DIY Double Sided PCB's?

rwgast_logicdesignrwgast_logicdesign Posts: 1,464
edited 2012-06-26 - 13:14:10 in Propeller 1
Ok so I have all the chemicals and copper clad I need to start etching PCB's. Unfourtantely I just dont have the money to get my pcb's printed somewhere. Iv read up on the transfer method and feel pretty confident I can etch my boards, I also have access to a decent drill press so I should be able to churn them out fairly quickly. Im planning to use KiCad, I have access to altium and dip trace, but I want to keep my kit fully open source and I feel like using a pay product or a pcb design product that only works on windows is a bad choice. I started with express pcb it seems alot easier, if anyone has some good links to kicad tutorials Id appreciate it, Ive seen a few but there isnt alot of good stuff out there that I can find. Ive also read Dave Jone E-book on PCB Design and gained some good insight that way. But Im still unclear on a few things when moving from a perfboard to designing a pcb and hand making boards.

First of all I accidently ordered some surface mount EEPROMs (http://search.digikey.com/us/en/products/24FC64FT-I%2FOT/24FC64FT-I%2FOTCT-ND/2651408) I meant to get the dip version. So I figured a good simple start may be to just make a simple breakout board for one of these EEPROMs that will slide into an 8 pin dip socket. This will give me such an easy board to etch and drill, while forcing me to learn to soldier SMT components. Now Im thinking id like to mount the chip on the top of the pcb attached to VIAS that connect to tracks on the bottom which lead to headers.

Now here is where im stumbling a little bit. What is the easiest way to make VIAS on a home etched pcb? Im thinking you could just put a pad on the top of the board and the bottom with the hole drilled. Fill the hole with flux and soldier both sides? Is there a better, faster, more standard way to do this? The next thing is cutting the copper clad, the kid on JumperOne just cut it with something that looked like tin snips, but I know if you were to just sink cutters into a perfboard it would definately screw it up unless you score it first. Do you just score clad with a razor down through the fiber glass? The last thing is the transfer, Lining up the bottom and top seems rediculously hard especially if your using a clothes iron. Ive seen people you laminating machines but I cant afford one of those, has anyone tried to use a heat gun? I know the cheapest one at home depot has like 400 and 750 degree settings, is that way to hot? Clipping the aligned transfers down with alligator clips and then just blowing a heat gun at it seems like the easiest way, if it works without starting the paper on fire.
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Comments

  • LeonLeon Posts: 7,620
    edited 2012-04-18 - 15:36:21
    You have two choices if you want vias on home-made boards: insert wire and solder it to the top and bottom and bottom pads, or use special eyelets that are inserted, peened over, and soldered. Flux won't work, it isn't conductive.

    I make double-sided boards with two transparencies, lined up and stuck together with tape, with the laminate between them. Each side is exposed in turn. Most of my boards are single-sided.
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-04-18 - 15:44:04
    Hmm do you have a name or # for the eyelets? I wasnt a saying the flux was conductive I meant if you flux in the hole the solder the pad on each side the solider would just flow through the hole and stick to the pads, would this not work without the wire? Just a bad idea?

    How do you keep the tape from melting? Your using real transparencies do these laminate the board? I was just going to use glossy paper.

    Oh yes I forgot to ask how or if ou can silkscreen and soldier mask homemade pcbs?
  • Duane C. JohnsonDuane C. Johnson Posts: 955
    edited 2012-04-18 - 15:46:11
    Hi;
    I'm thinking you could just put a pad on the top of the board and the bottom with the hole drilled. Fill the hole with flux and soldier both sides?

    This does not work. You need to put copper wire through the hole first. I use 24 to 26 gauge tinned wire. Put the wire through the hole, bend it over and clip short. This works well.
    something that looked like tin snips

    Yes, they are tin snips and they have a long lifetime.
    Scissors don't cut it.
    score clad with a razor down through the fiber glass

    Razor blades or the heavier utility knives will not do it.
    Lining up the bottom and top seems ridiculously hard

    I start with 2 large sheets of Mylar and tape 1 edge together. I then tape the transfer materials to the inside surfaces. Now that they are lined up you can slip the board in between. and iron away.

    Duane J
  • LeonLeon Posts: 7,620
    edited 2012-04-18 - 15:47:56
    Hmm do you have a name or # for the eyelets? I wasnt a saying the flux was conductive I meant if you flux in the hole the solder the pad on each side the solider would just flow through the hole and stick to the pads, would this not work without the wire? Just a bad idea?

    How do you keep the tape from melting? Your using real transparencies do these laminate the board? I was just going to use glossy paper.

    Oh yes I forgot to ask how or if ou can silkscreen and soldier mask homemade pcbs?

    Solder won't flow properly in the hole, and it won't be reliable.

    I use photo-etch - no heating.

