Methods PCB fabrication

Note: The text is auto translated from the Greek version

source: Elektor

In this article we will discuss that take shape essential copper circuits via that are realized the electric connections between the elements. We will be reported extensively in the stages that it should follow the amateur but also professional electronic, in order that beginning from the theoretical diagram that has drawn in a paper it leads to what is known as printed circuit. You will still learn how it is manufactured anyone of pcb abbey or double aspect with simple and easy way. And all these following the directives that you we give below.

In order to is materialised a any printed circuit it will be supposed we begin from the designing of lines of interconnection of elements, we advance in their transport in films and we finish with the etching and the piercing of pcb. Firstly we will speak concisely for the stages of manufacture plake'tas. Then we will analyze the each one from them more extensive using photographs and drawings.

 

The artwork

The designing of printed circuit can become with one from the following ways: With special thin felt-tip on rise paper or simple white paper. With specifically designing tools (stencils) that contain islands and lines on rise paper from white paper.  With specifically design auto transferable stickers (letraset, magictype etc) in rise paper, white paper, and in special transparent gelatin. With the help of designing programs that runs in computer, the known programs CAD, which offer facilities and crowd of possibilities.

This programs apart from the possibility simple (off-hand) transport in printer of spikes, have the possibility of printing out perfect in printers inject and laser. Certain of them have the possibility of transformation printed in form PostScript. With use of form PostScript exists the possibility of sending your drawing in special machines of photosynthesis that it is possible him they print in very high analysis in special film. In this way the final result does not have envy in nothing from a professional work. The method that has prevailed today because it has simplified all the stages is the last one. In case where the drawing of printed circuit is already ready (f.e has been published in certain periodical) then obviously we omit the stage of designing and simply we prepare the drawing for the final transport in pcb. Thus we can photocopy the drawing in rise paper or him repeat in films in some shop that has the possibility of production of special photocopies. Himself it will be supposed we make also in the other cases where the drawing has been made in paper. 

The TRANSPORT of DRAWING

The transport of drawing of printed circuit above in pcb can become with a lot of ways mainest than which they are:

With direct designing of lines with special felt-tip indelible ink above in the copper surface pcb. This way is judged ideal for simple and small dimensions pcb or off-hand essays that should be printed out immediately. With specifically auto transferable self-adhesive elements as films and islands that are stuck above in the copper surface.   With special self-adhesive artworks printed that is offered by certain magazines. With the method that forecasts use of photosensitive special spray covering pcb (as the known Positive of 20 German company Kodakt Chemie or the Photosensitive of English company Electrolube) and film. With special ready photosensitive pcb as f.e of German company  Bungard. The pcb these even if they are more expensive than simple pcb have the advantage the perfect and uniform covering pcb with photosensitive material, thing that guarantees the perfect transport of drawing.

The two last methods in combination with the designing in computer give pcb high technical specifications.

EXPOSURE OF PCB IN THE UV LIGHT

The report pcb in UV light becomes in order to are burned that points that constitute the final drawing of printed circuit and will be supposed they are impressed in pcb. It is a process similar with that of appearance of photographic film. The report PCB in the UV light becomes in the interior of specifically shaped box where a special lamp of steams of mercury of force 125  W undertakes it transports the drawing printed in the surface pcb. In order to becomes possible what it will be supposed the photosensitive pcb on her adjoin film with the help of piece of pane it is placed in distance 30 hundredth from lamp UV. 

Then it will be supposed it is exposed for 4 until 10 thinly depending on the type of film (gelatin, rise paper or other transparent paper) and proportionally photosensitive surface pcb. We stress that the lamp this in order to it functions needs in line with her catering a special inductor (tsok) similar with what we use in the pipes of fluorescence. If him you forget exists danger to be burned. Mark that the UV radiation is  VERY DAMAGING  for the eyes and should not never him you look at.

 

DEVELOPMENT

The appearance is the thinnest process because it requires experience and patience. It becomes with the help of special solution of 7-10  gr  caustic soda (NaOH) in one liter of water. In this appears to appearance pcb for 1-2 thinly the hour. After this time becomes visible the drawing that will constitute the final electronic diagram of connections. This solution becomes denser if is added extra caustic soda. Naturally this him you will make provided that the thickness of photosensitive surface is bigger than usual. Attention: this work is imposed it becomes with plastic gloves and big attention. The caustic soda is dangerous when it comes in contact with the skin.

The ETCHING

The hour of etching is holiest for the amateur that makes this first pcb, after moment it sees his labours be rewarded. Sure it is not little you see pcb be created front in your eyes. The etching can become with four ways:

1. With solution of arid chloride iron in proportion 1:2 in water

2. With solution of chloride iron in proportion 1:1 in water

3. With solution of hythio salt of ammonia in proportion 4:10 in water in temperature 40 I C

4. With solution hydrochloric acid (2 parts) peroxide of hydrogen (perintrol 1 part) and water (4 parts)

Attention:  the solution emit dangerous steams for the eyes but also for the breathing. For this reason the etching it is essential to become in open space (courtyard etc.) and never in underground or in space without good ventilation. Sure even if slow method is second. It presents the disadvantage however that where it falls this solution soils and does not leave with nothing or rather up to recently did not clean with nothing because henceforth exists in the market her dust company  Bungard that will save your beloved shirt from his transformation in duster. Independent from this it is good you wear the old clothes and you avoid is poured the solution in the floor or in your skin. All the above materials you can him find in any shop of chemical products. Certain perhaps him you find also in shops electronic. 

THE DRILLING

It specifically becomes with drills that accept small drills 0, 5  -  3 mms.  In the practice are used drills  0,8  mms for the  IC completed and drivers of elements, drills 1 mm for pins big elements, 1,2 -1,3 for  pins, 1,5 for relay, switches etc and 3 mms for holes of support pcb. For better results, you can use special base of support in order to centered better the apertures. Also you can use special power supply that has the possibility of regulation turn drill but also his her force.

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