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Choosing the Right Flux and Solder Paste Composition for Your PCBA

Choosing the Right Flux and Solder Paste Composition for Your PCBA

The continual evolution of circuit solutions dictates a trend towards miniaturization of electronic components. Printed Circuit Board (PCB) now operate at higher temperatures, smaller sizes, and increased complexity. Consequently, this has led to heightened intricacy in polyurethane (PU) production. To ensure the functionality of Printed Circuit Assemblie (PCBA), thorough cleaning of their contaminants is imperative. However, this process can be quite intricate, particularly considering the challenges posed by no-clean flux residues, difficult to clean residues, or the ever-changing landscape of workplace safety regulations.
PCBA

Miniaturization – Small PCB sizes, Big Cleaning Challenges

The growing demand for small electronic products forces manufacturers to install more components in compact sizes. Miniaturization increases the risks of solder joint weaknesses, bridging, dendritic growth, and all other well-known soldering defects. The denser layout also makes traditional cleaning more challenging. This compels polyurethane manufacturers to seek and implement cost-effective, efficient, and flexible cleaning technologies. They must not only consider which cleaning processes are viable but also find a cleaning process that can easily adapt with the evolving PU manufacturing technology.
 
Today, many micro components are assembled on PCBs using no-clean solder paste. While the formulation of no-clean flux aims to leave minimal residues on the circuit board, even such residues can still absorb moisture, interfere with the adhesion of conformal coatings, or simply be aesthetically undesirable. Moreover, modern circuit boards have more residues and contaminants to deal with, beyond just flux residues. The irony of no-clean flux lies in the fact that not only do PUs still require cleaning to function properly, but the residual residues are extremely difficult to remove, making the cleaning process even more challenging.
Flux and Solder Paste on PCBA 01

“Non-Clean flux” means “Needs Cleaning flux”

No-clean flux was initially developed to eliminate the need for cleaning PUs. Solutions planned back in the 80s to address many emerging difficulties are no longer applicable to modern electronic circuits. Today, washing is a crucial process. This importance stems from various reasons, including the unpredictability of the final outcome. Improper PU cleaning poses contamination risks that can affect work quality. For instance, accumulated flux may interfere with signal transmission.
If PUs are exposed to outdoor or harsh environments, they require the application of conformal coatings. Flux residues hinder the proper adhesion of coatings to PCBs. These residues often absorb moisture, so if any further curing processes are undertaken, moisture begins to evaporate, causing delamination of the coating from the board and disrupting the uniformity of the conformal coating. This leads to coating application failures, as moisture and corrosives may reside on the polyurethane. This, in turn, leads to corrosion, signal transmission issues, and even complete failure of the printed circuit board.
 
Flux residues also mar the appearance of the circuit board, which is a significant problem for consumer electronics products like graphics cards and sound cards. We also must not forget that flux residues often render visual quality control nearly impossible. Similarly, they may cause failures in automated visual inspection systems and in bed of nails testing systems used for electrical and functional testing.
As control devices become smaller and more complex, they also require many quality control procedures, especially in high reliability devices. Residual flux hampers quality control processes, such as troubleshooting new products. Thus, it is crucial to identify potential cleaning issues during the design phase and determine the best flux and solder paste to use, especially when cleanliness is paramount, such as in medical products manufacturing.
Flux and Solder Paste 02
Flux and Solder Paste on PCBA 02
Flux and Solder Paste on PCBA 05

What is the Best Cleaning Method?

It is important to remember that not only the soldering process and flux cleaning affect the final state of the PU. There are other steps in the assembly process: inspection, testing, storage – all of which can lead to contamination issues. To successfully assemble PUs, adhesives, fingerprints, particulate matter, marking inks, epoxy resins, and other materials must also be removed. How do you choose the right cleaning method? The key is knowing the type of contaminants to be removed and comparing it with the cleaning process. Consider what type of contaminants need to be removed. Is it just ordinary debris or does it include removal of unnecessary flux residues?
 
Today, the market is witnessing the emergence of increasingly new types of fluxes, making it difficult to find the appropriate cleaning type. Not only do you need to find a solution that can quickly and effectively clean difficult-to-clean flux residues and contaminants, but you also need to consider the technical issues related to throughput, footprint, and finances. Ability.
 
Special attention must also be paid to some conflicting aspects that need to be addressed: worker safety, waste disposal, global warming, volatile organic compounds, halogens, waste recycling, and so on.
The answer lies in modern precision cleaning agents. Their development is aimed at addressing a wide range of issues and is an effective and cost-effective cleaning option. When used in well-designed, reliable vapor degreasing equipment, they require little supervision or management. The high density, low viscosity, and low surface tension of these cleaners enable them to successfully handle small-sized PUs, even in the most hard-to-reach places and smallest spaces. Combined with the PCBA cleaning machine I.C.T-5600, you can get twice the result with half the effort.
 
These liquids can also be customized by combining two or more components, which, when mixed, can effectively clean and provide all the necessary benefits of modern cleaning. This makes the cleaning process simpler, safer, and more reliable. They also have lower toxicity and better environmental performance.
 
Future Advanced Electronic ChemistryToday, advanced cleaning fluid manufacturers offer solutions that are absolutely safe for the ozone layer, including. European Union regulations (REACH) requirements. These innovative cleaning fluids are not only environmentally friendly but also capable of providing consistent and reliable cleaning, including… and difficult-to-remove flux residues and other solder paste residues that do not require cleaning.
 
It turns out that a good solution for cleaning difficult-to-clean stains and flux residues is a cleaning agent composition based on ultra-pure siloxane. It can easily remove cured silicone adhesives and is also suitable for fluxes, pastes, organic residues, ions, silicone coatings, adhesives, greases, and oils. What’s more impressive about these innovative cleaning solutions is that they are green certified, have low VOC, ozone-friendly formulations, and comply with RoHS and REACH standards.
Flux and Solder Paste on PCBA 03
New solutions for flux and solder paste formulations play a crucial role in today’s electronic assembly. In turn, modern, non-flammable, environmentally friendly, high-precision cleaning can significantly and relatively inexpensively enhance the performance, reliability, and durability of even the smallest electronic devices.
 
With the increasing demand for high-reliability miniaturized electronic components, cleaning issues become more critical. This means adopting cleaning fluids and solutions that encompass all the functionalities of cleaning control units on small high-density components, while also considering worker safety, regulatory requirements, and the environment. Before selecting a cleaning solution, consult with a cleaning fluid manufacturer with the necessary skills and experience to provide the best options tailored to your specific requirements.

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