FI20060697A - Procedure for manufacturing conductors and semiconductors - Google Patents

Description

Method for the manufacture of conductors and semiconductors

The invention relates to sintering and sintered rod products. In particular, the invention relates to forming 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 nanobonds melt microparticles at lower temperatures in the so-called. This is due to the fact that the number of "loose" atoms on the particle surface increases significantly as the total particle size decreases. This phenomenon is reasonably well known both theoretically and experimentally, although some aspects of the phenomenon have not yet been fully explained. it is exhaustively explained, for example, that when nanoparticles are lined with a thin layer of organic compound and applied to the substrate by means of solvents, it is found that the sintering temperature may be significantly lower than the melting temperature 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.

Smelting 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 even then 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 process 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.

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 the voltage (gap field) imaged over the lined nanoparticles initiates sintering of the nanoparticles even at low temperatures. Thus, in the process of the invention, the particulate material containing conductive or semiconducting lined nanoparticles is sintered to increase this electrical conductivity by applying a voltage across the parlikelin material.

The process is typically carried out using a substrate having a surface at least partially provided with a nano-carrier-containing layer containing conductive or semi-conductive lined nanoparticles. The nanoparticles in the layer are sintered by applying a voltage across the layer. The voltage generates a tunneling oscillation 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 a layer containing lined conductor or semiconductor nanoparticles. The sintered pattern is characterized in that it is of good quality and very homogeneous, since sintering proceeds rigidly from the center of the voltage electrodes to the electrodes, not randomly from here.

The electronic module according to the invention comprises at least one electrical circuit having certain electrical properties and a certain functionality in the initial state. The module further comprises at least one nanoparticulate zone to which a voltage can be applied to at least partially sinter the zone. Upon sintering, 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 chip circuit.

The invention arose when an experimental arrangement was made in order to understand the sintering of nanoparticles and to measure any predicted electrical nonlinearities, in which a slit formed of thin metal nanoparticles was placed in a gap formed between a thin two-metal electrode at room temperature. As expected, the non-sintered structure was found to be slightly conductive. With an aperture of about 100 µm and a voltage of about 5 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. The doubling of the electrode gap caused the sintering voltage to be doubled as well. Further investigation 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 pads and semiconductor particles having an average size of less than 100 nm and 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.

The nanoparticles are typically introduced 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 that is less than that of a conductive film by tunneling. The film is then sintered from the center towards the electrodes. If a resistor is still in series with the voltage source or the voltage control is terminated soon after sintering begins (for example, based on a timer or impedance measurement), the metal of the membrane! iparticles may be partially sintered. This allows the production of extremely thin line widths. The series resistor causes the voltage source to change to 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 particle material drops below 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.

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 heat resistance of the substrate. 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: 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, 7 nm silver particles have already been sintered at room temperature.

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.

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 in applications related to, for example, circuit board electronics, printed electronics, and co-component fabrication. Component contacting and metal penetrations can also 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 layer mass 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 (shrinkage, decomposition, bending, color change, 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. According to a preferred embodiment, the electrospinning is carried out at room temperature, which makes almost any substrate whose surface is only sufficiently smooth to receive a uniform layer of nanoparticles, 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 spare sensors, for example, at a retail counter, conversion of an RFID antenna from remote reading to close reading, high-resolution metal patterning in printed electronics applications, 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.

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

Fig. 1 is a flow chart of one embodiment of the present method, Fig. 2 is a side view of one possible process for fabricating a transistor using electric sintering, Fig. 3 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 is higher and / or of the same order as the so-called. the charge energy e11C, where e is the electron charge and C is the capacitance between the two particles. According to this, the conductivity of the kena 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.

The following deduction circuit illustrates one way to model voltage-induced sintering using a sintered layer containing nanoparticles lined with a polymer shell:

Since the electrical conductivity of the layer is poor at first, the thermal conductivity of the layer is also poor. (However, it must be noted that in order to trigger the phenomenon, both electrical and thermal conductivity must be substantially non-zero.) - As the voltage rises, the layer tends to warm up (poor thermal conductivity).

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 ability of the layer to draw power from the external voltage source increases (P = UZ IR), This accelerates the temperature rise in the middle of the layer (in the inter-electrode direction).

When the central portion reaches a critical temperature, their polymeric shell melts and the particles drift closer together.

- The tunnel flow between adjacent particles increases and at the same time the leakage conductivity is improved.

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

Also, the particles near the melted nanoparticles melt and the metallization 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 low specific heat and mass, so that a small amount of heat can easily raise 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, the process does not directly introduce heat into the system, as in the known sintering processes, but instead, the sintering is carried out by means of a jet, which results in positive teaming feedback and thereby 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.

