- Published: Saturday, 23 April 2011
- Written by MrDeb
- Hits: 11232
DIY Printed Circuit Boards
for the home hobbyist
methods and mistakes
By Doug Bezaire
Making a printed circuit board for that one of a kind project can be a challenging experience at best.
I have tried most of the standard methods of actually applying the circuit design to a copper clad board then etching using several different chemicals.
But before one can apply a design to a copper clad board, a design must be produced. There are many design programs available, some free and some require to be purchased.
I personality have only tried three different FREE cad design downloads.
The first being Express PCB. An easy program to learn and the results are good. But if you have a design that you want multiple boards then you need to have Express PCB make your boards. Can get expensive. If you have never done any board designs then I suggest getting your feet wet with simple designs.
My next free download is DipTrace. A real nice bit of software that will produce Gerber files (a common file standard amungst PCB fab houses) - important if you want multiple boards. The learning curve is not to bad and using the auto-route is a nice feature but tweaking the design is necessary as I have found on most all the boards I have done need tweaking for optimal trace layout. The libraries are some what difficult to get a handle on but still learning.
The third free download CAD program is Eagle. This is a true professional bit of software with a steep learning curve. If you get serious about designing printed circuit boards then this is perhaps the one to use. But if DipTrace meets your needs then great.
A word on board design. I have done many designs but many are designed without proper layout rules. After being directed to this link PCB Design Tutorial. My boards have taken on an attractive well working appearance. Suggested reading before designing a board.
Now onto doing an actual printed circuit board.
You have your design on the computer but need to get onto a copper clad board. Several methods work, and I have tried many and for ease of applying etc. I decided on using the PULSAR toner Transfer method. Make Your Own Dry Transfer Decals and Instant Printed Circuit Boards!
Several pieces of equipment are necessary to apply your design to the copper surface.
Methods to use depends on how much you want to spend in time and money.
The photographic method involves using a clear transparency film, printing your design then placing on top of a photosensitive board, exposing to UV light then developing,and etching. If doing a large quantity of the same board then this is perhaps the best DIY but it can be expensive.
The Peel and Press method I have never tried but should be mentioned.
The toner transfer method is next on the list with different types of paper. A laser printer is required as an ink jet printer prints with water soluble ink which would dissolve when etching the board. A laser printer prints using a plastic based toner thus its water proof. As for paper to use, excellent results can be achieved using certain glossy magazine paper or glossy photo paper, Both work but experimentation is required to achieve quality results. I have tried using both types of paper and found its hard to remove the paper after laminating the design to the copper clad board. The solution I am presently using is the PULSAR PAPER. Make Your Own Dry Transfer Decals and Instant Printed Circuit Boards!
This paper can be expensive as I found out when first started using. Learned how to conserve paper by not using a whole sheet for each design. Print your design on plain paper, marking the plain paper with an arrow to denote top and direction. Then cut out transfer paper slightly longer than printed design to aid in taping to board later. If doing a 2x board, print the bottom normal while the top and silk screen is printed using mirror. A quick mention on the silk screen layer. If using the PULSAR transfer foil for your silk screen, you need to print your silk screen in black, apply to the board then apply the foil. The foil will only transfer to the plastic toner (avoid painting the board to apply the silk screen). Have found that using clear 8 ½ X 11 full sheet labels (Avery 8665), printing your silk screen pattern using normal not mirror then applying to your etched board works rather well and is cheap. Paint your board first then print onto the clear labels with a contrasting color using an ink jet. Be sure to clear coat to prevent moisture from smearing your silk screen.
Just poke out the mounting holes. Solder any vias before painting and applying as the board will look better without a bunch of burn marks.
This board was painted white then printed the silk screen in Red. Looks pretty good IMO.
NOTE the arrow on left side of plain paper printout. The transfer paper is cut slightly longer than the printed design and the arrow denote direction the paper went into the printer. Have printed and taped the transfer paper to the plain paper print out but when I printed out onto the transfer paper, the pattern was off and wasted some transfer paper.
Apply the transfer paper, glossy side up to the printed area on the plain paper, taping on one edge only (taped edge into printer first). After you have your design printed you need to laminate to the copper clad board using heat. An ordinary clothes iron works pretty good and using a dowel improves the transfer (see the PULSAR website for tricks and tips) that work regardless what paper you use. I started using the iron method but after purchasing a GBC laminiator for under $75 my transfers are perfect. Nothing left behind when removing the paper. NOTE when printing your design use the highest density and dpi on your printer. 1200Dpi works very well. TURN OFF ECON MODE.
A note on using filled areas, some printers won't apply enough toner if the areas are large and solid.. I found using a cross hatch instead of a solid area works well. Also found using the filled areas as ground plane aides in the overall design. Have made several mistakes in this area and learned to be generious with the clearance of the filled plan to traces. .060 seems to work well.
