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Author: Thomas Riegler and Burkhard Kainka ISBN 978-3-645-10062-5 Produced on the order of Conrad Electronic SE, Klaus-Conrad-Straße 1, D92240 Hirschau/Germany. All rights reserved, including the rights of photo-mechanical reproduction and storage in electronic media. Generation and distribution of copies on paper, data carriers or online, in particular as PDF, is only permissible with the express consent of the publisher;...
Table of Contents Introduction Components Battery Resistors Ceramics Capacitator Electrolyte Capacitator Transistor Diode Integrated Circuit (IC) Soldering Basics What is Soldering? The Soldering Iron Soldering Equipment Too Hot and too Cold Solder Points The Right Tools Before Starting Soldering Soldering Tinning Stranded Wire Soldering Together Wires Preparing Components...
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4.13 Soldering Components Close Together 37 4.14 Soldering Sensitive Components 39 4.15 Removing Short Circuits Caused in Soldering 40 4.16 Completing Transistor Circuit 42 4.17 Checking Circuit and Shortening Excessive Lengths 43 4.18 De-soldering Components with Several Legs 44 4.19 The Masterpiece 46 4.20 Other Circuits 47...
1 Introduction Specialist trade offers innumerable electronics circuit construction kits that you can solder together yourself. If you want to work with them, you should know how to handle a sol- dering iron. This learning package helps discovering the secrets of soldering step by step. In a series of subsequent exercises, you will learn how to solder various components and how to de- velop and build complete circuits.
2 Components 2.1 Battery The battery must be connected to any circuit in the correct polarity. The required battery clip has a red (plus) and black (minus) connection wire each. Both wires must be sol- dered on according to the required polarity. Figure 1: Battery circuit symbol 2.2 Resistors Resistors are some of the simplest electronic components.
Figure 3: Resistor Figure 4: Resistor circuit symbol 2.3 Ceramics Capacitator The capacitator is another important electronics component. It is available in two ver- sions. The simpler version is the small, round and flat ceramics capacitator. It is secured against polarity reversal. Capacities are indicated in Farad (F). The ceramics capacitator is labelled in a number code.
Figure 7: Electrolyte capacitator circuit symbol Figure 8: The electrolyte capacitator must be installed in the correct polarity. 2.5 LED Always observe polarity when installing a light diode. The LED has two connection wires of different lengths. The longer one is the plus pole. It is called anode (A). The minus pole, the cathode (K), has the shorter wire.
Figure 9: An LED must be installed in the correct polarity. Figure 10: LED circuit symbol 2.6 Transistor The transistor amplifies small currents. Its connections are called emitter (E), basis (B) and collector (C). The cylindrical casing is flattened on one side. The type designation is printed on here.
Figure 12: NPN transistor circuit symbol 2.7 Diode A diode lets current through in one direction only and blocks it in the counter-direction. It can be imagined like a check valve from a water installation. Conventional diodes are cylindrical like resistors. Their minus pole (cathode) is marked with a dash.
Figure 14: MD diodes are very small. 2.8 Integrated Circuit (IC) The learning package contains an IC type LM358 in SMD build. The installation direction must be observed when soldering on the IC. Polarity reversal must be avoided. It may de- stroy the component.
3 Soldering Basics 3.1 What is Soldering? In electrical engineering, soldering is one of the basic ways of establishing connections. Soldering creates an electrically conductive connection that cannot be disconnected. Using a melted metal binding agent (solder), soldering connects two metal work-pieces - e.g.
Universal soldering iron Universal soldering irons are slightly larger. Their power consumption is between 20 and 40 W. They are particularly suitable for hobby and craft use. They can also be used well for electronics soldering. They are also the first choice if you want to assemble simple to medium electronics kits.
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An electronics pliers set to bend components in shape and shorten excess lengths of con- nection wires is also recommended. Pincers can be helpful for small SMD components, as can a magnifying glass. Figure 17: 15-W fine soldering iron by Conrad Electronic (order no: 588539-62); this makes electronics soldering easiest.
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Figure 18: Stable soldering iron stand with solder sponge for cleaning contaminated soldering tips Figure 19: The fine mechanics’ clamp can be used to hold and comfortably solder PCBs. Figure 20: Soldering aids with magnifying glasses also hold the PCB.
