Transcript
R /C Techniques ©COPYRIGHT 1997,
TM
SR BATTERIES, INC.
Everything you ever wanted to know about soldering! Part 1 By Larry Sribnick
Resin based fluxes come in two forms. Kester makes Soldering Paste Flux SP-44 that comes in a small tin. You can also buy solder that has the flux
!
I don’t think there is any word in the R/C vocabulary that strikes fear in the hearts of modelers as much as the word solder does. If you want to make most modelers crazy, just mention that they’ll have to solder something! Soldering isn’t all that difficult once you know the basics. However, if someone doesn’t start you off right, you’re going to wind up with a lot of frustration and maybe a crash. Over the years, we’ve done a lot of soldering here at SR and we’ve taught a lot of people how to solder. I’d like to share with you what we’ve learned and hopefully convince you that your reaction to the word soldering should be, it’s a piece of cake!
VOLUME R5
built in. If it’s built into the solder, you’ll find that the solder isn’t solid but is actually a hollow tube with the flux on the inside. As you melt the solder, you’re also melting the flux and allowing it to flow onto the parts
First, the basics. Keep everything clean! The first concept you’ll have to learn is that everything has to be both chemically and physically clean. Physical cleaning is easy. You take a piece of fine sand paper or steel wool and clean the parts to be joined. Everything should be bright and shiny. If it isn’t, you’re doomed before you start. The only time I skip this step is when the parts to be joined are gold plated. Obviously, you can’t sand copper wire made up of fine strands but if the wire looks dark and discolored, find another piece of wire. If it’s a solid piece of copper wire, clean it! Flux... Chemical cleaning is taken care of by something called soldering flux. There are many different types of flux but for our purposes, we want a resin based flux (sometimes also called rosin). You do not want an acid based flux! Acid based fluxes are used by plumbers and will eat away the materials with time.
to be joined. I’m going to ask you to use both types. I want you to buy resin core solder and some straight soldering flux in a tin. I want you to have both because using too little flux makes soldering harder and I’d rather you used too much rather than too little.
Solder... On one hand, there’s a lot you could know about solder, but on the other hand, you don’t really have to know any of it. All you need to know is that it comes in different alloys, sizes, and with or without flux built it. For our purposes, general electrical and structural soldering, you want to use a 60/40 alloy. This means that the solder is 60% lead and 40 % tin. There are other solders that are used for other applications but I doubt that you will ever need them. For instance, for jewelry, or higher strength applications, you would use silver solder but most of us will never need it. For any electrical use, you’ll never use silver solder because of R/C Techniques, Volume R5, Page 1
its higher melting point. Strength is generally not an
Electric Flight motors and the motors used in our
issue in electrical work.
servos. If you get one of these soldering guns near a
After the alloy to use, the next thing to consider is
servo you can kiss your servo’s motor good bye. If
the size or diameter of the solder. Although solder
you’re an Electric Flyer, chances are that it could do
comes in many sizes, you’ll want to have both .062”
the same thing to the magnets in your expensive
and .031” on hand. The .062” solder will be used for
motors. Bottom line... Don’t own one. Don’t use one.
everything but the most delicate soldering. For circuit
Don’t allow one in your house! Have I made my point?
boards and small connections such as attaching 24g or
Soldering irons come in different sizes and
26g wire to Deans connectors, .031” solder will make
temperatures. The different heat ranges are sometimes
things a lot easier for you to control.
Irons, torches, and guns... Let’s start with torches. Most of you will never need one. The only time a torch will come in handy is when you’re assembling large diameter music wire landing gear or when you’re using silver solder. It is nice to have a torch handy at times but for the most part you won’t need one. When it comes to soldering guns... Don’t own one! Don’t use one! Don’t allow one in your house! Well, maybe that’s a little strong but I didn’t want you miss my point. Soldering guns work by induction. A strong magnetic field is created and its polarity is switched back and forth very quickly. This rapid polarity
expressed in watts making it harder to figure out what’s going on. For our purposes, a 30-40 watt iron that produces a temperature of about 650º F is about right. Although they are more expensive, you might want to consider a grounded iron if you think you’ll ever be working with solid state devices such as integrated circuits and such. Static electricity can kill these devices and a grounded iron is a must.
switching creates heat which in turn, melts the solder. The problem is in the strong magnetic field created. This induction is exactly the way the devices used to erase video and audio tapes work. In our case they will also erase the strength of the magnets used in our
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Wire... Wire comes in sizes called gauges. The higher the number, the smaller the diameter of the wire. So, a 26g wire is much smaller than a 12g wire. Most servos have leads made up of 26g wire. Battery packs should have leads made up of at least 24g wire. Extended battery leads should be at least 22g but at SR we like and use 18g wire for this purpose. For Electric Flyers, assuming the leads are kept as short as possible, use 18g wire for up to a 12 amp current draw. Use 14g wire for up to about 30 amps and 12g wire for anything higher. The longer the
length of the wire or the higher the current draw, the larger the diameter of the wire has to be. Wire also comes in stranded or solid. Use solid if you’re making up landing gear and the wire is there to reinforce the joints. Use stranded for everything else. The higher the strand count (how many individual smaller strands make up the finished wire) the more flexible the wire will be. For our purposes, we want the highest strand counts we can get to avoid wires breaking from vibration.
