Transition Board Redesign aka: The Connector Project Project Manager: Ashley Walker Teammates: Brad Westgate and Bryn Hollen NASA Mentor: Dr. F. Scott Porter Advisors: Dr. Steve Holt and Dr. Brad Minch With thanks to: Eric Gallimore

Transition Board Redesign –Design Goals Include impedance matching resistors Add ESD protection components Minimize board size Assembly Our Task Build interface boards between the detector first stage amplifiers and the dewar wiring

The Current Board Current Set-up Nanonics connector –Connects the signal harness and the JFET box Transition board –Connects to the dewar harness board Using DB62 connectors Dewar harness board –Fan-out board for the 28 pair ribbon cable, serving as the main harness inside the dewar –Runs from the 4K helium tank to the 300K hermetic connector, leading to the outside world MDM-51 right angle PCB connector –Shown for reference

Why A New Board? The 62 Pin DB connectors limit board size minimization ESD Problems –JFETs are sensitive to appx V of discharge Several FET’s blew out on the flight instrument To replace the FETs the whole assembly must be replaced, costing $50,000

Transition Board Redesign Board A: –Interface dewar twisted ribbon cable to MDM-51 connector Board B: – Interface JFET cable, which is terminated in a nanonics-55 pin on the JFET box at 17K to the MDM-51 of board A –Use MDM-51 connectors on both sides

ESD Overview It’s shocking stuff –Transient current flow compensating charge imbalance between bodies, i.e. a shock –Example: lightning Same phenomenon can occur on a smaller scale during handling of integrated circuits –Can be destructive if no protection exists Average losses in manufacturing to ESD “between 8-33%” Models of ESD –Human body model (HBM) –Machine model (MM), etc, etc.

Protection from ESD Zener diodes TVS diodes Ceramic Capacitors Schottky diodes Multilayer varistors

Multilayer Varistors Why? Perform at high voltage levels Low break down levels Available in surface mount packages In stock!

Revenge of EDS

Impedance Mis-Match Some of wave energy is reflected How much? –Part of this week’s lab General principle: –“Impedance Match” to get best energy transfer Similar to impedance match idea of compartment systems (Remember This?- Thanks Gill)

Transition Board Redesign Our Remodeled Circuit Boards

Board B Layout ESD and impedance board Two-layer board Top layer connects resistors and diodes Bottom layer goes straight through Diodes all need to have a common drain, so they are connected between the resistor pads (thanks, Brad Minch)

Gerber Top layerBottom layer

Bored A Layout Connects the connector and the ribbon cable Ribbon cable is untwisted and soldered on to a bunch of tiny pads (by some hapless NASA intern) Signals must be laid down in order, hence the diagonal layout

Gerber Top layerBottom layer

What are we up to next? Wait for boards to arrive Practice playing with solder When the boards are complete: –Test the connector boards in cryogenic temperatures Most contraction occurs between room temperature and liquid Nitrogen temperature

Dragons slain Gold Plating of boards –Led to redoing the boards and learning new software Getting a Custom Quote and Ordering Boards