Making Printed Circuit Boards at Home

By Bryan Ackerly, VK3YNG
(Updated, 14 feb 2004)


In previous years, amateurs used to resort to use of veroboard or used "dead bug" construction to make circuit designs. The proliferation of surface mount packaging has made these techniques more inappropriate. Many amateurs have not considered making their own PCBs for projects because of the complexity of the process. Recent developments in technology have made this process a lot simpler and cheaper. This paper describes a cheap, repeatable and reliable method making prototype PCBs using the new Kinsten presensitised PCB material.

1. Introduction

The method outlined here will allow PCBs to be made with repeatable results for track width and spacings down to 0.2mm (0.008"). This should be more than adequate for experimenting with commonly available surface mount and PTH components.

2. PCB material

    The Kinsten PCB material is available from several Australian suppliers (2 ,3 ,4 ,5 ) in the following formats:
Double sided material available in 0.4, 0.6, 0.8, 1.0, 1.2 and 1.6mm thickness (Note: only some suppliers stock all thicknesses).
Single sided material in 0.6 through 1.6mm thickness
Most of these are available in 150 x 300mm size with 1 oz (35um) copper thickness with the 1.6mm thick board also available in 2oz (70um) copper thickness.
The 1.6mm board is also available in several other sizes from 100x150mm through 300x450mm.

3. Required Equipment

3.1 Personal Computer

A personal computer is necessary for designing artwork. Most amateurs own something in this area.

3.2 PCB design software

There are a number of PCB design packages available either free or cheaply through the Internet. The author’s example uses the Protel  design system which is no longer classed as a cheap package, but there are older versions of it available. A number of amateurs have access to older versions of this software which may be applicable.

3.3 Ink Jet printer and film

Best results seem to be from an ink jet printer. A laser jet printer does not seem to give as good results. Through experimentation the best combination seems to be using an Epson   printer with >720dpi resolution and the use of Epson film (part no S041063). A box of this film (30 sheets) will set you back about $100, but if used properly a full box will last a long time. There are cheaper films available but they do not produce as good results. Consider purchasing among a number of people to distribute costs. This film is chemically treated to react with the ink. Do not handle the film directly with your fingers!!!

3.4 Print Settings

DO NOT try to print top layer tracking normally and then reverse the film. This will create track width problems due to the thickness of the film. It’s a good idea to set up custom profiles for print settings. For example:
Top layer draft:  Low resolution, flipped orientation
Bottom Layer draft: Low resolution, normal orientation
Top Layer Final:  Highest resolution, film plotting, flipped orientation.
Bottom Layer Final: Highest resolution, film plotting, normal orientation

3.5 Exposure box

Commercial exposure boxes are relatively expensive, some costing many hundreds of dollars. A simple wooden box containing a few fluorescent lamp holders and a cheap digital "egg timer" that goes "beep" when the time is up works out a damn sight cheaper! In fact at the time it was found to be cheaper to buy a couple of lamp fittings from the hardware store and discard the tubes than to buy all the bits separately. Plate glass is used for the top of the box and a heavy wood cover with a thin lining of foam rubber is used as a lid. The lamps are old UV Eprom eraser tubes. The box must be operated with the lid in place as UV light will damage your eyes. The original fluorescent lamps will work but exposure times will be much longer.

Figure 2 - Exposure box and Timer

3.6 Developing tray & developer

The developer used is sodium metasilicate. This is available in 50g bags at about A$2 each which makes a litre of developer. Although the manufacturer indicates that the solution has a working life of 8 hours, the author has found that premixed solution is a lot more convenient and will be usable for months provided it is not contaminated with used developer. Another option that will develop a lot quicker is sodium hydroxide, but the temperature (use 28C) and timing is critical as if left for a few seconds too long it will remove everything!

For the developing tray use a lid from an old floppy disk storage box. Don’t use acetone in this tray as it may attack the plastic.