Figure 21: De-soldering pump (order no.: 588502-62) to remove excessive solder 3.4 Too Hot and too Cold Solder Points Perfect soldering can be recognised by its nice gloss. A cold soldering point looks some- what matte and often has a lumpy surface. Defective solder points can also be recognised if the small solder cone around the component connection is missing or hardly there.
Soldering is best done with suitable equipment. We recommend the 15-W solder iron starter set available from Conrad Electronic (order: no.: 588292-62). In addition to a 15-W soldering iron, it comprises two soldering tips, solder, a deposit stand and a de-soldering pump.
Figure 23: Starter solder sets (Order no.: 588292-62) contain everything one needs to learn how to solder. 3.6 Before Starting Soldering Proper soldering is only possible if you keep the soldering tip clean at all times. Regularly wipe it off with a moist sponge. This removes excess solder from the soldering tip. Figure 24: Over time, solder collects at the soldering tip, which makes soldering considerably more difficult.
4 Soldering 4.1 Tinning Stranded Wire Fine-stranded wires are hard to solder because their strands go in all directions when sol- dering. The battery clip wire ends show how perfectly tinned wires should look. Cut off the tinned parts and strip about 5 mm of the wires. Then twist the strands evenly be- tween your fingers.
4.2 Soldering Together Wires For both wires to keep their position during soldering and you to have both hands free to work, clamp them into an electronics clamp and put them in position. Then use the sol- dering tip to heat both wire ends evenly. Now add the solder by moving it to the heated solder point.
Practice first by bending wire pieces with a few millimetres stripped of insulation on ei- ther end. Figure 29: The wire bent to shape with an electrician’s round pliers. Figure 30: For electrical components, the wires should not be bent right at the casing end. 4.4 Soldering Wire Bridges to Strip Grid There are two types of universal PCBs for constructing self-developed circuits, already ap- plied with the copper layer required for soldering.
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The lateral strip grid made up of 19 fields is well suitable for first exercises. You can solder on wire bridges and later components just by placing connection wires on the top half of the contact areas. Place the PCB and the wire bridge on the work surface. Strip a wire bridge end and align it with one of the contact surfaces.
Figure 31: Soldering wire bridges to the lateral strip grid 4.5 Soldering Wire Bridges to a Point Grid If you solder wire bridges to a point grid, push the wire ends to be soldered together through the bores of the hole grid part of the test PCB. Observe that there is only a small metal ring around each bore.
Figure 32: Soldering iron and solder must be moved precisely onto the land. Soldering should only take a few seconds. 4.6 Soldering Wire Bridges to a Point Grid - Version 2 The PCBs included in the learning package are coated on one side, like in most soldering kits.
Figure 33: To prevent the components pushed through from below from falling out during soldering, bend the connection wires slightly to the side. Figure 34: The PCB is turned around for soldering. 4.7 De-soldering Lateral Wire Bridges De-soldering must be practised. Again, the soldering iron must be heated to operating temperature.
When de-soldering, make sure not to touch any adjacent solder points or components with the hot soldering iron. Keep the de-soldering process short. The wire end should be de-soldered within 5 seconds. Figure 35: Pull slightly on the wire with your fingers while heating the soldering area, until the wire comes loose.
Figure 36: Pull slightly on the wire during heating in this version as well. 4.9 Simple LED Circuit: Preparations For your first circuit, your circuit plan only requires soldering on the battery clip, a resistor and a diode. In spite of the circuit being simple, the first question is how to transfer it to the PCB.
Figure 37: Simple LED circuit diagram Figure 38: Transfer the circuit diagram to a small sketch to see where and how to solder on the individual components. 4.10 Simple LED Circuit Use the soldering sketch from before to start soldering. Start with the resistor. It is a re- silient component and can be handled like a wire bridge.
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ode to one of the adjacent strips. When soldering, observe that the lower bores of the strip grid segments remain free. Push the red plus line of the battery clip through the bore of the strip to which the left resistor connection is soldered. Push the black minus wire into the free bore of the segment to which the LED cathode is soldered.
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Figure 40: Push the wires of the battery clips through the still-free bores at the two outer contact surfaces and solder them on. Figure 41: Last, solder the connection between resistor and LED with lots of solder.
