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CN-121989549-A - Graphene printing screen

CN121989549ACN 121989549 ACN121989549 ACN 121989549ACN-121989549-A

Abstract

A printing screen for Surface Mount Technology (SMT) applications, comprising at least in part graphene, optionally in the form of carbon nanotubes.

Inventors

  • WILLIAM THOMAS LUKE WALKER
  • CLIVE HOWARD CHARLES ASHMORE

Assignees

  • 先进装配系统新加坡有限公司

Dates

Publication Date
20260508
Application Date
20251022
Priority Date
20241106

Claims (20)

  1. 1. A foil for printing a screen comprising graphene.
  2. 2. Foil according to claim 1, comprising graphene sheets of doped or undoped type.
  3. 3. Foil according to claim 1, wherein the graphene is at least partly in the form of carbon nanotubes.
  4. 4. Foil according to claim 1, wherein the graphene is doped with a dopant material.
  5. 5. The foil of claim 4, wherein the dopant material comprises one of fluorine and nitrogen.
  6. 6. Foil according to claim 4, wherein the concentration of the dopant is in the range of 0.5 to 6%, optionally in the range of 2 to 4%, optionally about 3.5% by atomic percent.
  7. 7. Foil according to claim 2, wherein the sheet is fixed on at least one layer of a substrate, the substrate being different from graphene.
  8. 8. The foil of claim 7, wherein the substrate comprises one of nickel, stainless steel, and alloys of nickel and stainless steel.
  9. 9. Foil according to claim 1, wherein the foil is mounted on a mesh sheet.
  10. 10. A foil according to claim 1, comprising edge members adjacent each side of the foil.
  11. 11. Foil according to claim 10, wherein the edge member comprises jaws clamping edges of the foil.
  12. 12. Foil according to claim 10, wherein the foil comprises a plurality of sides, adjacent each side of the foil being provided with attachment means, each attachment means being for connection, in use, with the edge member.
  13. 13. Foil according to claim 12, wherein the attachment means comprises an opening formed near each of the sides of the foil.
  14. 14. Foil according to claim 13, wherein the edge member comprises fingers extending through the respective openings.
  15. 15. A printing screen comprising a foil according to claim 1, the foil having at least one aperture formed therein, the aperture extending through the foil.
  16. 16. The printing screen of claim 15, wherein the at least one aperture has a perimeter on one side of the printing screen that is greater than a perimeter of the at least one aperture on the other side of the printing screen.
  17. 17. The printing screen of claim 15, comprising a plurality of apertures formed in a regular array to form a mesh region within the printing screen.
  18. 18. The printing screen of claim 15, which is coated with a hydrophobic coating.
  19. 19. A method of manufacturing a foil for a printing screen by forming a sheet comprising graphene.
  20. 20. The method of claim 19, wherein the sheet comprises doped or undoped graphene.

Description

Graphene printing screen Technical Field The present invention relates to a foil for a printing screen, a method of manufacturing a foil and a method of manufacturing a printing screen. Background Typically, industrial screen printers apply a conductive print medium (e.g., solder paste, silver paste, or conductive ink) to a planar workpiece (e.g., a circuit board) by applying the conductive print medium through a pattern of holes in a thin planar layer or mask (e.g., stencil or screen). A stencil is a patterned solid material, such as stainless steel, nickel, or a less common plastic material, in the form of a generally planar sheet of material including apertures for defining the pattern to be printed. For ease of understanding, if holes have not been formed in the sheet, it is often referred to as "foil" (see below). The stencil is used to print directly on a printed circuit board (contact printing). The image in the master consists of holes (laser cut, chemical etched or electroformed) through the sheet. Meanwhile, the wire mesh is a mesh material including a flexible porous sheet such as a mesh woven from polypropylene, polyester or stainless steel strands. The emulsion is then applied to the web, and the image is then exposed by a camera or light source. There is a certain spacing between the screen and the workpiece (non-contact printing) to allow the web to contact the printing surface as the squeegee passes. In general, stencils can produce higher quality printing than silk screens, but silk screens also have advantages such as reusability and the ability to print features such as elongated strips (as may be required in solar panel manufacture) or loops, which the stencil cannot perform. The present invention is equally applicable to screen printing and stencil printing. In fact, the present invention provides a mixture of these two printing modes. For convenience, in the remainder of this document, the term "printing screen" will be used to refer to any such patterned mask. The term "foil" will be used to describe an unpatterned sheet to which holes may be provided to form a printing screen. Importantly, the term "foil" includes both continuous sheets and mesh sheets, such as (but not limited to) sheets formed by braiding strands together. In both forms, tension must be applied to the printing screen, typically by removably attaching the printing screen to a rectangular tension frame. The print medium is coated using a beveled blade or squeegee. The same machine may also be used to print certain non-conductive media (e.g., glue or other adhesive) onto the workpiece. However, as described above, although the stencil can provide a high quality printing effect, thereby enabling printing of very fine feature, it is impossible to print some types of feature, such as the aforementioned long line-shaped or ring-shaped feature, using the stencil. Furthermore, even with existing templates, there is a limit to the minimum feature size that can be reliably printed. In general, the smaller the feature, the thinner the stencil required, which obviously reduces the strength of the stencil. Disclosure of Invention The present invention aims to overcome the above problems and to provide a printing screen which is greatly improved and which maintains high strength even at very low thicknesses. Furthermore, the printing screen according to the invention can be used to combine the features of templates and screens to create a "hybrid" printing screen so that all types of features can be printed with high quality. According to the invention, this object is achieved by forming a sheet of a printing screen at least partly using graphene, which has not previously been proposed for such applications, nor is it known how to use such a material for such applications. According to a first aspect of the present invention there is provided a foil for a printing screen comprising graphene. According to a second aspect of the present invention there is provided a printing screen comprising a foil according to the first aspect. According to a third aspect of the present invention there is provided a method of making a foil for printing a screen by forming a sheet comprising graphene. According to a fourth aspect of the present invention, there is provided a method of making a printing screen, comprising the steps of: i) Manufacturing a foil using the method according to the third aspect, and Ii) forming at least one hole in the foil. Other specific aspects and features of the present invention are set out in the appended claims. Drawings The invention will now be described with reference to the accompanying drawings (not to scale), in which: fig. 1A schematically shows a printing screen according to the present invention in a perspective view. Fig. 1B schematically illustrates a portion of the printing screen of fig. 1A in a cross-sectional view. Fig. 2 schematically shows a part of a printing screen according to a second embodim