COMPOSITE INKJET PRINT HEAD AND ITS MANUFACTURING PROCEDURE.

Description

International Class B41J 3 / 04 Description of the Industrial Invention entitled: “Composite inkjet print head and related manufacturing process” in the name of Olivetti I-Jet S. p. A. of Italian nationality, with registered office in Via Jervis 77, 10015 IVREA (TO) Inventors: Conta Renato, Manini Enrico. 2 0 FEB.2002' ****** ***TO 2002 A 00 0 14*4 The present invention relates to a composite inkjet printhead and to the process for manufacturing the same, particularly for a top-shooter type inkjet printhead, i.e. the type in which the ink drops are ejected perpendicular to the substrate containing the heating elements and the ejection chambers. BRIEF DESCRIPTION OF THE STATE OF THE ART As is known in the art, for example from Italian patent No. 1234800, and from US patent No. 5387314, the print heads of the above-mentioned type are made using as a support a thin crystalline silicon disk with a thickness of approximately 0.6 mm and a diameter of approximately 150 mm (wafer), from which the individual heads will be separated at the end of their production; a plurality of superimposed layers is deposited on the silicon disk using vacuum processes, in which the active NMOS devices, made with integrated circuit technology, the heating elements, or resistors, and the related electrical connections are obtained for each head. outward, protected and separated by corresponding insulating layers; the resistors are contained within chambers obtained within the thickness of an additional overlapping layer of photosensitive material, for example VACREL™, and obtained using a photolithographic process together with the lateral ink supply channels; the chamber channels communicate with a narrow, oblong, slot-shaped ink supply duct, which passes through the silicon support and the already deposited layers and is arranged between two parallel rows of chambers, arranged on both long sides of the slots. Before being separated, a metal or plastic sheet carrying the ejection nozzles is applied to each of the heads still arranged on the wafer, fixed by glue above the layer of chambers, and positioned precisely to make each nozzle coincide with a corresponding chamber. The completed wafer is cut according to a rectangular mesh grid to separate the individual heads, each of which is completed with the connection to a multi-wire flat cable (fiat cable), the ends of which are soldered onto corresponding pads obtained along one edge of each individual head and connected via internal connections to the resistors. According to the current technique, the processing of the slots is carried out after having created the active semiconductor devices, and deposited the resistor layers, the layers of the relative electrical connections and the overlying protection layers on the silicon support; Two-stage processing begins on the surface opposite the resistor-bearing surface with a sandblasting process, or partial chemical etching of the silicon substrate, and is completed with sandblasting or laser erosion. Alternatively, the slots can be machined with a single, full-surface sandblasting operation. The machining of the slots done in the ways mentioned above often causes geometric irregularities, or misalignment of the edge of the slots with respect to the resistors, or even damage to the layers that are crossed, due to chipping on the edge of the slot facing the chambers, resulting in a high level of production waste, especially for long (> 1 / 2”) and narrow (<250 pm) slots, in addition to being a long, complex and expensive process. SUMMARY DESCRIPTION OF THE INVENTION The main aim of the present invention is to produce print heads free from the above-mentioned drawbacks and in particular to produce print heads in a time and at a reduced cost compared to the known art, and in which the processing of the ink supply ducts (slots) does not interfere with the integrity of the layers in the area of ​​the resistors and the ejection chambers and supply channels to the chambers. A further object of the present invention is to provide inkjet print heads in which the surface area of ​​the silicon support is reduced to a minimum. used by each printhead. Another aim of the invention is to define an innovative process for the construction of inkjet printheads, in which the processing of the ink supply ducts does not interfere with the integrity of the resistors and their protective layers and in which each head is made using a very small silicon support, to increase the production yield of the printheads and to allow the creation of multiple colour heads, i.e. with several independent groups of nozzles, capable of ejecting very small drops (<5 µl), particularly suitable for printing images with photographic resolution. In accordance with the predefined purposes, according to the present invention, a composite inkjet printhead and an innovative process for manufacturing said head are presented, characterized in the manner defined in the corresponding main claims. This and other features of the invention will appear more clearly from the following description of a preferred embodiment of the print head and of the manufacturing process thereof, given by way of example but not of limitation, with reference to the figures of the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 represents an exploded perspective view of a composite inkjet printhead, constructed according to the present invention; Figure 2 represents a partially sectioned plan view of the print head of Fig. 1; figure 3 is the section along line III-III of fig.2; Figure 4 represents the arrangement of the support elements, or bases, on a support plate, before cutting and separating them; Figures 5 and 6 show the arrangement of the contact pads on two different types of active modules; Figures 7 and 8 represent two different techniques for soldering the “fiat cable” to the pads of an active