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Author Topic: Problems making homemade pc boards  (Read 497 times)
NR5P
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« on: May 12, 2005, 07:00:53 PM »

I'm just starting making circuits on pc boards and recently I wanted to put a circuit I made for a VFO on a board for a receiver I'm building.  I got one of those kits at radioshack which came with a resist ink pin(regular marker), resist ink remover, and etchant solution.  The first time it disolved most of what was under the etchant and the second time I put as much as i could on and it came out usable but ugly and spots all over where some of the coper disolved in places it shouldn't have.  I was wondering if any of you knew either a better way of making these or better materials to use.  Also is there a cheap replacement for the etchant without buying the kit.  I asked the people at radioshack if they could get just the etchant without the kit and they said no, but I thought for sure I've seen it before.  Please share your experience, I didn't leave it in to long either because I checked it,  Just doesn't seem like the marker is a good resist.

Thanks, Nathan NR5P
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KG4RUL
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« Reply #1 on: May 12, 2005, 07:55:05 PM »

I have never had any success with the resist pens.  I have always done home PC boards by using a photoresist or using dry transfer decals as resist on the board.

Here is a supplier of pre-sensitized board materials and dry transfer decals.  They also have the ferric chloride etchants and electroless tin plating kits.

http://www.philmore-datak.com/DATAK.htm\

You can use one of the available shareware circuit board layout programs or another drawing program to produce a laser printed transparency which serves as a positive film for exposing the photoresist.

You will need a small drill press to accurately drill your holes.  I use a dremel tool with the drill press acccessory and carbide drill bits.

Dennis KG4RUL
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KZ1X
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« Reply #2 on: May 12, 2005, 08:18:20 PM »

Use ammonium persulphate instead of ferric chloride.
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G4AON
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Posts: 528




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« Reply #3 on: May 12, 2005, 10:42:11 PM »

Nathan

I've been making print boards, by hand with etch resist pens, for many years without any real problems. I don't know which etch resist pen you have been using, but the overhead transparency marker pens sold in the high street shops don't work very well. The "Dalo" pens are very good and leave what looks like blue varnish on the print board. They are available from Maplin in the UK (www.maplin.co.uk), search for Dalo. The Dalo pen was pretty much a standard item for hand made print boards a few years ago, but might not be so easy to find these days.

Dave
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AP2WF
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« Reply #4 on: May 13, 2005, 12:13:11 AM »

I have been making PCBs manually for years for my home brew projects. The specific kits are not awailable here so I used the followings that you may also try with success;

    You need the following stuff:
        1- Paint Brush with the desired number (I used 01 mostly).
        2- Any cheap quality paint with any colour (ordinary anamel paint will also do).
        3- Ferric Chloride (Caution must be taken when making solution in water).
        4- Glass or plastic dish for etching.
        5- Copper Clad or PC Board cut to desired requirement.
        6- Drilling equipment for the desired size wholes.

Wash the copper clad board surface with water and soap if dirty and wipe it. Now paint the traces manually and let it dry. It will dry quicker under the table lamp heat. Drill the wholes when dry and then etch it with the foil side down and aggitating the Ferric Chloride Solution. The etching will also be faster if the solution is a bit warm. Wash the etched board in a lot of water and remove tha paint with any cheap solvent. Thinner may be used. Wash the board again after removing the paint and wipe it to dry. The precision of your painting and drilling skill will yield the quality of results. No doubt it involves a lot of patience. Good luck.

Wasay AP2WF
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K5DVW
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« Reply #5 on: May 13, 2005, 05:46:58 AM »

What you might have discovered is that finger oils really screw up the process. First, they mess with the adhesion of the pen ink, and second, they can keep the etchant from working on the copper.

I've had good luck with pens, including the Sharpie brand of pens by first using clean steel wool on the copper PCB face I'm about to etch and then handling the the whole thing with gloves.

Also, it helps tremendously if you warm up the etchant solution. It etches faster and leaves less time for the etchant to seep under the resist pen markings. Something around 100F will do wonders. I've seen people use heat lamps to keep the etchant bath warm.

