http://www.opencircuits.com/api.php?action=feedcontributions&user=76.226.65.242&feedformat=atomOpenCircuits - User contributions [en]2024-03-29T09:45:36ZUser contributionsMediaWiki 1.34.2http://www.opencircuits.com/index.php?title=Techniques&diff=20101Techniques2011-01-05T17:10:43Z<p>76.226.65.242: /* Homebrew fabrication */</p>
<hr />
<div>There are a wide variety of techniques used in electronics.<br />
<br />
<br />
== Printed circuit board design/fabrication ==<br />
=== Overview ===<br />
=== Software Design ===<br />
See [[#Software_design_tools|Software Design Tools]] below.<br />
<br />
==== Step by Step by using Software Design Tool ====<br />
*make sure the dimension and shape of PCB<br />
*make sure the size and location of Via for PCB stand<br />
*Make sure each components footprint.<br />
*each components are placed on suitable place by put on a hardcopy of simulation PCB<br />
*All components get enough clearance between them.<br />
*Silkscreen layout is confirmed.<br />
*PCB is drawn.<br />
*silkscreen adding the following:<br />
**version no.<br />
**organization name<br />
**board name<br />
*Netlist is ran and got a no error result.<br />
*DRC is ran and got a no error result.<br />
*Overall is checked.<br />
*generate Gerber and send to [[PCB Manufacturers]].<br />
<br />
=== Manual Design ===<br />
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.<br />
<br />
=== Homebrew fabrication ===<br />
Before exploring these techniques, you should understand your options with regard to services such as BatchPCB.com, ExpressPCB.com and PCB123.com. Being able to have several boards fabbed in 2 days for $59 (for example) makes it harder to justify the hassle of etching your own boards at home.<br />
* [http://www.electricstuff.co.uk/pcbs.html "How to make really really good homemade PCBs"] by Mike Harrison 2007<br />
* [http://www.esmonde-white.com/home/diversions/etching-a-copper-pcb "Etching PCBs using Toner Transfer"] and [http://www.esmonde-white.com/home/diversions/milling-a-copper-pcb "Milling PCBs"] by Francis Esmonde-White, includes information on how to go from Eagle PCB to the etching or milling step<br />
* [[Toner Transfer]] -- This method involves laser printing your PCB design onto paper, then transferring toner onto copper-clad board.<br />
* [[Photoetching]] -- Exposure of PCB designs onto photosensitized copper-clad board.<br />
* [[Chemical Etchants]]<br />
* [http://groups.yahoo.com/group/pcb-gcode "Mechanically etching or milling PCBs. No chemicals!"] -- Use your CNC router/mill to make PC boards.<br />
* [http://openfarmtech.org/index.php?title=Routed_Circuit_Board Open Source Ecology wiki: "Routed Circuit Board"]<br />
* [http://tech.groups.yahoo.com/group/Homebrew_PCBs/ Yahoo group: Homebrew_PCBs · Homebrew Printed Circuit Boards]<br />
* [http://reprap.org/wiki/Automated_Circuitry_Making RepRap wiki] has details on how to use open-source RepRap-based desktop routers to cut PCBs out of copper-clad board.<br />
* [http://www.pabr.org/pcbprt/pcbprt.en.html "pcbprt - Experiments in inkjet PCB printing"] by pascal. Some inkjet printers can print directly CD and DVD. Pascal explains step-by-step how to get those printers to print on copper-clad FR4 to make reasonably good etch resist. The main trick seems to be baking the freshly-printed boards to dry out the ink and get the dyes/pigments to stick to the copper -- otherwise the water-based ink immediately washes off as soon as you drop the board in the etch tank.<br />
* A few people have made "DIY Flex Circuits".[http://diydrones.com/profiles/blogs/diy-flex-circuits]<br />
<br />
=== Commercial PCB fabrication ===<br />
* [[Submitting PCB's for fabrication]] -- Common processes for submitting PCB's for fabrication.<br />
* [[PCB Manufacturers]]<br />
* [http://diydrones.com/profiles/blog/show?id=705844%3ABlogPost%3A30196 "PCB fabbing advice"] by Chris Anderson 2008<br />