module; Figures 9 to 13 represent different geometries of composite inkjet print heads, according to the invention; Figure 14 represents the electrical diagram of an addressing circuit, integrated in an active module, according to the invention; Figure 15 schematically represents the arrangement on an active module of the circuit of Fig. 14. DETAILED DESCRIPTION OF THE INVENTION The fundamental solution idea, according to the present invention, is to construct an inkjet print head 1 (fig. 1), composed substantially of two parts machined separately and assembled together only at the end of the respective processes; more specifically, the new composite print head is made up of a first support element, or base 3, of a rigid, insulating material; a slot-shaped opening 5 is made on the base 3, passing through the thickness of the base itself; this opening constitutes the ink supply duct, as will be described in detail later. A second element, called active module 7, is made up of a crystalline silicon wafer 8, on which, using the processes known in the art and separately from the base 3, the active NMOS devices are made, constituting the driving and selection circuits 12, the layers relating to the heating elements, or resistors 10 and the related interconnections are then deposited, and a photosensitive resin film 15, in which the ink ejection chambers 14 are obtained, aligned with the corresponding resistors 10. At this point, each active module 7 is fixed to a corresponding base 3, already prepared, by gluing and pressing; subsequently, a resin frame 16 having the same thickness as the module 7 and surrounding the module itself is glued to the base 3, to improve the hydraulic seal. Finally, each active module 7 is completed with the application above the photosensitive film 15 and partially above the frame 16 of a metal or plastic sheet 17, carrying the ejection nozzles 18, precisely arranged in correspondence with the chambers 14 and facing the respective resistors 10, in such a way that the ink drops are ejected in a direction perpendicular to the extension plane of the resistors 10 (top shooter). A more detailed description of the structure and manufacturing process of a preferred, non-limiting embodiment of a composite print head according to the invention, and in particular of a head with a single row of nozzles, will follow. It is understood that the solution idea of ​​the present invention also applies to so-called multiple heads with more than one active module and with different geometries. Preparing the base 3 The head 1, as already mentioned with reference to fig. 1, comprises a support element, or base 3, of substantially rectangular shape, with a thickness between 400 and 600 µm and delimited by two opposite surfaces 20 and 21, flat and parallel; the base 3 is cut from a plate 22 (fig. 4) of rigid, electrically insulating, chemically inert material, with a thermal expansion coefficient close to that of crystalline silicon; by way of example, but not limited to, the materials that can be used to obtain the base 3 include alumina, borosilicate glass, resin, or even crystalline silicon, not necessarily of high purity and surface finish. For example, it is chosen to use for the creation of the bases 3 a plate 22 (fig.4) of normal silicon, of the commercial type, for example of the “rescarted” type, without particular electrical and mechanical characteristics, with a diameter of approximately 150 mm and a thickness of approximately 400 - 600 µm, from which it will be possible to After processing, obtain approximately 500 unit bases, assuming that each base has dimensions of approximately 5 X 14 mm. The preparation of the bases 3 proceeds according to the following steps, (fig. 4): step 1) on one face 20 of the plate 22 a metal film 24, for example Al or Cr, with a thickness of 1000 -3000 A° is deposited, on which a layer of photosensitive material, Fotoresist 26, is spread, in turn impressed with a mask to define the following positioning references: la) reference and alignment marks 29, to position the active module 7 on its base 3 with high precision, i.e. with a tolerance of + / - 1 pm; lb) outline 30 of buttonhole 5; the) separation lines 32, along which the individual support bases 3 will subsequently be cut; ld) outlines of adhesive dispensing areas 33, for gluing the active module 7 onto the base 3; le) outline of the dispensing area 34 of the adhesive for gluing the resin frame 16, which laterally seals the module 7 on its base 3. step 2) exposure of the photoresist 26 to a light source through a mask and subsequent development; removal of the superfluous portions of the metal film 24, not protected by the mask used; step 3) application of a film of the “adesion promotion” type to facilitate the adhesion of glues; Step 4) Etching of slot 5, without any particular precision restrictions, since base 3 lacks delicate components, such as resistors or NMOS circuits; etching can be performed using one of the methods known in the art, such as sandblasting, laser beam, vacuum plasma, anisotropic chemical etching, etc. If alumina or ceramic is used, the slot is obtained by molding before firing. With the creation of the 5 buttonholes, the preparation of the 3 bases is completed, which are temporarily stored in a temporary warehouse. Preparing active modules 7, To produce the active modules 7, a crystalline silicon wafer, not shown in the drawings, with a thickness of between 400 and 600 μm is used; initially, both external, opposite surfaces are passivated with an insulating layer of silicon oxide, SiO2; assuming that each active module 7 has plan dimensions of 10.5 mm x 1.6 mm, approximately 700 modules can be produced on the silicon wafer, excluding the inevitable production waste. Then on one of the passivated surfaces, for each active module 7, the NMOS circuits for driving the resistors 10, the logic selection circuits are made using known semiconductor technologies, and