US20160040292A1

Movatterモバイル変換

Info

Publication number: US20160040292A1
Application number: US14/455,196
Authority: US
Inventors: Gary P. Wainwright; Shawn A. Reuter
Original assignee: Individual
Current assignee: Eastman Kodak Co
Priority date: 2014-08-08
Filing date: 2014-08-08
Publication date: 2016-02-11
Also published as: WO2016022311A1; TW201612359A

Abstract

A roll-to-roll electroless plating system including a sump containing a first volume of a plating solution, and a pan containing a second volume of the plating solution, the second volume being less than the first volume. A web advance system advances a web of media though the plating solution in the pan, wherein a plating substance in the plating solution is plated onto predetermined locations on a surface of the web of media. A pan-replenishing pump moves plating solution from the sump to the pan through a pipe. A distribution system injects an inert gas into the plating solution to reduce the amount of dissolved oxygen.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly-assigned, co-pending U.S. patent application Ser. No. ______ (Docket K001834), entitled “Method for roll-to-roll electroless plating with low dissolved oxygen content” by G. Wainwright et al.; and to commonly-assigned, co-pending U.S. patent application Ser. No. ______ (Docket K001837), entitled “Roll-to-roll electroless plating system with micro-bubble injector” by G. Wainwright et al., each of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention pertains to the field of roll-to-roll electroless plating, and more particularly to a system and method for providing low dissolved oxygen content in the plating solution.

BACKGROUND OF THE INVENTION

Electroless plating, also known as chemical or auto-catalytic plating, is a non-galvanic plating process that involves chemical reactions in an aqueous plating solution that occur without the use of external electrical power. Typically, the plating occurs as hydrogen is released by a reducing agent and oxidized, thus producing a negative charge on the surface of the part to be plated. The negative charge attracts metal ions out of the plating solution to adhere as a metalized layer on the surface. Using electroless plating to provide metallization in predetermined locations can be facilitated by first depositing a catalytic material in the predetermined locations. This can be done, for example by printing features using an ink containing a catalytic component.

Touch screens are visual displays with areas that may be configured to detect both the presence and location of a touch by, for example, a finger, a hand or a stylus. Touch screens may be found in televisions, computers, computer peripherals, mobile computing devices, automobiles, appliances and game consoles, as well as in other industrial, commercial and household applications. A capacitive touch screen includes a substantially transparent substrate which is provided with electrically conductive patterns that do not excessively impair the transparency—either because the conductors are made of a material, such as indium tin oxide, that is substantially transparent, or because the conductors are sufficiently narrow that the transparency is provided by the comparatively large open areas not containing conductors. For capacitive touch screens having metallic conductors, it is advantageous for the features to be highly conductive but also very narrow. Capacitive touch screen sensor films are an example of an article having very fine features with improved electrical conductivity resulting from an electroless plated metal layer.

Projected capacitive touch technology is a variant of capacitive touch technology. Projected capacitive touch screens are made up of a matrix of rows and columns of conductive material that form a grid. Voltage applied to this grid creates a uniform electrostatic field, which can be measured. When a conductive object, such as a finger, comes into contact, it distorts the local electrostatic field at that point. This is measurable as a change in capacitance. The capacitance can be measured at every intersection point on the grid. In this way, the system is able to accurately track touches. Projected capacitive touch screens can use either mutual capacitive sensors or self capacitive sensors. In mutual capacitive sensors, there is a capacitor at every intersection of each row and each column. A 16×14 array, for example, would have 224 independent capacitors. A voltage is applied to the rows or columns. Bringing a finger or conductive stylus close to the surface of the sensor changes the local electrostatic field which reduces the mutual capacitance. The capacitance change at every individual point on the grid can be measured to accurately determine the touch location by measuring the voltage in the other axis. Mutual capacitance allows multi-touch operation where multiple fingers, palms or styli can be accurately tracked at the same time.

WO 2013/063188 by Petcavich et al. discloses a method of manufacturing a capacitive touch sensor using a roll-to-roll process to print a conductor pattern on a flexible transparent dielectric substrate. A first conductor pattern is printed on a first side of the dielectric substrate using a first flexographic printing plate and is then cured. A second conductor pattern is printed on a second side of the dielectric substrate using a second flexographic printing plate and is then cured. The ink used to print the patterns includes a catalyst that acts as seed layer during subsequent electroless plating. The electrolessly plated material (e.g., copper) provides the low resistivity in the narrow lines of the grid needed for excellent performance of the capacitive touch sensor. Petcavich et al. indicate that the line width of the flexographically printed material can be 1 to 50 microns.

Flexography is a method of printing or pattern formation that is commonly used for high-volume printing runs. It is typically employed in a roll-to-roll format for printing on a variety of soft or easily deformed materials including, but not limited to, paper, paperboard stock, corrugated board, polymeric films, fabrics, metal foils, glass, glass-coated materials, flexible glass materials and laminates of multiple materials. Coarse surfaces and stretchable polymeric films are also economically printed using flexography.

