This guide is intended for beginner/intermediate level solderers (although I will cover some advanced topics at the end). Since soldering is part art and part science you will find that everyone has their own personal technique and equipment preferences. The solutions I present here will provide the fastest/easiest/safest way to get good results, and over time as your skill level improves you can adapt the techniques to what works best for you.

I will break the information into three categories; basic, intermediate and advanced. The basic category will cover playfield work, like replacing a diode, lamp or solenoid, the intermediate category will focus on board repair and the advanced category will cover specific advanced board repair techniques like through-hole repair.

In part 1 we'll discuss soldering/desoldering equipment. In part 2 I'll cover basic (playfield) soldering/desoldering, in part 3 intermediate soldering/desoldering (circuit board), in part 4 advanced board repair techniques.

The most important thing to know when looking at soldering equipment is that it is not like a wrench set, for example. While a cheap wrench set from Harbor Freight will perform the same as an expensive set, at least initially, there is a vast performance difference between cheap soldering equipment and quality products. On the other hand, beginner/intermediate level solderers aren't going to spend several hundred to a few thousand dollars on JBC, Pace or Metcal so I've attempted to provide high performance, but cost-effective solutions.

In the image below you can see the difference in actual temperature at the joint of the Hakko FX-600, with improved tips, versus their older 933 model. In both cases the iron is set for 350°C, yet the FX-600 averages about 280°C at the joint and the 933 about 250°C. The difference is much larger when comparing a good iron to a cheap one.

Hakko-FX-600-Performance.jpg

Cheap soldering equipment is the number one cause of frustration when people are learning how to solder, so spend the extra money and buy quality tools.

Soldering Irons

Even if you plan on moving on to board repair I would still suggest you purchase a soldering iron since they are a lot easier to use when working under the playfield. You want a 25 watt iron--nothing higher is needed--from a quality manufacturer like Weller or Hakko. The tip is as important as the iron, and this is where those $20 soldering irons really cut corners (tips will be covered in-depth in a later post).

The Weller WP25 Professional costs slightly over $40 on Amazon. It comes with a .125" screwdriver tip (ST3), although I prefer the ST4 tip (.187" screwdriver) since it provides better performance for basic soldering tasks. The additional tip will cost you about $8 on Amazon.

amazon.com link »

Hakko has discontinued their 25 watt iron that competed with the Weller Pro. They instead now offer a couple of very slick adjustable temperature irons ( FX-600 and FX-601) at a good price (around $70). Both heat up faster and have a faster recovery time than the Weller Pro. My only complaint is the temperature setting on both is in Celsius.

The FX-600 has a temperature range of 392 to 932°F and the FX-601 392 to 1004°F. The FX-600 comes with a conical tip so I suggest you add a .2" chisel tip (T18-S3). The good news is these are the same tips the Hakko FX-888D uses (my recommended temperature controlled soldering station). The FX-601 comes with a .2" screwdriver tip (T19-D5) which is a high thermal capacity tip.

Hakko-FX-600.jpg

I prefer the FX-600, but some will find the FX-601 easier to work with on playfield soldering since it has a larger heat capacity. Although either could be used for board work in a pinch (the FX-600 the better choice of the two), a temperature controlled soldering station is the recommended solution.

amazon.com link »

amazon.com link »

Soldering Stations

The first thing you need for intermediate soldering is a good temperature controlled soldering station. Wattage type irons tend to be too hot (after sitting for a while) or too cold (if you solder several joints in a row or the iron can't keep up with the heat dissipation). This is because the wattage is fixed and cannot respond to increased demand. The temperature controlled stations overcome these problems plus you can fine tune the temperature to the job, the tip being used and your personal preferences.

While the FX-600/601 soldering irons are temperature controlled they do not have the performance of a soldering station. While we're on that topic let's discuss what makes a good soldering station. Three key factors affect the performance of a soldering station: temperature accuracy (how close the actual temperature is to the set temperature), temperature stability (how much the temperature swings above and below the set temperature while at rest) and thermal recovery (how fast the tip comes back to temperature when applied to a joint).

