Molex K and Amp (TE) MTA Connector Page
Resolving confusions about using these very common connectors
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I use a lot of Molex KK .1" and .156" connectors. They are cheap, flexible and reliable. Cables can be hand-built with low cost tools. However there are several traps involved w  ith these seemingly simple connectors.  There is no published 'standard' for pin 1, Amp and Molex are almost but not quite compatible with each other. there are gold and tin plating, which to use? Should you use straight or right angle? Should you use crimp-and-poke or IDC connectors? And how do you lay out PC boards for them?


I recently switched from ExpressPCB to DipTrace as my PCB layout tool of choice.  ExpressPCB has common connector footprints, but not a large selection. They do however have nice footprints for every size and style of Molex KK connectors. I just used them, built lots of boards, built lots of cables, and everything worked out well. I also assumed that any other CAD tool would have these common connectors. But DipTrace has no Molex KK footprints or anything looking like them. So I drew them and made them look like the ExpressPCB footprints.

Then at my day job, we began using Molex KKs with Altium Designer. And the boards came in backwards from the cables! When I questioned the engineer who designed the board and footprints, he pointed to the Molex drawings with pin 1 on the left end. I pointed to the Molex housing drawings with pin 1 on the right. For a common part like this to have such a trap for designers is pretty awful.

So where the hell is pin 1?

Molex puts Pin 1 of the male header and pin one of the female housing at opposite ends! What were they thinking?? Amp (aka Tyco, TE...) avoids the issue by not specifying Pin 1 on the male header. But a connector is pretty useless without knowing where pin 1 is!  Additional confusion is provided by not marking the male header with a pin 1 indication. Come on guys!!

I, like most, use the housing standard. Of course, this confuses the PC layout guys. But they only get confused once. Better that than confusing the cable manufacturer forever, every time they build a cable. If you look at DC Fan connectors which often use the 2 or 3 pin KKs, they use the housing convention.

Other Differences between Amp and Molex.

The ramps, keys and overall dimensions are ever so slightly different from Amp to Molex. But Amp females plug into Molex Males and vice-versa. However, do not try to use Molex pins in Amp housings or vice-versa. They are quite different even if you can get the pint into the housings, will not be reliable.

My suggestion is to pick one manufacturer and try to stick with them. That way you only need one type of pins and housings. I chose Molex KK a while back and have no regrets. If you must stock and use both, keep the female housings and pins separate so you won't accidentally mix them

Ramps, keying, etc.

I use only male headers with the keying feature. Life its too short to spend time figuring out how to plug in a cable, or dealing with the smoke and damage caused by plugging in a cable incorrectly. There is only one correct way to plug in a cable, but there are lots of incorrect ways: off by 1, reversed, wrong plug,  The keying feature is there to prevent all of these. It has the other advantage of preventing you from plugging a 5 pin female into the 6 pin housing. True, you can plug the 6 pin cable into the 5 pin male if you're not careful, but then when you go to plug in the 5 pin cable to the 6 pin male,  you will see the error of your ways. Hopefully before you power up the system and damage something.

I generally try not to have two different connectors of the same size in a system. If you must have multiple identical cables that use the same connectors, label both the PCBs and the cables clearly. And make sure your system will not be damaged when you reverse them. You will plug them in wrong, but will eventually learn, the hard way, to match the labels. Murphy says if someone can build it wrong, they will, and at the worst possible time and with the most expensive possible consequences.
The females come with or without the ramps, and with or without the keying features. I use only ramps and keys. They look like this:

Right angle or straight?

Seems like a simple question, no? With a right angle connector, it is obvious how to mount the connector to the board. The connector pins stick off the edge of the board. However the straight header can be installed with the tab at the board edge or the opposite way. My strong suggestion it to always put the tab away from the board edge. That way if you ever need to change to a right angle type, no problem. Otherwise you will need to re-lay out your board to use a right angle. Now the right angle holes should be mounted about 0.1" inward of the edge vs. the straight, to allow the housing to sit on the board edge. But they can be used in a pinch, they will just stick out a bit more. Here is an ExpressPCB  board snippet with vertical headers aligned correctly. Note that the footprint has the tab clearly marked and away from the edge of the board, and pin 1 (square pad) on the right side.


Note that if you use a right angle connector, the tab is on the top, which corresponds to the tab on the vertical header located away from the board edge. Ideally it uses a different footprint.

Cables and crimp tools

The proper ratcheting crimp tool from either Amp (TE) or Molex will run you several hundred dollars. I use an old Radio Shack hand crimp tool (276-1595, $20) with good success. It works on most medium sized pins for KK, MTA and DSUB connectors as well as most other .1" connectors. It is fine for making a few cables. If you are making dozens of cables, get a ratcheting tool, and your hand will thank you. There are low cost ratcheting tools available. If anyone knows a good cheap one, can you post your experience in the blog?

Tin or Gold?

I design critical medical equipment and expensive instruments. My general guideline is to use all gold plated connectors. These resist corrosion, are more reliable, and allow more insertion cycles. But gold connectors are more expensive than Tin. For example, Digikey (q100) pricing for Molex KK 5 pin gold is $0.40 and Tin is $0.18. The crimp pins are also more expensive in gold. So if your application calls for low cost over high reliability, use Tin.

How about mixing tin and gold?  Never mix tin pins and and gold connectors or vice-versa. In general, dissimilar metals cause corrosion due to electrolysis, and low reliability. This is particularly true with gold and tTIn. Decide whether quality or cost is more important on a given project, and stick with either gold or tin.

Crimp-and-Poke or IDC?

Sorry, but there are still more choices. Both Amp and Molex make Crimp-and-poke connectors. But Amp also makes IDC connectors. Some people swear by the IDC types. You simply push the wire onto the back of the connector with a low cost tool called a T-Handle. No tiny pins to handle, no poking needed. However you will need to decide wire size and use only one wire size for all your connections. The color of the connector corresponds to its wire size.
With Crimp-and-poke, pins can be used with a range of wire sizes. I generally use 26AWG for signals, and 22AWG for power. One size pin can handle 26, 24, and 22AWG.
When you purchase the pins, there are yet more choices: gold or tin, wire size, single contact or high reliability, reel or loose.

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Last Updated: 6/14/2016