A breakout board (BOB) is a simple printed circuit board that allows access to the pins or leads on a surface-mount device (SMD or SMT) package. Breakout boards provide an easy way to prototype, test, or use an SMT component in a breadboard or through-hole application. They serve as an intermediate mounting platform to convert fine-pitched SMT components into more accessible thru-hole pins and connectors.
What Are SMT Components?
SMT, or surface-mount technology, refers to the method of mounting electronic components directly onto the surface of PCBs rather than with wire leads that pass through holes. Typical SMT component packages include:
- Quad Flat Packages (QFP)
- Ball Grid Arrays (BGA)
- Tiny chip-scale packages like 0201 and 01005
- Connectors like SMA, SMP, and uSD
- Sensors, oscillators, resistors, capacitors
SMT enables great size reduction versus through hole components. However, the small size and dense connection pins also limit accessibility for prototyping. This is where breakout boards come in.
What Are Breakout Boards?
Breakout boards provide these key functions:
- A simple PCB that an SMT component is mounted on
- The dense SMT footprint is “broken out” into accessible through-hole pins
- Allows easy connection of SMT parts to breadboards or cables for prototyping
Breakout boards make working with SMT components quick and easy for prototyping or testing, without requiring reflow soldering. They also enable easy incorporation of SMT parts into through-hole projects.
Typical Breakout Board Features
Breakout boards implement various features to improve usability:
- Through-hole pins – The dense contacts of chips are converted to widely spaced pins.
- Header sockets – Pin rows connect to standard 0.1″ pitch headers/connectors.
- Castellated edges – Allow soldering wires directly to board edge.
- Silkscreen labels – Identify pin names/numbers for reference.
- Pad numbering – Match pinout diagrams on datasheets.
- Test points – Exposed metal pads for multimeter probes.
- Mounting holes – Allow securing board with standoffs.
- Polarization keys – Help correctly orient polarized components.
Applications and Uses of Breakout Boards
Breakout boards are indispensable tools for working with SMT components in prototyping:
- Interfacing SMT ICs – Quickly interface any SMT microcontroller, sensor, memory chip, etc.
- Simplifying designs – Avoid complexity of mixing SMT and through-hole assemblies.
- Testing and characterization – Convenient points to connect test probes and instruments.
- SMT integration for hobbyists – Incorporate advanced SMT parts in DIY electronics projects.
- Temporary adapter boards – Provide access to SMT parts for repair/reworging of consumer electronics.
- Education – Allows students to easily experiment with SMT components with minimal tools and experience.
Types of Breakout Boards
There are a few common types and categories:
Generic Boards
- SMT Carrier Boards – Accept a range of chip sizes from 0201 to QFN with changeable adapter sockets.
- Universal Breakout Boards – Array of connect pads for hand-soldering SMT parts.
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- Microcontroller Boards – Break out pins of SMT MCUs like ESP32, STM32, etc.
- Sensor Boards – For SMT sensors like IMUs, magnetomers, PMICs.
- Memory Boards – SD cards, EEPROMs, flash storage chips.
- RF and Wireless Boards – Bluetooth, WiFi, GSM, NFC modules.
- Display and LCD Boards – OLED, TFT displays.
- Audio Boards – For SMT codecs, amps, DAC/ADC chips.
Any specialized SMT component can have a matching breakout board for easy interconnection.
How Are Breakout Boards Manufactured?
Specialized PCB assembly is used to mount SMT components onto breakout boards:
- SMT Assembly – Pick-and-place machines precisely mount the chips using solder paste and reflow.
- Selective wave soldering – Adds through-hole pins to bottom side after SMT loading.
- Hand assembly – For quick prototyping, chips can be hand-soldered to blank generic boards.
- Rework and QC – Optical inspection and rework of bridges or tombstoned parts.
- Conformal coating – Protective epoxy layer prevents accidental short circuits.
Fully assembled boards with mounted SMT parts are available from electronics suppliers. But blank boards allow hand-assembly for custom parts.
Design Considerations for Breakout Boards
Several factors are considered when designing breakout boards:
- Original footprint – Matching the SMT part’s datasheet footprint exactly.
- Pad spacings – Sufficiently wide gaps between edge connection pads.
- Routing channels – Areas clear of copper between pads for isolating signals.
- Pinouts – Arranging edge pins to match reference designs.
- Pin labeling – Clear silkscreen numbering matching datasheets.
- Board shape/size – Rectangular or circular board large enough for part.
- Mounting holes – Including fastening points if needed for stability.
- Stackup – 4-layer boards with power/ground planes for high-frequency parts.
