Ferric Chloride Case Study

3.19.5 PROCEDURE: To etch 1 kg of copper, 5.1 kg of Ferric Chloride is consumed. In order to increase the copper dissolving capacity and to bring the etching time slightly down, often HCL is added. HCL acts simultaneously against excessive sludge formation. After etching is over the Ferric Chloride contained surface should be first cleaned by spraying water, which is not enough. Then we dip it in a 5% (by volume) in the solution of oxalic acid to remove iron and copper salt sand final water rinsed vigorously. Then we rinse it by using petrol so that the paint comes out and copper remains intact where the paint was applied. The copper acts as conduction path for flow of signals. The high corrosive nature of Ferric chloride leads to short etching time and avoid under etching.

3.19.6 CHEMISTRY: Due

In case of semiconductor devices like transistors and diodes, thelength of the leads extending above the component side of the PCB should be about 1 cm. if transistor leads are too short we use a base. Metal cap should touch if they are not at ground potential. The right terminals should be at right places.

5. Certain components like transformers, potentiometers and variablecapacitors, which are meant for use with PCB, are provided with pin type terminals that can be simply inserted into the hole in the PCB and soldered.

6. Use IC base for IC.

3.19.9 SOLDERING: PCB soldering required proper soldering technique, as explained below such as follows;

1. A light duty soldering iron of 25W or 30 W rating should be used to prevent damage to the printed circuit wiring due to excessive heating. The tip of soldering iron should not have an oxide coating. Clean it using sand paper.

2. Do not use excess solder to avoid solder flouring to adjacentconducing paths forming bridges, which cause short circuits.

3. Clean the surface of traces before you start soldering. It is advisable to use