Hardware Manufacturing

The complete design files (including schematic and PCB design files) are available in the project's Git repository.

For our builds, we ordered the PCBs off PCBWay. Many other manufacturers offer the same service, so you are free to choose. If necessary, adjust the Design Rule Check (DRC) settings in KiCad to the capabilities of your manufacturer to verify that the boards are able to be manufactured correctly.

Depending on the board, a 2-layer or 4-layer stack is required with standard manufacturing specifications and without impedance-controlled manufacturing. If you want to adapt the circuits (especially the receiver) to other hydrophone impedances, you must match the input impedance of the receiver circuit. The schematic contains corresponding notes.

In the following, we give a short overview on the steps required to prepare the files for PCB manufacturing and building.

Creating Gerber files

Export files

Manufacturer Specifics

Each PCB manufacturer uses a different file configuration, so the files have to be individually generated. For further details, refer to the manual of your PCB manufacturer.

If the manufacturer accepts KiCAD PCB files, you can skip this section and send the *.kicad_pcb files directly.

Depending on your PCB manufacturer, there might already exist a KiCad plugin simplifying the export process.

In the case of PCBWay, simply install the "PCBWay Fabrication Toolkit" using KiCad's "Plugin and Content Manager". The plugin adds a button to KiCad's PCB editor which you can use to export all fabrication files in a single click.

Repeat the export process for all boards you intend to built. For each board, sent the created ZIP archive containing its Gerber files to your manufacturer.

Verify files

Before ordering, it is a good idea to check whether all layers are included in the Gerber files. You can use the KiCad Gerber Viewer to view the production output files.

Assembling the boards

Bill of materials

BOM files for the default configuration are included as CSV files in the repository. If you make changes to the schematics, regenerate them using the export-boms.sh script.

Part descriptions of all ICs and some other components are available in the schematics and BOMs, where the BOMs also include order information for the ICs. Please be aware that some capacitors and resistors, particularly those in the analog filter chain of the receiver board, require small tolerances; we suggest 1% and 2% tolerances with resistors and capacitors, respectively. Another option is to manually measure and hand-pick components within those limits.

Soldering

The components can be placed and soldered with different techniques (soldering iron, hot air, reflow oven). Most components can be hand-soldered, and no special handling is necessary. ESD protection is strongly recommended.

Hot air / Reflow oven

If you use hot air, note that all connectors, the button (mainboard) and the LEDs will melt if they are heated up excessively. To prevent this, we suggest to hand-solder these components in a last step and, in particular, after hot-air and/or reflow soldering.

Additional flux can make the soldering easier and increase the quality of the solder points (especially PB-free). Which flux you use is not important, as long as it is designed for SMD soldering.

Cleaning

If you have used "no-clean" flux, cleaning is not required. Otherwise it is mandantory, as the flux will damage the board (longtime)!

Tip

Test the boards before cleaning. Remaining flux can be used for resoldering.

After the soldering, the boards can look a bit dirty. Cleaning them is fine, if you prefer. The appropriate way to clean the boards depends on the flux and soldering tin you have used. In the following table, the cleaning methods we used are listed. Possibly, you have to use more than one method, or a mixture.

Type	Comment
Isopropanol	Inflamible!
Aceton	If Isopropanol is not working. Inflamible! Removes the print on RX:L2 !
Soap+Water	Scrup. Wash board afterwards.
(Destilled) Water	Dry board after cleaning! Oven: low temp; Hot air: high flow, low temp