3Learning objectives: - Bigger picture: -Know about engineering processes used to produce modern engineered productsLearning objectives: -Be able to explain what is meant by the term fabricationDescribe a range of different fabrication processes used within engineeringBe able to explain the manufacture of PCB and surface mount technologySuccess criteria: -Provide a description of different fabrication techniquesCorrectly identify different fabrication techniquesCorrectly describe the manufacturing process of PCBLiteracy key words: PCB etching, surface mount technology
5Divide the various joining techniques into permanent and non permanent RivetsAdhesiveSolderBoltScrewsThreadsWeldingNailsPressed jointsPermanentNon permanent
6Divide the various joining techniques into permanent and non permanent RivetsThreadsBoltSolderAdhesiveNailsScrewsWeldingPressed joints
7Fabrication processes: Engineered products/parts need to be joined up in some way. Sometimes the solution is as simple as a nut, bolt and washer, but on other occasions a more permanent method is required.Assembling is done by welding, binding with adhesives, riveting and threaded fasteners
8Welding . . .One of the most efficient methods of permanently joining two pieces of metal together.It can be done in many different ways but most methods use intense heat to fuse the metal together.A number of energy sources – a gas or electric, laser or ultra sound – can be used.
9Homework – due 4th February 2014 Welding processDescriptionAdvantagesMIG welding common industrial welding process. It uses electricity to generate the heat required to weld materials.MIG stands for metal inert gas. Suitable for large scale production Varying thickness of materials can be joined Reduced cost due to no further cleaning requiredOxy-acetylene A gas welding process where a flame is produced using a mixture of oxygen and acetylene.No pressure on the product is required – the heat is there to control the welding of parts. Ease of controlling the low and high temperatures needed for welding, brazing and soldering Relatively inexpensive in comparison with other welding processes and commonly found in school workshops Spot welding A type of electrical resistance welding generally used to join sheet material together. The basic principle uses a transformer with a primary winding and a secondary winding connected to copper electrodes..When the two electrodes trap the sheet material they generate enough heat to fuse the two together. The process is free from fumes or spatter Requires little or no maintenance Cost effective
10Surface mountSurface-mount technology (SMT) is a method for producing electronic circuits in which the components are mounted or placed directly onto the surface of printed circuit boards (PCBs). An electronic device so made is called a surface-mount device (SMD).In the industry it has largely replaced the through-hole technology construction method of fitting components with wire leads into holes in the circuit board. Both technologies can be used on the same board for components not suited to surface mounting such as large transformers and heat-sinked power semiconductors.
11Printed circuit boardElectronic circuits in schools and industry are normally manufactured through the use of PCBs (Printed Circuit Boards). The boards are made from glass reinforced plastic with copper tracks in the place of wiresComponents are fixed in position by drilling holes through the board, locating the components and then soldering them in place. The copper tracks link the components together forming a circuit.
12Process of manufacturing a PCB and SMT Printed circuit board (PCB) manufactureThe Surface Mount Technology (SMT) process184.108.40.206.220.127.116.11.5.5.6.
13Process of manufacturing a PCB and SMT Printed circuit board (PCB) manufactureThe Surface Mount Technology (SMT) processComponents are soldered to the surface of the boardProducing the artworkThe finished board is then inspected for imperfectionsDesigning the layoutConveyor belts are used to transport the boards to the reflow soldering ovenPCB etchingPopulating the board and solderingThe board is heated to a temperature that melts the solder plateDrilling the boardPlace components using pick and place robotApply solder paste to copper pads