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Subelement L
Installation, Maintenance & Repair
Section 79
Repair Procedures
When soldering or working with CMOS electronics products or equipment, a wrist strap:
  • Correct Answer
    Must have less than 100,000 ohms of resistance to prevent static electricity.
  • Cannot be used when repairing TTL devices.
  • Must be grounded to a water pipe.
  • Does not work well in conjunction with anti-static floor mats.

When soldering or working with CMOS electronics products or equipment, a wrist strap:

Must have less than 100,000 ohms of resistance to prevent static electricity.

Please see ElProCus site for the article What are the Methods of Soldering Electronic Components?

Also, Instructables Circuits site for the article How to Solder

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Which of the following is the preferred method of cleaning solder from plated-through circuit-board holes?
  • Use a dental pick.
  • Correct Answer
    Use a vacuum device.
  • Use a soldering iron tip that has a temperature above 900 degrees F.
  • Use an air jet device.

Which of the following is the preferred method of cleaning solder from plated-through circuit-board holes?

Use a vacuum device.

From wp2ahg:

A vacuum device like a solder sucker bulb, desoldering station or desoldering pump will suck melted solder off of solder pads and out of through-holes.


A. Use a dental pick -- a dental pick could destroy traces and solder pads. Even if the solder were melted, the dental pick would just push the solder around. Too destructive.

C. Use a soldering iron tip that has a temperature above 900 degrees F. -- a 900+ degree F soldering iron would definitely melt the solder, as well as the PCB. 900 degrees F is too hot. Also, this would only melt the solder, and would not remove it.

D. Use an air jet device -- an air jet would blow solder everywhere, making a mess and potentially causing shorts and solder bridges.

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What is the proper way to cut plastic wire ties?
  • With scissors.
  • With a knife.
  • With semi-flush diagonal pliers.
  • Correct Answer
    With flush-cut diagonal pliers and cut flush.

What is the proper way to cut plastic wire ties?

With flush-cut diagonal pliers and cut flush.

From wp2ahg:

Cutting the tail off of a plastic wire tie using flush-cut diagonal pliers flush with the wire tie case leaves no sharp edges that could scratch or cut someone.

The other tools (scissors, knives and semi-flush diagonal cutters) all leave a sharp edge that is raised from the wire tie case, and that could cause an injury.


See Wikipedia's article on Diagonal pliers

Also, please see the Canadian Center for Occupational Health and Safety site for the article on What are common types of pliers and wire cutters?

And, see the Maun Industries site for the article What are diagonal cutting pliers and what are they used for?

Please see the UK RS site for the article on The Complete Guide to Cutters

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The ideal method of removing insulation from wire is:
  • Correct Answer
    The thermal stripper.
  • The pocket knife.
  • A mechanical wire stripper.
  • The scissor action stripping tool.

The ideal method of removing insulation from wire is:

The thermal stripper.

From wp2ahg:

Thermal strippers cut the insulator on the wire by melting through it. This avoids the risk of cutting any wire strands.

The other methods (pocket knife, mechanical stripper, and scissor action stripping tool) all cut through the insulator using sharp metal edges, which could cut wire strands.


Please see the Wiring Harness News site for the article on Back to Basics Mar/Apr 2020 – Thermal Wire Stripping

Also, see Hakkousa site for the article The Need for Thermal Wire Strippers

And, the Hackaday site for the article HOT WIRE STRIPPERS ARE PROBABLY THE BEST TOOL YOU AREN’T USING

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A “hot gas bonder” is used:
  • To apply solder to the iron tip while it is heating the component.
  • Correct Answer
    For non-contact melting of solder.
  • To allow soldering both sides of the PC board simultaneously.
  • To cure LCA adhesives.

A “hot gas bonder” is used:

For non-contact melting of solder.

From paradisecs:

When removing a large scale integrated circuit chip, the multiple contacts present a desoldering challenge.

The best tool for this work is a hot gas bonder that heats up the solder nearly instantly, allowing all LSI leads to free up from the molten solder, and making it easy to left the device out without distortion of the solder pads.

This process is reversed to put in the new LSI chip.


For more information, please see the Avio Co site for the article Principle of Pulse Heat Unit (Hot Bar Bonder)

View YouTube video from the RGL ENTERPRISES channel called Semiconductor Equipment Corp Model 4400 Hot Gas Die Bonder, 0.39 seconds

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When repairing circuit board assemblies it is most important to:
  • Use a dental pick to clear plated-through holes.
  • Bridge broken copper traces with solder.
  • Correct Answer
    Wear safety glasses.
  • Use a holding fixture.

When repairing circuit board assemblies it is most important to:

Wear safety glasses.

Please see United States Department of Labor, OSHA 1910.133 - Eye and face protection.

Also, see the American National Standards Institute's site for ANSI/ISEA Z87.1-2020: Current Standard for Safety Glasses

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