Method of manufacturing wiring board, and liquid ejection head having wiring board

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a wiring board, and a liquid ejection head having the wiring board, and more particularly to manufacturing technology for a wiring board in which plating wires are formed in grooves formed by resin molding.

2. Description of the Related Art

Circuit wiring technology for performing high-density installation has been developed for electronic devices, in order to achieve size and weight reductions, and high functionality, in such devices.

For example, a two-shot molding method and a one-shot molding method are known for manufacturing circuit components having conductive circuit wires formed on a substrate made of synthetic resin.

In the two-shot molding method, firstly, primary molding is carried out using a resin containing a plating catalyst, whereupon surface roughening (etching) is performed on the primary molding object. Alternatively, the primary molding object is formed of a resin that contains no plating catalyst, and surface roughened, then has a plating catalyst deposited on the roughened surface. Thereupon, secondary molding is carried out so as to partially cover the primary molding object with a resin that contains no plating catalyst. Electroless plating or electrolytic plating is then carried out on the exposed surfaces of the primary molding object, thereby depositing metal onto the circuit forming sections corresponding to the exposed parts of the primary molding object. In this way, in the two-shot molding method, the molding is carried out twice.

In the one-shot molding method, circuit forming sections are molded in a prescribed shape from synthetic resin, and surface roughening and plating catalyst deposition are then carried out over the whole surface of the molding object. Thereupon, electroless plating is performed over the whole surface of the molding object, the parts other than the circuit forming sections are masked, and the plating in the areas other than the masked areas is removed, whereupon electrolytic plating is performed on the circuit forming sections, thereby depositing metal on the circuit forming sections.

However, the two-shot molding method involves a large amount of waste, since it uses the plating catalyst for the whole of the primary molding object, and furthermore, the manufacturing process becomes complex, since it requires two molding steps: primary molding and secondary molding.

The one-shot molding method requires a complicated manufacturing process, and also creates wasted material. What is more, if surface roughening is carried out by using strongly acidic chemicals, such as chromic acids, in addition to problems relating to environmental suitability, there is also a drawback in that if the plating in the regions outside the mask is removed by sandblasting with micro-particles, or the like, then scratches are liable to occur due to the scattering of the micro-particles, and non-uniformities arise.

In view of this, Japanese Patent Application Publication No. 2002-270995 discloses a method of manufacturing a circuit component in which a molded component is formed by molding synthetic resin into a prescribed external shape, preparation processing (surface roughening) is performed by wet blasting on the circuit forming surface of the molded component, a plating catalyst is deposited on the circuit forming surface that has undergone preparation processing, and the plating catalyst is then activated. Subsequently, electroless plating is performed at locations that are to form conducting sections, and electrolytic plating is then carried on the electroless plating sections, thereby forming conducting sections on the circuit forming surface.

Furthermore, Japanese Patent Application Publication No. 2005-50992 discloses a wiring board in which non-conductive metal-containing resin layers containing dispersed metal micro-particles, are formed selectively on a wiring board which is formed by transfer of a visible image by an electrophotographic method, whereupon a conductive metal layer is formed on top of the metal-containing resin layer, by means of electroless plating and/or electrolytic plating, and a thermally curable resin layer is then formed between the respective metal-containing resin layers on the substrate.

However, in the method disclosed in Japanese Patent Application Publication No. 2002-270995, desired conducting layers are formed after surface roughening by wet blasting and selective catalytic activation (patterning) by UV or heat treatment; however, the selective catalytic activation by UV irradiation or heat treatment is substantially a patterning step, and hence there is no substantial reduction in the number of plating steps. Furthermore, there is also a problem in that it is difficult to carry out patterning by UV irradiation or heat treatment, on the surface of the resin molding that has been formed freely to a desired shape.

Moreover, the wiring board disclosed in Japanese Patent Application Publication No. 2005-50992 involves the selective formation of conducting layers by electrophotography. Since the patterning of the conducting layers is carried out by electrophotography, then it is impossible to achieve a resolution exceeding the resolution of the electrophotographic process. Furthermore, it is difficult to carry out patterning by electrophotography on the surface of a resin molding that has been formed freely to a desired shape.

SUMMARY OF THE INVENTION

The present invention has been contrived in view of the foregoing circumstances, an object thereof being to provide a method of manufacturing a wiring board, and a liquid ejection head comprising this wiring board, whereby the plating process is shortened, the adhesion of the plating is improved, and conducting layers can be formed on a surface having a freely designed shape.

In order to attain the aforementioned object, the present invention is directed to a method of manufacturing a wiring board, comprising the steps of: forming a flow channel by covering a groove formed in a resin substrate by means of a covering member; and filling a liquid containing conductive metal into the flow channel, and depositing the conductive metal onto wall faces of the flow channel.

