Soldering Paste vs Flux: The Ultimate Guide

About Soldering Paste vs. Flux, Soldering flux and paste are two important ingredients to make your soldering easy and reliable. 

So that you understand, soldering flux is important when it comes to cleaning the circuit board surface.

However, you’ll need a soldering paste to strengthen the bonds between metals. 

Interestingly, there are major differences between a soldering paste and flux that many aren’t aware of.

Therefore, we have taken time to end the soldering paste vs. flux debate. 

Table of Contents

What’s Soldering Paste?

Soldering paste

(Soldering paste)

Soldering paste is an alloy of metal solder powder and flux. You can use this metal combination to create perdurable bonds between metals. Therefore, we recommend soldering paste to join two metals or wires together. Interestingly, soldering paste does more exemplary work than regular glue.

What’s Soldering Paste Made of?

This paste contains solder powder, flux, and filler materials. The function of the flux is to draw heat from components, thus limiting melting and deformation. Moreover, the solder powder forms a conductive bridge between the two metals.

Finally, the filler materials increase the bond strength between the metals. 

Factors To Consider While Choosing A Soldering Paste

Generally, a soldering paste is available in different types with unique properties. You’ll note that pastes are designed for specific applications. Additionally, pastes come with varying melting points. 

Also, consider the soldering paste’s viscosity since it affects how easily you apply it. Lastly, the solder paste has different solder alloys, thus affecting the bond strength. 

How To Use A Soldering Paste

Soldering paste and iron

(Soldering paste and iron)

The application of soldering paste is very easy. Follow the steps below: 

  • Firstly, clean the surface you intend to solder using a reliable solvent. Ensure the circuit board surface is completely dry. 
  • Secondly, apply enough soldering paste to your target area with a syringe. 
  • Thirdly, heat the paste with a soldering iron until it melts. Consequently, it’ll create a strong bond between the two metals.
  • Finally, after the solder hardens, remove components and ensure the joints are secure. 

Uses of Soldering Paste

To begin with, a soldering paste is critical for joining two metals. Moreover, it guarantees a durable wire connection on a circuit board

Furthermore, soldering paste finds common use in the stencil printing process to create electrical connections. Finally, the paste is common in joining mechanical parts and adjoining particles. 

Pros of Using Soldering Paste

  • Firstly, soldering paste makes electrical joints effective and durable
  • Secondly, it guarantees the transmission of uninterrupted electricity and improves soldering reliability
  • Since it’s viscous, you can apply it as glue
  • The soldering paste won’t affect your PCB; therefore easy to work with metals and electrical wires.

Cons of Using Soldering Paste

  • The paste requires expensive equipment to use
  • If you’re a beginner, you’ll find it difficult to use this paste

What’s Soldering Flux?

Soldering flux involves a chemical cleaning product developed from acids and other materials. Before a soldering exercise, you can use soldering flux to dissolve any oxides or contaminants from circuit components.

Therefore, it develops a stronger bond and creates a reliable electrical connection. 

You should apply your soldering flux before applying the soldering paste. 

What’s Soldering Flux Made of?

To better understand how flux works, you need to know what it’s made of. Generally, flux contains solvents, acids, and other materials. Surprisingly, rosin-based flux is the most common soldering flux and contains alcohol and rosin. 

We also have the acid core, no clean, water-soluble flux besides rosin-based flux. Interestingly, each flux type has unique properties that expose them to specific applications. 

Factors To Consider While Choosing A Soldering Flux

Consider several factors to select the best soldering flux for your circuit board. First, select a soldering flux perfect for your soldering metals or wires. Remember, some soldering flux causes damage or corrosion. 

Moreover, it would be best to consider what you intend to use your soldering flux on. Some fluxes work better with certain applications than others. 

Finally, you can consider the pricing of the soldering flux, especially if you’re on a budget. However, at no point should you compromise flux quality for the price. 

How To Use A Soldering Flux

Applying soldering flux with a syringe

(Applying soldering flux with a syringe)

Like with soldering paste, using soldering flux is also easy. Check out the steps below:

  • First, if you intend to apply the soldering paste, you should apply flux on the surface before the soldering paste. 
  • Heat the soldering flux with a soldering iron until it melts. This way, the flux will remove contaminants from the board’s surface. 
  • Next, apply the soldering paste and proceed with the soldering process. 
  • Sometimes, you might use soldering flux after applying your paste. In such a case, heat the joint until your soldering flux melts. Consequently, your electrical components will acquire a very strong bond. 

Uses of Soldering Flux

A technician using flux

(A technician using flux)

Generally, soldering flux is available and helpful for several uses. First, you can use it to increase the adhesiveness of your soldering paste. 

For you to solder effectively, the circuit surface needs to be clean. For this reason, we use flux to get a pure metal, thus making the joint firm. 

Also, flux helps to seal out air, thus preventing oxidations. Furthermore, it is a heat transfer medium when you heat electrical wires and metal joints using a soldering iron

In summary, the primary use of flux is to prepare your metal for effective joining. 

Pros of Using Soldering Flux

  • Soldering flux gets rid of metal oxides from a circuit board
  • It limits potential danger cases while you solder your circuit board
  • A reliable soldering flux cleans a metal surface quickly. 
  • Since it’s viscous, it mixes with paste easily

Cons of Using Soldering Flux

  • It sometimes creates resistance and disturbance with soldering the circuit board’s internal equipment.


Can you use paste without flux?

Yes! You’re free to use paste without flux. However, using it with flux improves the reliability and strength of your connection. Also, flux prevents corrosion and oxidation from happening. Therefore, we recommend using paste with flux.

Is soldering flux the same as soldering paste?

No! There are major differences in properties and composition between the soldering flux and paste. Generally, a soldering paste consists of flux and metal alloy particles.

You can use a paste to strengthen the bond between two metals. However, a flux involves a chemical cleaning product developed from acids and other materials.

Before a soldering exercise, you use it to dissolve any oxides or contaminants from circuit components.

Is flux better than paste?

Generally, no product is better than the other. Each product will excel better in its application and use case. For example, a soldering flux will clean and dissolve oxides from components better than paste.

On the other hand, a soldering paste excels at strengthening bonds between metals. 


We hope we have put the soldering paste vs. flux debate to rest. As mentioned, a soldering flux is handy when cleaning a circuit board surface to remove oxides and contaminants.

Moreover, you can use a soldering paste to strengthen metal bonds. Therefore, ensure you buy the best flux and paste for the best results.