Flexographic printing members are sometimes known as relief printing members, relief-containing printing plates, printing sleeves, or printing cylinders, and are provided with raised relief images onto which ink is applied for application to a printable material. While the raised relief images are inked, the recessed relief “floor” should remain free of ink.

Although flexographic printing has conventionally been used in the past for printing of images, more recent uses of flexographic printing have included functional printing of devices, such as touch screen sensor films, antennas, and other devices to be used in electronics or other industries. Such devices typically include electrically conductive patterns.

To improve the optical quality and reliability of the touch screen, it has been found to be preferable that the width of the grid lines be approximately 2 to 10 microns, and even more preferably to be 4 to 8 microns. In addition, in order to be compatible with the high-volume roll-to-roll manufacturing process, it is preferable for the roll of flexographically printed material to be electroless plated in a roll-to-roll electroless plating system. More conventionally, electroless plating is performed by immersing the item to be plated in a tank of plating solution. However, for high volume uniform plating of features on both sides of the web of substrate material, it is preferable to perform the electroless plating in a roll-to-roll electroless plating system.

Roll-to-roll electroless plating systems are commercially available from Chemcut Corporation, for example. However, commercially available roll-to-roll electroless plating systems are adapted to be used with plating solutions that include a relatively high amount of dissolved oxygen, for example greater than three parts per million. Such plating solutions can work well for plating copper in the context of printed circuit board manufacture where the minimum line width is on the order of 100 microns. However, it has been found that such oxygen-rich plating solutions do not provide uniform metallization at high yield on features having line widths of 10 microns or less.

Dissolved oxygen content of an electroless plating solution influences the rate and quality of the plating. As indicated in U.S. Pat. No. 4,616,596 Helber Jr. et al., entitled “Electroless plating apparatus,” U.S. Pat. No. 4,684,545 to Fey et al., entitled “Electroless plating with bi-level control of dissolved oxygen,” and U.S. Patent Application Publication No. 2011/0214608 to Ivanov et al., entitled “Electroless Plating System,” increased oxygen content tends to stabilize plating and decrease the plating rate. Decreased oxygen content tends to increase plating activity.

It has been found that a copper electroless plating solution made by Enthone is well-suited to provide high quality plating on features having minimum line widths of 10 microns or less in a low dissolved oxygen content tank plating system, but not in a commercially available roll-to-roll electroless plating system. What is needed is a roll-to-roll plating system and method that can provide and maintain low dissolved oxygen content in the plating solution.

SUMMARY OF THE INVENTION

The present invention represents a roll-to-roll electroless plating system, comprising:

a sump containing a first volume of a plating solution;

a pan containing a second volume of the plating solution, the second volume being less than the first volume;

a web advance system for advancing a web of media from an input roll though the plating solution in the pan along a web advance direction and to a take-up-roll, wherein a plating substance in the plating solution is plated onto predetermined locations on a surface of the web of media as it is advanced through the plating solution in the pan;

a pan-replenishing pump for moving plating solution from the sump to the pan through a pipe connected to an outlet of the pan-replenishing pump; and

a distribution system for injecting an inert gas into the plating solution.

This invention has the advantage that the injection of the inert gas reduces the amount of dissolved oxygen in the plating solution to provide dissolved oxygen levels appropriate for use with plating solutions whose performance degrades at higher levels of dissolved oxygen.

It has the additional advantage that the exposure of the plating solution to air is minimized, thereby further reducing the amount of dissolved oxygen.

It has the further advantage that the amount of dissolved oxygen can be controlled to be in a range which is optimal for use with a particular plating solution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a flexographic printing system for roll-to-roll printing on both sides of a substrate;

FIG. 2 is a schematic side view of a prior art roll-to-roll electroless plating system;

FIG. 3 is a schematic side view of a roll-to-roll electroless plating system according to an embodiment of the invention;

FIG. 4 is a schematic side view of a roll-to-roll electroless plating system according to another embodiment of the invention;

FIG. 5A is a top view of an exemplary embodiment of a plumbing assembly for distributing inert gas bubbles into the plating solution;

FIG. 5B is a top view of another exemplary embodiment of a plumbing assembly for distributing inert gas bubbles into the plating solution;

FIG. 6 is a side view of an injector for injecting inert gas at a localized low pressure region;

FIG. 7 is a high-level system diagram for an apparatus having a touch screen with a touch sensor that can be printed using embodiments of the invention;

FIG. 8 is a side view of the touch sensor ofFIG. 7;

FIG. 9 is a top view of a conductive pattern printed on a first side of the touch sensor ofFIG. 8; and

FIG. 10 is a top view of a conductive pattern printed on a second side of the touch sensor ofFIG. 8.

It is to be understood that the attached drawings are for purposes of illustrating the concepts of the invention and may not be to scale.

