DVD-61C Splicing Wires - IPC Training Home Page

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DVD-61C TranscriptIt takes some practice to properly strip wire using these types of tools. There are some hand toolsand methods – such as the use of Exacto knives, razor blades and wire cutters – that are definitelynot acceptable for mechanical stripping.Another effective tool for manually stripping insulation is a thermal stripper. After the thermalstripper melts or softens the insulation, you can use your fingers to twist off the insulation slug inthe direction of the wire lay. Most thermal strippers are adjustable. Always use the lowest heatsetting to minimize damage to the insulation or wire. Do not remove the insulation slug with thethermal strippers. Using the tool to pull off the insulation slug can potentially damage thearrangement or lay of the wire strands – and the stripper blades.The advantage of thermal strippers is that they never nick or scrape the wire. When usedproperly, thermal strippers produce a perfect strip every time. The main disadvantage of thermalstrippers is that some insulation, such as PVC, will burn and release hazardous gasses whenmelted. If you’re not sure which types of insulation are appropriate for thermal stripping, be sureto ask your supervisor.Sometimes the conductor strands will have a slight discoloration from thermal stripping. Thiscondition may be acceptable – per IPC standards. It’s not acceptable when the insulation isburned or charred; or if the insulation is ragged; or if there’s not a clean cut.Now, we’ll take a look at strip criteria. The preferred strip is when there is no visible damage tothe conductor strands or the insulation. It’s important that the original lay of conductor strands berestored -- whenever it is disturbed by stripping. That’s because wire separation, or birdcagingcan change the diameter of the wire.A strip may be rejected if there’s any damage to the conductor. When there are nicks or cutstrands on the conductor, it indicates that an improper technique has been used. Depending onwhere the wire is used and the amount of damage, it may be acceptable for a wire to have one ormore nicked or broken strands. The IPC A-610, J-STD-001, and 620 documents provideacceptance criteria for the maximum allowable nicked or broken strands -- based on the totalnumber of strands in the wire.For wires that are going to be soldered, there is typically a final wire preparation step. Thesewires will need to be tinned. Tinning ensures that when the wire is bent -- it won’t be damaged.It also prevents birdcaging and improves solderability.There are several ways to tin a wire. We can move the wire across a soldering iron tip -- coatedwith solder; or move the tip of a soldering iron that is coated with solder over a stationary wire; ordip the wire in a solder pot.The majority of the wires that you’ll be splicing will be in the cabinets of an existing chassis ofelectronic equipment. This equipment typically contains circuit board assemblies and othersensitive electronic devices. One of the biggest causes of electronic failure -- when makingcircuit repairs – is electrostatic discharge, or ESD. ESD occurs when static electricity from yourbody is discharged into an electronic component. This electricity can degrade or destroy thefunctionality of certain types of components.2
DVD-61C TranscriptThere are a wide variety of materials and techniques to eliminate the build up and discharge ofstatic electricity. Refer to IPC-DVD-54C for detailed information on ESD Control. The generalprinciples of ESD prevention however, are easy to remember. Always be sure that your body,your workplace and the workpiece are at the same electrical potential – by properly grounding theworkstation. These grounding wires will capture any built up electrical charges and conduct themharmlessly into the ground. It’s also important to make sure that your wrist straps and shoegrounders are operating properly -- by testing them often.Unfortunately, we don’t always have the luxury of this degree of ESD protection. We can’talways be at an ESD safe technician's bench – especially when we’re working in the field. Forthese situations, it’s important to utilize a portable ESD field service kit. The kit typicallyconsists of several connection points for wrist straps; a grounding wire that is usually connectedby an alligator clip to an unpainted metal grounding point inside the equipment chassis; and astatic dissipative work surface that allows an ESD safe resting place for sensitive components andcircuit boards.The last topic in this introductory section is safety. Enclosure panels and other metal hardwaremay have sharp edges or burrs. You’ll need to take care when handling this equipment. Also,keep in mind that all the hand tools you’ll be using have the potential to injure you – if they areused improperly.Soldered SplicesNow, let’s examine soldered splices. There are four different types of soldered splices. Theseare mesh, wrap, hook and lap. There is no one best splice. Each type of splice has advantagesand disadvantages. Factors that need to be considered include available slack, requiredclearances, and required strength.For example, if you are making a repair inside a chassis or assembly, you don’t always have theluxury of lots of slack or extra wire to work with. In addition, you may have to pull thecompleted splice through a small panel opening. Under these conditions, you would need tomake a small profile splice -- since a larger profile splice would not fit through the opening.Other considerations in determining what splice to use include your company’s standards,customer requirements and the purpose of the splice.It’s important to never work on live or powered up equipment when performing splicing or otherelectronic repairs. Always follow proper lock-out tag-out procedures. It’s a good idea to test thewires inside the existing chassis with a voltmeter to verify they are not “live.” And make sureyou’re wearing ESD grounding equipment.Let’s start by examining the mesh splice. A meshed splice is one where the strands of wireinterlace, or interconnect evenly and are of equal length. These splices use the least amount ofwire.3
Page 4 and 5: DVD-61C TranscriptThe first step is
Page 6 and 7: DVD-61C TranscriptThe hook splice i
Page 8 and 9: DVD-61C TranscriptThe barrel crimp

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