<breakout />

Overview

A <breakout /> is similar to a <group /> 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 /> 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: 5.275,
},
{
  name: "ADDRESS",
  signals: [
    "ADDR0",
    "ADDR1",
    "ADDR2",
    "ADDR3",
    "ADDR4",
    "ADDR5",
    "ADDR6",
    "ADDR7",
  ],
  pins: [11, 21, 31, 41, 51, 61, 71, 81],
  targetX: -5.275,
},
]

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">
      <autoroutingphase
        autorouter="fanout"
        fanoutRoutingLayers={["top"]}
        fanoutBoundaryPadding="1.5mm"
        busFanoutDirections={{
          DATA: "center_right",
          ADDRESS: "center_left",
          GND_44: "center_left",
          VCC_45: "bottom_center",
          GND_46: "bottom_center",
          VCC_47: "center_right",
          VCC_54: "center_left",
          GND_55: "top_center",
          VCC_56: "top_center",
          GND_57: "center_right",
        }}
      />
      <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 explicit <autoroutingphase /> is needed here because the advanced fanout controls live on the phase. busFanoutDirections sends each named bus toward a specific side and can also guide an individual source trace, as shown for the power balls.

fanoutRoutingLayers={["top"]} reserves the top layer for signal escape. The GND and VCC traces have only one component endpoint, so the fanout router infers their destination layers from the matching <copperpour /> elements and drops them to inner1 and inner2. Those pour layers do not need to appear in fanoutRoutingLayers.

If a net has pours on multiple layers, disambiguate the plane destination with an explicit map:

<autoroutingphase
  autorouter="fanout"
  fanoutRoutingLayers={["top"]}
  fanoutPourNetMap={{ inner1: "GND", inner2: "VCC" }}
/>

Auto-Generated Breakout Points

When traces connect from components inside a <breakout /> to components outside of it, tscircuit can create the needed breakout points automatically. This keeps the breakout local to the component cluster while still letting board-level traces connect to headers and other surrounding parts.

The example below routes a QFP16 controller inside a breakout to an external pin header and nearby passives without adding any manual <breakoutpoint /> elements.

export default () => (
  <board width="20mm" height="16mm">
    <breakout name="MCU_BREAKOUT" padding="1mm">
      <chip
        footprint="qfp16"
        name="U1"
        pinLabels={{
          pin1: "GPIO1",
          pin2: "GPIO2",
          pin3: "GPIO3",
          pin4: "GPIO4",
          pin5: "VCC",
          pin6: "GND",
          pin7: "SDA",
          pin8: "SCL",
          pin9: "RESET",
          pin10: "BOOT",
          pin11: "GPIO5",
          pin12: "GPIO6",
          pin13: "GPIO7",
          pin14: "GPIO8",
          pin15: "GPIO9",
          pin16: "GPIO10",
        }}
        pcbX={0}
        pcbY={0}
      />
      <capacitor
        name="C1"
        capacitance="100nF"
        footprint="0402"
        pcbX={-3.5}
        pcbY={2.4}
      />
      <trace from="C1.1" to="U1.GPIO1" />
      <trace from="C1.2" to="U1.GPIO3" />
    </breakout>
    <pinheader
      name="J1"
      pinCount={4}
      footprint="pinrow4"
      pinLabels={["VCC", "GND", "SDA", "SCL"]}
      pcbX={7}
      pcbY={0}
      pcbRotation={90}
    />
    <resistor
      name="R1"
      resistance="10k"
      footprint="0402"
      pcbX={-5}
      pcbY={-2.4}
      connections={{ pin1: "U1.RESET", pin2: "net.VCC" }}
    />
    <trace from="J1.VCC" to="U1.VCC" />
    <trace from="J1.GND" to="U1.GND" />
    <trace from="J1.SDA" to="U1.SDA" />
    <trace from="J1.SCL" to="U1.SCL" />
  </board>
)

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`.
`fanoutBoundaryPadding`	Padding between the source pads and the shared boundary where fanout traces terminate.

Overview​

Auto-Generated Breakout Points​

Properties​

Overview

Auto-Generated Breakout Points

Properties