DETAILED DESCRIPTION OF THE INVENTION

The present description will be directed in particular to elements forming part of, or cooperating more directly with, an apparatus in accordance with the present invention. It is to be understood that elements not specifically shown, labeled, or described can take various forms well known to those skilled in the art. In the following description and drawings, identical reference numerals have been used, where possible, to designate identical elements. It is to be understood that elements and components can be referred to in singular or plural form, as appropriate, without limiting the scope of the invention.

The invention is inclusive of combinations of the embodiments described herein. References to “a particular embodiment” and the like refer to features that are present in at least one embodiment of the invention. Separate references to “an embodiment” or “particular embodiments” or the like do not necessarily refer to the same embodiment or embodiments; however, such embodiments are not mutually exclusive, unless so indicated or as are readily apparent to one of skill in the art. It should be noted that, unless otherwise explicitly noted or required by context, the word “or” is used in this disclosure in a non-exclusive sense.

The example embodiments of the present invention are illustrated schematically and not to scale for the sake of clarity. One of ordinary skill in the art will be able to readily determine the specific size and interconnections of the elements of the example embodiments of the present invention.

References to upstream and downstream herein refer to direction of flow. Web media moves along a media path in a web advance direction from upstream to downstream. Similarly, fluids flow through a fluid line in a direction from upstream to downstream.

As described herein, the example embodiments of the present invention provide a roll-to-roll electroless plating system and methods for providing and maintaining low dissolved oxygen content in the plating solution. The roll-to-roll electroless plating system is useful for metalizing printed features in sensor films incorporated into touch screens. However, many other applications are emerging for printing and electroless plating of functional devices that can be incorporated into other electronic, communications, industrial, household, packaging and product identification systems (such as RFID) in addition to touch screens. In addition, roll-to-roll electroless plating systems can be used to plate items for decorative purposes rather than electronic purposes and such applications are contemplated as well.

FIG. 1 is a schematic side view of aflexographic printing system100 that can be used in embodiments of the invention for roll-to-roll printing of a catalytic ink on both sides of asubstrate150 for subsequent electroless plating.

Substrate

150 is fed as a web fromsupply roll102 to take-up roll104 throughflexographic printing system100.Substrate150 has afirst side151 and asecond side152.

Theflexographic printing system100 includes two

print modules

120 and140 that are configured to print on thefirst side151 ofsubstrate150, as well as two

print modules

110 and130 that are configured to print on thesecond side152 ofsubstrate150. The web ofsubstrate150 travels overall in roll-to-roll direction105 (left to right in the example ofFIG. 1). However,

various rollers

106 and107 are used to locally change the direction of the web of substrate as needed for adjusting web tension, providing a buffer, and reversing thesubstrate150 for printing on an opposite side. In particular, note that inprint module120

roller

107 serves to reverse the local direction of the web ofsubstrate150 so that it is moving substantially in a right-to-left direction.

Each of the

print modules

110,120,130,140 includes some similar components including a

respective plate cylinder

111,121,131,141, on which is mounted a respective

flexographic printing plate

112,122,132,142, respectively. Each

flexographic printing plate

112,122,132,142 has raisedfeatures113 defining an image pattern to be printed on thesubstrate150. Each

print module

110,120,130,140 also includes a

respective impression cylinder

114,124,134,144 that is configured to force a side of thesubstrate150 into contact with the corresponding

flexographic printing plate

112,122,132,142.

Impression cylinders

124 and144 ofprint modules120 and140 (for printing onfirst side151 of substrate150) rotate counter-clockwise in the view shown inFIG. 1, while

impression cylinders

114 and134 ofprint modules110 and130 (for printing onsecond side152 of substrate150) rotate clockwise in this view.

Each

print module

110,120,130,140 also includes a

respective anilox roller

115,125,135,145 for providing ink to the corresponding

flexographic printing plate

112,122,132,142. As is well known in the printing industry, an anilox roller is a hard cylinder, usually constructed of a steel or aluminum core, having an outer surface containing millions of very fine dimples, known as cells. Ink is provided to the anilox roller by a tray or chambered reservoir (not shown). In some embodiments, some or all of the

print modules

110,120,130,140 also include respective

UV curing stations

116,126,136,146 for curing the printed ink onsubstrate150.

FIG. 2 is a schematic side view of a prior art roll-to-rollelectroless plating system200, similar to a configuration available from Chemcut Corporation, for use with aplating solution210. The roll-to-rollelectroless plating system200 performs well with platingsolutions210 that are formulated for optimized plating with relatively high dissolved oxygen content (e.g., greater than 3 parts per million).Substrate250 is fed as a web of media fromsupply roll202 to take-up roll204.Drive rollers206 advance the web in aweb advance direction205 from thesupply roll202 through a reservoir of theplating solution210 to the take-up roll204. In the configuration shown inFIG. 2, asump230 contains a large volume of theplating solution210, and apan220 positioned above the sump contains a smaller volume of theplating solution210.

