LEAD-FREE SOLDER: CHARACTERISTICS AND DIFFERENCES

The Restriction of Hazardous Substances Directive (RoHS), adopted by the European Union in 2003, changed the world of electronics manufacturing forever — especially with regard to solder. The lead-free solder necessary for RoHS compliance presents a set of unique challenges to PCB-manufacturing businesses.

While no one is disputing the fact that lead-free solder is less hazardous to those working in PCB assembly, working with unleaded solder has its complications. Lead-free solder doesn’t flow as easily as traditional leaded solder and, compared to a PCB using leaded solder, the soldered joints on a circuit board using lead-free solder will look noticeably different. You’ll also notice a dearth of top fill on through-plated PCBs (you’ll seldom get more than a seventy-five percent fill). In addition you’ll notice that unleaded solder joints are less shiny than joints using traditional solder because of the differences between the alloys.

It’s important to note that lead-free solder melts at a higher temperature than leaded solder. The exact melting temperature depends on the particular unleaded alloy you choose. A common mixture is ninety-nine percent tin, point seven percent copper, and point three percent silver; this alloy will melt and flow pretty well at two hundred seventy-five degrees.

Replacing and Modifying Equipment

There’s a good chance that the majority of your existing soldering equipment will need modification or replacement for lead-free soldering. You will at least need to replace your soldering irons’ tips — to avoid possible contamination issues — or you may need to replace your soldering irons and soldering stations altogether if they can’t reach the higher temperatures required for melting unleaded solder. Larger soldering equipment (e.g., wave soldering machines) will likely need to have their soldering baths replaced and you should consider replacing your flux as well because the PCBs you’ll be soldering will be lead-free, too.

With regard to solder pots and other types of hand-operated soldering equipment, you can either replace their baths or you could empty the equipment of solder, clean the bath, and coat it with oxide paint, which will save you some money; once the oxide paint has dried you can go ahead and fill your bath with lead-free solder and you’ll be ready to begin soldering again. While transitioning from traditional solder to unleaded solder can seem like a hassle, it’s rather easy and requires minor adaptation.

SOLDERING IRONS: WATTAGE VERSUS TEMPERATURE

A soldering iron has to rapidly heat metal parts above the temperature commonly used in electrical and electronic work — 60/40 or 63/37 tin/lead melts between three hundred sixty and three hundred seventy degrees — in order to make good connections. The solder you apply to the joint will melt and flow smoothly after it has been quickly heated. If your soldering iron heats too slowly the heat will be able to transfer to your components (resistor, capacitor, etc.) which can cause them to overheat and become damaged and, if you’re soldering insulated wire, too-slow heating can cause the insulation to weaken or melt.

Soldering tip temperatures are generally set between seven hundred fifty and eight hundred fifty degrees so that the temperature of the solder will raise above its melting point. Given that most solders have melting points below four hundred degrees you might be wondering why the soldering tip gets so hot. The answer is that using a higher temperature stores heat in the tip, thus speeding up the melting process; this enables you to solder your connections without applying excessive pressure on the joint. In addition, these high temperatures allow the proper formation of intermetallic layering between the components and solder to form, which is crucial for creating reliable electrical and mechanical solder joints.

Since we’ve established that the temperature is perhaps the most important aspect of choosing a soldering iron or soldering station, the next point of confusion is that soldering irons and stations are rated in watts rather than degrees. Most inexpensive soldering irons are actually unregulated, which means that the temperature of the tip isn’t controlled; they don’t advertise a temperature because the tip’s temperature will significantly change during use. The following data on certain unregulated soldering irons (fifteen, twenty-five, and forty watt) will shed some light on why choosing the right wattage is important.

A fifteen watt soldering iron has a resting temperature of roughly five hundred forty degrees Fahrenheit. However the temperature will drop to around four hundred twenty degrees after briefly wiping the tip on a damp sponge and soldering a couple PC board pads. This happens because the iron’s fifteen watt heat-storage capacity can’t maintain its resting temperature during use — it doesn’t have the capacity or the ability to restore temperature so it quickly cools when used. You can work around this limitation by allowing some rest periods between soldering joints, but if you’re doing work that requires more heating power — e.g., tinning a stranded wire — a fifteen watt iron won’t have enough power to get the job done.

