Project:PCB Making: Difference between revisions

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Project maintained by Daniel Sikar ~/ dsikaratgmaildotcom.
Project no longer maintained, was maintained by by Daniel Sikar ~/ dsikaratgmaildotcom.
 
'''To see the canonical guide on how to etch PCBs at the LHS go to this page: [[Pcb etching instructions]]  '''
 
Note : see '''[[PCB]]''' for other references


{{ProjectDetails|ProjectTitle=PCB_Making}}
{{ProjectDetails|ProjectTitle=PCB_Making}}
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How to make a Printed Circuit Board (PCB) using photoresist laminates.
How to make a Printed Circuit Board (PCB) using photoresist laminates.
==== Overview ====
This howto is intended as a module, aimed at providing building blocks to emulate and extend projects such as the [http://dorkbotpdx.org/wiki/benito Benito 7], [http://www.makestuff.eu/wordpress/?page_id=569 Nanduino] and [http://www.pjrc.com/teensy/ Teensy].


==== Equipment ====
==== Equipment ====


There is an ongoing pledge campaign to improve facilities with a [[PCBEtchTank|better etch tank]]
The etch station needs thoughtful operation and occasional maintenance. See [[Equipment/PCB etch station]] for details.


== Motivation ==
== Motivation ==
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There are several steps in producing electronic devices. PCB making comes in after the artwork is ready to be transferred and before the components are ready to be soldered onto the board.
There are several steps in producing electronic devices. PCB making comes in after the artwork is ready to be transferred and before the components are ready to be soldered onto the board.


== Method ==
The method described consists of exposing, developing, etching, drilling and tinning a photoresist copper-clad board.
== Other Methods and Guides ==


There are also [http://www.opencircuits.com/Chemical_Etchants alternatives] to some of the chemical processes - e.g.
There are also [http://www.opencircuits.com/Chemical_Etchants alternatives] to some of the chemical processes - e.g.


[[Cupric_chloride_etchant|Air-regenerated etchant]]
*[[Cupric_chloride_etchant|Air-regenerated etchant]]
 
*[http://www.nontoxicprint.com/etchcopperandbrass.htm Edinburgh etch]
Another guide can be found here : [http://www.electricstuff.co.uk/pcbs.html Mike's electric stuff]


== Method ==
Some other pages on this wiki with other process details are [[Pcb_etching_instructions]] and [[Project:DIY_PCB_Making]]


The method described consists of exposing, developing, etching, drilling and tinning a photoresist copper-clad board.
Other guides can be found here : [http://www.electricstuff.co.uk/pcbs.html Mike's electric stuff] and here [http://quinndunki.com/blondihacks/?p=835 Blondihacks]


== Bill of Materials (BOM) ==
== Bill of Materials (BOM) ==


# Photoresist Copper-clad board [http://www.maplin.co.uk/Module.aspx?ModuleNo=2033 Maplin product page (code FA61R)].
# Photoresist Copper-clad board [http://www.maplin.co.uk/Module.aspx?ModuleNo=2033 Maplin product page (code FA61R)].
# Sodium silicate [http://www.maplin.co.uk/Module.aspx?ModuleNo=2085 Maplin product page (code AP01B)]. - full bottle purchased 05-Aug-2010
:NOTE if you have to use maplin PCB, you MUST use maplin developer or Sodium Hydroxide. It does NOT work with the developer in the hackspace PCB station.  
# Universal PCB Developer (Sodium Metasilicate Pentahydrate) [http://www.maplin.co.uk/Module.aspx?ModuleNo=2085 Maplin product page (code AP01B)]. - full bottle purchased 05-Aug-2010
# Ferric chloride [http://www.maplin.co.uk/Module.aspx?ModuleNo=2097 Maplin product page (code XX12N)].
# Ferric chloride [http://www.maplin.co.uk/Module.aspx?ModuleNo=2097 Maplin product page (code XX12N)].
# Methylated spirits [http://www.wickes.co.uk/Methylated-Spirits/invt/600343 Wickes product page (code 600343)].
# Methylated spirits [http://www.wickes.co.uk/Methylated-Spirits/invt/600343 Wickes product page (code 600343)].
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Note in this cross section, black in the transparency layer represents a via (trail) on the left and a pad (where a component pin  will be soldered) on the right.
Note in this cross section, black in the transparency layer represents a via (trail) on the left and a pad (where a component pin  will be soldered) on the right.
<br><br>
<br><br>
1. The artwork (printed onto a transparency) is placed over the photoresist copper-clad board and exposed to UV light. (8 minutes)
1. The artwork (printed onto acetate or paper) is placed over the photoresist copper-clad board and exposed to UV light. (8 minutes)
<br>
<br>
[[File:UV_Exposure.jpg|400px]]
[[File:UV_Exposure.jpg|400px]]
<br>
<br>
2. The photo sensitive coating weakens as a result of exposure, and is rinsed off with a 10% sodium silicate solution. (1-2 minutes)
2. The photo sensitive coating weakens as a result of exposure, and is rinsed off with a 10% sodium of "Universal PCB Developer". (1-2 minutes)
<br>
<br>
[[File:RemovalExposedPhotoSensitiveArea.jpg|400px]]
[[File:RemovalExposedPhotoSensitiveArea.jpg|400px]]
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[[File:EtchingExposedCopperLayer.jpg|400px]]
[[File:EtchingExposedCopperLayer.jpg|400px]]
<br>
<br>
4. Remaining photo sensitive layer is removed with Methylated spirits. This can also be achieved by scrubbing the etched board with wire wool.
4. Remaining photo sensitive layer is removed - with Methylated spirits, scrubbing or re-exposing and rinsing in sodium silicate solution.
<br>
<br>
[[File:RemovalUnexposedPhotoSensitiveLayer.jpg|362px]]
[[File:RemovalUnexposedPhotoSensitiveLayer.jpg|362px]]
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The chemicals can be returned to their respective bottles, and the small residue in the tubs used in the process should be rinsed out in the sink.
The chemicals can be returned to their respective bottles, and the small residue in the tubs used in the process should be rinsed out in the sink.


