Techniques

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Contents

Printed circuit board design/fabrication

Overview

Software Design

see Software design tools below, this should be a link, but I do not know how to do it yet, someone want to fix it for me?

Manual Design

Somepeople do this with layout on clear film or by directly drawing on a circuit board, of even by scratching, grinding.... For now let them google this.

Homebrew fabrication

  • Toner Transfer -- This method involves laser printing your PCB design onto paper, then transferring toner onto copper-clad board.
  • Photoetching -- Exposure of PCB designs onto photosensitized copper-clad board.
  • Chemical Etchants

Commercial PCB fabrication

Circuit construction (Prototyping - Other than custom PCB)

["Construction Ideas"] has nice photographs of the above circuit construction techniques.

Soldering techniques

(Have you seen this CNC solder paste/pick n place ?)

Hardware Tools

A directory to tools that you may find useful.

Software design tools

Some people still build circuits without ever using any software tools. For complicated circuits, software design tools can save a lot of time.

Here we list "suites" that combine schematic capture, component editor for the components used in schematic capture, circuit simulation, PCB layout, autorouter, and footprint editor for the footprints used in PCB layout. (Is there another place for listing stand-alone tools such as a switching power supply "wizard" and a RF analysis tool?)

Quite often people mix-and-match tools -- using a schematic capture from one suite to generate pretty schematics and a netlist, then importing the netlist a third party Specctra autorouter, then importing the result into a PCB layout program from another suite for the final manual clean-up and design rule checking.

In no particular order:

Name Platform License AutoRouter Comments
Liquid PCB GPL Liquid PCB wiki at SourceForge Liquid PCB is a computer aided design application for designing printed circuit boards. You are not restricted to straight tracks and 45º angles, you can draw tracks any way you like. The tracks will move and bend as required to maintain your design rules. It is open source, and still in the Alpha stage.
gEDA Linux, *BSD Free, OSS gEDA wiki includes schematic and PCB for makeing gerbers etc...
McCAD EDS Lite Free demo max 200 pin Free demo version available for download, 200 pin limit
McCAD EDS SE "free"? Free book, "Apple I Replica Creation". Supports 750 pins, 11"x17" sheet size, 6-8 data layers. <tangent>(any useful tips in this book for those who want to build a CPU from scratch?) <reply>No, there are not. The book is more entry-level. - Tom Owad</reply></tangent>
FreePCB Win32 Free, OSS? PCB Design Software
TinyCAD Win32 ? Schematic Drawing Software
KiCad BSD, Linux, MacOSX, Win32 GPL http://www.lis.inpg.fr/realise_au_lis/kicad/ EDA suite
Express SCH/PCB Win32 Free use crippleware ExpressPCB's propietatary free schematic capture & PCB layout designer locking you to use ExpressPCB for manufacture explicitly. Manufacture in 3 business days of two boards for ~100 USD.
Protel DXP independent Protel users FAQ
Eagle Eagle Links Win32, Linux Free use crippleware ( Russ Hensel says>> ) I have been kicking around as a hobbyist for a while and Eagle seems to be the main hobbyist circuit/pcb cad program. It supports schematics and board layout with an auto-router. The free version can easily support 2 dual op amps with wide traces and a one sided board. There is quite a lot of info on the Internet and many projects supply eagle files. There is also a $125 non profit version supporting larger boards. It then gets expensive. Eagle is not really easy to learn: cut for it would be copy in almost any other program. It probably deserves a page or more of its own. ( << end RH )
http://cadsoft.de/
Eagle tutorial from Sparkfun
Eagle tutorial (makezine)
DipTrace Crippleware 250-pin Freeware or Purchase more advanced versions
WinQcad Crippleware Demo with max 499 pins available for download
Rimu Schematic and Rimu PCB Win32 Payware Schematic & PCB design for MS-Windows
SuperCAD and SuperPCB Win32 Mental Automation schematic & PCB for MS-Windows
autotraxeda.com AUTOTraxEDA needs MS-NT, won't work on MS-W98/ME. User forums have shown a certain lack of satisfaction with the program.
holophase.com/dleval Win32 Crippleware Circad's DOS version is free for non-commercial use.
geda.seul.org BSD, Linux, MacOSX, Win32 GPL Yes xNIX Electronic Design Automation project has Schematic capture with PCB CAD.
vutrax.co.uk/pricing Win32 Vutrax for MS-Windows. Free for under 256 component pins.
interactiv.com Electronic Workbench, 400 USD for 500 pins. Includes schematic capture and simulation, virtual instruments and PCB layout. Said to be stable.
Harry Eaton's PCB GPL? Yes PCB design program which can work under any POSIX compliant operating system like Linux (or BSD under API compability layer). Have Gerber and PostScript output options.
labcenter.co.uk They have a lite version "PIC bundle" ~149 USD includes schematic + simulation + pcb layout. You can write pic code for your pic schematic design and simulate. Even multi-pic, keypad, lcd display. Right now it can only simulate PIC16x83, PIC16x84 (lite version limited to 1k program code). Working on more pic modules. Will not produce Gerber or Excellion drill files. Only dxf, bmp, hpgl, tiff output (not sufficient!).
ivex.com Payware Winboard PCB Layout, now calcentron.com.
illuminated.com.au Linux, Win32, DOS Draftcad, Schematic Capture and PCB Design
winqcad.com Win32, Linux+Wine MicroCad

