Laser drilling of holes in materials with different thermal properties

Uglov, A. A.; Kokora, A. N.; Orekhov, N V

doi:10.1070/qe1976v006n03abeh011007

Cited by 11 publications

(4 citation statements)

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“…Our system makes use of a short free-running laser pulse with an intensity seven times smaller than the LSD threshold. The expulsion of the liquid is believed to be due to the recoil pressure [5] from the rapid vaporization of a thin layer of the liquid. The increase in the drilling efficiency is partially due to the fact that the latent heat of vaporization has not been expended on this molten liquid [9].…”

Section: Discussionmentioning

confidence: 99%

“…Pulse 2 has a higher peak power and much lower energy. It removes the molten materials by means of the recoil pressure generated by rapid vaporization of the molten liquid [5][6][7][8][9]. The amount of material removed will depend on the quantity of liquid present when pulse 2 is fired.…”

Section: Discussionmentioning

confidence: 99%

“…The amount of material ejected in the liquid state has a direct effect on the laser drilling/cutting efficiency due to the fact that the material is removed without the loss of additional energy required for vaporization. Many theoretical models have been developed in an attempt to characterize the dynamics of the laser drilling process [5][6][7][8][9].…”

Section: Pacs: ; ;Ce Amentioning

confidence: 99%

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Enhanced drilling using a dual-pulse Nd:YAG laser

Lehane

Kwok

2001

Appl Phys A

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Abstract.A new method for improving the efficiency of laser drilling has been developed. Two synchronized free-running laser pulses from a tandem-head Nd:YAG laser are capable of drilling through 1/8-in-thick stainless-steel targets at a standoff distance of 1 m without gas-assist. The combination of a high-energy laser pulse for melting with a properly tailored high-intensity laser pulse for liquid expulsion results in the efficient drilling of metal targets. We argue that the improvement in drilling is due to the recoil pressure generated by rapid evaporation of the molten material by the second laser pulse. PACS: ; ;CE aLaser drilling and cutting of metals are established industrial processes. They are applied in many different production lines. There have been some attempts to understand the laser-material interaction process with the aim of improving the efficiency of laser drilling and cutting [1][2][3][4]. It has been found that material is removed in both the vapor and the liquid states. The intense laser energy used for laser drilling is sufficient to melt and subsequently vaporize the material. This vaporization process creates a recoil pressure, which is responsible for expelling the liquid. The amount of material ejected in the liquid state has a direct effect on the laser drilling/cutting efficiency due to the fact that the material is removed without the loss of additional energy required for vaporization. Many theoretical models have been developed in an attempt to characterize the dynamics of the laser drilling process [5][6][7][8][9].In most instances, a gas jet is used to assist the drilling/ cutting of the material. In the case of stand-off drilling/cutting at a distance without gas-assist, the efficiency is rather low. The problem is due to resolidification of the molten pool. Increasing the laser power does not work well. Several novel methods for improving the efficiency of material removal in laser drilling have been developed. Fox [10] combined a cw CO 2 laser with Q-switched Nd:glass laser pulses to * Corresponding author. (E-mail: eekwok@usthk.ust.hk) achieve a factor of two increase in the drilling efficiency of carbon steel. The Q-switched pulse was responsible for the ejection of liquid metal, which had not yet consumed the latent heat of vaporization, resulting in a higher drilling efficiency. This experiment was theoretically modeled by Robin and Nordin [11] and Towle et al. [12]. Another novel technique was reported by Kim et al. [13]. They reported that the laser penetration efficiency was enhanced by amplitudemodulating a free-running Nd:YAG laser. They attributed this improvement to a reduction in the plasma screening effect due to the repetitive chopping of the laser beam, along with possible acoustic resonance effects of the molten metal.In this paper, we propose and demonstrate a new method for increasing laser drilling efficiency using two synchronized free-running Nd:YAG laser pulses. We show that a Qswitched pulse is not necessary for explosive liquid expulsion. In fact, ...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Pacs: ; ;Ce Amentioning

confidence: 99%

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Enhanced drilling using a dual-pulse Nd:YAG laser

Lehane

Kwok

2001

Appl Phys A

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“…The laser has good monochromaticity and directionality, as well as high energy. It can transfer photon energy of the laser light to glass, then melt the material and remove the material through vaporization or sublimation, then make a via hole [24,25,26].…”

Section: Methodsmentioning

confidence: 99%

Research on Wafer-Level MEMS Packaging with Through-Glass Vias

et al. 2018

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A MEMS fabrication process with through-glass vias (TGVs) by laser drilling was presented, and reliability concerns about MEMS packaging with TGV, likes debris and via metallization, were overcome. The via drilling process on Pyrex 7740 glasses was studied using a picosecond laser with a wavelength of 532 nm. TGVs were tapered, the minimum inlet diameter of via holes on 300 μm glasses was 90 μm, and the relative outlet diameter is 48 μm. It took about 9 h and 58 min for drilling 4874 via holes on a four-inch wafer. Debris in ablation was collected only on the laser inlet side, and the outlet side was clean enough for bonding. The glass with TGVs was anodically bonded to silicon structures of MEMS sensors for packaging, electron beam evaporated metal was used to cover the bottom, the side, and the surface of via holes for vertical electrical interconnections. The metal was directly contacted to silicon with low contact resistance. A MEMS gyroscope was made in this way, and the getter was used for vacuum maintenance. The vacuum degree maintained under 1 Pa for more than two years. The proposed MEMS fabrication flow with a simple process and low cost is very suitable for mass production in industry.

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Laser Techniques

Agajanian¹

1979

Microelectronic Packaging

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Laser drilling of holes in materials with different thermal properties

Cited by 11 publications

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Enhanced drilling using a dual-pulse Nd:YAG laser

Enhanced drilling using a dual-pulse Nd:YAG laser

Research on Wafer-Level MEMS Packaging with Through-Glass Vias

Laser Techniques

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