    Silk-screen and solder-mask can be done at home, but it's difficult. It's not really necessary.
  • Duane DegnDuane Degn Posts: 10,055
    edited 2012-04-18 - 15:49:42
    I agree with Leon. I'm pretty sure the homemade vias are done with wire passing through the board and soldered on both sides.
    First of all I accidently ordered some surface mount EEPROMs (http://search.digikey.com/us/en/products/24FC64FT-I%2FOT/24FC64FT-I%2FOTCT-ND/2651408) I meant to get the dip version.

    Wow, I didn't realize they make EEPROMs in that small of a package.

    It looks like it doesn't have any address pins.

    I'm curious about what you want to do with 8KB EEPROM?
  • PublisonPublison Posts: 11,233
    edited 2012-04-18 - 15:55:26
    First of all I accidently ordered some surface mount EEPROMs (http://search.digikey.com/us/en/products/24FC64FT-I%2FOT/24FC64FT-I%2FOTCT-ND/2651408) I meant to get the dip version. So I figured a good simple start may be to just make a simple breakout board for one of these EEPROMs that will slide into an 8 pin dip socket. This will give me such an easy board to etch and drill, while forcing me to learn to soldier SMT components. Now Im thinking id like to mount the chip on the top of the pcb attached to VIAS that connect to tracks on the bottom which lead to headers.

    Breakout board could be found here among of a dozen places. Just search for SOT23 to DIP:

    http://www.sparkfun.com/products/717

    Suitable headers are like this:

    http://www.ebay.com/itm/Machined-Pin-Header-male-40-round-gold-machine-pins-x4-/180738067149?pt=LH_DefaultDomain_0&hash=item2a14d40acd#ht_2120wt_698
  • pedwardpedward Posts: 1,583
    edited 2012-04-18 - 16:03:34
    Duane Degn wrote: »
    I'm curious about what you want to do with 8KB EEPROM?

    Me thinks he mistook 64Kilobits for 64Kilobytes. Don't get me started on Kibibytes!!!!
  • RaymanRayman Posts: 10,282
    edited 2012-04-18 - 18:01:22
    Personally, I would recommend ExpressPCB, you can get 3 boards in 3 days for $51. Comes with free software.

    If that's too much, you can use BatchPCB (from Sparkfun.com) and get them cheaper. Maybe use free version of DipTrace to draw it.
    I haven't used BatchPCB, but it looks good... Especially, if it's a small board...

    How much is to make your own boards anyway? Last time I tried was with some kit for RadioShack...
    I don't remember the price, but I bet it was at least $30 or so...
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-04-18 - 18:06:32
    Well it has 2 leads on one side im guessing it is for sclk and data, and the tree on the other are address pins, The listing says KB not Kb so im assuming its 64kilobytes, not bits capital B is usually standartd for bytes. If im wrong o well i wont be doing anything with them, like I said i ordered the wrong part anyways lol. Im just using it as a simple start to surface mount soldiering and pcb etching.

    Hmmm just looked at the datat sheet, well these sots packages are useless you as there are no address pins so I guess it would only be useful if it was the only i2c you wanted on that bus wich kinda sucks, unless its for a non expandable product. Ok so the damn thing say 8kilo X 8 which is 64,000 i guess that is only 8 kilo bytes. Why does the it say 64KB not 64Kb?? Do electronics distributors not follow this convention? Shoulda known 56 cents was to low in quantity's of 1!! Guess there ok smt practice.

    As far as silkscreen and solider mask goes, the mask is a but useless unless your gonna make small smt boards, but id like to silkscreen since im trying to build a kit. Would a t-shirt shop be able to screen the boards, sorry if that is completely dumb sounding but idk anything about silkscreen nor do i much care. I just want to get labels on my board, and maybe a nice color soldier mask!
  • pedwardpedward Posts: 1,583
    edited 2012-04-18 - 18:29:34
    Memory has always been rated in bits, 4Mx1 is 4Megabits x 1 bit wide bus. 8Kx8 is 8K units by 8 bits per unit, for 64K total bits.

    You want a 24LC512, which is 64Kbytes and 512Kbits.
  • Duane DegnDuane Degn Posts: 10,055
    edited 2012-04-18 - 18:37:10
    I think Digi-Key's practice of using all caps in product discriptions aided in the misunderstanding.

    I wonder how many times something like this happens? I know the bits vs bytes thing has bit other forum members.