If the stiffness system is controlled by current bias or high resistor instead of ice biasing, 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 so that only the middle part of the electrode will sinter and the other parts will not be metallized. This makes it possible to process conductors that are significantly smaller than the electrode spacing. 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 mn particles and a 50 µm electrode gap, it is possible to fabricate wires of less than 5 µm. As smaller particles, it is possible to fabricate conductors that are considerably smaller than this one. Also, a narrower electrode aperture allows for thinner conductors.

Both metallic nanoparticles and semiconductor nanoparticles 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.

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. Most typically, the coating has a thickness of about 1 to about 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.

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 polymeric shell (e.g., PEO, PPO) which prevents the particles from pelleting before being applied to the substrate. This is important, for example, in ink-jet printing, where adherent particles would clog the nozzles in the printer. In addition to application, a similar coating is also advantageous in the sintering process itself. The uncoated particles would partially adhere to one another prior to the "forced1" sintering, whereby the energy stored in the material would be significantly less than that of the clearly separated particles. Such material is brittle and very poorly conductive and cannot be similarly sintered , aal) has been discharged.

In summary, the method is thus based on the initial heating of the particle material by the power it draws from the voltage source and the increasing power consumption due to further warming, 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 introduced onto the substrate dispersed in a solvent, for example as an ink (so-called nano ink), whereby a very uniform particle distribution is smoked. The advantage of such an application method is that it can be implemented with inkjet-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 conventional ink jet printing. During spraying, the solvent evaporates from the dispersion, thereby 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, printed circuit board, 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.

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. This means 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 applying a 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 in the vicinity of 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 brought to the surface afterwards (e.g., making contacts). The magnitude of the voltage depends on the distance between the electrodes and the desired sintering rate and resolution. Typical sintering voltages within a 100 µm electrode gap are 1 to 10 V, preferably about 5 to 8 V. The electrode gap typically ranges from 10 µm to 5 mm, preferably 10 µm to 1 mm.

In step 13, sintering is stopped. This cannot happen in any way. 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. Second, the voltage can be switched 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 achieved simply by, for example, a constant-voltage resistor connected to a constant voltage source. Then the power consumption of the sintered part increases to a certain level as the coating resistance decreases and the feed power is no longer sufficient to effect further sintering.

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 a sintered conductor pattern (step 15) and then continue to manufacture the product by applying another conductor or semiconductor element (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.

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 or removably applied to the substrate.

In the present process, no external heat source or compression is required 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 of the structure. Thus, in order to avoid a significant increase 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, for example from -50 ° C to 100 ° C, preferably from about 10 ° C to 40 ° C, typically normal room temperature.

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-made conductors to sinter the surface therebetween. For example, in the manufacture of dense conductor patterns or conductor lattices, the pattern can always be densified by applying a new layer of nanoparticles and applying voltage to previous, sintered layers. In the first step, the substrate has 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 conductor.

Some practical applications of the invention will now be described.

Application Example 1, Low Temperature Sintering of Metallic Surfaces and Textured Metal Structures

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 on eg 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 1. In step (a) 1, nanoparticulate ink 20 is printed between (and partially over) 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 non-sintered portion of the layer is removed, leaving an intermediate zone between the electrodes and the sintered conductor 26. In step (c), a gate insulation 28 is printed on the sintering zone between the electrodes 22a and 22b. a printed semiconductor organic or inorganic layer 29 which comes into contact with the electrodes 22a and 22b but, thanks to the gate insulation 28, remains at a distance from the sintered conductor 24.

Typical for the use of the present method in component manufacturing is that at least one electrode tracked on the substrate is 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 parts which have the greatest influence on the speed of the component and thus often have the smallest line width can be manufactured without mechanical processing. In particular, the three-step process described above (printing, partial sintering, removal of the non-sintered part) is suitable as a subprocess for the production of printed electronics.

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 mobility can provide better mobility. In addition, if the particles are aligned with, 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 to pre-process semiconductor fabrication or where the semiconductor industry is performing sintering.

