Amid the wave of miniaturization of photonic integrated circuits (PICs), encapsulation adhesives are emerging as a key bottleneck for breakthrough
Researchers at Columbia University have recently made a breakthrough in the field of optoelectronics, successfully fabricating the smallest integrated photonic circuit to date and achieving high-performance stable operation over a wide wavelength range for the first time. Researchers liken this achievement to replacing vacuum tubes with semiconductor transistors, with potential impacts significant enough to reshape optical communication and optical signal processing systems. However, as PIC continues to evolve towards smaller sizes, higher integration, and more complex functions, a key aspect that has long been underestimated but determines system reliability is gradually emerging: Packaging and bonding materials for photonic integrated circuits. In actual mass production, the challenges faced by PIC packaging mainly focus on the following aspects: Mode Field Matching (模场匹配) sub-micron high-precision alignment and assembly technology for high-speed, repeatable automated packaging processes, which can reliably operate under harsh conditions such as high temperature, high humidity, and reflow soldering, has a very high cost proportion. According to the report “Photonics Packaging 2023” by Yole Développement In photonic integrated systems, over 70% of the overall cost comes from packaging and assembly processes This means that packaging materials, especially adhesives, are no longer “auxiliary materials” but rather system-level key materials. II. Why are adhesives for PIC packaging so demanding?In the PIC package, the adhesive plays multiple roles simultaneously: 1️⃣ Mechanical fixation + optical stabilization: Wafers, chips, optical fibers, lenses, and waveguide arrays require long-term submicron-level positional stability. The shrinkage rate, modulus, and stress release capability of the adhesive directly affect the optical coupling efficiency. 2️⃣ Thermal-moisture-stress multiphysics coupling: Reflow soldering, high-temperature storage (HTS), and high-humidity high-temperature (HAST) conditions can lead to optical path drift or failure due to material water absorption and CTE mismatch. 3️⃣ Process window determines mass production yield: UV/thermal curing speed, dispensing fluidity, thixotropy, dimensional stability and consistency after curing….
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