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Working instruction for photopositive boards

Working instruction for photopositive boards

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  PRINTED CIRCUIT BOARD

Working instruction for photopositive boards

 

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1. Cut the photopositive board to the desired size. Remove the light protection foil from the board in a weakly illuminated (darkened) room. 

 

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2. Put the photoboard with the light-sensitive, lacquered side upward onto a frm padding for exposition. Place the flm (layout) above it. On this flm all strip conductors are black and impervious to light and all gaps are transparent. A glass plate is placed over the flm to ensure that the flm leans plainly on and may not get out of place. Subsequently expose the flm with a powerful lamp (1000 W halogen lamp, tanning lamp or UV-lamp) for approx. 3 – 10 minutes in a darkened room. The weaker the light source, the longer will be the exposure time. The distance of the lamp should be at least 30 cm. You have to fnd out the most favourable exposure times by experiments. They depend to a large extent on the applied lamps. 

 

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3. After exposition, the board has to be developed. For this purpose, dissolve the developer in 1 l of water acc. to the working instruction. Immerse the board into this developer. After a short time, the lacquered parts which were not covered black will separate. If necessary, the board may be moved slightly during this process. As soon as only the strip conductors remain standing, remove the board from the developing bath and rinse well under running water. 

It is very important to wear safety glasses and rubber gloves during this work and to use our attached plastic forceps. 

 

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4. Dissolve the corrosive in approx. 0,5 l of warm water (50°C to 60°C) acc. to the instruction. In a warm condition the corrosive develops the highest causti- city. Fill the enclosed working bowl to the half with the warm etchant and place the board into this solution with the strip conductors upward. Now the bowl has to be moved slightly and continuously in order to engrave the board quickly. Af- ter the board is engraved (only the strip conductors remain on the board), rinse the board thoroughly under running water. After drying the board with a cloth, it can be drilled and equipped. 

It is absolutely necessary to wear rubber gloves and safety glasses while handling the corrosive and to use the enclosed plastic forceps. 

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