According to the present invention, close adhesion of conductive metal to the flow channel (groove) is improved, and furthermore, the manufacturing process can be simplified.

Preferably, the resin substrate is formed by resin molding by filling a resin material into a mold and curing the resin material.

According to this aspect of the present invention, high-density wiring becomes possible, and the freedom of the substrate shape and the wiring shape is increased.

Preferably, the liquid containing conductive metal is a material which, when making contact with an electroless plating liquid, induces electroless precipitation of the metal that is to be deposited; and the method further comprises the step of forming an electroless plating layer by using the metal having been deposited on the flow channel as an origin.

According to this aspect of the present invention, it is possible to reduce the wiring resistance and to form wires which are able to flow high current. Furthermore, the material inducing electroless precipitation of the metal that is to be plated by making contact with an electroless plating liquid is, for example, an active plating catalyst material, such as palladium (Pd).

Preferably, the method further comprises the step of forming an electrolytic plating layer by using the electroless plating layer as a seed layer.

According to this aspect of the present invention, in situations involving a very small signal system and limited wiring area, it is possible significantly to reduce the steps in the conducting layer formation process by using the wiring process up to the electroless plating step.

Alternatively, it is also preferable that the liquid containing conductive metal is a conductive paste.

According to this aspect of the present invention, in the case of the conductive paste, the covering member may be left in place, or it may be removed. If the covering member is left in place, then it forms a protective layer for the wires, and if the covering member is removed, then connection work becomes easier.

Preferably, the resin substrate is made of an epoxy resin; and the method further comprises the steps of: introducing an ion exchange group into the wall faces of the flow channel by causing liquid containing an oxyacid of sulfur to flow into the flow channel; and then causing a liquid containing copper ions and a reducing agent to make contact with the groove in the resin substrate.

According to this aspect of the present invention, if the substrate formed with the conducting layer is made of epoxy resin, then in order to deposit copper ions readily on the substrate, a sulfone group is introduced into the groove of the substrate. Electroless plating can be carried out readily onto the epoxy resin substrate by depositing a sulfone group inside the groove by flowing H₂SO₄through same.

Preferably, the resin substrate is made of polyimide; and the method further comprises the steps of: introducing an ion exchange group into the wall faces of the flow channel by causing liquid containing an aqueous alkali solution to flow into the flow channel; and then causing a liquid containing copper ions and a reducing agent to make contact with the groove in the resin substrate.

According to this aspect of the present invention, if the substrate formed with the conducting layer is made of polyimide resin, then in order to deposit copper ions readily on the substrate, a cationic exchange group is introduced into the groove of the substrate. Electroless plating can be carried out readily onto the polyimide resin substrate by depositing a cationic exchange group inside the groove by flowing KOH through same.

Preferably, the method further comprises the steps of: forming the groove formed in the resin substrate in a shape whereby a plurality of desired conducting layers are connected together; forming the conducting layers by means of a same operation; and then dividing the conducting layers by cutting.

According to this aspect of the present invention, it is possible to divide the wires and hence the load in the filling step can be reduced. Moreover, when the groove is formed in a shape whereby a plurality of conducting layers are connected together, and the connecting section is shaped to form a liquid accumulator, then it is possible to reduce the pressure loss during the step of filling the liquid into the flow channels, as well as being able to remove bubbles that may arise, by collecting same in the liquid accumulator.

Preferably, the method further comprises the steps of: forming grooves in both surfaces of the resin substrate; forming a through hole which connects the grooves in the surfaces; and forming flow channels by covering the grooves in the surfaces.

According to this aspect of the present invention, it is possible to form wires on both surfaces of the substrate.

In order to attain the aforementioned object, the present invention is also directed to a liquid ejection head, comprising: a plurality of pressure chambers which are connected respectively to a plurality of nozzles ejecting liquid and are arranged in a two-dimensional configuration; a diaphragm which constitutes wall faces of the pressure chambers on a side of the pressure chambers reverse to a side adjacent to the nozzles; an ejection device structure formed by a plurality of piezoelectric elements which respectively deform the pressure chambers and are disposed respectively at positions corresponding to the pressure chambers on a surface of the diaphragm reverse to a surface adjacent to the pressure chambers; and a substrate on which electrical wires for electrically connecting a drive circuit for driving the piezoelectric elements with drive electrodes of the piezoelectric elements are arranged, conducting layers to be the electrical wires being formed by the above-described method.

According to the present invention, it is possible to arrange electrical wires at high density and hence the head can be made more compact in size.

