USB Type-C Connectors

It wasn’t terribly long ago that pretty much every cellphone came with its own custom charging cable. It was a major step forward when they all (except Apple) standardized on the USB micro-B connector.

However, there are a number of limitations with the. First, it takes a minimum of three attempts to get the orientation right when trying to plug in a cable. Second, it’s limited in maximum current carrying capacity.

Now, along comes the USB 3.1 Type-C cable and connector. It’s similar in size, universally polarized (the connector and the cable can be plugged in any end to any end and in any orientation), it has much higher data throughput, and it’s spec’d to carry up to 3A. Further, it has alternate modes for other standards, such as DisplayPort and Thunderbolt.

The connectors are larger than the micro-B, as you can see in Figure 1, micro-B, Type-C with only surface mount connections, and Type-C with both surface mount and through-hole wiring, and a US dime. The size difference won’t be an issue in most cases, but it could be in really small devices. My guess is that we’ll be talking about a smaller, Type-D connector, not long from now.

Figure 1. Micro-B, Type-C with only surface mount connections, and Type-C with both surface mount and through-hole wiring, and a US dime. Figure 2. Micro-B connector with tabs formed from the same sheet metal as the shell.

All three of the surface mount connectors shown above have through-hole mounting tabs. That adds strength, but it does bring one caution with it. Looking at the micro-B connector in the image on the right, you can see that the tabs are formed out of the same sheet metal as the shell.

You can also see that the tabs don’t stick all the way through the PCB. This can lead to some deception when soldering. Without the tabs protruding, it’s easy to believe there’s not enough solder in the connection. If more solder is fed in, it will likely wick along the tab, and end up inside the receptacle, preventing the cable from being plugged in. If hand soldering or reworking these type of connectors, keep a close watch on the amount of solder used.

Duane Benson
Fester Bester Tester is alive and well and living where?

Connectors Kill

Lots of types of components can cause footprint woes. QFNs have their center pad issues. BGAs have escape via issues. But the most common footprint issues seem to be with connectors. At least with chips Connector footprint 2smand discrete silicon and passive components most manufacturers pretty much follow IPC standard footprints. Sometimes they’ll create new ones for smaller parts, but generally they still stay reasonably close to in line.

Connector footprint 1smConnectors are another story, though. I’m not sure any manufacturer follows anything close to a standard. This pair of Ethernet jacks is a good example. Often the actual pin layout will match, but the mounting will vary widely. I’ve seen it on Ethernet, mini-USB, micro-USB and even the old, old RS232 connector.

It gets more frustrating when they’re almost the same. We see that a lot; the layout will almost, but not quite match a footprint in the library. The bottom line is never take a connector footprint for granted. Always double check before getting your boards fabbed.

Duane Benson
Carburetors man. That’s what life is all about.