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During your first de-soldering exercises, you will have noticed that some residual solder re- mains at the solder point after de-soldering of a component or wire bridge. Is usually collects in the bore, so that no connection wires can be pushed through anymore. This is where the de-soldering pump comes in.
Figure 43: After using the de-solder pump once, the solder bridge is removed. 4.11 Soldering SMD Diode SMD means „surface mounted device“. SMD components usually have no wire connec- tions but are soldered right to the PCB. they are also very small. The SMD diode 1N4148 included in the soldering course is only 3 mm long, including lateral connections.
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Place the SMD diode on the installation area with pincers and continue to hold it while fixating it with a soldering iron. For this, heat the diode at the side with the pre-tinned pad for a second. Now the SMD diode is soldered on on one side. Last, solder the second diode end as already known.
Figure 46: Keep the SMD diode in place with pincers while heating the pre-tinned pad and the diode con- nection resting on it. Figure 47: Last, solder on the second end by adding a little solder. 4.12 Soldering SMD Operational Amplifier SMD-ICs like the operational amplifier LM358 are soldered similarly to small SMD diodes.
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pincers so that its connections are located precisely on the contact surfaces. Keeping the IC in position with the pincers, heat the connection on the pre-tinned pad. Now the SMD- IC is attached. Solder on the other connections in sequence by placing the soldering tip precisely and adding a little solder.
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Figure 49: Pre-tin a pad first. Figure 50: Every connection must be soldered on individually.
4.13 Soldering Components Close Together This exercise starts the step-by-step construction of a transistor circuit. If you install all components in the last required position from the first, you will reach a completed circuit step by step. Sometimes, individual components must be soldered close together or their connections require soldering them in directly adjacent bores or lands.
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Figure 52: Working form the centre to the edge makes it easy to solder in components close together. Figure 53: Keep a calm hand to solder on higher components (like this LED) to directly adjacent lands.
4.14 Soldering Sensitive Components Transistors and ICs are sensitive components that must not be heated for long. They would be destroyed by it. Soldering must be performed quickly and precisely for this. The faster you can solder a pin on sensitive components, the less thermal load is placed on them.
4.15 Removing Short Circuits Caused in Soldering When soldering points and components, conductor paths, etc. are close together, it is pos- sible that a conductive connection is created by the solder during soldering. The circuit is not destroyed by this. You can still repair the circuit by removing the excess solder. The easiest way of removing it depends on amount and position.
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Figure 57: Solder lumps can be removed by heating them and applying the de-soldering pump. Figure 58: Here, solder short-circuits two strip grids. There is only little solder. It can be removed with the soldering iron.
Figure 59: The last residue can be scratched off with a small electronics screwdriver or a needle. 4.16 Completing Transistor Circuit After soldering the resistors, LEDs and the transistor to the PCB, all you need now is the battery clip, some wire bridges and a switch. Form the latter from two wire pieces that are only soldered onto the circuit at one end.
Figure 60: The finished circuit 4.17 Checking Circuit and Shortening Excessive Lengths Before taking the circuit into operation, check by way of visual inspection that all compo- nents are correctly installed and that no solder points were forgotten. Now shorten the ex- cess lengths of the component connection wires with an electronics wire cutter.
Figure 61: Excess connection wire lengths must be cut off after completing and inspecting the circuit. Figure 62: The cut connections should protrude over the PCB by 0.5 to 1 mm. Figure 63: Cut off the connection wires closely to the solder cones. 4.18 De-soldering Components with Several Legs Simple components like wire bridges or resistors can be de-soldered easily.
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First, heat one of the solder points for the three transistor connections, and keep the de- soldering pump ready at the work-site. Once the solder has liquefied, trigger the pump to remove part of the solder. Repeat this process until the bore is solder-free. Then take on the other two connections.
Figure 66: The de-soldering pump removes the solder completely from all three solder points in several goes. 4.19 The Masterpiece Build your own light-sensitive circuit according to the following circuit diagram. This cir- cuit will let you practice everything you learned in this soldering course. This includes transferring the circuit to the PCB, installing LEDs, transistor, SMD-IC and SMD diode cor- rectly and soldering correctly.
4.20 Other Circuits The components in the soldering learning package permit soldering a great number of other circuits as well, such as most circuits of the Conrad-Electronic advent calendars from the years of 2008, 2009 and 2010. You can download the circuit templates from http://www.elo-web.de/ergaenzungen .
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