There are other performance issues directly related to the tip and those will be discussed further on in the thread.

As you look at different soldering stations the first thing you will notice is that cheaper models don't provide any performance data on their product--I presume you can figure out why. So once again you want to go with a quality brand like Weller or Hakko (of course there are other very high-quality brands on the market, but they are much more expensive). I will note though that at the moment Hakko appears to be leading in regards to tip engineering and manufacturing.

One of the dead give-aways on a cheap soldering station (or iron) is that it is not ESD (electro-static discharge) certified. ESD certified products will have a 3-prong AC plug and the soldering tip will be connected to ground. This is an important issue when working on static sensitive devices.

There are two products that I would recommend, with the main differences being price and some minor features. The Weller WESD51 Digital Station costs about $130 on Amazon and the Hakko FX-888D Soldering Station sells for about $90. Hakko also offers a package with the FX-888D and 5 extra tips for about $130 on Amazon. I'll be honest, I like the Hakko products, but either one will get the job done.

Hakko-888D.jpg

Note: There is a group buy post on Pinside for the Hakko FX-888D.

Pinside 888D Group Buy

amazon.com link »

amazon.com link »

amazon.com link »

In addition to the soldering station and the included tip you will want to purchase some additional tips. In fact tips are the magic that makes one companies product better, or worse, than another. Companies like Weller, Hakko, Metcal and a few others spend millions of dollars each year in R&D attempting to design a better tip. More importantly though, manufacturing a quality tip is not easy, and cannot be replicated by the low cost companies.

I would also get the rubber cleaner option (B3474).

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Soldering Station Tips

Any high quality soldering station will use tips which consist of four layers. The inner layer of the tip is copper for heat conduction and next is iron, which is the workhorse of the tip. Next out is nickel which is non-wetting, meaning it won't wick the solder away from the tip's working surface. The last layer, chrome, is applied as an additional protective layer.

Since I stole (Oops... I mean borrowed--or actually I mean rented) Weller's graphic, I'll leave their name on the image.

Soldering-Iron-Tip.png

When selecting a tip you need to consider both shape and size. Many soldering irons come with a conical tip which is just about worthless (IMHO) because it doesn't provide enough surface area for good heat conduction. A much better choice for basic or intermediate soldering is a chisel, or screwdriver, tip.

When sizing a tip, the general rule of thumb is the tip should be roughly the size of the circuit pad. This provides the best combination of tip efficiency (temperature drop, heat transfer, working time and heat storage capacity--see the article below for more info, and don't miss the link to the second page at the bottom) and minimizing potential damage to the board.

Hakko Tip Selection Guide

I typically use chisel tips in the following sizes: .0625", .125" and .187-.200". The smallest tip is for IC's (it won't bridge the gap between leads) and small transistors. The next tip is for larger (driver) transistors and the last is for bridge rectifiers and under-playfield work. You should always size the tip to the job to provide optimum surface contact, good temperature control and avoid overheating sensitive components or traces.

Here's links for the additional tips for the Hakko 888 (it comes with the .0625"). This is the same company that offers the Pinside group buy. The first and second links are both .125" tips, but the second is a high-capacity (temperature) as designated by the L. Either is fine, but the second does work a little better on large components and/or large traces. The .205" tip in the third link is also a high-capacity tip.

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Hakko .125" Tip
Hakko .125" High Capacity Tip
Hakko .205" Tip

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Note: Most soldering stations require re-calibration when tips are changed.

For the technical geeks here's a couple of interesting articles. The first covers everything you'll ever want to know about tips and compares the Hakko and Metcal tips. The second covers the performance characteristics of soldering iron tips (in this case Weller, but the theory applies to all brands).

Stratesys Group Under the Plating

Soldering Iron Tip Performance Analysis

Tip Maintenance

You will need a couple of products to properly maintain your soldering tips. The main concern in tip care is oxidation, which reduces the ability of the tip to transfer heat to the joint. Oxidation is the result of oxygen and the rate of oxidation is increased by heat. It is easier to prevent oxidation than to remove it so some basic preventive care will ensure your tips stay in good shape.