<br />
==Best Practices for PCB Layout==<br />
===Theory===<br />
*Provide the easiest path (lowest impedance) for current to flow<br />
**Return current tends to flow directly under signal trace (for PCB having ground plane)<br />
**Inductance increases with length of traces<br />
**Inductance increases with the area enclosed by signal trace and ground<br />
*Prevent digital currents from contaminating analog currents<br />
*Decouple high speed components<br />
*Use ground loop avoidance tehniques<br />
<br />
===Design===<br />
*Partition PCB into "analog stuff" and "digital stuff".<br />
*No digital signal traces should cross over analog ground, and vice versa <br />
*For components having both analog and digital signals (e.g. ADC), orientate components so that the analog signal traces goes only over the analog ground plane, and digital signal traces goes only over the digital ground plane<br />
*AGND and DGND of ADC must have a small impedance (i.e. separated by short distance)<br />
*Add decoupling capacitors close to Vcc and DGND of ICs<br />
*Add ferrite beads and capacitors (PI-filter) to power rail for low-pass filtering (reduce ripples).<br />
<br />
===Routing===<br />
*Place fixed components first (components location that cannot be changed, e.g. connectors, buttons, etc)<br />
* Make installing parts onto the PCB fast:<br />
** Fastest: No through-hole parts. All surface-mount parts on the bottom side.<br />
** Next-fastest: All through-hole parts on the top side. All surface-mount parts on the bottom side. ( [http://www.psocdeveloper.com/articles/apple-mighty-mouse-spills-its-guts/the-capacitive-touch-sense-buttons-pcb.html "Mighty Mouse Main Printed Circuit Board (PCB)"] )<br />
*Separate components into groups<br />
**Digital signals only<br />
**Analog signals only<br />
**Digital and analog (Mixed) signals<br />
**High current devices (e.g. led backlight for LCD/buzzer)<br />
*Do not partition ground into analog and digital planes.<br />
**Use a single ground plane. See the "[[#References | Grounding References]]" below.<br />
*Orientate components that have mixed signals according to the orientation of the ground planes, and straddle components over DGND and AGND<br />
*Place digital only components over DGND<br />
*Place analog only components over AGND<br />
[[File:Pcb layout.png|thumb|800px|center|Grounding Example for PCB]]<br />
*Decoupling capacitors should be as close to the ICs as possible<br />
Vcc<br />
| | | | |<br />
+-----------+<br />
-------+-+--|-+---------|-------- Vcc<br />
|C| | IC |<br />
-------+-+--|---------+-|-------- GND<br />
+-----------+<br />
| | | | |<br />
GND<br />
*Lay critical (noise-sensitive) traces first (e.g. crystal, analog signals)<br />
**As short as possible<br />
**Use 45<sup>o</sup> turnings instead of 90<sup>o</sup><br />
*Paired signal traces (e.g. TX+, TX- in ethernet chips) should run parallel along each other<br />
TX+ -----\<br />
TX- ----\ \<br />
\ \<br />
\ \<br />
\ \<br />
\ \------------ TX+<br />
\------------- TX-<br />
<br />
===References===<br />
*Grounding<br />
**[http://www.hottconsultants.com/pdf_files/june2001pcd_mixedsignal.pdf Partitioning and Layout of a Mixed Signal PCB]: The importance of single ground plane and partitioning of analog and digital signal trace<br />
** [http://techref.massmind.org/techref/noises.htm#unsplit_ground Massmind Techref: "Unsplit ground"]<br />
**[http://www.hottconsultants.com/pdf_files/ground.pdf Ground- A Path For Current Flow]: The importance of decoupling capacitors<br />
**[http://www.ece.msstate.edu/courses/ece4512/des1_syllabus/current/PCB_Layout_Tips.ppt PCB Layout Tips]: a power point presentation<br />
**[http://pemclab.cn.nctu.edu.tw/w3news/%E6%8A%80%E8%A1%93%E5%A0%B1%E5%91%8A/TR-040.%E9%9B%BB%E8%B7%AF%E6%9D%BF%E4%BD%88%E5%B1%80%E5%8E%9F%E5%89%87/html/layout.htm PCB Layout Guidelines]: in Traditional Chinese<br />
*Crystals and Oscillators<br />