Application Example 3. Use of metallic nanoparticles in the connection of electronic components

The electronics industry is moving to lead-free soldering. It is known that nanoparticles can be used for bonding by sintering the nano ink to the contact terminal of the substrate metal and the component by UV light or by heating

Figure 2 shows 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 disposed between the conductor 32b and the contact terminal of 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 Fig. 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 the component 40 and the conductors 44 and 46 (or alternatively between the conductors 44 and 46 and the second electrode (s)), whereby their intermediate region 43 is sintered to form a 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 utilize precautionary structures to make memory. However, their weaknesses are low picking speed and poor memory stability. Electronic sintering enables a 0/1 type of memory comprising resistor elements that are almost open without sintering (for example, a resistor of 10 kOhm to 100 kOhm) and voltage elements to sinter the resistor elements that are to be short-circuited. We have found, for example, that dried nano ink retains its electrical sinterability for a long time, so that memory can only be written after manufacture. In addition, the method allows to reset the circuit memory after use by sintering all the resistor elements

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

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, for example, results in the passage of the aluminum particles through the plastic insulator, resulting in a short circuit. However, the problem has been that the short circuit thus made tends to recover. This has led to the inability to introduce a so-called "burglar" door. source taging in application support 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 two conductors contained in the backup sensor. The required sintering voltage or electric field can be applied to the layer galvanically, capacitively, or inductively from outside the backup sensor. To achieve controlled sintering, separate sintering electrodes may be disposed near the nanoparticle layer. Alternatively, the sintering voltage can be traced between the conductors naturally present in the device.

The EU is demanding that all RFID circuits that end up in the consumer's hands must be able to. deactivated. UHF RFID circuits can also be used for theft protection. By using electronic sintering, we can short circuit the RFID circuit after purchasing the antenna and make the circuit unreadable. If the antenna is suitably short-circuited, the situation can be followed when 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 being able to deactivate, the customer is not suspected of being stolen and the outsourced product is not accessible to an outsider, but can receive services related to the product by reading the remote sensor on the product at close range. The ice cell can also be made such that the UHF antenna is destroyed, but the antenna forms, for example, a 13.56 MHz antenna which the consumer can connect to obtain information from the circuit using a suitable reader, for example a mobile phone. is rendered 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.

Changing the properties of 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.

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 a layer of particulate material by applying a substrate to 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 a voltage to the particle material layer. Thus, electrode zones and their counter-electrode zones are typically patterned on the surface of the electrode device. Sintering is then effected by an electric field substantially parallel to the surface of the substrate between said electrodes.

The method thus permits the production of sintered patterns by simple weight-type equipment, for example, roll-to-roll or roll-to-roll.

Figure 5 illustrates in more detail one embodiment of roll sintering. The web 54 is conveyed by roller equipment 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 velocity is chosen 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 sensing current formed in the particulate material. In this case, an electrode spacer fitted 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.

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.

Application Example 7. Preparation of lead-throughs

The method 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 particulate material is tracked into the lead-through (or recess) in a fluid form (fluid-like), after which a sintering voltage is applied across the material, generally in the direction of the lead-through.

The application examples described above illustrate the broad industrial utility of the invention. It will be appreciated by those skilled in the art that the method described may 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 a positive thermal dielectric coupling between the particle bond material (20) and sintering feed. 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). Method according to one of the preceding claims, characterized in that the reinforcement is generated by a voltage source having an impedance less than the resistance of the tunneling conductive particle material (20,42) at the time of applying the voltage. Method according to one of the preceding claims, characterized in that the voltage is applied 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 when the sintering has reached 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. Process according to any one of the preceding claims, characterized in that nanoparticles lined with organic material are used, A method according to any one of the preceding claims, characterized in that nanoparticles with an average diameter of 1 to 100 nm, preferably less than 50 nm, preferably less than 20 nm, are used. Method according to one of the preceding claims, characterized in that, in order to effect sintering, it utilizes only the increase in temperature of the 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). 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 electrodes (22a, 22b) placed laterally on the opposite sides of the layer. 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 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. A method according to any one of claims 15 to 19, characterized in that a layer of particulate material (20) comprising a dried layer of a liquid or paste dispersion, such as a melamine nanoparticulate ink, is used. Process according to one of Claims 15 to 20, characterized in that a substrate is used consisting of a material whose chemical or physical properties change permanently at temperatures above 100 ° C, preferably paper, cardboard or plastic. 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). A method according to any 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). 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 circuit boards, semiconductor components or bushings or in contacting of electronic components. Use of a method according to any one of claims 1 to 24 for changing 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. An electronic product comprising a substrate and a surface of a substrate and a wire or semiconductor pattern (24) formed by sintering nanoparticles, characterized in that the wire or semiconductor pattern (24) is sintered by means of a voltage applied to a lined wires or semiconductor (20) over. The electronic product of claim 27, further comprising voltage electrodes (22a, 22b) disposed on opposite sides of said pattern for sintering 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 in the initial state and a certain functionality, characterized in that it comprises at least one nanoparticle-containing zone (20) for supplying voltage for at least partial sintering of the zone; electrically 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.