Soldering and Soldering Tools - How to Make a Durable Solder Joint
Making a good solder joint is not difficult. A little practice and proper tools are all you need.
We have compiled a selection of recommended, hobby-priced tools into one product:
Tools and soldering stations (edited 4/2024)
With the cheapest soldering iron, it's difficult to make good solder joints. If the goal is to solder a couple of wires or assemble one pedal kit, you can get by with a 20-30 € adjustable soldering iron. However, we can say directly: this is not a good iron.
With a soldering station costing just under 100 €, you can get much further. Their power and heating speed are usually enough for amplifier building as well. Really good (non-western manufacturers) soldering stations start from just over a hundred euros.
In January 2018, we added a batch of soldering stations from the Far East directly from a large factory. This makes the price-to-quality ratio really good. The features and ease of use are far better than hardware store stations, and yet the price is even sometimes cheaper.
Here is the link to the entire new range!
Especially recommended are models with the C245 handle. These offer excellent value for money and make it easy to make good solder joints.
Note: Older soldering irons without temperature control unfortunately do not work well with lead-free solders. The temperature is too low, and it is impossible to make good solder joints. Older adjustable soldering stations usually work fine with modern solders.
Soldering solder
We recommend using high-quality solder. With good solder, it is significantly easier to make good joints!
This is really important. We receive many support requests asking for tips on soldering when it doesn't seem to work. In the end, it often turns out that the solder is of automotive-grade quality, making it nearly impossible to make good solder joints. There is a clear reason for this: good solders contain 3-4% silver, and because silver is expensive, it is not present in cheap solders. Without silver, the melting temperature of the solder is higher, and soldering is more challenging. Cheap alloys are mainly intended for industrial use.
So when you buy lead-free solder, make sure that the alloy contains the text AG3 (or AG4). For example, Sn96,5Ag3Cu0,5. This means that it contains 3% silver (Ag). This alloy has the lowest melting temperature of the most common alloys, and it is easiest to get good joints even with hobby-grade tools.
For building pedals, 0.5–0.7 mm solder is suitable. For amplifiers, especially when using turret or eyelet boards, 1 mm solder is better.
Soldering Preparation
Ensure that the surfaces to be soldered are clean and free from oxidation. Clean them if necessary using IPA (isopropyl alcohol) and/or mechanically by sanding, filing, or scraping.
Choose the appropriate tip for your soldering iron based on the task. When soldering circuit boards, the tip should be small. However, avoid using a small tip for turret posts, as it cools too quickly when soldering large metal parts.
Set the soldering iron temperature appropriately. The maximum for leaded solder is 385 °C, with a suitable starting temperature around 330 °C. For lead-free solder, a starting temperature of 370 °C is ideal. Different soldering irons may vary in their temperature suitability, as cheaper models do not maintain the tip temperature as consistently. In such cases, a higher temperature is often necessary. Too high a temperature can damage components and dry out the solder. If soldering large metal parts (e.g., speaker connectors), increase the temperature to maximum if the soldering doesn’t succeed otherwise.
Ensure that the soldering iron tip is clean and tinned. Never clean the tip by sanding, as high-quality tips have a coating that must not be damaged. Use a steel wool pad or a damp sponge (not wet) for cleaning.
Soldering
- Apply a small amount of solder to the tip of the soldering iron.
Place the soldering iron at the connection point between the parts to be soldered, for example, when soldering a circuit board, at the base of the component lead on the surface of the board.
Feed the solder into the joint near the tip. Do not feed the solder directly onto the soldering iron tip.
When soldering circuit boards, usually a very small amount of solder is sufficient. For turret joints, more solder is needed. However, excessive solder is more often a problem than too little solder.
Once the solder has fully melted, hold the soldering iron in place for a moment, then remove the tip.
Do not move, blow on, or alter the solder joint while it cools. Blowing or moving the joint will most likely degrade the quality of the soldering.
Visually check that the solder joint is good. If the solder joint is unsuccessful, correct it by reheating the solder and adding a small amount of new solder.
Too long a heating time can damage sensitive components such as transistors and other semiconductors. Germanium components are particularly sensitive to excessive heat. Additionally, the traces on circuit boards may detach from excessive heat.
Signs of a Good Solder Joint
A high-quality solder joint is cone-shaped, with a smooth and shiny surface.
A poor-quality solder joint is often irregularly shaped, with a dull surface.
Melting Insulation - A Common Cause of Failures in DIY Devices
We deal daily with issues faced by kit builders. A common reason for a non-functional device relates to soldering. The problems usually aren't caused by the solder joints themselves, but rather by accidentally touching the wrong spots or melting insulation.
The soldering iron should never touch the component bodies! If you melt the side of a plastic film capacitor, it will almost certainly short-circuit! This is hard to believe, but it's true. Replace any components with even small signs of melting before powering up the device!
Another common issue occurs when soldering insulated cables. Excessive heat can melt the insulation on cables, creating a short circuit between the cable's protective sleeve and the hot internal conductor. This isn't always noticeable visually.
Be especially cautious when soldering shielded wires. Teflon-insulated cables help, but they are ten times more expensive than standard cables, so they are not always practical for every application.
PVC cable insulation melts with even the slightest touch. Although this may not immediately cause a functional issue, cables with signs of melting should be replaced immediately.
A frequent issue is the copper strands in cables that stick out uncontrollably. Cut off any exposed copper strands from the solder joint to prevent short circuits.
Soldering Iron Tip Maintenance
Always keep the tip clean. Before each solder joint and after each solder joint, clean the tip using either a steel wool pad or a damp sponge.
Never leave the soldering iron on for long periods when not in use. Always turn off the soldering iron when you're not using it. The easiest way to damage the tips is by leaving the iron on without using it for an extended period.
Soldering iron tips are reasonably priced these days, so it is wise to keep at least one spare tip on hand.