Hands-On PCB Engineering

Lecture 10:

Bringup

Week 11 Attendance on bCourses

Password:

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University of California, Berkeley

IEEE Student Branch

University of California, Berkeley

IEEE Student Branch

Logistics

• Project work time after lecture
• Project files due this Thursday (TONIGHT ) 11:59 PM - do not be late
• IMPORTANT: Make sure to have imported and ran the DRC rules we provide here to make sure your board is manufacturable
• Design reference: https://bit.ly/HOPE-reference
• Late-night Thursday OH: 6PM-12AM (midnight) in Supernode
• Don’t forget about our design reference here :)))))!!!!

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(Be on the lookout for announcements)

Either way ~time is of the essence~. Deadline will likely be Monday.

University of California, Berkeley

IEEE Student Branch

Final Project Showcase

University of California, Berkeley

IEEE Student Branch

Final Project Showcase

• Friday of RRR Week 1:50-4 PM, Cory Courtyard/ Cory 200
• Apple representatives will be listening to projects and asking questions
• EE/CS Faculty will be present and asking questions
• Great opportunity to
• Network and get in the pipeline for internships, full time opportunities
• Obtain research opportunities with EE/CS Faculty

(Be on the lookout

for announcements)

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University of California, Berkeley

IEEE Student Branch

Final Project

University of California, Berkeley

IEEE Student Branch

Final Project Submission

• Entire KiCad Project folder zipped
• Manufacturing Outputs (Gerber) separate (drill files too!)
• Check your Gerbers with the KiCad Gerber viewer
• Check on Instant DFM: https://instantdfm.bayareacircuits.com/
• Neat project BOM (separately uploaded)
• Use our exact format so we can make the Digikey order
• Put “0” for anything you don’t need us to buy
• For urgent, low-stock parts only - order NOW
• Anything else to help us understand your project

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University of California, Berkeley

IEEE Student Branch

One Last Announcement

University of California, Berkeley

IEEE Student Branch

Join HOPE Staff!

We are always looking for more HOPE besties! ��Get experience with: � - Teaching (looks great for course staff :eyes:)

- Tons of events (Makerfaire, Opensauce, Outreach) �- Become part of the “largest technical organization in �the world) �- Interest Form: http://berkie.ee/hope-staff-sp24

University of California, Berkeley

IEEE Student Branch

Final Project Urgent Parts

• For any projects that have at-risk parts (low stock) we will be making an early part order tonight; edit this spreadsheet
• This is only for LOW STOCK/CONCERNING parts!!!
• Save the rest of your parts for the normal project submission deadline

University of California, Berkeley

IEEE Student Branch

Recap

• Microcontrollers
• Basic introduction
• Communication
• Layout considerations
• Advanced layout
• Non-ideal passives
• This lecture: seeing if you applied this knowledge to make functioning boards

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University of California, Berkeley

IEEE Student Branch

Bringup Strategies

University of California, Berkeley

IEEE Student Branch

Bringup - Make it work basically

• Make board
• Assemble board
• Test board & components
• Test firmware
• Does the whole thing work?
• Repeat if it doesn’t

University of California, Berkeley

IEEE Student Branch

Getting a Board Out

University of California, Berkeley

IEEE Student Branch

You have your design… how to get it made?

• Steps:
• Choosing a place
• Verifying design passes the rules of the fab
• Exporting output files
• PCB fab places:
• Price comparison tool: https://pcbshopper.com/
• JLCPCB (cheapest), PCBWay (cheapest), OSHPark (hobby quality), Bay Area Circuits (not cheap, good for sponsored project teams)

University of California, Berkeley

IEEE Student Branch

Examples

OshPark (Purple PCBs w/ ENIG)

JLCPCB (Green w/ HASL)

University of California, Berkeley

IEEE Student Branch

Passing DRC

• DRC only works if you have the fab DRC rules set up correctly!
• Min track width/via diameter, min spacing, min non-plated hole, etc.
• Rules (and guide for applying them) posted in bCourses
• Design reference: https://bit.ly/HOPE-reference

University of California, Berkeley

IEEE Student Branch

Passing DRC

University of California, Berkeley

IEEE Student Branch

Attendance Question

What should you NOT do when setting constraints for DRC?

1. Set the appropriate trace width for certain net classes
2. Define a trace clearance consistent with the PCB fab’s requirements
3. Define a minimum silkscreen text width/height/thickness
4. Lower the requirements whenever an error occurs

University of California, Berkeley

IEEE Student Branch

Exporting for manufacturing

• Gerbers
• Most widely used format, set of files for different layers
• Drill files (.drl)
• Check export format required by fab house
• (There are better and more modern files…)

University of California, Berkeley

IEEE Student Branch

Exporting for manufacturing

Opens the window on the right

1

2

3

0: specify a folder e.g. gerber

4: zip the folder up

same folder here

Checkboxes MUST match

(NOT the same as default!!)

