A few months ago, one of my daughters broke her arm (badly) when she fell off of a neighbor’s playset. As you may guess, my wife and I spent a fair amount of time in and out of the hospital, waiting for various reasons (x-ray, doctors, surgery, etc.). My daughter is fine- her arm is now stronger than ever, thanks to some great doctors and a little titanium. She had to get used to, though, using just her right arm (thankfully she is right-handed). It made me think, though, about how important an arm is, allowing our hands to do everything that we need them for in the course of a day. This got me thinking about connectors, and how useful connectors can be in attaching things.
We’ve all used these. Whether you need more real estate for components on a board, or you have to overcome mechanical packaging issues, you build a daughterboard or secondary board to stack onto your primary board. How do you connect it? Board to board connectors. These come in all shapes and sizes, and with all manner of electrical capabilities (good old fashioned 0.100” headers, shielded, high speed, power distribution, etc.).
[/span4]Figure 2: Various TE Connectivity Board to Board Connectors
Typically other hardware will be used, but these types of connectors are usually critical in locating a secondary or daughter printed circuit board. In many cases these might be very stressed, and in some cases, the ONLY mechanical link to the second board. That is rare but nonetheless, the mechanical function of this connector is as important or more important than the electrical one.
Many bulkhead connectors are just as mechanical as electrical. A good example of this is the J1772 charge connector for EVs. It serves as a physical holder/hanger for the heavy cables, and incorporates an easy-to-insert (and remove) pistol grip and button for release.
This bulkhead connector is typically mounted to the body of the vehicle, or in a recessed “cup” behind what looks like a fuel filler door. It is rigidly mounted to accept the abuse of being cycled up to several times daily. These cords are heavy, containing conductors that are 12, 10, or even larger gauge. These cables also tend to be trip hazards and get tugged on frequently. The jack and connector both have to handle an extreme amount of physical abuse. The electrical connection itself is not trivial, but its physical application is much, much more stringent than the electrical one.
Think of any RF test equipment you have used in the past. Whether it be long cables, heavy cables, or hanging various accessories from the bulkhead connector, they have to tolerate a lot. Various BNC, F, or N connectors take lots of abuse- whether it is frequent use, heavy cables, harsh environment… these bulkhead connectors are subject to quite a bit of mechanical torture but still remain in service and in spec for many, many years. Again, the electrical piece of this can’t be underestimated, but often takes a back seat to the physical component.
In many applications, board-to-wire connectors have to be very mechanically sound. Similar to bulkhead connectors, many applications are subject to harsh mechanical loads that require a robust physical connection. Take for example appliance and consumer electronic wiring:
A lot of appliance and consumer electronics manufacturers use the TE Mate-N-Lok connectors. Various manufacturers sell similar connector series. These are used in everything from washing machines to home PCs. While the primary function is not mechanical, they are subject to a lot of abuse. Vibration from small appliance motors, harsh environments, frequent maintenance activities (hard drive power connectors!) … there is quite a bit of mechanical stress applied to these connectors daily.
As electrical designers, it is easy to overlook sometimes the mechanical nature or requirements of a lot of what we design. What other connectors or items do you think we take for granted “mechanically?” Please share.