KR20010090726A - Method for assembling metal printed conductors as electrodes on a channel plate for ultrawide flat screens - Google Patents

Abstract

Recent ultrawide flat screens, known as PDPs and PALCs, have a micro-channel structure and a glass plate with address electrodes in each channel. To date, address electrodes selectively etch attached large-surface metal layers leaving printed conductor structures directly or without external current and / or in a galvanic manner using printing techniques or by selective sputtering along the channel structure. By indirectly attached. In order to avoid the drawbacks of the known method, the present invention provides that the metal-printed conductor as the address electrode is optionally attached to the electrode region using only an attachment method without external current and / or in a galvanic manner.

Description

METHOD FOR ASSEMBLING METAL PRINTED CONDUCTORS AS ELECTRODES ON A CHANNEL PLATE FOR ULTRAWIDE FLAT SCREENS}

Modern large-screen flat panel display panels, such as plasma display panels (PDPs) and plasma-addressed liquid crystal displays (PALCs), require channel plates made of glass for operation. The plate is provided with channels formed by ridges, also called barriers or separators, and are provided as address electrodes with a limited number of conducting paths extending vertically (for PDPs) or horizontally (for PALCs). These electrodes are attached between the rib-shaped ridges, which are made after the electrode is formed or are formed in advance on the glass substrate. 1 shows a typical example of such a channel plate.

The construction of modern flat panel displays, in particular channel plates, is widely described in the literature.

Attaching address electrodes is problematic because of the microstructure of the channel plate—the distance between the rib-shaped ridges, ie the channel width, also called pitch, is in the range of 100 to 600 μm.

Japanese Patent 95-077892 describes a process in which an address electrode is formed on a channel plate by attaching a metalloid paste in accordance with a structure through silk screen printing or other printing process. The main disadvantage of this prior art is the inadequate resolution of the applicable printing process and the high price of the metal-containing printing paste, which prevents cost-effective manufacturing of large-screen flat panel displays. Moreover, this process is only suitable for attaching electrodes to flat glass substrates that do not yet have ridges.

US patent application 4,359,663 describes a process for attaching an address electrode to a channel by sputtering a desired electrode material onto a glass substrate. The practical disadvantages of this sputtering process are the high production costs and the relatively low substrate throughput resulting from the high capital investment.

Japanese Patent Application No. 8-222128 describes a process of attaching an electrode to a channel plate for display through an electroless and galvanic process in which a metal film is attached to the entire portion of the display. Since the electrode occupies 5-20% of the display area, the remaining 95-80% of the display area must be etched after full-area attachment for electrode formation according to the structure. Thus, this process improperly uses the metal components of the electroplating bath. As a result, metal-containing or heavy metal-containing waste is produced, which is expensive. Moreover, here only the single transparent conductor layer (ITO) is mentioned as the base. However, this layer can be attached only by vacuum treatment (sputtering or evaporation) so that the advantage of forming the metal layer from the liquid state is partially reduced.

The present invention relates to a process using an electroless and galvanic metal deposition process and attaching a metallic conductor path as an electrode to a channel plate for a large-screen flat panel display panel.

It is an object of the present invention, on the basis of this process mentioned at the outset, to reduce the consumption of metals to be deposited, to eliminate additional etching treatment steps and associated hazardous wastes, to avoid costly vacuuming, and to process the process cost effectively. To do.

According to the invention, this object is achieved in that the metallic conducting path is selectively attached only to the electrode region via an electrless and / or galvanic deposition process.

The process according to the invention uses selective electroless metal deposition and galvanic metal deposition (without application of current), ie selective attachment from the liquid state. Compared to vacuum processing (eg sputtering or deposition), this process is cost-effective because it provides high substrate throughput at low investment costs. Moreover, compared to high vacuum technology, the clean room rating requirements are practically looser. The process according to the invention has these advantages, in particular, in that the full-region metallization does not occur as in the case of the Japanese patent application, and the electronic path is selectively formed depending on the structure of the glass substrate. This reduces metal consumption by at least 10. Moreover, no subsequent etching step is required as in the process according to the above Japanese patent application. It does not require such treatment steps, and the process according to the invention also does not yield expensive metal-containing or heavy metal-containing waste.

In other technical fields, for example, contact decks or conductive paths for microcircuits of planar electronic components such as LCD cells, etc., are known, in particular using a laser beam to attach metal layers depending on the structure to the substrate. have.

