Method of making mandrels for use in a deposition process

Abstract: A reusuable mandrel (1,9) and method of making a reusuable mandrel (1-9) is presented. This mandrel (1-9) has a substrate (1-7) with a conductive film layer (1-3). Upon the conductive film layer (1-3) a dielectric mold resides (1-1). An etched thin film mandrel (5-9) is also presented. This mandrel (5-9) has a substrate (5-5) covered with a conductive film layer (5-3). This conductive film layer (5-3) is etched to form a mold for the device to be manufactured. These mandrels are used by deposition of a metallIc layer thereon. The metallic layer is stripped from the reusuable mandrel; the thin film mandrel (5-9) becomes part of the product. In particular, they can be used to manufacture orifice plates for thermal ink jet printers.

Description: Field of the Invention The invention relates to the field of electroplating. In particular, this invention relates to the field of manufacturing mandrels using thin film processes. Additionally, this invention manufactures devices by electroforming a metal layer on to the mandrel. Background of the Invention U.S Patent No 3.703.450 describes a method for making a precision conductive mesh screen. First, this method constructs a mandrel. The prior-art mandrel is. constructed by placing a master plate with the screen pattern on the glass substrate and by vapor depositing a thin film through the interstices of the master plate to form the screen's pattern on the glass. After removing the master plate from the glass substrate, the method deposits photoresist over the entire glass plate. Next, the method exposes and oevelops the photoresist to produce a layer of thin film in a screen pattern covered with a layer of photoresist in the same screen pattern. Next, the method deposits silicon monoxide on the entire glass substrate and removes the silicon monoxide and photoresist from the thin film pattern. This non-reusable mandrel is now ready for manufacturing the screen. This prior-art mandrel has several disadvantages. It cannot manufacture small geometry devices as pointed out in US Patent No 4,549,939 discussed below Also, the complicated prior-art process for making this mandrel has low yields. U.S. Patent No 4.549.939 and EP 0 163 130 describe another type of prior-art thin film mandrel and the method of making it. This prior-art process constructs the prior-art mandrel by forming a stained pattern shield on a glass substrate and depositing a conducive and transparent thin film onto the substrate. Next, the prior-art method coats the thin film with resist and shines a light through the glass substrate and the transparent thin film to expose the unshielded photoresist. Finally, the photoresist is developed and forms the mold for electroforming. The prior-art mandrel formed by this process has several disadvantages. It is non-reusable and of poor quality due to resist broken after the electro-forming cycle. Additionally, it requires the use of a conductive thin film that is transparent; a costly and exotic material. U.S. Patent No. 4.528.577 describes another prior-art mandrel and the method of making it. This prior-art method of manufacturing orifice plates for thermal ink jet printheads electroforms nickel onto a stainless steel mandrel plate that contains either a pre-etched orifice pattern or a photoresist orifice pattern. Unfortunately, stainless steel mandrel plates always contain a large number of scratches and defects. These scratches and defects arise from characteristics of the stainless steel material and from the manufacturing process. The scratches and defects, which can not be eliminated, degrade the quality of the orifice plates manufactured from stainless steel mandrels. These inferior orifice plates produce inferior print quality. The method and apparatus in accordance with the present invention obviate these problems with mandrels in the prior art. JP-A-53 83 864 discloses a method of making a mandrel, comprising the steps of depositing a conductive layer on a substrate; depositing a photoresist layer on the conductive layer; and etching the conductive layer to form a mandrel comprising a pattern of projections on the surface of the substrate. The photoresist is printed on to the conductive layer in a pattern corresponding to the pattern of projections. According to the invention there is provided a thin film method of making a mandrel as specified in claim 1. According to the present invention, the reusable mandrel has a glass substrate with a conductive film layer and dielectric layer. Next, the method forms a mold by depositing a dielectric film on the metalized substrate, by using a standard photolithography process to define a resist pattern on the dielectric film, and by removing the unmasked dielectric film with a plasma etching process. Finally, the method strips the photoresist away and the mandrel is ready to use. A thin film mandrel has the advantage of producing high quality precision devices. This advantage results from the defect free surface of the thin film and the precision molds created by standard photolithography and etching processes. Additionally, the thin film mandrel has the advantage of producing high quality precision devices cheaply. This advantage results from the low cost procedures used to produce the mandrel and the low cost procedures for using the mandrel. The thin film mandrels are capable of producing a wide variety of devices. Devices traditionally manufactured by precision machining techniques such as laser machining, mechanical machining, and