Copper Inks for Printed Electronics

I recently spotted a patent for copper based metallic inks jointly granted to Applied Nanotech Holdings, Inc. and Ishihara Chemical Co., Ltd.  The conductive inks I have previously reported on have been silver or graphene based, these can be very expensive and so there is always interest in a lower cost alternative.  Copper metal is a standard in the electronics industry and is about one tenth the cost of silver.

Patent summary:

US8404160   -  METALLIC INK

Inventor(s): LI YUNJUN [US]; ROUNDHILL DAVID MAX [US]; LI XUEPING [US]; LAXTON PETER B [US]; ARIMURA HIDETOSHI [US]; YANIV ZVI [US]

Applicant(s): APPLIED NANOTECH HOLDINGS INC [US]; ISHIHARA CHEMICAL CO LTD [JP]

Filing date: 31/03/2009
Issue date: 26/03/2013

Abstract
A metallic ink including a vehicle, a multiplicity of copper nanoparticles, and an alcohol. The conductive metallic ink may be deposited on a substrate by methods including inkjet printing and draw-down printing. The ink may be pre-cured and cured to form a conductor on the substrate.

Claim 1:

1. A conductive metal ink comprising: a vehicle comprising two or more oxygenated organic compounds; copper nanoparticles; and a medium length chain aliphatic alcohol, wherein the ink does not comprise a binder.

There are a further 23 claims giving more details of the components mentioned in claim 1.

Two figures from the patent give a flow chart for two processes which can be used:

Direct printing:

Patterning after the ink deposition:

Phil’s Comments

This is a key patent for copper inks and has a broad first claim which had to be modified from the original application by the addition of the restriction that the ink does not contain a binder and I suspect this was to get around some of the prior art identified by the patent examiner.

Six very detailed examples are given which illustrate the invention and provide further details of the printing process, the curing or sintering that is applied to produce the conductive tracks on a range of materials including flexible substrates.

Silver Nanoparticle Inks for Printed Electronics

Xerox are continuing to add to their patent portfolio of silver nanoparticle inks for printed electronics.  A new patent was granted on 4th Dec 2012 adding to the one already granted on 17th April 2012.  These two patents are summarised below:

US8158032  (B2)  -  SILVER NANOPARTICLE INK COMPOSITION FOR HIGHLY CONDUCTIVE FEATURES WITH ENHANCED MECHANICAL PROPERTIES

Abstract: A conductive ink composition comprising organic-stabilized silver nanoparticles and a solvent, and a polyvinyl alcohol derivative resin of Formula (1) wherein R1 is a chemical bond or a divalent hydrocarbon linkage having from about 1 to about 20 carbons; R2 and R3 are independently an alkyl, an aromatic or substituted aromatic group having from about 1 to about 20 carbon atoms; x, y and z represent the proportion of the corresponding repeat units respectively expressed as a weight percent, wherein each repeat unit is randomly distributed along polymer chain, and the sum of x, y and z is about 100 weight percent, and wherein the polyvinyl alcohol derivative resin is present in an amount of from 0.1 to about 5 weight percent of the ink composition.

US8324294  (B2)  -  SOLVENT-BASED INKS COMPRISING SILVER NANOPARTICLES

Abstract: High performing nanoparticle compositions suitable for printing, such as by inkjet printing, are provided herein. In particular, there is provided a conductive ink formulation comprising silver nanoparticles which has optimal performance, such as, reduced coffee ring effect, improved adhesion to substrates, and extended printhead de-cap time or latency time. The ink formulation comprises two or more solvents and a resin.

Phil’s Comments

The key technology improvements over the general prior art are for the development of inks which do not dry out and clog the printhead along with improvements in the adhesion of the ink to the substrate, reduction of the coffee ring effect and reduction of particle aggregation which leads to black dots in the printed lines.

The improved adhesion is as a result of the incorporation of a resin in the ink based on a polyvinyl alcohol derivative.  The earlier patent goes into some detail over the formulae for these resins.

