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Characteristics of an Implantable Blood Pressure Sensor Packaged by Ultrafast Laser Microwelding

Department of Electronics and Control Engineering, Hanbat National University, Daejeon 34158, Korea
Department of Laser and Electron Beam Application, Korea Institute of Machinery and Materials, Daejeon 34103, Korea
Authors to whom correspondence should be addressed.
Sensors 2019, 19(8), 1801;
Received: 7 February 2019 / Revised: 11 April 2019 / Accepted: 13 April 2019 / Published: 15 April 2019
(This article belongs to the Special Issue Wearable and Implantable Sensors and Electronics Circuits)
PDF [2658 KB, uploaded 22 April 2019]


We propose a new packaging process for an implantable blood pressure sensor using ultrafast laser micro-welding. The sensor is a membrane type, passive device that uses the change in the capacitance caused by the membrane deformation due to applied pressure. Components of the sensor such as inductors and capacitors were fabricated on two glass (quartz) wafers and the two wafers were bonded into a single package. Conventional bonding methods such as adhesive bonding, thermal bonding, and anodic bonding require considerable effort and cost. Therefore CO2 laser cutting was used due to its fast and easy operation providing melting and bonding of the interface at the same time. However, a severe heat process leading to a large temperature gradient by rapid heating and quenching at the interface causes microcracks in brittle glass and results in low durability and production yield. In this paper, we introduce an ultrafast laser process for glass bonding because it can optimize the heat accumulation inside the glass by a short pulse width within a few picoseconds and a high pulse repetition rate. As a result, the ultrafast laser welding provides microscale bonding for glass pressure sensor packaging. The packaging process was performed with a minimized welding seam width of 100 μm with a minute. The minimized welding seam allows a drastic reduction of the sensor size, which is a significant benefit for implantable sensors. The fabricated pressure sensor was operated with resonance frequencies corresponding to applied pressures and there was no air leakage through the welded interface. In addition, in vitro cytotoxicity tests with the sensor showed that there was no elution of inner components and the ultrafast laser packaged sensor is non-toxic. The ultrafast laser welding provides a fast and robust glass chip packaging, which has advantages in hermeticity, bio-compatibility, and cost-effectiveness in the manufacturing of compact implantable sensors. View Full-Text
Keywords: implantable blood pressure sensor; ultrafast laser; glass welding; direct bonding; MEMS hermetic packaging implantable blood pressure sensor; ultrafast laser; glass welding; direct bonding; MEMS hermetic packaging

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Kim, S.; Park, J.; So, S.; Ahn, S.; Choi, J.; Koo, C.; Joung, Y.-H. Characteristics of an Implantable Blood Pressure Sensor Packaged by Ultrafast Laser Microwelding. Sensors 2019, 19, 1801.

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