Why Keyssa Built a Better Connector: Part 3 – Mechanical Tolerances

By Alan Bessel
Mechanical Engineer, Keyssa

By design, the mechanical connector requires very tight tolerances. And faster signals require even tighter tolerances.

As an example, compare the mechanical tolerances of a Type-A plug width, to that of a Type-C. The Type-A can get away with ±0.10 mm whereas the Type-C spec requires a tolerance of ±0.03 mm.

 

 

This comes as no surprise. Discontinuity of the connector termination area has a major impact on signal integrity. There are many more contacts in a Type-C connector than in a Type-A, and the pitch is much smaller. Common sense tells us the mechanical tolerances need to be tighter.

But super tight alignment required by mechanical connectors is problematic for many applications where X, Y, and Z tolerances need to be flexible. Take PCBs with multiple board-to-board connection points. The manufacturing tolerances of the board-to-board connectors does not always allow for a seamless connection between the two connection points. In some cases, forcing the connection can break the solder on the PCBs. In other cases, connected PCBs in applications that vibrate (automobiles for example) stress the solder joints to the point of failure.

 

Are More Complex Mechanical Structures the Answer?

There are mechanical connectors designed to address this issue. A floating connector is an electro-mechanical interconnect that can absorb misalignments in both X and Y directions. But even these connectors do not truly “float.” They typically allow some flexibility in X and Y to align and then once aligned, they snap into place. And of course, this added mechanical complexity adds substantial cost to the design.

 

Floating connectors try to solve a mechanical problem
by designing a more complex mechanical solution.

A critical use case for a floating connection is LED display modules that tile together to build an LED video wall. LED video walls are made up of tens, hundreds, or even thousands of these small LED display modules, all connected by snapping into the backplane with a standard board-to-board connector. Slight misalignment of the modules never mattered in a stadium scoreboard, or on the face of a building, but with LED video walls now entering the conference room space, control rooms and even the home, the pixel pitch (distance between each individual LED) has become so small (sub 1mm) that any misalignment of the module can create a visible seam in the video wall.

Visible seams appear in video walls due to
misalignment caused my fixed mechanical connectors.

 

Left: A typical board-to-board connector: inflexible and can lead to visible seams in tight pixel pitch LED modules
Right: A home grown floating connector on springs to enable some X, Y flexibility – complex, costly, and unreliable

 

Using Solid-state Technology to Address a Mechanical Problem

Although every mechanical engineer loves to solve mechanical challenges, not every mechanical challenge needs a mechanical solution – especially one that ends up being much more complex and costly. Engineering a mechanical connector with increased tolerances comes at a cost: either bandwidth suffers (a USB-A connector has much more tolerance than a USB-C connector but cannot support Type-C speeds); or cost suffers (floating connectors are substantially more expensive than traditional connectors). Keyssa’s non-mechanical solution enables a high-speed signal to connect within wide tolerances at an affordable price.

Keyssa’s solid-state connector frees product designers from some of the limitations of mechanical connectors. When a connector no longer needs to be physically touching, and when the connection is maintained when the two connected devices move independently, many applications where physical connectors have issues become much easier and less expensive to design, and much more reliable.

Keyssa’s X and Y tolerance is up to ±1.5mm. This enables Keyssa connectors to truly “float” within these wide tolerances. PCB solder joints are not stressed when two PCBs come together to connect. Vibration, a key factor in the reliability of connectors in automobiles, factory floors, or ruggedized PCs designed for industrial use, is no longer a concern. LED display modules can be shifted to create perfect pixel alignment without damaging the backplane.

Keyssa’s connectors have wide tolerances and will perform reliably
in instances of gross misalignment.

 

Reimagining the Connector

Keyssa’s high-speed solid-state connector frees engineers to spend time envisioning new ways to design connectors into their products rather than trying to tackle age-old mechanical problems with existing connectors. When connectors no longer need to physically connect, devices have more freedom to move independently of each other while maintaining a high-speed, point-to-point connection. No more broken solder joints, no more metal fatigue caused by vibrating motors, no more misaligned pixels in video walls. Just pure data going from point A to point B – just as it is intended to.

 

For more in this series of “Why Keyssa Built a Better Connector,” see:

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