As thesubstrate250 is advanced through theplating solution210 in thepan220, a metallic plating substance such as copper, silver, nickel or palladium is electrolessly plated from theplating solution210 onto predetermined locations on one or both of afirst surface251 and asecond surface252 of thesubstrate250. As a result, the concentration of the metal in theplating solution210 in thepan220 decreases and theplating solution210 needs to be refreshed. To refresh theplating solution210, it is recirculated between thesump230 and thepan220. Alower lift pump232

moves plating solution

210 from thesump230 through apipe233 to alower flood bar222 for distribution into thepan220 below thesubstrate250. Likewise, anupper lift pump234

moves plating solution

210 from thesump230 through apipe235 to anupper flood bar224 for distribution into thepan220 above thesubstrate250.Excess plating solution210 waterfalls back into thesump230 atfreefall return236. Occasionally theplating solution210 is chemically analyzed, for example by titration, andfresh plating solution210, or components of theplating solution210, are added to thesump230 as needed.Air inlet tubes240 are provided to provide additional oxygen to theplating solution210 insump230 as needed.

Although the prior art roll-to-rollelectroless plating system200 shown inFIG. 2 works well for platingsolutions210 that are designed to plate at relatively high levels of dissolved oxygen, for example greater than3 parts per million, it has been found that it does not work well for platingsolutions210 that are designed to plate at a lower level of dissolved oxygen, for example between about 0.5 parts per million and about 2 parts per million. Not adding air through theair inlet tubes240 is an obvious measure for reducing the dissolved oxygen content in theplating solution210. However, in order to control the dissolved oxygen content at the desired low level, it is necessary to make significant modifications to the roll-to-rollelectroless plating system200.

FIG. 3 is a schematic side view of an improved roll-to-rollelectroless plating system300 which is useful for platingsolutions310 having a low level of dissolved oxygen content. As in the prior artelectroless plating system200, asubstrate350 is fed as a web of media from asupply roll302 to a take-up roll304.Drive rollers306 advance the web ofsubstrate350 along aweb advance direction305 from thesupply roll302 through a reservoir of platingsolution310 to the take-up roll304. Asump330 contains a large volume of theplating solution310 and apan320 positioned above the sump contains a smaller volume of theplating solution310. The term “reservoir” can be used to refer to either thesump330 or thepan320.

As thesubstrate350 is advanced through theplating solution310 inpan320, a metallic plating substance such as copper, silver, nickel or palladium is electrolessly plated from theplating solution310 onto predetermined locations on one or both of afirst surface351 and asecond surface352 of thesubstrate350. The predetermined locations can be provided, for example, by the prior printing of a catalytic ink.

A number of modifications have been made relative to the prior art similar to a configuration available from roll-to-rollelectroless plating system200 ofFIG. 2 to control the amount of dissolved oxygen in the plating solution within a lower range of about0.5 to about2 parts per million. The modifications include measures to a) reduce the amount of turbulence in theplating solution310 in portions of the roll-to-rollelectroless plating system300 that are exposed to air, b) reduce the exposure of theplating solution310 to ambient air, c) displace dissolved oxygen from theplating solution310, and d) sense the amount of dissolved oxygen in theplating solution310.

Modifications for reducing turbulence in the roll-to-rollelectroless plating system300 ofFIG. 3 relative to the prior art roll-to-rollelectroless plating system200 ofFIG. 2 include replacing the freefall return236 (FIG. 2) with a more controlled flow of theplating solution310 through adrain pipe336; eliminating thelower flood bar222 and the upper flood bar224 (FIG. 2); and removing theupper lift pump234 and its associated plumbing. Instead, in roll-to-rollelectroless plating system300, there is only a singlepan-replenishing pump332 that movesplating solution310 from thesump330 to thepan320 through apipe333 connected to anoutlet335 of thepan-replenishing pump332.Plating solution310 enters thepan-replenishing pump332 fromsump330 via aninlet331.

In addition to reducing splashing and other forms of turbulence,drain pipe336 also reduces the exposure of platingsolution310 to ambient air. The top ofdrain pipe336 is within theplating solution310 inpan320, and the bottom ofdrain pipe336 is within theplating solution310 insump330. Other measures for reducing the exposure of platingsolution310 to ambient air include providing asump cover338 and optionally providing a pan cover328 (seeFIG. 4).

Preferred embodiments of the invention also include modifications that provide for the displacement of dissolved oxygen from theplating solution310. This is done by injecting an inert gas into theplating solution310 via a distribution system. As used herein, the term inert gas refers to a gas that does not take part in the chemical reactions necessary for electroless plating. Nitrogen is an example of such an inert gas. Another example of an inert gas would be argon. In various embodiments, the inert gas can also be injected into one or both of thesump330 andpan320.FIG. 3 shows inert gas being injected into thepan320 from aninert gas source345. In the illustrated embodiment, the inert gas from theinert gas source345 is inserted intopipe333 at throughtee334, formingbubbles344 which are carried into thepan320.

