FI121562B - Method for the manufacture of conductors and semiconductors - Google Patents

Description

Method for the manufacture of conductors and semiconductors

The invention relates to sintering and products made by sintering. In particular, the invention relates to the formation of conductive structures on a substrate by sintering metallic or semiconductor nanoparticles.

Metal nanoparticles are known to be sintered, for example, in applications in printable electronics to provide conductive structures. It is known that metallic nanoparticles melt microparticles at lower temperatures in the so-called. surface-phonon softening 10. This is because the number of "loose" atoms on the particle surface increases significantly as the total particle size decreases. The phenomenon is reasonably well known both theoretically and experimentally, although some aspects of the phenomenon have not yet been fully explained. For example, it has not been extensively explained in the literature that when nanoparticles are lined with a thin layer of organic compound and applied to solvents by means of solvents, it is found that the sintering temperature may be significantly lower than the melting point of the individual particles.

Although the sintering temperature of nanoparticles is substantially lower than that of microparticles, prior art solutions require external heating to sinter them.

Sintering is accomplished by raising the temperature in the oven or by exposing the particles to UV light or a hot plate or roll. The temperatures required are generally at least 100 ° C. Only very small semiconductor particles can be sintered at low temperatures, but here too, the performance of the sintered structures remains poor.

Heating limits the choice of substrates used in the methods. Many of the plastic or paper substrates that are inexpensive in cost are deformed or decomposed at the temperatures required for sintering. Indeed, there is a strong tendency in the art to produce sintering processes and sinterable material compositions suitable for use at low temperatures. Some such known methods are described e.g. WO publications 2005/061598 and 2004/075211.

2

The object of the invention is to provide a completely novel method of sintering nanoparticles, which is suitable for use at very low temperatures, even at room temperature, and at normal pressure.

It is also an object of the invention to provide a new electronic product, an electronics duo and a use.

The invention is based on the observation that a voltage (electric field) applied over the lined nanoparticles initiates sintering of the nanoparticles even at low temperatures. Thus, in the process of the invention, particulate material containing conductive or semiconductor lined nanoparticles is sintered to increase this electrical conductivity by applying a voltage across the particulate material.

Typically, the method is carried out using a substrate having a surface at least partially provided with a nanoparticulate layer comprising conductive or semiconducting lined nanoparticles. The nanoparticles in the layer are sintered by applying a voltage across the layer. The voltage generates a tunneling current through the layer, which causes the particles to sinter in a new way, which will be described in more detail later. Thus, single, for example, metallic nanoparticles can be uniformly formed into a conductive metallic conductor pattern or layer between the voltage electrodes.

The product of the invention comprises a substrate and a conductor or semiconductor pattern formed by sintering nanoparticles on the substrate surface. The pattern is sintered by a voltage applied to the layer containing the lined conductor or semiconductor nanoparticles. The sintered pattern is characterized in that it is of good quality and very homogeneous, since sintering proceeds systematically from the center of the voltage electrodes to the electrodes, and not randomly from here.

The electronics module according to the invention comprises at least one electrical circuit having 30 initial electrical properties and a certain functionality. The module further comprises at least one nanoparticulate zone to which a voltage can be applied to at least partially sinter the zone. When sintered, the zone is adapted to electrically connect at least two conductive regions contained in the electrical circuit to alter the electrical properties or functionality of the electrical circuit.

3

The invention arose when an experimental arrangement was made in order to understand the sintering of nanoparticles and to measure possible predicted electrical nonlinearities by placing a non-citrated dried silver nanoparticle pulp in a gap formed between two thin metal electrodes at room temperature. As expected, it was observed that the non-sintered structure was slightly conductive. At about 100 μιη electrode gap and at about five volts (current <1 mA), the conductivity increased dramatically, resulting in a structure having a conductivity similar to that produced by sintering at temperatures above 100 ° C. After the voltage was removed, the structure remained in the lead in all tests performed. Increasing the spacing between the electrodes to about twice caused the voltage to lead to sintering 10 also to be doubled. A closer examination showed that silver was almost completely sintered in the process.

Thus, the invention is particularly applicable to such particles where the phenomenon is detectable with sufficient intensity. Such particles include in particular metal conductor particles 15 and semiconductor particles having an average dimension of less than 100 nm and having a thin lining. Thus, many nanoparticles which are also commonly used in conventional sintering applications are suitable for use in the present invention. These have a size of 1 to 100 nm, typically 1 to 50 nm.

