PCB fabrication.pptx

Pcb fabrication and types of fabrication and it's advantages. Application of pcb fabrication.It plays important role in electronics industry

1. Printed Circuit Board (PCB) A  printed circuit board  ( PCB ) is a laminated sandwich structure of conductive and insulating layers. PCBs have two complementary functions . To affix electronic components in designated locations on the outer layers by means of soldering. To provide reliable electrical connections (and also reliable open circuits) between the component's terminals in a controlled manner often referred to as PCB design.  PCBs mechanically support electronic components using conductive pads in the shape designed to accept the component's terminals, and also electrically connect them using traces, planes and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. Through-hole technology Surface-mount technology

2. Surface mount PCBs assembly occurs when electrical components (surface-mount devices)  are machine picked and mounted directly onto the surface of the PCB . During this process, thousands of electrical components are attached and connected to their contact pads using reflow soldering. Through-hole technology , also spelled “thru-hole”, refers to the mounting scheme used for electronic components that involves the use of leads on the components that are inserted into holes drilled in PCBs and soldered to pads on the opposite side either by manual assembly (hand placement) or by the use of automated insertion mount machines.

3. Types of PCB fabrication Double-Sided PCBs Multilayer PCBs Rigid PCBs Flex PCBs Rigid-Flex PCBs Single sided PCBs

4. PCB FABRICATION PROCESS Designing of electronics circuits & layout Layout printing Preparing substrate ( A printed circuit board needs structure and shape. It also needs a platform or canvass to hold all of its other components .) Etching Drilling Solder mask application Component assembly PCB testing

5. DESIGNING OF CIRCUIT & LAYOUT Softwares for PCB designing:- Proteus Professional/Eagle PCB layout designing :- 1. Defining Trace Widths PCB layouts use traces to connect components, but how wide should these traces be? The required trace width for different nets depends on three possible factors: Manufacturability.  Traces cannot be too thin, otherwise they can't be reliably manufactured. Current.  The current carried in a trace will determine the minimum required width to prevent the trace from overheating. When the current is higher, the trace will need to be wider. For traces that don't need specific impedance or high current, a 10 mil trace width is fine for the vast majority of low current analog and digital signals. Printed circuit board traces that carry more than 0.3 A may need to be wider. To check this, you can use the  IPC-2152 nomograph  to determine your PCB trace width for a required current capacity and temperature rise limit. “1 mil = 1/1000 inch = 0.001 inch” 2. Make important nodes accessible. 3. Give space between components . 4. Place components with the same orientation. 5. Print the layout to see if components' sizes match. Exchange wiring directions between layers . Do not mount the electronic components within 1.27mm around the non-mounting holes, such as tooling hole and standard holes . Avoid placing holes under the components such as the horizontally mounted resistors, inductors, (electrolytic capacitors, etc., so as to avoid short-circuiting the vias and component.

6. ETCHING ETCHING is an intaglio printmaking process in which lines or areas are incised using acid into a metal plate in order to hold the ink. In etching, the plate can be made of iron, copper, or zinc . Chemical etching is usually done with ammonium per sulphate or ferric chloride. Process for using PCB etching machine: Prepare Ferric Chloride Solution in the ratio of 1 KG Solid Ferric Chloride in 2 liters of water. Put the solution in tank till the level touches 70% of the tank capacity. Make sure the heater and temperature sensor tube is dipped in solution. Set temperature to 50-55°C and after the solution is heated up to this temperature, dip the PCB hanged in the hanger provided with the machine for 4-5 minutes. Keep on inspecting the PCB after every 2 mins to avoid over etching.

7. DRILLING PCB drilling, or  printed circuit board  drilling, is the process of creating holes, slots, and other cavities into an electronic circuit board before soldering/mounting components onto it. It is typically done by using a PCB drill bit (an automated machine) that is slightly smaller than the components placed on it. Single-sided or double-sided PCB  will be drilled directly after getting on the production line . Multi-layer board will be drilled after pressuring layers. By classification of the function, different drilling holes can be divided : through the hole, blind hole, Buried hole, etc.

8. SOLDER MASKING, COMPONENT ASSEMBLY, PCB TESTING A Solder mask is   a protective coating over PCBs that prevents oxidation and electrical shorts . The solder mask is coated over the entire board apart from the solder pads. The traditional green color coating that you see on the PCBs is the solder mask. Uses Resin to coat the PCB to protect it from damage. Soldering all components on right place leads to component assembly. And the resultant PCB is called as Assembled PCB. Final step in fabrication is – PCB Testing- which verifies the working of complete circuitry. Can be done by manual , automated optical inspection , flying probe, x-ray inspection, etc methods.