with a deposition of conductive, insulating and resistive layers, the resistors 10, the protective layers, the Giampterójfobb g? internal interconnections and external pads; finally, a layer of photosensitive polymer is laminated, in which, after exposure and development, the ink ejection chambers are obtained, following the construction processes known in the art, for example as described in detail in the aforementioned Italian patent No. 1,234,800, or in the Italian Patent Application No. TO 2001 A001019 in the name of the applicant, which are hereby incorporated by reference. By following the preparation process described, according to the invention, at least two types of active modules can be produced, by way of non-limiting example: a first type called “Module A” (fig.5), in which the driving circuit 12, integrated in the module, is organised as an NMOS matrix, which requires a high number of external connections, or pads 37, arranged on the long side 38 opposite the resistors 10; a second type called “Module B” (fig.6), in which in addition to the driving circuit 12, the selection logic 40, in CMOS or NMOS, is also integrated on board, with a further reduction in the number of external connection pads 42, which can be arranged on the short sides 43 of the module 7. Once the construction of all the active modules contained in the silicon disk has been completed, after the normal visual checks and electrical tests, the individual modules are separated by cutting the disk according to a rectangular grid with dimensions conforming to the dimensions of the individual modules. Composite printhead manufacturing The composition of the print head according to the invention is achieved by fixing each of the active modules 7 on each of the bases 3 still joined on the plate 22, and is carried out according to the following steps: step 5) dispensing of a polymerizable adhesive into the areas 33 where the active modules 7 will be fixed on the plate 22; step 6) positioning and alignment of the active modules with a precision of + / - 1 pm on the bases 3 of the plate 22, making reference between the marks 29 of the base 3 and the corresponding marks 29' obtained on each module 7; step 7) application of UV-curing glue dots on the 3 bases to keep the individual active modules blocked during the subsequent polymerization phase of the polymerizable adhesive; step 8) polymerization of the polymerizable adhesive after completing the positioning and alignment of the individual active modules in their respective positions on the plate 22; step 9) dispensing adhesive into the gluing areas 34 of the frames 16; step 10) assembly of the resin frames 16 on the bases 3, according to the references of the separation lines 32 of the plate 22; the frames 16 are made up of a resin plate of substantially rectangular shape (fig. 1), presenting a central opening 16a, also of rectangular shape, complementary to the dimensions of the active module 7 and such as to surround the active module 7, in contact with at least three contiguous sides “a”, “b”, “c” of the active module 7 (figs. 2, 3); the frame 16 is kept at a distance from the fourth side “d” of the active module 7, or the fourth side “e” of the opening 16a is positioned beyond the slot 5 with respect to the fourth side *d* of the active module 7, equipped with the chambers 14, so as to form an ink reserve chamber 5a, communicating both with the feed slot 5 and with the chambers 14; the chambers 16 must have a thickness equal to that of the active modules 7 to form, together with the active module 7, a uniform surface, to facilitate the subsequent gluing of the nozzle holder plate 17 (fig. 1); step 11) polymerization of the adhesive to lock the comics on the plate 22; step 12) spreading of an adhesive on the upper surface of the frames 16, for the subsequent fixing of the ink ejection nozzle holder plates 17; the nozzle holder plates 17 adhere to the photopolymer layer 15 by thermal effect; alternatively, a film of thermoplastic or thermosetting material can be spread on the frame, deposited by pad printing, rolling, screen printing, or more simply a layer of semi-liquid glue, dispensed flat in a groove, not shown, prepared on the frames; step 13) assembly of the nozzle holder plate 17 and its temporary alignment with respect to the resistors 10 and locking of the same with some glue points 19, 86 (figs. 1,13), before separating the portion of nozzle-holding sheet, relating to each single module, from the carrying coil, not shown in the drawings, in the case of plastic sheets, or from the pre-scored sheet, in the case of metal sheets; step 14) pressing at controlled temperature and duration of all the plates 17 of all the active modules 7 mounted on the plate 22, for gluing the plates themselves to the photosensitive polymer layer 15 of the individual active modules 7 and to the frames 16; at the end of this operation the nozzle-holder plates 17 form an upper closing wall of both the chambers 14 and the chambers 5a, communicating with the slots 5. step 15) cut the plate 22 along the separation lines 32 to obtain the individual composite print heads. A “fiat cable” 45 is connected to the composite heads thus created, by welding its ends to the pads 37,42, obtained on the edges of each active module 7; the welding can be carried out with the standard process, known in the art, called “Tape Automatic Bending”, TAB (fig. 7), or with thermoplastic adhesives of the ACF (Anisotropie Conductive Film) or ACP (Anisotropie Conductive Paste) type (fig. 8), consisting of a thermoplastic film 44, or respectively a paste resin to be dispensed, including small electrically conductive spheres, dispersed in the polymer; the conductive spheres are based on a Tin-Bismuth alloy, with a melting point of approximately 140 °C, they make an excellent electrical contact between the “flat cable” 45 and the pads 37,42 of the modules 7, such as the commercial product Loctite ACP 3445 ™. With the ACF, or ACP, technique, the advantage is obtained that the contact conductors 46 of the “flat cable” 45 (fig. 8) are supported by the “flat cable” itself, with the advantage that the leading edge 47 of the “flat cable” can be positioned very close to the edge 48 of the nozzle-holder plate 17 and the thickness of the “flat cable” can be chosen so that the upper surface 49 of the “fiat cable” is at the same level as that 49' of the nozzle-holder plate 17; on the contrary, with the TAB welding type (fig. 7), the welding ends 50 of the “fiat cable” are arranged in a cantilevered manner creating a cavity 52 which must be filled with a protective UV resin 53. The ACF or ACP type connection is feasible with high-definition printheads; in fact, the ejected ink droplets can be reduced to a volume of about 4 - 6 µm, with energies of 1 - 2 yJ, so the electrical currents crossing the pads are on the order of 100 mA, or less. The reduced current consumption allows to reduce the area occupied by the NMOS driving circuits (figs. 5,6), with the consequent possibility of reducing the width “W” of the active module 7; this also allows to increase within a wide range the number of nozzles aligned on a single row, increasing the height “H” of the active module 7. With a step of 1 / 300" between the resistors, i.e. between the nozzles, you it can build a module with a height “H” of up to 1", without encountering the problems of making the ink supply slots 5, as they are made separately on the support plate 22. The printhead preparation process described above can be used, without any particular modifications, to prepare multiple printheads, in which at least two or more active modules 7 are fixed on the same base, arranged in different configurations, according to the required printing performance. Figures 9 to 12 show, by way of example and without limitation, some possible configurations of multiple print heads, composed of a single base 55, on which a plurality of active modules 7, of the “A” type, are fixed, in which the electrical connection pads are arranged on one long side of each module 7, opposite to the other long side, on which the chambers 14 are arranged; more specifically, figure 9 represents a print head in which, on a single base 55, three active modules 7, of the “A” type, are fixed, for a colour printer; the modules 7 are placed side by side in parallel, in a horizontal direction, i.e. parallel to the writing direction, indicated by the arrow “F”, and with nozzle pitch such as to obtain a printing resolution of 300 or 600 DPI.; 60 indicates the external edge of the support base 55, 61 indicates that of the overlapping frame 16, 62 indicates the three nozzle-holder plates, 63 indicates the three slots for feeding inks of different colours; 63a indicates the ink chambers, . similar to those indicated with 5a in figure 3, delimited by the plate 62, by the sides “e” of the opening 16° and by the side “d” of the active modules 7; with 64 are indicated the nozzles aligned in proximity to the long side “d” of each module 7, facing the corresponding slot 63, and with 65 the external connection pads to which the “fiat cable” 66 is connected; in this version, the “fiat cable” 66 is provided with three openings 67 of such a size as not to cover the nozzle-holding plates 62; the contact ends 68 of the “fiat cable” 66 are arranged on an internal long side of each opening 67. Figure 10 shows a print head with four active modules 7, two by two, fixed on a single base 55, to be able to print with three colors plus black; on the base 55, machined separately from the active modules 7, the four supply slots 71 are obtained, each suitable for supplying a different colored ink; then on the base 70 the four active modules 7 are fixed, arranged adjacent and parallel to each slot 71. In the version shown in fig.10, two nozzle-holder plates 72, 73 are used, each of which carries two parallel rows of nozzles 18 and covers two adjacent modules. The “fiat cable” 45 is provided with a single rectangular opening 75, and the connection pads 76 are located on the two long sides of the opening 75. Figure 11 shows a single-colour head made up of a single base 55 on which two identical modules 7 are fixed and aligned in head-to-head contact, with a nozzle pitch of 1 / 300”; this arrangement allows the nozzle pitch to be kept constant, even across the two modules; in this way, by using two 1 / 2” high modules (H), an “equivalent” 1” high module is obtained, with which it is possible to print with a resolution of 300 DPI with a single pass, or with 600 DPI with two passes. On the base 55 there is a single ink feed slot 77, longer than other similar ones, as it has to feed two consecutive rows of nozzles 18. Likewise the nozzle holder plate 78 is made in a single piece and covers both modules 7. Finally, figure 12 shows a print head composed of a single base 55, with three modules 7 aligned vertically, but spaced apart from each other; this head can be used to print with three colors at a pitch of 1 / 300”, or 1 / 600”. Also in figures 11, 12 the 'fiat cable' 45 has only one opening 75 and the connection pads 76 are located on one of the long sides of the opening 75. Figure 13 shows an exploded perspective view of a multiple, three-color print head, with three “B” type modules 7, arranged on a single base 55, parallel and side by side in the direction of the writing feed, indicated by the arrow “F”; the base 55 is provided with three slots 80, in proximity of which the three active modules 7 are fixed. pi ro Bobb n A 81 resin frame with a thickness equal to that of the modules 7, is glued on the base 55, so as to partially surround each module, to improve the hydraulic seal; the frame 81 is provided with opposing protrusions 82, of adequate dimensions to be inserted between the modules 7, near their end 82, to delimit the feed chambers 83, communicating both with the corresponding slot 80 and with one of the groups