As described above, according to the present invention, close adhesion of conductive metal to the flow channel (groove) is improved, and furthermore, the manufacturing process can be simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

The nature of this invention, as well as other objects and advantages thereof, will be explained in the following with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures and wherein:

FIG. 1A is an oblique diagram of a substrate in which grooves are formed by resin molding according to a first embodiment of the present invention, and FIG. 1B is a cross-sectional diagram along line 1B-1B in FIG. 1A;

FIG. 2 is an oblique diagram showing a state where flow channels are formed by covering the grooves by pressing a covering member to the substrate formed with the grooves in FIGS. 1A and 1B;

FIG. 3 is a conceptual diagram showing a situation in which the plating catalyst is filled into the flow channels formed as shown in FIG. 2;

FIGS. 4A and 4B are cross-sectional diagrams showing a state of controlling the roughness of a portion of the grooves of the substrate according to a second embodiment;

FIG. 5 is an illustrative diagram showing a molding method using a UV curable resin according to a third embodiment;

FIGS. 6A and 6B are illustrative diagrams showing a molding method based on heating and pressurization according to the third embodiment;

FIG. 7A is a plan diagram showing a state in which a recess which connects a plurality of grooves is formed in a substrate according to a fourth embodiment, and FIG. 7B is a cross-sectional diagram along line 7B-7B in FIG. 7A;

FIG. 8 is an illustrative diagram showing a state where the conducting layer formed on the substrate shown in FIGS. 7A and 7B is to be divided;

FIG. 9 is an illustrative diagram showing conducting layers obtained by dividing the conducting layer along line A-A in FIG. 8;

FIG. 10 is an illustrative diagram showing conducting layers obtained by dividing the conducting layer along lines A-A and B-B in FIG. 8;

FIG. 11 is an illustrative diagram showing a state where plating catalyst is filled into the grooves formed in the substrate, according to a fifth embodiment;

FIG. 12A is a plan diagram showing a substrate having a curved surface according to a sixth embodiment, and FIG. 12B is a cross-sectional diagram along line 12B-12B;

FIGS. 13A and 13B are illustrative diagrams showing states where plating catalyst is filled into grooves formed in the substrate in FIGS. 12A and 12B;

FIGS. 14A and 14B are cross-sectional diagrams showing embodiments of substrates having surfaces other than a flat surface;

FIG. 15A is a plan diagram showing a substrate according to a seventh embodiment, FIG. 15B is a cross-sectional diagram along line 15B-15B in FIG. 15A, and FIG. 15C is a bottom face diagram;

FIG. 16A is an illustrative diagram showing a state where a plating catalyst is filled into a groove formed in the substrate in FIGS. 15A to 15C, and FIG. 16B is a cross-sectional diagram showing a state where a conducting layer is formed on this substrate; and

FIG. 17 is a cross-sectional diagram showing an approximate view of a liquid ejection head according to an eighth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A to 3 show a method of manufacturing a wiring board according to a first embodiment of the present invention.

The method of manufacturing a wiring board according to the present embodiment involves: forming a substrate having grooves by resin molding, forming flow channels by closing off the grooves after they have been formed, introducing a liquid containing a conductive metal (namely, an active plating catalyst material, in other words, a material which induces electroless precipitation of the metal that is to be plated when it makes contact with an electroless plating solution; hereinafter simply referred to as a “plating catalyst”), into the flow channels, thereby depositing the catalyst onto the grooves, and forming conducting layers which will become electrical wires on the substrate, by means of electroless plating or electrolytic plating.

Firstly, a substrate 10 having grooves 12 is formed by resin molding, as shown in FIG. 1A. Here, for the purpose of the description, the shape of the grooves 12 is represented by a simplified shape, but the invention is not limited in particular to the shape illustrated, and the grooves may be formed to any desired shape. Furthermore, there are no particular restrictions on the method of forming grooves by resin molding, provided that it is a method which enables groove shapes to be formed, such as injection forming.

FIG. 1B shows a cross-sectional diagram along line 1B-1B in FIG. 1A. As shown in FIG. 1B, the grooves 12 are formed to a certain depth with respect to the substrate 10, and will subsequently have electrical wires formed therein. Furthermore, with regard to the shape of the grooves 12, the groove width is determined by the electrical wiring density, but as regards the depth of the grooves 12, considering that the grooves 12 form flow channels along which the liquid containing conductive metal (plating catalyst) travels, and it is hence desirable that the depth is increased when the density is high, thereby reducing the pressure loss during travel of the liquid, while at the same time, the adhesion of the conductive layer thus formed can be guaranteed and the electrical resistance of the conducting layer can be reduced, by ensuring the contact surface area of the conducting layer.