    In case you're wondering, there's a link to a 64KByte EEPROM in this post from your homebrew protoboard thread back in May.
  • RaymanRayman Posts: 10,282
    edited 2012-04-18 - 18:41:10
    I wonder if everybody gets burned by that... When I first started, I got some 128kB chips from Digikey thinking I was going to have all kinds of extra space...
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-04-18 - 19:30:24
    Well it was a buck no biggie next time i wont assume anything based on the case of letters :)
  • kwinnkwinn Posts: 8,475
    edited 2012-04-18 - 20:12:35
    Well it was a buck no biggie next time i wont assume anything based on the case of letters :)

    Always a good idea to download and double check the data sheet.
  • photomankcphotomankc Posts: 929
    edited 2012-04-18 - 21:20:54
    Ive been using the PulsarPCB FX product to make some double sided stuff and as others metioned, cut the design over-sized and use a light table (A glass coffee table and hardware store clip-on light is my light table) to line up some registration marks you make outside the PCB outline to get them lined up then I tape it up into a pouch and slip the board in between. Generally it comes out well. Transparent film would make that a lot easier. I'm pleased with what I get from the paper they use though. I just do another transfer after drilling to get a silk screen layer added. It's not nessisary but it sure is helpful when you come back and look at the board again a month later.

    What I find difficult is to remember in the design that you can't solder both sides of things like IC sockets, headers, and other items that block access to the pad they sit on. This means you can easily make an error that leaves a trace unconnected in real-life that the software thinks is just fine. There may be a way to tell DipTrace that I don't have plated through holes but I haven't run into it yet. For me, it's nice to make a prototype this way and find the bugs. Then I can have a real board house (BatchPCB) make the completed and debugged version that's nice.

    I'm getting into surface mount where I can. The fewer holes to drill the better, but for me, anything smaller than 800 sized discretes and .050 lead pitch on IC's is a bear to work with.
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2012-04-19 - 07:45:26
    I use FreePCB and toner transfer for all of my PCBs. I use Tesco value photo paper, not because it is cheap but I find that it gives the least problems when trying to soak it off. Single side PCB is always curved by the lopsided copper (shrinkage?) and there can lead to problems near the corners and edges, but double sided is usually nice and flat. Having the PCB cut about half an inch bigger all round helps. Double sided ones do create a registration problem but I put some dummy holes on the design somewhere near the diagonal corners,there are usually three of these just as another clue as to which way around they should be. With a clothing iron set to full I heat the back of the paper, via another sheet of normal (70-80 gsm) paper just to prevent a bit of pulling on the photo paper's back. Moderate and even preasure over 5-10 minutes usually does the job.

    I seem to go through bouts of perfect results (for 50 thou pitch) to not far from useless. Having a second swipe at it isn't to difficult on single sided effort but if it is a double sided then it's a PITA.

    Vias have to be a piece of thin wire and so you can't put them underneath QFP chips etc, I usually use DIP chips and often with bases so that isn't too much of a problem.

    I did see a video of how to through plate the holes with conductive ink and then electoplating the entire set of holes, before the tracking were etched. The list of chemicals that were required would probably bring a lot of interest from the authorities!
  • Christoph_HChristoph_H Posts: 31
    edited 2012-04-19 - 14:59:04
    I've made two or three small double sided boards at home some time ago. I've used photosensitive pcbs so I can't comment on the toner transfer specific questions. Actually I've also tried that method and failed so many times that I switched to the photo process...
    For vias I used simple copper wire. You can cut the ends nearly flush using precision wire cutters. I quickly learned that in my process the registration errors are not the greatest source of error for through hole parts/vias; it's hand held drilling with my dremel. :)

    Regardless of the error source it helps to keep the layout "simple" on one side. For instance use the top layer for all fine pitched smd parts and fine circuit traces and use larger pads on the bottom side. That way if you drill from the top any registration error you make will only lead to the via being off-center in the larger bottom pad.
    Unfourtantely I just dont have the money to get my pcb's printed somewhere.
    When I toyed with creating my own pcbs for the first time my train of thought was similar. Today it's clear to me that is not correct (anymore).

    You can get pcbs professionally manufactured for _really_ low prices and I'm not talking about large quantities. Don't get me wrong - I still value that I can design a simple pcb in the morning, have it developed and etched until noon and solder the whole thing together in the afternoon. If I order it somewhere it takes a few weeks to arrive.
    But the cost is only a bit higher compared to the cost of material I am using at home. If I factor in the time the various steps take me and the fact that the professionally manufactured pcb also has tin plating, a solder mask and finer traces (all of which I don't/can't do at home) it would be downright irrational to make them myself.
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-04-20 - 11:39:11
    how cheap is very cheap beciase some of the sites recommended on this forum are pretty exspensive to me 40 or less for a 1 of sounds resonable. and 120 for 10 it was more like 300 for 10.

    considering i have a press and gallons of homemade reusable etchant, my price is only time and maybe a buck or less per board for clad. im not sure what photo resistive paper cost but a ream of gloss paper is only 11 bucks or so. If my kits do well and i can boot strap myself ill definately go to pro boards.. but then id be buying 50 to 100 so itd be alot more reasonable. trust me id love to pay for nice boards but i really cant afford it. if i really want nice boards my best option is to etch a working prototype and then try to get some funding. i have access to do this but im not sure if funding is the way to go. this is a decision ill make when i have a working board etched.

