How to Use Flux When Soldering Electronics: A Detailed Manual for Beginners
How to Use Flux When Soldering Electronics: A Detailed Manual for Beginners
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Let’s admit it – sometimes solder is just not solid enough to bond two parts, especially when you work with wires and electronics. A solder-based solution will surely affect in a poorly made joint with bridged pins or no joints at all. That is when a flux agent is picked. After setting the proper temperature level and flux, even a soldering beginner can cope with this common problem during any works with electronics.

How to Use Flux When Soldering

To avoid oxidation that keeps the metallurgical bond from the building, special flux agents are picked. The agent stays on the metallic surface when a person uses a soldering iron tool. The whole process goes on without too many oxides. Two surfaces form a solid and even bond.

The best types of flux for soldering electronics

However, it isn’t enough to take any flux agent to solder wires and electronics. As an owner of SolderingIronGuide, I went through many similar jobs. So, I can say for sure what flux agents to pick and what to avoid when you require to form a metallurgic joint.

What flux agents you must buy:

  1. Any leaded solder based on rosin cores is the best pick for electronic works. It dissolves better at low levels of temperature, compared to other types. And it’s better for a quite delicate wiring project. Using soldering flux with a slim rosin layer in the midst will help to cover the wires in the best way possible;
  2. Leaded solders with a solid core are also good. Such products oxidize easier and hold a strong bond much longer. Make sure to wash your hands when working with any leaded solder;
  3. Rosin flux products are based on refined pinesap. Some producers combine different rosin fluxes to deliver the greatest performance of their flux agents. Such products flow smoothly (when hot) and they remove oxides faster. When rosin flux is liquid it is acid, but when cooling down it gets more solid. That’s why consider eliminating the leftovers of rosin flux agents from a PCB as soon as possible, by means of alcohol;
  4. Water-soluble or organic acid flux products. Lactic, citric and stearic acids combined with water and isopropyl alcohol are also quite effective for the use of electronics. Mainly, because they’re more powerful than rosin-based fluxes. It’s easier to clean PCBs after the use of organic flux agents. These products are electrically conductive and provide better performance rates;

However, there are certain products that are absolute “no-no” when using flux for electronics.

How to Use Flux When Soldering Image

What flux agents you must avoid:

  1. Inorganic acid flux agents are good for bonding strong metals like stainless steel or brass. These agents include strong acids like zinc chloride or ammonium chloride. A complete cleaning is necessary immediately after using the soldering flux of this kind. The corrosive leftovers on the surfaces may destroy the solder joint! Never use such agents for assembling electronic devices or any electronic work;
  2. Lead-free electrical solder will do only for small wiring projects. Yes, such products are eco-friendly because have no lead but won’t make a strong hold;
Universal advice for buying a flux agent for electronics: eventually, the major thing to remember is that the least aggressive (i.e. the least acidic) agent is the best one in all scenarios. Such an additional layer during a soldering job will make sure that oxides are under the control and form a great bond.

Most experts advise picking rosin-based flux agents for electrical soldering. Most electronics and wires are extremely fragile, corrosive agents must be avoided. Local hardware stores will surely have such agents for soldering fans.

How to Use Flux When Soldering Picture

Consider using the so-called water-soluble fluxes. You can find them both in a liquid form and a semi-liquid gel. Their major advantage is a strong corrosive effect with maximum oxidation of the intertwined parts. Also, they don’t conduct electricity nor require washing the board after finishing the works. Nevertheless, it’s still better to remove all residual flux from soldered parts after soldering.

Sra Rosin Paste FluxThe SRA Rosin Paste Flux is offered in a small container holding 2-ounce flux to complete all of your soldering applications.

To apply liquid flux, you may require a paintbrush, cotton swab or even a single match. But it’s more acceptable to buy the so-called “flux applicator”. Branded flux applicators cost about $20-30 per item, so for some it will be a wiser choice to do such an applicator on their own. You will require a piece of silicone/rubber hose (choose the diameter of 5-6 mm), and a disposable syringe.

