Table of Contents:1.1 About 1.2 Why Use Flux? 1.3 Inspecting the Flux 1.4 Using the Flux 1.5 What Tools to Use 1.6 How Much to Apply 1.7 Common Applications 1.8 Maintenance 1.9 Safety Precautions 2.0 Downloads 2.1 Media and Reviews 2.2 Frequently Asked Questions (FAQs)
About:SRA #135 is a petrolatum-based soldering flux, containing Rosin and organic acid activator. Unlike many paste fluxes, it contains NO Zinc Chloride or Ammonium Chloride, making it ideal for electrical and electronic repairs. The Rosin also leaves a protective coating over the soldered area that can prevent corrosion.
- Ideal for electrical and PCB repairs
- Does not need to be cleaned
- Contains 2 ounces (56.6 grams) in a “Hockey Puck” jar
- Type RA (Rosin-Activated) Flux
- Active Temperature Range is 93 – 315°C / 200 – 600°
- SKU: FLS135
- Dimensions: 2.5″ Dia x 1″ H (64 x 25.5 mm)
- Weight: 2.5 Oz (70.8g)
Why use Flux?Flux is necessary to form a proper electrical connection because solder CANNOT bond without it. Soldering without a good flux is like trying to put a new registration label onto your license plate without first wiping off the layer of dirt and grime that has accrued on your license plate since last year. The surface needs to be clean so the adhesives on the label can do their job. If you want your solder to be able to do its job, you need to first remove the layer of oxide that has gathered on the surface of the metal you’re trying to solder. A good flux, like #135, removes the oxides and sets the stage for the solder. The solder follows the flux, as if the flux were clearing a path for the solder and telling it where it to go. For many soldering applications, using only flux-core solder wire is sufficient. However, there are some distinct benefits of adding an externally applied flux such as the #135 paste. These benefits include:
- More control over where the solder will travel – Wherever you apply the flux, the solder will flow to.
- Expedites the soldering process – It takes less heat and time to get the solder to flow where you need it.
- Results in a stronger connection – The flux allows the solder to bond properly throughout the target area.
- Protects the solder joint – This rosin paste not have to be cleaned off after soldering and the residue actually provides a protective coating from corrosion.
Inspecting the Flux:Open the #135 Flux “puck” container by turning the lid and lifting off. The SRA #135 flux is an amber colored paste. The consistency of the flux should not be gooey or hard to puncture. In other words it should be solid but also easy to dip wires and applicators into. If you see crystallization (rosin hardening) at the surface of the flux this is absolutely normal and NOT an indication of expired or tampered with flux.
More Information about Rosin Hardening:
The patterns and crystallization effect at the surface appear because of the way the acid activators and Rosin/Petrolatum solidify together during manufacturing. There can be variations on the appearance of the crystals, which are caused by the levels of temperature used during manufacturing, as well as ambient temperature. In addition, Rosin is a natural-derived product that varies in color, and this can also affect the appearance of the crystals. The crystals do not negatively affect performance.
Using the Flux:As noted in the previous section, flux is self-cleaning in that its job is to dissolve oxidation. However, it is recommend to clean surfaces to be soldered prior for the best results. If your parts are heavily corroded than this will be necessary. Prep the surfaces by removing any dirt, rust, grease, paint, and other contaminants with sandpaper, wire brush, steel wool, etc. For many applications, the residues can be removed with just a rag and some isopropyl alcohol. These impurities may prevent solder flow so it is important not to proceed until clean metal is visible. For very critical applications follow these steps to ensure a proper cleaning.
- De-grease with an organic solvent
- Rinse in hot water containing 2% hydrochloric acid (HCI) solution.
- Use as many hot deionized water rinses as necessary