The extended drying times to prevent printhead clogging are the result of incorporation of two or more ink vehicles (solvents) with vapour pressure properties as described in the second patent.  Typical compositions are based on aliphatic hydrocarbons comprising at least one cyclohexane ring, cyclic terpene, cyclic terpinene, terpineol, methyl naphthalene, and mixtures thereof.  Typical drying times are in excess of 5 hours and one claim states up to about 1 week.

The nanoparticles are stabilised with organo-amines, the first patent gives more detail on these structures,  a preferred compound is dodecylamine.

 

As always please leave a comment if you require further details or are interested in patent landscapes related to these conductive inks.

Printed Electronics using Graphene based Inks

When I spotted a recent granted patent with the title Printed Electronics, it was an obvious candidate for a Phil’s Patent Pick.  US8278757 was published on 2nd October 2012 and jointly assigned to Vorbeck Materials Corp. and Univ. of Princeton.  It was originally filed on 9th January 2009 and has a priority date of 5th February 2008.

The patent has quite broad claims and describes printed electronics devices made using a conductive ink comprising functionalized graphene sheets and a binder.  I don’t always reproduce the claims but in this case they are fairly simple to follow:

1. A printed electronic device, comprising a substrate comprising at least one surface, wherein a layer of an electrically conductive ink has been applied to a portion of the surface, and wherein the ink comprises functionalized graphene sheets and at least one binder.

2. The device of claim 1, wherein the substrate comprises paper and/or cardboard.

3. The device of claim 1, wherein the substrate comprises at least one polyolefin.

4. The device of claim 1, wherein the substrate comprises at least one polyimide.

5. The device of claim 1, wherein the ink further comprises at least one dispersant.

6. The device of claim 1, wherein the binder is a polymeric binder.

7. The device of claim 6, wherein the binder is one or more of poly(ethylene oxide), poly(propylene oxide), and ethylene oxide/propylene oxide copolymers.

8. The device of claim 1, wherein the ink further comprises at least one metal component.

9. The device of claim 8, wherein the metal is silver and/or copper.

10. The device of claim 1, wherein the ink further comprises at least one electrically conductive polymer.

11. The device of claim 1, wherein the ink further comprises at least one carbonaceous material other than the functionalized graphene sheets.

12. The device of claim 1, wherein the functionalized graphene sheets have a surface area of from about 300 to about 2630 m²/g.

13. The device of claim 1, wherein the functionalized graphene sheets have a surface area of from about 400 to about 2400 m²/g.

14. The device of claim 1, wherein the functionalized graphene sheets have a carbon to oxygen ratio of about 60:40 to 20:1.

15. The device of claim 1, further comprising one or more components selected from the group consisting of processors, memory chips, batteries, resistors, diodes, capacitors, and transistors.

16. The device of claim 1 in the form of an integrated circuit.

17. The device of claim 1 in the form of a printed circuit board.

18. The device of claim 1 in the form of a light-emitting diode display.

19. The device of claim 1 in the form of a radiofrequency identification device and/or a radiofrequency device antenna.

20. The radiofrequency identification device and/or radiofrequency device antenna of claim 19 in the form of a radiofrequency identification device and/or antenna for use with ultra-high frequencies.

21. A method for forming a printed electronic device, comprising the step of applying an electrically conductive ink to a substrate, wherein the ink comprises functionalized graphene sheets and at least one binder.

22. The method of claim 21, wherein the substrate is selected from one or more of paper, cardboard, polyolefin, and polyimide.

23. The method of claim 21, wherein the electrically conductive ink further comprises a carrier.

24. The method of claim 21, wherein the electrically conductive ink further comprises a dispersant.

25. The method of claim 21, wherein the functionalized graphene sheets have a surface area of from about 300 to about 2630 m²/g.

