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Soldering Techniques





Safety notes
  1. Be sure to have a clean and uncluttered working environment.
  2. Always rest the soldering iron/ woodburning pen on the stand provided when not in use to avoid the heated tip coming into contact with other objects causing fire hazards.
  3. Do not touch any metal parts. Extreme high temperatures!
  4. Always let the soldering iron/ woodburning pen cool down naturally on the stand.
  5. Do not immerse in water!
  6. Do not dismantle the soldering iron/ woodburning pen.
  7. If the cord is damaged, it should be replaced by the manufacturer, or its service agent, or a similarly qualified technician.

Preparation of the joint to be soldered

  1. Be sure the material you are soldering is completely clean from dirt, grease, oxidation, etc. The surface must be scraped, sanded, or treated with flux, before applying solder.
  2. Solder does not stick to coated surfaces.
  3. When soldering electrical wire, separate the wires to be soldered and scrap them clean. Each section of the wire should be ¡§tinned¡¨ with a thin layer of solder and then twist the sections of wire together.

Soldering basic steps

To achieve good soldering, one must know the following basic steps in soldering:

  1. Hold the soldering iron like a pen, near the base of the handle. Imagine you are going to write your name! Remember to never touch the hot element or tip.
  2. Touch the soldering iron onto the joint to be made. Make sure it touches both the component lead and the track. Hold the tip there for a few seconds and...
  3. Feed a little solder onto the joint.
  4. It should flow smoothly onto the lead and track to form a volcano shape as shown in the diagram. Apply the solder to the joint, not the iron.
  5. Remove the solder, then the iron, while keeping the joint still.
  6. Allow the joint a few seconds to cool before you move the circuit board.
  7. Inspect the joint closely.

It should look shiny and have a 'volcano' type of shape (see image below for reference). If not, you will need to reheat it and feed in a little more solder. This time ensure that both the lead and track are heated fully before applying solder.



Cold Solder Joints

A cold joint is a joint in which the solder does not make good contact with the component lead or printed circuit board pad. Cold joints occur when the component lead or solder pad moves before the solder is completely cooled. Cold joints make a really bad electrical connection and can prevent your circuit from working.

Cold joints can be recognized by a characteristic grainy, dull gray colour, and can be easily fixed. This is done by first removing the old solder with a desoldering tool or simply by heating it up and flicking it off with the iron. Once the old solder is off, you can resolder the joint, making sure to keep it still as it cools.


Selection of tips

Choose the tip shape that can offer the maximum contact between the tip and the metals to be soldered. Having a large enough contact area can deliver just the right amount of power/heat to make a good soldering joint. A tip that is too large in contact area may damage the PCB. A tip that is too small in contact area may be too cold for making the joint. There are two major types of soldering tips:

  1. Nickel Plated Copper Tips
    These nickel-plated copper tips are economical soldering tips. Oxidation occurs on the surface of the tips easier during soldering. You may file away the oxidation.
  2. Iron Plated Long Life Tips
    Long life tips are iron-plated copper tips. They are much more durable than regular copper tips. They are pre-tinned at the tip by the manufacturer to allow easier wetting of solder to the tip. Never file a long life tip, as this will damage the plating of the tip.

Selection of solder

There are two major types of solder: regular tin/lead alloy solder and special lead-free solder. Solder usually comes in wire form and bar form.

  1. Solder bars are for industrial production line use.
  2. Solder wires are for DIY and repair maintenance use.

There are two types of solder wire: rosin-core and acid-core:

Always use a rosin-core solder for soldering electrical wiring or copper and tin flat metals.
Use acid-core solder only on galvanized iron and other hard-to-solder metals.

Special lead-free solder is an environmentally friendly product, and just like the name says it does not contain any lead.

Selection of wires

For wire links between points on the circuit board we recommend using Single core wire (see image below).


For wires to parts off the circuit board, including switches, relays, variable resistors and loudspeakers we recommend using Stranded wire (see image below). Do not use single core wire because this will break when it is repeatedly flexed.



Soldering-tip care
  1. Always "tin" the tip before, during, and after soldering to prevent the tip from oxidation. Oxidation of the tip will result in poor wetting of solder and hence affect the quality of the soldering joint.
  2. Do not feed solder wire directly to the tip surface. The flux inside the solder wire will speed up the oxidation of the tip.
  3. Occasionally, after the soldering iron is cooled down, remove the tip from the soldering iron to prevent the tip from "freezing".

The Solder-It Soldering Kit


There are times when a product comes along that I feel will be of special interest to our readers. The Solder-lt kit is just such an item. Over the years I have written several articles on soldering. I have seen numerous methods marketed that claimed to solder dissimilar metals, and none of these methods were really successful from my observations.

At Dayton last year, however, Fred Doob, AA8FQ, displayed a soldering kit that was truly amazing. In fact, amateurs were lined up to see and buy his product.

I approached Fred with the possibility of doing a product review for CQ, and he gave me a complete demonstration. I really felt this was something in which a lot of operators would be interested. Fred has been a representative selling products for the automobile industry. One automotive company had a very experienced metallurgist who came up with a soldering paste and material that had better bonding charateristics than normal solder and worked at lower temperatures. Fred saw the possibilities of this paste and solder for radio amateurs, so he put together a kit containing the necessary materials. Also, he designed a very small butane torch that can be used with a soldering tip or simply as a torch. The torch is refillable from one of the commonly available small butane bottles for cigarette lighters.

What will the Solder-lt kit do? Simply put a slight coating of the solder paste on the materials to be soldered. Then apply the torch flame so that the paste melts. Next apply the flame tip so the solder flows along the desired area.

There are four different tubes of paste provided: silver paste, copper paste, aluminum paste, and last, pot metal paste (that's right, pot metal paste).

Some technical points need to be included here.The aluminum solder paste will solder aluminum to other metals such as copper. It has a low melting point (395 degrees), and the resulting connection has a tensile strength of 28,000 PSI ! In fact, small solderlng jobs can be done with a match or lighter because of the low-temperature paste points. One problem with many antennas is that the manufacturers use self-tapping screws to hold elements together. These screws tend to become loose, creating noise problems Not so with the Solder-lt kit. Simply solder the screw in place. It's easy and quick and will hold as long as the element lasts.

One of my hobbies is making turquoise jewelry, and silver soldering is always a touchy proposition. Not so with the Solder-lt klt. You can solder at a point to hold a piece in place, then form the metal, and move along, soldering as you go. Coax fittings become very easy and simple to solder.

Frankly, as you can tell, I was extremely impressed with the kit. I don't expect it would eliminate normal circuit-board work, but for tough soldering chores it's the answer.

The Solder-lt kit comes complete with the pastes mentioned above, plus the torch and a soldering tip. Price of the kit is $59.00.




The Solder-It Kit (SPK-8) is our most popular item among hobbyists. It contains one each of our four Solder Pastes:

It also contains a Professional Grade Solderpro-70 Torch with a Catalytic (flameless) Soldering Tip, a Vinyl Storage Pouch, Removable Stand, Full Instructions and Warranty.

The Solder-It Kit will allow you to solder almost any metals as well as to join dissimilar metals like aluminum to copper, or brass to pot metal. Since all of our solder pastes flow at low temperature, you will be able to solder delicate pieces without distortion or in the case of electronics, without damaging insulation or delicate components. Similarly, for heavier work, you will not have to apply as much heat. Solder-It Pastes produce solder joints that are 5 to 10 times stronger than conventional solder. That is 5,000 to 28,000 psi depending on the metals you are joining. 

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