Soldering

Basic Electricity

  • Question 1

    Both soldering irons and soldering guns are tools used in the process of electrical soldering. Describe what each of these tools looks like, and how they function.

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  • Question 2

    What does it mean to tin a piece of wire prior to making a soldered connection with it?

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  • Question 3

    All electrical soldering, and most other forms of soldering as well, requires the addition of a substance known as flux. What is the purpose of adding “flux” to the soldering process, and what type of flux is typically used for electrical soldering?

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  • Question 4

    As in all technician tasks, safety must be your first priority. Soldering harbors specific dangers of its own that you need to be aware of. Explain what precautions you need to take with regard to the following aspects of soldering:

      • Safe handling of soldering iron/gun

      • Safe handling of solder and flux

      • Personal protective equipment

      • What to do (and not do) after soldering

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  • Question 5

    Semiconductor components such as diodes and transistors are easily damaged by the high temperatures of soldering, so care must be taken to protect these components during the soldering process. One way to do this is to use a heat sink to draw heat away from the component without cooling the connection point too much. Heat sinks made out of sheet metal may be temporarily clipped to the component leads, one at a time, to prevent the solder’s high temperature from thermally conducting all the way to the component body:



    In the absence of a formal heat sink, can you think of any ways to fashion your own “impromptu” heat sinks out of commonly available tools and/or objects?

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  • Question 6

    When soldering a wire into a metal lug, which of these positions would be considered best for soldering iron and solder?



    Explain why you think one of these positions is better than the others for producing a sound solder connection between the lug and the wire.

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  • Question 7

    What is a cold solder joint? Identify its causes, its appearance, and the means of correction.

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  • Question 8

    After a period of use, the tip of a soldering iron (or a soldering gun) becomes dark and “encrusted” with oxidation and flux residue. Describe why this accumulation impedes the soldering process, and how it may be removed.

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  • Question 9

    What may be done if you solder a component into a circuit board and then realize you soldered it in the wrong place? What, exactly, must you do to move this component to a different location on the board?

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  • Question 10

    Explain what surface-mount devices are, and how the soldering and desoldering processes for them differ from the processes used to solder and de-solder “through-hole” components on printed circuit boards. The following illustration contrasts “through-hole” component construction versus surface-mount construction for a voltage divider circuit (three resistors connected in series):



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  • Question 11

    The equation for converting degrees Celsius (oC) to degrees Fahrenheit (oF) is as follows:


    TF = 9

    5
    TC 32

    Use this equation to convert the following temperatures from Celsius to Fahrenheit:

      • 0oC =

      • 100oC =

      • -40oC =

      • 250oC =

      • 310oC =

    Now, algebraically manipulate the equation so that you may solve for degrees Celsius from a given figure in degrees Fahrenheit. Show all your work, then check your results by working backward through the five calculations above to arrive at the original figures in degrees Celsius.

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  • Question 12

    What is soldering? What is solder?

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  • Question 13

    Find a printed circuit board with soldered components on it, and bring it with you to class for discussion. If you have access to a scrap bin from an electronics or computer repair shop, this would be an excellent place to find a printed circuit board. On your PCB, try to identify:

    • Number of layers on board
    • “Traces”
    • “Lands”
    • Cold solder joints (if any)
    • Solder bridges (if any)
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