Typically, large-area metallization is selectively attached and removed by masking. However, this process is not suitable for attaching electrodes for PDP or PALC, since it requires a large area of metallization of 42 inches or more diagonally. In addition, it is uneconomical to form a metal layer in conformity with the structure of a large-area substrate by laser.

Moreover, the sides of the barrier ribs cannot be easily exposed to laser light, making it impossible to remove the protective layer as desired. However, in the production of PDP or PALC channel plates it is required that all metals be removed completely along the side of the rib-shaped ridges.

EP 534 576 B1 further describes a process for selectively attaching a conductive path for an electronic circuit to a glass substrate, wherein a mask having a negative shape of the path structure to be attached is a beam path of an excimer laser. ). The laser beam from the mask goes to a flat quartz glass substrate, the rear side of which is in contact with a reductive copper bath. This allows laser induced thin copper paths to be selectively attached according to the desired structure, structure. This process is again not suitable for large-area glass substrates, such as channel plates, as it requires the use of lasers, moreover special lasers. Moreover, expensive quartz glass should be used here, since only this type of glass can transmit the light of the excimer laser required and allows for selective backside copper attachment.

In contrast to these methods, the process according to the invention uses only those processes that are suitable for large surfaces without using vacuum techniques for the formation of selective address electrodes. Moreover, this process does not require a transparent conductive layer or quartz glass or laser as the base layer. In addition, the process according to the invention can easily be used for channel plates already equipped with rib-shaped ridges or barrier ribs.

The process according to the invention has particular advantages for the channel structure of PDP / PALC panels, since homogeneous metallization of the channel walls is also possible.

Roughening the substrate is also advantageous because it improves tack.

Moreover, it is possible in the present invention to use all metals and metal alloys suitable for attachment in the form of a single material or multilayer, with or without the application of current.

When making printed circuit boards for electronic products or glass substrates for electronic circuits, the use of selective electroless deposition methods to form metallic conductive paths to connect components is known in the art (German Patent 44 38 779 A1 and European Patents). 0 083 458 B1). However, this process has been known for about 10 years and is not suitable for selectively coating channels of channel plates because of different dimensions and different boundary conditions.

Thus, this did not have any effect on the technique of attaching a metallic conductive path as an electrode to a channel plate for a large-screen flat-panel display, while attaching a metallic conductive path as an electrode to a channel plate for a large-screen flat-panel display. It was controlled by the large-area metal layer attachment principle and selectively developed conductive paths by masking.

There are many ways to form the conducting path. According to another feature of the invention, special advantages are obtained if the thin conductive path is first attached in an electroless manner and then augmented through galvanic or chemical attachment. The advantage is that if a thin, full-area conductive layer is first attached to the starter layer and then the surface on which the electrode of this layer is to be selectively covered and optionally enlarged in a galvanic and / or electroless manner Turned out to be. Finally, the electrode area outside is removed again in this thin full-area starting layer. Where possible, the electrode regions are selectively augmented through a self-adjusting mask.

Alternatively, the process is performed by first attaching a thin, full-area conductive layer to the initiation layer, which is formed to conform to the structure by photolithography and augmented in a galvanic or electroless manner.

The conductive initiation layer is a metal or conductive oxide deposited with a layer thickness of up to 500 nm, possibly 200 nm.

If the structure is formed in the channel plate by photolithography using a photoresist covering the entire channel plate and a positive mask corresponding to the conductive path structure to form a selective conductive path structure, Another advantage of the present process of attaching a metallic conductive path as an address electrode to the channel plate is obtained. The free path defined by the photodevelopment process results in palladium nucleation, photoresist stripping in the remaining areas, and finally, in the nucleated path, a metallic conductive path is attached in the liquid state and at least one protective layer thereon. This is provided. In this way an adhesive conductive path using a relatively small amount of metal is ensured.

Alternatively, for the formation of a selective conductive path, the palladium nucleus is selectively attached according to the conductive path structure, the metallic conductive path is attached in the liquid state to the nucleation path, and at least one protective layer is provided thereto. This process can be carried out advantageously.

