Laser micromachining of permalloy for fine metal mask

Abstract

We show that crack-free drilled structures with 25 µm hole size can be fabricated in the 12 µm-thick Permalloy foil by a nanosecond ultraviolet laser with low pulse energy and high repetition rate. The number of pulses required for drilling decreased with increasing pulse energy. The obtained hole exhibited a smaller size than the laser spot, implying that only the central part of a focused Gaussian beam contributed to the drilling. Debris and burr incurring as a result of the laser micromachining could be quickly removed by etching in an HCl/HNO 3 solution. This made it possible to obtain a clear structure without any debris remaining on the foil. This laserdirect process may be effectively utilized for fabricating fine metal masks necessary for the production of organic light emitting diode displays and other electronic devices.

Low-Power, Multimodal Laser Micromachining of Materials for Applications in sub-5 µm Shadow Masks and sub-10 µm Interdigitated Electrodes (IDEs) Fabrication

“…In the case of RIE multi-wafer/multi-substrate parallel processing is also possible as with some laser micromachining examples as well for higher throughput micro/nanofabrication. Laser micromachining has occasionally been used for shadow mask fabrication; however, the state of the art in laser micromachining (minimum feature size of 10 µm) [23] (to date) has relied entirely on single-wavelength excimer, CO 2 , and Nd:YAG (neodymium-doped yttrium aluminum garnet) lasers [1,3,12,[23][24][25][26][27][28][29][30][31][32][33][34][35][36]. To the best of our knowledge, multimodal laser micromachining has not been used for shadow mask fabrication.…”

“…The lasers used in the aforementioned research can produce shadow masks for MEMS applications, but they are unable to micromachine highly precise features on the scale of a single micron, unless they operate in the femtosecond regime [3,7,23,24,30,37]. The higher power of these lasers allows for the processing of thicker materials in a more reasonable time scale; however, this capability comes at the price of benchtop machining, high costs, space, high power usage (GW), and absence of multimodality to micromachine several materials with the same tool.…”

75‐4: Invited Paper: FMM Materials and Manufacturing Process: Review of the Technical Issues

“…In order to implement the UHD display, UHD FMM (Fine Metal Mask) should be developed, which is utilized as a shadow mask in red, green and blue organic materials evaporation process. [2][3][4][5] In this digest, we would like to review the technical issues on materials and manufacturing process of FMM, and suggest some solutions for UHD FMM.…”

“…In addition, it is difficult to produce a uniform and low taper angle except for few report2), and there is a problem of having a rough taper surface unique to laser processing. [3][4][5] In order to planarize the rough slopes, chemical or electrochemical etching has to be carried out, but until now, only the physical particles adhering to the surface have been removed. It has not yet been reported to planarize the slopes without changing the activated pattern size.…”

Microstructure-based analysis of fine metal mask cleaning in organic light emitting diode display manufacturing

“…The thin metal sheet includes tiny openings formed by electroforming or micro photo etching of stainless steel or Invar (64% Fe-36% Ni alloy). The thin metal sheet of the FMM is only 30-200 μm [6,7]. Due to its limited ductility and low thickness, it is extremely difficult to keep the FMM aligned and attached to the TFT back plane with high positional accuracy, so the thin metal sheet needs to be stretched and supported by a thick metal frame using laser welding.…”