Nanoparticles are typically deposited on the substrate surface in the form of lined (agglomerates). They may be delivered to the substrate in the form of a dispersion or suspension with a liquid or paste carrier, but they may also be applied in powder form. Solvents, inks and polymer dispersions are typically used as carriers. The most common application techniques are printing and printing. However, the invention is not limited to any particular application method or particulate powder or pasta composition, although some methods may provide a particular advantage. By particulate material we generally refer to nanoparticulate lipid materials in which the particle density is sufficient to effect coalescence (coalescence).

In particular, we have found an embodiment of applying a voltage across an nanoparticle-dried film to an impedance of less than the resistance of the conductive film by tunneling. The film is then sintered from the center towards the electrodes. Further, if a resistor is applied in series with the voltage source or the voltage control is terminated shortly after the onset of sintering (e.g. based on a timer or impedance measurement), the metal particles of the film 4 may be partially sintered. This allows the production of extremely thin line widths. The resistivity causes the voltage source to change into a power source as sintering progresses, effectively making the process self-regulating. It is essential here that, at the desired sintering step, the power received by the particulate material decreases to less than the power required to proceed with sintering.

More specifically, the method according to the invention is characterized by what is said in the characterizing part of claim 1.

The uses according to the invention are characterized by what is stated in claims 25 and 26.

The electronic product according to the invention is characterized by what is said in the characterizing part of claim 27.

15

The electronics module according to the invention is characterized by what is said in the characterizing part of claim 32.

The invention provides considerable advantages. It allows complete sintering of metal particles already at room temperature without an external source of heat. After the voltage is applied, the temperature at the center of the electrodes rises to a sintering temperature, usually within a few seconds, and the sintering itself begins within a few hundred milliseconds. That is, sintering is remarkably fast compared to conventional methods and does not produce heat on the substrate. Thus, conductive patterns can be obtained on the substrate regardless of the substrate's heat resistance. The Sint decomposition temperature of semiconductor nanoparticles is generally higher than the metal nanoparticles, but also in these cases the sintering temperature can be significantly reduced.

Thus, in the case of metal and semiconductor particles suitable for sintering (hereinafter also referred to as: 30 electric sintering or electric sintering) by the electric field described herein, the process can reduce the sintering temperature by at least tens, typically several hundred degrees. For example, for 7 nm silver particles, sintering is already occurring at room temperature.

5

Since sintering does not require mechanical contact with the pulp to be sintered, the roughness or inhomogeneity of the substrate also does not pose a problem, as is generally the case with pressurized processes. As a result, the method is also better suited to sintering three-dimensional conductor patterns than known methods.

5

Because the method is based on an electric field, it allows not only sintering but also the construction of patterns. The method is particularly suitable for the production of thin line widths, for example in applications related to circuit board electronics, printable electronics and component manufacturing. Also, component contacting and metal penetrations can be achieved using the method.

We have found that the temperature of the nanoparticle layer increases as the particles fuse. Since the increase in temperature of the nanoparticle layer is entirely caused by the electric field, dielectric substrates do not experience corresponding heating. Furthermore, since the mass of the layer is very small, only a negligible amount of heat is transferred to the substrate. Thus, the process is applicable to substrates which significantly alter their physical or chemical properties (shrink, decompose, bend, change color, etc.) at elevated temperature and / or pressure. Such substrates include many typical plastics and papers. Preferably, the sintering according to the invention is carried out at a temperature below 100 ° C, particularly preferably at a temperature from about 0 ° C to 50 ° C. In a preferred embodiment, the electro sintering is carried out at room temperature, which makes almost any substrate whose surface is only sufficiently smooth to receive a uniform nanoparticle layer, suitable substrates.

The method can be used in entirely novel applications or it can be used in known applications where either voltage and / or nanoparticle layer is naturally available. Examples of applications include manufacture of programmable memory, manufacturing of surge protector, passivation of backup sensors, e.g.

The processing of small patterns is simple by the method because since the sintering is controlled by an electric field, the resolution level of the patterns need not be achieved mechanically.

6

The various embodiments of the invention will now be described in more detail with reference to the accompanying drawings.