Phil’s Comments

It is worth looking at the examples in the patent.  The printing methods and samples generated for testing are pretty crude and suggest that only simple circuits have been generated such as RFID antennas.  The type of ink suggests that printing processes will be of the gravure or flexo type rather than ink-jet.  However, the wording of the allowed claims suggests that just about any printed electronic device containing a layer that includes graphene sheets with a functional group in a binder would infringe this patent.  The majority of the claims are all about the device and not the material.  The last five claims are about the method.  Vorbeck sell the graphene based inks and with this patent they will require anyone using the inks to enter into some form of agreement with them to make the devices.  It will be interesting to see how this works in practice and whether the patent will stand the test of time.

Recent Patent may be concern for Printed Semiconductor Manufacturers

When looking through granted patents in any technical field it is always a concern if one turns up with broad claims that might impact a wide range of products or manufacturing processes.  Recently I came across one in the printed electronics field which might just be in that category.  Read on to see what it is all about.

US7982296 was granted on 19 July 2011 to the University of Illinois and has the title “Methods and Devices for Fabricating and Assembling Printable Semiconductor Elements”.  The abstract caught my eye because it was referring to flexible devices made on substances comprising polymeric materials and also to stretchable structures.

The invention provides methods and devices for fabricating printable semiconductor elements and assembling printable semiconductor elements onto substrate surfaces. Methods, devices and device components of the present invention are capable of generating a wide range of flexible electronic and optoelectronic devices and arrays of devices on substrates comprising polymeric materials. The present invention also provides stretchable semiconductor structures and stretchable electronic devices capable of good performance in stretched configurations.

I was able to trace the history of this application and found that the earliest documents associated with the filing were back in 2004 and that two patents were eventually granted, the earlier one related to the method for assembling the devices (US7622367) published on 24 Nov 2009 and this one just published being for the devices themselves.  The INPADOC patent family now consists of over 30 documents across several countries including Japan, Korea, Taiwan, and China.

The first claim is the broad one which I believe may give some concern to a number of manufacturers involved in printing inorganic semiconductors.  It reads:

1. An electrical device comprising: a first electrode; a second electrode; and a printable semiconductor element positioned in electrical contact with said first and second electrodes, said printable semiconductor element comprising a unitary inorganic semiconductor structure having at least one cross sectional dimension greater than or equal to about 500 nanometers.

The other 8 claims are all dependant claims and further refine claim 1.  A number of examples are included illustrating the range of devices in mind, some involve dry transfer printing, others solution printing.

The patent description is remarkably detailed with several pages of background references and 46 figures one of which is included below.

FIG. 26A illustrates the steps used to fabricate exemplary bendable thin film transistors devices of the present invention.

If you wish to explore the patent further it is best to review the pdf file which can be downloaded from the Espacenet website.

As always, please leave a comment if you want to discuss this further and visit my IPScope website for details of a range of Strategic IP Management services including patent searches.

Optomec Aerosol Jet metal deposition for Printed Electronics

This is the fourth in the series of Printed Electronics patents granted in 2011.  I was alerted to this via the Boliven patent alert system which sends me an automatic update for any new granted patents with the search terms used in my original PE patent search.

US7987813:

Patent Title: Apparatuses and methods for maskless mesoscale material deposition
Filing Date: 6 Jan 2009
Issue Date: 2 Aug 2011
Inventor(s): Michael J. Renn, Bruce H. King, Marcelino Essien, Gregory J. Marquez, Manampathy G. Giridharan, Jyh-Cherng Sheu
Assignee(s): Optomec Inc.

Abstract

Apparatuses and processes for maskless deposition of electronic and biological materials. The process is capable of direct deposition of features with linewidths varying from the micron range up to a fraction of a millimetre, and may be used to deposit features on substrates with damage thresholds near 100° C. Deposition and subsequent processing may be carried out under ambient conditions, eliminating the need for a vacuum atmosphere. The process may also be performed in an inert gas environment. Deposition of and subsequent laser post processing produces linewidths as low as 1 micron, with sub-micron edge definition. The apparatus nozzle has a large working distance—the orifice to substrate distance may be several millimetres—and direct write onto non-planar surfaces is possible.

