Customer:

A small RF hardware startup in southeast Michigan.

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Description:

Prototyping microwave devices like radar systems in a lab requires specialized electronics in a small form factor. A microwave attenuator allows engineers to adjust the power output of a microwave signal in an experimental RF system.

 

The customer in this case developed a miniaturized attenuator circuit & PCBA set for laboratory use and needed a durable, RF-tight enclosure and user interface to complete his product. 

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Customer Requirements and Challenges:

• One entire side of one of the PCBAs needed to be soldered to the enclosure interior in order to maximize PCBA grounding.

• Rigid electrical connectors that required soldering to a PCB on one end and mechanical fixing to the enclosure on the other end. This required the connector to be located with an accuracy of ~0.004” (0.1 mm) relative to the PCBA and enclosure

• The customer requested LEDs to be added to the assembly to indicate power and functional state.

• The customer required access to two PCBA DIP switches without opening the enclosure.

 

To meet these requirements, I developed:

• A custom two-part enclosure, machined from brass billet. The final enclosure included:

  • Thin, compressible RF seals between the enclosure components and the connector.

  • Openings in the enclosure that were sized to minimize RF radiation leaks.

  • Light pipes to transmit LED light from PCBA-mounted LEDs to the exterior of the enclosure.

• An assembly process to join the soldered PCBA, enclosure, and the RF connectors:

  • First, nickel-tin plate the interior of the enclosure to permit PCBA soldering

  • Drop the PCBA into the enclosure, solder-side down, aligning it with datum features inside the enclosure.

  • Assemble the connectors through the outside of the enclosure, screwing them to the enclosure and checking alignment with PCBA traces visually.

  • Apply a small amount of solder paste to the connector-PCBA joint by syringe.

  • Heat the PCBA-connector-enclosure assembly in a reflow oven and cool to join the components together.

  • Manually assemble the rest of the attenuator assembly.

• See below for renderings and early 2-D drawings of the assembly and its components.

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Gallery and Drawings Coming Soon!

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