Fig. 1 is a flowchart illustrating one embodiment of the present method, Fig. 2 is a side cross-sectional view of one possible process for fabricating a transistor using electric sintering, Fig. 3 is a plan view 5 is a perspective view of an apparatus according to one embodiment for sintering a pattern on the surface of a web-like substrate.

In order to understand the present invention, the physical phenomenon that can be observed on the surface of the substrate when applying a voltage over the nanoparticle layer is briefly described below.

It is known that, when the lined nanoparticles are three-dimensional on the surface, the surface can conduct electricity if its thermal energy kBT is higher and / or of the same order as the so-called. the charge energy e1 / C, where e is the electron charge and C is the capacitance between the two particles. According to this, the conductivity of the layer should be very low at low temperatures. In addition, there is a so-called interactions between the particles. Casimir's power, which effectively reduces the charge energy and causes such a set of particles of small lined particles to conduct current by tunneling at already reasonably low temperatures.

25

The following deduction circuit illustrates one way of modeling the voltage-induced sintering process when using a sintered layer containing a polymer shell-lined nanoparticle: - Because the layer has low electrical conductivity initially, the layer also has poor thermal conductivity. (However, it must be noted that in order to trigger this phenomenon, both electrical and thermal conductivity must be substantially non-zero.) - As the voltage increases, the layer tends to become warm (poor thermal conductivity).

7 - Since the electrical conductivity is based on thermal excitation, the electrical conductivity of the layer improves as the temperature increases. In addition, a strong electric field increases the conductivity of the surface because the voltage partially overrides the so-called. Coulombise's blockade.

- The capacity of the layer to draw power from an external voltage source increases (P = U2 / R).

5 - This accelerates the temperature rise in the middle layer (in the direction between the electrodes).

- When the central portion reaches a critical temperature, the polymeric shell of the central particles melts and the particles drift closer to one another.

- The tunnel current between adjacent particles increases and at the same time improves thermal conductivity.

- When a few nanoparticles melt together, their total effective surface area increases and they transfer their heat through the electron gas to the other particles.

Also, the particles near the melted nanoparticles melt and the metallization 15 proceeds from the center toward the voltage electrodes. If the event is allowed to continue, the entire layer between the electrodes will sinter.

From the exemplary chain of events above, it is found that the invention can utilize the built-in positive feedback between dense nanoparticle systems for conducting sintering to achieve sintering. Thus, sintering is preferably controlled by a constant voltage rather than a constant current. Extremely low power is required to perform the method because the system is thermally insulated due to the extremely fast warm-up due to positive feedback. In addition, the nanoparticles have a low specific heat and mass, so a small amount of heat increases their temperature.

Electronic sintering is basically a complex phenomenon. The theory behind the phenomenon is described above only to the extent that it may assist the reader in understanding and reproducing the method of the invention and its embodiments. Thus, in the process, heat is not introduced directly into the system, as in the known sintering processes, but sintered at a voltage which results in positive thermal feedback and thus rapid sintering. An interesting feature of the process is, therefore, the increasing sintering rate after initiation of sintering. The achievable sintered structures are also of good quality, i.e. durable and homogeneous in conductivity.

8

If instead of voltage biasing the system is controlled by current bias or high resistor, positive feedback can be prevented and sintering will not occur (at least not so easily). If the value of the resistor is appropriate or the voltage is cut off at a given moment, the event can be adjusted 5 so that only the central part of the electrodes is sintered and the other parts are not metallized. This makes it possible to process wires that are clearly smaller than the electrodes. We have found that a line width of up to 1/5, even less than 1/10 of the electrode distance can be achieved. Naturally, this is also affected by the size of the nanoparticles. For example, using 10 nm particles and a 50 μπι: η electrode gap, it is possible to fabricate less than 5 μηι: η conductors. With smaller particles, it is possible to produce even smaller conductors. A narrower electrode gap also allows for the production of thinner conductors.

Both metallic nanoparticles and semiconductor denan particles can be used in the process. For both, exemplary application areas will be described in more detail later. Among the metals useful are in particular silver, gold, copper, platinum, nickel, palladium, iron, titanium, tin and alloys thereof. Particularly mentioned are semiconductors based on silicon, germanium, titanium, zinc, GaAs and indium. Oxide semiconductors can also be used, especially titanium dioxide and zinc oxide.

