APPARATUS FOR AUTOMATIC MATERIAL DEPOSITION BY MEANS OF AN

AIRBRUSH

TECHNICAL FIELD

The present invention relates to an apparatus for automatic deposition of materials by means of an airbrush.

More particularly, the present invention relates to chemical sensors fabrication, to which the following description will be referred to, without loss of generality.

BACKGROUND ART

Generally, in sensor fabrication the chemical material is deposited on the transducer surface by means of the "spray casting" technique, in which the chemical material is dissolved into a proper solvent and sprayed through a nozzle using a sodium flux as carrier. The airbrush and the transducer are fixed to a small supporting structure, placed under an pumping means. More particularly, the airbrush is faced toward the transducer surface, and it is manually controlled by the user, who can take control over both the sodium-solution mixture composition and the airbrush flow shut off.

Obviously, with the above mentioned technique it turns out to be very difficult, if not impossible, succeed in reproducing the deposition features; in the case of chemical sensors this means that it is impossible to have sensors able to give the same answer.

DISCLOSURE OF INVENTION

The aim of the present invention is that of realizing a device able to assure the reproducibility in airbrush deposition.

Object of the present invention is an apparatus for automatic deposition characterized by comprising a deposition chamber; an airbrush, part of which is lodged inside the deposition chamber; a supporting structure for a substrate lodged inside the deposition chamber; a quartz resonator lodged inside the deposition chamber and placed inside the airbrush spraying zone; reading devices able to read the quartz resonator frequency; and a master control unit connected both to the reading devices and to the airbrush, and able to receive settings about the amount of material to be deposited on the substrate; the master control unit being able to do progressively: receive the frequency values of the quartz resonator from the reading devices, compare these values with a sequence of values related to the resonator frequency corresponding to a specific amount of material deposited on the substrate, and control the airbrush as consequence of the comparison performed and the amount of substance chosen to be deposited on the substrate.

According to a preferred embodiment, the apparatus of the present invention includes heat treatment devices lodged inside the deposition chamber and connected to the master control unit.

According to a further preferred embodiment, the apparatus object of the present invention includes positioning devices able to rotate the supporting structure in order to allow the deposition on both the faces of the substrate.

BRIEF DESCRIPTION OF THE DRAWING

The following non-limiting example is purely indicative in order for a better understanding of the invention with the help of the figure in the accompanying drawing, in which the apparatus of the present invention is schematically shown.

BEST MODE FOR CARRYING OUT THE INVENTION

In figure the overall apparatus of the present invention is labelled as 1. The apparatus 1 comprises a deposition chamber 2, in which a supporting structure 3 for a substrate 4 and provided with a revolving base 5, a quartz resonator 6 and an heating lamp 7 are lodged.

The apparatus 1 includes also an airbrush 8, whose spraying nozzle 9 is placed inside the deposition chamber 2 too, a first electromechanical device 10 connected to the supporting structure 3, a second electromechanical device 11 connected to the airbrush, and a device 12 connected to the resonator 6 and able to read the frequency value by means of an oscillating circuit schematically labelled as 13. More particularly, the second electromechanical device 11 is able to interrupt the airbrush flow and operate on a sodium-solution mixture, acting on an electrically controlled valve, which is not described and shown in figure for sake of simplicity.

The apparatus 1 comprises a master control unit 14 connected to the heating lamp 7, to the reading device 12 and to a electromechanical control unit 15, which take control over the first 10 and second 11 electromechanical devices.

In the master control unit 14 is implemented a specific algorithm which, on the basis of physical parameters entered, provides for a sequence of values relating quartz resonator frequency 6 with the amount of material deposited on the substrate 4. These physical parameters could be, for example, the placement of the resonator 6 and of the substrate 4 in respect to the airbrush 8.

In this way, the master control unit 14 knows the resonator frequency corresponding to the substance deposited on the substrate.

The apparatus 1 includes also a switch 16, able to apply the oscillating circuit 13 directly to the substrate 4 instead to the resonator 6. This kind of displacement is possible when the substrate 4 is made up of quartz too, and it requires an adequate change in the parameters set in the algorithm,

thus providing a different sequence of the values available to the master control unit 14. The switch 16 can be also directly connected to the master control unit 14 and controlled by software.

As above mentioned, the master control unit 14 is connected to the heating lamp 7, in order to control a thermal treatment during and/or after the deposition. Moreover, the master control unit 14, through its connection to the electromechanical control unit 15, drives the first electromechanical device 10 in order to rotate the supporting structure 3, thus allowing the deposition on both faces of the substrate 4. Obviously, the master control unit 14 will take into account the rotation, shifting the "zero-threshold" to control the amount of mass deposited on the new face of the substrate.

As showed in figure, the master control unit 14 can be interfaced with a user by means of the keyboard-display 17, or by means of a PC 18 equipped with a specific software.

Finally, the apparatus 1 comprises pumping means 19, which are also connected to the master control unit 14 and guarantee a high level of cleanliness inside the deposition chamber 2.

In use, the physical parameters related to the resonator 6 and substrate 4 are provided to the algorithm, in such a manner to obtain a sequence of values that link the frequencies of the resonator 6 to the amount of substance deposited on the substrate 4. These series of values set up the basis on which the deposition goes on set by the master control unit 14. Moreover, working parameters relating to the satisfactory resonator tolerance and to the stability (both are expressed in Hz) will be entered in the master control unit 14. The reading device 12 has to own such parameters in order to take into account the frequency read. The setting relative to the stability comes from the evaporation of the solvent that is deposited together the substance of interest.

Once the master control unit 14 has the mentioned sequence of values available, the user can insert the following deposition settings into the master control unit 14: the amount of substance to be deposited on the substrate; if the deposition has to be performed on one or both the faces; and the thermal treatment, that is the temperature profile set during and after the deposition.

During the deposition process, the master control unit 14 receives continually the values coming from the reading device 12, and whenever it checks that the resonator frequency, according to the value sequence obtained from the algorithm, matches the amount of substance set to be deposited, then call for the airbrush 8 to be shut off through the mechanical control unit 15 by means of the second electromechanical device 11.

Moreover, the master control unit 14 controls the heating lamp 7 as set from the user, and it requires periodically the switching on of the pumping means 19 particularly among different depositions.

The data inserted by the user by means of the keyboard-display are stored in a memory in such a way that they will not be lost when the apparatus is turned off, thus being possible to use them again. In particular the thermal treatment can allow the achievement of a specific morphology of the material deposited; the relative settings can be recorded in the master control unit 14 to be later recalled to reproduce a certain morphology.

Whenever the software is used as an interface, it can also be used to manage all the data relating to the deposition parameters. This software, apart from managing the communications to the master control unit 14, can also allow to visualize the deposition progression on the PC display. Moreover, this software allow to save both the deposition setting parameters to be later recalled, and the temporal deposition trace to be compared with others from earlier depositions, stored in memory.

It can be clearly understood from the above description that the apparatus of the present invention allows to realize an automatic and repeatable material deposition through spray casting technique. It will thus be possible to produce different chemical sensors having all the same features.

The above mentioned advantages are made possible by the simultaneous use of both a quartz resonator and a master control unit, which take into account a sequence of values relating to the correspondence between the resonator frequency and the amount of material deposited on the substrate.