Checkboxes MUST match

University of California, Berkeley

IEEE Student Branch

Importance of BOM

• Maintain a neat and comprehensive BOM from the start
• Ease of double-checking footprints
• Ease of ordering parts
• Easy to reference during assembly
• For boards to be assembled by machine, a specially formatted BOM must be given to the PCBA as well

University of California, Berkeley

IEEE Student Branch

BAC InstantDFM

• Follow instructions to export and zip up the files
• Upload to here: https://instantdfm.bayareacircuits.com/
• Wait for results
• If all green: nice! You pass their DRC rules
• If not: the report should point out the place(s) with the error(s)

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Example Reports

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Testing

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Design For Test (DFT)

• Making layout decisions to facilitate easier board bringup/test
• Add features to facilitate testing:
• Test pins, LEDs, jumpers, test points/hooks, and standard interfaces
• If your board ends up not working, did you add features to make it reconfigurable?
• Breakout extra pins from microcontroller, jumpers to disconnect sections, etc.

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University of California, Berkeley

IEEE Student Branch

Board Basics Check - use your eyes

• Are there any obvious problems with the board?
• That aren’t your own fault, but check for those too
• Undrilled vias, severe soldermask misalignment, pad or trace shorts, extra traces/traces missing
• Mechanical: board edge tolerances, mounting holes
• These are unlikely, but best to check anyways
• Before assembly, harder to check after

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University of California, Berkeley

IEEE Student Branch

Board Basics Check - use your eyes

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• After soldering / component assembly
• Are there any shorts or misaligned component leads?
• Watch out for floating components and/or solder globs
• Are any components oriented incorrectly? (diodes, ICs)

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IEEE Student Branch

Unit Tests

• Testing part by part
• Hardware: Assemble functional blocks independently
• Also make sure fundamental operation is correct, not burning up, etc.
• Firmware: Upload software tests for one feature at a time
• Independently test each block (as much as possible)
• Add another module once the previous one works properly
• Unit testing is easier for debugging
• Will help you decouple errors
• Makes board bringup faster

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Order Matters: a sample plan

1. Power
1. Supply power from power supply and test regulator voltages
1. Upstream regulators before downstream ones, if applicable
2. Test regulators with electronic load or resistors
3. Test protection like reverse polarity, overcurrent, etc.
2. Microcontroller(s)
• Use power from supply or regulators to test basic MCU functions
• Basic interfaces: UART, USB, SWD/JTAG if applicable.

University of California, Berkeley

IEEE Student Branch

Order Matters: a sample plan

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• Other ICs / functional blocks
• With MCU and power, test serial interfaces like I2C, SPI, I2S, etc.
• Test ICs like sensors, motor controllers, etc.
• Overall functionality
• Integrated tests with multiple subsystems running concurrently
• Coexistence issues: e.g. does power circuitry produce noise on signal lines?
• Put board in its final application and validate functionality

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IEEE Student Branch

Making Measurements

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Making Measurements

• Precision, accuracy, reproducibility
• Availability of equipment
• Measurement time
• Using equipment correctly

University of California, Berkeley

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Power Supply

• Configurable voltage, current supply
• Limited voltage range and current handling
• Limited meter accuracy
• Current limit handles startup transients poorly
• (You set a current limit, didn’t you?)
• Power supply noise, decoupling
• Grounds are not connected

University of California, Berkeley

IEEE Student Branch

Oscilloscope

• Plot voltage over time
• Probe has a signal and ground contact
• Signal/ground is not interchangeable!
• Limited bandwidth
• Horizontal/vertical scale, triggers, measurements
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University of California, Berkeley

IEEE Student Branch

Oscilloscope

• Check probe compatibility
• Probe impedance
• Probe compensation
• Probes also load sensitive circuits
• Current probes, active probes, diff probes

University of California, Berkeley

IEEE Student Branch

DC Voltage

• Connect all grounds properly
• Measurements could disturb circuit
• Large, finite input impedance for voltage measurements
• Probe capacitance could destabilize control circuits
• Checking power supply DC voltage is not enough!
• Won’t catch rapidly excessive ringing or oscillation

~20 us

60 Hz noise

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DC Current

• All the DC voltage caveats apply
• Current could be significant → resistive loss
• Important for current sense resistors or sensitive supplies
• Current density
• Exceeding current limit will blow fuses
• Good to have fuses!

University of California, Berkeley

IEEE Student Branch

Passive Measurements

• Use ohmmeters on disconnected components only
• Ohmmeters apply a voltage (up to 5 V!) to components, then measure current (or vice versa)
• Could turn on/damage parts of your circuit
• In some cases this simply isn’t a safe option
• Digital multimeter (DMM)
• Voltage, current
• Capacitance
• (Inductance) - LCR meter

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University of California, Berkeley

IEEE Student Branch

4-Wire Sense

• Use 4 wires, not 2, to make impedance measurement
• Two provide a current source, two measure voltage
• Combined source measurement units (SMUs)

University of California, Berkeley

IEEE Student Branch

Attendance Question

Select all the tools used for testing and measurement

1. Oscilloscope
2. Multimeter
3. Power Supply (make sure to set a current limit!)
4. Your fingers to feel if the IC got too hot (don’t select this one)

University of California, Berkeley

IEEE Student Branch

Board Basics Check - X-Ray / CT

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• Only relevant for professionals and industry, but know this is possible. Especially useful for internal layers / traces.

University of California, Berkeley

IEEE Student Branch

Automated: Flying Probe Testing

• Exposed pads make great automated probing points
• Automated process use flying needles to check for correct connectivity, functionality, and more

University of California, Berkeley

IEEE Student Branch

Lab

• Project files due this Thursday 11:59 PM

Reminders:

• Attendance
• https://ieee.berkeley.edu/hopeforms/

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University of California, Berkeley

IEEE Student Branch