Poorly maintained soldering iron tips have real costs associated with their lack of care. The replacement costs associated with failing soldering tips, as well as the negative impact on outgoing quality levels, are the two greatest costs related to poor tip management practices. A poorly maintained soldering tip can result in ineffective heat transfer, which means that a reliable intermetallic interconnection is difficult to ensure. To maintain the integrity of the soldering joints and prevent the tips from becoming a runaway consumable expense, there are several areas of tip care that can prolong their life.
Figure 1: An example of a degraded blade tip.
When to Replace the Tip
There are signals to the rework technician that a soldering tip is beginning to fail. If solder on the tip tends to “pool up” rather than flow across the tip, then surface oxidation may be going on in the tip. This will lead to a poor heat bridge and limited heat transfer. Another sign of oxidation buildup will be a drop in soldering performance. If it seems like the iron is just not getting hot enough, it could be that a thermal barrier of oxidation is preventing the tip from doing its job.
Another telltale sign is in the visual appearance of the surface of the tip, which should have a luster and shininess to its visual appearance. The soldering iron tip plating material should show that it is intact by not displaying any signs of pitting, holes, or cracks in the tip plating. All of these are signs that the tip needs a replacement.
Keeping the Tip Clean
One of the habits that rework technicians need to nurture is keeping the soldering tip clean. Clean tips will help ensure that they last longer and work most efficiently during their lifetime. Ideally, the tip should be cleaned frequently during use and after every shift. There are multiple methods for cleaning the soldering iron tip.
One technique is wiping the tip on a damp sponge wetted via distilled or DI water (to reduce any mineral buildup on the tip). Be sure to let the tip return to the set temperature between each of the wipes as the sponge will cool the tip. Change these sponges periodically so as not to re-contaminate the tip. As an alternative, brass wool can be used to gently scrub the iron plating on the tip without damaging it. Sandpaper and files should never be used to clean the tip of a soldering iron as this will damage the plating material and cause premature tip failure.
Most tip cleaners contain highly aggressive chemicals and should be avoided, as buildup can lead to blackening of the tips and oxidation of the plating. Due to the numerous heat cycles and the many different coatings, fluxes, epoxies, and other materials found in the rework area, cleaning may need to be on a more frequent basis compared to other areas of the manufacturing floor; thismaintains tip life and ensures solder joint integrity.
Once cleaned, one of the best ways to extend the life of your soldering iron tip is to apply solder so as to protect it from oxidation and premature failure. Tip tinning helps prevent oxidation, which hinders the tip from transferring heat effectively. Simply flood the tip with solder before putting it into the holder. This layer of solder works to protect and seal the iron plating from the air, thereby inhibiting oxidation. The other benefit to tip tinning is that it creates a heat bridge, which can effectively transfer the heat from the soldering iron to the pad as well as the component leads.
Storage and Handling
In addition to cleaning and tinning of the tip, their life can be extended through proper handling and storage. It is recommended that tips be stored in a container to limit the effects of oxidation, corrosion, and debris accumulation. Never bang or drop the tip, as this can cause damage to the plating or heating cartridge. Through proper storage and handling, tip life can be extended.
Understanding the Role of Flux
Tip plating can be eroded and altered by flux as activators found therein can damage the plating of the tip through a chemical reaction. More aggressive fluxes such as rosin-based or water-soluble fluxes can act more aggressively in wearing the tip plating away. It is not advised to dip your soldering iron tip into the flux as it could prematurely damage the plating. Instead, flux should be applied at the interconnection point of where the solder is applied at the pad/lead interface and never directly to the tip itself to protect tip life.
Figure 2: Chisel tip plating erosion.
Maintaining the Right Tip Temperature
Tip temperature has a big impact on the expected life of the soldering iron tip for a number of reasons. Fluxes and cleaning agents coming into contact with the soldering iron tip under increased temperature can accelerate the degradation of the tip coating. Oxidation of the tip increases under higher temperatures. Finally, the thermal stress on the tip increases with increased temperature, thereby inducing a greater rate of tip degradation.
In some soldering stations, the soldering iron can go into a “sleep” mode to increase tip life, which greatly reduces the temperature of the tip while it is not in use. By understanding the impact of temperature on tip life, rework technicians can prolong the life of their soldering iron tips.
By following these guidelines for soldering tip maintenance, more consistent and reliable hand soldering rework results can be obtained while reducing the consumable costs associated with the purchasing of many tips.
Bob Wettermann is the principal of BEST Inc., a contract rework and repair facility in Chicago. For more information, contact firstname.lastname@example.org.
This column originally appeared in the November 2020 issue of SMT007 Magazine.