**[http://www.atmel.com/dyn/resources/prod_documents/doc8128.pdf AVR186]: Best Practices for the PCB layout of Oscillators<br />
*ADC & Analog Filters<br />
**[http://ww1.microchip.com/downloads/en/DeviceDoc/adn007.pdf ADN007]: Techniques that Reduce System Noise in ADC Circuits<br />
**[http://ww1.microchip.com/downloads/en/DeviceDoc/ADN010.pdf ADN010]: Predict the Repeatability of your ADC to the BIT<br />
**[http://ww1.microchip.com/downloads/en/AppNotes/00699b.pdf AD699]: Anti-Aliasing, Analog Filters for Data Acquisition Systems<br />
**[http://ww1.microchip.com/downloads/en/AppNotes/00682c.pdf AN682]: Using Single Supply Operational Amplifiers in Embedded Systems <br />
**[http://ww1.microchip.com/downloads/en/AppNotes/00990a.pdf AN990]: Analog Sensor Conditioning Circuits - An Overview<br />
*EMC<br />
**[http://www.atmel.com/dyn/resources/prod_documents/doc1619.pdf AVR040]: EMC Design Considerations<br />
**[http://www.freescale.com/files/microcontrollers/doc/app_note/AN1705.pdf AN1705]: Noise Reduction Techniques for Microcontroller-Based Systems<br />
** [http://www.st.com/stonline/books/pdf/docs/4988.pdf AN898: EMC general information]<br />
** [http://www.st.com/stonline/books/pdf/docs/4967.pdf AN901: EMC guidelines for microcontroller-based applications]<br />
** [http://www.st.com/stonline/books/pdf/docs/9914.pdf AN1709: EMC design guide for ST microcontrollers]<br />
<br />
== Circuit construction (Prototyping - Other than custom PCB) ==<br />
<br />
* [[Solderless protoboard]] ([http://en.wikipedia.org/wiki/Breadboard Wikipedia:Breadboard]) ([http://www.best-microcontroller-projects.com/prototyping.html a simple example with a small microcontroller])<br />
* [[Point-to-point]] ([http://en.wikipedia.org/wiki/Point-to-point_construction Wikipedia:Point-to-point construction])<br />
* [[Wirewrap]] ([http://en.wikipedia.org/wiki/Wire_wrap Wikipedia:Wire Wrap])<br />
* [[Dead bug style]]<br />
* [[Manhattan style]] aka [http://ciphersbyritter.com/RADELECT/BREADBD/BREADBD.HTM "A Modern Breadboarding Technology: Insulating Pads Soldered to a Ground Plane"]<br />
* [http://www.qrp.pops.net/ugly.asp "Ugly Construction"] (like deadbug... )<br />
[http://www.techlib.com/electronics/construction.html "Construction Ideas"] has nice photographs of the above circuit construction techniques.<br />
[[http://www.geofex.com/Article_Folders/protostyles/proto_styles.htm "Effects Building Techniques"] by R.G. Keen 1999 reviews, compares, and contrasts these techniques for circuit construction -- also a few more.<br />
<br />
* [[Stripboard]] (Veroboard): ([http://en.wikipedia.org/wiki/Stripboard Wikipedia:stripboard].)<br />
<br />
== Soldering techniques ==<br />
<br />
* [[Basic soldering]] -- How to use a soldering iron.<br />
* Surface Mount<br />
** [[Skillet reflow]]<br />
** [[Toaster oven reflow]]<br />
** [[Hot air soldering]]<br />
** [http://en.wikipedia.org/wiki/User:WillWare/Homebrew_surface-mount_construction A few different SMT assembly methods] that you can do at home on a cheap budget<br />
* [[Rework]] -- Techniques for fixing mistakes, or for adding new features to a board that ''almost'' does what you want.<br />
** [http://workmanship.nasa.gov/lib/insp/2%20books/links/sections/302_jumper%20wires.html official NASA recommendations for adding discrete wiring ("jumper wires") to PCBs]<br />
<br />
(Have you seen this [http://hackaday.com/2007/06/04/cnc-solder-pastepick-n-place/ CNC solder paste/pick n place] ?)<br />
''Hackaday has lots of other similar articles: [http://hackaday.com/?s=solder+paste search hackaday for "solder paste"]''<br />
<br />
== [[Hardware tool]]s ==<br />
A directory of [[hardware tool]]s that you may find useful.<br />
<br />
== [[software tool]]s ==<br />
== Software design tools ==<br />
<br />
A directory of [[software tool]]s that you may find useful.<br />