(Some of this information in this table came from the list of software design tools at the Massmind).

Is there any way to objectively compare these tools? How well did they do at the PCB Top Gun contest ?

Checklist for "The flow of PCB fabrication/PCB" using Software Design Tool

  • Format and shape of PCB are conformed./
  • Via size and location are conformed./
  • Fixed location item are placed on suitable place./
  • A one-first PCB silk layout is made./1:1的PCB
  • All item get enough clearance between them./鄰是否過於緊貼
  • All vias get enough size to install them components./求
  • Make sure no worng footprint is created./
  • PCB is drew./PCB
  • Netlist is ran and got a no error result./執行netlist指令直無錯誤
  • DRC is ran and got a no error result./DRC
  • Location of item is reasonable./
  • All items are put on to a hard copy of PCB./PCB
  • Overall is checked./

And then the Gerbers are sent to a PCB Manufacturers.

Serial Communications from a PC to Microcontrollers

This is often done using Hyperterminal ( a program bundled with MS Windows ) to communicate with the microcontroller using RS232 or virtual RS232 over USB. This program is pretty painful to use, we should list some alternatives to it here. This is just a start:

Program Source/Comments


RS232/USB Probe RS232/USB Probe Now in testing, a specialized program for microcontroller communication on the PC side.
R. E. Smith I/O Commander From the site:

The I/O Commander is designed to communicate, test and control our line of digital and analog I/O products. However, due to its flexible nature, it can also be used as a general purpose terminal emulator (color coded TXD/RXD, split screen modes, and 32/1024 "hot-keys") and, as a drum sequencer. The terminal emulator now supports COM1 through COMX, and data rates from 300bps to 921.6Kbps. Now with flow control and parity. Same low cost: Free

PIC Chip Communication with a PC Date on this is 2001, does it still run?
Tera Term Home Page From the site:

last updated: Aug. 9, 1999 Tera Term (Pro) is a free software terminal emulator (communication program) for MS-Windows. It supports VT100 emulation, telnet connection, serial port connection, and so on.

( for the search engines: dump HyperTerminal find a better communications program )


For some notes on how to plan the microcontroller end of the communications see: RS232 and for a particular implementatation take a look at BitWacker PIC USB Development Board and the specialized PC program for it and similar devices: BitWacker Java Communications

For general information on terminal emulators see: Terminal emulator From Wikipedia, the free encyclopedia

Embedded System Programming and Testing

  • Many systems use JTAG for programming and testing. (Such as Atmel AVR embedded systems]).
  • Other systems use some other kind of in-circuit programming.
  • Some people use bootloaders to make re-programming a little quicker.

Enclosure

  • The Earth Signal should short to whole metal Case
  • Digital/Analog GND should separate to this Earth Signal, and should connect a Y-cap. to filter the noise between them.
  • Attention: do not place near between Earth Signal and Digital/Analog GND, otherwise some spark come out, and affect your whole system.

