<breakout />

Overview

A <breakout /> is a transparent routing container similar to a <group />. 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 /> elements to define explicit exit locations, or let tscircuit generate breakout points for connections that leave the breakout.

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.

const buses = [
{
  name: "DATA",
  signals: [
    "DATA0",
    "DATA1",
    "DATA2",
    "DATA3",
    "DATA4",
    "DATA5",
    "DATA6",
    "DATA7",
  ],
  pins: [20, 30, 40, 50, 60, 70, 80, 90],
  targetX: 5.75,
},
{
  name: "ADDRESS",
  signals: [
    "ADDR0",
    "ADDR1",
    "ADDR2",
    "ADDR3",
    "ADDR4",
    "ADDR5",
    "ADDR6",
    "ADDR7",
  ],
  pins: [11, 21, 31, 41, 51, 61, 71, 81],
  targetX: -5.75,
},
]

const powerDrops = [
{ pin: 44, name: "GND_44", net: "GND" },
{ pin: 45, name: "VCC_45", net: "VCC" },
{ pin: 46, name: "GND_46", net: "GND" },
{ pin: 47, name: "VCC_47", net: "VCC" },
{ pin: 54, name: "VCC_54", net: "VCC" },
{ pin: 55, name: "GND_55", net: "GND" },
{ pin: 56, name: "VCC_56", net: "VCC" },
{ pin: 57, name: "GND_57", net: "GND" },
]

const fanoutExitYs = [
-1.2, -0.625, -0.375, -0.125, 0.125, 0.375, 0.625, 1.2,
]

const bgaPinLabels = Object.fromEntries([
...buses.flatMap((bus) =>
  bus.signals.map((signal, index) => [
    "pin" + bus.pins[index],
    signal,
  ]),
),
...powerDrops.map((drop) => ["pin" + drop.pin, drop.name]),
])

export default () => (
  <board
    width="18mm"
    height="12mm"
    layers={6}
    minTraceWidth="0.1mm"
    defaultTraceWidth="0.1mm"
    minTraceToPadEdgeClearance="0.1mm"
    minViaEdgeToPadEdgeClearance="0.1mm"
    minViaHoleDiameter="0.2mm"
    minViaPadDiameter="0.5mm"
  >
    <copperpour layer="inner1" connectsTo="net.GND" />
    <copperpour layer="inner2" connectsTo="net.VCC" />
    <breakout
      name="BGA_BREAKOUT"
      width="14mm"
      height="11mm"
      fanoutRoutingLayers={["top"]}
      fanoutBoundaryPadding="1.5mm"
      fanoutPourNetMap={{ inner1: "GND", inner2: "VCC" }}
      busFanoutDirections={{
        DATA: "center_right",
        ADDRESS: "center_left",
      }}
    >
      <chip
        name="U1"
        footprint="bga100_grid10x10_p0.8mm_pad0.35mm_circularpads"
        pinLabels={bgaPinLabels}
      />
      {buses.map((bus) => (
        <chip
          key={"EDGE_" + bus.name}
          name={"EDGE_" + bus.name}
          pcbX={bus.targetX}
          pinLabels={Object.fromEntries(
            bus.signals.map((signal, index) => [
              "pin" + (index + 1),
              signal,
            ]),
          )}
          footprint={
            <footprint>
              {fanoutExitYs.map((pcbY, index) => (
                <smtpad
                  key={"pin" + (index + 1)}
                  portHints={["pin" + (index + 1)]}
                  pcbX={0}
                  pcbY={pcbY}
                  width="0.4mm"
                  height="0.1mm"
                  shape="rect"
                />
              ))}
            </footprint>
          }
        />
      ))}
      {buses.map((bus) => (
        <bus
          key={bus.name}
          name={bus.name}
          connections={bus.signals.map(
            (signal) => bus.name + "_" + signal,
          )}
        />
      ))}
      {buses.flatMap((bus) =>
        bus.signals.map((signal) => (
          <trace
            key={signal}
            name={bus.name + "_" + signal}
            from={"U1." + signal}
            to={"EDGE_" + bus.name + "." + signal}
          />
        )),
      )}
      {powerDrops.map((drop) => (
        <trace
          key={drop.name}
          name={drop.name}
          from={"U1." + drop.name}
          to={"net." + drop.net}
        />
      ))}
    </breakout>
  </board>
)

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 on the enclosing board. An explicit map is useful when a net has pours on multiple layers:

<breakout
  fanoutRoutingLayers={["top"]}
  fanoutPourNetMap={{ inner1: "GND", inner2: "VCC" }}
>
  {/* BGA, buses, and traces */}
</breakout>

Properties

<breakout /> accepts all the layout properties of <group /> plus a few extras:

Property	Description
padding	Uniform padding around the breakout region.
paddingLeft / paddingRight / paddingTop / paddingBottom	Control padding for each side individually.
autorouter	Autorouter used to escape components inside the breakout. Defaults to fanout.
busFanoutDirections	Maps named buses to preferred escape directions.
fanoutBoundaryPadding	Padding between the source pads and the shared boundary where fanout traces terminate.
fanoutRoutingLayers	Copper layers available to boundary-terminated fanout buses.
fanoutPourNetMap	Maps plane layers to nets for source-only fanout escapes. Matching copper pours are inferred when omitted.