<br />
<br />
== [[PC-Microcontroller Communications]] ==<br />
<br />
Discussion of the various methods to connect a microcontroller or embedded system to a PC...<br />
<br />
== Embedded System Programming and Testing ==<br />
To add to the confusion programming in embedded system can mean a person writing a program or a device called a programmer "burning" a program into a chip. This section is for the "burning" meaning of programming.<br />
<br />
* Many systems use [[JTAG]] for programming and testing. (Such as [http://en.wikibooks.org/wiki/Atmel_AVR Atmel AVR embedded systems]]).<br />
* Other systems use some other kind of in-circuit programming.<br />
* Some people use [http://en.wikibooks.org/wiki/Embedded_Systems/Bootloaders_and_Bootsectors bootloaders] to make re-programming a little quicker.<br />
<br />
-- not sure that this next one is not misplaced ? --<br />
''We're talking about "programming and testing" ? What else do you use to test op-amp circuits?''<br />
<br />
* Many people use an [[oscilloscope]] ([[o'scope]]). See [[oscilloscope]] for a list of Keith has made a list of low-cost o'scopesl [http://www.techtravels.org/amiga/amigablog/?p=167 "PC USB logic analyzers that cost under $1000."] for a list of low-cost logic analyzers.<br />
<br />
Humans writing a program almost always do it in a language. Here is a section that discusses some of these languages: [[Programming Languages]]<br />
<br />
== driving motors ==<br />
<br />
See [[Stepper Motor Tester]] and [[motor driver]].<br />
<br />
== Enclosure ==<br />
<br />
* The Earth Signal should short to whole metal Case<br />
* Digital/Analog GND should separate to this Earth Signal, and should connect a Y-cap. to filter the noise between them.<br />
* Attention: do not place near between Earth Signal and Digital/Analog GND, otherwise some spark come out, and affect your whole system.<br />
* ''See [[enclosures]]''.<br />
<br />
== Misc Tips Tricks ==<br />
<br />
[[Misc Tips Tricks]]<br />
<br />
<br />
== Further Reading ==<br />
<br />
* [http://airborn.com.au/method/ "Electronics Design" from Airborn] gives an overview of the complete process: specification, (schematic) circuit design, layout, prototypes, firmware, pilot run, production.<br />
* EDA electronic design automation software is a subset of CAD in general. Is there a wiki that discusses CAD in general? Until I find it, I'm going to post these tools here: "Google SketchUp is a powerful yet easy-to-learn 3D software tool" http://sketchup.google.com/ ; "Inkscape is the best tool for SVG standard vector graphics" http://wiki.inkscape.org/ ; Visual Wiki http://visualwiki.org/<br />
* [http://www.national.com/rap/Story/0,1562,18,00.html "What's All This Ground Noise Stuff, Anyhow?"] by Robert A. Pease<br />
* [http://www.elecdesign.com/Articles/ArticleID/6150/6150.html "What's All This Teflon Stuff, Anyhow?"] by Robert A. Pease -- explains a situation using lots of metal (instead of carefully insulating everything with lots of Teflon) causes less noise. Also mentions "why am I telling you all of these details? If I design a tester with greatly improved performance to help me test a really high-performance product, why should I tell all our competitors so that anybody in the world can test their products using the improved tester? Why should I give away all of these hard-earned secrets?" and gives some very good reasons.<br />
* [http://groups.google.to/group/sci.electronics.design/browse_thread/thread/889153f0e77b1718/fcaac532bb6d4b12?fwc=1 sci.electronics.design: EDN: Measuring Nanoamperes] discusses some ways to measure extremely small currents.<br />
* [http://www.millpcbs.com/ MillPCBs.com for techniques on using a small cnc machine to mill PCB's]<br />
* [http://groups.yahoo.com/group/Homebrew_PCBs yahoo.com/group/Homebrew_PCBs]<br />
* [http://www.electricstuff.co.uk/pcbs.html electricstuff.co.uk/pcbs]<br />