Further Reading

Environmental Issues

The metals, chemicals, and polymers used in producing electronic circuits, as well as the energy consumed in producing them and the extraction (mining) processes can have significant environmental impact. The purpose of this section is to collect information that can be used to assess and/or mitigate the environmental impact. It may also suggest some projects which can be environmentally beneficial. [Note: techniques was the closest major section to incorporate this into but it might make more sens to promote this section to a fifth major section]

Energy Use, Global Warming Gasses

Embodied Energy/CO2

With the climate change crisis and peak oil, energy consumption becomes an important issue. Embodied CO2 includes the effects of emboddied energy plus other CO2 sources. An good source for information on how much energy is consumed and CO2 produced in making a variety of materials is the ICE [1] database. You have to request a free copy be sent via email. The production of metals and plastics releases many times their weight in greenhouse gases.

Energy consumption by Electronic Devices

Standby modes, switching supplies, etc.

Transportation

Raw materials, electronic components, bare PCBs, finished products, and end-of-life products being recycled get transported very long distances.

Electronics as energy saving devices

Some electronics are used to save energy. Fluorescent ballasts, Photovoltaics, power inverters, charge controllers, some motor controls, solar trackers, LED lighting, setback thermostats, motion sensor controls and timers, blind controllers, etc. In some cases, computers are used for telecommuting.

RoHS/lead-free

The transition to RoHS/lead-free processes has cost the industry a large amount of money and creates problems for hobbyists. When you consider the environmental impact of lead free solders (for example, silver mining is highly polluting), and the greater amount of non-renewable resources used, and the shorter lifespan of the electronic circuits, the whole lead free movement may be yet another political boondoggle. [2]

John Barnes, electronics text book author, and author of the Pushback site:

It is widely accepted in the Engineering community that the recent ban of lead in solders for use in electronics in Europe is not only erroneous, but will actually lead to a worsening situation on the environment with the replacements being in general use from July ’06 having a GREATER environmental impact. [3]

To date I have collected over 230 books and well over 11,100 other documents on these and closely-related subjects, going clear back to 1851. My collection now fills one-and-a-half bookcases and three 5-drawer file cabinets. [4]

Based on my research, and helping clients develop RoHS-compliant electronic products, I believe that: If you buy a lead-free RoHS-compliant electronic device-- and if it works when you first turn it on-- it should be safe and fully-functional for at least one year. If you are lucky, it may last a couple of years longer... versus the 20+ years use that we can easily get out of many lead-based electronic products. [5]

[6]

A huge problem with the RoHS laws is the sheer nitpicky nature of the regulations and the beaurocracy that enforces them. It doesn't matter if you reduce the lead content a thousand fold relative to a lead solder board, which would put it well within the 0.1% lead limit. The product is reduced to homogeneous parts each one of which must individually meet the regulations. One stray microscopic lead solder ball might be ok if it is absorbed into a joint where it is becomes part of a larger homogeneous component but not if it contaminates an inspection sticker or gets trapped in the flux between traces. Maybe widespread competent recycling of electronics is a better approach. Not shipping it off to other countries or using prison labor to disassemble it under unsafe and environmentally harmful ways; there are some horror stories of how electronics is recycled now.

Mixing lead containing and lead free components

Many lead-free components are compatible with lead solder processes. leadframe based components, such as QFPs, SOICs, and SOPs with gull wing leads, are generally compatible since the finish on the part leads contributes a small amount of material to the finished joint. However, components such as BGAs which come with lead-free solder balls are not compatible with lead processes. [7] Also, leadless parts are exposed to higher stresses and are more susceptible to any affect from mixed metallurgy. Check with each manufacturer as lead finishes may vary.

[edit]

Materials, Chemicals, and Processes used

Etchants

Ferric Chloride poured down the drain will eat pipes and copper is toxic. Although your sewage plant may not be happy about ferric chloride in the sewage (and it may be illegal) , they can probably at least deal with it better than many other chemicals since Ferric Chloride is used at sewage treatment plants to remove copper. Ferric Chloride etchant can be neutralized into iron oxide (rust), copper, and salt by using iron (nails, etc) to use up all the etchant and then add washing soda and evaporating and can then be landfilled. Considering the value and toxicity of copper, it would be nice to see this improved on so that the copper can be reclaimed.

Another source [8] suggests adding washing soda before pouring down the drain. Another source [9] suggests baking soda.

