Soldering Paste or Rosin — differences, benefits & uses
In electronics, every detail matters — especially when it comes to the soldering process. Clean, durable, and aesthetic solder joints depend not only on technique but also on choosing the right auxiliary materials. That’s why a common question arises in workshops: “Soldering paste or Rosin?”
Both Soldering paste and Rosin (Colophony) serve a similar purpose — they make soldering easier, improve solder wetting, and protect the soldered surfaces — but they differ in properties, applications, and how they are used. Selecting the right flux is crucial for efficient soldering, reliable connections, and high-quality joints.
Flux – An Essential Element of Soldering
Flux refers to chemical substances that make the soldering process easier. Its main functions are removing oxides, lowering surface tension, and improving solder flow. In electronics, the flux determines whether a strong and stable joint will form.
Types of flux include:
Liquid fluxes – easy to apply on larger surfaces (e.g., AG5, AC81/N, LP1, RF800, TK83, TS81)
Gel fluxes – used for precision soldering during SMD and BGA rework (Ball Grid Array)
Synthetic fluxes – modern, high-activity formulas (e.g., TS81, AG5)
Acid fluxes – highly active, used outside electronics (e.g., Soldering Acid, Borax Flux, Soldering Water)
Rosin / Colophony – a natural classic of soldering workshops.
Soldering Flux – How It Works
When heated, soldering flux becomes active and creates a protective layer. This improves solder wetting and prevents re-oxidation of the metal surface. Soldering flux isn’t limited to Rosin alone — modern flux formulations enhance soldering efficiency under demanding conditions.
Why does flux quality matter so much?
Poor or no flux leads to cold solder joints and weak connections, while the right flux improves quality, consistency, and durability.
More about this topic can be found in the blog post: “Soldering preparations – liquid soldering aids”
Rosin – A Classic in Soldering
Rosin (also known as Colophony) is a natural flux derived from pine tree resin. For decades, it’s been used to increase soldering efficiency and protect components. It doesn’t contain aggressive additives and performs exceptionally well in demanding soldering environments.
A common workshop question: Why use Rosin?
Because Rosin ensures better solder flow and more stable, high-quality joints.
Key properties of Rosin:
Prevents cold solder joints by eliminating oxides.
Protects soldered surfaces against re-oxidation.
Improves solder wetting during heating.
Gentle, non-corrosive action.
Acts as an active flux when heated.
Serves as a base for many modern flux products (e.g., RF800, TK83).
Plays a crucial role in maintaining soldering quality.
Despite advances in soldering technology, Rosin remains indispensable for electronics technicians and hobbyists alike.
Correct Use of Rosin
Using Rosin correctly is essential:
Apply a thin, even layer.
Use appropriate soldering temperature.
If needed, remove residues afterward with isopropyl alcohol or an alcohol PCB cleaner.
Be precise, even though Rosin is easy to use.
Advantages: effective, inexpensive, forgiving to use.
Drawback: residue cleaning may be needed in some processes.
Natural Rosin vs. Synthetic Flux
Another frequently asked question:
What’s the difference between liquid fluxes and Rosin, and which is better for precision soldering?
Rosin (Colophony) – natural, mild, and effective for standard soldering applications.
Synthetic & gel fluxes – more active and precise, ideal for demanding soldering tasks.
However, they often require cleaning afterward.
The right choice depends on the specific soldering process.
Precision Soldering – When to Use Soldering Paste
Soldering paste plays a crucial role in SMD assembly (Surface Mount Devices). It allows precise dispensing and ensures consistent, repeatable joints. Solder paste combines Rosin with an organic halogen activator, creating a powerful flux.
Advantages of soldering paste:
Precise application.
Fast, repeatable serial assembly.
Excellent solder flow.
Ideal for copper, tinned, silvered, zinc-plated, and nickel-plated elements.
Suitable for demanding soldering environments.
Pastes are widely used in radio, telecom, and electronic device manufacturing.
What is soldering paste used for?
Precision, repeatability, and cleanliness — this is where soldering paste plays a key role. In SMD and BGA soldering, soldering paste stands out for its high application accuracy and stable behavior during heating. Thanks to this, it enables consistent, repeatable results in the soldering process while minimizing the risk of errors.
Additionally, it is highly active, allowing for the creation of strong, clean solder joints while shortening the overall process time. All these advantages make soldering paste an ideal choice for a wide range of applications — from precision metal soldering in radio and telecommunications technology to the assembly of electrical devices.
Key Differences – Soldering Paste vs. Rosin
| Feature | Rosin (Colophony) | Soldering Paste |
|---|---|---|
| Type | Natural flux | Flux with halogen activator |
| Application precision | Medium | Very high |
| Use case | Through-hole soldering, repair | SMD/BGA soldering, serial production |
| Residues | Easy to remove | Requires cleaning (alcohol-soluble) |
| Joint durability | Excellent | Excellent, highly repeatable |
| Cost and ease of use | Low, very easy | Higher, requires skill |
In practice, combining both materials gives the best results.
Quality of Solder Joints
No matter which material you choose — Rosin (Colophony) or solder paste — the cleanliness of the surface is crucial. A clean surface ensures stable, aesthetic, and high-quality joints.
Grab your solder! Check what else a good soldering kit should include.
A well-assembled soldering kit is the foundation of efficient work in any electronics service. It should include:
Gel flux for precision work
TK83 flux for restoring solderability
High-quality solder
Isopropyl alcohol for cleaning
Such a set guarantees strong, reliable joints in both serial production and repair work.
Conclusion
The question “Soldering paste or Rosin?” doesn’t have a one-size-fits-all answer:
Rosin – simple, natural, and effective for standard soldering.
Soldering paste – ideal for precision SMD and BGA work.
Combination of both – offers maximum flexibility and the highest soldering quality.
By understanding when and how to use Rosin (Colophony) and soldering paste, you can significantly increase soldering efficiency and ensure durable, clean joints in any electronic project.