A twenty-five watt iron has a resting temperature of around six hundred forty degrees and will retain much of its resting temperature (i.e., over six hundred twenty degrees) after soldering more than ten PC board pads. With regard to tinning wire, a twenty-five watt soldering iron can handle fourteen gauge wire well, but it lacks the power to tin ten or twelve gauge wire. If you tried to tin a ten gauge wire you can get the iron’s tip hot enough to melt solder in around two minutes, but by that time the insulation is hot enough to melt as well. The goal is to heat the surfaces being soldered, so we don’t want to heat the surfaces for more than a couple seconds or we risk damaging components and wires.

A forty watt soldering iron’s resting temperature is roughly seven hundred forty degrees and will keep a tip temperature of over seven hundred degrees through repeated PC pad solders. While a forty watt iron has enough power to easily tin twelve and fourteen gauge wire, ten gauge wire will still be on the slower side. Lower wattage soldering irons and soldering stations can really slow down your work and may not be suited to the electrical or electronic work that you’ll be doing.

HOW TO REPLACE ELECTRIC GUITAR PICKUPS

Swapping the pickups in your guitar can dramatically affect its tone; you can transform a student model guitar into tone machine that nails your favorite sound simply by installing the right combination of pickups and tone/volume potentiometers, and it’s surprisingly easy to do.

(Note: It’s best if you already have experience with a soldering iron.)

First things first: you’ll need wire cutters (preferably needlenose), new strings, a Phillips head screwdriver, solder, and a soldering station or iron. Every electric guitarist should invest in a good soldering iron, because almost all the electronic repairs you’ll ever need to do require one.

Remove your guitar strings to make things easier on yourself. On a rear-routed guitar you’ll remove the plastic plate on the back of the guitar or, if you have a Fender-style guitar, you’ll remove the entire pickguard to which the pickups are attached. Be sure to keep the screws organized according to where they came from, i.e., keep pickups screws, screws from the pickguard or backplate, etc. in separate piles.

Next you should orient yourself by identifying where the jack is, which potentiometer is which, where the selector is at, and how the wires connect the various parts. Use your needlenose pliers to pull out and separate the wires to make things easier, but don’t pull any wires out completely, as this will damage both the wires and components.

Take your new pickup and pull each colored wire out. Strip an inch or so of the black wire coming out of the pickup. After that pull each of your new pickup’s wires out and apart from each other. On rear-mounted guitars you’ll then feed the new pickup’s wires into the cavity making sure there is enough space in the cavity for the new pickup’s wiring.

Let your soldering iron warm up for five to ten minutes. Examine where the guitar’s current pickup’s wires solder to the jack, pots, etc. while you wait. Desolder one by putting the soldering iron’s tip to the solder point. Be sure that you’re desoldering the wires for the pickup you’re replacing, which can be accomplished by pulling on that pickup’s wire.

Break out the needlenose pliers again and pull the wire from the liquified solder. If you have a desoldering bulb you can suck up the excess solder — otherwise take the correspondingly colored wire from your new pickup and solder it where the old one was. If the point where you’re soldering has a hole, loop the wire through first. Hold your solder to this point and touch it with the soldering iron to get just enough solder to secure the wire. Do this for each wire and solder point.

Take the old pickup out, plug your guitar into your amp, and turn it up. Touch the new pickup’s screws and magnets with a screwdriver and, if you hear a popping noise each time you tap the screws or pole pieces, you’ve successfully soldered your new pickup in place.

Screw the pickup in position — with the wire facing down, i.e., toward the bridge — replace the backplate or pickguard, and restring your guitar. That’s all there is to it.

Building a Distortion Pedal with a Kit

Distortion pedals — which compress the peaks of your electric guitar’s sound wave and add overtones, resulting in a warmer, dirtier, and fuzzier guitar tone popular in rock, blues, punk, and metal music — are the most popular effects pedals around and you can easily build your own distortion pedal with a kit. Let’s have a look at the process of distortion pedal assembly. You’ll need a distortion pedal kit, wire strippers, a screwdriver, and a soldering iron.