Once spent, the sodium silicate solution can be poured down the drain. The ferric chloride on the other hand, must be taken to a Harzadous Disposal Unit, or, deactivated according to this [[Projects/Deactivating a ferric chloride solution|method]].
Once spent, the Universal PCB Developer solution can be poured down the drain. The ferric chloride on the other hand, must be taken to a Harzadous Disposal Unit, or, deactivated according to this [[Projects/Deactivating a ferric chloride solution|method]].


== Real life example ==
== Real life example ==
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[[File:cutting_to_size.jpg|400px]]
[[File:cutting_to_size.jpg|400px]]


* Finishing the edges, to ensure good contact between transparency and board. Very important step, if any of the edges are raised the UV light can get under the transparency and you'll lose definition on thin traces.
* Alternatively, the LHS now has a metal sheet cutter which makes for cleaner and less laborious cuts.
 
[[File:Chopping.jpg|400px]]
 
* Finishing the edges, to ensure good contact between transparency and board. If any of the edges are raised, UV light can get under the transparency and definition is lost on thin traces.


[[File:finishing_edges.jpg|400px]]
[[File:finishing_edges.jpg|400px]]


* Preparing for exposure. Double-up transparency for better results, or run through the printer two or three times to put down more toner.
* Preparing for exposure. Double-up transparency for better results, or run through the printer two or three times to put down more toner.  


[[File:Developing_photoresist.jpg|400px]]
[[File:Developing_photoresist.jpg|400px]]
* Alternatively, good results can be obtained by printing PCB artwork on paper.
[[File:PaperPrint.jpg|400px]]


* Peeling off protective layer.
* Peeling off protective layer.
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* Expose in the UV box.
* Expose in the UV box.


* Developing the photoresist in a sodium silicate solution.
* Developing the photoresist in a Universal PBC Developer solution.


[[File:TQFP32_DIL32_PhotoresistDevelopment.jpg|400px]]
[[File:TQFP32_DIL32_PhotoresistDevelopment.jpg|400px]]
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TODO
TODO
== Double sided boards ==
The process for exposing and etching double sided boards is basically the same as described previously, with the addition of one extra layer.
The one thing to watch out for when generating the artwork, is that one of the layers needs to be mirrored, to match the opposite layer, when both come face to face.
In Eagle CAD, the top layer is mirrored.
Once printed, the layers are, in the case shown, stapled together.
The optimal distance between staples allows for the board to be inserted into the "pocket" but not move freely.
This helps to keep the board registered, when flipping it around in the UV light box.
One of the remaining open sides can also be stapled, leaving one aperture for board insertion into the pocket.
[[File:PCB_Artwork_pocket.jpg|400px]]


== Notes ==
== Notes ==


Artwork can be printed straight onto a transparency sheet, on a laser printer. Alternatively high street print shops will do the job.  One run on the laser might not be dark enough, try printing multiple times on the same sheet to lay down more toner.
=== Universal PCB Developer ===
 
According to the [http://www.chilternconnections.co.uk/ZENCART/HANDSSHEETS/Etching%20Products/PDSM_MSDS.pdf safety datasheet] of the PCB photoresist developer (Universal PCB Developer, manufactured by Chiltern Connections Ltd and sold by Maplin), the compound is Sodium Metasilicate Pentahydrate, containing the hazardous ingredient Disodium Metasilicate at a concentration of 58%.
 
