DVD-60C The Seven Sins of Wire Harness Assembly - IPC Training ...

DVD-60C Script
Pierced terminals have a hole in the middle. Wire can enter from either side, or from the top. The
wire should be pushed through the hole, then wrapped and positioned to contact both the flat
sides of the terminal. Make sure you set the soldering iron temperature based on the guidelines
set by the solder manufacturer.
Now, let's watch the proper soldering operation for this particular terminal. There are four basic
steps. First -- the iron is placed at the point of greatest thermal mass – in contact with the
terminal and the wire. Next – a solder heat bridge is made to increase the thermal linkage
between the tip and the work. Additional solder is then applied on the opposite side of the point
of contact to form the necessary solder fillet. The solder wire is removed when a sufficient
amount of solder has been added to the joint. Finally, the iron is withdrawn from the same angle
it was introduced to the joint. Let’s watch this correct soldering technique once more – in real
time.
It’s very important to clean the joint after the soldering is complete -- using an appropriate
cleaning solution. Flux should not remain on the mating surfaces.
A preferred or target connection is where all of the metals are covered by solder – and the outline
of the lead remains visible within the solder connection. On a proper solder joint, the solder fillet
is slightly concave, or curved inward.
Sin number 6 – Missing or Incorrect Hardware
When you’re working quickly – trying to meet production deadlines – it’s easy to overlook a wire
that needs termination hardware, or to attach the incorrect hardware to a wire. That’s why it’s
important to take the time to double check the information in the assembly documentation.
Verifying your work will save time in the long run – since there’ll be fewer rework situations.
Some assemblies require the addition of jackscrews, stand offs, clamps, washers or screws. If the
wrong hardware is installed, it may prevent the installation of the harness.
For instance, if the wrong screw thread size is used, it will not mate with the intended mating
hardware.
Sin number 7 – Improper Tying
Tying the wires is typically the last step in the wire harness assembly process. The two basic
parts of tying are the application of the tie wrap and the breakout of the wires.
The use of plastic tie wraps is a common method for bundling the wires. The ties maintain the
form of the harness, along with defining the location where the individual wires can be broken
out of the harness at their designated connection points.
Plastic tie wraps can be installed manually, or with a handgun. The ties are tightened around the
wires and the tail is cut off. The tie wrap gun should be set to the proper tightness. If the tie wrap
is too tight, the wires can be damaged. If it’s too loose, the tie won't hold the bundle securely.
Tie wrap locations are called out in the assembly documentation.
There are a number of alternative methods used to separate and secure the cable bundles. Among
them are spiral wrap, heat shrink tubing, conduit, loom and expandable sleeving. Adhesive heat
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