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Adhesives are increasingly proving to be an alternative to soldering in display manufacturing. DELO has once again demonstrated this in extensive long-term tests with directional (anisotropic conductive) adhesives. The results underscore the potential of adhesives for the scalable series production of miniLEDs and future microLED displays.
Schematic illustration showing the process of miniLED integration on a PCB: before placement, after placement, and with the LED illuminated through adhesive connection
Advancing miniaturization is increasingly pushing conventional joining methods to their performance limits. That is why DELO's feasibility study, published in 2024 garnered significant interest among experts. At that time, DELO had shown that adhesives are in principle suitable for reliable electrical and mechanical miniLED connections. The adhesives not only perform a fixing function but also are directionally conductive to ensure the functionality of the MiniLEDs. In a now expanded study, these results were confirmed over significantly longer test periods— an important step toward the series maturity of modern miniLED and microLED displays.
The study focused on investigating the long-term stability of adhesive bonds under extreme conditions. From a long-term perspective, the electrical and thermal conductivity of the bonds are particularly important. Conductivity is crucial for the durability and performance of components in displays.
To test the long-term quality of the bonds, defined amounts of adhesive were first applied to test boards using a stamping process, and the miniLEDs were then cured at 180 °C using a thermode. The connections created in this way had to withstand extreme conditions for over 500 hours, including continuous heat of 120 °C and 85 °C and 85% relative humidity. This combination simulates the stresses of real-world application scenarios and places high demands on electrical and mechanical stability.
The evaluation included:
The anisotropically conductive adhesive bonds also passed a particularly demanding test that combined heat and moisture exposure. Since heat and moisture usually place heavy demands on soldered joints in particular, the results demonstrate high long-term thermal conductivity and robustness.
The findings were presented by DELO experts at MicroLED Connect – the world's leading trade event for microLED technology, which took place in Eindhoven on September 24–25.
Learn more about the detailed results of the study in our white paper:
The current study is part of a series of fundamental research projects that DELO supplements with over 3,000 customer tests annualy. With its expertise, DELO supplies leading industrial partners, including Infineon, Mercedes-Benz, and other players in the semiconductor, automotive, and consumer electronics sectors.
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| Feature | microLED | miniLED | OLED |
|---|---|---|---|
| Max. brightness | 4,000+ nits | 1,000–4,000 nits | 400–1,000 nits |
| Lifespan | >100,000 h | 60,000–100,000 h | 30,000–50,000 h |
| Burn-in risk | ❌ No | ❌ No | ⚠️ Yes |
| Black levels | ✅ Perfect | Very good | ✅ Perfect |
| Energy efficiency | Very high | Good | Average |
| Color representation (accuracy + color gamut coverage) | Very high (DCI-P3 > 99%, Rec. 2020 ~ 90%) | High (DCI-P3 ~ 90%) | Very high (DCI-P3 > 99%, Rec. 2020 ~ 75–85%) |
| Color depth | Up to 12-bit possible | Mostly 10 bits | Up to 12-bit possible |
| Contrast ratio | Virtually infinite (true black) | High, but limited by LCD layer | Infinite (pixels dimmable) |
| Latency/response time | Very low (< 1 ms) | Low (2–5 ms) | Very low (< 1 ms) |
| Viewing angle stability | Very high | Average to good | Very high |
| Cost | Very high | High | Moderate |
| Market availability | Very low (high-end/niche) | Limited (premium segment) | High – widely available |
| Construction | Thin | Thick | Very thin |
DELO is a leading provider of high-tech adhesives and has been offering solutions for the semiconductor, automotive, and electronics industries for over 25 years. Our innovative technologies set industry standards. Companies such as Bosch, Huawei, and Siemens trust DELO when it comes to superior adhesive technologies.