Next, as shown in FIG. 2, a flat plate-shaped covering member (closing member) 14 is pressed from above against the substrate 10 in which the grooves 12 have been formed, thereby covering the grooves 12 and forming the flow channels 16. The covering member 14 of the grooves 12 forming the flow channels 16 is not limited in particular to any material, provided that it has good adhesion with the substrate 10 in which the conducting layer is to be formed. For example, sheet-shaped silicone rubber, or the like, having low hardness (e.g., in the range of 10 to 30 degrees specified in JIS K 6253) has good adhesion characteristics, and is suitable for forming flow channels.

Next, as shown in FIG. 3, in the state where the covering member (closing member) 14 is pressed against the substrate 10, a plating catalyst tank 18 and a pump 20 are connected to the flow channels 16 formed by covering the grooves 12, by means of a tube 22, the pump 20 is driven, and the liquid (the liquid containing the conductive material, such as the plating catalyst) is circulated through the flow channels 16.

As a method of making the liquid containing conductive metal (plating catalyst) flow into the flow channels 16 (grooves 12), in addition to this method in which the liquid containing conductive metal is conveyed by creating a pressure differential between the ends of the flow channels 16, by means of the pump 20, other effective methods are a method in which the liquid containing conductive metal is made to flow into the flow channels 16 by capillary action, or a method which is essentially the same as the method of creating a pressure differential, but in which the liquid containing conductive metal is drawn into the flow channels 16 by creating a vacuum therein, or the like.

Next, electroless plating is carried out on the grooves 12 into which the plating catalyst has been deposited by introducing the liquid containing conductive metal into the flow channels 16, and the covering member (closing member) 14 is then removed and electrolytic plating is carried out, using the electroless plating as a seed layer. In this way, conducting layers are formed in the grooves 12. Thereby, electrical wires are formed in the sections of the grooves 12.

Therefore, it is possible to form wires that have low resistance and along which high current can flow.

Furthermore, to give a more detailed description of plating in this way, in general, electroless plating is carried out by firstly depositing a catalytic active material (by partial deposition), and then reducing (by partial reduction) and precipitating the catalytic active material, and performing electroless plating onto this active material. At the initial stage of depositing the catalytic active material, it is desirable for the wires to be patterned by using the aforementioned groove wires as the flow channels 16, since this produces the least waste.

Furthermore, when a general catalytic chemical (catalyst) is introduced into the flow channels 16 and the catalytic active material is partially deposited, then electroless plating should be carried out after electrostatic deposition by flowing a tin-palladium (Sn—Pd) colloid and reducing Pd by means of an accelerator. This is because the metal, such as Cu, Au, Ag, Pt, Pd, or the like, is reduced by a reducing agent, such as formaldehyde, and hence plating can be formed on this metal.

Furthermore, the characteristics of the aforementioned catalysts are such that Pd colloid has a negative charge, which is stabilized by the superabundance of Sn²⁺, H⁺ and Cl⁻.

Moreover, it is preferable that only the interior of the grooves 12 (flow channels 16) undergoes surface modification. Therefore, an ion exchange group is introduced inside the grooves 12 only, copper ions are deposited and reduced to metallic copper, and electroless plating is then carried out using this copper as a catalytic core.

Furthermore, when the material of the substrate 10 is an epoxy resin, then a sulfone group is introduced into the inner surfaces of the grooves 12, by using H₂SO₄, whereupon copper sulfate is flowed through the grooves 12 (flow channels 16), copper ions are deposited and reduced to metallic copper by using NaBH₄, and electroless plating is then carried out using this copper as a catalytic core. Here, the manufacturing conditions involve flowing a concentrated solution of 14M (mol/liter) for 3 minutes at 60° C., but instead of this, it is also possible to flow a low-concentration solution at a higher temperature for a longer period of time.

Moreover, when the material of the substrate 10 is polyimide, then the imide chains on the inner surfaces of the grooves 12 are broken by an alkaline solution such as KOH, for example, thereby forming a cationic exchange group. Copper ions are deposited and then reduced to metallic copper by using NaBH₄, and this copper is used as a catalytic core to perform electroless plating. Here, the manufacturing conditions involve flowing a concentrated solution of 5M (mol/liter) for 5 minutes at 50° C., but it is also possible to flow a low-concentration solution at a higher temperature for a longer period of time.