chemical etching can be manufactured by an electroforming process using the thin film mandrel. The electroforming process using the thin film mandrel produces devices having the same or better quality as those produced by precision machining and the thin film process produces the devices at a much lower cost. Ink jet printhead performance depends on the quality of the orifice plates. High quality orifices yield high quality printing. Thus, this invention has the advantage of producing high quality precision orifice plates for ink jet printers that result in higher print quality. Additionally, the thin film mandrel can be used to manufacture components for other types of printers or for medical devices. Brief Description of the Drawings Figures 1A - 1B show a reusable mandrel. Figures 2A - 2G show the steps used to manufacture a reusable mandrel. Figures 3A - 3B show a device being manufactured by the reusable mandrel. Figures 4A - 4C show an orifice plate being manufactured by the reusable mandrel. Figures 1A and 1B show the reusable mandrel 1-9. It has a conductive thin film layer 1-3 deposited on a glass substrate 1-7. This conductive thin film 1-3 can range from 10 nanometres (100 Angstroms) to 200 micrometres (200 microns). The film layer 1-3 has a layer of chrome 1-11 and a layer of stainless steel 1-5. The chrome layer 1-11 bonds firmly to the substrate 1-7 and provides a surface that the stainless steel layer 1-5 can adhere to. A dielectric layer 1-1 resides on top of the film layer 1-3. This dielectric layer 1-1 has been patterned and-etched to form a mold. The process for manufacturing a reusable mandrel shown in Figures 2A-2G starts with a glass substrate 2-1 as shown in Figure 2A. A vacuum deposition process, such as the planar magnetron process, deposits a conductive thin film 2-3. This thin film 2-3 is constructed from chrome and stainless steel materials. Another vacuum deposition process deposits a dielectric layer 2-5 on to the thin film layer 2-3. Alternatively, the dielectric layer may be deposited by spin coating. The preferred embodiment of the present invention uses a plasma enhanced chemical vapor deposition process to deposit a dielectric layer 2-5 of silicon nitride. However, alternate embodiments could use different nonconductive materials. Next, a photoresist layer 2-7 is applied to the dielectric layer 2-5. Depending on the photomask 2-11, either positive or negative photoresist is applied to the dielectric layer 2-5. Next, the photomask 2-11 is placed next to the photoresist layer 2-7 and exposed to ultra violet light as shown in Figure 2E. Next, the photoresist layer 2-7 is developed to obtain the photomask 2-11 pattern into the photoresist layer 2-7. This patterned photoresist layer 2-7 serves as a mask for the dielectric layer 2-5. Next, an etching process, such as plasma etching, removes the unmasked dielectric film 2-5. Aher removing the remaining photoresist, the reusable mandrel 2-9 has a patterned dielectric layer 2-13 resting on a stainless steel layer 2-3 as shown in Figure 2G. This reusable mandrel is ready for fabricating devices. In order to manufacture a device using the reusable mandrel, insert the mandrel into an electroforming bath 3-1 shown in Figure 3A. This reusable mandrel becomes the cathode 3-9. The source material plate 3-5 which supplies the electroforming material is the anode. In the preferred embodiment of the invention, the metal plate 3-5 is composed of nickel. During the electroforming process metal is transferred from the anode metal plate 3-5 to the cathode mandrel 3-9. The metal attaches to the conductive areas of the cathode mandrel 3-9. Thus, metal attaches to the conductive film layer 3-11, but not to the patterned dielectric areas 3-13. The electroforming process is continued until the device 3-7 has the desired thickness. When that point is reached, the device 3-7 is separated from the cathode mandrel 3-9 as shown in Figure 3B. A reusable mandrel 4-9 for fabricating orifice plates 4-7 is shown in Figure 4A. The mandrel 4-9 has a chrome stainless steel thin film 4-3 (not shown in Figure 3B). Upon this film 4-3 lies the silicon nitride pattern 4-5 for forming the orifice plates 4-7. Once this mandrel has been formed, the orifice plate 4-7 is formed as shown in Figure 4B. Figure 4C shows a cross section of the orifice plate 4-7 with the orifice 4-1.

Claims: A thin-film method of making a mandrel (1-9) for use in a deposition process, comprising the steps of depositing a conductive layer (2-3) on a glass substrate (1-7), formed by a chrome layer (1-11) on the substrate and a stainless steel layer (1-5) on the chrome layer; depositing a dielectric layer (2-5) on the stainless steel layer; depositing a photoresist layer (2-7) on the dielectric layer; exposing and developing the photoresist; and etching the dielectric layer through the resulting patterned layer to form a reusable mandrel comprising a pattern of projections (1-1) on the surface of the stainless steel layer (1-5). A method as claimed in claim 1, wherein the conductive layer (2-3) is deposited by vapour deposition. A method of producing an apertured product comprising producing a mandrel (4-3) by the method of any of claims 1 to 2, depositing metal (4-7) over the mandrel such that a layer is formed which has apertures over the projections (4-5) and stripping the layer off the mandrel (4-3).

Inventors: SI-TY LAM, WEBERG GLENN, SI-TY, LAM, WEBERG, GLENN
Applicants: HEWLETT PACKARD CO, HEWLETT-PACKARD COMPANY
Application year: 1987
Main classification: C25D1
IPC codes: C25D1, B41J2