20

The nanoparticle liner (encapsulation layer) is preferably thin to provide a sufficient (sintering) tunneling current at operating temperature. By thin lining we mean primarily that the coating layer thickness is less than 30%, typically less than 1-20%, of the agglomerate diameter. Typically, the coating has a thickness of about 1-5 nm. Organic compounds such as polymers are typically used as lining materials. The softening temperature of the lining material is preferably low, generally less than or equal to the melting temperature of the nanoparticles, typically about 50-150 ° C. Crucially, the microscopic warming caused by electrical sintering enables co-sintering (coalescence) of adjacent nanoparticles.

30

Particle coating has a clear connection to the success of electro sintering. According to a preferred embodiment, the sintered nanoparticles are coated (Encapsulated) with a polymer shell (e.g., PEO, PPO), which prevents the particles from clustering before being placed on the substrate. This is important, for example, in ink-jet printing, where the nozzles are clogged by particles adhered to the printer 9. In addition to the application, similar coating also has the advantage of the sintering process itself. The uncoated particles would partially adhere to one another prior to the "forced" sintering, whereby the energy stored in the material would be significantly less than that of the clearly separated particles. Such a material is brittle and very poorly conductive and cannot be sintered in a similar way, since some of the energy (potential) stored in the material has been discharged.

In summary, the method is thus based on the heating of the particle material al-10 by the power it draws from the voltage source and the increasing power consumption caused by further heating, and thus at least in the early stages of the sintering process. Particularly dense but still substantially non-zero conductivity and thermal conductivity of lined nanoscale particles are suitable as a starting material. Thus, after the voltage is applied, a local temperature rise is observed in the layer, which further causes the sintering event to propagate in the particulate material substantially in the direction of the electric field.

The nanoparticles can be applied to the substrate dispersed in a solvent, for example as an ink (so-called nano ink), whereby a very uniform particle) is deposited. The advantage of such an application-20 method is that it can be implemented with ink jet type printing. Other application methods for nanoparticles include printing, roller application, spraying, painting and electrostatic transfer. Application does not constitute a necessary method step for the present process as nanomaterials and the like retain their sinterability for a long time after application. Thus, application and sintering are not temporally or locally interconnected.

One known method for depositing metal nanoparticles on a substrate surface is disclosed in WO 2005/025787. The particles are in a liquid dispersion which can be printed, for example, by the conventional inkjet method. During the spraying, 30 of the solvent evaporates, already increasing its viscosity.

Figure 1 shows one possible embodiment of the method according to the invention. In step 10, the substrate on which the conductor pattern is to be produced is taken. The substrate may be, for example, paper, cardboard, polymer film, three-dimensional plastic body, circuit 10, ceramic substrate, glass or other similar insulating material. In making permanent patterns, a substrate is selected which is capable of bonding the applied and sintered nanoparticle coating to its surface. The substrate may also be temporary, so that the sintered pattern does not adhere to it and can be transferred from the substrate to another substrate.

5

In step 11, the nanoparticles are applied to the substrate, for example, by dispersion as described above. When using solvents or pastes, the coating is preferably allowed to dry on the substrate surface so that its nanoparticulate concentration increases to a level suitable for sintering. By this is meant that the nanoparticles, when melted, are able to merge with one another and thus form uniformly conductive chains or regions.

In step 12, an electric field is generated through the coating by biasing the voltage across it. Voltage can be applied to the surface of the substrate, to the electrodes in the application area of the nanoparticles, or alternatively to the electrodes, which are subsequently introduced into the coating. Of course, it may also be possible for one of the electrodes to be finished on the surface, substantially in contact with the coating, and the other electrode to be subsequently applied to the surface (for example, for making contacts). The magnitude of the voltage depends on the distance between the electrodes and the desired sintering rate and resolution. Typical sintering voltages at 100 µιη electrode spacing are 1 to 10 V, preferably about 5 to 8 V. The electrode spacing typically ranges from 10 µιη to 5 mm, preferably 10 µιη to 1 mm.

In step 13, sintering is stopped. This can happen in different ways. First, sintering stops automatically if the entire coating layer is sintered. If conductive particles are used, the sintered layer will short circuit the electrode circuit. Secondly, the voltage can be cut off after a certain time after it has been switched on. Disconnection can also be based on feedback. After disconnecting the voltage, sintering stops and the layer temperature returns to normal. Third, the voltage supply circuit may be designed such that, when the coating is sintered over a sufficiently large area, sintering stops. This can be accomplished simply by, for example, a resistor connected in series with a constant voltage source. Then the power consumption of the sintered portion increases to a certain level as the coating resistance decreases and the feed power is no longer sufficient to effect further sintering.