There are several methods for selective palladium nucleation. According to one embodiment, ink jet technology is used to attach the palladium nuclei. Alternatively, according to another embodiment of the present invention, the palladium nucleus is selectively selected by blasting or etching the channel plate using a mask having holes according to the conductive path structure, the structure being formed mechanically or through a photolithography process. Can be attached. This roughens the uncovered path area for selective nucleation from a palladium bath.

In another way of carrying out this process, the entire channel plate is first covered with a palladium nucleus to selectively attach the conducting path. Next, an electrode structural path is made by selectively attaching a metal to the path through a photolithography process using a photoresist and a mask covering the entire channel plate. In the remaining areas, the photoresist having the palladium nucleus at the bottom is stripped off, and the attached conductive path is provided with at least one protective layer. Full-area palladium nucleation is not a continuous metal layer, but merely a distribution of individual nuclei. Thus, at most very thin, full-area initiation layers are needed and are optionally enlarged as described above.

The term "photolithographic structuring" should be understood to include the following steps: application of photoresist, exposure, development, etching of exposed areas of the substrate, peeling off (or lift) of the photoresist. Similar process such as lift-off).

It is advantageous to apply a SiO ₂ diffusion barrier to the entire area underneath the full-area palladium nucleation layer to prevent reaction with the glass.

The process can be performed particularly cost-effectively due to the use of metals or metal alloys in electroless or galvanic deposition processes, which also carry out corrosion protection and sputter protection as well as the ability to carry current. According to one embodiment of the invention, it is advantageous if the electrode material consists of nickel and / or copper together with a metallic corrosion inhibitor, the corrosion resistant metal can be attached in an electroless manner, preferably nickel, palladium or It is good to be gold. Alternatively, the electrode material has the advantage of being composed of nickel and / or precious metals together with metallic corrosion inhibitors. In this case, the precious metal is a metal that can be attached in an electroless or galvanic manner, such as palladium, silver or gold, and the corrosion resistant metal can be attached in an electroless manner, preferably nickel, palladium or gold. good.

In electroless deposition, the metal is present in a reductive bath. For example, if copper is attached, a reductive copper bath is provided, also referred to as "chemical copper", which allows for self-catalytic attachment of metals.

The following examples illustrate the process according to the invention in detail and clearly show its advantages.

Example 1 (Figure 2)

One side of the flat AF45 glass substrate (100 × 100 × 3 mm 3) is coated with a positive resist (photoresist), for example (Shipley 1818), 2 m thick, corresponding to the required electrode structure. It is selectively exposed through a mask (step 1). After development, the substrate is immersed in an ammonium hydrogen fluoride solution for 3 minutes. This causes the glass surface to be slightly chemically roughened, allowing the metal to stick to the glass better. The glass substrate is fixed to the frame such that only one side of the glass is exposed to the solution. The glass substrate is immersed in 5% tin (II) hydrochloride solution, rinsed with distilled water for 30 seconds, and soaked in 0.05% palladium (II) hydrochloride solution for 1 minute to start palladium nucleation (step 2). The glass substrate is then rinsed for one minute in running distilled water. The photoresist is stripped off by dipping in acetone. This leaves only the palladium nuclei in the glass, which is necessary for the subsequent formation of the electrode's structure (step 3).

The glass thus treated is immersed in a chemical nickel bath (chemical nickel bath: Ni component 4.5 g / l, hypophosphite component 22 g / l, pH value 4.5) for 1 minute. This selectively attaches a nickel path to a thickness of 150 nm and a width specified in the photolithography process (step 4). The conductive paths are dried at 200 ° C. for better adhesion. This selectively nickel-plated glass is immersed in a 40 ° C., chemical copper bath (2.5 g / l Cu component, formalin concentration 37% 8 ml / l, pH value 8.2) for 45 minutes. 2.5 μm of copper is attached to the sample (step 5). Copper paths are now nickel-plated to prevent corrosion. The substrate is immersed in a 5% tin (II) hydrochloride solution for 30 seconds, rinsed with distilled water for 15 seconds, and immersed in an activator (50 mg / L Pd component, pH value 2) for 30 seconds. After rinsing with distilled water, the glass substrate was again immersed in the chemical nickel solution at 65 ° C. for 5 minutes, thereby forming a 1 μm thick nickel phosphorous layer to act as a corrosion protection (step 6).

