Soldering Equipment and Techniques

Soldering Equipment and Techniques

By Roger Heid

 

In your quest to improve your model railroad skills and experience you might, sooner or later, try to do some soldering. You may already have some or a lot of experience. This blog addresses those who have little or no experience with a solder iron. Myself, I started soldering in 1963 in the electronics service industry. Since then I have learned a lot, and I think I know what I am doing. As an apprentice, I acquired my skill and wisdom in a supervised School of Hard Knocks.

I will not get much into the equipment and techniques common in the plumbing and automotive industries or the likes. Soldering tasks encountered in the realm of electric model railroads are very similar to those common in the electronics manufacturing and service industries. That’s what I will mostly stick to.

Solder is an alloy consisting of lead, tin, silver and brass. Depending on the purpose of the solder, the combination and mix ratios will vary. Solder is used to fuse two or more metallic work pieces together, whereby the melting point of the solder used is lower than the melting point of the metal pieces to be fused. Different types of solder have different melting points. The typical 60/40 tin/lead (Sn/Pb) solder melts between 360 and 370 degrees Fahrenheit. Take note, that the process of soldering must not be confused with welding, which is an entirely different procedure that does not belong here.

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Sample of recommended solder

There is a plethora of solder irons or stations on the market. A simple solder iron costs just a few bucks, ranging between $ 10 and $30. Such devices can handle the basic tasks, such as soldering two wires together or to solder a wire to some kind of connector or lug. However, they lack the finesse to deal with more complex situations like changing components on a PCB (Printed Circuit Board), especially solid state components such as transistors and integrated circuits (IC), also called chips.

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Two examples of ordinary solder irons

Typically, these types of irons get too hot. Too much heat applied can cause permanent damage to whatever you are trying to work on. On the other hand, some models do not get hot enough to handle bigger jobs. On any of these types you cannot change the temperature. You’re stuck with what you have. On the cheap ones, you also cannot change the physical tip configuration. You’re stuck with one size which may prove to be too clumsy to effectively take care of very small solder points. Trying it anyway can easily cause irrepairable damage and tons of frustration. Not recommended. These inexpensive solder irons will put a limit to what you could actually do having the right equipment. A friend of mine ordered a good solder station after he ruined a piece of electronics that had cost him more than the new solder station. You see, there is definitely a hard way to learn things.

There are also these handy-dandy little irons that clamp on to the model railroad tracks. They have been around for decades. Personally, I take those with a grain of salt. They are good for small simple jobs and will do, in a pinch. They do not produce enough heat for a more massive project.

Now, here is word of caution. You can buy a 12 Volt solder station, mostly in Automotive Supply Stores. Some have connector clips small enough to clip to model tracks. They are intended to be field equipment in the automotive industry. They draw way too much current. Your power supply or control station will either shut down or move to the eternal hunting grounds. In this category, Weller makes a real good one, temperature controlled. It costs almost $110.-. It is obviously not your choice.

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Left: For Model Railroad use   Right: For automotive use

Some guy I know clamped one of these on his Atlas tracks in order to solder a couple of wires together. His rather inexpensive analog power pack smoked, stank and went to heaven, in short order. That iron he used draws 80 Watts. Uffda!

If you should decide to get one of these clip on irons, be careful about what you are getting and don’t expect it to do what it is not capable of.

The tricky part of soldering is that the temperature applied has to be high enough to make the solder melt, but also high enough for the solder to actually fuse with the work pieces. The required temperature could very well be a lot higher than the melting point of the solder. The work pieces at hand may be big in volume, thus absorbing a lot of the heat produced by the solder tip, preventing the actual temperature to reach the fusion point. In this case you are merely ‘glueing’ the pieces together. This is referred to as a ‘Cold Solder Joint’. Such a joint does not provide solid electrical connectivity; it may even break loose, after some time.

By the same token, applying the temperature of the level mentioned above, namely not high enough, in a situation where the work pieces are tiny, possibly embedded in some form of plastic material, this very same temperature can be outright destructive. No metallic pieces large enough to absorb the extra heat are present. Instead, the extra heat is absorbed by something that cannot stand to be overheated. You get the drift?