Build Process

First off, you’ll need your distortion pedal kit, which you can buy from a number of online retailers. There are a variety of different types of distortion pedals so you’ll need to make a decision on what type of distortion suits the music you play. A Tube Screamer-type pedal sounds much different than pedals based on Big Muff or Turbo Rat circuits. If you play grunge or punk music you’ll want a fuzzier distortion pedal with lots of overdrive and, if you play the blues, you’ll want a pedal with good compression and more midrange.

Take the components from your kit and attach them in the appropriate places on the perfboard. The components will plug straight into the board and should fit securely in their respective slots. These components consist of capacitors, transistors, and diodes. Every kit is different, so be sure to consult your kit’s schematic to find out what goes where.

Strip the kit’s wires’ ends with your wire strippers and wrap the stripped ends around the terminals of each of the components. The wires are likely all one color, meaning that you don’t have specific wires for specific components. Although all kits are different, you can expect to connect five to ten wires to the terminals.

After allowing your soldering iron or soldering station to warm up, solder the wire connections. A mildly active rosin-core solder is best for these kinds of circuits.

Attach the perfboard to the bottom of the pedal’s chassis. Use your screwdriver and the included screws to secure the perfboard in place.

Then secure the top part of the pedal’s chassis to the bottom half. Plug your distortion pedal into the wall and test it out. If you plug the pedal in and the LCD doesn’t light up when you turn the pedal on then you’ll need to check your connections. If the light does come on and no sound comes out of your amp or the sound cuts in and out with you guitar plugged into the pedal you’ll need to take the pedal apart and ensure that everything is correctly connected.

So long as you have experience with a soldering iron, building a distortion pedal from a kit is a rather straightforward process that will give you the experience and confidence you’ll need to start building more complex circuits.

REPLACE YOUR GUITAR AMP’S FAULTY INPUT JACK

Your guitar amplifier is useless if its input jack is faulty: either your signal is unable to pass through the jack or it’s distorted dramatically (and not the good kind of distortion). Given the time, effort, and materials needed to diagnose and repair a faulty input jack, you’re better off simply replacing the jack altogether. And you don’t need an extensive knowledge of guitar amps to do this simple repair. What you’ll need are a mono input jack, a soldering iron, and solder made for electronics — not to mention experience with soldering.

1. Plug in your soldering iron or fire up your soldering station and give it a few minutes to warm up.
2. Unless you have an open-back amp you’ll need to remove the amp’s panel to access the electronics inside.
3. Unscrew the nut securing the jack to the panel. There will be two wires connected to the jack: the hot wire is the wire connected to the prong touching the input jack’s metal ring; and the ground wire is the wire connected to the prong touching the plastic ring.
4. Melt the solder connecting the wires to the faulty input jack by touching each solder joint with the tip of your soldering iron and then discard the faulty jack.
5. Lightly touch the soldering iron’s tip to your fresh solder to melt a drop on the tip. (You can use traditional leaded or lead-free solder; it doesn’t matter aside from the temperature you’ll use for your soldering iron. However, you should only use solder marked for use with electronics as other types of solder can corrode and damage your amp’s electronics.)
6. Touch the end of the hot wire to the replacement input jack’s prong connected to the metal ring.
7. Touch the drop of molten solder to the point where the input jack’s prong and the wire are touching. Once the heat from the soldering iron is removed the solder will harden rapidly and this will securely connect the wire and input jack.
8. Follow the same procedure outlined in the previous three steps to connect the ground wire to the prong connected to the plastic ring.
9. Insert the end of your replacement input jack in the hole left by the faulty jack. Secure your new input jack with the nut you removed from the faulty jack earlier.
10. If you needed to remove the guitar amp’s panel, replace the panel. (A final note: Your soldering iron will retain heat for several minutes after being unplugged, so it’s a good idea to wait at least fifteen minutes in order to give it time to cool down.)