* [http://www.fullnet.com/~tomg/gooteepc.htm fullnet.com/~tomg/gooteepc]<br />
* Dave McGuire says "The notion that through-hole soldering is easier than soldering surface-mount devices is, and always has been, [http://archives.seul.org/geda/user/Aug-2004/msg00175.html a myth.]" (Now, about keeping all the look-alike passive parts straight... :) )<br />
* [http://www.instructables.com/id/Intro-into-SMD-Soldering/ Intro into SMD Soldering]<br />
* [http://PMinMO.com/ PMinMO.com is THE PLACE for DIY CNC driver information]<br />
* [http://uptownmaker.blogspot.com/2009/07/18-essential-skills-for-maker.html 18 Essential Skills for a Maker]<br />
<br />
== Environmental Issues ==<br />
<br />
see [[better for the environment]].<br />
<br />
<br />
[[Category:Techniques]]</div>76.226.65.242http://www.opencircuits.com/index.php?title=Toner_Transfer&diff=20100Toner Transfer2011-01-05T17:06:58Z<p>76.226.65.242: /* External Links */</p>
<hr />
<div>Toner Transfer, like [[photoetching]], is a popular [[techniques | PCB fabrication technique]].<br />
<br />
== Introduction ==<br />
<br />
Press-and-Peel(tm), photoresist, Sharpie, nail polish...<br />
<br />
I have used this method for etching some fairly fine lines when fabricating a microstrip microwave filter using Tom Gootee's method linked to below. My two cents on this is the fact that the type of toner you use matters. In an admittedly small sample set of two different printers, the genuine HP microfine toner performed far better than the generic toner that was installed in a second printer that we tried. We used the Staple's glossy inkjet paper, and with the HP toner, it worked quite well.<br />
<br />
Also, the etching solution of 1 part muriatic acid to 2 parts hydrogen peroxide is worlds better than the ferric chloride solution as it is clear and doesn't stain everything it touches. It is also available locally (hydrogen peroxide is in every drug and grocery store, muriatic acid can be found at almost any hardware store).<br />
See [[Chemical Etchants]] for details.<br />
<br />
Thankfully, we worked in a school lab that had access to pure acetone for cleaning off the traces, so we didn't have to resort to foul-smelling nail polish. <br />
<br />
== Toner Transfer Tip and Tricks From around the World ==<br />
<br />
Leave your tips and tricks here, it is ok if you found it on the web (give reference if you have them) or if you picked it up somewhere else even figured it out yourself. If you have a long write up do not leave it here, make a new page and link to it.<br />
<br />
<br />
=== Paper ===<br />
<br />
Experiment with paper, keep shifting around to find the right stuff. I use magazine paper. You want a glaze (usually clay) so the toner will transfer, and soluble paper so you can easily remove it. Right now, my favorite is the RISDI catalog. If the paper is too thin it may jam in the printer (check printer settings by the way). Some have suggested attaching (perhaps just by folding the leading edge over) it to standard paper as a carrier to get it through the printer. There are, of course, photo papers for laser printers and stuff made just for toner transfer.<br />
<br />
=== Roller === <br />
<br />
A roller may help focus pressure, especially at the edges. This has to be done while hot. One way I have seen is to put a dowel (perhaps several) under the board and roll back and forth on that.<br />
<br />
=== Padding === <br />
<br />
A couple of layers of paper towel as padding between the board and the iron can help even out the pressure and improve adhesion at the edges.<br />
<br />
=== Electric Grill as Ironing Board === <br />
<br />
I [[russ_hensel]] was having trouble getting enough heat. My breakthrough was to use a temperature controlled electric grill (great for pan cakes by the way) set for 350°f and iron as usual.<br />
<br />