3.7 Etching tank

For an etching tank you will require a chemical proof preferably clear glass or plastic box, a heater and some form of agitator to circulate and/or airate the solution. A commercial etching tank suitable for doing boards up to 200x250mm is available for about A$75 including heater, air agitator and PCB holders.

Figure 3 - Kinsten ET10 etching tank from Kalex and Computronics

3.8 Etchant

There are a few options for etchant. Ammonium persulphate is preferred by the author and costs about A$12 for 600g. This is a clear solution which turns blue as the solution turns to copper sulphate through use. Ferric chloride is preferred by some, but it’s messy, has a habit of causing permanent brown stains and has the disadvantage that you cannot see the board while it is etching. Another option used by some is Hydrochloric Acid and Hydrogen peroxide. Depending on the strengths of the solution this method is extremely quick and the reaction provides its own heat. This solution will etch a board in seconds and if you are not careful a few seconds later it may take all the trackwork with it.  Just the thing for making fibreglass insulators!

3.9 Drilling and drills

This is one area that takes a bit of care. Most people prefer to have PCBs made of fibreglass since it is a lot more robust and predictable. However, this material is extremely abrasive and standard high speed steel drill bits will do about 3 or 4 holes before they start to become blunt and produce burrs. The first indication of this is burrs on the underside of the board followed by complete removal of underside copper lands.

To consistently drill clean holes with sharp edges requires the use of solid Tungsten drill bits that are commonly used by the PCB industry. There are a number of suppliers ( 4 ,5 ,8 ) of these, but don’t expect to be able to get them from you local hardware store or electronics hobbyist supplier. These drills are available in sizes from 6.3mm down to 0.2mm but they are not cheap and the smaller ones are extremely fragile. A reasonable bench press is required for these drills as any vibration will destroy them. Use a spindle speed of around 7,000RPM for drill sizes around 3mm and up to 28,000RPM for sizes around 0.7mm. These drill bits will do around 10,000 holes before they go blunt and generally you will break them before this happens. The drill bits shown in figure 4 are several years old now and are still sharp even after many thousands of holes! Only consider sharpening them if you have access to a diamond grinding wheel.

Figure 4 – Solid Tungsten drill and router bits

3.10 Protective coating

A protective coating is necessary to protect the board from tarnishing especially from contact with fingers. Generally any pressure pack clear protective lacquer will work but thick layers are difficult to solder through. There are specialised versions of this protective lacquer that can double as a soldering flux.

There are also "electroless tin plate" solutions available giving a dull tin finish. The trick to using this solution is to use distilled water rather than tap water as impurities in the water can compromise the plating results.

4. The process steps:

1) Create trackwork on the computer: This should always be done from the component side. Always be sure to include a border showing the final board outline.
2) Print off a draft copy of the trackwork layers(s) as a check copy and a template for the film. Use the printer dialog box to select flipped artwork for the top layer. Make sure the "add holes" option is checked on your PCB software when printing.
3) Cut out a piece of film approximately 20mm larger than the artwork.
4) Stick this film down MATT (non-shiny) SIDE UP onto the paper with thin sticky tape.
5) Put the paper back into the printer and print the artwork again using the Final print setting. Leave the film for a few minutes for the ink to completely set.
6) Remove a sheet of Kinsten PCB from its packaging. With a pen, mark out two lines 3mm and 6mm larger than the required PCB, plus an allowance on one edge to hold the board in the etching tank.
7) With the aid of a steel rule, cut along these lines with a Stanley knife and then carefully remove the thin 3mm strips of protective coating material.
8) Cut through these exposed 3mm wide strips with a hacksaw. Be careful not to bend the board if using thin material as this damages the coating.
9) File any burrs off. This is extremely important as any lifting of the film during exposure due to the board not being completely flat will cause registration problems.
10) Remove the film from the sheet and cut off any remaining sticky tape. (Peeling it off will leave the glue behind.)
11) Put the film dull side (printing side) up on the light box. Carefully remove the protective sheet from the PCB material and place it face down onto the film.
12) Cover the light box and enable the UV light. Depending on light intensity this will take somewhere around 2 to 5 minutes. Use a digital "egg timer" to ensure that you don’t over expose the board.
13) Remove the PCB from the exposure box and put it into the developing tray. Add a small amount of developer (enough to completely cover the board) and gently rock the board until the unwanted copper areas are completely free from resist)
14) Remove and rinse the board. Keep the used developer for the time being.
15) Hang the board in the etching tank. Depending on temperature and how used the etchant is, this may take anywhere from 5 to 15 minutes. It is a good idea to set the egg timer to about 10 minutes or so to ensure that you don’t over etch the board in case you get side tracked. Its rather difficult to put the copper back on!!
16) Remove, rinse and dry the board.
17) Place the board back into the light box and expose the board for the standard exposure time.
18) Put the board back into the used developer and agitate it until all resist is gone. Discard the used developer. (These last two steps can be replaced by using acetone if time is critical)
19) Drill the board and cut, file or route the edges to size.
20) Spray the board with clear protective lacquer. (or plate with immersion tin coating)