Phil’s Comments

This is the latest granted patent covering Optomec’s Maskless Mesoscale Material Deposition (originally termed M3D).  Their recent applications seem to use the Aerosol Jet Printing system description and that is consistent with Optomec’s current website.  There is quite a lot of technical information available on this approach and the reader is referred to their website for more details.  An extract from their website gives a good overview of the system and its applications:

Aerosol Jet systems have the unique ability to produce a wide range of electronic, structural and biological patterns onto almost any substrate. The proprietary process, which is completely different from ink jet industrial printing, utilizes aerodynamic focusing to precisely deliver fluid and nano-material formulations that as required can be optionally post-treated with a highly focused laser or other sintering methods. The resulting patterns can have features that are less than 10 microns wide, with layer thicknesses from 10′s of nanometers to several microns. A recently announced Aerosol Jet Wide Nozzle print head is also available which enables efficient patterning of millimeter scale conductive features (bus bars, backplanes), large area thin film coatings, and selective coatings (insulators, cross-over circuits, encapsulation). Example applications for Aerosol Jet Wide Nozzle deposition capabilities are fuel cells, conformal antennae and Molded Interconnect Devices.

This patent further strengthens Optomec’s patent portfolio which already has close to 20 granted US patents in this field.  A look at the granted patent trends over the past few years shows that while there has been a steady rate of on average 2 patents per year this number is already significantly higher for 2011.

Optomec Granted Patent Trend

 

The Aerosol Jet deposition method has been investigated by a number of companies interested in using this approach for printed electronics including the PETEC organisation in the UK.

Printed Electronics Patents Granted in 2011 – Kovio Inc

This is the third in the series covering patents granted during 2011 in the printed electronics field.

US7977240: Metal Inks For Improved Contact Resistance

Inventor(s)
Joerg Rockenberger, Yu Chen, Fabio Zürcher, Scott Haubrich

Assignee(s)
Kovio, Inc.

Filing date: 13 Feb 2009; Issue date: 12 Jul 2011

Abstract

Metal ink compositions, methods of forming such compositions, and methods of forming conductive layers are disclosed. The ink composition includes a bulk metal, a transition metal source, and an organic solvent. The transition metal source may be a transition metal capable of forming a silicide, in an amount providing from 0.01 to 50 wt. % of the transition metal relative to the bulk metal. Conductive structures may be made using such ink compositions by forming a silicon-containing layer on a substrate, printing a metal ink composition on the silicon-containing layer, and curing the composition. The metal inks of the present invention have high conductivity and form low resistivity contacts with silicon, and reduce the number of inks and printing steps needed to fabricate integrated circuits.

Phil’s Comments:

Kovio Inc. is one of the leading companies involved in printed electronics devices and have made significant progress in printing complex electronic devices such as RFID’s in which not only the antenna but also the associated electronics is printed by a solution deposition process.

Here is an extract from the patent which explains the problem faced in any printing method for electronic devices:

In integrated circuits, the devices (e.g., TFT, capacitors, diodes, etc.) are generally connected to each other with metal lines (i.e., interconnects). Integrated circuits with good performance generally include interconnects with low resistivity, and thus not all metals are suitable for use as interconnects. Typical examples of suitable metals are Al, Cu, Au and Ag. Often, metals used for interconnects in integrated circuits do not form low resistivity contacts with the device electrodes (e.g., gate and source/drain electrodes), which are usually made with n+ and/or p+ doped silicon. Therefore, in order to fabricate integrated circuits with good performance, a contact layer formed between the n+/p+ silicon and the metal lines often provides relatively low resistivity between the devices and the interconnects. Typically, silicides are the preferred contact layers used in microelectronic devices, because they can provide ohmic contacts to heavily doped semiconductors (e.g. n+/p+ silicon and/or germanium).