MSDS

Etching can be improved, and the lifetime of the etchant before it needs disposal, using citric acid [10]

PCB Substrates

Etch Resists

Solder

See RoHS/lead free section above. Solder paste should be refrigerated (embodied energy) and has a limited lifetime. One problem with expired solder is absorbed water which can lead to spatter and voids in solder joints. What to do with expired solder paste? It should still be ok for manually tinning leads and large copper areas. It may be possible to add it to a wave solder bath using the same alloy.

Flux

Epoxies

Solder Mask

Silk screen

Tape & Reel, JEDEC matrix trays, other component packaging

JEDEC matrix trays can be reused or recycled. Resistors tend to come in paper (cardboard) tape, which can be recycled, plus a cover tape. Capacitors, transistors, and IC's often come in formed plastic tape with a plastic cover tape..

poly bags

Cleaning products

Plating =

Tin Plating
Gold Plating
Nickel Plating
Silver Plating
Hot Air Solder Levelling

Not technically a plating process, but many of the alternatives are. Contains Lead (see RoHS/lead free section).

Solder Mask over Bare Copper (SMOBC)

Copper

Sulfur dioxide produced in making copper is equivalent to 1/4 the sulfur dioxide emisions of all industrial nations combined. 1kg of copper requires excavating 127kg of ore and 136kg of other rock and the equivalent of 275 liters of petoleum was consumed. [11] Copper is somewhat toxic. And it is a scarce and valuable resource. Copper prices are high enough that people steel copper wiring and pipes out of unoccupied buildings (destroying the buildings in the process). Copper can be recovered from PCB etchant by electrolysis. [12] It also saves on etchant replacement and disposal. They spent 55,000 English Pounds to set it up but it paid for itself in two years. This may be possible to do on a smaller scale. Copper used on printed circuit boards is usually produced by electrodepositing copper onto a rotating drum (Printed Circuits Handbook); this particular process, though often done by the panel manufacturer and not the PCB fab, appears to be compatible with reclaimed copper (no need to remelt it). It appears that electrodes used in the reclamation process can be transfered to the plating bath for panel plating, pattern plating, or making electrodeposited foil sheets, provided the baths are kept well filtered. In a double sided circuit board, most of the copper on the board is electroplated onto the board (starting with a thin foil), thus plating the holes.

Aluminum

Tantalum

"Other concerns we have center on a material necessary for wireless technology, called Tantalum. Tantalum is a rare earth metal that is only found in a few places. Because of growing demand caused by the popularization of cell phone, laptop and wifi use, tantalum mining has become a lucrative business in areas that sometimes have delicate ecosystems and unbalanced economies. This led to wars, exploitation and environmental havoc in the Congo³. That situation has been mostly addressed through policing and international embargoes4, but that is just one example of how consumer electronics can be linked directly to environmental and social problems.5" [13]

PVC

PVC is used as insulation for wires. Flexible Vinyl contains plasticizers which can be toxic and are banned in some countries. Hard Vinyl is safer. There are other plastics, such as LDPE, which do not require plasticizers for flexibility and materials such as silicone rubber which make superior insulation.

Teflon

Used as a PCB substrate, dialectric, wire insulation, and as a non-stick coating on cookware. Teflon wire releases nerve gas when burned. Teflon cookware (which may be used in the hot plate or toaster oven methods of reflow soldering) is alleged to release nerve gas fumes that will kill pet birds even at normal cooking temperatures.

