Soldering/Useful tips

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Preparing a New Soldering Iron

  1. Screw on/in a new tip
  2. Heat the iron
  3. Soak the sponge on the soldering iron holder in water. It should be damp, not dripping.
  4. Remember to clean and dry the sponge when done
  5. If possible, use distilled water with the sponge.

"Tinning" the iron

  1. Dab solder onto the tip until the solder 'sticks.' Coat the tip evenly. Wipe off any excess on a damp sponge or rag.
  2. From time to time wipe the tip of the iron on the sponge to remove the dross and excess solder that accumulates during the soldering session. Re-tin as necessary.
  3. If you are using an adjustable base, adjust...

Renovating an Old Iron

Remove any residue on the tip

  • This can be done while the iron is cold or hot. Most soldering tips are plated with iron, filing will remove the iron plating and ruin the tip. Tips will wear out and become pitted with time anyway. The good news is that tips are almost always replaceable and relatively cheap.
  • A knife can also be used to scrape any dross that has accumulated on the tip.

Make sure the tip is firmly screwed in/on to the iron

  • Loosening, then tightening a tip will break any corrosion that has formed and may improve performance in the process. If the iron is hot, use a pair of pliers and keep your fingers away from the hot bits!

Re-tin the tip.

  • Heat the tip, then dab on fresh solder until the tip is shiny with molten solder.

From time to time while soldering, wipe the tip on the sponge to remove the dross (technical term is 'crud') that accumulates in the process

  • A tip cleaning device made from brass turnings is also useful. Electronics suppliers carry these and other accessories.
HowToSolder.SolderingIron.gif

How To Solder (Using an Iron)

As with all things, practice makes perfect.

Many become fustrated with their attempts as soldering. The usual suspects are an iron which is not suitable, or is not hot enough for the soldering task. Another common issue is old solder with weak flux. A third possibility is materials which are incompatible with soldering.

A better, hotter iron, with new solder or additional flux applied to the work go a long way to improving the results. Since modellers tend to solder copper and copper alloys, incompatible metals are unlikely.

Soldering Processes

Generally speaking, all types of soldering follow the same basic steps:

  1. Clean the parts being joined.
    1. Remove all coatings, paint, grease, oil, and dirt from the joint. Solder and flux do not clean the joint! Flux will remove corrosion from the metal, but that is it! The surfaces to be soldered should be clean and bright.
      1. Soldering feeds to weathered track can be difficult. The rails must be clean and all surface coating removed to bare metal. Flux will also be very useful in attaining a proper soldered joint.
  2. Physically mate the parts.
    1. The joint should be strong enough (if possible) to stay together without solder. Solder is not intended to provide a lot of mechanical strength!
  3. Stabilize the work so it cannot move during the soldering process.
    1. You will be pressing on the joint with the soldering iron, so it must be restrained. You can use a "third hand" rig, with alligator clips on swivel arms, you can prop it up or weight it down, or otherwise keep it from moving.
    2. If you will be using flux, this is the time to apply some onto the work.
    3. Heat the work, not the solder
      1. Make sure the iron is hot. Unwind a few inches of solder from the spool. Do not cut it, just unwind a bit! Tin, using fresh solder, the tip of the iron. Ensure sure the tip is 'shiny' with molten solder. You may need to first wipe the tip to clean off the dross, then add solder. The tinning process aids in heat transfer by using liquid solder to increase the surface area to improve heat transfer from the iron.
    4. Apply the iron to the joint. Make sure as much of the iron's surface (part of the reason for tinning the iron) as possible is touching the joint. Make sure BOTH parts of the joint are heated!
  4. Solder: Applied to the Work, Not the Iron!
    1. After a second or so of heating, apply solder to the work opposite the iron. If things go well, the solder will melt and flow into the joint. Keep adding solder to the joint until you see it 'surfacing' at the edges of the joint. A small amount of solder is all that is needed. Two seconds is about the maximum time you should need to complete this process.

If there is no wetting action or the solder will not melt and flow, there is a problem. Your iron may not be hot enough or corrosion prevents the solder from wetting and flowing into the joint. Clean the joint, apply flux, and try again.