FIG. 3 also showsbubbles344 of inert gas being injected into thesump330 frominert gas source340. As the inert gas is dissolved in theplating solution310, the amount of dissolved oxygen decreases. To facilitate dissolution of the inert gas, it is advantageous to inject the inert gas as micro-bubbles and to distribute the inert gas in such a way as to promote longer paths through theplating solution310 before exiting. In the embodiment ofFIG. 3, thebubbles344 are injected through aplumbing assembly342 located near abottom339 ofsump330 so that the injected bubbles344 will rise through nearly the entire height of theplating solution310. The inert gas enters theplumbing assembly342 from theinert gas source340 through aninert gas inlet341. As shown in the top view ofFIG. 5A, in an exemplary embodiment theplumbing assembly342 has a network of distributedorifices343, so that the inert gas bubbles344 enter theplating solution310 more uniformly, thereby facilitating dissolution by avoiding forming a few regions of inert-gas-saturatedplating solution310.

Within the context of the present invention, micro-bubbles are defined as bubbles having a diameter between about one micron (one thousandth of a millimeter) and one millimeter. Since the ratio of surface area to volume of a sphere is inversely dependent upon diameter, micro-bubbles have a larger surface area to volume ratio than larger bubbles, thereby facilitating efficient dissolution into theplating solution310. In addition, micro-bubbles tend to stay suspended longer in theplating solution310 rather than rising and bursting rapidly. As described below, there are a variety of ways to inject the inert gas into theplating solution310 in the form of micro-bubbles.

It is also advantageous to control the amount of flow of inert gas into theplating solution310 according to a measured amount of dissolved oxygen in theplating solution310. Anoxygen sensor360 can be immersed into, or periodically dipped into, theplating solution310 to measure the dissolved oxygen content. The data from theoxygen sensor360 can be provided to acontroller315 to control the rate of flow of inert gas injected into platingsolution310 frominert gas source340 orinert gas source345, for example by controlling flow rate through a needle valve (not shown).

FIG. 4 shows a schematic side view of an alternate embodiment of a roll-to-rollelectroless plating system300 that injects micro-bubbles of inert gas into thesump330 by means of a recirculation system including arecirculation pump370 having aninlet373 and anoutlet375; aninlet line372 for movingplating solution310 from thesump330 to thepump inlet373; and anoutlet line374 for returningplating solution310 from thepump outlet375 to thesump330. In the example shown inFIG. 4, inert gas is injected into thelow pressure inlet373 of therecirculation pump370 from aninert gas source376 connected toinlet373 bytee378. Mechanical action withinrecirculation pump370 tends to break inert gas bubbles into micro-bubbles, which then flow together with platingsolution310 from thepump outlet375 into thesump330 through aplumbing assembly342 located nearbottom339 ofsump330 providing thebubbles344. Furthermore, afilter377 can be disposed in theoutlet line374 for removing particulates so that they do not re-enter thesump330. A second function offilter377, which may have a pore size on the order of one micron, can optionally be used to break up bubbles of inert gas into micro-bubbles. Thus, inert gas is injected into theplating solution310 outside thesump330 to provide an inert-gas-rich plating solution310, and the inert-gas-rich plating solution310 is delivered into thesump330.

FIG. 5B shows a top view of an exemplary embodiment of theplumbing assembly379, where the inert gas is injected from theinert gas source376 into theinlet line372 to therecirculation pump370. The inert gas bubbles pass through afilter377 before enteringplumbing assembly379. The bubbles of inert gas have a long flow path withinplumbing assembly379 before exiting at distributedorifices371, thereby aiding dissolution of the inert gas into the plating solution310 (FIG. 4) within theplumbing assembly379.

An advantage of injecting inert gas on the low pressure inlet side of a pump is that theinert gas source376 can be a low pressure source for improved flow control. However, a potential disadvantage of injecting inert gas into a pump inlet is cavitation damage within the pump.FIG. 4 also shows inert gas flowing frominert gas source345 through atee334 intopipe333 downstream of theoutlet335 ofpan-replenishing pump332. Thus, inert gas is injected into theplating solution310 outside thepan320 to provide an inert-gas-rich plating solution310, and the inert-gas-rich plating solution310 is delivered into thepan320 through thepipe333. Afilter348 can be used for further reducing the size of bubbles.

In some embodiments, a static mixer (not shown) having a tortuous flow path around baffles can be inserted in-line withpipe333 to facilitate dissolution of the inert gas micro-bubbles within theplating solution310 being returned topan320 throughpipe333.

AlthoughFIG. 4 shows inert gas provided upstream of theinlet373 ofrecirculation pump370, and shows inert gas provided downstream of theoutlet335 ofpan-replenishing pump332, alternatively inert gas could be provide downstream ofoutlet375 ofrecirculation pump370 or upstream ofinlet331 ofpan-replenishing pump332.

