Browse Prior Art Database

Screening Method for Thin, Protective Coatings

IP.com Disclosure Number: IPCOM000120569D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Lanzetta, AP: AUTHOR [+5]

Abstract

Disclosed is a method for screening extremely thin coatings for the corrosion protection of flex circuits or other applications. The limitations of widely available screening stencils and meshes make it difficult to achieve a coating thinner than about 40 mm. A thick coating, in turn, can complicate subsequent process steps like forming and bonding. A thinner coating is also preferable because it contributes less to the composite mechanical properties of the flex, e.g., during thermal cycling. By using a custom-designed screener and polymer, thin coatings were obtained and process control was improved.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 67% of the total text.

Screening Method for Thin, Protective Coatings

      Disclosed is a method for screening extremely thin
coatings for the corrosion protection of flex circuits or other
applications.  The limitations of widely available screening stencils
and meshes make it difficult to achieve a coating thinner than about
40 mm.  A thick coating, in turn, can complicate subsequent process
steps like forming and bonding.  A thinner coating is also preferable
because it contributes less to the composite mechanical properties of
the flex, e.g., during thermal cycling.  By using a custom-designed
screener and polymer, thin coatings were obtained and process control
was improved.

      Silk-screening stencils typically consist of a woven mesh, with
an emulsion of finite thickness adhered to the underside (see Fig.
1).  The emulsion has openings which define the pattern to be
screened, and the polymeric "ink" is applied from the top side with a
squeegee.  The amount of material transferred to the part underneath
is a function of the speed and pressure of the squeegee, rheological
properties of the ink, and the geometry of the stencil.  The amount
of ink trapped in the stencil opening and transferred to the part
will be governed by the screen mesh size and weave and the emulsion
thickness.  Consequently, in order to transfer a minimum amount of
material, a mesh with small wires, tightly woven, and a minimum
emulsion thickness should be used.  Ideally, the emulsion would be in
the...