Careful breakout board design ensures the SMT component connects properly and signals are cleanly routed.
Creating Custom Breakout Boards
For highly specialized SMT parts, engineers may design custom breakout boards tailored to an exact application:
Design Process
- Obtain datasheet for target SMT component
- Import footprint into PCB CAD tool as new component
- Arrange I/O pins on edges with spacings for connectivity
- Add text labels, markers, mounting holes as needed
- Export Gerber files of finished board layout
Manufacturing
- Send Gerber files to trusted PCB fabrication vendor
- Source compatible SMT components for assembly
- Ship SMT parts and blank boards to assembly contractor
- Have assembled boards delivered with mounted components
While more complex than generic boards, custom breakout PCBs enable specialized SMT components to be easily utilized in prototype projects.
Integrating Breakout Boards in Prototyping
Breakout boards are easy to integrate into electronics projects:
- Solderless – Insert header pins into breadboard or use jumper wires for no-solder prototyping.
- Soldered wires – Solder solid core wires directly to edge pads for semi-permanent connections.
- Castellated edges – Allows soldering jumper wires neatly to board edge.
- Stacking headers – Female headers on multiple boards stack together when prototyping complex circuits.
- Screw terminals – Some boards provide screw terminals for field wiring.
With standardized pin spacing, breakout boards drop into breadboards or custom circuits easily.
Sourcing Breakout Boards
Many online retailers offer a wide selection of ready-made breakout boards:
- SparkFun – Extensive catalog of over 1500 boards for most common SMT ICs and modules.
- Adafruit – Another leading provider carrying 1000+ boards. Very beginner friendly.
- Seeed Studio – Manufacture and sell many different breakout boards.
- Tindie – Marketplace for unique products has breakouts made by DIY creators.
- eBay/AliExpress – Cheap boards of common parts can be sourced directly from China. Quality varies.
For unusual or custom SMT chips, consider having PCB assembly houses manufacture a custom breakout board to your requirements.
Pros and Cons of Using Breakout Boards
Breakout boards provide unmatched convenience and usability but also some limitations:
Advantages
- Extremely easy to prototype without soldering skills.
- Integrates SMT components into breadboard or through-hole designs.
- Cost effective compared to using development boards.
- Wide selection of ready-made boards available.
Disadvantages
- Adds parasitic capacitance that may affect high frequency signals.
- Less compact than direct SMT integration.
- Costly for low volume or custom designs.
- Limited availability for uncommon components.
Overall, breakout boards provide the simplest path to utilizing SMT chips in prototype development and education applications. Their accessibility enables incredible innovation.
Example Breakout Boards
To illustrate typical breakout board implementations and usage, here are some examples for common SMT components:
ESP32 Series Module
- Breaks out GPIO, power, and serial pins on popular ESP32 WiFi/BT module.
- 0.1″ pitch castellated connection pads for easy breadboard use.
- USB-serial interface eliminates need for FTDI cable.
- Ready to load MicroPython firmware out of the box.
BME680 Sensor
- Exposes I2C pins for Bosch’s integrated environment sensor.
- Test points provided to probe SDA, SCL lines.
- Qwiic connector for plug and play connection to development boards.
- Minimalist design focused on easy connectivity.
AT24C02B EEPROM
- Dual row female pinheaders interface to standard jumper wires.
- Address select pins broken out to dip switches.
- Test pads provided for ICSP interface.
- Simple and general purpose.
Frequently Asked Questions
What is the difference between a breakout board and a development board?
Breakout boards just provide connectivity for a single SMT component. Development boards integrate multiple ICs and peripherals with power regulation to create a complete system for building applications on top of.
Can I solder wires directly to a breakout board?
Yes, the row of pads along the edges of most breakout boards are designed for easy soldering of solid core wire jumpers. Having castellated edges allows soldering wires right to the PCB edge.
How are breakout boards different from adapter boards?
Adapter boards convert between different pinouts or form factors rather than SMT to through-hole. For example, converting DIP chips to work in breadboards or SIL pin headers to SIP sockets. The goal of accessing SMT specifically defines breakout boards.
Can I probe test points on a breakout board while a circuit is powered?
Use extreme caution, as probing powered test points risks short circuits. Add jumper wires from test points to measurement equipment inputs instead of direct probing whenever possible. Power off completely if probing is required.
What is the most flexible breakout board for prototyping many different SMT ICs?
Generic SMT carrier boards accept different sized adapter sockets allowing a wide range of chip packages to be used. However, customized boards for specific components offer higher quality signal routing.
