DD147437A1 - METHOD OF STRUCTURING THE INSULATING LAYER OF FLEXIBLE INSULATION LAYER METAL COMPOUNDS - Google Patents

Abstract

The invention relates to a method for structuring the insulating layer of flexible insulation layer-metal composites such as in particular intermediate carrier for Filmtraegerbonden or flexible printed circuit boards. The invention solves the problem of selectively removing the insulating layer of flexible insulation layer-metal composites without damaging the metal layer, deforming it or changing its structure. It has been found that all the objects of the problem are met when the insulating layer is evaporated with a laser beam of wavelength> 2 microns, preferably 10.6 microns.

Description

217151

Int.Cl. H 01 L / 21/60

Process for Structuring the Insulation Layer of Flexible Insulation Layer-Metal Composites

Field of application of the invention

The invention relates to a method for structuring the insulation layer of flexible insulation layer-Ivletall-composites such as in particular intermediate carrier for the Filmtragerbonden or flexible printed circuit boards. ,

Characteristic of the known technical solutions

Flexible composite materials made of insulation, adhesive and metal layers have long been used in electrical engineering / electronics, eg. B. for flexible printed wiring from 1953 · Industrially, the Pilmträgerbonden of chips has prevailed with a flexible multi-layer subcarrier. These intermediate carriers consist for example of an approximately 35yum thick copper layer, an adhesive layer and an approximately 70 Aim strong polyimide, polyester or other insulating layer.

Before contacting the etched into the copper layer conductor with components, eg. For example, chips, or other conductors, the insulating layer must be removed in the region of the contacting point, and the contacting layer can be cut into the insulating layer before the layers are joined together or it can be selectively worked out of the finished composite material.

Wach the first variant can not be produced generally useful starting material. The geometry of the

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Contact window is fixed. In addition, the copper layer in the production of the layer composite in the region of the contacting window u. U. deformed. This deformation adversely affects the later process steps, or makes them impossible. Particularly at risk is the step of photolithographic structuring of the metal layer.

From the layer composite, the insulation and possibly the adhesive layer must be removed selectively, if possible without affecting the copper layer. For this purpose, various attempts or techniques have become known.

On the one hand, the insulating layer is etched out after a covering step using 98% strength sulfuric acid at about 90 ^° C. The aggressive chemicals require appropriate occupational safety measures ... Additional covering and stripping processes are required. High demands are placed on the covering varnish.

On the other hand, the insulation layer is ground down locally. The method has become known in particular for exposing flat ribbon cables. To unscrew the relatively small contacting window in the intermediate carriers, it is unsuitable, especially since it can not be prevented with certainty that the copper layer is attacked and deformed.

It was also tried to burn out the insulation layer with heated punches. The hole quality (edge, charred residues) is insufficient and a deformation of the copper layer could not be prevented here.

Since the mid-sixties, it has been known in electronics technology to use a laser to trim resistor layers on ceramic or glass substrates. The excess resistance material is evaporated. By optimizing the laser (YAG laser), it has been possible to increase the selectivity of the process. The ceramic substrate is removed only slightly, about 3 / um.

So far, this method for structuring insulation layers, in particular of insulating layers is more flexible

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Insulation layer-to-metal bonds, not used Even the slightest removal of the copper layer is sufficient to unduly alter their surface, flatness and structure.

Goal of _; invention

The object of the invention is a further method for structuring the insulating layer of flexible insulation layer metal interconnections.

Explanation of the essence of the invention

The invention solves the problem with a further method. to selectively ablate the insulating layer of flexible insulation-metal composites without damaging, deforming or altering the structure of the metal layer.

It has been found that all points of the problem are met when the insulating layer is evaporated with a laser beam of wavelength > 2 μτη, preferably 10.6 pn. Due to the different reflectivity of the insulating and adhesive layer on the one hand (r <50 %) and the metal layer on the other hand (r »99 %) , the metal layer is neither injured nor otherwise attacked in any improper manner.

embodiment

An intermediate carrier of a multilayer flexible base material with a polyester (PSTP) insulation layer ("Mylar" from Du Pont) is irradiated with a COp laser and thereby the polyester is removed. For this purpose, the beam is either guided over a predetermined program on the 'flat to be removed or it is previously placed a mask made of metal and removed by the rope.

Claims (2)

invention claim 1. A process for structuring the insulating layer of flexible insulation layer-metal composites, characterized in that the insulating layer is evaporated with a laser beam of wavelength> 2 pm . 2 * Method according to item 1, characterized in that the laser beam of wavelength 10.6 μm is used.