Furthermore, in the above-described embodiments, a plating catalyst is flowed inside the grooves 12 (flow channels 16), as a liquid containing conductive metal, but instead of this, it is also possible to flow a conductive paste. In this case, the conductive paste injected inside the grooves 12 forms the electrical wires directly, itself, and hence there is no need to carry out electroless plating and/or electrolytic plating, and the covering member (closing member) 14 can be left in position rather than being removed. If the covering member (closing member) 14 is left in place, then it forms a protective layer for the wires, and if the covering member (closing member) 14 is removed, then a beneficial effect is obtained in that connections can be performed easily.

Next, a second embodiment of the present invention is described.

In this second embodiment, the surface roughness of the inner sides of the grooves is controlled to a suitable value in order to improve anchoring effects which enhance the adhesion of the plating to the interior of the grooves which form the electrical wires. More specifically, the surface roughness of the interior of the grooves is set to Ra 0.4 or above in order to improve the adhesion (anchoring effect) of the plating, and the close contact face with the covering member (closing member) which forms the flow channels by covering the grooves is formed with a surface roughness of Ra 0.2 or below.

In practice, in order to form surface roughness of this kind on the interior of the grooves of a substrate formed with grooves, and on the close contact face with the covering member, a surface roughness is previously formed in this manner on the mold used for resin molding of the substrate, in the portions corresponding to the grooves and the close contact faces, in such a manner that this surface roughness is transferred to the substrate during resin molding.

As shown in FIG. 4A, the roughness of the smooth surface 24a corresponding to the close contact face of the groove forming mold 24 is Ra 0.2 or less, and the surface roughness of the region indicated by the arrows in FIG. 4A of each of the projecting sections (projections) 24b corresponding to the grooves is formed to Ra 0.4 or above. The groove forming mold 24 can be formed with projecting sections 24b which correspond to the grooves, by means of micromachining, electroforming, or the like.

When forming the substrate, as shown in FIG. 4B, a thermally curable epoxy resin 28, which has been heated, is filled into the mold 26, the groove forming mold 24 is then pressed against same from above, and the resin is cured, whereupon the thermally curable epoxy resin 28 is removed from the mold. Thereby, the portions 28a of the thermally curable epoxy resin 28 which correspond to the flat surfaces 24a of the groove forming mold 24 are formed to have a roughness of Ra 0.2 or below, thus forming a close contact surface with the covering member, and the portions 28b which correspond to the projecting sections 24b of the groove forming mold 24 are formed to a surface roughness of Ra 0.4 or above.

Next, a third embodiment of the present invention is described.

In this third embodiment, grooves are formed in a substrate by means of a mold.

There are three types of method for forming the grooves: the grooves may be molded in a thermally curable epoxy resin, or molded in a resin that is curable by irradiation of energy, or alternatively, the grooves may be formed by means of a hot press (heating and pressurization).

Firstly, molding the grooves in a thermally curable epoxy resin is the same as the method described in FIGS. 4A and 4B. If a thermally curable epoxy resin which has been heated and melted is molded by being introduced into a metal mold, then since the thermally curable epoxy resin has good fluidity, it has highly beneficial properties for forming grooves for high-density wiring.

Next, FIG. 5 shows a molding method using ultraviolet (UV) curable resin. As shown in FIG. 5, the groove forming mold in this case is formed with projection-shaped sections 30a corresponding to the grooves, by dry etching, or the like, in an optically transparent material, such as quartz, glass, or the like. An acrylic type UV-curable resin is suitable for use as the resin material. The UV-curable resin 34 is introduced into a mold (lower mold) 32, the groove forming mold 30 is pressed against the resin, and UV light is irradiated from above, thereby curing the UV-curable resin 34, and thus forming a substrate in which grooves 32a are formed.

Furthermore, next, FIGS. 6A and 6B show a groove molding method based on heating and pressurization. As shown in FIG. 6A, in this case, a groove forming mold 36 is heated to the glass transition temperature (Tg point) of a thermoplastic resin 38, and a pressing force is applied to the thermoplastic resin 38, thereby transferring projecting shapes to the resin. Accordingly, as shown in FIG. 6B, grooves 38a having a shape which corresponds to the projecting shape sections 36a corresponding to the grooves of the groove forming mold 36.

In this way, by forming a substrate having grooves by means of resin molding, it is possible to achieve high-density wiring, and furthermore, it is possible to increase the freedom of the shape of the wiring board and the shape of the wiring.

Next, a fourth embodiment of the present invention is described.

In the present embodiment, recesses in which a plurality of grooves are linked together are formed on the substrate, the grooves are covered, a plating catalyst is filled into same, and conducting layers are formed and then cut by laser, or the like, to form prescribed conducting layers.

FIGS. 7A and 7B show a state where a recess having a plurality of grooves linked together is formed on the substrate. FIG. 7A is a plan diagram, and FIG. 7B is a cross-sectional diagram along line 7B-7B in FIG. 7A.

