What is a Liquid Solder and How Do you Use It?


Liquid solder is a molten metal developed to help in joining two metal surfaces. In particular, the liquid is a water-resistant and powerful adhesive that provides an effective alternative to the high-melting and conventional point solder interconnects. That is why liquid solders have continued to become famous, heavy-duty options among most metal contractors and workers.

Types of liquid solders

Liquid solders come in a can or tube to help you in different soldering projects. Liquid solder in tubes is suitable for small jobs, and you can apply it directly to your intended joints. In contrast, canned liquid solders are meant for large surfaces, and to apply them, and you will need a wooden stick or paddle. The major liquid solders in the marketplace include Rosin Flux, Permatex, SMD, PCB, and BGA fluxes.

Rosin flux

It is a non-corrosive solder used for soldering wires to metal chassis, forming seals, and pot tinning copper and brass metals. One of the main merits of rosin flux eliminates the waste and hazards associated with solvent-based and organic liquid fluxes. It offers a non-corrosive alternative to chloride and other acid-based liquid solders.


It is a specially blended adhesive liquid flux solder that offers a metal-tough and weather-resistant bond after it dries. The liquid is quick-drying soft and does not need the application of heat. That makes it easy to use this liquid solder, and it is a famous choice among most first-time users. You can use it to fill small cracks or holes and also repairing splits in seams in metal. This liquid is also recommended for use in broken trunk compartments, battery trays, floor panels, and weld lines. It would help if you did not use the Permatex for electrical repairs since it does not have conductive material.

BGA, SMD, and PCB Flux

BGA, SMD, and PCB are liquid solders formulated for Ball Grid Array tools and equipment. These are non-corrosive and high-quality liquid solders with low melting points and provide the advantage of preventing CSP Hydroplaning. The liquids are non-conductive when dry, meaning they are suitable for re-balling. Due to their low residue formation, they make cleaning easier.

How to use liquid solder

Liquid solders are usually used for bonding metal and other solid materials, including concrete. You can follow the following steps when using a liquid solder. Decide if you want to use liquid solder in a can or a tube for your soldering project. If you work within a confined surface, you should wear protective gear before using the liquid solder. Examine the joints you want to bond together. For optimum results, the surfaces you want to join together should be dry, smooth, and clean. Also, the surfaces should be free from greasy fingerprints. Such issues can interfere with the soldering process, making it hard for the liquid solder to flow through the joint properly. Also, ensure that the soldering joint is free from a flush. You can file it until you cannot see the light seeping through it. That will help in ensuring that your soldering joint becomes strong since the liquid solder will attach properly. You will be required to apply the liquid solder on one surface. If you are using a tube solder, you can directly apply it from the tube. However, if you are using a can tube, you can use a wooden paddle or stick to apply it to the joints.

Wipe away any excess liquid solder on the soldering surface. Ensure you do that immediately to maintain liquid consistency. You can use the same techniques which you could use for solder wires or strip. Depending on the liquid you are using, you can apply heat to the soldering joint in a circular motion. When the metal piece achieves a glowing sully cherry red look, you can focus the heat on the solder joint. After applying the solder, you need to clamp together the bonded parts for approximately 30 minutes to achieve a strong bond. If you wish to release the bonded surfaces, you can apply acetone to dissolve the elements bonding the metal surfaces together. You can find acetone in most of the drug stores and nail polish remover shops. If you are not satisfied with the solder joint, you can re-clean the surfaces and add more liquid to the liquid.

Methods of applying liquid solder

Even if you are using liquid solder in prototype PCB or mass PCB assembly, you need to follow specific steps. In particular, you should apply the solder on circuit boards. Also, ensure that you only apply to the areas where you want to solder. The following are the most famous method to apply liquid solder.

Using stencil

The stencil will enable you to apply the liquid solder only on the parts you want. You can place the stencil over the soldering area and ensure you apply the required liquid solder. Do not apply every little liquid because the joints can become weak and disintegrate easily. In contrast, you should not apply too much because the joints can become large, and it can result in the likelihood of shorts between adjacent pads.

Using a jet printer

A stencil is the best in applying liquid solder for mass PCB assemblies. However, depending on the PCB assembly, you can spend a lot of time establishing a stencil. It can also be hard to control the amount of liquid that you can apply to the joints. Fortunately, a jet printer will overcome such demerits, although it is not appropriate for all kinds of liquid soldiers. In this case, the liquid should have a low viscosity for you to easily jet print it. The best thing is that the jet printer has been programmed according to the PCB assembly pattern. The printer has a cartridge where you will fill your liquid solder. The printer applies the appropriate amount of liquid solder to the joint areas. Notably, jet printing the liquid solder increases the precision and offers more flexibility in the way you solder metals.

Liquid solder acts as a critical component in the soldering process by enabling electrical conductivity, establishing reliable joints, and protecting your metal boards from oxidation and corrosion. However, if you wish to achieve such purposes, you should select the appropriate kind of liquid solder. After choosing a solder, you can apply it by following the above steps and any soldering techniques that you think are relevant.

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