I have been fortunate enough to have been taught how to make professional quality printed circuit boards by two people who have developed totally different methods of achieving very good results. I hope what I'm about to relate may assist you producing your own printed circuit boards with less hassle and more success than you may previously have done so.
I shall two methods since one method uses an ultraviolet flat bed exposure box and the other does not.
The first method I shall describe uses ultraviolet exposure of light sensitive printed circuit board material initially answers already been described in many different articles. What differs about this method is the way that the printed circuit board is etched.
In this method, three photographic trays are used. The first photographic tray contains full strength ferric chloride solution, the second photographic tray contains half strength ferric chloride solution and the third tray contains water.
Photographic tongs are used to hold the printed circuit board whilst it is being etched. The secret of this method are camel hair brushes which are used to lightly brush the etching solution over the surface of the printed circuit board.
Any of us who of made printed circuit before will know the problem is that the board is etched away unevenly resulting in some parts of the board being over etched and other parts of the board being under etched. The camel hair brush over comes this problem by agitating the solution over the printed circuit board where it is needed most, resulting in a near the effect printed circuit board.
As you may already guessed, once the board approaches that point where it is nearly etched, it is then transferred with with the tongs to the half strength solution and is finished off in this half strength solution to give a virtually perfect result. It is then washed off in the third tray of pure water and examined carefully. Any parts which of been overlooked can then be easily attended to by returning it to the half strength solution in the second tray.
The results obtained by using this method are quite remarkable, and so simple when you stop to think about it. I would have great difficulty in telling the difference between a professionally made printed circuit board and the printed circuit board produced by my colleague using this method.
When asked him who had taught him to make print circuit boards this way he told me no one had -- he had developed the technique himself, but he had been at keen amateur photographer before he took up making printed circuit boards and he could not say you why the same techniques he used to develop photographs could not be applied to the production of printed circuit boards. Certainly the results were very impressive indeed!
I hope these notes may encourage you try making your own printed circuit boards using this technique which hopefully will produce results that you would like to have obtained, but didn't, in the past !
This is the second bulletin in the series on making printed circuit boards and describes a method which does not require an ultraviolet exposure box or expensive photo resist printed circuit board material.
It was also developed by a friend of mine who was kind enough to show me how he produced printed circuit boards using this method. I have myself used this method successfully and can recommend to you.
The copper side of the printed circuit board is printed out on a computer printer at normal size IE the size it will be on the printed circuit board. It is then cut out and sellotaped firmly over the copper laminate with sellotape over both sides and the diagram to make absolutely sure that it does not move.
Having done that, we now start using the secret weapon -- this is a self- actuated metal punch, ( the type that car thieves used the use to smash car windows in the days before laminated glass ). The spring is adjusted for minimum tension. Using the punch a hole is punched through the diagram and causes an indentation in the copper where the hole is to go. However since the spring tension is set of minimum, it is not enough to punch hole through the copper laminate -- simply to cause an indentation.
This process is repeated for every hole which will be required in the printed circuit board. The holes in the diagram show where the punches already been used. When this process is finished the diagram and sellotape are removed and discarded. This leaves the copper laminate with lots of little indentations visible under a good light.
The next step involves the use of a mapping pen. A mapping pen is bought from a stationary supplier and consists of a stick with a nib on the end, and should bring back many happy memories for those of us old enough to remember being taught to write with pen and ink at school. These mapping pens cost very little ( less than 1 pound each ) and several are recommended with different sized nibs -- broad, medium and fine -- to produce the best results.
You can buy special etch resist ink but it is very expensive and my friend and I have found that normal mapping ink is a lot cheaper and is sufficiently dense to allow printed circuit boards to be produced with it. Using the mapping pen and ink, a ring is drawn around each indentation in the printed circuit board. When this is been done, the printed circuit board is covered with little black rings where each hole is going to go. You then join up the rings using the mapping pen to complete the printed circuit board.
Having checked the board and no missing holes and no missing connections, you can now use the broad nib to ink in unused parts of the printed circuit board which do not need to be etched and can represent earth. This gives your printed circuit board a very professional finish and means of that you do not have to actually is much copper so your etching solution will last a lot longer -- a nice finishing touch if you feel so inclined?
The board is etched as previously described in photographic trays using a camel hair brush. The beauty of this system is that not only can one off printed circuit boards be produced cheaply with minimum transfers and not needing ultraviolet exposure or photo resist printed circuit board material, but also it is much easier to drill because all the holes are pre-punched.
My friend and I differ on whether to drill holes before etching or after etching -- it doesn't really appear to make much difference !
I hope that techniques I have described will enable you to make better printed circuit boards easier and with more professional results.