 Welcome, myself, Mr. Giridhar Jain, Assistant Professor in Electronics and Telecommunication Engineering Department, Walchin Institute of Technology, Singapore. Now today, I am going to explain Printed Circuit Boards' fabrication process, means how to build a Printed Circuit Board. Learning outcomes of this session are, at the end of this session, students will be able to explain PCB fabrication steps. So first, for starting the PCB fabrication, the first requirement is PCB artwork, positive or negative film depending on whether screen printing or photo printing technology is being used. Second step, cut the copper clad to the PCB size by shearing machine or a hacksaw. Copper clad is selected of either paper phenolic or glass epoxy depending on the application. So this table shows the comparison between the paper phenolic and glass epoxy. So here, three properties are compared, so mechanical strength. Mechanical strength of glass epoxy is higher than the paper phenolic, cost. Cost is higher glass epoxy than the paper phenolic and applications. So paper phenolic is used for consumer electronics applications and the glass epoxy is used for industrial applications. Now next step, after the PCB is copper clad is cut to the size of PCB by using hacksaw or a shearing machine. Then next step is clean the copper clad by the scrubber or by using the lime and salt to clean the PCB. For industrial applications, the 5% hydrochloride acid HCl is used for cleaning the copper clad. Now second step is printing of the artwork on the copper clad. Next is itching and cleaning of the PCB and next drilling. Now this figure shows a positive film of the artwork. Positive film means here whatever you see that is a black, black color that copper remains on the PCB and other copper is removed in the itching process. So it is a original size image of the PCB artwork from solder side. Now this figure shows the negative film of the solder side artwork. In a negative film what is done the image of earlier image that is this image is inverted in color. So here whatever is the white. So that portion the copper remains and the for black portion the copper is removed. Now this positive film and negative film they are used depending on the technologies used for manufacturing of the PCB. Now when screen printing is used, this positive film is used and when photo printing is used this negative film is used for preparing the PCB. Now next is printing of the artwork on the copper clad. So printing of the artwork on copper clad involve the printing of the acid resistant image of the artwork on the PCB that is copper clad. Means whatever image is printed on a copper clad that image is resistant to the itching chemicals. Now pause this video and think on following question. How to print acid resistant image on the copper clad? So for printing acid resistant image on a copper clad there are basically two techniques. First is screen printing and second is photo printing. Now in first technique screen printing. Now screen printing is a technique which is same which is used for printing the visiting cards, invitation cards same technique is used. So instead of that paper cards they are printed on a copper clad and for printing a positive film is used, positive film of the artwork and the material used that is ink used for printing the PCB is a PCB ink which is specially designed for screen printing of the PCBs. Now second method is a photo printing. So in case of photo printing the material used is a photoregist. Now this photoregist is a material when it is exposed to the ultraviolet rays its properties are changed and the unexposed portion there is no reaction means when light falls on the photoregist that part gets affected there is a chemical reaction, photochemical reaction. Means photoregist material with a UV exposing machine is used in photo printing and as far as film is concerned a negative film of artwork is used for preparing PCB by using this photo printing techniques. Now this technique is suitable for the printing with high accuracy and it is costly as compared to the screen printing. Now next step in the PCB fabrication is etching means once the acid resistant image is printed on a copper clad either by using screen printing or a photo printing next is etching. Etching process involves removing of the unwanted copper from copper clad by using etching chemicals. Now etching chemicals generally used here is ferric chloride acid used ferric chloride acid for etching of the printed circuit boards means PCB to be etched are immersed in a fucl 3 solution. The etching time depends on the concentration of this fucl 3 acid and the temperature of acid for etching for less number of PCBs a plastic tray is being used and for large number of PCBs the etching machine is used in the industry in which the spray of etchant is sprayed on to PCB and the PCBs are moving over a conveyor belt. Now next step in the PCB fabrication is cleaning means once the PCBs are etched means unwanted copper is removed the etched PCBs are cleaned by flushing water over it. Now next allow PCBs to dry for some time after PCBs are dried then remove acid resistant layer of the printed image from PCB by using thinner and then allow the PCBs to dry. In this way the PCBs are etched and they are printed on the copper clad. Now next is inspection inspect the PCBs for any errors that is open circuit of the copper conducting tracks means some of the tracks may be open circuit during the etching or some of the adjacent tracks there will be the short circuit. So if there are such kind of open circuit and short circuit errors correct these errors if any. Now for correcting the errors next is drilling. Now PCBs are drilled by using a drill machine with a spindle speed of 20000 rpm. So this is a minimum speed required for drilling of the PCBs. Now PCBs can be drilled by such drill machines by visual inspection. Now while drilling the diameter of holes drill on the PCB is not uniform for all the holes but it depends on the component means while drilling the printed circuit boards the holes are holes are drilled by referring the component layout the drill bits which are used for drilling the printed circuit boards are different for paper phenolic and glass epoxy for paper phenolic HSS which stands for high speed steel drill bits are used and for the glass epoxy tungsten carbide drill bits are used. Now this figure shows a component layout. Now while drilling the PCB if we look at the component layout you can see this is 40 pin IC so all holes of these are all holes of the pins of this IC are drilled with 0.7 mm drill bit this is a connector this is connector. So for these connectors drill the hole with a diameter of 1 mm for regulator IC 1 mm for the preset 1.2 mm these are the switches 1.4 mm means in this way depending on the component the hole size are different and by referring by looking at the component layout the drills holes are drilled as per the requirement of the hole size from the component layout. These are references printed circuit board design and technology by Bouchard Tata Migrail publisher and circuit maker PCB design software. Thank you for watching this video.