1. Never use an abrasive to clean the tip.
2. Turn the soldering iron/station off when not in use.
3. While soldering, frequently clean the tip using a copper wire sponge (see image below).
4. Tin the tip with a small amount of solder when placed in the stand.
5. Use a wet sponge to clean the tip and apply solder at the end of the day.

In the following image you can see how much oxidation will occur on a brand new tip after being left on for 30 minutes.

Tip-Oxidation.gif

In the old days a damp sponge would have been used to clean the tip while soldering, but due to the thermal shock applied to the tip, a copper wire sponge is now the preferred method. The copper is softer than the tip, but harder than the oxidation so it will safely clean the tip. Hakko recommends that at the end of the soldering session you clean the tip using a sponge and the following procedure.

1. lower the temperature to 482° F (soldering stations and adjustable temperature irons).
2. Clean the tip with the damp sponge and inspect the tip.
3. If there is any black oxide on the tip, apply solder with flux and clean again. Repeat until no oxidation remains.
4. Tin the tip with solder.

You will want to use some type of stand for your soldering iron and Hakko sells one that includes the copper wire sponge. You will also want to add the rubber cleaner (B3474).

FH800-1.jpg

Since about 2006 manufacturers have tinned their tips with lead-free solder. Since lead-free solder will oxidize faster, the first thing you should do with all new tips is flush them with lead solder.

Solder

Solder tends to be a religious issue, with everyone having their favorite. I exclusively use Henkel Multicore 63/37 leaded rosin core solder. That doesn't mean it's better than other choices, just that I'm used to how it flows, so why change. Equally important to the brand is the type of solder you use, so let's talk about solder.

The first issue I'll address is lead solder vs lead-free solder. The Restriction of Hazardous Substances (RoHS) directive requires manufacturers to use lead-free solder (technically almost lead-free). Unfortunately there are some downsides to lead-free solder.

It requires higher soldering temperatures, you need to add a lot of additional flux, it is brittle and does not have the same visual clues that identify a good solder joint. Obviously in a high vibration environment like pinball, brittle is not a good thing, nor is higher soldering temperatures on a 20 some year-old board. The only, slight, advantage lead-free solder has is safety, but when a few simple rules are followed there are no great safety risks with lead solder. See the following article for more information on lead-free solder.

Lead Free Solder Disadvantages

Manufacturers have been working hard to identify other mixtures that will equal the performance of lead solder, and until they do I'll stick with my leaded.

The next choice is whether you want to use 60/40 Sn/Pb (Tin/Lead) or 63/37 Sn/Pb. The former melts between 361° and 374° while the latter is eutectic since it has a single melting point of 361°. There is some advantage to the latter although it is more expensive.

Solder contains an inner core of flux which cleans the joint and helps the solder flow better. The flux can be either rosin or water-soluble (commonly called no-clean). The former turns acidic when heated so it needs to be removed with a flux cleaner or naptha/alcohol after soldering. While technically the no-clean does not have to be removed, solder joints will look more professional (and be easier to inspect) with any leftover flux removed.

The problem with the no-clean fluxes is that they don't clean the joint as well as the rosin core and are actually harder to clean up afterwards. Personally I stick with solder that uses rosin core flux.

The last, and most common mistake I see, is choosing the proper diameter of solder for a specific job. If the diameter is too small it takes forever to feed enough solder to a large joint (coil, for example) and if the diameter is too large it's difficult to flow the solder properly on a small joint (board repair, for example) and not end up with solder blobs. The DoD recommends .031 to .063 diameter solder. I use .031 for circuit board work and .040 - .060 diameter for solenoids, wiring, etc.

As mentioned earlier, I prefer Henkel's Multicore solder. It has 5 strands of flux instead of one and (IMHO) flows better than single core solder. It is more expensive though and a quality single core like the one from Kester or MG Chemicals is an acceptable replacement. Bottom line you want a good quality lead solder with a rosin core flux and a couple of different diameters (one for playfield work and one for board work).

henkel-multicore-solder.jpg

Flux

There are times you will need additional flux in addition to what is provided by the solder. If a joint is heavily oxidized, or you're having trouble getting the solder to flow, adding a little more flux can help. Always use a rosin type flux, since it cleans better, and then use a flux remover (MG Chemicals, for example) or naptha/alcohol. I have the best luck with hitting it with the flux remover and a toothbrush and then finishing up with naptha/alcohol and cotton swabs.