   Figure 5 – various stages of making a PCB

And there you have it – The whole process once the board is designed should normally take around 10 to 20 minutes for a typical SMD board. (..or a bit longer for PTH boards because of all those damn holes). Artwork should be stored in a paper envelope to ensure that the ink doesn’t bleed onto other pieces of artwork and to avoid buildup of dust and fingerprints.

5. Double sided boards

One of the biggest problems a person faces when making double sided boards is how to make both sides line up. There is a simple technique the author has successfully used many times that doesn’t require drilling alignment holes and has been used to align hole sizes well under a millimetre. The following steps outline this technique along with the pictures shown in figure 5.
1) Tape one side of the artwork printing side up on a flat white surface.
2) Put lengths of 3M double sided tape carefully along two intersecting edges about 1-2mm from the marked edge of the artwork.
3) Get the other side of the artwork and carefully align it up with the first sheet. Use holes or board edge registration marks on three major edges for this purpose. (Make sure the alignment is correct and the you are holding the artwork firmly for the next two steps as you won’t get a second chance if you get it wrong!)
4) Lift one edge of the artwork over the double sided tape and remove the protective cover from the tape.
5) Carefully sit the top artwork over the double sided tape and tap it at few points to ensure it sticks. Don’t wipe your finger across it as this tends to make the tape "curl"
6) Lift the other edge of the artwork and remove the cover from the other double sided tape.
7) Carefully let the top artwork down and tap it in a few places to ensure it sticks.
8) Put the PCB material inside this "artwork sandwich" for exposure. 1.6mm board should wedge quite firmly between the sheets so there should be no movement when the board is flipped to expose the other side
9) When exposure has completed, put a folded blank piece of paper between the artwork sheets as otherwise the ink will tend to "bleed" from one side to the other over time making the artwork unusable.


Figure 6 – Technique for double sided board artwork

6. Conclusion

The Kinsten PCB material along with suitable PCB design software allows making of PCBs quickly. The cost and simplicity of the system makes it easier than ever for amateurs to make PCBs for their projects. Now you can confidently experiment with some of the more interesting devices that have recently become available.

7. References

1) Kinsten is a trademark of Kinsten Industrial Corp.

2) Computronics Corporation , Bentley Western Australia

3) Wiltronics Research , Ballarat, Vic

4) Kalex Photosensitive Products 718 High St Rd, Glen Waverly, 3150. Ph +61 (0)3 9802 0788

5) Mektronics Co Pty Ltd , U3/67-71 Industrial Drive Braeside 3195.

6) Protel is a trademark of Altium Limited .

7) Epson Corporation ink jet printers

8) Farnell electronics , Chester Hill, NSW