As you will probably tell from my user name, I have a particular interest in connectors of all kinds. Most of my career has been spent with manufacturers who specialise in high-reliability connectors of various configurations, and I have formed a number of opinions about connector design as a result. But I must confess that the new Mega-Fit connector series has made me re-think some of my ideas. I'll try to explain why.
When I received my first connector product training, I was told that machined contacts were good, and stamped contacts were... not so good. I am willing to admit that this idea has stuck and followed me ever since. But what's the difference? I could bore you for hours on the fine details of contact design (just ask my colleagues), but here's a quick summary...
Stamped contacts, sometimes known as "stamped and formed", are usually made from a single strip of metal that is cut, shaped and plated in a continuous process. They are ideally suited to mass production, and can take advantage of such clever ideas as selective plating (where the front and rear of a contact are plated in different metals). As a result they tend to be very cost effective, but there are disadvantages. They are hollow which means that they cannot carry too much current and they are not too durable. The life of a connector can be measured in mating cycles - the number of times a connector is plugged in and unplugged - and stamped and formed contacts are not intended for a long and active life.
In contrast, machined contacts are solid, reliable and can carry a high current. They are made one at a time, and often use quite sophisticated designs to ensure good electrical continuity and low resistance. They are often capable of a long life, with mating cycles measured in the thousands.
And so it was that I was indoctrinated into the ways of "high quality" machined contacts. The downsides were ignored - they are generally expensive, and sometimes not ideal for their chosen application. If you meet me, ask me to tell you the story of the customer who spent hours removing the gold plating from their incredibly expensive contacts so that solder would stick to them.
Okay, maybe this is a bit of a simplification, but I definitely spent many years assuming that if you need a high reliability, high power connector, it must have machined contacts. In recent years, however, I have been forced to re-evaluate my previous assumptions.
When it comes to multipole power connectors, one idea we can talk about is "power density". This is the measure of how much current can be carried through smaller connectors. In the never-ending quest for miniaturisation, engineers will be looking for higher and higher power density.
As far as I can see, the Molex Mega-Fit connector is one of the products that will lead the charge for higher power density. Molex have managed to design a contact that is turning my opinions upside down - this is a stamped and formed contact that can carry 23 Amps. Not only that, it is capable of over 200 mating cycles and it sits in the Mega-Fit connector on a 5.7mm pitch.
What does this mean? Well, it might be easier to illustrate this in pictures. The image at the top of the page shows a two-pole version of the Mega-Fit next to a 2p piece (which has a diameter of just under 26mm). An even more dramatic picture of the power density capability of the Mega-Fit range can be seen below.
The image uses the 3D models of the Mega-Fit range that are available on DesignSpark. Both of these are 10 pole connectors. As is normal for any multi-pole connector, the terminals have to be de-rated when so many are grouped together, but the current rating per circuit is still 16 Amps - meaning each of these connectors is capable of carrying 160 Amps. This counts as pretty impressive in my book!
This performance is quite remarkable, and it is all as a result of the clever contact. It is a very sophisticated design that has six points of contact to provide this fantastic current capacity. In fact, this gives the Mega-Fit connector a hot-plug capability - as long as your voltage is not too high, the connector can be plugged and unplugged with the power live!
I think it is rare to find this combination of features in any stamped contact, and in my opinion they make the Mega-Fit range a connector system that any engineer should consider very seriously. They have huge capability and offer fantastic value for money. I urge you to check them out.
The Molex Mega-Fit range is now available to buy from RS Components - click below to find out more.
In addition, all of the 3D models you need to incorporate the Mega-Fit range into your products are available from DesignSpark. Click below to see the connectors and download the models in 31 different formats!