11

In step 14, the non-sintered material may be removed from the substrate mechanically, chemically, or otherwise.

The process can be continued with steps 15 and 16. They apply a thin layer of dielectric over the sintered conductor pattern 5 (step 15) and then continue to manufacture the product by applying a second conductor or semiconductor layer (step 16). In this way, multilayer semiconductor component structures, circuit boards, or even whole functional electronic modules can be manufactured. Thus, the method described is particularly well suited for applications in printable electronics.

10

In particular, we have found an embodiment in which the voltage is applied across the nanoparticulate layer substantially in the direction of the surface of the substrate by means of electrodes placed laterally on opposite sides of the layer and in contact with the layer. The electrodes may be part of the conductors remaining in the structure 15 or removably applied to the substrate.

In the present process, no external heat source or compression is required in order to effect sintering, but a rise in temperature due to the voltage applied to the layer has been found to be sufficient due to the previously described internal positive feedback loop. Thus, in order to avoid a significant rise in the temperature of the substrate, a substrate having a substantially higher thermal capacity in the sintering region than the Sint-rotating region is preferably used. Thus, such a substrate should withstand only an external temperature, which may be, for example, -50 to 100 ° C, preferably about 10 to 40 ° C, typically normal room temperature.

25

The process can also be carried out step by step, for example, by using a sintered conductor structure in the previous process step as the electrode in the next process step. For example, sintering of large surfaces can be accomplished by using ready conductors to sinter the surface between them. For example, when producing dense wire patterns or wire grids, the pattern can always be densified by applying a new layer of nanoparticles and applying voltage to the previous, sintered layers. In the first step, the substrate has the initial electrodes (2 pieces), in the next step a first sintered conductor (1 piece) is produced between them, in the next step a new sintered wire (2 pieces) is made between each initial electrode and the first sintered wire. lines, etc.

Some practical applications of the invention will now be described.

Application Example 1. Sintering of metal surfaces and textured metal structures at low temperatures

As described above, the most natural way to utilize the method described is to sinter the metal at low temperature by applying either a galvanically or capacitively powerful electric field. If sintering is interrupted, we can make very thin metal patterns 15, for example on transistor structures and diodes in printed electronics. A smaller line width increases the speed of the transistor and diode. The thin structure, for example, on the screen makes it less visible.

One way to fabricate a thin gate transistor is shown in Figure 2. In step (a) 20, a nanoparticulate ink 20 is printed between (and partially on) the electrodes 22a and 22b on the substrate (a), so that a voltage is applied between the electrodes 22a and 22b. the central portion 24 of the ink-forming layer is sintered. In step (b), the Sint unbonded portion of the layer is removed, leaving an intermediate zone 26 between the electrodes and the sintered conductor 24. In step (e), gate 25 insulation 28 is printed on the sintering zone between electrodes 22a and 22b. a further printed semiconductor organic or inorganic layer 29 which comes into contact with the electrodes 22a and 22b but remains at a distance from the sintered conductor 24 due to the gate insulation 28.

Typical for the use of the present method in component fabrication is that at least 30 electrodes arranged on a substrate are utilized both in the component manufacturing process as a sintering electrode and as a contact terminal for the finished component. In particular, the process has the advantage that the components that most influence the speed of the component, and thus often represent the smallest line width, can be manufactured without mechanical processing. In particular, the above-described three-step (printing, partial sintering, non-sintering part removal) method 35 is applicable to the manufacture of subprocess electronics.

13

Application Example 2. Low temperature sintering

Experimental results show that semiconductors do not sinter at temperatures as low as metals. This is not generally explained, but we assume it is due to the poor conductivity of the surface and hence the weak Casimir phenomenon. Thus, conventional methods of sintering semiconductors at low temperatures require the use of very low particle size. This results in a very high number of crystal errors and, consequently, poor mobility of the booking carriers. The present process enables the particle size to be increased. Thus, electric sintering can provide better mobility. In addition, if the particles are oriented by, for example, a magnetic field before or during sintering, we can further reduce crystal errors and improve the mobility of the resulting semiconductor. Because the process requires the use of voltage electrodes, electronic sintering is particularly suited for pre-process semiconductor fabrication or where the semiconductor industry makes 15 sintering.