=== Remember high temperature is required === <br />
<br />
This is not like ironing a shirt, the thing has to get hot, move the iron slowly or almost not at all. Pressure is good, experiment to find out how much.<br />
<br />
=== Edges === <br />
<br />
The edges are usually the problem focus your attention there, if you get the edges you will probably do fine on the center with only minimal attention there.<br />
<br />
== Touchup ==<br />
<br />
Touchup with a Sharpie marker.<br />
Some people (such as Stefan Vorkoetter) draw their entire board with the Sharpie marker, completely bypassing all that hassle with computers, laser printers, special paper, ironing, etc.<br />
<br />
Scrape off any toner or Sharpie ink that is covering metal you don't want.<br />
<br />
Now you're ready to drop it in the [[Chemical Etchants]].<br />
<br />
== External Links ==<br />
<br />
* [http://www.stefanv.com/electronics/etching.htm "Making Excellent Printed Circuit Boards"] by Stefan Vorkoetter<br />
<br />
* [http://www.esmonde-white.com/home/diversions/etching-a-copper-pcb "Etching a Copper PCB using Toner Transfer and Peroxide/HCl"] by Francis Esmonde-White<br />
<br />
* [http://www.pulsarprofx.com/PCB/a_Pages/1_Menu/overview.html Direct Etch PCBs] These guys are selling a product for toner transfer, might be good or bad, ( how about a review by a user? ) but in any case they also have a bunch of very useful tips.<br />
<br />
* [http://www.ceunes.ufes.br/downloads/2/sandramuller-pci_metodo_termico.pdf Tonner transfer - By Lucas Zampar Bernardi - Article in Brasilian Portuguese]<br />
<br />
* [http://www.veys.com/2001/11/21/making-home-made-pcbs Toner transfer]<br />
<br />
* [http://www.fullnet.com/u/tomg/gooteepc.htm Toner transfer - by Tom Gootee]<br />
<br />
* [http://www.karosium.com/2007/03/clean-simple-cheap-toner-transfer.html Clean, Simple, Cheap Toner Transfer - By Karo-sama]<br />
<br />
* [http://diycircuits.net/makepcb/pcb_making PCB Making Photo Etching Toner Transfer including Using Matte Paper - by Hilary Cheng]<br />
<br />
* [http://www.riccibitti.com/pcb/pcb.htm How to make PCBs at home in 1 hour & W I T H O U T special materials]<br />
<br />
* [http://myweb.cableone.net/wheedal/pcb.htm Decent PCB's on the cheap.]<br />
<br />
* [http://www.instructables.com/id/5pcb/ 5pcb]<br />
* [http://www.instructables.com/id/Two-sided-PCB-using-toner-method/ Two sided PCB using toner method]<br />
* [http://www.instructables.com/id/DIY_Printed_circuit_board/ DIY Printed circuit board ] A video, pretty good.<br />
* [http://www.5bears.com/pcb.htm Printed Circuit Boards for the Masses] A pretty quick tutorial.<br />
* [http://revision3.com/systm/etching/ Episode 15 PCB Etching] A video, the safety warnings are a bit over the top.<br />
* [http://more.random.stuff.googlepages.com/howtomakepcbs How to make PCBs with a laser printer] <br />
* [http://www.mouldy.org/making-a-pcb "Making a PCB"] toner transfer method; 0.1mm tracks; all surface mount with a tiny fine-pitch QFN IC. [http://www.mouldy.org/assembly later] he uses the Sparkfun tutorial for [[skillet reflow]].<br />
* [http://www.instructables.com/id/Quickie-PCB-Production-with-Bonus-NiCd-Battery-Ch/ "Quickie PCB Production (with Bonus NiCd Battery Charger)"] is entirely drawn with Sharpie markers (no computer, no laser printer).<br />
* [http://www.dr-lex.be/hardware/tonertransfer.html Dr. Lex: Creating PCBs with the toner transfer method]<br />
<br />
[[Category:Techniques]]</div>76.226.65.242http://www.opencircuits.com/index.php?title=Chemical_Etchants&diff=20099Chemical Etchants2011-01-05T17:04:50Z<p>76.226.65.242: /* External Links */</p>
<hr />
<div>{{stub}}<br />
<br />
Chemical etching is one step of some popular [[techniques | PCB fabrication techniques]].<br />
<br />
In this technique,<br />
* one starts with a copper-clad board.<br />