of expulsion chambers 14. A metal or resin sheet 85, normally made of Kapton ™, is glued to the frame 81 and to the three active modules 7. The sheet is provided with three parallel rows of nozzles 18; the nozzles 18 are arranged facing the corresponding resistors contained inside the chambers 14, so that the ink drops are ejected in a direction perpendicular to the surface of the resistors themselves; the sheet 85 also constitutes the upper closing wall of the chambers 83. When assembling the heads on the plate 22 (fig.4), the plates 85 are initially fixed to the frames 81 by means of some points of UV glue 86, to keep them firm and integral with the frame 81, before being separated from the coil, not shown in the drawings, on which they are wrapped, in the case of plastic sheets, or separated from a larger pre-printed sheet, in the case of metal sheets; finally the sheets 85 are glued by hot pressing onto the completed wafer. The “fiat cable” 45 has only one opening 87, and the connection pads 88 of the “fiat cable” 45 are connected to corresponding pitches 88', obtained along the edge of the short sides 89 of the 7 modules; with this geometry it is possible to use even more than three modules, for example four modules (three colours plus black), with obvious advantages, since the nozzle holder plate 85 can be made in a single piece, the head takes up less horizontal space and the hydraulic seal between the 7 modules and towards the environment is more secure. The head configuration shown in Fig. 13, in which the “fiat cable” 45 is soldered end-to-end to the active modules 7, or on pads arranged on the short sides 89 of the modules themselves, is made possible by the use of an addressing circuit operating in 3D mode, with simple active N-MOS devices, and in particular of the type described in the international patent application PCT / ITOO / 00271 with priority 12 / 07 / 1999 in the name of Olivetti Lexikon SpA, and partially reported in Fig. 14. For simplicity of exposition and as an example, it is assumed that each active module 7 of the head in fig. 13 comprises 112 nozzles, each of which corresponds to a resistor Rn (N= 1...112) which in turn can be activated by a corresponding transistor Tn; the resistors Rn, and therefore the transistors Tn, are organised in 8 pairs of groups 90 (fig. 14) of seven resistors Ri,R2,...Rz each; the resistors Ri,R2,...R7 of each group 90 are connected between the “drain” D of each corresponding transistor Ti, T2, ...Tz and in common with each primitive line Pm (M= 1...8); the transistors Ti, T2, ...Tz of each group 90 have their “source” connected in common with the “drain” of a selector transistor 91, 9 la, while each of their the “gate” terminal is connected to one of the seven lines Aa (A= 1...7); in turn the selector transistors 91, 9 la have the “source” connected to a common ground terminal 92. The selector transistors 91 belonging to each first group and the selector transistors 9 la belonging to each second group of each pair have their “gate” terminal connected to one or the other of the two selection enable lines SW1 and SW2 respectively. Therefore, with the settings chosen for the example above, where the number of primitives P = 8, the number of addresses per primitive is A = 7 and the number of SW selections = 2, the following are required: 8 (P) + 7 (A) + 2 (SW) = 19 external contacts (pads) 88' for each active module 7, which is therefore equipped with: 8 (P) * 7 (A) * 2 (SW) =112 resistors Rn, or 112 ejector nozzles 18 (fig. 13). Figure 15 schematically represents an active module 7, made according to the provisions of the example cited; the plan dimensions of the active module 7 are 10.5 mm in length and 1.6 mm in width of the short side 94. The 19 88' pitches are divided (+ one spare) into ten on each side 94, spaced 20 pm apart, for each pitch having a width of 140 pm. The circuit of fig. 14 is schematically represented on the active module 7 of figure 15 in the following way: the staggered lines 95 represent the sixteen groups of resistors Rn, each pair of groups being connected with a line of primitive (Pm); the boxes 96 with vertical lines represent the transistors Tn corresponding to each group of resistors Rn, which receive the address signals Aa from a bundle 97 of conductors, which also includes two conductors for the pulses SW, which drive the selection transistors 91, represented by barred rectangles 98, below which runs a large ground return conductor 99. The 88' pads, located on the short side 94' (on the left in fig. 15), are therefore connected to the following conductors: PI, P2, P3, P4; Al, A2, A3, A4; GRN; while the pads 88', arranged on the short side 94 (on the right in fig. 15), are connected to the conductors: P5, P6, P7, P8; A4, A5, A6, A7; SW1, SW2. From what has been described, it is clear that the composite print heads, made according to the invention, have numerous advantages over the heads according to the prior art; in fact, their construction is simpler because, since the ink supply slots are built separately, they are exempt from the restrictions of precision and high quality of finish required by traditional construction techniques; furthermore, the new heads are more economical because the active modules can be built in smaller dimensions than previous techniques, saving significant quantities of silicon. and of the noble metals used for resistors and for the internal interconnections, as well as work on the fabrication of each individual chip. A further advantage achieved with the heads according to the invention consists in the fact that, with the use of 3D mode addressing circuits, integrated in the active modules, a significant reduction in the number of external connections is achieved, this allows the "fiat cable" conductors to be connected to pads arranged even on the short sides of the active modules, making it possible to achieve greater compactness of the multiple print heads. £ a]