That’s when a ‘Temperature Controlled Solder Station’ comes into the picture, preferably with a digital temperature read out. Here you can adjust the temperature to the desired level. Keep it as high as necessary, as low as possible. This takes some experience.

Such a solder station should also come with solder tips of several types and sizes, or they should be available as an option. The kind of solder station I am talking about you will not find at Sears or in hardware stores. Due to their current status, Radio Shack is quite iffy. I would not bother. Here comes the question of what brand name to choose. There you need to know that there are solder stations designed to tackle job situations above and beyond of what you will ever encounter. Those can cost hundreds of bucks. There is no need for this type.

My chosen brand name is Tenma. While still working in the electronics field, I used one of their stations for more than 10 years, on a daily basis, before it gave up the ghost. Four years ago, I bought a new one for under $100.-. It may outlive me. My supplier is a company called MCM. I have been dealing with them since 1982. Well, that’s me. All of the items mentioned in this blog can be had from them. Weller is also a very good brand. In my opinion, their products are a tad too expensive, for my taste.

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Left:  Tenma Temperature Controlled Solder Station   Right: Selection of solder tips (optional)

You notice there is a little square sponge on top of the station body. While under heat, the solder tip will develop some nasty gunk (oxidation), dark grey to black in color, making it hard or difficult to use the iron. Rubbing the tip on that wet or moist sponge will eliminate this problem immediately. Also, when you first start using a brand new solder tip, it needs to be broken in. I know this sounds strange, but it is true. You need to coat this tip with solder in order for it to work properly. Some surface contamination on this new tip may prevent this from happening.

After the tip is heated up, a few swipes across that wet sponge will take care of this situation. There may other methods to accomplish this, but the wet sponge has never failed me.

Good soldering is a skill that needs to be learned; there are no two ways about it. I will give you a comparable analogy in a non-related field. During the 1980s, I managed several garage and basement rock bands to assist them to elevate themselves to a level where they could get and perform pay gigs. Heavy Metal was in vogue.

There was this one kid who had dreams about being a Rock Star, a Guitar Hero. He could play guitar amazingly well, for is age (17), but all he had was a fairly decent acoustic guitar, nothing else. These heavy metal bands seldom, if ever, perform in the so-called ‘unplugged’ mode. His parents could not afford the required equipment. He could not join the band. In spite of his skill, his instrument was not up to the task.

Then there was this kid with similar aspirations, but he had wealthy parents. His dad bought him a very expensive electric guitar and a ton of associated equipment, enough to fill a van. He could not play worth a darn. He also could not join the band. His lack of skill made all of his equipment useless.

You can make whatever you wish out of this little story.

Now let us talk about the very solder you will be using. Before you walk into some store, asking for solder, and the clerk asks what kind, and you have no idea, get a load of this. The information below will naturally help you to make the proper choice when you are facing a shelf with umpty different solders on display. If you ask some clerk for help, the clerk will most likely disappear to find the only guy in the whole store who can answer your questions. Most likely, this Solder Guru is on vacation, in Hawaii.

The solder we use for our purposes has to have a rosin core. Rosin serves as a flux to assist the fusion process. Rosin flux is a necessity. Without it, the fusion would be very difficult to achieve; it may not take place, at all.  This rosin core solder comes in different thicknesses.

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Stay away from the thick stuff. It gets in the way. If you are trying to tackle a tiny joint, the sheer thickness of the solder can prevent you from being able to see the joint. On top of that, when touching the solder with the hot tip, it will most likely melt more solder than needed. This molten solder will find its way into places where it is not welcome, for a variety of reasons. If you are working on a PCB (Printed Circuit Board) the dreaded excess molten solder is very eager to fuse with another joint close by, a place where it should not be. It just built the infamous ‘Solder Bridge’ for you. Failure to notice this will be a major contributor to a ‘Bad Hair Day’, your hair, if you have any left. Now you can understand my recommendation to get the solder in the thinnest form you can find.

