ZP3 Interboard Input/Output Connector

Owned by Daniel Puratich
Last updated: 2022-10-08
4 min read

Purpose

The inter-board connector for ZP3 will be our platform for communication between Interface and Primary PCBAs. The current concept art for the board is as shown below. The primary contains power filter, micro-controller, SD card reader, a few LEDs, and IO Connector. The interface contains all IO headers (of whichever type is preferred) we would like as well as potential other devices such as IMUs or buzzers, buttons, and extra LEDs. The idea is either board can be spun in order to facilitate progress and allow ZP3 to have a solid incremental design process.

Goal for the spec of the connector is roughly 40 pins? Mated height between 3 and 10mm. The pitch should be fairly large as we have plenty of space, 0.5-1mm seems nice, but the larger the better to help ensure solid electrical connection under vibration. Dimension height note, 1210 cap is 2.6mm tall, microSD slot used 2mm height max, 5mm seems like an optimal number for components on the bottom of the interface having plenty of clearance on current components.

Below is a preliminary drawing to show the concept and end usage of this connector.

Research

  • Slim Stack Molex (Slim Stack Core)

    • As a general rule in this series the larger the pitch the larger the mated height. This is a rough balancing act as I want the most pitch and pins with the smallest mated height.

    • SlimStack 0.50mm Pitch Series

    • SlimStack 0.80mm Pitch Series

      • Receptor Mouser: 52465-4071

      • Receptacle Digikey: 0524654071

      • Receptacle Molex: 524654071

      • Receptacle Drawing: 524654071

      • Plug Molex: 533074071

      • Plug Mouser: 53307-4071

      • Plug Digikey: 0533074071

      • Plug Drawing: 533074071

      • 0.8mm pitch (relatively large) 40 circuit

      • 17.6mm long receptacle

      • Receptacle Height 3.55mm

      • 3.65mm Plug height

      • 17.8mm long plug

      • They don’t make this in a more circuit option which is disappointing, but should be fine, potentially fit three of these instead of the originally drafted two.

      • Mated height calculated: (3.65mm plug height overall) + (3.55mm receptacle overall height) - (2.10mm receptacle mating insert) = 3.65 + 3.55 - 2.1 = 5.1mm

      • Largest slimstack pitch 0.8mm, 5mm mated height, 20mm long

        • There are technically larger pitch ones, but the mated height is very high, recall 8mm perceived maximum

    • 52901

      • Mated height is too tall, though I like the circuit count, this is off the table

      • Excerpt from drawing sheet regarding this:

      • Essentially receptacle roughly sets mated/stacked height and then plug series refines it

      • The only difference between products in the series is pin count

      • The above drawing shows the plug and receptacle visually.

    • 52885 ← Receptacles is more my speed size wise!

      • 0.635mm = 25 mil, pitch common for all of these receptacles, decent number

      • 6.4mm mated height

      • 528850874

        • Molex Page

        • 80 pin (this is a lot, but extra is fine and leaves room for future expansion, unused pins is fine and extra ground would be nice)

        • 33mm long total (35mm footprint length roughly)

        • Molex Drawing

        • This feels very promising to me, now I need to find the mating connector

      • For this series the mated height is determined by the plug, the receptacle is common except for pin count changes

      • 20-240 circuit options, I plan on using at least two of these connectors (three in a pinch): 60 pins feels like too little since micro has 144 pins, 80 is a bit much, but it’ll be good, too much is fine

      • The cost is high, but for a solid connector, it’s all worth it.

      • Corresponding Plug 550910874 molex

        • The 6mm mated height version of plug probably ideal!

        • Very low to hopefully reduce effects of vibe/shear

Conclusion

I guess I did not validate further then Molex Slimstack series. This is Molex’s flagship for board to board connectors and Molex is generally reliable in my opinion thus I feel comfortable not evaluating other options despite that being the original intention. I’ll have others review this decision before it’s final, but by the above research I would like ZP3 platform to use:

  • Receptacle - 528850874

  • Plug - 550910874

  • Specifications:

    • Pins: 80

    • Pitch: 0.635mm

    • Mated Height:

    • Estimate Footprint Length: 35mm

    • Cost for QTY(60) pairs: $1000

    • QTY per ZP3 Interface and Primary Pair 2

  • Pin 1

    • Molex decided to not put this in the datasheet but it can be found at the bottom of the page here:

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