Then again, I've completely given up etching my own boards because of the trouble. I can do a better and faster job assembling things dead bug style on a piece of copper clad. I've done circuits this way that work to several GHz. Makes a great ground plane.
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K5LXP
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« Reply #6 on: May 13, 2005, 06:22:41 AM »

2nd the vote for ammonium persulfate, ferric chloride is slow, messy and a disposal hazard.

It's tough to make a decent looking board with sharpies and decals.  Very time consuming, difficult to correct mistakes and the results are less than stellar.  After trying a number of different processes, I have settled on PnP BlueCad, which is a toner transfer process.  You design your PCB on the computer, either with real CAD software or even just a simple image editor, print the image (reversed) on the PnP material and heat transfer it to the copper.  After etching it looks like a professionally made board.  Though somewhat dated I have a web page on the topic:

<http://www.qsl.net/k5lxp/projects/PCBFab/PCBFab.html>

If all of that is too much messing around you can go to <http://www.expresspcb.com>, download their free software, lay out your board, send them the file and your boards show up in the mail.


Mark K5LXP
Albuquerque, NM
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K1CJS
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« Reply #7 on: May 13, 2005, 07:16:29 AM »

As someone else pointed out, skin oils play heck with the process.  I've used the disposable latex gloves and a little TLC when doing mine, after I wipe the board down with a good mild degreaser.  I use 99% isopropyl alcohol and a paper towel.  Then a rinse wipe with distilled water on another paper towel.  

The secret is getting the board clean before applying the resist marker so the marker adheres well.  Also, any oils or contamination will slow the dissolving of the copper--you have to get rid of them.

I think you'll find you'll have better results if you insure everything is degreased, clean and dry before you begin the marking process.

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WA2DYA
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« Reply #8 on: May 14, 2005, 06:59:50 AM »

Lots of good advice by from board makers here.

I once made some simple boards using 'frosty on the rool' scotch tape as the resist.  I made the round solder pads by punching them out with a paper punch.

Board making is very tedious work.

---  CHAS
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W9SZ
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« Reply #9 on: May 18, 2005, 02:42:38 PM »

I've been making boards with Datak ER-71 negative-acting photoresist and ER-8 resist developer for years with excellent results.  This may be more involved than you care to get, but it DOES give excellent results!

These days I make the circuit pattern with a CAD program.  My favorite is CorelDraw.  This enables me, with a couple mouse clicks, to turn my artwork into a negative.  I print it on a laser printer on transparency film.  It usually requires some touch-up with a Sharpie pen to darken areas that print too light.

I clean and coat the board exactly per the instructions that come with the ER-71 photoresist.  I found you really have to coat the boards in a dark room with a bug light (yellow).  A regular incandescent bulb does deteriorate the quality of the resist.

I expose with a contact printer in bright sunlight for 3 minutes, then develop in the ER-8 for a minute and place the board face down on a couple layers of soft paper towels for a few seconds to drain, then carefully lift and let dry.  Sometimes I need to touch up areas of the photoresist with the Sharpie pen, but it's usually just little pinhole areas. I develop in ferric chloride.  Note - Radio Shack DOES sell ferric chloride solutions individually in bottles, not as part of a kit.

If you use Sharpie pens, ammonium persulfate tends to wash it off.  Sodium persulfate doesn't have this problem.

I've made multiple circuit boards of several key circuits with this technique and haven't had a bad board yet.  This includes about 10 of the KK7B no-tune 560 MHz microwave LO's, various microwave circuit boards up to 24 GHz, and recently quite a bit of surface-mount boards.  The Datak materials do very well with very tiny traces.
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N3EF
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« Reply #10 on: May 19, 2005, 08:36:38 AM »

  Iv'e had good success using the methods from the following website as well as using the software to make the patterns from expresspcb.com

http://www.fullnet.com/u/tomg/gooteepc.htm

Eric N3EF

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