Example 2 (FIG. 2)

The glass substrate is optionally provided with a palladium nucleus again, as in Example 1, except that ink jet technology is used to attach the palladium nuclei directly according to the structure. The substrate thus treated is immersed in the chemical nickel bath at 70 ° C. for 1 minute, thereby selectively attaching a 150 nm thick nickel path having a width defined by the printing technique (step 4). After the printing process, the layer is thermally fixed at 200 ° C. This optionally nickel-plated glass is immersed in the copper bath described above for 40 minutes at 40 ° C., which attaches a 2,5 μm thick layer of copper to nickel (step 5). Copper paths are now nickel-plated to prevent corrosion. The substrate is immersed in 5% tin (II) hydrochloride solution for 30 seconds, rinsed with distilled water for 15 seconds, and immersed in the activation bath mentioned in Example 1 for 30 seconds. After rinsing with distilled water, the glass substrate was again immersed in the chemical nickel solution at 65 ° C. for 5 minutes. This results in the formation of a 1 μm thick nickel phosphorous layer that provides corrosion protection (step 6).

Example 3 (FIG. 3)

To slightly chemically roughen the glass surface so that the metal adheres well to the glass, a flat D 263 glass substrate (100 × 100 × 3 mm 3) is immersed in the ammonium bifluoride solution for 5 minutes. The glass substrate is fixed to the frame such that only one side of the glass is exposed to the solution. The glass substrate is immersed in a 5% tin (II) hydrochloride solution, rinsed with distilled water for 30 seconds, and soaked in 0.05% palladium (II) hydrochloride solution for 1 minute to start palladium nucleation (step 1). The glass substrate is then rinsed for one minute in running distilled water.

Next, a negative photoresist (3 mu m) is applied to the chemically treated side of the glass and structured with a corresponding mask (step 2). The glass thus treated is dipped in the aforementioned nickel bath at 60 ° C. for 1 minute. This causes the nickel path to be selectively attached to the width and 100 nm thickness defined by the photolithography process (step 3). This optionally nickel-plated glass is immersed in the copper bath described above at 40 ° C. for 45 minutes, thereby attaching 2.5 μm of copper to nickel (step 4). The photoresist and its underlying palladium nucleus are stripped by dipping in an aqueous alkali solution (10% sodium hydroxide solution) containing the synthetic ethylenediamine tetraacetic acid (EDTA) at a concentration of 100 g / l ( Step 5). And the copper paths are nickel-plated to prevent corrosion. The substrate is soaked in 5% tin (II) hydrochloride solution for 30 seconds, rinsed with distilled water for 15 seconds, and soaked in the above-described activator for 30 seconds. After rinsing with distilled water, the glass substrate is again dipped in the chemical nickel solution for 5 minutes. This results in the formation of a 1-micron thick nickel-phosphorus layer to provide corrosion protection (step 6).

Example 4 (FIG. 4)

A flat AF45 glass substrate (200 x 150 x 3 mm3) is coated with a mechanical resist by silk-screening (step 1). Thus, a blasting process using aluminum oxide grains is performed on the glass substrate on which the structure is formed (step 2). After blasting, the resist is stripped away leaving only the structure that was roughened by the blasting of the glass substrate (step 3). This results in a ca 5 μm deep channel. At the bottom of the channel, the height from the highest point to the lowest point is 0.5 μm. The roughened glass substrate thus formed is immersed in a 5% tin (II) hydrochloride solution, rinsed with distilled water for 30 seconds, and then immersed in 0.05% palladium (II) hydrochloride solution for 1 minute to start palladium nucleation. (Step 4). The glass substrate is then rinsed with distilled water for 5 minutes by spraying. This removes nuclei from the roughened portion of the glass substrate, leaving enough nuclei in the roughened channel region (step 5). The glass thus treated is immersed in the aforementioned nickel bath at 60 ° C. for 1 minute to attach a nickel path to the prescribed width and thickness of 100 nm (step 6). This optionally nickel-plated glass was immersed in the copper bath at 40 ° C. for 45 minutes to attach 2.5 μm of copper to nickel (step 7). Copper paths are now gold-plated to prevent corrosion. The substrate is immersed in a gold bath (gold component 3 g / l, pH value 4.6) at 85 ° C. for 15 minutes. This selectively attaches a 100 nm thick gold layer to the copper (step 8).