As shown in FIG. 7A, two grooves 42 which are substantially parallel are formed respectively in left-hand and right-hand positions, in a substrate 40, and these four grooves 42 are connected together by means of a recess 44. Furthermore, as shown in FIG. 7B, in this embodiment, the grooves 42 and the recess 44 formed in the substrate 40 have the same depth, but the invention is not limited in particular to this.

Then, as shown in FIG. 8, if the conducting layer is cut by laser, or the like, along line A-A in FIG. 8, for example, then two conducting layers 42a and 42b are obtained as shown in FIG. 9. Furthermore, if the conducting layer is cut by laser or the like along both line A-A and line B-B in FIG. 8, then four conducting layers 42c, 42d, 42e and 42f are obtained, as shown in FIG. 10.

Thereby, it is possible to separate the wires and hence the load of the plating catalyst filling step can be reduced.

In this case, the recesses 44 in the connecting sections of the plurality of grooves 42 are formed to a shallow depth, and if the required portions of the grooves 42 are made deeper, then it is possible to leave only the portions of the grooves 42 which form the conducting layers, by grinding the surface and cutting away the connecting sections. In this way, it is also preferable to alter the depth of the recess 44 and the grooves 42.

Next, a fifth embodiment of the present invention is described.

In the present embodiment, liquid accumulating grooves which span across a plurality of grooves forming conducting layers are provided in order to reduce the pressure loss when the liquid (plating catalyst) travels along the flow channels formed by covering the grooves formed in the substrate. An internal flow channel conveyance pressure is applied to the grooves and a plating catalyst is thereby deposited in the grooves.

FIG. 11 shows a general overview of this embodiment. As shown in FIG. 11, flow channels are formed by placing a covering member (closing member) 46 in close contact with a substrate 40 formed with grooves 42 and a recess 44 shown in FIGS. 7A and 7B, for example, thereby closing off the grooves 42 and the recess 44. In this case, the recess 44 which connects together a plurality of grooves 42 forms a liquid accumulating groove which spans across a plurality of grooves 42.

A plating catalyst is sucked in from a plating catalyst tank 48, by means of a pump 50, the plating catalyst is injected into the grooves 42 (flow channels) from through holes 46a and 46c formed in the covering member 46, and the plating catalyst is then sucked up from the liquid accumulating groove (recess 44) via a through hole 46b and returned to the plating catalyst tank 48. The plating catalyst is circulated in the flow channels, thereby depositing the plating catalyst inside the grooves 42.

The grooves 42 formed in the substrate 40 are extremely narrow, as shown in FIGS. 7A and 7B, and hence when it is attempted to flow the liquid (plating catalyst) through same, then the pressure loss is extremely high. It is possible to reduce the pressure loss by using the recess 44 as the liquid accumulator which spans across the plurality of grooves 42, as in the present embodiment.

Furthermore, if bubbles occur and if these bubbles accumulate in the flow channels when it is sought to flow the liquid (plating catalyst) into the flow channels (grooves 42), then plating will not be deposited in the regions where the bubbles are present, and hence wiring disconnections will arise. In a case of this kind, by providing a liquid accumulator, it is possible to collect together the bubbles into the liquid accumulator, and to remove the bubbles. Therefore, disconnections can be prevented in the formed electrical wires.

Furthermore, when the liquid (plating catalyst) is circulated through the flow channels formed by covering the grooves created in the substrate, if the interior of the flow channels is reduced to a vacuum state and the plating catalyst is then flowed through the flow channels and filled into same, then the plating catalyst can be introduced and deposited inside the grooves in a more efficient manner.

Next, a sixth embodiment of the present invention is described.

In the present embodiment, if the substrate surface is curved rather than being flat, and has a certain curvature, then the conducting layers are formed following the curvature of the substrate surface.

FIGS. 12A and 12B show a substrate in the present embodiment. FIG. 12A is a plan diagram, and FIG. 12B is a cross-sectional diagram along line 12B-12B in FIG. 12A. As shown in FIG. 12A, the planar shape of the substrate 52 in the present embodiment is similar to that in FIG. 7A, and a plurality of grooves 54 are formed extending in four directions from a recess 56 provided in the central portion of the substrate 52.

However, in the present embodiment, as shown in FIG. 12B, the surface of the substrate 52 on which the grooves 54 and the recess 56 are formed has a curved shape which projects in the upward direction.

FIGS. 13A and 13B show a situation where a plating catalyst is filled into the substrate 52 in the present embodiment.

