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

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As you can see, the flat-set eyelet actually provides reinforcement for the pads on both sides of thecircuit board <strong>and</strong> reinforces the hole itself. The design of the roll-set eyelet (which may trap gasses, flux,or other contaminants, <strong>and</strong> obscures view of the finished solder flow) is not acceptable as a repairtechnique. The funnel-set eyelet does not provide as much pad reinforcement as the other types. However,it provides better "outgassing" of flux, moisture, or solvents from the space between the eyelet <strong>and</strong> thehole wall. It also provides a better view of the finished solder connection than the roll-set eyelet.Lead TerminationsThe finished circuit board consists of conductive paths, pads, <strong>and</strong> drilled holes with components<strong>and</strong>/or wires assembled directly to it. Leads <strong>and</strong> wires may terminate in three ways: (1) through the holein the board, (2) above the surface of the board, or (3) on the surface of the board.THROUGH-HOLE TERMINATION.—This style provides extra support for the circuit pads, thehole, <strong>and</strong> the lead by a continuous solder connection from one side of the circuit board to the other. Threebasic variations of through-hole termination are the CLINCHED LEAD (two types), STRAIGHT-THROUGH LEAD, <strong>and</strong> OFFSET PAD.Clinched Lead.—The clinched-lead termination is usually used with unsupported holes, but is foundwith supported holes as well. Both clinched-lead types, FULLY CLINCHED <strong>and</strong> SEMICLINCHED(figure 3-5), provide component stability. Like the fully clinched lead, the semi-clinched lead alsoprovides stability during assembly. However, this termination can be easily straightened to allow removalof the solder joint should rework or repair be required. Note that the fully clinched lead is bent 90 degreeswhile the semiclinched lead is bent 45 degrees.Figure 3-5A.—Clinched leads. FULLY CLINCHED.3-9

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