Of course, the next thing that will happen is you need to tackle a big job, requiring lots of heat and lots of solder. You’re having a hard time feeding that thin solder to the hot spot fast enough. You wished there were such thing as powered solder speed feeder. Good luck with that! Well, why don’t you just take a length of the thin solder, cut it in three equal length sections and braid the three sections. Bingo! Now you got the thick stuff. How about that!

Time has come to cross the ‘Solder Bridge’. It is quite obvious that you need to tear it down, get rid of it. After several attempts to do so, utilizing all sorts of innocent devices and ill-fated methods, you finally managed to break the PCB in half. You no longer need to worry about a ‘Bad Hair Day’. By now, you ain’t got no hairs left, not a single one.

Once again, there is a solution. It is called ‘Solder Wick’ or ‘Solder Braid’. You cannot possibly be without it.

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This device consists of very thin copper wires, braided and shaped like a narrow ribbon. It is drenched in resin flux; you know why. You place this ribbon between the bridge and the solder tip. Moments later, all solder is gone. Poof! Just like that. This solder wick is very useful in any situation where unwanted solder needs to be removed, for whatever reason. The so-called ‘capillar effect’ sucks molten solder into the wick. When saturated, just feed more wick. It’s that simple.

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But wait! This is not the end of it. In the process of performing certain solder jobs you wish you were born with three or four hands. This not being the case, you need to employ artificial hands. One needed item is a bench or table top vice, suitable in size. Those can easily be found. Mine even has a ball joint between the clamp and the actual vice.

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Don’t even bother trying to work without one; otherwise something important will fall on the floor. You will then step on it and break it, or your cat will grab and hide it, or your dog will bury it in your back yard, or the maid will suck it into the vacuum cleaner. Pick your choice.

And then there will be times when you think you’re blind. I use magnifying lenses that I strap in front of my face. They can be found in many places. I prefer these over desk lamps with lenses, simply because I can put my face in any place where needed, not being limited by the stationary nature of desk lamps, plus I can place a battery operated LED light source to wherever it gives me the best results. However, this is a matter of personal preference.

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As you can see, soldering is not as easy a task as it may seem, at first glance. As I mentioned before, this is a skill that needs to be acquired, step by step. If you are new to this, you can go about this in two ways; the right way or the wrong way. The choice is your decision. In this skill, it is experience that makes the master. Only hands on practice will give you the experience.

If you decide to be serious about this soldering business, you need to practice on some dummy projects of your choice, before you tackle important projects. As they say: ‘Practice makes perfect.’ You decide how good you want or need to be.

In parting, I want to mention three more types of soldering devices. One is the classic solder gun, originally intended to be used in the field, usually by electricians. It works well, but for advanced soldering techniques it has its limits.

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Next are a variety of battery operated solder irons. They work and they are convenient. But once again, they have their limits. They can’t handle big jobs. For finesse work they are too clumsy. The batteries don’t last long.

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Finally, there are the types that get their heat from a butane gas flame. Personally, I hate them. But that’s me. I have no further comment on those.

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Last not least, I need to mention that, at a slightly higher price, lead free rosin core solder is available. Lead, by itself is toxic. Wash your hands after extensive use of leaded solder. During the soldering process, leaded solder emanates toxic fumes; not at dangerous levels, though. But if soldering with the leaded type all day long, all year long, the room you are in needs to be ventilated. Lead free solder is a solution to this. The difference in melting point is insignificant.

There are probably some issues I have not covered. I am hoping some experienced ‘Solderer’ will add more wisdom to this article.

If you should have any questions, please post them in the Forum under the appropriate topic.

Thank you.

One Response to Soldering Equipment and Techniques

  1. peter martin says:

    Roger, nice article and well considered. I have replaced most of my soldering guns with a Hackco (Hako) soldering station (Model FX-888). The unit is mid range in their line of soldering stations. It is ideal for all gauges (save #1 track) of model railroad soldering. The stations seem to be the best choice for in home layout work; they provide controllable heat and they can keep up with most heavy work. I like the ability to regulate wattage (heat)as it can prevent the melting of surrounding parts to the solder point. I also like the resistance soldering systems, I brought a Black Beauty, the top of the line, at garage sale for pennies. If you need heat and powerful soldering, such as gauge one track this is the device to use. Again thanks for your many articles.

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