Wave Soldering Machine

The purpose of flux is to facilitate the soldering process. One of the obstacles to a successful solder joint is an impurity at the site of the joint, for example, dirt, oil or oxidation. The impurities can be removed by mechanical cleaning or by chemical means, but the elevated temperatures required to melt the filler metal (the solder) encourages the work piece (and the solder) to re-oxidize. This effect is accelerated as the soldering temperatures increase and can completely prevent the solder from joining to the workpiece. One of the earliest forms of flux was charcoal, which acts as a reducing agent and helps prevent oxidation during the soldering process. Some fluxes go beyond the simple prevention of oxidation and also provide some form of chemical cleaning (corrosion). For many years, the most common type of flux used in electronics (soft soldering) was rosin-based, using the rosin from selected pine trees. It was ideal in that it w...

Soldering  is a process in which two or more items (usually metal) are joined together by melting and putting a  filler metal  ( solder ) into the joint, the filler metal having a lower  melting point  than the adjoining metal. Soldering differs from  welding  in that soldering does not involve melting the work pieces. In  brazing , the filler metal melts at a higher temperature, but the work piece metal does not melt. In the past, nearly all solders contained  lead , but environmental and health concerns have increasingly dictated use of  lead-free alloys  for electronics and plumbing purposes. Origins Applications Solders 63/37: melts at 183 °C (361 °F) (eutectic: the only mixture that melts at a  point , instead of over a range) 60/40: melts between 183–190 °C (361–374 °F) 50/50: melts between 183–215 °C (361–419 °F) Soldering was historically used to make jewelry items, cooking...

Elements of vector calculus: divergence and curl; Gauss' and Stokes' theorems, Maxwell's equations: differential and integral forms. Wave equation, Poynting vector. Plane waves: propagation through various media; reflection and refraction; phase and group velocity; skin depth. Transmission lines: characteristic impedance; impedance transformation; Smith chart; impedance matching; pulse excitation. Waveguides: modes in rectangular waveguides; boundary conditions; cut-off frequencies; dispersion relations. Antennas: Dipole antennas; antenna arrays; radiation pattern; reciprocity theorem, antenna gain. Network analysis Electronic devices and circuits Signals and systems Control systems Network graphs: matrices associated with graphs; incidence, fundamental cut set and fundamental circuit matrices. Solution methods: nodal and mesh analysi...

Professional bodies of note for electrical engineers include the Institute of Electrical and Electronics Engineers (IEEE) and the Institution of Electrical Engineers (IEE) (now renamed the Institution of Engineering and Technology or IET). Members of the Institution of Engineering and Technology (MIET) are recognised professionally in Europe, as Electrical and computer (technology) engineers. The IEEE claims to produce 30 percent of the world's literature in electrical/electronic engineering, has over 430,000 members, and holds more than 450 IEEE sponsored or cosponsored conferences worldwide each year. SMIEEE is a recognised professional designation in the United States. Project engineering For most engineers not involved at the cutting edge of system design and development, technical work accounts for only a fraction of the work they do. A lot of time is also spent on tasks such as discussing proposals with clients, preparing bud...

Electronic devices : Energy bands in silicon, intrinsic and extrinsic silicon. Carrier transport in silicon: diffusion current, drift current, mobility, resistivity. Generation and recombination of carriers. p-n junction diode, Zener diode, tunnel diode, BJT, JFET, MOS capacitor, MOSFET, LED, p-i-n and avalanche photo diode, LASERs. Device technology: integrated circuit fabrication process, oxidation, diffusion, ion implantation, photolithography, n-tub, p-tub and twin-tub CMOS process. Analog circuits : Equivalent circuits (large and small-signal) of diodes, BJTs, JFETs, and MOSFETs. Simple diode circuits, clipping, clamping, rectifier. Biasing and bias stability of transistor and FET amplifiers. Amplifiers: single-and multi-stage, differential, operational, feedback and power. Analysis of amplifiers; frequency response of amplifiers. Simple op-amp circuits. Filters. Sinusoidal oscillators; criteri...

A stall occurs when the motor torque cannot overtake the load torque and the motor cannot rotate. When this happens, the motor will draw more current than the FLA to try to turn the load, again, defeating the purpose of the soft starter. Motor stalls are possible if the motor torque dips below the load torque; for a high inertia load, the starting load torque is quite high and stays relatively high. Fig. 26-27 show possible stall conditions (highlighted by arrows) for a soft start or a current limit start. Fig. 26-27 and 32 may be slightly misleading because once the motor stalls the speed will not increase. Soft Starter Settings Starting Type Soft Start Initial Torque % 40% Figure 26: Soft Start Stall  Soft Starter Settings Starting Type Current Limit Initial Current% 300% Figure 27: Current Limit Stall  Pump Application Load Characteristics of Poles 4 Motor Inertia 100 Pump Application Stall Conditions Conclusion other soft starters The pump application ...

An example of open loop control is the voltage ramp (Fig. 14), the voltage ramps from an initial voltage to full voltage in a linear fashion without regards to the load. Pump start is another form of open-loop control. The pump starter’s firing circuit ramps up the voltage with a profile that allows the speed/torque to ramp (Fig. 15) in a more efficient manner and helps protect against water hammering, a common problem in pump applications. Fig. 14-15 also show examples of soft stopping. Applications such as current limit (Fig. 16) use feedback from the motor or the line current/voltage to change the firing angle of the SCRs as necessary, hence closed-loop. All control schemes listed monitor back EMF of the motor as to not become unstable. Figure 14: Voltage Ramp  Figure 15: Pump Start  Figure 16: Current Limit  Applications Soft starters can be made for a reversing application by adding two extra SCR pairs that switch two phases. For example, line phase “b”...

Quality depends on proper temperatures when heating and on properly treated surfaces. Defect Possible causes Effects Cracks Mechanical Stress Loss of Conductivity Cavities Contaminated surface Lack of flux Insufficient preheating Reduction in strength Poor conductivity Wrong solder thickness Wrong solder temperature Wrong conveyor speed Susceptible to stress Too thin for current load Undesired bridging between paths Poor Conductor Contaminated solder Product Failures Solder types Effects of cooling rate Thermal profiling Different combinations of tin, lead and other metals are used to create solder. The combinations used depend on the desired properties. The most popular combinations are SAC (Tin(Sn)/Silver(Ag)/Copper(Cu)) alloys and Sn63Pb37 (Sn63A) which is 63% tin, 37% lead. The latter combination is strong, has a low melting range, and melts and sets quickly. Higher tin compositions give the solder higher corrosion resistances, but raise the melting po...

Wave soldering is a bulk soldering process used in the manufacture of printed circuit boards. The circuit board is passed over a pan of molten solder in which a pump produces an upwelling of solder that looks like a standing wave. As the circuit board makes contact with this wave, the components become soldered to the board. Wave soldering is used for both through-hole printed circuit assemblies, and surface mount. In the latter case, the components are glued onto the surface of a printed circuit board (PCB) by placement equipment, before being run through the molten solder wave. As through-hole components have been largely replaced by surface mount components, wave soldering has been supplanted by reflow soldering methods in many large-scale electronics applications. However, there is still significant wave soldering where surface-mount technology (SMT) is not suitable (e.g., large power devices and high pin count connectors), or where s...