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seveibar merged 3 commits into from
Jul 31, 2026
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Document breakout as a transparent routing directive #834

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7ed12de
Move breakout pours into routing scope
seveibar Jul 31, 2026
f24d91e
Document breakout as a transparent routing directive
seveibar Jul 31, 2026
34799ac
Stack breakout preview vertically
seveibar Jul 31, 2026
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22 changes: 14 additions & 8 deletions docs/elements/breakout.mdx
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Expand Up @@ -6,19 +6,21 @@ description: >-

## Overview

A `<breakout />` is similar to a [`<group />`](./group.mdx) but is meant for situations where you
want to guide the autorouter on where connections should exit the group. Inside
a breakout you can place [`<breakoutpoint />`](./breakoutpoint.mdx) elements to
define explicit exit locations, or let tscircuit generate breakout points for
connections that leave the breakout.
A `<breakout />` is a transparent routing container similar to a
[`<group />`](./group.mdx). It does not create a subcircuit, selector scope, or
private net scope. Instead, its routing properties guide the autorouter on where
connections should exit the region. Inside a breakout you can place
[`<breakoutpoint />`](./breakoutpoint.mdx) elements to define explicit exit
locations, or let tscircuit generate breakout points for connections that leave
the breakout.

import CircuitPreview from "@site/src/components/CircuitPreview"

This 100-pin BGA keeps two 8-bit buses on contiguous outer columns and assigns
each bus an explicit fanout direction. Eight center-region balls connect to
GND and VCC pours on separate inner layers.

<CircuitPreview defaultView="pcb" code={`
<CircuitPreview verticalStack defaultView="pcb" code={`
const buses = [
{
name: "DATA",
Expand Down Expand Up @@ -172,14 +174,18 @@ The breakout uses the fanout autorouter by default, so its fanout controls can
be set directly on `<breakout />`. `busFanoutDirections` sends each named bus
toward a specific side.

Because `<breakout />` is transparent, its traces use the same GND and VCC nets
as the board-level copper pours. The pours do not need to be children of the
breakout, and no net exposure or separate `<autoroutingphase />` is required.

`fanoutRoutingLayers={["top"]}` reserves the top layer for signal escape. The
GND and VCC traces have only one component endpoint, so `fanoutPourNetMap`
drops them to `inner1` and `inner2`. Those plane layers do not need to appear in
`fanoutRoutingLayers`.

When `fanoutPourNetMap` is omitted, tscircuit infers the plane destinations
from matching `<copperpour />` elements. An explicit map is useful when a net
has pours on multiple layers:
from matching `<copperpour />` elements on the enclosing board. An explicit map
is useful when a net has pours on multiple layers:

```tsx
<breakout
Expand Down
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