# Route Your Board in the Flux Chat: Pairs, Lengths, USB-C, Fanout, and Every Edit After

Route a complete board or selected nets with the Flux agent. Route differential pairs, match lengths, fan out BGAs, break out USB-C, and change widths, layers, and routes from the chat.

Written by [Matthias Wagner](https://flux.seobdtools.com/natarius)

Published Oct 2026 - 6 min read

![Route Your Board in the Flux Chat: Pairs, Lengths, USB-C, Fanout, and Every Edit After](https://flux.seobdtools.com/p/assets/blogs/agentic-routing/main.webp)

Picture a motor controller on the last day of placement. It has a USB-C connector at the edge, a radio module with a chip antenna, a DDR memory, a buck converter, and four mounting holes that line up with the bosses of the enclosure. The mechanical engineer has signed off on the board outline. Now someone has to route it.

Routing a board like this by hand is slow, careful work. The USB pair needs a constant gap. The antenna feed needs the right width and no vias. The memory lanes need matched lengths. The power rails need wide copper. Then every review comment means another round of rip-up and reroute.

In Flux, the engineer writes one sentence in the chat: "Route this board." The Flux agent routes it. When a route needs to be different, the engineer says so in the chat, and Flux changes that route.

## What you can ask Flux to route

-   **A complete board.** Ask Flux to route the board.
-   **The nets that you name.** Route one net, a bus, or the nets of one part.
-   **Differential pairs.** Route USB, Ethernet, LVDS, MIPI, and PCIe pairs as pairs, with the impedance, layer, and skew that you need.
-   **USB-C.** Break out a USB-C connector and route its data pair to the chip.
-   **Matched lengths.** Match the lanes of a memory bus, a parallel bus, or a clock group to a target length, within the tolerance that you give.
-   **RF and antenna feeds.** Route a 50 Ω feed on the layer that you choose, with no vias and rounded bends.
-   **Power.** Route rails at the width that their current needs.
-   **Dense parts.** Fan out a BGA, a fine-pitch IC, a QFN, or a dense connector, and route its escape traces.

![Board layout of a GNSS receiver with an FPGA in a BGA package and dense fan-out routing, in Flux](https://flux.seobdtools.com/p/assets/homepage-v2/eda-ti375-fpga-gnss-layout.webp)

A GNSS receiver with an FPGA in a BGA package, routed in Flux.

## Refine any route in the chat

The first route is rarely the last. Reviews add requests, the enclosure moves a connector, and a test shows a noisy clock. In Flux, you make these changes the way you would ask a colleague:

-   "Make the 5V trace from the USB-C connector to the regulator 1 mm wide."
-   "Move the SPI clock to the bottom layer, away from the antenna."
-   "Reroute the I2C bus around the left side of the MCU."
-   "Delete the routes of the debug header and route them again with no vias."
-   "Round the corners of the RF feed."
-   "Match the two traces of the Ethernet pair within 0.1 mm."

Flux changes the routes that you name. Tell Flux which routes to keep, and it keeps them. Every route follows your design rules: your trace widths, clearances, and via sizes.

## Five example scenarios

These scenarios are illustrations. They show how an engineering team can use routing in Flux.

### An industrial sensor hub: one sentence for the whole board

An engineer designs a sensor hub with a USB-C port for power and data, a 2.4 GHz radio, a buck converter from 24 V, and an MCU with a debug header. She routed the radio section by hand. Now she asks: "Route this board. Keep the copper I already drew." Flux routes the USB-C pair, the 24 V input, the 3.3 V rail, and the signal nets, and keeps her radio routing as she drew it. [Start a sensor hub like this in Flux](https://flux.seobdtools.com/signup?destinationPath=%2Fprojects%2Fcreate%3Fprompt%3DDesign%2520an%2520industrial%2520sensor%2520hub%2520in%2520an%2520aluminum%2520enclosure%253A%2520a%2520USB-C%2520port%2520for%2520power%2520and%2520data%252C%2520a%25202.4%2520GHz%2520radio%2520with%2520a%2520chip%2520antenna%252C%2520a%252024%2520V%2520to%25203.3%2520V%2520buck%2520converter%252C%2520and%2520an%2520MCU%2520with%2520a%2520debug%2520header.%2520Then%2520route%2520the%2520board%252C%2520with%2520the%2520USB%2520data%2520lines%2520as%2520a%252090%2520ohm%2520differential%2520pair%2520and%2520the%2520antenna%2520feed%2520as%2520a%252050%2520ohm%2520line%2520with%2520no%2520vias.).

