Week 5
Electronics Production
Week Highlights
This week focuses on electronics production, covering PCB fabrication techniques, assembly processes, and creating functional embedded microcontroller systems. We'll explore both in-house production methods and board house services.
PCB Milling Design Rules
Characterize design rules for in-house production
Table of Contents
Course Content
Production Methods
Assignments & Projects
Electronics Production
This week we dive into the practical aspects of electronics production, covering PCB fabrication methods, assembly techniques, and creating functional embedded microcontroller systems. We'll explore both in-house production capabilities and board house services.
This Week's Goals
- Characterize PCB production process
Test design rules for in-house PCB fabrication and understand limitations - Design and fabricate embedded system
Create custom microcontroller board and test functionality - Submit to board house
Learn boardhouse PCB production workflow and design rules
Assignments
- Group Assignment
Characterize design rules for in-house PCB production process; submit PCB design to board house - Individual Assignment
Make and test embedded microcontroller system; extra credit for alternative process
Tools & Materials
- PCB Materials — FR4, FR1, Kapton, copper foils
- Fabrication Tools — CNC mill, etching chemicals, drill bits
- Assembly Tools — Soldering iron, microscope, flux, solder
- Testing Equipment — Multimeter, oscilloscope, power supply
PCB Fabrication Methods
Understanding different approaches to PCB production, from traditional etching to modern machining and boardhouse services.
In-House Methods
- Etching — Ferric/cupric chloride, ammonium persulfate
- Machining — CNC milling with 1/64", 1/32", V-bits
- Vinyl Cutter — Flex connections and encapsulation
- Laser Engraving — Combined LIG processes
Boardhouse Services
- Board Houses — JLCPCB, PCBWay, OSH Park
- Design Rules — 15/5 mil width/spacing
- Layers — 1, 2, 4+ layer options
- Assembly — Pick-and-place, reflow soldering
Assembly & Soldering
Essential techniques for assembling and soldering electronic components, from through-hole to surface-mount devices.
Soldering Techniques
- Manual Soldering — Iron station, fume extractor, microscope
- Reflow Soldering — Hot plate, convection oven, IR
- Hot Air — For SMD components and rework
- Wave Soldering — For through-hole components
Component Types
- Through-Hole — Traditional components with leads
- Surface-Mount — SMD components, smaller footprint
- Chip-Scale — BGA, QFN, CSP packages
- Headers — Connectors and interface components
Board House Services
Boardhouse PCB production services offer higher precision, better quality, and advanced features compared to in-house methods.
Popular Board Houses
- JLCPCB — Low-cost, fast turnaround, good for prototypes
- PCBWay — Professional quality, assembly services available
- OSH Park — Open source friendly, purple soldermask
- Aisler — European service, good for EU projects
Debugging & Testing
Systematic approach to troubleshooting and verifying electronic systems functionality.
Debugging Checklist
- Inspect and reflow solder joints
- Check component orientation and values
- Verify datasheet specifications
- Confirm connector orientation
- Measure supply voltages
- Probe I/O signals with oscilloscope
Training
Essential training materials and procedures for PCB milling using the Othermill machine.
Standard Operating Procedure (SOP)
Equipment Specifications
Pre-Processing
- Power on the machine using the rear power button
- Initialize homing sequence through Bantam Tools software
- Load design file: Export from Fusion as .brd (Eagle 9.x compatible) or generate Gerber files from fabrication outputs
- Configure hole types: Click PTH first; NPTH (non-plated through holes) requires edge cuts for proper origin alignment - process in second mill unless using vias for rivets
Workpiece Setup
- Activate loading sequence to position machine at front
- Remove magnetic panels and prepare workpiece area
- Apply double-sided tape across entire board surface
- Position board left-justified with 1mm buffer from origin
- Set Z-offset 5mm from origin point
Tool Configuration
- Add 1/64" end mill as secondary tool in tool list
- Install tool by aligning end mill shoulder with collar
- Select appropriate tool size and confirm installation
Milling Operation
- Install acrylic safety panels (required for operation)
- Verify hall effect sensor detects magnetic panel closure
- Execute "Mill All Visible" command to begin fabrication
- Monitor process completion (estimated 14 minutes to 2 hours)
Post-Processing
- Retract machine using loading controls
- Remove completed board from work area
- Clean debris using CleanView Deluxe vacuum system
PCB milling process using the Othermill machine
Reference Materials
Source: Original hand-typed training notes
Detailed training notes from MIT HTMAA Slack channel with comprehensive SOP and pro tips
Pro Tips & Best Practices
Design Optimization
- Single-sided boards: Prefer zero-ohm resistors over double-sided designs when possible
- Flexible alternatives: Consider vinyl cutter for translucent board applications
- Feature control: Toggle traces, holes, and outlines independently for selective milling
Workflow Efficiency
- Tool management: Store wrenches on machine tip; use left hand for small wrench operations
- Time estimation: Short jobs ~14 minutes, long jobs ~2 hours (automatic tool switching not available)
- Process monitoring: Time estimates are approximate; monitor progress manually
Advanced Techniques
- Solder resist: UV-cure solder resist available (process development ongoing with lab staff)
- Rivet alternatives: Avoid copper rivets (1mm/0.6mm sizes) - complex installation requiring conical hammering and dual-side soldering
Group Assignment
Characterize the design rules for in-house PCB production process and submit a PCB design to a board house.
