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Lab 4: Soldering (09/25/2025)

Soldering is an important skill to have as an unmanned aircraft pilot or maintenance professional. According to Purdue University professor Nathan Rose, “soldering is the process of using a metal alloy with a low melting temperature to fuse together two other pieces of metal.” When done properly, soldering provides both a strong mechanical connection as well as a strong electrcial connection between two electronic components, and it is used often in things like computers and small unmanned aerial systems.

Safety Considerations

Soldering involves the use of a series of potentially dangerous or hazardous tools and materials, so it is imperative that proper safety precautions be taken. For instance, the tip of the soldering iron can reach approximately 650 degrees F, which can certainly cause damage or pain to a person or object. Also, many solders contain lead, which has proven itself to be a neurotoxin over the years. The following safety precautions should be utilized to prevent adverse results from taking over when soldering:

Wear safety glasses

Wear pants

Wear close-toed shoes

Optional: wear mask

Do not eat or touch face without washing hands

Wash hands with soap before leaving lab

Tips for Successful Soldering

Clean component leads before connection and soldering

Good mechanical connections when combined with the addition of soldering make for the best component connections

Heat the contact leads or wires to ensure proper flow and spread of solder

A clean soldering iron tip transfers heat easier than a dirty one

Required Materials

Personal protective equipment (highlighted above)

Soldering station including

Base station

Soldering iron

Sponge

Solder

Wire cutters (flush cuts)

Wire strippers

Wire

Helping hands

How to Solder a Lap Joint

Lap joints are a common application of the soldering skill, and it is an easy way to connect two electrcial components such as wires. In a lap joint, the goal is essentially to overlap the exposed portion of two wires facing each other and apply a reasonable amount of solder. This should create a mechanically and electrically strong bond between the two, and great results are achieved through practice. Below is a step by step guide in completing a lap joint with images to support.

Obtain all tools and safety equipment

Put on safety equipment

Prepare wires

Cut provided wires in half if longer than needed

Separate the individual strands

Strip the wires carefully and using the correct tool setting

The wires are gauge 24 in the example

The wires are stripped about 1/4 inch from the end

Set up the soldering station

Place the soldering iron on the lab bench, ensure that the power switch is off, and plug it into the provided outlet. (note: the soldering iron plugs into the soldering station for the model pictured)

Be sure that the soldering iron is placed in the metal spring holder

Power on the soldering station. Set the dial to ‘4’ or whatever yields desired results

While the station is heating, dampen the sponge with reverse osmosis (RO) water if possible

We use reverse osmosis water because it removes impurities and minerals from the water, meaning that these materials will have less of a chance of dirtying the soldering as opposed to tap water

If we use tap water, things like chlorine, calcium, lime, or other impurities may be present and weaken the soldering process by making the soldering process inconsistent (like welding with bubbles or something along those lines)

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Figure 1: Example of soldering station

5. Set up the helping hands

Make sure that your helping hands has at least two alligator clips if you have them. This will be used to hold both pieces for the lap joint.

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Figure 2: Helping hands clamp demonstration

6. Clean and prepare the soldering iron tip

This is done to make sure the surface has no interfering substances and to avoid leeching them into the solder. Use a mixture of wet sponge and wire brush material if possible.

7. Tin the wires

Tinning is adding a small amount of solder to the wires after heating them to allow consistent flow and results

Tinning is a necessary step that many forget. Tinned wires seem to hold longer lasting and better-looking solder joints, so be sure to prepare the solder correctly.

8. Solder the wires

A proper lap joint should have parallel and close wire distance with a smooth and shiny solder

Moving the wires while the solder is cooling produces a cloudy look and a weaker joint. Soldering the wires in a poor position may cause the joint to wear faster or have a worse electrical connection.

9. Continue to practice lap joints until you have achieved the desired results

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Figure 3: First attempt at lap joint. Poor Spacing and soldering technique

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Figure 4: Final attempt at a lap joint. Proper spacing and technique are demonstrated

10. Power off and unplug soldering station allowing it to cool

11. Clean up work area and return all tools to their appropriate locations

12. Wash hands before leaving lab to remove lead and other unwanted substances from your skin

How to Solder a Through-Hole PCB

Printed circuit boards, or PCBs, are found in many applications relating to computer operating systems. They can be somewhat complex looking to the untrained eye, but proper soldering technique can allow operators, especially in the UAS field, customize and repair parts to be in proper working order. For the purposes of this section, resistors are soldered into a PCB as an example of the application steps.

Identify the top of your PCB

Insert both leads of the resistor into the PCB

Bend the legs of the resistor slightly to hold it in place

Following the soldering tips from the Lab Joint section above, apply head to the resistor leg and soldering pad for about 1 second

Feed a small amount of solder into/onto the heated solder pad/component leg

Hold the soldering iron in place until the solder flows.

A proper through hole solder connection should have a small volcano-like shape, and it should show through both sides of the board. This shapes shoes that the components were properly heated, and it allows for maximum strength and electrical conductivity.

Continue to practice through hole soldering until you have achieved the desired results

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Figure 5: First PCB solder (second from the left on the top row)

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Figure 6: First PCB solder reverse side (second from the left on the bottom row)

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Figure 7: Final PCB solder front side (just below and left of the cutout on the top edge)

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Figure 8: Final PCB solder reverse side (just up and left of the bottom cutout)

8. Watch this video on using solder wick:

https://www.youtube.com/watch?v=ljRJiN6nHek⁠

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9. When using the solder wick, it is important to make sure you pay special attention to the placement of the wick, the temperature of the soldering iron, and the placement of the soldering iron over top of the soldering wick. These three items must be utilized properly for the application to get the best results from using the wick.

10. Using solder wick, remove the solder from the component and hole completely for practice (optional)

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Figure 9: Demonstration of proper solder wick use length

11. After all work is completed, be sure to allow components and tools to cool

12. Clean workstation and wash hands

Reflection of Lab Work:

Over the course of this lab, I was able to both polish up my skills first practiced last year in the realm of soldering. I was able to rekindle a gentle touch for lap joints, and I was able to find some success in their creation. I was very exciting to be soldering the PCB components, and that was a brand new task for me. Over the course of two hours I was able to hone in my skills on both, and I was able to complete at least three of each type of soldering application. Furthermore, I was proud to learn how to use a solder wick in such a short amount of time, and I imagine it could be very useful in a number of applications (especially with PCB components).

I hope to be able to use some of these skills in the future when I will be maintaining and perhaps even repairing unmanned aerial systems which contain these very components within them. Soldering has some risks and requires fine motor skills and patience, but it is a very necessary skill to learn in order to be a well rounded professional in the unmanned aviation industry. While I am not very enthused to be dealing with lead so intimately, it is a small price to pay for aviation safety. As has been said, a chain is only as strong as its weakest link, and I am determined not to allow any drone I am a part of falter because of repair or building related failures. Soldering properly is one step in the line of defense of accident prevention.

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