ENGLISH PAPERS : The Types of Soldering

January 26, 2020



1.1  Background
            Soldered connections are used in aircraft electrical wiring to form a continuous and permanent metallic connection having a constant electrical value. The importance of establishing and maintaining a high standard of workmanship for soldering operations cannot be overemphasized.
            This section describes the materials and equipment used in soldering aircraft interconnecting wiring. It also describes and illustrates preparation and care of equipment, procedures to be followed, and the soldering techniques necessary to make a good soldered joint.
            In addition, special materials, equipment, and techniques used in soldering printed circuit assemblies are mentioned where they differ from those used in general electrical soldering. In the repair of printed circuit assemblies, soldering is closely associated with repairs to the insulating base and conductor pattern, and with replacement of components. These repairs are usually accomplished at the intermediate or depot level where other component or “black box” repairs are made. For detailed information on printed circuit repairs to a particular system, the handbook of maintenance instructions for the particular equipment involved should be consulted.
1.2  Purpose
1.      Know the meaning of soldering
2.      Know the types of solder
3.      Know the application of soldering



2.1 Definitions
            Soldering is the process of joining two or more metals together at a temperature lower than the melting points of the metals. In its molten state, solder chemically dissolves part of the metal surfaces to be joined. However, most metals exposed to the atmosphere acquire a thin film of tarnish or oxide; the longer the exposure the thicker the film will become. This film is present even though it is not visible, and solder alone cannot dissolve it. A soldering flux with a melting point lower than the solder must be used to “wet” the metal and allow the solder to penetrate it and remove the film. The flux melts first, removing the tarnish or metallic oxide, and also preventing further oxide from forming while the metal is being heated to soldering temperature. The solder then melts, floating the lighter flux and the impurities suspended in it to the outer surface and edges of the molten fillet. The solder cools and forms an alloy with the metal. Most of the flux is burned away during the soldering process; any residue is removed by appropriate cleaning methods.
            The soldering methods used for general aircraft wiring are essentially the same for both production soldering and repair work. For printed circuit assemblies, production methods and repair methods are different. In production, a dip soldering method is used, where several connections are made at the same time. Soldering repairs, however, are made individually, using techniques similar to those used for soldering general wiring - with special precautions to prevent thermal damage to the heat-sensitive, closely packed circuit elements
2.2 Types of Solder and Flux
            Soldering melts at temperatures below 450 ° C (840 ° F). Solder, which has always been used in general and is a tin-lead alloy with various portions. For example solder with 61.9% tin and 38.1% lead melting at 188 ° C, where tin melts at 232 ° C and lead at 327 ° C. For special applications and higher joint strength (especially at high temperatures), other solder compositions that can be used are tin-zinc, lead-silver, cadmium-silver, and zinc-aluminum alloys.
2.3 Typical Soldering Operations
a. Tinning - wires or cables preparatory to joint soldering and to fuse ends; contact pins and inside surfaces of solder cups; shielded wire braid, after twisting, to fuse, terminate, and connect.
b. Soldering - wires and cables, previously tinned, inserted into solder cups of terminals, or mechanically wrapped on shaped lugs and post or hooked terminals; twisted connections, or broken wire for emergency repair; printed circuit conductor pattern defects, or component leads and lugs to conductor pattern terminal areas.
c. De-soldering - soldered joints prior to re-making; printed circuit component connections to remove component for replacement.
2.4 Heat Application Methods
            Soldering Iron
                                The most commonly used method of' heat application for soldering joints in aircraft electrical wiring is by means of an electrically heated, hand held soldering iron. In addition to the conventional iron, a pencil iron is frequently used. Pencil irons, except for their smaller size, are identical to conventional irons and are used for precision soldering of small units and miniature assemblies.
                Resistance Soldering
            Resistance soldering is frequently used in large volume production where the operation is standardised. In this method, a low voltage transformer is used and the metal to be soldered is heated by the resistance to a flow of electric current. The work is gripped between two electrodes, completing the circuit and heating the metal for soldering. In another application, a carbon pencil is used as one electrode and the metal to be soldered forms the other electrode. When contact is established through the carbon pencil, intense heat is generated at the point of contact. Resistance soldering is well adapted to the soldering of small parts or for congested assemblies where it is desired to restrict heat to a small part of the assembly.
Torch Soldering
            Torch soldering is used where a high heat is required - as in silver soldering. This process is also suitable for soft-soldering large work which is not part of an assembly or when the part to be soldered can be removed for soldering. For example, wires may be torch soldered to large contacts that have been removed from MS connectors. Torch soldering is not suitable for soldering small parts.
Dip Soldering
            Dip soldering is the process of immersing connections in molten solder; one or more connections can be made in a single operation. This process is used on printed circuits, where the conductor pattern is on one side of the board and the components on the opposite side. Joints are mechanically secured, dipped first into liquid flux, then into molten solder.
2.5 Soldering Techniques
a.       Torch soldering (TS).
b.      Furnace soldering (FS).
c.       Iron soldering (INS).
d.      Induction soldering (IS).
e.       Resistance soldering (RS).
f.        Dip soldering (DS).
g.      Infrared soldering (IRS).
h.      Ultrasonic soldering.
i.        Reflow (paste) soldering (RS).
j.        Wave soldering (WS).
2.6 Soldering Advantages:
1.    The energy needed is relatively low compared to brazing and welding.
2.    Variations in heating methods vary.
3.    The connection results have good electrical and heat conductivity.
4.    Able to produce airtight (gas) and water-resistant (liquid) connections.
5.    Easy to repair and rework.
2.7 Soldering Weakness
  1. The connection strength is weak, unless reinforced by mechanical connections.
  2. The connection is likely to be weak or liquid if applied at high temperatures.
2.8 How to Soldering Iron
1.      Hold the soldering Iron in your right hand? Soldering Iron must be held properly so that the soldering does not vibrate.
2.      Hold the Wire Solder in the left hand, the solder wire must be held about 2cm from the end to make it easier to give solder wire when doing the soldering process.

3.      The position of the soldering iron must be around 45 ° regarding the parts of the component and the PCB which will be the process of connecting two or more workpieces, but there is no fusion between the workpieces connected together. Metal fillers (called solder) are liquefied at a relatively low temperature (lower than the filler metal temperature in the brazing process).

2.9 Product
            Good soldering is one of the most important aspects in the realization of an electronic circuit. Soldering is used to connect the legs of electronic components with a circuit on a PCB (Printed Circuit Board). So that it can be said that soldering is the process of connecting between electronic components and circuits. Good - poor connection between components in the circuit (system) is very much influenced by the badness of soldering



            Soldering machines are the process of connecting two or more work pieces, but there is no fusion between the work pieces connected together. So sometimes when we do soldering the results sometimes get good or less good results, so there are many weaknesses or advantages when we do soldering. Soldering has two important characteristics namely low surface tension and high permeability. The heat source of the soldering process usually comes from iron soldering, torch, or oven. The word solder comes from Latin, which is solidare, which means to make it strong. Soldering with copper-gold alloys and tin-lead alloys was first carried out around 4000-3000 BC.

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