Read this article to see how low-temp soldering is cutting carbon in electronics.
INTRODUCTION
Reducing carbon dioxide (CO2) emissions faces a key challenge in all industrial sectors. The electronics industry plays a significant role due to its energy-intensive production processes. The adoption of new soldering techniques in component assembly offers an opportunity to reduce energy consumption and improve sustainability in the electronics manufacturing industry.
Originally developed to protect sensitive components from heat, soldering with Low Temperature Solder (LTS), became an effective solution for reducing energy consumption during soldering. This technology ensures high process reliability and flexibility, while reducing equipment, labor, and maintenance costs.
The objective of this article is to examine the characteristics of MacDermid Alpha OM565[1] solder paste with lead-free HRL3[2] alloy, evaluating both reliability and the potential to reduce its carbon footprint.
HISTORY AND DEVELOPMENT OF LTS TECHNOLOGY
Following the transition to “lead-free” processes, imposed by regulations, the electronics industry has adopted solder pastes based on tin (Sn), silver (Ag) and copper (Cu) – SAC alloys[3] – valued for their robust mechanical and thermal properties. However, these alloys require high reflow temperatures between 240°C and 250°C, which have several inherent drawbacks:
- High energy consumption: Achieving and maintaining high process temperatures, increases operating costs and carbon footprint.
- Equipment wear: Elevated temperatures accelerate wear and tear on reflow ovens and soldering machines, increasing the need for maintenance.
- Thermal stress on components: High thermal stress can cause degradation of components and substrates, leading to warping and premature aging.
In particular, a lower peak temperature in the reflow process (below 200°C) drastically reduces thermal stress, preventing defects and increasing reliability, a crucial advantage, for example, in “Package-on-Package” (PoP) applications.
Initially, LTS alloys were primarily studied for assembly with heat-sensitive components. Early studies focused on two metals known for their low melting points:
- Bismuth (Bi): The Sn42-Bi58 alloy melts at 138°C, but bismuth experts recognize it for its brittleness. It tends to fracture rather than deform, limiting its electronic applications. Developers introduced formulations such as Sn-Bi-Ag (e.g., 42Sn-57.6Bi-0.4Ag) to further improve the properties and enhance fatigue resistance.
- Indium (In): The Sn52-In48 formulation melts at (118°C) and exhibits greater ductility than bismuth alloys. However, its main disadvantage is the extremely high and unstable market cost of Indium[4].
Researchers developed new formulations such as HRL3 from MacDermid Alpha, a complex multicomponent alloy. This alloy, combined with OM565 solder paste, was chosen for use in the CIRC-UITS project, funded by the Horizon Europe program, which aims to promote sustainability and circularity in the electronics sector.
ENERGY CONSUMPTION AND ENVIRONMENTAL IMPACT
The adoption of LTS technology offers significant advantages in terms of reducing energy consumption and costs in soldering processes. Decreasing the reflow temperature from 250°C to 190 C or 175°C can generate energy savings of more than 30% per production run.
This energy reduction directly translates into a substantial decrease in carbon dioxide (CO2) emissions, making a significant contribution to sustainability goals. Additionally, low temperatures enhance the long-term reliability of products by reducing thermal stress on components and substrates. This also enables the use of printed circuit boards (PCBs) with lower glass transition temperatures (Tg), which offer additional material cost savings.
A simple calculation we can make on a single soldering system is the following:
Engineers adapt the setting temperatures for SAC-based alloy paste, because its melting point exceeds 220°C. In the preheating phase, above 180°C, and in the peak phase, above 250°C, a power of more than 20 kWh and CO2 emissions of more than 42 kg of CO₂e are consumed. On the other hand, the use of OM565 paste with a melting point at 146°C, allows much lower temperatures, 140°C in the preheating phase, and a peak at 175°C, which translates into a power of just over 14 kWh and a CO₂e impact of 29 kg.
From a life cycle perspective, the cumulative energy savings over millions of units are enormous. For manufacturers who make thousands of boards per day, this can translate into annual savings of several megawatt hours (MWh), markedly reducing environmental impact.
RELIABILITY OF LTS ALLOYS
A key barrier to adopting LTS alloys in automotive applications has been concern over their reliability. However, recent research by the CIRC-UITS consortium on the HRL3 alloy has provided valuable insights that address these concerns.
For testing purposes, HRL3 alloy with OM565 paste has been compared with SAC-based high-reliability alloy that is widely used in the automotive industry. The tests have been conducted on sample cards provided by a well-known automotive manufacturing company, part of the CIRC-UITS project, and included shear test analysis after thermal shock (1,000 and 2,000 cycles, from -40°C to 125°C) and hot aging (1,000 hours at 85°C, 125°C, 150°C).
The results showed that the OM565 alloy in HRL3 consistently performs reliably at temperatures below 100°C. Its performance was on par with the high-reliability SAC alloy, which excels at more extreme temperatures and thermal cycling tests. These results confirm that in the automotive sector, HRL3 alloy can be successfully use in interior applications such as infotainment systems, lighting, and in many ‘off-the-bonnet’ applications[5] where operating temperatures do not exceed 100°C.
REGULATORY ENVIRONMENT AND SUSTAINABILITY STANDARDS
Global regulatory frameworks and companies’ sustainability goals are becoming increasingly stringent, and lower melting temperature alloys are perfectly aligned with these initiatives. Programs such as the European Green Deal, the United Nations Sustainable Development Goals (SDGs), as well as various national commitments to carbon neutrality are pushing manufacturers to adopt cleaner and more efficient technologies.
In response to these directives, standardization bodies such as IPC (GEA), IEC, and ISO, are updating their protocols to include sustainability requirements. LTS alloys meet these new standards, allowing companies to demonstrate reduced energy consumption and emissions per unit produced. In this way, companies can more easily obtain prestigious environmental certifications such as ENERGY STAR, promoted by the US EPA to comply with strict energy efficiency criteria, or the EPEAT (Electronic Product Environmental Assessment Tool), managed by the Global Electronics Council (GEC), a global ecolabel that identifies electronic products meet high environmental standard or finally the TCO Certified, one of the most globally recognized certifications for product sustainability.
This will translate into supporting the supply chain, reducing emissions related to the goods and services purchased.
CONCLUSION
In summary, HRL3 low-temperature solder alloy offers a viable and effective technology for minimizing environmental impact in electronics manufacturing. Not only does it significantly reduce energy consumption and CO2 footprint, but it also improves compatibility with temperature-sensitive components and offers promising reliability in a wide range of applications.
The introduction of OM565 solder paste elevates this solution from a niche option to a strategic choice[6] for electronic industry. Adopting this technology means initiating a broader shift towards sustainable innovation, improving operational efficiency and product performance. This presents a real opportunity that offers a measurable benefit for both the manufacturers, and the planet.
[1] ALPHA® OM-565 HRL3 Solder Paste | MacDermid Alpha
[4] Price volatility may rise in fragmented indium market – Argus Metals
[5] “Off-the-bonnet” applications refers to electronic systems and components that are not located under the vehicle’s hood (bonnet)—i.e., they are positioned elsewhere in the vehicle, typically in the cabin or body, where thermal demands are typically lower.
[6] Wu, G., Shen, J., Zhou, D., Faiz, M. K., & Wong, Y. H. (2025). Applications and Recent Advances of Low-Temperature Multicomponent Solders in Electronic Packaging: A Review. Micromachines, 16(3), 300. https://doi.org/10.3390/mi16030300.