=== Artwork ===
 
Artwork can be printed straight onto a transparency sheet, on a laser printer. Alternatively high street print shops will do the job.  One run on the laser might not be dark enough, try printing multiple times on the same sheet to lay down more toner, though the register might be lost.


The best medium for printing artwork on a laser is tracing paper as it has much better toner adhsion than transparency film and works fine with just one pass - it needs to be fairly thick, at least 90GSM to avoid crinkling in the fuser. A few years ago I wrote this extensive guide to making good PCBs : www.electricstuff.co.uk/pcbs.html
The best medium for printing artwork on a laser is tracing paper as it has much better toner adhesion than transparency film and works fine with just one pass - it needs to be fairly thick, at least 90GSM to avoid crinkling in the fuser. A few years ago I wrote this extensive guide to making good PCBs : www.electricstuff.co.uk/pcbs.html


The board was drilled on the Dremel Workstation.
=== Drilling ===
Drill bit; 0.7mm (smallest one) on the workstation plastic drill case, chuck is in the silver dremel case. [I couldn't find a suitable drill bit or chuck, or silver dremel case for that matter...]
 
0.8mm drill bits work well (tungsten carbide better than HSS), anything thicker and the remaining copper might be damaged or in case of double sided boards, lifted on the other side, as the drill goes through the board.
 
=== UV exposure ===


The UV box, etching tubs and all chemicals are currently in the left hand metal cupboard (marked etching stuff) at the far end of the dirty room.
The UV box, etching tubs and all chemicals are currently in the left hand metal cupboard (marked etching stuff) at the far end of the dirty room.


If anyone in interested in making PCBs and needs a hand, there are now 3 members of the Hackspace etching PCBs in loco - Daniel (dsikar), Solexious and Meurig, all willing to help, I am sure.
Put the light on a 2 minute time lapse prior to exposing the board, to warm it up.
 
=== Removing remaining photoresist layer ===
 
Once the unwanted copper has been etched, there is still photoresist left on the remaining copper. It is practical to expose the board again, thus weakening the photoresist, then repeating the sodium silicate rinse. Note that removing the resist on most types of photosensitive board is not necissary unless you are going to tin plate the PCB. The resist protects the copper from oxidising and also acts as a flux when soldering so it can be benificial not to strip it.


== Tried and Tested Settings ==
== Tried and Tested Settings ==
===JasperWallace 11-12-2010 ===
* plain paper, mirrored with the toner side next to the board.
* I used an upside down hackspace storage box with a light under it as a light box for alignment (it was a double sided board).
* I used the shear press brake for cutting the boards, it does mangle the edges a little, so be careful when peeling off the protective film that it dosn't take off some of the photo resist with it.
* for long thin boards it's hard to get them square in the brake press.
* 5 mins in the uv box (for each side).
* didn't time the developing of the photoresist in the sodium silicate, just agitated it by hand until it was obviously done.
* one board done with the 'recycled' clear etchant, took 40 mins on the agitator .
* 2nd board done with a mix of ferric chlorides, the fresh stuff is quickest, next time i'll get it properly warmed 1st.
* A drop of meths on some paper towel is fine for removing the photo resist.
* Drilled in the milling machine, move along only one axis when drilling a row of holes for DIP devices make all the holes stay in line.
* drilling is really tedious, [[Pledges/CNC_Mill]].
* My board was slightly off square so not all the hole in one axis were truly on the same axis.


===pingbat & samthetechie 14-Oct-2010===
===pingbat & samthetechie 14-Oct-2010===
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* Addendum: My first board was ruined by leaving a lip where I'd cut it (hacksaw). Always make sure the board is perfectly flat! I left some developer and etchant in the trays since I'm sure they'd by good for a few more runs and I wasn't sure how to dispose of them.
* Addendum: My first board was ruined by leaving a lip where I'd cut it (hacksaw). Always make sure the board is perfectly flat! I left some developer and etchant in the trays since I'm sure they'd by good for a few more runs and I wasn't sure how to dispose of them.
[[Category:PCB making]]
[[Category:Guides]]