For configurations where the inert gas is provided downstream of the outlet of a pump (i.e., on the high pressure side of the pump), it is advantageous to provide a local low pressure region where the inert gas can be injected. For example, inFIG. 4, it can be useful to provide a local low pressure region where the inert gas is injected downstream of theoutlet335 of thepan-replenishing pump332.FIG. 6 is a side view of an injector380 (sometimes called a Venturi injector) for providing a local low pressure region at a gas injection site. Theinjector380 can be used at the position of thetee334 inFIG. 4.Injector380 includes athroat386; convergingtube segment382 upstream of thethroat386 having a diameter D1 that decreases from an upstream portion to a downstream portion; and a divergingtube segment384 downstream of thethroat386 having a diameter D2 that increases from an upstream portion to a downstream portion. Thethroat386 is formed by the junction of the convergingtube segment382 and the divergingtube segment384. Theplating solution310 flows through theinjector380 from upstream to downstream inflow direction385. Due to the

Venturi effect, a localized low pressure region is formed at thethroat386. By providing aninlet388 forinert gas389 in proximity to thethroat386, a low pressure source of inert gas, such asinert gas sources340,345 (FIG. 4) can be used. In some operating conditions it has been found that micro-bubbles tend to be formed when the inert gas is injected usinginjector380, thereby providing an additional advantage for the use of this device. In some embodiments, aninjector380 can be also be used to inject inert gas downstream of theoutlet375 of the recirculation pump370 (FIG. 4).

Having described exemplary embodiments of the roll-to-rollelectroless plating system300, a context has been provided for describing further details of methods for controlling the dissolved oxygen content to be at its desired low range (e.g., in the range of about 0.5 to about 2 parts per million). As described above, an amount of dissolved oxygen in theplating solution310 is measured usingoxygen sensor360. The measured amount of dissolved oxygen is compared to a target range of dissolved oxygen. If the measured amount of dissolved oxygen is greater than the target range of dissolved oxygen, then the rate of injecting the inert gas is increased, for example by further opening a needle valve through which the inert gas flows to increase the flow rate. If the measured amount of dissolved oxygen is less than the target range of dissolved oxygen, then the rate of injecting the inert gas is decreased, for example by further closing a needle valve through which the inert gas flows to decrease the flow rate.

In some embodiments, the measuring of the amount of dissolved oxygen can be repeated at specified time intervals, for example once every five minutes or once every hour. During start-up of the electroless plating process, prior to injecting inert gas, theplating solution310 tends to be somewhat oxygen rich. Therefore, it can be advantageous to measure the dissolved oxygen content at a relatively high repetition frequency (e.g., once every five minutes) during a start-up phase, and then to measure the dissolved oxygen content at a lower repetition frequency (e.g., once per thirty minutes) after the system has stabilized and the dissolved oxygen content has reached the target range.

In some embodiments, measurement of dissolved oxygen content can also be initiated by thecontroller315 if it detects that an environmental condition has changed. For example, a measurement can be initiated if thecontroller315 senses that the temperature of theplating solution310 has changed by more than a predetermined threshold, as gas solubility is a function of temperature.

In some embodiments, measurement of dissolved oxygen content can also be initiated when a system operating condition changes. For example, a measurement can be initiated if thepan cover328 is removed for service, thereby exposing the surface of theplating solution310 to the air. Likewise, a measurement can be initiated whenfresh plating solution310, or components of theplating solution310, are added to thesump330.

In some embodiments, measurement of dissolved oxygen content can also be initiated when an indication is detected that the system may not be performing in the intended manner. For example, a measurement can be initiated if it is observed that elements of theplating solution310 are plating onto extraneous surfaces other than the intended features on thesubstrate250.

In some embodiments, a user interface can be provided to enable the measurement of dissolved oxygen to be manually initiated by an operator. For example, if it is observed that the system performance has been degraded.

For embodiments where the inert gas is injected into theplating solution310 for delivery into both thesump330 and thepan320, the rates of injection can be independently controlled bycontroller315. For example, the injection of the inert gas into theplating solution310 for delivery into thesump330 can be done at a first rate, and the injection of inert gas into theplating solution310 for delivery into thepan320 can be done at a second rate that is different from the first rate.

FIG. 3 shows theoxygen sensor360 submerged within theplating solution310 inpan320. In some embodiments, if theoxygen sensor360 is kept within theplating solution310, metal can deposit on it, thereby affecting its performance.FIG. 4 shows an embodiment where theoxygen sensor360 is configured to be repositionable. Under control ofcontroller315, amotor362 controllably lowers theoxygen sensor360 to dip it into the plating solution310 (e.g., through an opening in the pan cover328) in order to measure dissolved oxygen content. Thecontroller315 can then control themotor362 to raise theoxygen sensor360 to remove it from the plating solution after the measurement is made. Data indicating the measured amount of dissolved oxygen can be sent tocontroller315 either before or after theoxygen sensor360 is removed from theplating solution310.

FIG. 7 shows a high-level system diagram for anapparatus400 having atouch screen410 including adisplay device420 and atouch sensor430 that overlays at least a portion of a viewable area ofdisplay device420.Touch sensor430 senses touch and conveys electrical signals (related to capacitance values for example) corresponding to the sensed touch to acontroller480.Touch sensor430 is an example of an article that can be printed on one or both sides by theflexographic printing system100 and plated using an embodiment of roll-to-rollelectroless plating system300 with low dissolved oxygen content described above.