    im acually hoping i can find an intrested party who could pay for pcb and then i will just pay them the cost of the board from each sale. once again before i asked neone i knew for help with this id like to have a test etch, itd suck to get a batch with an error lol.
  • photomankcphotomankc Posts: 929
    edited 2012-04-20 - 11:49:54
    The only thing I disagree on is that the design cycle on low cost PCB is so slow when you are testing an idea. Waiting 3 weeks only to find that left out a trace in spot you can't fix is a real bear. If I goof a home PCB I know I can make another with the fix in a few hours.

    Once I know it works then I can clean it up for plated through holes and little traces and send it off and be resonably certain my thingy is going to work when it comes in.
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-04-20 - 12:58:42
    Leon are the prices for 8 boards or 35x8 is the min order? 35 for 8 10x10 is pretty cheap! That's usually single board price
  • LeonLeon Posts: 7,620
    edited 2012-04-20 - 14:00:26
    Most of the cheap offers are for 10 boards. For instance, 10x 5 cm x 5 cm boards for $9.95: that's under $1 each. I've placed three orders with them and the boards arrived in under two weeks, here in the UK. Most of that was in the post, they actually took three days in production.
  • Christoph_HChristoph_H Posts: 31
    edited 2012-04-20 - 14:14:01
    how cheap is very cheap
    Depends on size. See for yourself - Leon has already posted a link to ITead. Prices at seeed are similar, see http://www.seeedstudio.com/depot/fusion-pcb-service-p-835.html.
  • LeonLeon Posts: 7,620
    edited 2012-04-20 - 14:22:37
    ITead and Seeed use the same board manufacturer. ITead's service seems to be faster.
  • crazy8crazy8 Posts: 1
    edited 2012-05-01 - 15:12:16
    I'd have to agree with Christoph_H, whenever I try to make my own i either mess it up and have to do it again, or hurt myself, haha
    I use pcb solutions cause they're local to me and they don't gripe about my small orders.
  • idbruceidbruce Posts: 5,887
    edited 2012-05-07 - 15:00:06
    Pertaining to the OPs question about plated through holes, here is something worth reading:
    http://www.colinmackenzie.net/electronics/14-pcb/25-thru-hole-plating-diy-printed-circuit-boards
  • GadgetmanGadgetman Posts: 2,436
    edited 2012-05-08 - 02:19:51
    Just tossing in my [small coinage] here...

    I have made double-sided PCBs with eyelets, and what I can most vividly remember is that putting in the eyelets is a real pain in the seating apparatus...
    And the guy who taught me to do it also reccommended that you add solder to the through-hole afterwards, to ensure a reliable connection between eyelet and copper on both sides.
    In short, it's a process mosttly used on boards that needs to 'look good'...

    EDIT: But if you want to try...
    http://www.circuitmedic.com/products/201-3140.shtml
  • idbruceidbruce Posts: 5,887
    edited 2012-05-08 - 02:44:27
    Just thinking out loud hear...

    If a person could accurately cut brass or copper tubing to PCB thickness, I would imagine these small tubes could be press fit into an undersize hole, similar to the installation of a sintered bronze bearing. I would imagine that the press fit would be a good enough connection for many PCB applications.

    Bruce

    EDIT: Then perhaps use something like a double-sided flaring tool
  • LeonLeon Posts: 7,620
    edited 2012-05-08 - 02:51:13
    Such items used to be available commercially, they probably still are. They were already flared at one end. Eyelets have been used, as well.
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2012-06-25 - 12:24:19
    Hi all,

    I have been fretting for a while now about the fact that the Prop II will be 0.4mm pitch and that would stop my little game of using toner transfer PCB making.

    I have always resisted trying the "Press and Peel" blue films (http://www.techniks.com/how_to.htm) due to their cost but I got hold of one and tried it to make a dev board for a XC95144xl which has 0.5mm pitch. Whilst I admit I had to do a small amount of touching up on the toner after it was ironed on it was certainly less than that I usually have to when using photo paper. Also to be fair to the sheet it is my fist time so more heat, less heat, more preasure, ...

    The tracks are 10 thou, and the "vias" are 60 thou pads with a single strand of 0.2mm wire soldered either side. There are a bunch of them under the chip, for them I allowed the solder to ball up (as in the ones visible) and then filed them down until the first signs of the wire appeared.

    The sheets are pricey at around £15 for 5 (28cm x 22cm) but for those fine pitch times I think that it is a simple way to get a better consistancy.

    Next I will have to go photographic. Anybody know how much useful UV comes of of those energy saving bulbs ?
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