If using the iron, be sure to press hard and long to “melt” the toner to the copper board. When using a laminiator I insert in all 8 directions several times to the point I can hardly hold the board. I apply the paper to be laminated by taping with blue painters tape (do not use scotch tape, it is very hard to remove from board) on one edge. Found this prevents the paper from bulging while laminating.
Before we get ahead of ourselves, you need to C L E A N the copper board of any and all oils and oxidation. Several methods work well such as scotch bright pads, wet dry 600 sandpaper as well as #0000 steel wool. My preferred is the steel wool as its cheap and does a very good job. I first apply a small dab of dish soap to board then scrub in several different directions under running warm water. DO NOT TOUCH the cleaned surfaces, just the edges. When water fails to puddle or stick to the board when slightly tilted, then the board is clean.
Note the left side of this board compared to the right side.
The left side has no puddles sticking to it.
After cleaning then wipe dry w/ a lint free tissue or paper towel. Some suggest using Rubbing Alcohol to finish cleaning the board. Have never seen a difference.
After applying the transfer paper then laminate. I use a Laminator I purchased from PULSAR but numerous units are available on Ebay.
Insert into laminator with taped end first. Insert several times to be sure the paper is adhered to the board before inserting in a different direction. BEFORE LAMINIATING, pre-heat the laminator for at least twenty minutes before using.
After inserting in all eight direction counting paper on top as well as on the bottom
and while the board is still HOT, run the board under cold water to cool. If you remove while hot the pattern might stick to the paper and ruin your pattern.
Repairing broken traces is accomplish by using an ultra fine sharpie pen. Before using, wet the tip by twirling between fingers so the ink flows towards the tip thus wetting it with excess ink. Then just dab on. If you just draw without slightly dabbing, the ink won't be very thick. Apply so the copper is not visible through the ink.
After cooling the board, the PULSAR paper practically falls off where as the magazine paper or photo paper will require some light scrubbing. Inspect the paper for any traces that failed to transfer and repair if necessary.
Note the board edge that is left behind. No big deal but ALL the printed traces transferred perfectly.
If doing a 2x (double sided board) the process requires additional steps to register the traces to both sides..
When doing a 2x board, insert in your design three mounting holes on three corners, drill out with a # 65 wire drill, then using stick pins to register one side to the opposing side. The pins fit very tight with no wiggle. I applied the mounting hole targets after inserting the filled planes so the mounting hole targets failed to show up very well. I just drilled out three component mounting holes as far from each other as possible.
Note the three pins in each board.. This method works rather well. There are several other methods that work but I found this to be the most dependable.
After applying the pattern to one side I have found that painting the opposite side with paint then etching (print the pattern BEFORE painting to prevent the paint from adhering to the rollers in the laminator) proves to work very well. Prevents etching the opposite side accidentally by tape creeping up or ?.
After paint has dried then etch your board, dry board off, remove all the toner as well as the paint using acetone but found lacquer thinner works the best. Clean the opposing board side, register the pattern using the pins, tape one edge, laminate, paint etched side of board then etch the second side. Remove all the toner and paint.
I then drill out all the component holes (NOTE when designing your pattern, enlarge the pads and use a .020 or .015 inch hole size. The little etched hole acts as a center punch dimple for your drill.
A suggestion on drilling, have experimented using a drill press but recently found that using a # 78 drill bit mounted in a hand held Dremel tool, the bit will drill dead center in the small etched holes. Follow up with # 65 or #68 drill bits. Found 99% of the holes will use these two bits. After I tried this method my mounting holes are all aligned perfectly. After all the drilling is done, lightly sand the board with #600 wet/dry sand paper (dry). This removes the burs as well as polishes the copper for soldering.
A good supply of wire gauge drill bits is Widget Supply: Sets of Drills . These are HSS bits that work pretty good. The carbide bits are more money and break easier so I go with the HSS bits.
As for etching chemical, I like the 1 part Muratic acid mixed with 2 parts hydrogen peroxide. Can re-activate using more hydrogen peroxide as I understand it. Also applying air via a bubblier will help re-activate the solution. I have yet tried either method. My plan is to use a narrow long plastic container, place a plastic tube on the bottom with slits in the tubing. Attach to an aquarium bubblier. This will agitate the mixture to aid in speeding up the etching process.
CAUTION do not allow the board to etch in the solution too long as the etchant will undercut the traces and result in a poor printed circuit board. Wiping with a cloth wearing latex gloves and safety glasses, removing the dull copper finish will speed up the process.
NOTE copper clad boards come in several different weights based on the amount of copper per square inch. The less copper the faster the etch process but use heaver boards for high voltage traces.
If ordering from PULSAR, be sure to order some FREE copper clad boards. These are remnants but usable. These are ½ oz. Boards so etching is very quick and the board is thin so you can hold up to a light source and see any broken traces.
The board pictured has .060 trace to filled plane clearance as well as larger pads Thinking of going even bigger pads. These are .060 wide and .070 tall. All the traces are .020 wide with a few exceptions when going between pins. Then drop down to .015.