no edit summary
No edit summary |
No edit summary |
||
Line 1:
'''PCB''' is an abbreviation for '''printed circuit board''', the copper clad boards used for mounting and connecting electronic circuit components. Originally PCBs had holes for component leads, pins, wires, etc. which passed through and were soldered to the copper tracks on the underside. From the 1980s [[surface mount]] components have been used increasingly instead of through-hole components. Double-sided or multi-layer boards use plated-through holes, called vias to connect the traces on different layers. The most common PCBs are composed of either FR4 (glass fiber and epoxy), or the cheaper and easier to cut and drill but more brittle SRBP (Synthetic Resin Bonded Paper).<ref name="wpcb">[[Wikipedia:Printed circuit board]]</ref>
This article aims to be a guide to quickly and efficiently producing consistently high quality homebrew PCBs. The cost of materials is of secondary importance.<ref name="mh">''[http://www.electricstuff.co.uk/pcbs.html How to make really really good homemade PCBs]'' by Mike Harrison</ref>
==PCB layout design==
Choose a suitable [[Electronic design automation|EDA]] application, for the schematic capture (the circuit diagram), PCB layout, Gerber files etc. such as [[Eagle]], [[DesignSpark PCB]], [[KiCad]], [[gEDA]], [[Fritzing]], etc.<!-- Wikibooks' Practical Electronics [http://en.wikibooks.org/wiki/Practical_Electronics/PCB_Layout PCB Layout] and [http://en.wikibooks.org/wiki/Practical_Electronics/PCB_Layout/Trace_Current_Capacity Trace Current Capacity].
===Best Practices===
==Bill of materials==
-->
==Homebrew PCB fabrication==
Making PCBs at home is much quicker, with results the same day instead of waiting weeks for a commercial fabricator, and cheaper. However it involves working with messy chemicals, drilling will be tedious and the overall quality wont be as good.
Line 16 ⟶ 17:
Alternately take a straight edge and secure it along the line to cut. Then take a chisel (one set aside for this), and run one of the corners along the straight edge. First pass go lightly to just get a bit of a groove dug in for the tool to follow so it wont jump out on subsequent passes. Next pass or two press hard, and dig in for a deep groove. Score on both sides. Secure the board and snap the piece off. To finish the edge make a pass or two along it with a fine file.<ref>[http://www.eevblog.com/forum/manufacture/cutting-fr4-boards/15/ Cutting FR4 boards], EEVblog forum, August 2012</ref><ref name="diyaudio"/>
==Printing and etching==
There are two methods to choose from, the toner transfer method is cheap and is simpler but takes a lot of patience and fiddling about. The more expensive photo resist method can be much more accurate and one printout can be used multiple times but it requires a UV box and another chemical to develop the board.<ref>[http://www.diystompboxes.com/smfforum/index.php?topic=102924.msg914631#msg914631 Re: DIY etching PCB's - Toner Method or Photo Resist Method?] by R O Tiree, 27 May 2013</ref>
==Etching and printing==▼
===Photo resist===
Print the PCB layout onto clear or translucent film - this is the ''mask''. Plastic transparency might deform from the heat of the printing. Place the printed side against photo-resist coated PCB and expose to ultra-violet light. Pre-sensitised PCBs are easier than spray photo-resist where it's difficult to attain consistent thickness needed to estimate a correct exposure time. For double sided boards, first tape the two masks printed sides together then tape the board in place between them and expose both sides to the UV.<ref name="mega">Mega [http://www.megauk.com/video.php PCB Instructional Video]</ref> Use the recommended developer not sodium hydroxide, this removes the coating where it has been exposed to UV. Follow the manufacturers directions for correct concentration and temperature. Leaving the photo-resist on the board prevents the copper oxidising and it acts as half reasonable a solder flux.<ref name="mega"/>
Etching the PCB in Ferric Chloride (FeCl<sub>3</sub>) solution removes the copper not masked by the etch resist. Take precautions because FeCl<sub>3</sub> will deeply stain anything it comes in contact with.