    1. DO NOT apply solder to the iron; DO NOT push the solder around with the iron. The solder must melt and flow into the joint!
    2. Allow the solder to cool (freeze) by removing the heat source without disturbing the work. If the solder is still molten you may end up with a misaligned part or other issues.
      1. This is usually easy to see: the shiny, molten appearance of the solder turns more of a dull silver-gray.
    3. You can accelerate this cooling by gently pressing the tip of a small screwdriver to the joint. This works because the screwdriver is absorbing the energy, and as the screwdriver is heated, the solder is cools (faster than if the heat just dissipates into the air).

A commercial video (free for the downloading) showing how to solder turnouts using Fast Track brand jigs for PC-board tie turnouts is available at HandLaidTrack

The demonstrator has good technique but uses acid flux (not recommended) to good effect, and does show the problems of corrosion if the acid is NOT neutralized! The application of sandpaper and some elbow grease is very effective at preparing the copper for soldering. As noted above, the metal should be clean and bright.

On wire, where you will not be able to wash off the acid nor rinse with a baking soda solution, do NOT use Acid Flux! Despite comments to the contrary, you will not be able to entirely remove/deactivate the acid. With stranded wire, the acid will wick into the bundle and begin destroying the wire from the inside.

Also shown is an example of trying to solder on a dirty surface, with the solder 'beading up' and not flowing properly. Other examples show how solder should flow into a joint.

During the 'how to solder trackwork' demo the demonstrator does tell you to do one thing, but demonstrates a slightly different technique: he starts by holding the tip of the iron on the base of the rail, but after a second slides it so it touches both the rail and the PC board tie - necessary to heat both parts of the joint when there might be a slight gap between them. He does push the solder around a bit with the iron, but the joint is hot, the solder is liquid, and the solder flows into the joint, it does not lie on the surface!

The largest "Building Turnouts" video is 201 Megabytes, so guide yourself accordingly.

Tips on Soldering Different Things

Electrical Wires

  1. Since wires are covered with insulation, the first step is to strip 1/2 to 3/4 inch of insulation from each wire. Cleaning is not usually necessary, since the wire has been protected by the insulation. If possible, cut the first inch off the wire before stripping to eliminate any oxidation which may have occurred.
  2. Make a secure mechanical connection. There are several ways of joining the wires together:
    1. Line up the stripped ends together and twist them together. This is similar to preparing the ends for using a wire nut.
      HowToSolder.Twisted.gif
    2. Cross the stripped ends of two wires at 90 degrees, about half-way down the stripped end. Then wrap the free end of each wire around and around the remaining stripped portion of the -opposite- wire. This will result in a joint that is in line with the remaining lengths of the wires.
      HowToSolder.Electrical.StraightLine.gif
    3. Remove 3/4" of insulation from the center of a length of wire. Strip the end of the joining wire, then wrap the entire stripped end around and around the stripped center section. This results in a "T" shaped connection.
      HowToSolder.Electrical.Tee.gif
  3. Stabilize the joint so it won't move.
    1. In some cases, if the joint is mechanically secure enough, you can place tension on the wires with the soldering iron itself.
  4. Apply some flux, if needed. With older wires, flux can be the difference between successful and unsuccessful soldering.
    1. If you are having trouble getting the solder to flow, flux can really help.
  5. Heat the joint.
  6. Apply solder to the joint.
    1. Always apply solder opposite to the iron whenever possible.
  7. Allow the joint to cool without moving.

Mounting Rail on PC-Board Ties

A chisel tip works best. Clean the ties and the rail. Apply a small amount of flux. Position the iron so it can heat the rail and the tie. Tinning the iron beforehand allows the solder to form a bridge to conduct heat to the work. The flux should boil, then apply a little solder from the opposite side. It should melt and flow under the rail towards the heat source. Remove the iron and let the solder freeze.

Properly done, there should be a small amount of solder on either side of the rail, flowing up onto the base of the rail. The entire process should take no more than two seconds.

Adding Details to Brass Locomotives

The best method of doing this is using a resistance soldering rig. They are not cheap, but will make life a lot less stressful.

