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TEAR ZIP CONVERTING METHOD

IP.com Disclosure Number: IPCOM000030314D
Publication Date: 2004-Aug-05
Document File: 4 page(s) / 150K

Publishing Venue

The IP.com Prior Art Database

Abstract

Current methods to convert wide web flexible circuits to narrow web typically involve chemically etching the plastic substrate material to create a channel or traditional slitting techniques. This invention is a method for converting wide web plastic films having metal features to multiple narrow web films. This method will work on any type of metal-patterned plastic film materials in which the plastic allows tear propagation and the metal provides enough resistance to confine the tearing to the tear zip feature. An example of a suitable film is a polymer film, such as a thin polyimide, patterned with copper features, as is typically used to form flexible circuits. The invention provides a method of photolithographically defining a boundary that allows for tearing the film in a precise location. By utilizing the tear propagation properties of the plastic, a metal-patterned film can be converted from wide web to narrow web by simply tearing the web along the defined boundaries. A single tear zip feature may be used to separate adjacent areas of patterned material or to remove an edge "weed" portion. Alternatively, two tear zip features may be used in an interior portion of a web to remove a weed strip from between two areas of patterned material, as is illustrated in Fig. 1 (in which the weed portion has not been separated) and Fig. 2 (in which the weed portion has been separated).

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Current methods to convert wide web flexible circuits to narrow web typically involve chemically etching the plastic substrate material to create a channel or traditional slitting techniques.

This invention is a method for converting wide web plastic films having metal features to multiple narrow web films. This method will work on any type of metal-patterned plastic film materials in which the plastic allows tear propagation and the metal provides enough resistance to confine the tearing to the tear zip feature.  An example of a suitable film is a polymer film, such as a thin polyimide, patterned with copper features, as is typically used to form flexible circuits.

The invention provides a method of photolithographically defining a boundary that allows for tearing the film in a precise location.  By utilizing the tear propagation properties of the plastic, a metal-patterned film can be converted from wide web to narrow web by simply tearing the web along the defined boundaries.  A single tear zip feature may be used to separate adjacent areas of patterned material or to remove an edge “weed” portion.  Alternatively, two tear zip features may be used in an interior portion of a web to remove a weed strip from between two areas of patterned material, as is illustrated in Fig. 1 (in which the weed portion has not been separated) and Fig. 2 (in which the weed portion has been separated).

Fig. 1

 

Fig. 2

An advantage of using the tear zip technique can include lower unit cost, higher yield, lower cycle time, and fewer defects than in other converting processes. It can also provide a robust web that can survive handling, high precision of edge location, small amount of debris generated, and fewer edge quality issues.

Photolithography is a well-known method used to define the flexible circuit patterns.  For example, photolithography can be used to define a copper circuit pattern on a polyimide substrate.  Photolithography may be used in a subtractive or an additive process to make such a flexible circuit.

 In an additive process, a photosensitive resist layer is laminated or coated onto the substrate.  The substrate may have a seed layer or tie layer already applied to it.  Next, a mask having a negative pattern of the desired copper circuit is placed over the photoresist.  The exposed areas of photoresist are then subjected to radiation, which causes the photoresist to crosslink.  The mask is removed and the uncrosslinked portion of the photoresist is stripped using a suitable solvent.  Then copper is deposited or plated in the pattern openings.  The remaining resist is then removed as is any exposed areas of a seed or tie layer. 

In a subtractive process, a copper layer is first applied to the substrate, then a photo-sensitive resist layer is laminated or coated onto the copper layer.  Next, a mask having a positive pattern of the desired copper circuit is placed over the photoresist.  The exposed areas o...