REPAIR STATIONS

In addition to the requirements for special skills, the repair of 2M electronic circuits also requires special tools. Because these tools are delicate and expensive, they are distributed only to trained and certified 2M repair technicians.

2M repair stations are equipped with electrical and mechanical units, tools, and general repair materials. Such equipments are needed to make reliable repairs to miniature and microminiature component circuit boards.

Although most of the tools and equipments are common to both miniature and microminiature repair stations, several pieces of equipment are used solely with microminiature repair. Precision drill presses and stereoscopic-zoom microscopes are examples of microminiature repair equipment normally not found in a miniature repair station. A brief description of some of the tools and equipments and their uses will broaden your knowledge and understanding of 2M repair.

The 2M repair set consists of special electrical units, tools, and materials necessary to make high-reliability repairs to component circuitry. The basic repair set is made up of a repair station power unit, magnifier/light system, card holder, a high-intensity light, a Pana Vise, and a tool chest with specialized tools and materials. As mentioned previously, stations that have microminiature repair capabilities will include a stereoscopic-zoom microscope and precision drill press.

REPAIR STATION POWER UNIT

The repair station power unit is a standardized system that provides controlled soldering and desoldering of all types of solder joint configurations. The unit is shown in figure 2-1. Included in the control unit's capabilities are:

Figure 2-1. - Repair station power unit.

"Spike free" power switching for attached electrical hand tools to eliminate damage to electrostatic discharge components. Abrading, milling, drilling, grinding, and cutting using a flexible shaft, rotary-drive machine. This allows the technician to remove conformal coatings, oxides, eyelets, rivets, damaged board material, and damaged platings from assemblies. Lap flow solder connections and thermal removal of conformal coatings. Resistive and conductive tweezer heating for connector soldering applications. Thermal wire stripping for removing polyvinyl chloride (PVC) and other synethetic wire coverings.

Power Source

The basic unit houses the power supply, power level indicator, motor control switch, hand tool temperature controls, air pressure and vacuum controls with quick connect fittings, positive ground terminal, the mechanical power-drive for the rotary-drive machine, and a vacuum/pressure pump. A two-position foot pedal, to the left of the power unit in the illustration, allows hand-free operation for all ancillary (additional) handpieces. The first detent on the pedal provides power to the voltage heating outputs. The second detent activates the motor drive or vacuum/pressure pump.

Handpieces

The handpieces used with the power unit are shown in figures 2-2 and 2-3. The lap flow handpiece, view (A) of figure 2-2, is used with the variable low-voltage power source. This handpiece allows removal of conformal coatings, release of sweat joints, and lap flow soldering capability. (Lap flow soldering will be discussed in topic 3.) The thermal wire stripper in view (B) is used to remove insulation from various sizes of wire easily and cleanly.

Figure 2-2. - Low voltage Handpiece.

Figure 2-3. - Motorized solder extrator.

The resistive tweezers, shown in view (C), are used for soldering components. Two sizes [views (C) and (D)] are provided to meet the needs of the technician. Both the thermal stripper and the resistive tweezers are used with the low-voltage power supply.

The solder extractor, shown in view (A) of figure 2-3, is connected to the variable high-voltage outlet. This handpiece allows airflow application (at controlled temperatures) of a vacuum or pressure to the selected area. Five sizes of extractor tips are provided, as shown in view (B). You can determine the one to be used by matching the tip with the circuit pad and the component being desoldered.

Soldering Irons

A soldering iron is shown in figure 2-4. This is connected to the 115-volt ac variable outlet of the power unit. You control the temperature by adjusting the voltage. The iron has replaceable tips. Chosen for their long life and good heat conductivity, soldering iron tips are high quality with iron-clad over copper construction. The tip shape and size and the heat range used are determined by the area and mass to be soldered.

Figure 2-4. - Soldering iron.

ROTARY-DRIVE MACHINE

This variable-speed, rotary power drive adapts to standard diameter shank drill bits, ball mills, wheels, disks, brushes, and mandrels for most drilling and abrasive removal techniques (figure 2-5).

Figure 2-5. - Rotary-drive machine handpieces.

The accessories used with the rotary-drive tool are shown in views (A) through (F) of figure 2-6. Abrasive ball mills, wheels, discs, and brushes are either premounted on mandrels or can be mounted by the technician on the mandrels provided. These attachments are used for sanding and smoothing repaired areas, drilling holes, removing conformal coatings, and repairing burned or damaged areas. A chuck-equipped handpiece allows it to accept rotary tools with varying shank sizes.

Figure 2-6. - Rotary-drive machine accessories. BALL MILLS

CIRCUIT CARD HOLDER AND MAGNIFIER

The circuit card holder is an adjustable, rotatable holder for virtually any size circuit card. Figure 2-7 shows the circuit card holder [view (A)] and the magnifier unit [view (B)]. The magnifier unit provides magnification when detail provided by a microscope is not required. The special lens allows the technician to view a rectangular area of over 14 square inches with low distortion, fine resolution, and excellent depth of field. The magnifier unit, which includes high intensity lamps, adapts to the vertical shaft of the circuit card holder.

Figure 2-7. - Card holder and magnifier.