Note: Naptha works better than alcohol, but you can't get it easily in California so that's why I'm including the alcohol option.

More importantly though is you need flux when desoldering. Think about it, solder has flux in it yet at that point in the process the joint should be relatively clean (since it was protected from oxidation by the solder you just removed). On the other hand, the joint is most oxidized at the point where you are desoldering so why would you not add flux to the mix? I'll discuss flux more once we get into soldering/desoldering, but it really is your best friend and is under-utilized by most people.

Other than quality (I recommend DeoxIT, Kester or MG Chemicals) the main difference in solder flux is the application method. I use a paste that comes in a syringe, but other choices include a rub-on applicator, liquid or a paste you apply with a brush. While the syringe is the most expensive solution, it is also the easiest to work with, and you can solve the cost issue by refilling it with flux paste.

Desoldering Equipment

If you get anything out of this post it should be that more than 90% of the damage done to circuit boards happens during the desoldering phase. This is not the area to pinch penny's or cut corners.

For basic desoldering you can get by with solder wick or a solder-sucker. Yes, I can hear the groans when I mention solder wick. The problem is that even the solder wick from quality manufacturers does not have enough flux in it. Take your solder wick and add a stripe of flux down the side you'll be applying to the joint and give it a try (or you can dip it in a liquid flux). You'll find that it works dramatically better and there are cases, like when you're cleaning up through-holes or pads after desoldering, that a good solder wick is the proper tool for the job. A width of .1" to .2" is a good choice for the solder wick.

Desoldering-Tools.jpg

I'm going to cover three additional tools for basic desoldering, only one of which needs to be in your toolkit. They are a solder bulb, a solder-sucker and the 45 watt Radio Shack desoldering iron. The only reason I even mention the Radio Shack product is because I've seen a lot of people using it.

Radio-Shack-Desoldering-Iron.jpg

I've never found the solder bulb to work very well, and prefer the solder sucker. I suggest the shorter type solder sucker (approximately 6" rather than 8 or 9") since it's easier to manage one-handed. Pick up some extra tips since you they will need replacement every so often. Many times it is easiest to use the solder sucker to remove the majority of solder and then use solder wick for final clean-up. On the other hand, if you use my tip above, solder wick works pretty well for the whole process.

While the Radio Shack 45 watt desoldering iron seems like a good idea, it runs way too hot for circuit board repair and in my opinion doesn't provide any advantage over a solder sucker for playfield work. In fact it's kind of unwieldy under the playfield. You do risk lifting pads and destroying through-holes with the Radio Shack product. If you're not interested in buying a desoldering station or desoldering gun, I'll cover how to safely do board work with a solder sucker in the intermediate desoldering post.

I would have previously recommended the Hakko 808 for circuit board repair, but it has been replaced by the FR300. When used properly, either will almost guarantee you will never lift a trace or circuit pad again, and desoldering IC's will actually become fun. While the FR300 has some advantages over the Hakko 808 it does cost quite a bit more so if you're on a budget I would consider trying to pick up the latter used.

Although it costs more, the FR-300 has a better pump, an on/off button, led heating indicator and a new style tip, which you can change while hot. The ceramic filter is in a better location and the temperature adjustment is much a better design.

Hakko FR-300 Features

While still in manufacturing the Hakko 808 Desoldering Kit cost around $190. The FR300 Desoldering Kit will run you around $270. Personally I think they kind of over-priced themselves on the FR300, but it really doesn't have any competition (unless you go to clones, which I avoid due to performance and reliability differences).

Hakko-FR300.jpg

The FR300 has a built-in vacuum pump and the tip has a hole in the middle that fits over the component lead and provides the vacuum pressure when the trigger is depressed. There are four temperature settings ranging from 662° to 932°.