▲===Toner transfer method===
===Safe disposal of FeCl<sub>3</sub>===
▲This is using a laser printer or copier (not inkjet) to print an image of the PCB tracks on glossy inkjet paper. Laying this printed side onto the de-oxidised and de-greased copper laminate and using an iron at a high temperature, on the rear of the paper to transfer the toner from the paper onto the copper. After soaking in water to remove the paper, the toner now transferred to the copper laminate acts as an etch resist.<ref>[http://fullnet.com/~tomg/gooteepc.htm ''Easy Printed Circuit Board Fabrication, Using Laser Printer Toner Transfer''] by Thomas P. Gootee, 2007</ref>
FeCl<sub>3</sub> is toxic and harmful to the environment - do not flush spent etchant down the drain. After use leave the FeCl<sub>3</sub> to stand still for at least a couple of days, the copper precipitates to the bottom, leaving still useful etchant on top. Pour this into another container. Add pure sodium bicarbonate (NaHCO<sub>3</sub>) aka baking soda to the thick mud at the bottom. The NaHCO<sub>3</sub> will react with ferric chloride rendering the solution relatively harmless to the environment. Do only a little bit at a time, waiting for the reaction to settle down each time. The reaction will produce a substance 7 to 10 times the volume of the solution, any spillage will contain still active FeCl<sub>3</sub> that will stain whatever it comes in contact with. Keep adding the NaHCO<sub>3</sub> until the rust-coloured mess is fairly dry in texture. It can then be disposed of along with the household waste.<ref>[http://www.diystompboxes.com/smfforum/index.php?PHPSESSID=2721ef0370b6f7ad578168a1c3200a26&topic=50426.msg377103#msg377103 Re: how do you all dispose of Ferric Chloride?] by Mark Hammer, 15 October 2006</ref>
==Tinning==
If you don't tin the board, coat the copper laminate with rework flux to prevent it oxidising.<ref name="mh"
Tin-plating a PCB makes it a lot easier to solder. Use room-temperature tin plating crystals e.g. ''Seno Immerse Tin Crystals'', these produce a good finish in a few minutes but can be expensive. Only make enough tinning solution to cover a PCB in the tinning tray. Keep the solution in a concertina-type bottle to exclude air. Also avoid contamination with metals other than copper. Thoroughly rinse and dry the PCB before tinning. Use a separate tray and pair of tongs specifically for tinning, and rinse them after use. If the solution stops tinning, discard it, clean & rinse the tray, and make up a fresh solution. A cool tinning solution will usually prevent tinning so ensure the temperature of the tinning solution is at least 25ºC, but not more than 40ºC, put the bottle in hot water to warm it up.<ref name="mh"/>
Line 34 ⟶ 38:
<!-- Hole dimensions-->
{{stub}}
==Commercial PCB fabricators==
== References ==
Line 39 ⟶ 45:
== External links ==
*Wikipedia:[https://en.wikipedia.org/wiki/Comparison_of_EDA_software Comparison of EDA software]
*[http://www.opencircuits.com/Printed_Circuit_Boards Printed_Circuit_Boards] at Open Circuits
*[http://www.megauk.com/ Mega Electronics] UK manufacturer and supplier of products for printed circuit board production, etc.
*[https://wiki.london.hackspace.org.uk/view/Project:Deactivating_a_ferric_chloride_solution Deactivating a ferric chloride solution]
===Commercial fabrication===
*[http://www.ladyada.net/library/pcb/manufacturers.html Where To Have Made]
*[http://pcbshopper.com/ PCB Price Comparison], a calculator showing the prices for prototype PCBs from different manufacturers
==Further reading==
*''The Circuit Designer's Companion'' by Peter Wilson, Newnes, 2012, ISBN 0080971385
*''How to Design and Make Your Own PCBs'' by R. Penfold, Babani, 1983, ISBN 0859340961
[[Category:Electronics]]
| |||