FIG. 8 shows a schematic side view of atouch sensor430.Transparent substrate440, for example polyethylene terephthalate, has a firstconductive pattern450 printed and plated on afirst side441, and a secondconductive pattern460 printed and plated on asecond side442. The length and width of thetransparent substrate440, which is cut from the take-up roll104 (FIG. 1), is not larger than the

flexographic printing plates

112,122,132,142 of flexographic printing system100 (FIG. 1), but it could be smaller than the

flexographic printing plates

112,122,132,142.

FIG. 9 shows an example of aconductive pattern450 that can be printed on first side441 (FIG. 8) of substrate440 (FIG. 8) using one or more print modules such as

print modules

120 and140 of flexographic printing system (FIG. 1), followed by plating using an embodiment of roll-to-roll electroless plating system300 (FIGS. 3 and 4).Conductive pattern450 includes agrid452 includinggrid columns455 of intersecting

fine lines

451 and453 that are connected to an array ofchannel pads454.Interconnect lines456 connect thechannel pads454 to theconnector pads458 that are connected to controller480 (FIG. 7).Conductive pattern450 can be printed by asingle print module120 in some embodiments. However, because the optimal print conditions forfine lines451 and453 (e.g., having line widths on the order of 4 to 8 microns) are typically different than for printing thewider channel pads454,connector pads458 andinterconnect lines456, it can be advantageous to use oneprint module120 for printing the

fine lines

451 and453 and asecond print module140 for printing the wider features. Furthermore, for clean intersections of

fine lines

451 and453, it can be further advantageous to print and cure one set offine lines451 using oneprint module120, and to print and cure the second set offine lines453 using asecond print module140, and to print the wider features using a third print module (not shown inFIG. 1) configured similarly to print

modules

120 and140.

FIG. 10 shows an example of aconductive pattern460 that can be printed on second side442 (FIG. 8) of substrate440 (FIG. 8) using one or more print modules such as

print modules

110 and130 of flexographic printing system (FIG. 1), followed by plating using an embodiment of roll-to-roll electroless plating system300 (FIGS. 3 and 4).Conductive pattern460 includes agrid462 includinggrid rows465 of intersecting

fine lines

461 and463 that are connected to an array ofchannel pads464.Interconnect lines466 connect thechannel pads464 to theconnector pads468 that are connected to controller480 (FIG. 7). In some embodiments,conductive pattern460 can be printed by asingle print module110. However, because the optimal print conditions forfine lines461 and463 (e.g., having line widths on the order of4 to8 microns) are typically different than for thewider channel pads464,connector pads468 andinterconnect lines466, it can be advantageous to use oneprint module110 for printing the

fine lines

461 and463 and asecond print module130 for printing the wider features. Furthermore, for clean intersections of

fine lines

461 and463, it can be further advantageous to print and cure one set offine lines461 using oneprint module110, and to print and cure the second set offine lines463 using asecond print module130, and to print the wider features using a third print module (not shown inFIG. 1) configured similarly to print

modules

110 and130.

Alternatively, in some embodimentsconductive pattern450 can be printed using one or more print modules configured like

print modules

110 and130, andconductive pattern460 can be printed using one or more print modules configured like

print modules

120 and140 ofFIG. 1 followed by plating using an embodiment of roll-to-roll electroless plating system300 (FIGS. 3 and 4).

With reference toFIGS. 7-10, in operation oftouch screen410,controller480 can sequentially electrically drivegrid columns455 viaconnector pads458 and can sequentially sense electrical signals ongrid rows465 viaconnector pads468. In other embodiments, the driving and sensing roles of thegrid columns455 and thegrid rows465 can be reversed.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

PARTS LIST

100 flexographic printing system
102 supply roll
104 take-up roll
105 roll-to-roll direction
106 roller
107 roller
110 print module
111 plate cylinder
112 flexographic printing plate
113 raised features
114 impression cylinder
115 anilox roller
116 UV curing station
120 print module
121 plate cylinder
122 flexographic printing plate
124 impression cylinder
125 anilox roller
126 UV curing station
130 print module
131 plate cylinder
132 flexographic printing plate
134 impression cylinder
135 anilox roller
136 UV curing station
140 print module
141 plate cylinder
142 flexographic printing plate
144 impression cylinder
145 anilox roller
146 UV curing station
150 substrate
151 first side
152 second side
200 roll-to-roll electroless plating system
202 supply roll
204 take-up roll
205 web advance direction
206 drive roller
210 plating solution
220 pan
222 lower flood bar
224 upper flood bar
230 sump
232 lower lift pump
233 pipe
234 upper lift pump
235 pipe
236 freefall return
240 air inlet tube
250 substrate
251 first surface
252 second surface
300 roll-to-roll electroless plating system
302 supply roll
304 take-up roll
305 web advance direction
306 drive roller
310 plating solution
315 controller
320 pan
328 pan cover
330 sump
331 inlet
332 pan-replenishing pump
333 pipe
334 tee
335 outlet
336 drain pipe
338 sump cover
339 bottom
340 inert gas source
341 inert gas inlet
342 plumbing assembly
343 orifices
344 bubbles
345 inert gas source
348 filter
350 substrate
351 first surface
352 second surface
360 oxygen sensor
362 motor
370 recirculation pump
371 orifices
372 inlet line
373 inlet
374 outlet line
375 outlet
376 inert gas source
377 filter
378 tee
379 plumbing assembly
380 injector
382 converging tube segment
384 diverging tube segment
385 flow direction
386 throat
388 inlet
389 inert gas
400 apparatus
410 touch screen
420 display device
430 touch sensor
440 transparent substrate
441 first side
442 second side
450 conductive pattern
451 fine lines
452 grid
453 fine lines
454 channel pads
455 grid column
456 interconnect lines
458 connector pads
460 conductive pattern
461 fine lines
462 grid
463 fine lines
464 channel pads
465 grid row
466 interconnect lines
468 connector pads
480 controller
D1 diameter
D2 diameter

