides storage space for the electronic
repair hand tools, dental tools, abrasive wheels, solder and solder wicks, eyelets, abrasive disks, ball mills,
various burrs, and other consumables used with the repair procedures. The chest is portable, lockable, and has
variously sized drawers for convenience. REPLACEMENT PARTS Replacement parts are
provided with the 2M repair set to ensure the technician has the capability to maintain the equipment properly.
Actual preventive and corrective maintenance procedures, as well as data on additional spare parts and ordering
information, are found in the technical manual for the 2M repair set equipment.
REPAIR STATION FACILITIES
To be effective, 2M electronic component repair must be performed under proper environmental conditions. Repair
facility requirements, whether afloat or ashore, include adequate lighting, ventilation, noise considerations,
work surface area, ESD (electrostatic discharge) protection, and adequate power availability. The recommended
environmental conditions are discussed below. With the exception of requirements imposed by the Naval
Environmental Health Center and other authorities for ship and shore work conditions, each activity tailors the
requirements to meet local needs.
LIGHTING The recommended lighting for a work surface is 100 footcandles from a direct
lighting source. Light- colored overheads and bulkheads and off-white or pastel workbench tops are used to
complement the lighting provided. VENTILATION Fumes from burning flux, coating
materials, grinding dust, and cleaning solvents require adequate ventilation. The use of toxic, flammable
substances, solvents, and coating compounds requires a duct system that vents gasses and vapors. This type of
system must be used to prevent contamination often
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found in closed ventilation systems. This need is particularly important aboard ship. Vented hoods, ducts, or
installations that are vented outside generally meet the minimum standards set by the Naval Environmental Health
Center.
NOIsE Considerations Noise in the work area during normal work periods must be no greater
than the acceptable level approved for each activity involved. Because the work is tedious and tiring, noise
levels should be as low as possible. Ear protectors are required to be worn when a noise level exceeds 85 dB. Ear
protectors should also be worn anytime the technician feels distracted by, or uncomfortable with, the noise level.
WORK SURFACE AREA Work stations should have a minimum work surface of at least 60-inches
wide and 30-inches deep. Standard Navy desks are excellent for this purpose. Standard shipboard workbenches are
acceptable; however, off-white or pastel-colored heat-resistant tops should be installed on the workbenches.
Chairs should be the type with backs and without arms. They should be comfortably padded and of the proper height
to match the work surface height. Drawers or other suitable tool storage areas are usually provided.
ELECTROSTATIC DIsCHARGE SENSITIVE DEVICE (ESDS) CAPABILITY A 2M work station should be capable of
becoming a static-free work station. This is specified in the Department of Defense Standard, Electrostatic
DIsCHARGE Control Program for Protection of Electrical and Electronic Parts, Assemblies, and Equipment. ESD will
be discussed in greater detail in topic 3. Power REQUIREMENTS No special power
source or equipment mounting is required. The 2M repair equipment operates on 115-volt, 60-hertz power. a
15-ampere circuit is sufficient and six individual power receptacles should be available.
High-RELIABILITY SOLDERING
The most common types of miniature and microminiature repair involve the removal and replacement of circuit
components. The key to these repairs is a firm knowledge of solder and high- reliability soldering techniques.
Solder is a metal alloy used to join two or more metals with a metallic bond. The bonding occurs when molten
solder dissolves a small amount of the metals and then cools to form a solid connection. The solder most commonly used in electronic assemblies is an alloy of tin and lead. Tin-lead alloys are identified by their percentage in
the solder; the tin content is given first. Solder marked 60/40 is an alloy of 60 percent tin and 40 percent lead.
The two most common alloys used in electronics are 60/40 and 63/37. The melting temperature of tin-lead
solder varies depending on the percentage of each metal. Lead melts at a temperature of 621 degrees Fahrenheit,
and tin melts at 450 degrees Fahrenheit. Combinations of the two metals melt into a liquid at different
temperatures. The 63/37 combination melts into a liquid at 361 degrees Fahrenheit. At this temperature, the alloy
changes from a solid directly to a liquid with no plastic or semiliquid state. An alloy with such a sharp changing
point is called a EUTECTIC ALLOY.
As the percentages of tin and lead are varied, the melting temperature increases. Alloy of 60/40 melts at 370
degrees Fahrenheit, and alloy of 70/30 melts at approximately 380 degrees Fahrenheit. Alloys,
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other than eutectic, go through a plastic or semiliquid state in their heating and cooling stages. Solder
joints that are disturbed (moved) during the plastic state will result in damaged connections. For this reason,
63/37 solder is the best alloy for electronic work. Solder with 60/40 alloy is also acceptable, but it goes into a
plastic state between 361 and 370 degrees Fahrenheit. When soldering joints with 60/40 alloy, you must exercise
extreme care to prevent movement of the component during cooling. USE of Flux IN SOLDER BONDING
Reliable solder connections can only be accomplished with clean surfaces. Using solvents and abrasives to clean
the surfaces to be soldered is essential if you are to achieve good solder connections. In almost all cases,
however, this cleaning process is insufficient because oxides form rapidly on heated metal surfaces. The rapid
formation of oxides creates a nonmetallic film that prevents solder from contacting the metal. Good metal-to-metal
contact must be obtained before good soldering joints may take place. Flux removes these surface oxides from
metals to be soldered and keeps them removed during the soldering operation. Flux chemically breaks down surface
oxides and causes the oxide film to loosen and break free from the metals being soldered. Soldering fluxes
are divided into three classifications or groups: CHLORIDE Flux (commonly called ACID), ORGANIC Flux, and ROSIN
Flux. Each flux has characteristics specific to its own group. Chloride fluxes are the most active of the three
groups. They are effective on all common metals except aluminum and magnesium. Chloride fluxes, however, are NOT
suitable for electronic soldering because they are highly corrosive, electrically conductive, and are difficult to
remove from the soldered joint.
