Printing screen and method

Abstract

A printing screen has a first metallic layer that is electroformed and has a number of apertures in the metallic layer. A second metallic layer is electroformed over the first metallic layer. The second metallic layer forms a frame around groups of the apertures.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a bottom view of a printing screen in accordance with one embodiment of the invention;

FIG. 2 is a cross sectional view of a printing screen in accordance with one embodiment of the invention; and

FIG. 3 is a flow chart of the steps used in manufacturing a printing screen in accordance with one embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention is directed to a printing screen for electronic circuits. The improved printing screen uses a two step electroforming process. The first metallic layer defines a plurality of apertures. The second metallic layer creates a frame around groups of the apertures. The process of producing the screen is inexpensive, can produce fine pitch apertures, does not stretch with use and does not result in the solder paste adhering to the apertures.

FIG. 1 is a bottom view of a printing screen 10 in accordance with one embodiment of the invention. The screen 10 has a first metallic layer 12 which is electroformed with a plurality of apertures or orifices 14. A second metallic layer 16 is electroformed on the first metallic layer and creates a frame around a group 18, 20, 22 of apertures. In one embodiment, a group of apertures is defined as a number of closely spaced apertures. FIG. 2 is a cross sectional view of the printing screen 10 in accordance with one embodiment of the invention. The first metallic layer 12 defines a plurality of apertures 14. A second metallic layer 16 defines a frame around a group of apertures. The second metallic layer 16 is electroformed onto the first metallic layer 12. The first metallic layer has a thickness of “t” and the second metallic layer has a thickness of “T”. In one embodiment, the thickness “t” of the first metallic layer is less than or equal to the thickness “T” of the second metallic layer. Note that a group of apertures may be a single aperture.

FIG. 3 is a flow chart of the steps used in manufacturing a printing screen in accordance with one embodiment of the invention. The process starts, step 50, by applying a pattern of resist on a conductive mandrel that defines a plurality of apertures 52. Next the first metallic layer is electroformed with the plurality of apertures at step 54. A second pattern of resist is applied on the first metallic layer at step 56. At step 58 the second metallic layer is electroformed on the first metallic layer which ends the process at step 60. In one embodiment, the second metallic layer forms a frame around a group of apertures.

Thus there has been described a printing screen that is reliable, does not stretch with use and allows for fine pitch apertures without the solder paste adhering to the apertures.

While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alterations, modifications, and variations in the appended claims.

Claims

1. A printing screen comprising: a first metallic layer electroformed having a plurality of apertures; anda second metallic layer electroformed to the first metallic layer, the second metallic layer creating a frame around a group of the plurality of apertures.

2. The printing screen of claim 1, wherein the group of the plurality of apertures is a number of closely spaced apertures.

3. The printing screen of claim 2, wherein the plurality of apertures form at least two groups.

4. The printing screen of claim 1, wherein a thickness of the second metallic layer is equal to or greater than a thickness of the first metallic layer.

5. A method of forming a printing screen, comprising the steps of: a) applying a pattern of resist on a conductive mandrel that defines a plurality of apertures;b) electroforming a first metallic layer with the plurality of apertures; andc) applying a second pattern of resist on the first metallic layer.

6. The method of claim 5, further including the step of: d) electroforming a second metallic layer on the first metallic layer.

7. The method of claim 6, wherein step (d) further includes the step of electroforming a frame around a group of the plurality of apertures.

8. The method of claim 5, wherein step (c) further includes the step of defining a frame around a group of the plurality of apertures with the second pattern of resist.

9. A printing screen comprising: a first electroformed metallic layer having a plurality of orifices; anda second metallic layer electroformed to the first electroformed metallic layer.

10. The screen of claim 9, wherein the second metallic layer forms a frame around a group of the plurality of orifices.

11. The screen of claim 10, wherein the plurality of orifices form at least two groups.

12. The screen of claim 11, wherein a thickness of the first electroformed metallic layer is less than or equal to a thickness of the second metallic layer.