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Method for a UV curable, low dielectric material for the preparation of substrates by an imprinting process

IP.com Disclosure Number: IPCOM000100640D
Publication Date: 2005-Mar-15
Document File: 4 page(s) / 63K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for an ultraviolet (UV) curable, low dielectric material for the preparation of substrates by an imprinting process. Benefits include improved functionality, improved yield, improved process simplification, and improved ease of manufacturing.

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Method for a UV curable, low dielectric material for the preparation of substrates by an imprinting process

Disclosed is a method for an ultraviolet (UV) curable, low dielectric material for the preparation of substrates by an imprinting process. Benefits include improved functionality, improved yield, improved process simplification, and improved ease of manufacturing.

Background

      Conventional dielectric film materials cure too slowly under typical imprinting processes and during the subsequent thermal cure. As a result, the imprinted features are lost or very degraded.

      For manufacturing substrates by imprinting, the dielectric film is processed at a pressure of 300 psi for about 1 minute. During that time, the temperature is rapidly ramped to 165° and then decreased to below 100°C for mold opening. The temperature drop prevents the low molecular weight material from sticking to the microtool.

      After imprinting, the film is cured at about 170°C for 90 minutes (see Figure 1). During that time, many of the features are lost or are distorted due to material flow at elevated temperatures prior to achieving sufficient cure. To avoid the problem of lost features, the film can be partially cured prior to imprinting. However, this procedure leads to poor images in the film because the imprinted features are not as deep and well defined. The imprinting process can be extended to provide 5 to 15 minutes at 165°C. However, the long imprinting times are not feasible for high-volume manufacturing due to the cost and throughput concerns.

      Conventional substrate manufacturing plates a layer of copper on a thermosetting epoxy dielectric film. The circuitry is obtained by using a sacrificial photo-definable layer, which after being developed serves as the mask for etching the exposed copper and dielectric material. In the final step, the photo-definable layer is removed.

      Experimental efforts showed that thermoplastic materials do not allow construction of multilayer substrates. A lower melting point, thermoplastic would be required for each subsequent layer, which becomes problematic with 6-layer to 12-layer substrates.

              Typically, UV-curable formulations comprise acrylate monomers and UV-activated catalysts. High molecular weigh acrylics, such as polymethylmethacrylate (PMMA), are useful thermoplastics. However, monomers are liquid at room temperature and are not film forming. Additionally, the cured polymer has a low glass transition temperature (Tg) of 100°C and a very low melting point of 150°C. The polymer does not maintain its shape during reflow at 200-260°C. To increase the Tg and provide thermosetting properties, bis-acrylates comprising rod-shaped liquid crystalline segments, such as monomer N2, can be prepared. This material has most of the required properties, except that the dielectric constant of the cured polymer is too high (4-9 depending on orientation).

General description...