The product comes with a 1mm tip which is fine for IC"s, resistors and such, but you should also purchase the 1.6mm tip for components with larger leads like TIP36 transistors. Pick up some extra ceramic filters while you're at it and a cleaning pin and drill for the 1.6mm tip. I would consider the 1.3mm tip an optional purchase, it works well in some cases (for example, .156 header pins), but you can get by without it.

The tip size should roughly be the same size as the pad you are desoldering, but not much larger. The gun should be re-calibrated after changing nozzles.

There's a group buy on Pinside for the FR300

Pinside Hakko FR-300 Group Buy

One last thing you will need is a fiberglass pen, which is used to mechanically clean joints before desoldering.

Fiberglass-Pen.jpg

FR300 Maintenance

I cannot stress how important it is to clean and maintain the FR300. It will dramatically affect the performance when desoldering and will prolong the life of the gun. Cleaning should be done periodically during each desoldering session and a more thorough cleaning at the end of the session.

During a desoldering session you should frequently clean the tip on a copper sponge. In addition, every time I put the FR300 on it's stand during a session I run the cleaning pin through the nozzle.

At the end of the session, while the gun is still hot, I do the following. Run the cleaning pin through the nozzle and use the tip cleaning drill if necessary--if you're properly maintaining the gun you will not typically need to use the drill.

Tin the tip with solder and then remove the heating element cover using the nozzle changing tool--be aware the tip is very hot and is not held by the nozzle changing tool so it will fall out when you remove the cover. Clean the heating core with the heating element pin (looks kind of like a long flat-tip screwdriver) or a heating element drill (not included with the FR300). Be careful during this procedure since the area you're working on is very hot. Repeat until the pin or drill passes easily through the heating core. Reassemble everything.

Do not skip cleaning the heating core just because the nozzle cleaning pin will pass through it. The core will get a build-up of flux and the larger diameter heating element pin/drill is required to clean it out properly.

Once the gun has cooled you can remove the filter pipe and disassemble it. You can do this part with the gun on, but it's really not necessary. Remove any solder from the pre-filter (it will chip off even if cooled) and inspect the ceramic filter. If the ceramic filter is stained or vacuum power has decreased, replace it. Tap the pipe on the table to remove any stray solder and then run a paper towel through it. If you're using flux, you can clean out the sticky residue with alcohol and cotton swabs.

During long soldering sessions you will need to clean the filter pipe assembly more frequently. You can do this carefully with the gun on. Solder build-up on the pre-filter is the leading indicator that it's time to clean the filter pipe assembly.

Dissasemble and clean the pump assembly once a week/month, depending on usage.

Hakko-FR300-Cleaning-1.png

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If you have a Hakko 808, the same schedule is recommended although there are some minor differences in product design. Reference the manual for additional information.

Other Equipment

Last, but not least, are some other tools that will make soldering/desoldering much easier.

Although you will most likely only use two of them, a set of solder picks should be in your toolkit. The two you will use are the one with the slot for bending leads and desoldering components/wires and the pointed one for cleaning out through-holes (personally I just use a toothpick for this).

Solder-Picks.jpeg

One of my most used soldering tools is an orangewood stick (also called a spudger). They are high temperature, do not conduct heat away from the joint and will not scratch components/traces/etc. They work well for positioning wires/leads while soldering and wiggling chip leads while heating to break that last little bit of solder loose (I'll cover this technique later). This is one of those tools that once you have one you'll find a dozen uses for it.

amazon.com link »

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The next thing you'll need is a good pair of side cutters. Buy the ones with long, narrow blades (as shown below) so you can get between the leads on an IC.

amazon.com link »

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Kapton (Polyimide) is a heat-resistant tape and does not leave behind a sticky residue when removed. Use it to hold pop bumper leads or a jumper wire in place and then remove it when you're done. If you've never tried it before, you will be amazed how much easier it makes some tasks.

amazon.com link »

Polymide-Tape.jpg

For those who prefer using a board clamp there are a few choices. Firstly, I will say I've never found the third-hand board clamps with alligator clips to be of much use.

