Printed Circuit Board Design LIN155 PDF

Printed Circuit Boards LIN155 – Electronic Lab & Instrumentation Techniques School of Electronics and Mechanical Engineering Technology (SEMET) Textbook references: Chapter 5 p. 80 Chapter 15 p. 297-301 Agenda Types of PCBs History of PCBs Structure of PCBs...

Printed Circuit Boards LIN155 – Electronic Lab & Instrumentation Techniques School of Electronics and Mechanical Engineering Technology (SEMET) Textbook references: Chapter 5 p. 80 Chapter 15 p. 297-301 Agenda Types of PCBs History of PCBs Structure of PCBs Types: Pin Thru-hole vs Surface Mount Single- vs Double-sided PCBs PCB Design in Software Using Fusion to Create Schematics and PCBs PCB Printing Lab Requirements PCB Design Tips Instructor Demonstration 2  Types of Circuit Boards Bread Board Strip Board Printed Circuit Board Test board for Copper strips run Designed specifically for a building temporary parallel to each other, circuit, generally for mass and experimental soldering required. production. Tracks or circuits. No soldering Crude replacement to a “traces” are covered with insulating materials, and required. PCB for testing or soldering occurs only on emergency. exposed copper pads. Image source: https://cdn-learn.adafruit.com/assets/assets/000/002/602/medium800/learn_arduino_breadboard_half.jpg Image source: https://www.instructables.com/Practical-Circuit-Construction-With-Strip-Board/ Image source: https://stapulawski.files.wordpress.com/2017/04/pcb-001.jpg 3 History of PCBs 1903 – Concept: Use flat foil connectors laminated to an insulating board in multiple layers (Albert Hanson) 1904 – Experiments: Plating conductors onto linen paper (Thomas Edison) 1913 – Patent: Print-and-etch method (Arthur Barry) 1913 – Patent: Flame-spray metal through patterned mask (Max Schoop) 1927 – Patent: Electroplating circuit patterns (Charles Durcase) 1936 – Concept: Use etched foil to lay down traces on a substrate (Paul Eisler) 1943 – Eisler applied for patent. No-one was interested… … But the U.S. incorporated this new technology into WW2 “proximity fuses” and mandated it for all airborne circuitry. PCBs slowly grew in popularity (preference for by hand) 1948 – The U.S. released the invention for commercial use. 1950 – Patent: Eisler’s split into 3 and finally published. Image source: https://en.wikipedia.org/wiki/Paul_Eisler#/media/File:Paul-eisler-by-maurice-hubert.png Paul Eisler 4 PCB - Structure – Mechanical Insulating or “dielectric” layers are laminated together Dielectric typically made of polytetrafluorethylene (Teflon), woven glass, and epoxy (FR-4, most commonly used in industry) Gives circuit supportive structure, & insulates between all components Image source: https://www.circuitwork.tech/pcb-circuit-board-structure/ Image source:: https://www.gadgetronicx.com/multilayer-pcb-explained/ 5 PCB - Structure – Electrical Conductive pathways are tracks or “traces” for connections Connections typically made of thin copper foil Thickness specified in ounces per square inch, or micrometres Coated with a protective solder mask (green, blue, red, black, white) Image source: Stock image Image source: https://www.pad2pad.com/images/colorful_pcb.jpg 6 PCB – How is it made? Additive – no copper on board, added with printer Subtractive – copper covers board, etched away (chemicals or router) Image source: https://info.elephantech.co.jp/en/p-flex-fpc 7  PCB – Types – Pin Thru Hole Component leads are inserted into holes drilled into the PCB and soldered on the opposite side Image source: https://upload.wikimedia.org/wikipedia/commons/2/21/Through-Hole_Mounted_Component.svg Image source: https://cdn.shopify.com/s/files/1/1126/9610/articles/Through_hole_soldering_grande.jpg 8 PCB – Types – Surface Mount Components sit on one side of the PCB and are soldered to flat pads on the same side Image source: https://www.circuitrework.com/guides/7-3-1.html Image source: https://marketbusinessnews.com/surface-mount-pcb/211810/ 9 PCB – Sides – Single “Single-Sided” PCB Mounted Side – the side with the components and silkscreen writing Solder Side – the side with the copper pads, traces, and solder joints Image sources: Velleman MK137 PCB from LIN155 kit, photos used with permission, K.Craigs. 