Gap bridging in joining of glass using ultra short laser pulses

Cvecek, Kristian; Odato, Rainer; Dehmel, Sarah; Miyamoto, Isamu; Schmidt, Michael

doi:10.1364/oe.23.005681

Cited by 48 publications

(27 citation statements)

References 17 publications

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“…It is known that the HAZ represents the melted glass region [10,13]. Recently it has been shown that even regions outside the melt zone exhibit clear expansion of the order of several hundred nm [16] and possibly as much as 1 µm which has been demonstrated as being of benefit to glass-glass welding [17]. The ability of this formation to bridge a gap between two surfaces is therefore highly dependent on the size of the HAZ (melt zone) has reached as the formation approaches the gap.…”

Section: Discussionmentioning

confidence: 99%

Avoiding the requirement for pre-existing optical contact during picosecond laser glass-to-glass welding

et al. 2015

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Previous reports of ultrafast laser welding of glass-to-glass have indicated that a pre-existing optical contact (or very close to) between the parts to be joined is essential. In this paper, the capability of picosecond laser welding to bridge micron-scale gaps is investigated, and successful welding, without cracking, of two glasses with a pre-existing gap of 3 µm is demonstrated. It is shown that the maximum gap that can be welded is not significantly affected by welding speeds, but is strongly dependent on the laser power and focal position relative to the interface between the materials. Five distinct types of material modification were observed over a range of different powers and surface separations, and a mechanism is proposed to explain the observations.

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Section: Discussionmentioning

confidence: 99%

Avoiding the requirement for pre-existing optical contact during picosecond laser glass-to-glass welding

et al. 2015

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“…Figure 6 shows the measurement results of the surface roughness near the welding area by changing the etching time up to 40 min. According to published papers, optical contacted fused silica welding with ultrafast laser can bridge a 1 to 3 μm gap [20,35]. In conclusion, our etching time of 30 min, generating a surface roughness of 10 nm, which is still less than a hundredth of the wavelength of the welding laser, will not affect the welding efficiency [30].…”

Section: Resultsmentioning

confidence: 99%

“…They demonstrated the disappearance of Newton’s ring at the femtosecond laser scanned area, which implies the removal of the gap between glass substrates. Thanks to intensive investigations, including those from Cvecek et al and Okamoto et al, this method achieved higher throughput and process reliability by introducing efficient heat accumulation at MHz repetition, as well as optimized contact treatment methods [12,13,14,15,16,17,18,20,21].…”

Section: Introductionmentioning

confidence: 99%

“…Second, the width of the welding seam is typically a few tens of micrometers, keeping the welded lines as close as possible in a micrometer scale to the microfluidic channel, thus extending the useful space of the substrate [16]. Third, it has higher bonding strength than other bonding methods [16,18,20,21]. Although there is a lack of standardization and evaluation protocol of welding strength measurements thus far, a number of prior studies have already proven that femtosecond laser direct welding shows superior bonding strength compared with conventional bonding methods (e.g., shear stress measurement, three-point bending test, fracture strength, and simple leak check) [19,21,22,23,24].…”

Section: Introductionmentioning

confidence: 99%

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Bonding Strength of a Glass Microfluidic Device Fabricated by Femtosecond Laser Micromachining and Direct Welding

Kim

Joung

et al. 2018

Micromachines

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We present a rapid and highly reliable glass (fused silica) microfluidic device fabrication process using various laser processes, including maskless microchannel formation and packaging. Femtosecond laser assisted selective etching was adopted to pattern microfluidic channels on a glass substrate and direct welding was applied for local melting of the glass interface in the vicinity of the microchannels. To pattern channels, a pulse energy of 10 μJ was used with a scanning speed of 100 mm/s at a pulse repetition rate of 500 kHz. After 20–30 min of etching in hydrofluoric acid (HF), the glass was welded with a pulse energy of 2.7 μJ and a speed of 20 mm/s. The developed process was as simple as drawing, but powerful enough to reduce the entire production time to an hour. To investigate the welding strength of the fabricated glass device, we increased the hydraulic pressure inside the microchannel of the glass device integrated into a custom-built pressure measurement system and monitored the internal pressure. The glass device showed extremely reliable bonding by enduring internal pressure up to at least 1.4 MPa without any leakage or breakage. The measured pressure is 3.5-fold higher than the maximum internal pressure of the conventional polydimethylsiloxane (PDMS)–glass or PDMS–PDMS bonding. The demonstrated laser process can be applied to produce a new class of glass devices with reliability in a high pressure environment, which cannot be achieved by PDMS devices or ultraviolet (UV) glued glass devices.

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“…This degradation of the sealing quality can be mitigated by using ultrafast laser welding. Prior studies showed that ultrafast laser glass welding can effectively bond glass substrates by filling the interface gap up to 3 μm [46,47]. Figure 2B provides a schematic illustration of the ultrafast laser welding of a cover glass to the sensor substrate.…”

Section: Methodsmentioning

confidence: 99%

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

Kim

Park

et al. 2019

Sensors

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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.

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Gap bridging in joining of glass using ultra short laser pulses

Cited by 48 publications

References 17 publications

Avoiding the requirement for pre-existing optical contact during picosecond laser glass-to-glass welding

Avoiding the requirement for pre-existing optical contact during picosecond laser glass-to-glass welding

Bonding Strength of a Glass Microfluidic Device Fabricated by Femtosecond Laser Micromachining and Direct Welding

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

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