Claims

CLAIMS 1. Inkjet print head (1) of the type comprising a plurality of nozzles (18) and a corresponding plurality of heating elements (10), selectively activatable, to cause the expulsion of ink drops through said nozzles (18), said nozzles being arranged facing the corresponding heating elements (10), the latter being housed in respective chambers (14) suitable for containing ink, characterised in that said print head (1) is composed of an active module (7) and a support element (3) for said active module (7), said active module (7) being constituted by a thin silicon plate (8), carrying said plurality of heating means (10) and said chambers (14), said support element (3) being constituted in turn by a portion of a plate (22) of rigid and insulating material, provided with a supply duct (5) for said ink,crossing the thickness of said support element (3), said active module (7) being constructed separately from said support element (3) and subsequently fixed, integrally on said support element (3)., 2. Print head according to claim 1, characterised in that said active module (7) is positioned on said support element (3) in such a way that said chambers (14) face said feed duct (5).

3. Print head according to claim 1, or 2, characterised in that said feed duct (5) is made in the form of an elongated slot in the longitudinal direction of said active module (7).

4. Print head according to claim 1, or 2, or 3, characterised in that it further comprises a resin frame (16) fixed on said support element (3) and provided with an opening (16a) of a shape substantially complementary to the dimensions of said active module (7), suitable for housing said active module (7) in contact along at least three contiguous sides (a, b, c) of said opening (16a).