* one puts a mask over all the copper he want to keep. There are a variety of ways to do this -- see [[Toner Transfer]] and [[Photoetching]].<br />
* one removes the parts he don't want to keep, by chemically etching away the copper.<br />
* cleanup: wash off the board in the sink; carefully store or dispose of the acid.<br />
<br />
There are a lot of different chemical techniques for doing this, each with its own advantages and drawbacks.<br />
<br />
None of these chemicals is incredibly dangerous, but they can all be toxic or caustic, and should be treated with care. Eye protection and gloves are a very good idea. Before you start, make sure you know how dangerous each chemical is, and figure out what you will need to do if you spill it or get it on yourself. Washing with plenty of water is usually a good start. For some chemicals you may want to keep a neutralizing agent handy. An MSDS (Materials Safety Data Sheet) for the chemical will give you some basic information.<br />
<br />
== vinegar and salt ==<br />
<br />
* [http://www.kobakant.at/DIY/?p=2575 How to get what you want: Salt and Vinegar Etching]<br />
* [http://www.flickr.com/photos/jeanbaptisteparis/4831465916/ smt pcb with Salt and Vinegar]<br />
* [http://www.instructables.com/id/The-Saltwater-etch-process/ The Saltwater etch process]<br />
* [http://www.electro-tech-online.com/general-electronics-chat/33876-electro-etching-no-acid.html electro etching a PCB with vinegar, salt, and a 12 V power supply] (the copper etched off the PCB is plated on the anode?) -- however, other people claim that "You should not be using any acids (or basic 'acids') with your [electro] etcher at all. No FeCl no vinegar, etc ".[http://www.bladeforums.com/forums/showthread.php?t=671936]<br />
<br />
== Ferric Chloride ==<br />
This is the most common hobbyist etchant. Ferric chloride, FeCl<sub>3</sub>, is a brownish substance. It's usually sold in a bottle (dissolved in water, perhaps with a little acid or peroxide) or as a powder (which you have to dissolve in water).<br />
<br />
When in solution, ferric chloride is a ferric ion (Fe<sup>3+</sup>) and a chloride ion (Cl<sup>-</sup>). The ferric ion reacts with the metallic copper on the circuit board in a redox reaction, producing a ferrous ion (Fe<sup>2+</sup>) and cuprous or cupric (Cu<sup>1+</sup> or Cu<sup>2+</sup>) copper. The chlorine is just along for the ride. The copper ion, unlike the metallic copper, is soluble, so it leaves the circuit board and goes into solution. The reaction products form a black sludge which settles to the bottom of the etching tank. After etching enough copper, all your Fe<sup>3+</sup> is used up and your solution is full of Cu<sup>1+</sup>, and you need to get more etchant.<br />
<br />
== Ammonium Persulfate ==<br />
Expensive & hard to control and optimize the process parameters (such as specific gravity & pH value).<br />
<br />
== HydroChloric Acid / Hydrogen Peroxide ==<br />
<br />
Mixing about 1 part HCl (Which can be found at most hardware stores, also known as Muriatic Acid. Ask for concrete cleaner.) into 2 parts Hydrogen peroxide (normally used for cleaning cuts) you can make a fairly powerful etchant. Use gloves and don't breathe the fumes though. This will etch a 3"x5" board in less than 10 minutes. No need to heat it up. I usually like to drill a small hole through the board on a corner and thread a wire or nylon string through to help agitate / remove the board.<br />
<br />
When the board is done etching, the etchant will probably look like green kool-aid, from the copper content in it. This stuff is highly corrosive and will burn skin, which is why you should wear gloves. But it is easy to handle, and fairly easy to dispose of. the etchant is easily deactivated with baking soda. Pour enough baking soda into it slowly (to keep it from boiling and overflowing... remember what happens with baking soda/vinegar? ya...) until it is a solid mass, then leave it in the sun to dry. You should contact your local authorities to find out what you should do with it next. Whatever you do, DO NOT dump the stuff down the drain, it will eat through your pipes just like any of the other etchants.<br />