Silicone Rubber and other Silicones

Silicon is an abundant natural resource. Silicone Rubber has a 50 year life span, which makes it good for durable goods. It is considered by some to be more environmentally benign than many other polymer resins due to its durability, low toxicity, manufacturing process, being chemically inert, and abundant raw materials. Another Silicone, Silicone gel, was vindicated as a cause of health problems associated with breast implants. Silicone rubber is one of the few materials considered safe enough for medical implants. It is an excellent high voltage insulator and withstands high temperatures. When used in contact with electrical circuits, peroxide curing vs. acetic acid (vinegar) curing silicone should be used due to the corrosive nature of acetic acid. Silicone caulk may be thinned to make it suitable for painting or dip coating, when the proper forms of the resin are not available, using Xylene (a hazardous material) or pourable silicones or other silicones without thixotropic additives may be used, though these are expensive in small quantities. Silicone rubber may be used as an adhesive (it must be cut to remove it). It may be used as a potting material. Silicone oil is used as a lubricant; purists prefer pure silicone lubricants (such as CRC 100% silicone) over products such as WD-40 which mix it with petroleum based oils; do not use it on a surface you intent to paint. Paint does not adhere to silicone rubber, either. "Paintable" silicone rubber caulk appears to lack the thixotropic additive and is thin enough to spread with a paint brush, though probably not thin enough for dipping or pouring. Liquid silicone may be used as a non-toxic solvent. Availible in electrically conductive varieties. Silicone is used to make flexible molds and hobby moldmaking suppliers are a source of small quantities of different types of silicone rubbers. Silicone rubber will withstand reflow soldering temperatures; it could be used to adhere components to a board before soldering, however it will not let go when you attempt to desolder the parts. [14]

Wood

Can be used for breadboarding leaded components, enclosures, etc. Low embodied energy/CO2.

Stencils

Panel Plating vs Pattern Plating

[15]

Chemical Etching vs Mechanical Etching

Fumes

Soldering (flux)

Laser Cutting (stencils, engraving, via hole drilling)

Chemical Etching

Enclosures

Recycling

Electronic Equipment

ReHDPE

Recycled polyethylene lumber (ReHDPE) (Not the kind with wood fillers), seems to machine well, is cheaper than delrin and other plastics. Wood fillers in the sort found at Lowes Hardware stores may absorb water. At least I think the sample (from teksupply) I saw was ReHDPE; they don't say but similar products seem to be ReHDPE. There may be voids. 2x4 material (many sizes available) is about $3 per foot. [16] [17] [18] May be useful for electronics enclosures and other plastic parts. HDPE has a lower embodied energy than most plastics.

Obsolescence

The enviromental impacts of electronic devices are greatly exacerbated by obsolescence (or worse planned obsolescence), limited lifetimes, and poor repairability (including lack of technical documentation), and by often being cheaper to replace than repair.

Single Function vs. Multifunction devices

Devices which perform many functions, and thus replace many devices, may reduce environmental impact. Do you need a computer, TV, stereo, CD player, DVD player, game console, DVR, VHS/DVD recorder or can you use one device (the computer) for all those functions? Do you need separate PDA, GPS receiver, digital camera, camcorder, cell phone, DECT cordless phone, voice recorder, MP3 player, and ebook reader or can those be combined into a single portable device that functions better than the individual devices?

Components

= semiconductors

The embodied energy in a Monocrystalline solar panel, 230Kg CO2/square meter might be a some indication, though that is for the module and not just the cell and it is based on a square meter rather than by weight as most things are, but it seems rather high (they do, however, repay that energy in about 18 months to 7 years). 60% of the embodied energy is in the silicon wafers. Pound for pound, semiconductors are probably an environmental nightmare, though very little material is actually used in the final product. Unfortunately, a 2g chip (32MB DRAM) requires 1.7kg of materials (72g of chemcials, 1600 grams of fossil fuels, and 700 grams of elemental gas) and uses 32000g (32 liters) of water. A lot of this energy is too heat the materials to 1000 degrees Celsius (how about a large concentrating solar collector to help out here?).

Resistors

The process of making resistors generally involves baking (embodied energy/CO2); probably twice, once to make the ceramic subtrate and once for the resistive coating; however, this is probably not a major concern as ceramics have a fairly low embodied CO2.

Computers

Computers have a very large environmental impact and may be indicative of the environmental impact of electronic devices in general. For a computer, the emboddied energy is about twice what it will consume over a three year life span.

For a desktop computer (not counting monitor, etc): 6050g steel, 670g copper, 440g Aluminum, 650g plastics, 1040g Epoxy, 47g Tin, 27g Lead, 18g Nickel, 1.4g Silver, 0.35g gold, and 96 grams misc for a total of 9040g. A 17" CRT monitor: 6817g Glass, 2830g Steel, 700g Copper, 480g Ferrite, 240g Aluminum, 3530g Plastics, 140g Epoxy, 20g Tin, 593g Lead, 1.24g Silver, 0.31g Gold, and 98g of other materials. "Other" is probably largely the fiberglass in the PCBs and the silicon wafers. [19]

Capacitors

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