For example, as shown in FIG. 13A, the surface of the covering member 58 having a curvature matching the curvature of the surface of the substrate 52 is placed in close contact with the substrate 52, a plating catalyst is sucked in from a plating catalyst tank 60 by means of a pump 62, and the plating catalyst is filled into the flow channels (grooves 54) from the through holes 58a and 58c formed in the covering member 58. The plating catalyst which has flowed into the flow channels returns to the plating catalyst tank 60 via a through hole 58b in the covering member 58, from the central recess 56. In this way, by driving the pump 62, the plating catalyst is circulated and plating catalyst is deposited inside the flow channels (grooves 54).

Furthermore, as shown in FIG. 13B, it is also possible to reverse the direction of circulation of the plating catalyst, and to introduce the plating catalyst into the recess 56 from the central through hole 58b, in such a manner that it flows from the recess 56 into the peripheral flow channels (grooves 54).

In this way, according to the present embodiment, even if the substrate surface is curved, rather than flat, it is still possible to form conducting layers on this surface.

Moreover, as shown in FIG. 14A, flow channels 65 are formed by placing a covering member 66 which follows the curved shape of a substrate 64, in close contact with a curved substrate 64 having a surface with an arbitrary curvature, and by introducing a metal catalyst 68 into the flow channels 65, it is possible to form conducting layers having the arbitrary curvature.

Furthermore, as shown in FIG. 14B, flow channels 65 are formed by placing a covering member 66 matching the shape of step-shaped flow channels 65, in close contact with step-shaped flow channels 65 which combine perpendicularly arranged flat surfaces. By introducing the plating catalyst 68 into the flow channels 65, it is possible to form conducting layers which bend in the stepped shape.

Next, a seventh embodiment of the present invention is described.

In the present embodiment, grooves are formed on both surfaces of the substrate, through holes which connect the grooves on both surfaces are formed in the substrate, and conducting layers are formed on both surfaces of the substrate.

FIGS. 15A, 15B and 15C show a substrate according to the present embodiment. FIG. 15A is a plan diagram, and FIG. 15B is a cross-sectional diagram along line 15B-15B in FIG. 15A, and FIG. 15C is a bottom face diagram.

As shown in FIG. 15A, the planar shape of the substrate 70 of the present embodiment is similar to that of FIG. 7A, having a plurality of grooves 72 formed extending in four directions from a recess 74 provided in the central portion of the substrate 52. In the substrate 70 of the present embodiment, a through hole 76 is formed in the center of the recess 74.

Furthermore, as shown by the cross-sectional diagram in FIG. 15B, the substrate 70 according to the present embodiment also has a groove 78 formed in the rear surface thereof, and the two grooves 72 and 78 are connected together by means of the through hole 76. As shown by the bottom face diagram in FIG. 15C, the groove 78 in the rear surface is formed so as to extend in one direction from the through hole 76.

FIG. 16A shows a state where plating catalyst is filled into the grooves 72 (flow channels) in the substrate 70 of this kind. In the substrate 70 according to the present embodiment, the grooves 72 and 78 are formed on both surfaces of the substrate 70, and covering members 80 and 82 are placed respectively in close contact the surfaces of the substrate 70. The covering member 80 placed in close contact with the front surface of the substrate 70 has through holes 80a and 80b connected to the groove 72 in the surface of the substrate 70, and the covering member 82 placed in close contact with the rear surface of the substrate 70 has a through hole 82a connected to the groove 78 in the rear surface of the substrate 70.

A pump 86 is connected to a plating catalyst tank 84, the pump 86 is driven, plating catalyst is sucked up from the plating catalyst tank 84, and the plating catalyst flows into the groove 72 in the surface of the substrate 70 from the through holes 80a and 80b of the covering member 80 on the surface of the substrate 70. The plating catalyst injected into the groove 72 flows from the groove 72 into the recess 74, flows from the through hole 76 in the center of the substrate 70 into the groove 78 in the rear surface of the substrate 70, and then flows out from the through hole 82a of the covering member 82 placed in close contact with the rear surface side of the substrate 70, in such a manner that it returns to the plating catalyst tank 84.

Thereby, the plating catalyst is circulated through the grooves 72 and 78 in both the front surface side and the rear surface side of the substrate 70, and hence the plating catalyst can be deposited in both of the grooves 72 and 78.

Accordingly, as shown in FIG. 16B, it is possible to form conducting layers 88 respectively on both surfaces of the substrate 70. In this way, according to the present embodiment, it is easy to form wires on both surfaces of the substrate.

Next, an eighth embodiment of the present invention is described.

In the present embodiment, when an integrated wiring board is formed to have ejection devices which eject liquid and conducting layers which are electrically connected to the drive elements of the ejection devices and a switching IC, then the conducting layers are formed by means of the above-described method of forming conducting layers (method of manufacturing a wiring board) according to the present invention.