### A compute module: a DDR byte lane, matched

An engineer routes a compute module with an SoC and a DDR memory. He asks: "Route DQ0 to DQ7 and DQS0 of the DDR byte lane, and match every lane to DQS0 within 0.5 mm." Flux routes the byte lane and matches the lanes to the strobe.

### An FPGA board: escape a fine-pitch BGA

A GNSS receiver has an FPGA in a fine-pitch BGA at the center of the board. The engineer asks: "Fan out the FPGA and route its escape traces." Flux fans out the FPGA and routes its escape traces. Then the engineer asks Flux to route the rest of the board.

### A handheld meter: the enclosure moves a connector

The mechanical design of a handheld meter changes late. The new enclosure needs the probe connector J3 4 mm closer to the left edge. The board and the enclosure are in the same Flux project, so the engineer moves the connector and asks: "Reroute the nets of J3. Keep every other route as it is." Flux reroutes the nets of J3 and keeps the other routes. The engineer checks the fit of the board in the enclosure in the 3D view of the same project.

### A wireless camera: a review comment, fixed in the chat

In the design review of a wireless camera, the RF engineer asks for two changes: a wider 5 V trace, and the SPI clock away from the antenna. The layout owner writes: "Make the 5V trace from the USB-C connector to the regulator 1 mm wide, and move the SPI clock to the bottom layer, away from the antenna." Flux changes those two routes. [Start a camera module like this in Flux](https://flux.seobdtools.com/signup?destinationPath=%2Fprojects%2Fcreate%3Fprompt%3DDesign%2520a%2520wireless%2520camera%2520module%2520with%2520an%2520image%2520sensor%252C%2520a%2520Wi-Fi%2520radio%2520with%2520a%2520chip%2520antenna%252C%2520a%2520USB-C%2520port%252C%2520and%2520a%2520molded%2520enclosure%2520with%2520a%2520lens%2520window.%2520Then%2520route%2520the%2520board%252C%2520and%2520keep%2520the%2520SPI%2520clock%2520away%2520from%2520the%2520antenna.).

## Before and with Flux

| Step | Before | With Flux |
| --- | --- | --- |
| **Route the board** | Hand routing, then autorouter cleanup | "Route this board." |
| **Differential pairs and USB-C** | Routed by hand, pair by pair | One sentence for each pair |
| **Matched lengths** | Meanders drawn and measured by hand | A target length and a tolerance in the chat |
| **BGA fanout** | Escape routing by hand | "Fan out the FPGA." |
| **Review changes** | Rip up and route again by hand | One sentence in the chat |

## Part of the whole device

Flux is an AI hardware engineer. It designs the complete device: the requirements, the parts, the schematic, the board, the firmware, the enclosure and the mechanical parts, the wire harness, the simulations, and the manufacturing files. In Flux, the agent does this design work in hours, not weeks. Routing is one step of that work, and it happens in the same project as the others. The connector positions come from the enclosure. The routed copper goes to the electromagnetic simulation. The finished board goes to the fabrication files and the quote.

## Prompts to try on your board

-   "Route this board. Keep the copper I already drew."
-   "Route USB\_D\_P and USB\_D\_N from J1 to U1 as a 90 ohm differential pair on the top layer, with as few vias as possible."
-   "Break out the USB-C connector J1 and route its data pair to the MCU."
-   "Route DQ0 to DQ7 and DQS0 of the DDR byte lane, and match every lane to DQS0 within 0.5 mm."
-   "Route RF\_FEED from the SMA connector J2 to the matching network as a 50 ohm line on the top layer, with no vias and rounded bends."
-   "Fan out the FPGA and route its escape traces."
-   "Make the 5V trace from the USB-C connector to the regulator 1 mm wide, and move the SPI clock to the bottom layer, away from the antenna."
-   "Reroute the nets of J3. Keep every other route as it is."

Read more in the docs: [Route with Flux](https://docs.flux.ai/reference/route-with-flux).

## Start now

Open your board in [Flux](https://flux.seobdtools.com/) and ask the agent to route it. [Start Free Trial](https://flux.seobdtools.com/signup).

## About the author

[Matthias Wagner](https://flux.seobdtools.com/natarius)

Founder & CEO at Flux

Matthias is the Founder and CEO of Flux, a hardware design platform that's revolutionizing how teams create and iterate on circuits. Find him on Flux [@natarius](https://flux.seobdtools.com/natarius).

Let’s start building

Build your big idea together with Flux. All you need to do is describe what you want to make, or what problem you want to solve. Flux will work with you to make it a reality.

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