The present invention enables cost-effective attachment of address electrodes to a channel plate for a flat panel display, even in view of the metal consumption which is significantly saved by the process itself and by selectively attaching a metallic conductive path, The examples above show an economical process.

Claims (21)

In the process of attaching a metallic conductive path as an electrode to a channel plate for a large-screen flat panel display through an electroless and galvanic process for metal attachment, Wherein the metallic conductive path is optionally attached only to the electrode region via an electroless and / or galvanic attachment process. The process according to claim 1, wherein the thin conductive path is first attached in an electroless manner and then augmented by galvanic or chemical attachment. 3. A thin, full-area conductive layer is first attached as an initiation layer, optionally overlaid, and the region in which the electrode of the layer is to be formed is selectively covered in a galvanic manner and / or in an electroless manner. And, wherein the electrode area outside of the thin full-area starting layer is removed again. 4. The process of claim 3, wherein the electrode region is selectively enlarged by a self-adjusting mask. 3. The method of claim 2, wherein a thin, full-area conductive layer is first deposited as an initiation layer, then structured by photolithography, and augmented in a galvanic and / or electroless manner. Process characterized. The thin conductive layer of claim 2, wherein the thin conductive layer is optionally structured as an initiating layer, optionally by ink jet technology and preferably by spraying a metal-containing solution, suspension or paste, and galvanic and / or electroless Characterized in that it is augmented in a manner. The process according to any one of claims 3 to 6, wherein a metal layer up to 550 nm thick is formed as a conductive initiation layer. 8. The process of claim 7, wherein the layer thickness is at most 200 nm. 6. The process according to any one of claims 3 to 5, wherein a conductive oxide layer up to 500 nm thick is formed as a conductive initiation layer. The process of claim 9, wherein the layer thickness is at most 200 nm. The channel plate of claim 1 or 2, wherein the channel plate is conductive through photolithography using a positive mask and a photoresist covering the entire channel plate in order to structure the selective conductive path. Structured according to the path structure, the palladium nucleus is covered by the free path defined by the photolithography process, the photoresist is stripped from the remaining areas, and the metallic conducting path is attached in the liquid state to the nucleated path, with minimal A process, characterized in that one protective layer is provided. 3. The method of claim 1 or 2, wherein for the formation of a selective conducting pass, a palladium nucleus is selectively attached according to the conducting pass structure, and a metallic conducting pass is attached in the liquid state to the nucleated path and at least A process, characterized in that one protective layer is provided. The process of claim 12 wherein the palladium nuclei are attached via ink jet technology. 13. A hole according to a conductive path structure according to claim 12, wherein the structure is formed mechanically or through a photolithography process to roughen the uncovered path area that is selectively nucleated from a palladium bath. And selectively attaching the palladium nucleus by blasting or etching the channel plate through the mask. 3. The method of claim 1 or 2, wherein to selectively attach the conductive path, the entire channel plate is first covered with a palladium nucleus, and optionally the metal is subjected to a photolithography process using a photoresist and mask covering the entire channel plate. Attaching to the path to form an electrode structural path, wherein the photoresist is stripped with the underlying palladium nucleus, and the attached conductive path is provided with at least one protective layer. The process according to claim 1, wherein a SiO ₂ diffusion barrier is attached to the entire region of the channel plate, if possible, and under the full-region palladium nucleation layer. The process according to claim 1, wherein a metal or a metal alloy is used for the electroless or galvanic deposition process, which performs corrosion protection and sputter protection with a current transfer function. 18. The electrode material of claim 17, wherein the electrode material consists of nickel and / or copper with a metallic corrosion inhibitor, and the corrosion resistant metal consists of a corrosion resistant metal that can be attached in an electroless manner, preferably nickel, palladium or gold. Process characterized in that. 18. The electrode material of claim 17, wherein the electrode material is comprised of nickel and / or precious metals with a metallic corrosion inhibitor, and the precious metal is comprised of metals that can be attached in an electroless or galvanic manner, such as palladium, silver or gold, and corrosion resistant The metal is a process characterized in that it consists of an anti-corrosion metal which can be attached in an electroless manner, preferably nickel, palladium, chromium or gold. The process according to any one of claims 1 to 19, wherein the layer forming the electrode is made of a multilayered layer. 21. The process according to claim 20, wherein the multilayered layer consists of an adhesion promoting layer, an electrically conductive layer and at least one protective layer, respectively.