5. Print head according to claim 4, characterised in that each of said openings (16a) also houses said supply duct (5), arranged between a fourth side (d) of said opening (16a) and the chambers (14) of said corresponding active module (7), to define an ink reserve chamber (5a), communicating with the chambers (14) of said active module (7) and with the corresponding supply duct (5)- 6. Print head according to claim 4 or 5, characterised in that a plate (17) carrying a plurality of nozzles (18), corresponding to said chambers (14), is fixed partly above said active module (7) and partly above said frame (16), said plate (17) constituting an upper closing wall for said chambers (14) and for said communicating chamber (5a).

7. Printhead according to one of the preceding claims, characterised in that said active module (7) is provided with a plurality of electrical contact pads (37,42), connected to said heating means (10), suitable for being welded to a bundle of power wires (45).

8. Print head according to claim 7, characterised in that said active module (7) comprises integrated electronic control circuits, connected between said pads (37) and said heating means (10), suitable for selectively activating said heating means (10), said pads (37) being arranged on a long side (b) of said active module (7), opposite to said chambers (14).

9. Print head according to claim 7, characterised in that said active module (7) comprises integrated electronic control and selection circuits, suitable for selectively activating said heating means (10) and connected between said pads (42) and said heating means (10), said pads (42) being arranged on both short sides (a, c, 43) of said active module.

10. Multiple colour inkjet print head, of the type comprising groups of nozzles (18) and corresponding groups of heating means (10), selectively activatable, to cause the expulsion of ink drops through said groups of nozzles (18), said nozzles (18) of each group being arranged facing the corresponding heating means (10), the latter being housed in respective chambers (14) suitable for containing ink, characterised in that said print head is composed of a plurality of active modules (7), and a single support element (3) for said plurality of active modules (7), each active module (7) being constituted by a thin silicon plate (7) carrying a corresponding group of heating means (10) and related chambers (14), said support element (3) being in turn constituted by a portion of a plate (22) of rigid and insulating material and provided with an ink supply duct (5), associated with each active module (7) of said plurality, each duct (5) passing through the thickness of said support element (3), the active modules (7) of said plurality being constructed separately from said support element (3) and subsequently fixed, solidly onto said support element (3).

11. Multiple print head according to claim 10, characterised in that the active modules (7) of said plurality are positioned on said single support element (3) in such a way that the chambers (14) of each module face a corresponding feed duct (5).

12. Multiple print head according to claim 10, or 11, characterised in that it further comprises a resin frame (16) fixed on said single support element (3), and provided with at least one opening (16a) having a substantially complementary shape of the dimensions of a corresponding active module (7) and being suitable to house said corresponding active module (7) in contact along at least three adjacent sides (a, b, c) of said opening (16a).

13. Multiple print head according to claim 12, characterised in that each of said openings (16a) also houses said supply duct (5), arranged between a fourth side (d) of each opening (16a) and the chambers (14) of said corresponding active module (7), to define a plurality of ink reserve chambers (63a), each communicating with the chambers (14) of each of said modules (7) and with the corresponding supply duct (63).

14. Multiple print head according to claim 12 or 13, characterised in that a plate (62, 72, 78), carrying groups of nozzles (18), associated with said chambers (14), is fixed partly above at least one of said active modules (7) and partly above said frame (16), said plate constituting an upper closing wall for each of said communicating chambers (63a) and for the chambers (14) facing said communicating chambers (63a).

15. Multiple print head according to one of claims 10 to 14, characterised in that said plurality of active modules comprises three active modules (7) arranged side by side in parallel, in a horizontal direction, i.e. parallel to the writing direction (F), fixed on a single support element (55), the chambers (14) of each active module (7) facing a corresponding feed duct (63) of said support element (55).

16. Multiple printhead according to one of the claims 10 to 14, characterised in that said plurality of active modules comprises four active modules (7) placed side by side, two by two, fixed on a single support element (55), to be able to print with three colours plus black, the chambers (14) of each active module (7) facing a corresponding supply duct (71) of said support element (55).

17. A single-colour multiple print head according to one of claims 10 to 14, characterised in that said plurality of active modules comprises two identical and aligned head-to-head active modules (7), fixed to a single support element (55), for printing with a single colour, said support element (55) comprising a single supply duct (77^, extending in a position facing the chambers (14) of both said two active modules (7), said chambers (14) being spaced at a constant pitch, said frame (16) being provided with an opening (16a) suitable for housing both said two active modules (7) and said nozzle holder plate (78) being sized to cover both said two active modules (7).