Holding fixtures... When you’re soldering, everything gets hot. If you’re trying to hold everything in position with your fingers when you’re making the connections, not only is it awkward, you’ll burn your fingers! There are commercial soldering fixtures that you can buy but it’s also very easy to make your own.
Chances are, you’ll want to have both. Radio Shack sells the commercial fixtures made up of alligator clips on ball swivels so that they can be positioned in any position. However, I have found that the spring pressure of the alligator jaws can be too high for small gauge wires. For this reason, I like to use the home made fixtures too.
To make your own soldering fixture, all you need is a block of soft wood, such as pine, and some clothes pins. Use any glue you’d like to glue the clothes pins to the top of the block at about 3” intervals. I like to use hot glue as it’s easy to reposition the clothes pins.
How to solder, 101... Finally, we get to soldering. The most important thing to remember is that Solder isn’t spackle! You don’t trowel it on and build it up in layer after layer to make a joint or splice. More, is definitely not better. You want just enough to make a sound, secure joint. Next, and this is very important, you are not heating the solder! You are heating the pieces to be joined and then adding the solder afterwards. It’s the heat of the pieces to be joined that melts the solder! Please re-read what I’ve just said. The most common mistake I see in soldering is that people use the iron to melt the solder and then use the hot melted solder to try to heat up the parts to be joined. This is the best way to make a bad joint (sometimes called a cold solder joint). Lesson 1... Okay, for lesson one you’ll need a strip of copper, brass, nickel plated steel, or nickel between 1/8” and 1/4” in width. You can get one of these at the Hobby Shop or, at the end of this Volume, we’ll give you information on an entire kit of supplies for learning how to solder. If the material isn’t nice and clean and shiny, use some steel wool or fine sand paper to clean it. You’ll also need a soldering iron, solder, holding fixture, and a small damp sponge. In addition, it’s a good idea to work in a well ventilated area and better yet have a little air blowing across your work area as some smoke will be produced as you’re soldering Plug in your iron and let it heat for a few minutes. You’ll know that it’s ready when it will melt solder. If you let a hot iron sit for a minute or less you’ll find that any solder on the tip starts to darken and scale over. The tip may even turn black and crusted over in places from flux actually burning onto the tip. That’s what the sponge is for. Get into the habit right now of every time you pick up the iron, the first thing you do is wipe off the tip on the damp sponge. Position the flat strap you’re going to be soldering to, between the jaws of your fixture. Apply the side of R/C Techniques, Volume R5, Page 3
the soldering iron’s tip against the strap material. By
blob of flux hanging from the end of the wire you’re
side I mean the small flat portion of the tip. If you use
used too much flux.
the pointed tip itself it’s hard to get the heat to transfer
Next, hold the wire up against one of the solder
from the tip to the strap material. After a second or
buttons you’ve formed. Clean and then apply the hot
two, apply the solder to the place where the tip and the
soldering iron tip to the point where the wire and
strap make contact. As soon as the solder starts to
button meet. As soon as the solder melts and the wire
melt, remove the tip of the iron and the solder and
sinks down into the button, remove the tip but hold the
you’ll leave a nice small button of solder on the strap
wire very still for a second or two. If you move the wire
material.
as the solder is cooling and hardening, you’ll get a cold
You’ll notice that the button looks all shiny and glazed over. It probably looks like it has a coating of an
solder joint so hold the wire very still! Repeat this process over and over again with every button.
amber liquid. That’s the flux that has melted and now
When your done, you’ll be ready for Part 2 where
cooled and hardened on the work. Don’t worry about
we’ll apply the skills you’ve learned. You’ll learn how
it. Repeat this process over and over again down the
to join wires, solder Deans, Sermos, and Astro
length of the strap material until you’re comfortable
connectors, solder circuit boards, motor terminals,
with the process and can control the size and
pushrod ends, and landing gear.
placement of the buttons. Experiment with more solder and less solder. Applying heat longer and shorter. But, don’t forget to keep cleaning your tip on the sponge between buttons. Making 50 buttons would not be too many.
Lesson 2... Now for the wire. Strip about 1/8” of insulation from the end of a piece of 24g wire. Touch the stripped portion of the wire to the soldering flux in the tin. If you can just barely see that there is any flux on the wire you’ve used the right amount. If it looks like a
Soldering Starter Kit... Everything I’ve mentioned can be found at a good Hobby Shop or Radio Shack. For your convenience, we have put together a starter kit which includes: .031” and .062 resin core solder, soldering flux paste, 24g, 18g, 14g, and 12g wire, 1/8” and 1/4” wide nickel strap material, and an assortment of various heat shrink sizes that you’ll need for Part 2. Give us a call at 631286-0079 if you’d like more information or pricing on the Soldering Starter Kit.
©1997 SR Batteries, Inc.. All rights reserved. No portion of this document may be reproduced in any form without the express written permission of SR Batteries, Inc., Box 287, Bellport, New York 11713 Phone: 631-286-0079 Fax: 631-286-0901 Email:
[email protected] R/C Techniques, Volume R5, Page 4