10 PCB – Sides – Mounted Side Version Info: - Can write words in ink PCB Decal: (or on the metal layer) - Part outline in ink - Drill holes for pins - Reference Designator No Metal Only components are mounted on the “Top” side. Board Outline: - Design boundary Drill Holes: - Keep all parts inside! - For screws or standoffs Image source: Velleman MK137 PCB from LIN155 kit, photo used with permission, K.Craigs. 11 PCB – Sides – Solder Side Copper Trace: Copper Pour: - Connections between - Can be a ground plane component pads Copper Pad: Metal Traces - Surrounds drill hole, All soldering is for soldering part lead done on the “Bottom” side. Green Solder Mask: Manufacturer Info: - Covers any copper in - Write words in metal insulating material then cover in mask Image source: Velleman MK137 PCB from LIN155 kit, photo used with permission, K.Craigs. 12 PCB – Sides – Double “Double-Sided” PCB Traces, solder masks, silkscreens and components are placed on both sides Side 1 Side 2 Image source: https://othermachine.co/assets/dsbetaimage07.jpg 13 Schematic/PCB Programs Are any Free to use? Are there Student versions? Some for Limited use? LTSPICE, SmartDraw, ExpressPCB, Eaglesoft, Creo Schematics, more At Seneca, we use software that you will likely find in your next workplace. AutoDesk Fusion A 1-year renewable free trial is available for students who create an AutoDesk account and upload proof of their status as a student (e.g. submit your student timetable) 14 Fusion: Design Schematic, then PCB, then Export Files In Schematic mode (saves as a.sch file): Add parts to the design by searching and selecting each one from the library Connect the parts using the Net tool, to indicated where in the traces will go Run the ERC to check for errors and fix them before continuing In PCB Layout mode (saves as a.brd file): Set the Design Rules first – see next page for hints Set the board outline dimensions Place the parts within the board dimensions in their desired locations Replace all schematic nets with physical copper traces on the board Add text to the silkscreen layout to indicate name, revision, etc. Run the DRC – Design Rules Check – and fix any issues before continuing Getting the files ready to send to the PCB Printing Lab: Export the manufacturing files, also called “Gerber” or “CAM” files (many files saved!) Collect all Gerbers plus the original schematic and PCB files together in one place 15 How to Meet the PCB Printing Lab’s Requirements Set up tolerances in software to match our PCB Printing Lab requirements! Latest requirements are always posted on the website. See also Lab 8. Summary of what your PCB layout should have: Don’t have large open spaces around the board (it’s a waste of material!) Look up your course code to see what MAXIMUM* area you can use *Make the board area smaller, if you can In DRC†, change the Clearance, Sizes, Annular Ring, and Supply tabs †You need to fully understand the effect of each of these in your design If the DRC (Design Rule Check) fails, the PCB Lab cannot print your board 16 PCB – Design Tips Designers often reserve space on the board to mark information. eg. the assembly name, part number, and revision of the board. Efficient use of space on the board leads to cheaper assemblies (boards, components, and process time), and is also more sustainably conscientious. Keep orientation and spacing consistent on entire board. This will reduce time for placement and during the inspection process. eg. Use symmetry and balance when placing similar components. 17 PCB – Design Tips continued Consider the height of the components in your placement. eg. Avoid placing an IC in between tall connectors or capacitors. Surface-mount is generally cheaper than thru-hole. Try to avoid sockets on production SMT boards to reduce costs. Image source: https://www.proto-electronics.com/blog/best-rules-for-pcb-components-placement 18 Instructor Demonstration In-Class Demo to show Fusion Schematic and PCB Design Open MyApps. Launch Fusion. Walk through a simple demo Reminder: Full details are described in Lab 8. Try this ahead of your lab. 19 Questions 20 Works Cited History of Computers and Computing: http://history- computer.com/ModernComputer/Basis/ Wikipedia: http://en.wikipedia.org/wiki/Printed_circuit_board 21