This patent describes metal ink compositions that have high conductivity and low contact resistance and can therefore reduce the number of inks and printing steps required to manufacture a device.  The patent also describes a method which comprises (a) forming a layer comprising silicon and/or germanium on a substrate, (b) depositing (e.g., by printing) a metal ink composition on the silicon-containing layer, and (c) curing the metal composition. In general, the metal ink compositions comprise a bulk metal and a silicide-forming transition metal source.

More details are available in the full patent specification which can be found here.  Email me or leave a comment if you would like any further details.

Printed Electronics Patents Granted in 2011 – Conductive Ink

This is the second in the series covering patents granted during 2011 in the printed electronics field.

US7968011: Conductive Ink

Inventor(s): Gerardus Cornelis Overbeek, Michael Arnoldus Jacobus Schellekens, Alfred Jean Paul Bückmann

Assignee(s): DSM IP Assets B.V.

Filed: 6 Mar 2007; Issued: 28 Jun 2011

Abstract: A conductive ink comprising 10 to 75 wt % of at least one solvent comprising ≦20 wt % water; 0 to 50 wt % of at least one radiation curable material having a Mn in the range of from 50 to 10,000 g/mol; 5 to 70 wt % of at least one polyurethane having a Mw in the range of from 4,000 to 70,000 g/mol, 0 to 5 wt % of isocyanate-reactive component(s) bearing ionic or potentially ionic water-dispersing groups and a free isocyanate group content <0.5 wt % and 20 to 85 wt % of a conductive material.

The claims provide more details around the various components but rather than copying the claims I’ll explain in simple English.

The problem being solved by this invention is the lack of a common binder that can be used across a range of different conductive ink materials.  The inventors have provided a polyurethane based binder which they have found can be used to create inks suitable for flexography, gravure and ink-jet printing.  The method does not require high temperature curing and leads to good conductivity. Claim 1 requires that a UV radiation curing material is also included with the binder and this gives additional improvements in film properties and faster printing speeds.

The conductive materials are described as any form of conductive particle and the scope is very broad, including nanoparticles of silver or copper.  The particles can be flakes, fibres, nanotubes or mixtures, the particles can be silver coated.

The system requires a solvent which can be alcohol based (e.g. ethanol, iso-propanol, etc.) or any from a broad range of esters, ethers, ketones, etc. and preferably contains less than 10% water.

Any reader interested in the full formulation should refer to the patent for details of the preferred formulations.

Printed Electronics Patents granted in 2011

I recently reviewed the patents that are granted in the field of printed electronics and a recent search indicated that during 2011 there have already been nearly 100 granted patents in this technology sector.  It is not possible to provide a comprehensive overview in this format but over my next few posts I will provide brief details of a few of the patents that caught my eye.  (If anyone is interested in a more thorough analysis or any particular technology field then please leave a comment or get in touch with me and I can provide details of how to obtain the data.)

US7879688 – Methods For Making Electronic Devices With A Solution Deposited Gate Dielectric

Issued: 1st Feb 2011

Inventors: James C. Novack, Dennis E. Vogel, Brian K. Nelson

Assignee: 3M Innovative Properties Company

Abstract:  A method of making an electronic device comprises solution depositing a dielectric composition onto a substrate and polymerizing the dielectric composition to form a gate dielectric. The dielectric composition comprises a polymerizable resin and zirconium oxide nanoparticles.

Granted claim 1:

1. A method of making an electronic device comprising: (a) solution depositing a dielectric composition onto a substrate, the dielectric composition comprising an ultraviolet radiation polymerizable resin comprising tris-(2-hydroxy ethyl) isocyanurate triacrylate, an ultraviolet photoinitiator, and zirconium oxide nanoparticles; and (b) polymerizing the dielectric composition via at least ultraviolet radiation to form a gate dielectric.

The additional claims generally expand on the ZrO2 nanoparticles and dielectric composition which is preferably ink-jet printed.  Further claims elaborate on a method for making the thin-film transistor.

The claims are fairly self explanatory and the method is said to allow a higher charge carrier mobility for a solution deposited semiconductor.  Obviously, the patent can be circumvented by using other types of metal oxide but for those exploring its potential as a dielectric this is a key patent.