Application Example 3. Using Metallic Nanoparticles to Join Electronic Components 20 The electronics industry is moving to lead-free soldering. It is known that nanoparticles can be used for bonding by sintering nanomaterial to the contact terminal of the substrate metal and component by UV light or heating.

Figure 2 illustrates one method utilizing the present invention for making a metal contact even at room temperature. In the method, an electric field is applied to the dried nanoparticulate layer, in this case nano ink 30, which is located at the contact terminal of the conductor 32b and the component 35, to make contact 34. The conductor 32b also functions as the first voltage electrode. The electric field can be generated by using a second electrode 32a with which the nano ink is also contacted.

Alternatively, the contact terminal of component 35 may be used as a second electrode, if the desired potential can be supplied to it during the contact.

Figures 4a-4c show a side view of one of the contact modes. In Figure 4a, the conductors 44 and 46 are imprinted on the substrate 48. Nanoparticles are printed on the conductors as a layer 42. A layer 40 is placed on the layer 42 so that its contact terminals are aligned with the conductors 44 and 46. In Fig. 4b, voltages are applied between the contact terminals of component 40 and conductors 44 and 46 (or alternatively between conductors 44 and 46 and one electrode (s)), whereby their intermediate region 43 is sintered to form a 5 contact. In Figure 4c, the non-sintering layer is removed.

Application Example 4. Electronically writable memory

Memory is a key component of electronics. Printable electronics utilizes 10 precautionary structures for memory creation. However, their weaknesses are low embedding speed and poor memory stability. Electronic sintering enables a 0/1 type of memory comprising resistors which are almost open without sintering (for example, a resistor of 10 kOhm to 100 kOhm) and voltage elements for sintering the resistors that are to be short-circuited. We have found, for example, that dried nano-15 ink retains its electrical sinterability for a long time, so that memory can only be written after manufacture. In addition, the method allows the circuit memory to be reset after use by sintering all resistor elements.

More generally, the memory element to be written by electrical sintering comprises a matrix of multiple elements 20, each element having two voltage electrodes and a nanoparticulate zone, which when sintered is adapted to reduce, preferably short circuit, the resistance between the voltage electrodes. The voltage electrodes of each element of such a memory element are individually controllable to provide the described sintering.

25 Application Example 5. Use for Passivation of Spare Sensors or Remote Identification Circuits In LC resonance-type spare sensors, passivation is achieved by generating a strong electric field across the thin dielectric. This results, for example, in the passage of the aluminum particles through the plastic insulator, resulting in a short circuit. However, the problem has become that the short circuit thus made tends to recover. This has led to the inability to introduce a so-called "burglar" door. source taging applications because the products would cause too many fault alarms. The use of the present method eliminates the reactivation of backup sensors because the sintered metal structure is very stable.

Such backup sensors would thus have at least one layer of non-sintered or only partially sintered nanoparticle applied to the substrate, which when sintered is adapted to electrically connect the two wires contained in the backup sensor. The required sintering voltage or electric field can be applied to the layer galvanically, capacitively or inductively from the ul-5 side of the backup sensor. To achieve controlled sintering, separate sintering electrodes may be disposed near the nanoparticle layer. Alternatively, the sintering voltage may be arranged between the conductors naturally present in the device.

The EU is demanding that all RFID circuits drifting into consumer use must be able to be deactivated. UHF RFID circuits can also be used for theft protection. By using electric sintering, we can short circuit the RFID circuit after purchasing the antenna and make the circuit unreadable. If the antenna is suitably short-circuited, a situation can be provided in which the UHF-RFID reading range drops from several meters (e.g. 4-6 m) to a few centimeters (e.g. 0-10 cm). This way, after deactivation, the customer is not suspected of being stolen and no information is available to a third party about the products he / she is purchasing, but he / she can obtain the services related to the product by reading the remote sensor inside the product. The arrangement can also be made such that the UHF antenna is destroyed, but the antenna forms, for example, a 13.56 MHz antenna to which the consumer can connect to obtain information from the circuit using a suitable reader, for example a mobile phone. Nowadays, some RFID circuits contain the property of being unusable by programming, but unfortunately this prevents the consumer from utilizing the RFID circuits in their products.

