3-25
Figure 3-17.—Preferred solder joint.
When a solder joint is completed, solvent must be used to remove all flux residue. The two most
highly recommended solvents, in the order of their effectiveness, are 99.5 percent pure ethyl alcohol and
99.5 percent pure isopropyl alcohol.
Q19. What is solderability?
Q20. What is the most common source of heat in electronic soldering?
Q21. What determines the shape and size of a soldering iron tip?
Q22. What term describes a device used to conduct heat away from a component?
Q23. What is the appearance of a properly soldered joint?
REMOVAL AND REPLACEMENT OF DIPS
In topic 1 you learned the advantages of DIPs. They are easily inserted by hand or machine and
require no special spreaders, spacers, insulators, or lead-forming tools. Standard hand tools and soldering
equipment can be used to remove and replace DIPS.
DIPs may be mounted on a board in two ways: (1) They may be mounted by plugging them into DIP
mounting sockets that are soldered to the printed circuit boards or (2) they are soldered in place and may
or may not be conformally coated. Although plug-ins are very easy to service, they lack the reliability of
soldered-in units, do not meet MILSPECS, and are seldom used in military designed equipment. They are
susceptible to loosening because of vibration and to poor electrical contact because of dust and dirt and
corrosion.
