DVD-61C Splicing Wires - IPC Training Home Page

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DVD-61C TranscriptThe hook splice is considered defective if there are any sharp points or projections covered by theheat shrink tubing; if the conductor strands pierce the tubing; if the wire splice area is exposed; orif the tubing doesn’t overlap the wire insulation on both ends for a minimum of three wirediameters.The final soldered splice we’ll be explaining is the lap splice. The lap splice can be used to jointwo or more wires. The first step is to strip the wires. Each wire end should have the samelength of insulation removed so that they appear identical. Each wire end should be stripped aminimum of four wire diameters. Then we tin the stripped wires.Now, we place the heat shrink tubing onto the wire. At this point, we line up the wires. Theyshould be positioned so that the tinned lengths of wire overlap and are touching each other.Notice that the end of the first wire butts against the ends of the insulation of the second wire.If a flat surface is not available the wires may be secured in position with alligator clips or asimilar type clamp. When using alligator clips, consider placing a small folded piece of businesscard or a thick heat shrink between the clips and the wire insulation to avoid “teeth marks” in thewire.Now, we’ll be wrapping the positioned wires. Use a wire that is about equal in diameter to asingle strand of the wires being spliced. For example, if you’re splicing two 24 AWG wirestogether, a piece of solid 30 AWG wire would be a good choice.We recommend tinning the wrapping wire. Notice that we tin one end, then the other – and thenfold the wire to tin the middle part. If the wire has been tin plated, it’s important to clean itbefore wrapping. Try to minimize handling during the wrapping process so that oils from yourfingers don’t contaminate the wire and interfere with the soldering process.Now, we'll solder the connection. Add just enough solder so it can penetrate the splice area, butleave the outline of the strands visible. Notice that the completed solder connection may have aslightly convex fillet along the length of the connection, as long as the individual wire used tosecure the spliced wires is clearly visible in the solder.At this point, we clean the freshly soldered splice. Then we inspect it. An acceptable lap splice iswhere the solder is wetted to the wires and you can see the outline of the wire strands underneaththe solder.To complete the lap splice, we position heat shrink tubing over the spliced area. Then apply heatto shrink the tubing to a snug fit -- over the splice and the wire insulation.The lap splice is considered defective if there are any sharp points or projections covered by theheat shrink tubing; if the conductor strands pierce the tubing; if the wire splice area is exposed; orif the tubing doesn’t overlap the wire insulation on both ends for a minimum of three wirediameters.6
DVD-61C TranscriptNow that you know how to make the four types of soldered splices, let's take a look at anotheroption. This involves the use of a heat shrinkable solder device where a solder preform is insidethe heat shrink tubing. Stripped wires are purposefully NOT pre-tinned, per J-STD-001. Once thestripped wires to be spliced are inserted into the heat shrinkable solder device, external hot air isapplied and the solder preform achieves a molten state. Notice that the heat shrink tubing alsoshrinks into a snug fit over the splice and insulation, and in many devices a ring of glue meltsinside each end to hermetically seal the solder joint.Crimped SplicesNow, let’s turn our attention to crimping. Crimping is an alternate method of splicing wires.The advantage to crimping is that it's a quick and solderless technique for splicing wires.There are two types of crimped splices – a barrel splice and a double-sided splice. Based uponthe size of the wires to be spliced, we’ll select the proper terminal and crimping tool. Forcrimped splices to be reliable, it’s important to match the wire size, terminal and crimping tool.In terms of strip length, the copper conductor should be in the crimp zone, half way into the metalbarrel. The insulation should be just inside the funnel -- with no copper conductor exposed.Terminal manufacturers may also provide specific instructions regarding strip lengths.We’ll begin by making a barrel splice. The first step is to strip insulation from the ends of thewires to be spliced. Stripped wires are never tinned for crimping operations. Then we pre-loadthe terminal barrel into the crimper nest. The stripped wires are now positioned inside theterminal barrel. The wire insulation should be flush against the end of the barrel on both sides.The last step is to close the handles of the crimping tool to complete the crimp. Because of theratcheting mechanism – also referred to as a full cycle tool – these crimpers will not release untilthe crimper is fully closed.Now we’ll inspect the crimp. Notice that the wire insulation is flush against the barrel splice.The bare wire ends should also be flush with the barrel splice – and the bellmouth is evident.The bellmouth is the flare that's formed on the edge of the crimp and acts as a funnel for the wirestrands. This funnel reduces the possibility that a sharp edge on the terminal will cut or nick thewire strands.The crimp should be centered and properly formed in order to retain the wires. It’s important toverify that the barrel splice is not cracked and that the wires cannot be pulled out when applyingmoderate pressure.An acceptable barrel crimp can tolerate some variation from our target crimp. For example, therecan be some insulation gap – meaning the insulation doesn’t have to be exactly flush against thebarrel splice – as long it is within two wire diameters. The bare wire end can also be less thanflush, but is visible within the crimp indentation. In addition, the crimp can be slightly off center-- as long as it is properly formed.7
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