TROUBLESHOOTING YOUR GUITAR’S VOLUME CONTROL

Your electric guitar’s volume and tone controls are a fast, convenient way to raise and lower your guitar’s bass, mid, treble, and output volume without having to make adjustments at the amplifier; this is extremely helpful when practicing and performing, enabling you to tweak your tone and volume in the middle of a song.

When your guitar’s volume control fails the wires and connections need to be inspected. You’ll want to use your digital multimeter (DMM) to measure the resistance in ohms of the volume potentiometer. Potentiometers, or pots, are the electronic components to which the guitar’s volume and tone knobs attach. The problem with your volume control can be easily isolated and repaired with this simple three-step troubleshooting guide.

(Note: You’ll need a digital multimeter and small Phillips-head screwdriver. Ensure that your guitar is not plugged in to anything while testing your volume controls and, if you have any active electronics, remove their batteries.)

Step One

Remove all plates, knobs, and pickguards preventing access to your guitar’s electronics. Gibson-style guitars usually have a plate on the back of the body that covers the guitar’s electronics. Fender-style guitars, on the other hand, are generally accessed from the front, requiring you to remove the pickguard and the knobs attached to the potentiometers.

Step Two

Check the volume control pot’s wires and connections for any loose soldering or shorts. A loose or broken connection might be the source of the problem and this can be easily fixed by resoldering the connection with your soldering iron.

Step Three

Next you’ll want to test the volume pot using your digital multimeter. Set the DMM’s meter dial to 200k on the ohm (Ω) section of the dial and then turn the guitar’s volume control all the way in one direction. Touch the digital multimeter’s probes to the middle terminal and one of the outside terminals (potentiometers have three terminals). After that turn the volume control in the opposite direction. Depending on the direction the knob is turned the reading on your DMM will increase or decrease. If the reading on your DMM doesn’t change or even show up you’ll know the volume pot is no longer functional and will need to be replaced. The good news is that volume pots are inexpensive and need simply to be soldered.

CLEANING AND MAINTAINING YOUR SOLDERING IRON

Properly caring for your soldering iron will result in lower melt times, cleaner soldering jobs, and a significantly longer iron life. Cleaning and taking care of your soldering iron is rather easy and you’ll only need everyday household items.

Cleaning Supplies

The first thing you’ll need is a sponge, due to its ability to hold water. When you rub a hot soldering iron tip on a wet sponge the solder contracts at a different rate than the soldering iron, which helps to knock off any residual solder clinging to the iron’s tip. (This is why soldering stations include a sponge.) The sponge should be damp — not soaked.

The next thing you’ll need is six hundred-grit sandpaper, which you’ll use on the tip only if it’s been abused by the previous technician, student, co-worker, etc. Paper will catch fire at around four hundred fifty degrees, so be sure that the soldering iron has had time to cool and make sure the soldering iron or station is unplugged.

Tip tinner/cleaner isn't necessary if you have some extra solder, but it may be worth buying and using if you have a high-dollar soldering iron or station. Most of the time solder will work just as well, though.

Two Cleaning Scenarios

Let’s say someone has left you with a cold and dirty soldering iron, which is of course a common scenario in college electronics labs and a lot of workplaces. If and only if the iron is cool lightly scuff the iron’s tip with your six hundred-grit (or higher) sandpaper until the tip regains its luster — you’re just trying to remove the oxidation, not the metal.

If your soldering iron is dirty but still hot, you’ll need to set your iron aside and allow it to heat — a minute and a half is generally sufficient. Once the iron has heated you’ll notice brown deposits on the tip: this is rosin. Take your iron and flick the tip against the damp sponge. Don’t hold the sponge in your hand.

You’re almost finished.

Tip Tinning

Once you've cleaned the iron it’s a good idea to tin the soldering iron’s tip, which you’ll do in our case by lightly coating the entire iron’s tip with solder. The solder will act as a buffer zone that serves to protect the iron from oxidation.

Choose a low-temperature solder so that the iron cools fairly quickly — that way you won’t fry the solder to the tip, which would completely defeat the purpose of cleaning your soldering iron or soldering station. I won’t go into details regarding tinning here, but you’ll find a number of helpful tutorials elsewhere online.

Take care of your soldering iron or soldering station and it will work flawlessly for years to come.