Resistance soldering uses the metal body, and the part to be soldered on, to complete the circuit. A lead is clipped onto the body. The part to be soldered is held with a tool that is connected to the resistance soldering system's power supply. When the part is positioned correctly, the circuit is completed and energy flows. The metal of the body and the part at the point gets hot quickly, and can be quickly soldered into place. Stopping the energy flow allows the solder to freeze and complete the bond.

For more information, see the American Beauty website here: American Beauty wesite

Soldering Rail Joiners to Improve Connectivity

This is easiest when done prior to installation, but not always possible. Soldering the joints improves conductivity and strengthens the mechanical joints. Curves laid with flex track are easier, smoother, and less stressful when the sections are soldered together prior to forming and installation.

Leave an unsoldered joint at intervals, with a slight gap, to allow for expansion and contraction of the track.

TrackJoint.jpg

Requirements:

  1. Flux
  2. Chisel tip iron
  3. Light gauge solder
  4. Assorted track laying tools

For soldering track, a chisel tip is best, as the rail will draw the heat out of the tip. The larger thermal mass of the chisel tip, and its area, will minimize this. If it takes too long to complete the operation, any plastic ties near the joint may melt or deform. Cold solder joints, or joints with excessive amounts of solder may also result.

Using a light gauge solder allows more precise control over the amount applied to the joint.

Flex track: trim away any ties, trim and file the rails square, and install the joiners. Then butt the second section against the first. If adjustments are needed, now is the time.

Once the two sections are mechanically aligned and connected, prepare the joint for soldering. Apply a small amount of rosin flux to the area of each joint, clean and tin the iron, apply the iron to the joint, and then touch the solder to the joint. The solder should flow and wick into the joint almost instantly. Remove the heat.

It may be easier to flip the track over and apply the heat to the bottom of the rails, directly on to the joiner.

Flextrack and Curves: leave, if possible, a straight section before finalizing the curve. It will be easier to trim, join, and solder. Once the joint is completed, continue to form the curve, adding additional sections as needed. Otherwise kinks and poorly butted joints can occur.

With previously installed track, apply rosin to the joints, touch a hot, tinned iron to the joint and add a little solder. Work from the outside of the rails, if possible.

For sectional track, soldering may be more difficult if the plastic ties surround the joint. A hot chisel tipped iron, flux, speed, and dexterity are the keys. Heatsinks should be used to prevent excessive heat from melting the plastic ties. Any metal device, such as alligator clips, that can be clipped onto the rails on either side of the joint should work. Damp paper towels also work. A narrow chisel tip may also improve access to the joint. Flux and a hot iron minimize the time needed to complete the joint, reducing the ties' exposure to heat.

After the joints have cooled, clean off any excess flux residue, and check for a smooth, proper joint. If there is excess solder, reheat the joint and draw off the excess. For a cold solder joint, reheat the joint to reflow the solder. Application of flux may also improve the joint during the reflow process.

Flux isn't a necessity, but it will make the task a lot easier and cleaner.

Adding Power Feeds to Track

Similar to soldering the joints, except you will be using a light gauge wire to connect the rail to your power bus This is usually done after the track is laid, from the bottom of the rail. When done in the gauge, care must be taken to avoid causing a lump which will touch the flanges and possibly derail the truck. The secret is to plan your attack so the wire is hidden as best as possible with as little evidence of the connection as possible.

Problem Solving

The first problem is old flux.

With rosin cored solders, you don't need additional flux, right?

Maybe. Over time, the lead in the solder reacts with the flux, reducing its effectiveness.

Not only does solder have a shelf life, so does flux. Over time they are not effective.

Another issue rarely discussed is poor quality solder. Always try to buy the best solder you can find. Quality solders are made with pure alloys, which means better performance. Lesser quality solders will have other metals in the alloy which alter its characteristics and performance.

  1. Quality Solder
  2. Solder which has not reached its expiry date
    1. Fresh flux is the antidote to this issue.
  3. Flux which has not expired
  4. Read the manufacturer's data sheets for their soldering products

Solder won't "Take;" Solder 'Beading Up' on the Surface

This is what wetting is. The solder will alloy with the metal and form a bond. If the solder will not wet, the result is solder which can be removed completely using a tool.