Part 1: Design Rule Characterization
Comprehensive testing of in-house PCB production capabilities through systematic evaluation of trace widths, spacing tolerances, and mechanical durability.
Characterized Design Rules
4 mil (0.004") pre-test
9 mil (0.009") post-durability test
16 mil (0.016") minimum
Based on 1/64" tool width
Note: Design rules are guidelines; actual tolerances may vary based on material and process conditions
Durability Testing Results
Pre-test: Initial trace pattern
Post-test: Surviving traces after mechanical stress
Part 2: Boardhouse Submission
Evaluation of boardhouse PCB manufacturing services through JLCPCB submission to compare design rules, pricing, and production capabilities with in-house methods.
JLCPCB Submission Workflow
- Access JLCPCB online platform and create account
- Upload PCB design files (Gerber format)
- Select aluminum substrate (preferred over FR4 for machining compatibility)
- Configure production parameters and place order
Production Specifications
1.6 mm (standard)
Multiple colors (adds processing time)
Various options available
Individual Assignment
Make and test an embedded microcontroller system that you designed, with extra credit for using an alternative production process.
Project Overview
Design and fabricate custom embedded microcontroller systems using single-sided PCB milling techniques. Primary focus on ESP32-S3 based development boards with comprehensive testing protocols.
Development Sequence
- Phase 1: ESP32-S3 LED PCB - Basic microcontroller board with LED control
- Phase 2: ESP32-S3 LED Connector PCB - Enhanced version with additional connectivity
Functional Testing Protocol
Load Cell Integration
- Interface with load cell and amplifier board
- Design two-layer PCB with compatible header connections
- Develop data acquisition and processing code
Accelerometer Network
- Integrate accelerometer sensor module
- Establish wireless communication between ESP32-S3 nodes
- Implement data tethering and synchronization protocols
Advanced Manufacturing Exploration
Laser Cutter Application
Develop origami-style PCB design that mechanically activates LED through folding mechanism
Vinyl Cutter Application
Create flexible PCB using copper ring material for accelerometer integration
Useful Documentation
Essential resources and detailed guidance for electronics production processes and design rules.
PCB Fabrication Process Details
Source: Anthony Pennes - Slack Message
Detailed guidance on the three available PCB fabrication processes and design rules for successful board production.
Available Fabrication Methods
- Othermill PCB Mill — Preferred method, easiest to get started
- Roland SRM-20 — Runs through MODS interface
- Fiber Laser — Super small traces/spaces, single-sided only, no outlines/holes
Design Rules for Milling
- Trace Width: Keep traces big (>10mil), smaller traces should be kept short
- Spacing: Spaces should be larger than 16mil for reliable production
- Holes: Must be larger than 32mil for the bigger tool (slimmer tool not suitable)
- Vias: Use 0.9mm or 1.5mm holes for copper rivets, avoid holes under components
File Preparation
- Fusion: File → Export → Eagle 9.x compatible .brd file
- KiCad: Fabrication outputs → Gerber files (topcopper, edgecuts, holes, bot copper)
Post-Milling Inspection
Critical: Always perform optical inspection before soldering components. Look for stray copper strands and address them with light sanding, steel scraper, or utility knife.
- Check for copper strands and milling artifacts
- Clean up any issues before component placement
- Much easier to fix problems before soldering
Design Files
Links to design files, schematics, PCB layouts, and documentation for this week's projects.
File Formats
- Gerber Files — RS-274X format for PCB production
- Schematic — EDA tool source files and PDF exports
- Bill of Materials — Component list with part numbers
- Assembly Drawings — Component placement and orientation
Reflections & Learnings
Key insights and lessons learned from this week's electronics production work.
Production Process Insights
- Understanding the trade-offs between in-house and boardhouse production
- Importance of design rule checking and manufacturability
- Soldering techniques for different component types
- Systematic debugging approach for electronic systems
Contributions
Acknowledgements for help received during this week's electronics production work.
Lab Staff & Instructors
Thank you to the lab staff and instructors for guidance on PCB fabrication techniques, soldering best practices, and debugging methodologies.
Classmates & Peers
Collaborative learning with classmates on design rule characterization, component selection, and troubleshooting techniques.
Ethical AI Use
Transparent documentation of AI assistance used in this week's electronics production work.
AI-Assisted Week 5 Training and Assignment Updates
This week's training section and assignment updates were significantly enhanced by Cursor AI to transform hand-typed notes into professional documentation. The AI assisted with refining the SOP procedures, restructuring group assignment results, and developing comprehensive individual assignment plans with improved formatting and professional language.
AI-Assisted Content Refinement
Cursor AI helped transform informal training notes into professional SOP documentation, restructure design rule characterization results with improved visual presentation, and develop comprehensive individual assignment plans with clear testing protocols and advanced manufacturing exploration sections.
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