Although I seldom have need of a board clamp, when I do have a 2x4 with a shallow, narrow (barely wider than the board) slot cut in it. Some boards will work better than others depending on component placement and in some cases you will need to route out some additional space for connectors.

For a professional solution I would recommend the Panavise 333, and then add a longer crossbar (see following link) so you can hold larger boards. The entire setup will cost you about $90 (Panavise makes excellent products though so it will last a lifetime).

Panavise 333

Panavise-333.jpg

Plastic locking hemostats work well for adding tension to a wire when soldering playfield parts. After you've got a good physical connection on the coil lug, for example, just go back a few inches on the wire (the hemostats are not heat resistant) and clamp the wire to another wire or playfield part. They also work well for restoration projects.

Plastic-Hemostat.jpg

Another good option for holding playfield wires is the old-style wooden clothespins. While they're not completely heat-resistant you can get them fairly close to the solder joint.

You will absolutely need some type of magnifier for inspecting solder joints on circuit boards. I use the type that fits over your head (and yes I look like a dork), but you can go with whatever type works for you (handheld, table, etc.). Keep in mind that as with soldering equipment when it comes to optics you get what you pay for (up to a point).

Lab-Magnifier.jpg

Safety

First let's talk about lead solder. Like most things that can be dangerous the actual risk tends to get overblown. Lead is not absorbed directly though the skin, but it can enter through cuts, tear ducts, nostrils or sucking your thumb. To avoid exposure you can either wear some thin surgical gloves or wash your hands when you're done soldering.

Funny story, 40 years ago when I went through training they taught us to use our mouth as a third hand to hold the solder.

The bigger health concern (from a likely to happen point of view) is vapor from the flux (there is no lead in the vapor, unless you crank the temperature up over 850°). I just use a small box fan to blow the vapor away from me towards my girlfriends cat. If you like cats, you might consider a smoke absorber like the Hakko FA-400 (about $70).

NOTE: This is an inexpensive, decent solution but would not be acceptable in a production environment. If you do a lot of soldering you should go with a fume extraction system.

Hakko-FA-400.jpg

It's also a good idea to wear protective eye wear while soldering.

Note: This advice is for healthy hobbyists with limited exposure to lead solder and flux vapor, not people who solder eight hours a day for a living or have other illnesses.

Good question. Although it's a simple question that can quickly get complex, and get a lot of differing opinions. The simple answer is if you are working on highly static sensitive boards or in a high-static environment then you need more advanced precautions. If not, then some basic steps should do.

Compared to other boards I've worked on, pinball boards would be on the low end as far as static sensitivity. As far as environment, part of that is the locale, part of it is the weather (season) and part of it is the flooring in your house (specifically carpet is the problem). So if you're in a high-static environment I would lean towards an ESD mat and wrist strap.

I'm not in a high-static environment and while I do use an ESD mat (mostly a holdover from when I lived in Chicago) I could easily get by with just a wrist strap. Of course , as mentioned before, all of your soldering equipment should be ESD rated.

Here's a mat that is intended for soldering environments. Note: It will not stand up to a soldering iron but will be OK with solder splashes.

http://www.globalindustrial.com/p/work-benches/components/mats/2-x-4-anti-static-mat

Basic Soldering

Now, on to the fun stuff. Actually that's just a tease since first we need to talk about the appearance of solder joints.

Appearance

When I went through training on soldering I was told, "If it looks like shit, it is shit." There is no way around it, if a solder joint looks bad there is a good chance that it is bad. A good solder fillet (the fillet is the solder portion of the joint) should be shiny (a dull solder fillet is an indication of a cold joint--meaning the solder did not adhere properly to the joint), smooth and have no pits, sharp edges or deep gouges. It should have just the right amount of solder, and not too much.

Solder-Joints.jpg

One of my pet peeves is people not cleaning off the flux after soldering. Not only is it unsightly, but it tells me they didn't inspect the joint after soldering it since the flux residue kind of gets in the way of doing this. So rule number one, always inspect your solder joints. If they look good then you can feel comfortable that you've got a good connection that will last for years.