More generally, the invention can be utilized to modify the operating frequency, sensitivity, or other characteristics of antennas, circuit boards, and other electronic devices (more generally, electronic modules). Such devices include at least one nanoparticle-containing zone, which when sintered is adapted to reduce (usually short-circuit) the impedance between the two conductor regions of the device. The sintering voltage may be applied to the zone, for example, as described above.

3 0 Modification of the properties of the electronic modules includes not only their deactivation and functional modification, but also their activation. Thus, the electrical circuit contained in the module may be completely unusable in its initial state, but may be converted into a functional circuit by electrical sintering.

16

Application Example 6. Roller sintering

The process is well suited for mass production. As an example of such an embodiment is mentioned an embodiment in which the sintering voltage is applied across the particle material layer by introducing the substrate 5 into an electric field in a web or sheet form. The electric field may be formed, for example, by a patterned electrode means, which preferably comprises a rotating roll, i.e. a roll, and includes means for locally applying voltage to the particle material layer. Thus, electrode zones and their counter-electrode zones are typically patterned on the surface of the electrode device. The sintering is then accomplished by a substantially electric field between the electrodes of the substrate surface orally.

The method thus permits the production of sintered patterns by simple weight-type equipment, for example, on a 'roll-over' or a 'roll-over' basis.

Figure 5 illustrates in more detail one embodiment of roll sintering. The web 54 is conveyed by roller means 51, 56. In the first step, particle material 52 is applied to the surface of the web. The web is then fed to an electrode roll 56 whose electrodes are connected to a sintering voltage. The conductive pattern determined by the electrode geometry is thus repeated on the web 54 to provide a conductive textured web 58. The substrate transport speed is selected such that the residence time of the particulate material in the electric field is long enough to achieve complete sintering.

Roller sintering can also be accomplished by means of a field perpendicular to the surface of the substrate, especially if the resistance of the substrate does not unduly restrict the sensory winding current formed in the particulate material. In this case, an electrode means mounted on one surface and a counter electrode means mounted on the other side are generally used. At least one of said electrode means comprises a conductor pattern for sintering the corresponding conductor pattern on the substrate. If the substrate itself is conductive, the substrate can be used as a counter electrode.

The electrode means or means may also be part of a nip between which the substrate is transportable. However, the electrode means do not need to exert significant pressure or temperature on the substrate, as in known sintering applications, but most preferably sintering is accomplished solely by the voltage between the electrodes and the tunneling current generated on the particle material. The method is thus also applicable to soft, porous and brittle substrates.

17

As the skilled artisan will understand from the foregoing, similar results may also be obtained by planar or planar or other types of electrode means.

5 Application example 7. Preparation of through-holes

The process according to the invention is also suitable for the manufacture of bushings in the circuit board and component industry. In particular, the lead-throughs for surface mounting circuit boards and single- and multi-layer circuit boards with embedded components are mentioned. Typically, the particle-10 coil material is arranged in a via hole (or recess) in a fluid form (fluidized), followed by a sintering voltage across the material, generally in the direction of the lead-through.

The application examples described above illustrate the broad industrial utility of the invention. One skilled in the art will appreciate that the method described can also be used in many other applications beyond these examples. Accordingly, the appended claims are to be construed in their entirety and in light of the equivalence interpretation.

Claims (34)