Using Boliven for a “Printed Electronics” Patent Search

I was recently exploring the patent search capabilities of www.Boliven.com and thought I’d share the results of a quick review of recent patents including the phrase “printed electronics”.  Simply typing the term “printed electronics” (including the quotes) into the search box returns over 3400 results.  These include patents and applications from US, Europe, Japan, Korea and the PCT filings.  To quickly get to just the patents you can use the analyze function and the top chart is an overview of the patents granted by year.

Clicking on the yellow sector of the pie chart takes you to the summary list of granted patents.  This list can be further refined by selecting only patents published in 2011 from the left hand filter options.  This reduces your list to the 57 patents granted this year.  The results are sorted by relevance and the third one in the list caught my eye and the brief summary showing where the  term “printed electronics” appears in the text is reproduced below.

I found the ease with which you can scroll down the results and quickly get a feel for the most relevant patents highly valuable.  You can access the full text of any patent and follow up on the detail.  The full result set can be exported or saved to a list for sharing with colleagues or for working on later.

To complete the story here is the first claim from the Soligie Inc. patent I found:

1. A process for creating electrical circuits or circuit elements using imaged gravure printing plates, the process comprising: obtaining a gravure printing plate imaged by etching a substantially flat plate; mounting the imaged gravure printing plate to a printing apparatus, wherein the imaged gravure printing plate comprises an image configured to create an electrical circuit or circuit element with features of 10 microns or less, and wherein the printing apparatus comprises a cylinder, and a carriage adapted to be moved into contact with the cylinder, wherein a substrate to be printed is mounted to one of either the cylinder or the carriage, and the imaged gravure printing plate is mounted to the other of the cylinder or the carriage; applying a material to be deposited on the substrate to the imaged gravure printing plate wherein the material is present in the etched areas of the imaged gravure printing plate; directly contacting the substrate with the imaged gravure printing plate to transfer the material from the imaged gravure printing plate to the substrate; and removing the substrate from contact with the imaged gravure printing plate, wherein the material forms a first patterned layer of an electrical circuit or circuit element on the substrate corresponding to the image of the imaged gravure printing plate.

Hopefully this has given you a brief insight into how easily the modern patent search tools can help you find relevant prior art or competitors’ patents to inform your own business or technology strategy.  Of course if you wanted to do a thorough analysis you would need to construct a much more comprehensive search term and use a combination of keywords and patent codes to be sure of identifying all the relevant material in the databases.  Post a comment if you want any more details on fine tuning this type of search.

Kovio Inc. patents: Printed Electronics Devices at lower cost

Background

The radio frequency identification (RFID) market is huge, already over £2 billion.  Within this market passive RFID is expected to be the prime candidate for printing but so far the main thrust has been the printing of the antennae.  Often silver inks are used but the price fluctuations of silver (currently very high) cause many companies to look for alternatives such as copper, aluminium and organic conductive polymers.  The expensive part of an RFID tag is the chip and there are not many companies who have tried printing the chips.  Kovio Inc. was the first using nanosilicon on a variety of substrates.

The real advantage of printed RFID is the potential to produce tags and labels cheaply, perhaps even being able to print them directly as is done with barcodes today.  Applications like library tags, that currently use high cost silicon memory chips, tend to use HF rather than UHF and I believe this is where the potential for printed RFID is to be found.

Kovio Patents

Kovio Inc. were recently granted a third patent in a series which all relate to methods for making devices such as RFID tags at lower cost.  The key phrase from their abstract is:

The present invention advantageously provides semiconducting thin film structures having qualities suitable for use in electronics applications, such as display devices or RFID tags, while enabling high-throughput printing processes that form such thin films in seconds or minutes, rather than hours or days as with conventional photolithographic processes.

Their recent series of patents are summarized in the table below:

The most recent patent can be viewed here and has 67 method claims, the earlier patents relate to the materials and the thin film structure.  The 7553545 patent is also interesting in that it details the linewidths and gaps that can be printed.