Organic fluxes are nearly as active as chloride fluxes, yet are less corrosive and easier to remove than chloride
fluxes. Also, these fluxes are NOT satisfactory for electronic soldering because they must be removed completely
to prevent corrosion. Rosin fluxes ARE ideally suited to electronic soldering because of their molecular
structure. The most common flux used in electronic soldering is a solution of pure rosin dissolved in suitable
solvent. This solution works well with the tin- or solder-dipped metals commonly used for wires, lugs, and
connectors. While inert at normal temperatures, rosin fluxes break down and become highly active at soldering
temperatures. In addition, rosin is nonconductive. Most electronic solder, in wire form, is made with one
or more cores of rosin flux. When the joint or connection is heated and the wire solder is applied to the joint
(not the iron), the flux flows onto the surface of the joint and removes the oxide. This process aids the wetting
action of the solder. With enough heat the solder flows and replaces the flux. Insufficient heat results in a poor
connection because the solder does not replace the flux. Q10. Stereoscopic-zoom microscopes
and precision drill presses are normally associated with what type of repair station? Q11.
Solder used in electronic repair is normally an alloy of what two elements? Q12. In soldering,
what alloy changes directly from a solid state to a liquid state? Q13. Flux aids in soldering
by removing what from surfaces to be soldered? Q14. What type(s) of flux should never be used
on electronic equipment?
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Summary
This topic has presented information on the Miniature and Microminiature 2M Repair Program and high-reliability
soldering. The information that follows summarizes the important points of this topic. The
MINIATURE/MICROMINIATURE (2M) REPAIR PROGRAM provides training, tools and equipment, and certification
for 2M repair personnel.
CERTIFICATION of technicians ensures the capability of high-quality, high-reliability repairs.
The three SM&R codes for maintenance of electronic devices are: DEPOT (D), INTERMEDIATE
(I), and ORGANIZATIONAL (O). SM&R Code D Maintenance is
characterized by extensive facilities and highly trained personnel. Code D activities are capable of the most
complex type repairs.
Code I activities provide direct support for user activities. This includes calibration, repair,
and emergency manufacture of nonavailable parts. Code O maintenance is the responsibility
of the user activity. It includes preventive maintenance and minor repairs. ON-LINE Test Equipment
continuously monitors system performance and isolates faults to removable assemblies. ofF-LINE
Test Equipment evaluates removable assemblies outside of the equipment and isolates faults to the
component level. FAULT IsOLATION USING GENERAL-PURPOSE ELECTRONIC Test Equipment (GPETE)
should only be attempted by experienced technicians. 2M REPAIR STATIONS are equipped
according to the level of repairs to be accomplished. ALLOYS, such as solder, which
change directly from a solid state to a liquid are called eutectic alloys. SOLDER with a
tin/lead ratio of 63/37 is preferred for electronic work. a ratio of 60/40 is also acceptable.
ROSIN
or RESIN FluxES are the only fluxes to be used in electronic work.
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Answers to Questions Q1. Through Q14.
A1. Chief of Naval Operations (CNO). A2. Naval Sea Systems Command
(NAVSEASYSCOM) and Naval Air Systems Command (NAVAIRSYSCOM). A3. Microminiature component
repair.
A4. Microminiature repair technician. A5. Depot, Intermediate, and
Organizational.
A6. Organizational.
A7. On-line, off-line, and General Purpose Electronic Test Equipment (GPETE). A8.
On-line.
A9. Off-line. A10. Microminiature repair station. A11. Tin
and lead. A12. Eutectic. A13. Oxides. A14. Chloride or
(acid) and organic.
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- |
Matter, Energy,
and Direct Current |
- |
Alternating Current and Transformers |
- |
Circuit Protection, Control, and Measurement |
- |
Electrical Conductors, Wiring Techniques,
and Schematic Reading |
- |
Generators and Motors |
- |
Electronic Emission, Tubes, and Power Supplies |
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Solid-State Devices and Power Supplies |
- |
Amplifiers |
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Wave-Generation and Wave-Shaping Circuits |
- |
Wave Propagation, Transmission Lines, and
Antennas |
- |
Microwave Principles |
- |
Modulation Principles |
- |
Introduction to Number Systems and Logic Circuits |
- |
- Introduction to Microelectronics |
- |
Principles of Synchros, Servos, and Gyros |
- |
Introduction to Test Equipment |
- |
Radio-Frequency Communications Principles |
- |
Radar Principles |
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The Technician's Handbook, Master Glossary |
- |
Test Methods and Practices |
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Introduction to Digital Computers |
- |
Magnetic Recording |
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Introduction to Fiber Optics |
Note: Navy Electricity and Electronics Training
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