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  •  05/28/2026

Behind the MFG. | From "Manufacturing" to "Creation" Ep.2: Innovation Built from Zero to One


In the field of electronics manufacturing services (EMS), technological progress often begins with a refusal to settle for the status quo. If Ep. 1 examined miniaturization as a battle against the limits of physical space, this article explores innovation as a fundamental shift in process thinking.

Today’s global electronics supply chain faces overlapping challenges in environmental sustainability (ESG), high-performance computing (HPC), and the reliability of advanced packaging. Through the hands-on experience of two technical experts—Deputy Director Eric Chiu and Manager CW Chang—USI’s Corporate Operations Development Division (COD) demonstrates how environmental standards can be built from scratch, and how invisible risks can be transformed into visible, mistake-proofing controls. This is more than the accumulation of technical know-how; it is the core driver behind the invisible value USI creates for its customers.
 
COD Technical experts: Deputy Director Eric Chiu

Pioneering Green Processes: The Shift from Organic Solvents to Water-Based Cleaning

With the rise of environmental sustainability and green manufacturing, conventional cleaning methods that rely on organic solvents such as n-propyl bromide (nPB) are gradually being phased out by the market. However, transitioning to a water-based process without compromising quality is far more complex than simply changing the cleaning chemistry.

Beyond Convention: Building a Cleaning Logic for High-Density Assemblies

As Eric recalls, the initiative began as a response to a Japanese customer’s stringent requirements for environmentally friendly processes. The team decided to take on the challenge of building a full-line Water Clean Process from zero to one. The key difficulty lay in enabling water-based cleaning chemistry to penetrate the tiny gaps within high-density components such as SiP (System-in-Package) modules.

Using DFM (Design for Manufacturability), the team redefined the production line by integrating soaking tanks and spray sections into the equipment, applying ultrasonic energy to enhance chemical penetration, and adding a multi-track transfer design. This innovation not only met environmental requirements; it also surpassed conventional equipment in cleaning efficiency and output, turning an environmental requirement into a productivity advantage.
 
COD Technical experts: Manager CW Chang

Pursuing “Zero Residue”: Developing the Formic Acid Reflow Process

In advanced packaging and high-reliability electronics, residue is often considered one of the biggest threats to yield. Traditional reflow soldering relies on the rosin contained in solder paste as the fluxing agent during soldering. While rosin effectively supports solder joint formation, the remaining residue requires a complicated post-cleaning process and may also introduce potential failure risks.

Subtractive Innovation: The Birth of a Rosin-Free SMT Process

The Formic Acid Reflow process developed by the COD team is an industry-first rosin-free SMT solution. At its core, the technology uses formic acid gas to directly replace the rosin flux in solder paste. Through the redox reaction among formic acid, the substrate, and rosin-free solder paste, the process achieves genuinely residue-free soldering and further eliminates the post-cleaning step required in conventional processes.

During development, the team tested nearly ten rosin-free solder paste formulations and addressed both high-temperature safety management for formic acid gas and process-parameter fluctuations. The project consistently focused on one core idea: “What we wanted to solve was not how to clean residue, but how to prevent residue from being generated in the first place.” This technology not only eliminates the cost and power consumption of downstream cleaning, but also provides a highly competitive, energy-saving manufacturing solution for SiP products.

The Art of Proactive Mistake-Proofing: Colored Flux Development and Visual Management

On high-speed production lines, the most dangerous risk is an invisible failure. In the Flux Dipping process widely used for SiP miniaturization, conventional flux is typically a transparent paste. As a result, the existing recognition system on the placement machine cannot determine whether dipping is uniform. This can lead, often unnoticed, to batch-level non-wetting or open-solder defects, increasing both repair and scrap costs.

Making Risk Visible: The Reverse Thinking Behind Black Flux

The COD team proposed an idea that seemed simple but was highly ingenious: “If we can’t see it, let’s give it color.” Based on this reverse thinking, the team worked with suppliers to develop a Black Flux that could be detected by the placement machine’s recognition system.

This innovation enables the placement machine to identify dipping conditions in real time and proactively. If the dipping amount is insufficient, the machine immediately triggers an alarm and rejects the part. By intercepting risk at the front end of the process, this change effectively prevents batch-level open-solder defects from occurring—or from escaping to downstream processes—and significantly improves scrap rates. This shift from passive inspection to proactive mistake-proofing not only enhances process visibility, but also demonstrates USI’s resilience in continuously improving process stability.

Technical Resilience Creates Invisible Value for Customers

From the miniaturization breakthroughs discussed in the first article to the green, safe, and mistake-proofing innovations explored here, USI COD demonstrates more than manufacturing capability—it shows professional technical resilience.
The standards established through countless DoE validations, material tests, and process redesigns are ultimately transformed into competitiveness for customers’ products. When customers choose USI, they gain not only production capacity, but also technical resilience that acts before problems occur. This capability ensures that, as customers face rapidly changing market demands, they are supported by an R&D team capable of turning challenges into advantages.




COD Expert FAQ: A Guide to Process Innovation and Environmental Sustainability

Q1: Why is the Water Clean process becoming increasingly important in the EMS industry?
A1: As global regulations on chemical solvents such as nPB become stricter and ESG-driven sustainable manufacturing requirements continue to rise, the Water Clean process offers an environmentally friendly approach that can more effectively remove trace rosin from high-density SiP modules, thereby improving product reliability.

Q2: What is the biggest difference between Formic Acid Reflow and conventional reflow soldering?
A2: Conventional reflow soldering uses the rosin contained in solder paste as the fluxing agent, which leaves rosin residue after reflow. Formic Acid Reflow instead uses formic acid gas to activate the soldering surface, enabling rosin-free, zero-residue quality and eliminating the need for the traditionally costly post-cleaning process.

Q3: Why did USI develop colored Flux, and how does it support quality management?
A3: Conventional flux used in dipping applications is a transparent paste, making it difficult for the placement machine’s recognition system to determine the flux dipping amount. By developing Black Flux, the machine can “see” the flux and actively identify the dipping condition in real time. This enables proactive mistake-proofing and significantly reduces batch defects or scrap caused by open solder joints.

Q4: How does COD ensure the safety of new processes, such as those involving formic acid gas?
A4: For gases with potential risks, the team implements dual exhaust systems, redundant sensor designs, and process simulation modules to ensure that innovation is pursued while absolute safety on the production floor is maintained.

Q5: What challenges arise when applying rosin-free / flux-free solder paste in a formic acid reflow oven?
A5: Rosin-free solder paste lacks the tackiness and protection provided by conventional flux, making soldering instability or open solder defects more likely. The COD team must go through months of parameter tuning and Design of Experiments (DoE) to identify the optimal temperature profile and gas ratio.
 

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