<br />
Alternatively, instead of disposing of the etchant, you can re-use it again and again. In fact, after etching a few boards with this solution, you will have successfully made [[Chemical Etchants#Acid Cupric Chloride|Acid Cupric Chloride]] (see below).<br />
<br />
== Sodium Persulfate ==<br />
More environmentally friendly than ferric chloride. Can monitor the etching as initially clear new etchant solution turns blue from the copper ions.<br />
<br />
== Acid Cupric Chloride ==<br />
Dead simple etchant made from ordinary, store-bought chemicals (hydrochloric acid and hydrogen peroxide). Has the advantage that it can be regenerated by bubbling oxygen/air through it, or by adding more H<sub>2</sub>O<sub>2</sub>. In addition, it doesn't get used up: the etchant bath simply grows with use (kind of like sourdough starter…)<br />
The used etchant also makes a great algecide/pH reducer for your pool (and a whole lot cheaper than that stuff they sell at the pool store).<br />
<br />
What you need:<br />
* 38% Hydrochloric Acid, HCl (available at finer hardware stores or pool supply stores as Muriatic Acid)<br />
* 3% Hydrogen Peroxide, H<sub>2</sub>O<sub>2</sub> (available from any drug store)<br />
* Plastic or Glass Pans, Jars, and tongs (no metal)<br />
Directions:<br />
<br />
# Mix your HCl and H<sub>2</sub>O<sub>2</sub> 1:1 in a non-metalic container, making sure to add the acid slowly to the H<sub>2</sub>O<sub>2</sub>. DO NOT ADD THE H<sub>2</sub>O<sub>2</sub> TO THE ACID!!! <br />
# After you've masked your board, dip it in the solution and constantly agitate. You should notice a dark green cloud start to come from the board almost immedately which quickly dissapears or turns lighter as it gets further from the surface of the board.<br />
# Etching should take about 10min depending on the temperature and how well you agitated the etchant. When all of the copper is gone, dip in water to wash off any stray etchant and stop the reaction.<br />
# When done etching, save used etchant in a non-metalic container and mark clearly its contents.<br />
# If your etchant has become a dark, murky green color, add a little bit of H<sub>2</sub>O<sub>2</sub> or bubble air/O<sub>2</sub> through the solution to regenerate it back to a light, transparent green color.<br />
See links at bottom for more information on the chemistry and some pictures of the process.<br />
<br />
== Disposal procedures ==<br />
Flushing used etchant down the drain is a bad idea (and usually illegal) because copper ion is toxic. The usual recommended way to dispose of hobbyist amounts of etchant is to convert it to a solid somehow and dispose of the solid in accordance with local laws.<br />
<br />
== External Links == <br />
<br />
* [http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/ "Sponge + Ferric Chloride Method -- Etch PCBs in One Minute!"]<br />
* [http://www.k9spud.com/wiki/PCB:Etchants Ferric Chloride vs. Ammonium Persulfate] and other etching chemicals.<br />
* [http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html Etching with Air Regenerated Acid Cupric Chloride] — an excellent in-depth page on acid cupric chloride etching by Adam Seychell.<br />
* [http://www.esmonde-white.com/home/diversions/etching-a-copper-pcb Etching a Copper PCB with HCl and H2O2]<br />
*[http://www.mgchemicals.com/index.html MG Chemicals]A possible source?<br />
* [http://reprap.org/wiki/MakePCBInstructions RepRap wiki: Make PCB instructions]<br />
<br />
== Internal Links ==<br />
<br />
<br />
*[[Toner Transfer]]<br />
*[[Techniques]]<br />
*[[Eagle Links]]<br />
<br />
<br />
[[Category:Techniques]]</div>76.226.65.242