DVD-18C Soldering Terminals - IPC

Bifurcated Terminals
DVD-18C Transcript
Now let's take a look at bifurcated, or forked terminals. On these terminals, the wires can enter
from the side, the top, or the bottom. Side entry is commonly used when one or more wires are
connected. The recommended minimum wrap on a bifurcated terminal is 90 degrees. 180 degrees
is used when additional mechanical strength is desired, and when there is sufficient clearance
between adjacent terminals. When two or more wires are required, they should be wrapped to
alternating posts.
Let's watch the soldering operation for a side route installation of one wire. The pre-tinned wire
is laid across the terminals to determine the proper insulation clearance. A 180 degree wrap is
made using a pliers that won’t cause damage to the wire. The wire is now positioned and
trimmed so that it doesn't protrude more than one conductor diameter beyond the edge of the
terminal. We do this to make sure the conductor doesn’t violate electrical clearance and cause a
short circuit. The wire should be mounted at the bottom of the slot – between the terminal posts.
Now, place the solder wire in contact with the terminal base and the wrapped wire.
Next, a solder heat bridge is made. Remember, the purpose of the heat bridge is to transfer the
heat more quickly to the connection and to preheat both the wire and terminal so they are hot
enough to melt the solder. Then the solder is touched to the other side to form a proper solder
fillet. After the right amount of solder is melted, remove the solder wire – followed by the iron.
Let’s watch these steps once again – in real time.
The joint can now be cleaned – if required. The acceptable joint will have a concave fillet
between the wire and the terminal. It should be smooth, clean, and display evidence of wetting. It
is recommended that the wire should be in contact with all three terminal post surfaces. Here’s
another joint that has insufficient solder and may not have acceptable mechanical strength. Also,
notice that the wire is extending beyond the edge of the terminal more than one lead diameter –
which is not acceptable. This joint has excessive solder. The fillet bulges out and the outline of
the wire is covered by the excess solder.
In addition to side entry, wires may also enter from the top or bottom. For top entry of bifurcated
terminals, the tinned wire may be bent to double thickness – thereby contacting more surfaces for
a stronger connection. Once properly inserted, the wire is soldered. If the wire is too large for
double thickness, a filler wire is cut to length and added to fill the space. For bottom entry, the
wire is bent a minimum of 90 degrees from where it comes up through the hole. The wire should
then be trimmed so it doesn't protrude more than one wire diameter beyond the edge of the
terminal. Make sure the wire insulation does not enter the hollow terminal.
Hook Terminals
Next, we’ll look at hook terminals. Hook terminals are found primarily on hermetically sealed
relays. The wire wrap should be at least 180 degrees. Numerous tools can be used to make the
wrap for hook terminals as long as they don’t nick, scrape or leave impressions on the conductor.
One example that we’ll use here is round nosed pliers.
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