Students were divided in three groups after the seminar and they visited the various manufacturing units and R&D labs of PCB designing. Mr. Indra Singh Bohra (Training Head, Nano Electrotech Pvt. Ltd.) described in brief about the manufacturing process of a PCB including drilling, conductor plating, solder resist, testing and assembling. He explained that in PCB drilling, the components that have to be attached to the multi - layered PCB can be prepared only by VIAS drilling in which a pated - through hole is drilled in the shape of annular rings. Small drill bits that are made out of tungsten carbide are used for the drilling. A dremel drill press is normally used to punch the holes and for high volume production automated drilling machines are used. After that he defined the conductor plating process which is the outer layer of the PCB containing copper connections which do not allow solderability of the components. To make it solderable, the surface of the material has to be plated with gold, tin, or nickel. The next process he defined is solder resist which covers the other areas which are not to be solderable with a solder resist material. It is basically a polymer coating that prevents the solder from bringing traces and possibly creating shortcuts to nearby component leads. In industrial applications the next phase is testing in which PCB’s are tested by different methods such as Bed of Nails Test, Rigid Needle adaptor, CT scanning test, etc. The basic of all tests include a computer program which will instruct the electrical test unit to apply a small voltage to each contact point, and verify that a certain voltage appears at the appropriate contact points. The last step of PCB manufacturing is PCB assembling that includes the assembling of the electronic components on to the respective holes in the PCB. This can be done by through-hole construction or surfac - mount construction. |
