Cross-sectional or X-ray analysis will offer a high level of confidence when trying to ascertain if soldered joints are acceptable. However, in reality, most applications will rely on visual inspection by a trained operative. Inspection criteria will include the degree of wetting, amount of solder, shape of the soldered joint and physical appearance.
For example, if there is too much solder on a joint, this could be a poor joint, i. It is difficult to inspect, and also increases the risk of solder bridges, which will result in a short circuit. In difficult applications where heavy oxidation is present, the integral flux may be insufficient to produce a good quality joint. In this case, additional flux may be required.
However, care should be taken to use a flux chemistry that is compatible with the solder wire and the amount applied should be kept to a minimum, especially if the assembly is to be cleaned at a later stage. As long as the solder alloy is the same, there is no problem mixing old solder with material that has been freshly applied.
Make sure that your soldering iron is set to the correct temperature, clean the soldering tip using a damp sponge or Tip Cleaning Wire and then apply a small amount of solder to the tip to aid thermal conductivity. Once you are happy with the quantity of solder wire applied, remove the solder wire shortly followed by the solder tip.
Solders are not mixed as this would create a new alloy whose electrical and mechanical properties could be compromised. The ultimate test of a soldered joint will always be the functionality of the unit produced. However, this is purely a snapshot of the joint integrity at that moment in time and does not give any indication of long term reliability.
Use clean DI water. Tap water may include minerals that can build-up on the tip. When you saturate the sponge, wring it out so that it is not dripping wet. Too much water can increase the thermal stress of the tip, and slow down tip recovery.
When the soldering tip has turned black from baked on fluxes and no longer wets properly, it is time for the cleaning tools of last resort. Tip tinner Plato TT is a combination of lead-free solder and cleaner. While the soldering iron is at full temperature, roll it in the tip tinner.
As you roll it, it should change from black to shiny silver as the baked flux is cleaned off. Then wipe off the excess tip tinner from the soldering tip, and re-tin using wire solder.
Polishing bars are also available and are used to scrub the tip clean of flux residues. This should only be used as a last resort because you will be removing iron along with the burnt flux.
Once a tip shows pitting - actual holes in the iron - it is time to be replaced. Remember to use a jabbing motion using a brass tip cleaner.
Wiping across the surface increases the likelihood of flinging molten solder. Since the move from lead to lead-free solders, a common complaint has been short tip life. The higher heat needed for lead-free solders and flux combined with greater activity leads to faster tip burn-out. Often the tips turn black, the solder beads and just drips off the end of the tip.
Soldering tips have a copper core that transfers heat from the heating element to the working end tip of the tip. Because copper is very soft and easily corroded and worn away, other metals are used to plate over the copper, including an outer layer of iron. Although iron is very hard, it will still corrode eventually.
In addition, it can be coated with flux and other soils, which can cause dewetting. Corrosion and dewetting will slow down soldering and eventually necessitate scrapping the tip. Although all tips will have their day in the trash bin, there are several steps an operator can take to increase tip life:. When leaving the solder station for anything over 5 minutes, turn it off. When you leave the station turned on, the tip remains at soldering temperature, further reducing tip life.
Modern soldering equipment heats up to a soldering temperature in seconds, so the time savings is not worth the reduction in tip life. Once there is pitting and visible corrosion, it is time for a new tip. The outside of a soldering tip is plated with iron over the thermally conductive copper center. This protects the soft, corrosion-prone copper from the harsh fluxes. Once flux gets through the iron plating through pits, the tip will be eaten away quickly. After all, the components have been replaced and excess solder removed….
This is an optional step for no-clean flux, but still a good idea for densely populated or high voltage boards. It is absolutely required, regardless of the flux type, if you plan to follow your repair with conformal coating. That concludes our Ultimate Guide to Electronic Soldering. Still have questions about which soldering products are best for your applications?
Contact us at , or send us a message here. Americas English Spanish. My account Login View Cart 0. What do I need to solder electronics? Wire solder, with or without a flux core. Flux, if the wire solder does not include a flux core or if additional flux is needed.
What is a soldering iron? What is the difference between a soldering iron and a soldering station? What type of solder should I use? Lead or lead-free — Solder is generally a combination of metals, which are chosen for the best reliability and conductivity.
Lead, often combined with tin, has been the mainstay of electronic soldering since its inception. Lead has a relatively low melting point and readily wets and flows, which makes the process faster, easier, and more fool-proof. Because of environmental and health concerns around, there has been pressure to move to lead-free solder, which is often a combination of tin and silver. Lead-free solders have a higher melting point and generally require more active or more concentrated fluxes higher solids content to achieve the same soldering performance as leaded solders.
For typical manual soldering, if done properly, reliability between lead and lead-free solders should be about the same. For high-end electronics used in extreme environments e. Wire for plumbing will be much thicker, 2mm in diameter or higher. Electronics solder wire will be thinner, from 1. Match the diameter to the size of the connectors and contacts you are soldering.
If the diameter of the wire solder is too small, you will be going through too much solder. Too large and it could be hard to maneuver around a dense PCB, thus increasing the chance of thermally stressing or even soldering other components that are unrelated to your repair. Flux core or solid wire — Most wire solder comes with a flux core, so the flux will automatically activate and flow over the soldering area when the solder is melted.
It is more convenient and efficient to work with. Solid wire can be used, with flux added by a brush, a bottle dispenser, or a pen dispenser. Unless a very specific flux is required that is not available as a wire solder core, flux core wire solder is generally recommended. Type of flux -- No-clean flux is a good choice for soldering where cleaning is to be avoided. Should I use lead or lead-free solder? What is flux? What type of flux should I use?
Do I need to add extra flux when soldering? Make sure the surfaces to be soldered are clean. Turn on the soldering iron and set temperature above the melting point of your solder. The idea is to bring both up to a soldering temperature at the same time. The size of the tip depends on the size of the component lead and the spacing between the tracks. The high-quality irons such as the soldering stations have adjustable temperature controls and various tip sizes, making them suitable for a variety of components and circuits.
There are various kinds of solders, differing in diameter, metal content, and type of flux. However, the lead-free solders have higher melting points than the lead-based. The lead-based solder is being phased out in favor of the lead-free due to the toxic nature of lead. In fact, new products containing lead are banned in some countries such as Europe and those under the European Union EU region. Recommended diameters range between 0. Thicker solders are used to make larger joints faster but are not suited for smaller joints because of the likelihood to create bridges between the closely spaced pad and pins.
The rosin core acts as a flux and prevents oxidation of the metals in addition to enhancing the wetting of the surfaces. Mixing the lead-free and lead-based solders cause cross-contamination which can lead to cracking of the joint, circuit instability, and sometimes non-compliant equipment.
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