18. Multiple print head according to one of claims 15 to 17, characterised in that each active module (7) of said plurality comprises a group of pads (68,76) arranged on a long side of said active modules (7), opposite to said chambers (14).

19. Multiple print head according to claim 18, characterised in that each active module (7) of said plurality comprises integrated electronic control circuits (12), suitable for selectively activating said heating means (10) and connected between said groups of pads (68,76) and said heating means (10).

20. Multiple print head according to one of claims 10 to 14, characterised in that said plurality of active modules comprises at least three active modules (7) arranged side by side in parallel, in a direction parallel to the writing direction (F), fixed on a single support element (55), the chambers (14) of each active module (7) facing a corresponding supply duct (80) of said support element (55), each active module (7) of said plurality comprising integrated electronic control circuits (12) and integrated CMOS or NMOS logic selection circuits (40), suitable for selectively activating a plurality of groups of heating elements (10, Rn) and connected between groups of pads (42, 88') and said heating elements (10, Rn), said pads (42, 88') being arranged on the opposite short sides (43, 89) of each active module (7).

21. A multiple print head according to claim 20, characterized in that said CMOS, or NMOS (40) integrated logic selection circuits comprise a 3D mode addressing circuit for selectively activating said heating elements (10, Rn), said addressing circuit comprising selection transistors (91, 91a) associated with each of said groups of heating elements (10, Rn), adapted to sequentially activate predetermined heating elements (10, Rn), in each of said groups, defined by a predetermined combination between a selection address (Aa) and a primitive logic signal (Pm), said selection transistors (91,9 la) being enabled by a logic enable signal (SW1, SW2).

22. Method for making an inkjet print head of the type comprising a plurality of nozzles (18) and a corresponding plurality of heating elements (10), selectively activatable, to cause the expulsion of ink drops through said nozzles (18), said nozzles (18) being arranged facing the corresponding heating elements (10), the latter being housed in respective chambers (14) suitable for containing ink, said procedure comprising the following steps: 1) to create a plurality of active modules (7) each of which is made up of a thin silicon plate, carrying said plurality of heating means (10) and said chambers (14); 2) trace on a surface (20) of a plate (22) of thin, rigid and electrically insulating material, reference marks (29), a grid of contour and separation lines (32) to delimit a plurality of support elements (3) for said active modules, which can be cut from said plate; 3) make on each of said support elements (3), delimited by said contour lines (32), at least one opening (5), crossing the thickness of said support element; 4) fix on each of said support elements at least one of said active modules (7), with reference to said marks (29), so that said plurality of chambers (14) faces each of said openings (5); 5) fix on each of said support elements (3) a resin frame (16), provided with at least one opening (16a) of complementary shape with the dimensions of each of said active modules (7), suitable for housing a corresponding active module (7), and arranged adjacent to at least three contiguous sides of said active module (7) and sized to define an ink chamber arranged between a fourth side (e) of said opening and the chambers (14) of said active module (7); 6) fix on at least one of said active modules (7), or already fixed to the relative support element (3), a plate (17, 62, 72,78) carrying a plurality of nozzles (18), corresponding to said plurality of chambers (14), in such a way that said nozzles face corresponding heating elements (10). 7) cut said plate (22) along said contour lines (32) to separate said support elements (3) carrying at least one of said active modules (7), said comets (16) and a corresponding nozzle-holding plate (17, 62, 72,78).

23. Method according to claim 22, characterised in that step 2) further provides for tracing on said surface (20) of said plate (22) the outline (30) of said opening (5) and the outlines (33, 34) of adhesive dispensing areas for fixing on said plate (22) said active modules (7).

24. Method according to claim 22, characterised in that step 3) further provides for making said opening (5) in the form of an elongated slot in the longitudinal direction of said active modules (7), following said traced contour (30).

26. Process according to claim 22, characterised in that step 4) is preceded by the operation of spreading an adhesive inside said dispensing areas (30.33).

27. Process according to claim 22, characterised in that step 5) is preceded by the operation of spreading an adhesive within a dispensing area (34) surrounding said active modules (7), to glue said frame (16).

28. Method according to claim 22, characterised in that step 6) further provides that said plate (17, 62, 72, 78) is positioned partly above said at least one active module (7), and partly above said frame (16), and that the fixing is carried out under pressure at a controlled temperature and for a controlled duration.

29. Composite inkjet printhead and method for manufacturing the same, substantially as described, with reference to the figures in the attached drawings. pp Oliveta£2èt 3. d. TO.*' I was Bobbio