Claims

1. A roll-to-roll electroless plating system, comprising:

a sump containing a first volume of a plating solution;

a distribution system for injecting an inert gas into the plating solution.

2. The roll-to-roll electroless plating system ofclaim 1, wherein the distribution system is configured to inject micro-bubbles of the inert gas into the plating solution, wherein the micro-bubbles have a diameter between about one micron and one millimeter.

3. The roll-to-roll electroless plating system ofclaim 1, wherein the plating substance is copper, silver, nickel or palladium.

4. The roll-to-roll electroless plating system ofclaim 1, wherein the inert gas is nitrogen or argon.

5. The roll-to-roll electroless plating system ofclaim 1, wherein the distribution system is configured to inject the inert gas into the plating solution in the sump.

6. The roll-to-roll electroless plating system ofclaim 1, further including a recirculation system including:

a recirculation pump including an inlet and an outlet;

an inlet line for moving plating solution from the sump to the pump inlet; and

an outlet line for returning plating solution from the pump outlet to the sump.

7. The roll-to-roll electroless plating system ofclaim 6, wherein the distribution system is configured to inject the inert gas into the inlet of the recirculation pump.

8. The roll-to-roll electroless plating system ofclaim 6, further comprising a filter in the outlet line.

9. The roll-to-roll electroless plating system ofclaim 6, further including an injector downstream of the recirculation pump outlet, the injector including:

a converging tube segment having a diameter that decreases with distance from the recirculation pump outlet;

a diverging tube segment downstream of the converging tube segment, the diverging tube segment having a diameter that increases with distance from the converging tube segment;

a throat formed at a junction of the converging tube segment and the diverging tube segment; and

an inlet for the inert gas in proximity to the throat.

10. The roll-to-roll electroless plating system ofclaim 1, wherein the distribution system includes a plumbing assembly having a plurality of distributed orifices for injecting the inert gas into the plating solution for providing bubbles of inert gas into the sump.

11. The roll-to-roll electroless plating system ofclaim 10, wherein the plumbing assembly is disposed proximate to a bottom of the sump.

12. The roll-to-roll electroless plating system ofclaim 1, wherein the distribution system is configured to inject the inert gas into the pipe through which plating solution is moved from the sump to the pan.

13. The roll-to-roll electroless plating system ofclaim 12, further including an injector downstream of the pan-replenishing pump outlet, the injector including:

a converging tube segment having a diameter that decreases with distance from the pan-replenishing pump outlet;

a throat formed by a junction of the converging tube segment and the diverging tube segment; and

an inlet for the inert gas in proximity to the throat.

14. The roll-to-roll electroless plating system ofclaim 1, further comprising an oxygen sensor.

15. The roll-to-roll electroless plating system ofclaim 14, further comprising a controller, wherein the controller is configured to receive data from the oxygen sensor and to control a rate of injection of the inert gas into the plating solution in response to the data received from the oxygen sensor.

16. The roll-to-roll electroless plating system ofclaim 15, wherein a dissolved oxygen content of the plating solution is controlled to be between 0.5 and 2 parts per million.

17. The roll-to-roll electroless plating system ofclaim 1, further comprising a drain pipe extending from the pan into the the sump for draining plating solution from the pan to the sump, such that plating solution in the drain pipe is not exposed to air.

18. The roll-to-roll electroless plating system ofclaim 1, wherein the sump further includes a sump cover.

19. The roll-to-roll electroless plating system ofclaim 1, wherein the pan further includes a pan cover.

20. The roll-to-roll electroless plating system ofclaim 1, wherein the distribution system further includes a static mixer.

21. The roll-to-roll electroless plating system ofclaim 1, wherein the predetermined locations include features printed onto the web of media with ink including a catalyst for plating.

22. An article having features that were plated using the roll-to-roll electroless plating system ofclaim 1.

23. The article ofclaim 22, wherein at least some of the features have widths between 2 microns and 10 microns.