FIG. 17 is a cross-sectional diagram showing an approximate view of a liquid ejection head according to the present embodiment in which ejection devices and a wiring board having conducting layers are formed in an integrated fashion.

The liquid ejection head 150 shown in FIG. 17 is constituted by bonding together a nozzle plate 160, a cavity plate 162, a diaphragm 156 having piezoelectric elements 158 formed thereon, an intermediate plate 170 and an ink pool member 164.

Nozzles 151 for ejecting ink droplets are formed in the nozzle plate 160. Hole sections 162a corresponding to pressure chambers 152, and groove sections 162b which constitute portions of ink supply channels 153 described hereinafter, are formed in the cavity plate 162. One side of each hole section 162a (the lower side in FIG. 17) is covered by the nozzle plate 160, and the other side (the upper side in FIG. 17) is covered by the diaphragm 156, and hence the pressure chamber 152 is formed thereby.

The ink pool member 164 has a vessel-shaped structure formed so as to be open on one side, and the ink pool member 164 is bonded onto the intermediate plate 170 in such a manner that the open side thereof is orientated toward the lower side in FIG. 17. The space formed by the ink pool member 164 and the intermediate plate 170 is an ink pool (common liquid chamber) 155, which is composed so as to cover a region corresponding to the plurality of pressure chambers 152. The hole sections 170a and 156a, and the groove sections 162b, which constitute a portion of the ink supply channels 153 provided respectively for the pressure chambers 152, are formed respectively in the intermediate plate 170, the diaphragm 156 and the cavity plate 162. The ink pool 155 and the pressure chambers 152 are connected via the ink supply channels 153 constituted by these members (170a, 156a and 162b). Ink supplied from an ink tank (not illustrated) is accumulated in the ink pool 155, and is distributed and supplied from the ink pool 155 to the respective pressure chambers 152, via the ink supply channels 153.

The piezoelectric elements 158, each of which has an individual electrode (drive electrode) 157 on the upper surface thereof, are provided at positions corresponding to the pressure chambers 152, on the surface of the diaphragm 156 reverse to the side adjacent to the pressure chambers 152 (in other words, on the ink pool 155 side). The diaphragm 156 is made of a conducting member, such as stainless steel, and also serves as a common electrode for the plurality of piezoelectric elements 158. It is also possible to form a common electrode on the surface of the diaphragm 156.

Recess sections 170b corresponding to the piezoelectric elements 158 are formed in the intermediate plate 170. Thereby, a prescribed space is guaranteed in the peripheral region of each piezoelectric element 158, and therefore it is possible to achieve the print head 150 having good ejection characteristics, without impeding the displacement of the piezoelectric elements 158.

The intermediate plate (wiring board) 170 is composed so as to be broader than the diaphragm 156 or the ink pool member 164. A drive circuit 172 constituted by a switch IC, for example, is provided on the front surface side (ink pool 155 side) of an extension section 170c (of the intermediate plate 170) which projects from the side face of the head.

Electrical wires (internal wires) 174 which are patterned in a prescribed shape are provided on the intermediate plate 170. In the embodiment shown in FIG. 17, each electrical wire 174 is constituted by a horizontal section 174a formed horizontally along the front surface side (ink pool 155 side) of the intermediate plate 170, from the position where the drive circuit 172 is disposed, and a vertical section 174b which passes vertically through the intermediate plate 170 from one end of the horizontal section 174a. One end of the electrical wire 174 is connected electrically to the drive circuit 172, and the other end thereof is connected electrically to the individual electrode 157 of the piezoelectric element 158 via an electrical connecting section 176. An insulating and protective film (not shown) made of resin, or the like, is formed on the portion of the surface of the intermediate plate 170 which makes contact with the ink inside the ink pool 155.

In the present embodiment, in the liquid ejection head 150 having the composition described above, an ejection device structure which principally comprises the nozzle plate 160, the cavity plate 162, and the diaphragm 156 having the piezoelectric elements 158 formed thereon, is unified with the intermediate plate 170 which forms the substrate including conducting layers that provide electrical connections between the piezoelectric elements 158 and the switching IC, and these conducting layers are formed by means of the conducting layer forming method such as that described in the respective embodiments mentioned above. Accordingly, it is readily possible to achieve high-density arrangement of electrical wires.

It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the invention is to cover all modifications, alternate constructions and equivalents falling within the spirit and scope of the invention as expressed in the appended claims.

Method of manufacturing wiring board, and liquid ejection head having wiring board

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Priority Claims (1)