Technical note · 27 October 2026 · VPX / OpenVPX
Anyone who has specified a VPX system knows the chassis is never just a box. VITA 46/48/65 was written for high-speed switch fabrics and harsh environments — which is exactly why most projects end up with a backplane profile and a mechanical package that no catalogue product matches.
The industry line is that “every backplane is custom”. Behind that line sits a choice: backplane from one supplier and mechanics from another, or both from the same team. Our answer has always been the latter — because we started as a backplane house.
C-BOX designs across four families — CompactPCI, PXIe, VME and VPX — covering topology, stack-up and impedance control, connector selection, power distribution and monitoring circuitry.
This is not a slogan; the adjacent product line can be checked. On the PXIe side we build the BP-2315 backplane family (specification detail in the PXIe selection note): BP-2315G3 is 5 slots, 16 GB/s system bandwidth (PCIe Gen3 x16), 4 GB/s per slot, on-board VCXO clock, 4 hybrid slots. Below it sit an 8 GB/s Gen2 version and a PXI-Only version with PCI 32-bit and 4 PXI slots. All three share one hybrid baseline — variants, not redesigns. The same approach applies to VPX, where the difference is a more complex topology and a larger set of slot profiles.
For us, “custom backplane” does not mean building to a drawing we are handed. It means agreeing on topology, power routing, clock distribution and where monitoring sits before the board is laid out. The cost is more dialogue up front; the benefit is that cards plug in and work.
An MCU on the backplane runs real-time monitoring, and all three thresholds are fixed and documented: temperature above 70 °C flashes amber (steady amber if the MCU itself faults); fan speed below 800 RPM flashes green; any rail deviating more than ±5% flashes blue. On the supply side the figures are equally concrete: at 50 °C ambient, 8 A per contact on J10 and 9 A per contact on J11/J12.
In the field this matters for one reason: when something misbehaves, the first question is heat, fan or power. A chassis that separates those three answers is diagnosed in minutes; one that cannot takes days. For VPX-class power density, this is worth more than the appearance of the front panel.
6U VPX power density is moving toward the 3,000 W class in redundant or symmetric architectures. At that level, cooling stops being a fan-selection question.
Air-cooled 3U/6U cages are decided by fan-tray position, vent geometry and card-guide spacing — these preserve the airflow channel. This is a sheet-metal design problem first and a fan problem second.
Conduction-cooled variants are decided by wedge locks, cold-plate interfaces and thermal paths. These must be machined, not folded — which is where a supplier's real CNC depth shows. Our Kunshan plant runs 23 machining centres and we make these parts in-house.
One point is routinely missed: development benches want airflow and access, while deployed systems want sealed conduction. Whether the same mechanical baseline can grow both versions decides whether a later variant needs new tooling.
VPX programmes often state an availability requirement, which on paper is Availability = MTBF / (MTBF + MTTR). Telecom-grade 99.999% corresponds to 5 minutes 15 seconds of downtime per year.
In that formula, MTTR is where mechanics and structure have direct influence: can a board be replaced live, does replacement require a shutdown, how is the faulty board identified. In the CompactPCI world the established method is the three-tier pin length on the connector — long pins for ground and pre-charge, mid pins for power and bus signals, short pins for BD_SEL#/IDSEL# identification — which is what makes live insertion work. We have been building to that principle for well over a decade, and it transfers directly to VPX projects.
A VPX cage rarely stands alone. It ends up in a 19-inch rack, often with a PDU, fan unit, filter and console alongside. Sourcing the cage from one supplier and rails, panels and hardware from another is how integration delays are born.
C-BOX keeps the whole 19-inch stack in-house:
One supplier, one drawing set, one delivery.
Many test programmes are mixed: the unit under test runs VPX, the instrumentation runs PXIe. The usual failure mode is two suppliers waiting on each other's drawings.
We also supply the PXIe platform: Gen3 18-slot (PXIe-62785, 10+1 timing slots, 24 GB/s system bandwidth, 50 W per slot), 2722G3 / 2519G3 / 2315G3 at 58 W per slot, the Gen2 family, and the rugged portable 2519PMK with integrated display. Controllers, digitizers, DAQ, arbitrary waveform generators and bus cards sit in the same selection system.
For a mixed programme there is one supplier to talk to: backplane and mechanics from C-BOX, PXIe instrumentation specified from the same platform range, interfaces and drawings aligned internally.
Next step. Send the backplane configuration, thermal load and mounting requirements. If the backplane is not fixed yet, we can review it at topology stage; if it already exists, we build the mechanics to it. Either way you get a manufacturability review and a costing. Request a review.
Send the backplane configuration and thermal load — we will review manufacturability and quote the mechanical package.