A sintering process wherein sintered or semiconducting lined nanoparticle particle material (20) is sintered to increase this electrical conductivity, characterized in that sintering is performed by applying a voltage across the particle material. Method according to Claim 1, characterized in that it utilizes positive thermal feedback to facilitate sintering between the particulate material (20) and the voltage supply. 10 Method according to claim 1 or 2, characterized in that the sintering is carried out by means of voltage electrodes (22a, 22b) disposed on opposite sides of the particulate material (20). A method according to any one of the preceding claims, characterized in that the voltage is generated by a voltage source having an impedance less than that of the conductive particle material (20, 42) at the time the voltage is applied. Method according to one of the preceding claims, characterized in that the voltage is switched by means of a constant voltage source. Method according to one of the preceding claims, characterized in that only the central part (24) of the particulate material (20) is sintered. Method according to Claim 6, characterized in that the voltage is cut off as the sintering proceeds to a predetermined level in the material (20). Method according to claim 6 or 7, characterized in that the voltage is applied over the resistor, the resistor being adjusted so that when the power supplied to the nanoparticulate layer (20) has increased to a certain level due to sintering, the sintering stops. Process according to one of the preceding claims, characterized in that the sintering is carried out at an external temperature of -50 to 100 ° C, typically at a temperature of 0 to 50 ° C, preferably at room temperature. Process according to one of the preceding claims, characterized in that sintering is carried out at normal pressure. Process according to one of the preceding claims, characterized in that metallic nanoparticles or semiconductor nanoparticles are used. 10 A process according to any one of the preceding claims, characterized in that nanoparticles lined with organic material are used. Method according to one of the preceding claims, characterized in that nanoparticles having an average diameter of 1 to 100 nm, preferably less than 50 nm, preferably less than 20 nm, are used. A method according to any one of the preceding claims, characterized in that, in order to effect sintering, it utilizes only the increase in temperature of the 20 nanoparticulate layer provided by said voltage. A method according to any one of the preceding claims, characterized in that substrate-conductive or semiconductor structures are produced, using a substrate having a surface at least partially provided with a layer of said particulate material (20). 25 Method according to claim 15, characterized in that the voltage is applied across the particle material layer (20) substantially laterally to the substrate surface, preferably to the substrate surface, by means of electrodes (22a, 22b) disposed on opposite sides of the layer. 30 Method according to Claim 15, characterized in that the voltage is applied at least partially over the layer of particle material (20) in the normal direction of the substrate surface. Method according to one of Claims 15 to 16, characterized in that the sintering is stopped before the entire particle material layer (20) is sintered and the non-sintered part of the particle material layer is removed from the surface of the substrate. Method according to one of Claims 15 to 18, characterized in that a particle material layer (20) is used which has a heat capacity substantially lower than the substrate heat capacity in the area corresponding to the particle material layer. Method according to one of Claims 15 to 19, characterized in that 10 layers of particulate material (20) comprising a dried layer of a liquid or paste dispersion such as metal nanoparticulate ink are used. Process according to one of Claims 15 to 20, characterized in that a substrate consisting of a material whose chemical or physical properties change permanently at temperatures above 100 ° C, preferably paper, cardboard or plastic, is used. Method according to one of Claims 15 to 21, characterized in that it comprises the step of applying a nanoparticulate coating on the surface of the substrate to form said layer of particulate material (20). Method according to one of Claims 15 to 21, characterized in that the sintering voltage is applied across the particle material layer (20) by substantially contacting the substrate with an electrode means comprising means for locally applying voltage to the particle material layer (20). 25 Method according to claim 23, characterized in that the electrode means comprises a rotating roll (56). Use of the method according to any one of claims 1 to 24 in the manufacture of printed electronic caps, semiconductor components or bushings, or in contacting electrical components. Use of a method according to any one of claims 1 to 24 for modifying the electrical properties, such as frequency response or sensitivity, of electronic modules comprising at least one nano-particle-containing band which when sintered is adapted to reduce the resistance between two conductor regions of the module. 27. An electronic product comprising a substrate and a conductor or semiconductor pattern (24) formed by sintering a nanoparticle on a substrate surface, characterized in that the conductor or semiconductor pattern (24) is sintered by a voltage applied to the lined wires or semiconductor particles. over the layer (20). The electronic product of claim 27, further comprising 10 voltage electrodes (22a, 22b) disposed on opposite sides of said pattern to sinter the pattern. An electronic product according to claim 27 or 28, characterized in that it comprises a layer of particulate material which cannot be sintered in the immediate environment by sintering a conductor or semiconductor pattern (24). An electronic product according to any one of claims 27 to 29, characterized in that it is a circuit board, a semiconductor component, a display matrix, a remote identifier, a backup sensor or a memory circuit. An electronic product according to any one of claims 27 to 30, characterized in that it is a printed electronic product. An electronic module comprising at least one electrical circuit having certain electrical properties and certain functionality in the initial state, characterized in that it comprises at least one nanoparticle-containing zone (20), to which a voltage can be applied for at least partial sintering of the zone. when sintered, is adapted to electrically connect at least two conductive regions within the circuit to alter the electrical characteristics or functionality of the circuit. The electronics module according to claim 32, characterized in that a voltage is applied between said conductor regions from the outside of the electronics module which causes said sintering. Electronic module according to claim 32 or 33, characterized in that it is a spare sensor, a remote identifier or a memory circuit.