PCB exposure, development and etching

You will see pcb presenting itself front in your eyes if you are careful at certain fundamental points of this article. The tools and the materials that you will need for this work appear in the two first photographs and they are:

· UV exposure chamber

· Photosensitive pcb

· Caustic Soda

· Trichlorure iron in solid form

· 3 deep plastic basins in order to it is not soiled the space where you work

· Plastic pence

· Plastic gloves

· Ready films of printed circuits that you want to manufacture

Preparation - Precautions

Turn on the UV box lamps because need roughly 5 thinly in order to they reach in their biggest brightness. Thus you do not use UV box front pass 5 thinly since they turn on lamps. Be not extinguished lamps afterwards the appearance pcb if you are to present above, because lamps steams of mercury it should freeze in order to they turn on again. Extinguish since you have finished all the process of report.

In one of the three basins you dissolve the content of file of caustic soda in one liter of water. If you have caustic soda in bulk you dissolve 10 - 20 grams in one liter of water. Leave the soda to be dissolved well because it does not make to remain small pieces of caustic soda in the solution because they are capable to spoil pcb. The caustic soda that you did not use you look after in plastic or glass container and no metal, because the caustic soda is water absorber thing that means that it draws the water vapors of atmosphere, it melts whenever it becomes useless and dangerous after if it falls in the skin it causes burn. When you handle pcb in in the solution is essential the use of plastic gloves or the use of plastic pincer in order to it is touched pcb, and never with naked hands.

In the second basin marsh clean water in order to it is washed pcb by the residues of appearance. In the third basin empty the content of sachet with trichlorure iron in one liter water, or differently use in proportion 1:2 with water. Afterwards the etching you can use the solution sometimes still, for this you look after well closed in plastic or glass container and you are careful it does not come in contact with any metal because him it will melt. The trichlorure iron does not burn the skin but is very distinctive and it causes oxidation of metals with which it comes in contact. Also where it falls it leaves a yellow blot which does not come out with no detergent, for this attends you wear the old clothes when you work with this. The unique way to clean a such stain is to find the product of German company Bungard which is in form of dust and is dissolved in two parts water and with this solution is cleaned the stain.

After you have prepared the three basins with the liquids, you can advance in the process of appearance.

The report

Take two pieces of glass of thickness of 5 mms in such size so that fits in your booth of report. Front you make anything you extinguish lights and you leave little light equally - equally in order to you can it is worked. If it is day you attend does not enter very natural light from the windows. PCB is sensitive in UV but is also offended by the possible light. Take the photosensitive pcb that is seen in photograph 3. Is pcb that is covered with the blue protective paper. If you do not use photosensitive pcb because they are precise, you can spray one simple pcb after him you clean with sponge, with photosensitive spray (as Positive 20 or PRP 200 ), dry it well with a heat gun for 15 minutes or leave it dry alone her in a dark box for 24 hours. After you have already in your hands photosensitive pcb (if they are from ready the trade you remove the protective cover) you lean with the opposite side from that of copper above in a pane. Place carefully the film that can be also chine above in the photosensitive surface. Attention needs in this point is not placed backwards the film and it is presented so as to it cannot be used later. For this reason you can put certain letters so that you know which side is the right.

Then you place from above the other piece of pane so that they come in absolute contact. With the help scotch tape you stick the two panes so that they are tight tied up between them and they are not shaken. All these should become in conditions of low lighting and as long as more fast it becomes so that it does not anticipate pcb it takes light and spoils. Place in in the space of report and with a chronometer you measure 5-7 minutes (depending on the intensity of light, the pcb or thickness of spraying). If you use rise paper then you extend the time of report at 3-5 thinly in order to it anticipates it is lilted up well artwork your.

If you make this process for first time you we consult to cut small small pieces pcb and experiment with various years of report so that you achieve the perfect result.

The development

After you finish with the appearance you look after in dark box until you finish with remainder. If you only have one of closed lamp booth of report and throw pcb in in the solution with the caustic soda. Attention does not come the solution in contact with the skin because him it burns and afterwards will sting. Better it is you touch pcb with plastic gloves or with plastic pincer. If all are include in 15 -20 seconds you will slowly see - slowly front in your eyes it is presented pcb. You saw how much easy it was? If passes one thin and has not been presented pcb most likely to be they happen the following:

· The quantity of caustic soda was small. It is removed pcb and throws in in the basin with clean water. Add still few caustic soda and after it is dissolved well you throw again in pcb. It will be supposed maximum in half thin it has been presented. And in this point it is judged essential experiment with the small small pieces pcb that you have in advance in order to you find the suitable combination of time of report and quantity of caustic soda.

· The water was a lot of cold. The suitable temperature 20-30 C

· The report in the light was very small. In this case unfortunately you failed. Try again with other pcb and bigger time of report. Do not despair in any case, it wants patience and does not forget each beginning and difficult.

· You used photosensitive pcb old or the thickness of spraying he was not uniform.

After it is presented pcb you in touch her with the plastic pincer or with the gloves and marsh in clean water to be rinsed. Then you sweep with a cotton cloth light (no synthetic because it engraves and will have problems) and observe her surface. It will be supposed she is impressed embossed artwork and you distinguish clearly. The points that were lilted up will be supposed to have the color of copper.

The etching

Now you can open all lights and windows and because it is not to suffer nothing pcb but also because you need very good ventilation. Throw pcb in in the second basin with Trichlorure iron. After certain thinly you remove pcb with plastic pence and you will see that in utmost from the points that have been lilted up the copper has begun to be eaten. Will be supposed the drawing it is clean and the lines they are of course separated and does not exist point that while it appears the copper exists points that do not melt. If it happens such something means that or the time of report was not enough, or the appearance did not become rightly or was not sprayed uniformly pcb. If all went well in 20 - 30 thinly pcb your she will be ready.

The final washing

Wash meticulously pcb with clean water and you leave dry, meanwhile it is gathered your tools. If it needs it is flown the Trichlorure solution will be supposed rarefaction very - a lot with water because it exists danger it destroys the metal piping of your house or even all the block of flats.

The piercing

You will need drill, drills 0,8 until 1,5 mms for the various elements and for better and more relaxant work a base as that of photograph. With use of base you will have better results and more professional work. Then you clean pcb with acetone in order to leave the residues of photosensitive covering. Then with little wire of cooker (as what we clean the saucepans) you rub in order to burnishing. Sweep with clean cloth or paper of cooker and if you want you spray with special spray for protection by the oxidation and for facility in him you stick. Now pcb she is ready in order to you stick her elements.