- If you've been following High Performance Academy for any amount of time,
you've probably heard us talk about solder versus crimping and this always ends up
in a bit of a heated debate in the comments with inevitably a bunch of people saying
that 10 or 15 years ago they soldered a wire one time on their car and it didn't fall apart
so obviously soldering's fine.
Fair enough, we're not here to say that soldering is instantly going to result in a
failure of your wiring, however no matter how you want to spin it and no matter how
good your soldering technique is, can't get away from the fact that it does bring about
a potential failure point.
And particularly with motorsport wiring where we're trying to improve the reliability,
sometimes on some very expensive equipment, we want to mitigate any risks we can which
is why we crimp over soldering.
Let's talk about the differences between the two and why soldering does have the potential
to be problematic.
First of all with a crimp, when we talk about crimping, most people will argue with us
in the comments that they once crimped a wire and it pulled out of the crimp so
obviously crimping isn't any good.
Again fair enough but we're not talking about using cheap crimp tools, we're talking
about using the proper materials, the proper consumables, the correct crimp
tooling as well as the correct technique for applying those crimp tools.
When we do this, we end up with essentially a cold weld inside of the crimp which is
stronger than the parent conductors.
What I mean here is that if we apply enough force to that completed crimp, the actual
individual conductor strands will break before they pull out of a crimp.
So that's the first thing, we want to make sure that if we are going to be crimping,
we're using the right tools and the right techniques,
When we do this properly, the crimp is going to be incredibly strong.
This is also why you'll see OE manufacturers essentially only use crimping.
Now on the other hand, with a soldered joint, what happens is that when we apply heat
and we apply solder to our wires, the solder will wick up the wires.
It's unavoidable no matter how good our technique is.
The more solder we apply and the more heat we apply, the worse this gets.
And the situation where we end up with a potential problem or a potential weak
point is where the wicked solder finishes.
Now if we apply enough vibration or movement to that particular point, it can end up with the
wires, the conductor strands actually fracturing over time.
Now again, this doesn't necessarily mean it's going to happen straight away, it might not
happen at all.
There are definitely techniques we can apply that are going to reduce the chances
of that failure.
Strain relief, supporting the wiring harness properly so that it is not going to be
subjected to any bending, that's all going to help.
No matter what we do though, we can't get away from the fact that we do bring
about the potential for a failure point there.
Alright so for every rule though, there's also an exception and I wanted to talk about a
couple of those now.
When we are building motorsport wiring harnesses, often the factory connectors that
we're using aren't that reliable.
They may fail over time, they may result in intermittent connection between the
terminals and the actuator or sensor that we're connecting to and this is understandably
a problem so a technique that's quite common is what's referred to as potting.
Here, we use, wait for it, solder.
What we're going to do is cut down the connector body on the actuator or the
sensor that we're using to give good exposure to the terminals inside.
We're then going to strip some insulation off our wire, we're going to basically bend that
wire around so it's going to sit around the terminal and then we're going to lightly
solder that directly to the terminal on the sensor or actuator.
Now straight away I know what you're thinking, well you just told us that this doesn't work
so how and why would we do this?
Wait, there is a reason that we can get away with this and again it all comes down
to preventing the relative movement of those wires once we've soldered them.
And there's two ways we do this when we are potting an actuator or a sensor.
First of all, once the solder has been applied we're going to then pot that connector with
an epoxy.
This two pot epoxy, basically once it cures, it's completely solid so this will generally
cover the area where that solder is wicked up the wire, meaning that there is absolutely
no chance of the connector or wires moving so that's going to strain relieve the wires
and prevent and potential failure.
We then go step further and we'll apply a heat moulded boot over the finished
connector and this will support that wire even further away from the actuator,
again meaning that there is no chance of movement.
We end up with a very reliable connection to our sensor or actuator.
From here we can then terminate the flying lead in something a little bit more reliable,
maybe a DTM style connector.
If budget's no problem then maybe an autosport connector.
This does present one problem to the teams though, obviously we can't then
just swap in a new coil, a new sensor in place of that one that we've potted so
everything that we pot on the engine, all of the sensors and actuators,
we also need to pot spares and have these at the track when we're racing the car.
Another area where we really can't get away from using solder is using some
specific connectors that we may come across.
AA couple of examples of these would be the D9 serial style connector or the XLR connector.
And these use solder cups on the back of them so we need to actually solder the wires
into those little solder cups.
Again, mitigating the potential problems is the key here and again we're going to
probably here be potting the connector once it's complete and using a heat moulded boot
to support the wiring so that it can't move.
It's not an idea connector but sometimes we have no option and it's all about using the
techniques in our arsenal to make sure we end up with the best reliability possible.
Another area where we actually choose to use solder is when we're terminating the
likes of a shielded cable.
Let's have a look at one of these shielded cables.
This is an example of what I'm talking about here, this is a two core shielded cable and
we'll quite often use this style of cable for some of our mission critical sensors.
You can see there are two conductor strands and then this section here is a braided shield.
The idea with the shielded cable is that the shield is there to essentially absorb
electromagnetic interference and prevent that from getting into the conductors.
We're going to be using these for the likes of our engine speed and position sensors,
knock sensors etc and any noise or interference that makes its way into the
conductors can actually play havoc with the operation of the ECU and the way our engine
runs so the idea is that the shield absorbs the electromagnetic interference and then it's
earthed at the ECU end, it drains all of that electromagnetic interference straight
to ground, protecting the underlying conductors.
However, this brings us to the tricky part where we need to actually terminate that
braid so that we can pin it out to our ECU header plug and this is where we use a
product called a solder sleeve.
This is a solder sleeve here, these are available in a variety of different sizes and what you
can see is there's two blue bands on that solder sleeve and a red one.
This is a heat recoverable part meaning that we're going to shrink this onto our shielded
braid using our heat gun.
the red band in the middle is a small band of solder that's applied to the inside
of that product and essentially when we heat it up with our heat gun, that solder band will
melt and it will run out and it's going to contact to our shielded braid and we're
also going to add another conductor into the setup before we shrink it down.
So the stripped insulation here, the conductor strands, this is going to be applied so that it
connects to our solder band as well as our shielded braid.
The reason that the solder sleeve is used here and the reason that it is effective and
reliable is twofold.
First of all, when the solder sleeve is recovered, it becomes essentially rigid, this provides
strain relief to the finished solder joint so there's going to be no relative movement
and our finished solder joint is going to be inherently reliable.
The other aspect with this as well though is that it has a carefully controlled amount of
solder applied inside that solder sleeve so this prevents the solder wicking up our
wire excessively.
Finished result, very easy to use, we have a nice drain wire that's going to be easy to
terminate into our ECU plug and a reliable finished solder joint.
Now that might not be the only instances where solder is unavoidable but again,
essentially where possible we're going to crimp instead of using solder, where we do
have to use solder, it's important to mitigate the potential downsides and risks that
solder inherently will give us.
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