How to Use Flux When Soldering Cords

Cut a syringe into 2 parts. Both parts must be placed in a tube made of rubber. The needle is slightly shortened, it can be slightly bent for ease of use. Pressing the hose lightly, squeeze a drop of flux from the tip onto the soldered parts and solder. When storing, so that the needle does not dry out, thin wire can be inserted inside it.

Consider using flux gel or paste. For its application, you can also pick a disposable syringe, only because of its density, the syringe needle must be thick.

How should you prepare a soldering tool?

When working with electronics, it is essential to clean it immediately after use. So make sure the iron is clean and only then turn it on. Plug in or turn on the iron and wait while it is heating up. When it’s hot, apply a damp sponge for cleaning the tip. Do not touch the hot end while cleaning!

Always leave the iron on the stand when the tool is on. The hot tip may start a fire if left unsupervised.

When the iron’s tip hot and clean apply a small amount of solder. Wipe away any access with a damp sponge. Such a technique is called “tinning” the iron, it prevents oxidizing when you work with electronics.

Using Flux When Soldering

The application process will depend on what kind of low-melting composition is used:

  • When using solders it’s necessary to dip a soldering iron into the body of the reagent and hook a small amount of solder;
  • If a liquid ready-made mixture is used, it can be applied with a brush;
  • When working with paste, it is required to apply it to the junction with a stick, a toothpick;
  • Also, do not forget about cleaning the surface from oxidation;

Consider wearing special gloves made for leather to prevent burns when using soldering flux agents.

Using Flux When Soldering Electronics Image

A step-by-step guide for soldering wires with flux agents

  • Initially, the surfaces must be cleaned. Make sure that each wire is clean;
  • After stripping, a flux layer is applied;
  • Intertwine the wires to avoid any pointed ends;
  • To melt the flux agent pressure onto one side of intertwined wires. When the tool is hot, press it against one section of the wires to heat up. Keep pressing the tool to the wires until the flux is melted, but before bubbles appear;
  • In the end, be patient for the seam to harden – in a few minutes;

It’s impossible to connect the contacts without a special composition. Experienced soldering users suggest that beginners do the job without flux and see the result — the job will take much longer, the shock will quickly fall off. The best additional material for adhesion is pure tin. However, this is not a cheap metal and mostly it’s applied along with lead.

Tips for soldering electronics with flux

  • Don’t forget about using flux on the board;
  • The paste form is almost always a smarter choice than a liquid form;
  • No-clean flux is a “no-no” for assembling cables – solvents won’t remove such agents;
  • After the job, please remove flux with any store or DIY solvents. They must drain away from contact-insulating zones;
  • Water and solvent should never go to the body of your connector. If it happens, use fresh solvent for flushing the leftovers in this area;
  • It’s better to pick deionized water for removing any residues;
  • Stay away from the solder’s fumes, they may lead to asthma and other serious healthcare problems, consider wearing a respirator when applying;

I can’t say that soldering with flux is simpler when you deal with electronics and cables. But in the end, thanks to the previous tips you’ll get a solid bond in a shorter time period. And, that is what you seek, right? Bonding electronics with or without flux agents – what is your choice?

Hi! My name is Tom and I’m an author of the blog. My hobby is electronic circuits and soldering irons.

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  1. Thanks for sharing the content. Soldering flux is actually activated with the help of the heat of the soldering operation to remove the last layer of oxidized metal so that the solder will wet the base metal and produce a good joint.

  2. Glad to learn about the application of flux on soldering electronics. Thanks for sharing the blog Tom.

  3. Hi. Can you help me? When we perform soldering process finish, our gold surface is deformed. Do you know some reason for this problem? Thanks

    1. Hello, Thuan! Once the solder has flowed along the joint, and the metal surfaces have been heated sufficiently to join together, turn off the torch and let the gold cool. After a couple of minutes, quench it further in the water bath. Use copper tools to lower the gold slowly into the pickle bath, and wait a few minutes for most of the discoloring fire-scale on the surface to be removed. Remove the gold from the pickle, rinse in the water bath, and inspect. You may need to polish or file off excess solder or fire scale to achieve the appearance you desire.

  4. Hi.i have a problem which I can not answer for this. When we do soldering process, the gold layer is deformed. Please advise me for this. Many thanks

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