Oil, grease or dirt present
A dirty joint will usually cause smoking (i.e. overheated flux), darkening of the joint, and problems with solder flowing through the joint.
Desolder, clean up the parts, try again.
Material not be suitable for soldering with lead/tin solder (e.g. aluminium).
Aluminum won't solder with lead/tin solder

Joint is crystalline or grainy-looking; solder 'beading up' on the surface; solder does not appear to have 'wet' the joint.

These symptoms are generally classed as a "cold" solder joint.
Probable Cause 1 - The objects you wish to solder together have been moved before being allowed to cool
Probable Cause 2 - Not enough heat applied to allow solder to melt and flow into the joint via capillary action
Explanation 1 - Moving a solder joint before it freezes doesn't allow the solder to bond to the pieces being joined
Explanation 2 - The joint was not heated adequately due to a low wattage iron, inappropriate tip size or too large a joint
Sometimes re-heating the joint and adding more solder is sufficient; otherwise, desolder and clean up the parts, then try again. If the problem is due to a too-small iron or too-large parts, obtain a larger iron, soldering gun, or soldering torch to supply additional heat. Be careful of 'collateral damage;' i.e. melting of the surrounding materials. A soldering iron should be at least 60W, or use a temperature controlled station and increase the heat/change tips.
When solder changes from liquid to solid, it passes through a plastic state. That's when moving the joint ruins it. One solution is to use Eutectic solder. It has a slightly different tin/lead ratio (63/37 instead of 60/40). It goes rapidly from liquid to solid and spends almost no time in the plastic state. Therefore, moving the joint is much less of a problem. (BTW: If you ask for eutectic solder, the store clerk may not know what you're talking about. Just ask for 63/37.)

As a general rule, a joint can be remelted three times. After that, face the fact that the joint was not properly prepared. Remove all the solder and start over. You can remove solder with a solder sucker or solder wick. If the solder wick isn't working well, apply a little flux first to the wick.

Generally, as long as the joint is shiny you have a good joint. A dull colour indicates trouble. If you re-melt a joint and the colour goes dull then the solder has probably become oxidized.

Solder Forms a "Spike"

Probable Cause - Overheating the joint and/or the flux.
Flux can be burned away if heated too high
Desolder and clean the parts, then try again.

Large Blobs of Solder on Joint

Too much solder!
Although the main problem with too much solder is unsightly appearance, excess solder can cause short circuits if it connects things it's not supposed to, or blocks trains from running down the rails!
This is where the "solder sucker" comes into play. Make the solder sucker ready- if it is spring loaded, make it ready. If it's a squeeze syringe, squeeze it. Heat the joint until the solder turns shiny (melted). With careful coordination, press the tip of the solder sucker into the molten solder and let it go! Much of the solder should disappear into the tool. You may have to poke a stiff wire into the business end of a solder sucker to unclog it from time to time. Make sure there is sufficient solder remaining in the joint!

Strands of Wire not Embedded in Solder; Parts Loose

Not enough solder used.
Solder should surround all strands of wire; parts should be held firmly by the solder, sometimes re-heating the joint and adding more solder is sufficient; otherwise, desolder and clean up the parts, then try again.

To tin a wire, start in the middle, add a little solder and move the iron toward the insulation, then move toward the end. You should be able to identify strands of wire when properly done. Additional flux will improve the result.

Surrounding Objects Charred, Melted, or Damaged

Probable Cause - "Collateral Damage" due to soldering in too-tight quarters; poor control of business end of the iron.
  1. Iron is too hot, or tip is too large. Reduce temperature and/or replace the tip.
  2. Iron isn't hot enough, or tip is too small.
    1. If it is not hot enough to make the joint within two seconds, continued application of heat will allow the energy to travel further into the work (heatsink), possibly melting or damaging something. At the joint it doesn't get hot enough to melt solder effectively.
The soldering iron is HOT! Plastics will melt, other materials will char.
Be more careful in the future.
Make changes to the tip and temperature used to minimize the time needed to heat and solder the work.

Notice that many of the problems are fixed in the same way - "Desolder and clean up the parts, then try again." This does cure a lot of problems; soldering is generally a reversible process, except for a thin coating of solder on the parts (they are now 'tinned').