JP2005146367A - Method for selectively performing plating on sintered ceramic, and method for forming electrode of ink jet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformly perform plating without causing defective plating deposition attributable to residual resist when plating is selectively performed by applying photoresist onto a sintered ceramic and performing patterning by the exposure phenomenon. <P>SOLUTION: After coating a surface to be plated of sintered ceramic with the photoresist, the photoresist is exposed and developed, and thus the sintered ceramic of a portion required to be plated is exposed and the sintered ceramic of a portion unnecessary for plating is covered by the photoresist, then the surface of the sintered ceramic is etched with acid etching liquid in a range of the depth of ≥ 1/10 time and ≤ 2 times the average particle size of the sintered ceramic. After plating catalyst is imparted on the surface of the sintered ceramic after the etching, the plating is performed with plating liquid containing at least Ni. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for selectively forming a plating on a sintered ceramic and an electrode forming method for an ink jet head, and more specifically, in forming a plating selectively on a sintered ceramic using a photosensitive resist. The present invention relates to a method for forming plating satisfactorily without the occurrence of poor deposition due to residual resist.

  The ink jet head generates a pressure change in the ink chamber, applies pressure to the ink in the ink chamber, and ejects the ink from the nozzle to land on the recording medium. Various means have conventionally been proposed as means for generating a pressure change in the ink chamber, and one of them is an electromechanical conversion action made of a sintered ceramic as an actuator for generating a pressure change in the ink chamber. There is one formed of a piezoelectric material showing

  As a piezoelectric material made of such a sintered ceramic, PZT (lead zirconate titanate) is well known, and a material obtained by polarizing this PZT is used. For example, when polarized PZT is used as a material for the side wall of the ink chamber and a voltage is applied at a right angle to the polarization direction, a shearing deformation is caused by a piezoelectric sliding effect to generate a pressure change in the ink chamber.

  In an ink jet head using an actuator made of such a sintered ceramic, it is necessary to directly form an electrode for applying a voltage on the surface of the sintered ceramic, and conventionally an electrode is formed by a vapor deposition method or a plating method. In particular, the plating method is superior to the vapor deposition method because of its excellent cost performance and productivity.

  When forming an electrode by a plating method, it is effective to form an electrode on a portion having no conductivity by electroless plating. In that case, it is necessary to provide a place where electrode formation is not required and a place where electrode formation is not required, and several methods have been proposed.

Among them, the method with good workability and high productivity is a method in which a photosensitive resist is used for patterning by photomask exposure / development, and plating is selectively formed on a necessary portion (patent) References 1-3).
Japanese Patent Laid-Open No. 5-147215 Japanese Patent No. 2919425 JP-A-8-267768

  In the process of using the photosensitive resist on the sintered ceramic to form the plating on the necessary part, the part where the resist is left is not plated, and the part where the resist is removed by development It is necessary to form a uniform plating. Therefore, the resist is required to have a property of suppressing plating deposition.

  However, when a photosensitive resist is applied onto the sintered ceramic and patterning is performed by exposure and development, even if plating is performed thereafter, plating is not uniformly formed, and plating deposition defects may occur. As a result of intensive studies by the present inventors on the cause, even if a photosensitive resist is applied on the sintered ceramic and patterned by exposure and development, the surface shape of the sintered ceramic has an effect, as shown in FIG. In addition, a slight resist residue r exists in the gaps between the sintered ceramic particles a and is not sufficiently removed. Therefore, even in the portion where the resist should have been removed, the effect of suppressing plating deposition due to the residual resist is exerted. It was found that plating deposition defects occurred due to the influence.

  Therefore, an object of the present invention is to generate plating deposition defects due to residual resist when selectively forming a plating by applying a photosensitive resist on a sintered ceramic and performing patterning by exposure and development. And a plating forming method capable of uniformly forming a plating.

  Another object of the present invention is to apply a photosensitive resist on a sintered ceramic constituting an ink jet head and perform patterning by exposure and development to form a residual resist when selectively forming electrodes by plating. It is an object of the present invention to provide an electrode forming method for an ink jet head capable of uniformly forming a plating without causing a defective plating deposition.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

  The invention according to claim 1 is a method of selectively forming a plating on a sintered ceramic, wherein a photosensitive resist is applied to a plating formation surface of the sintered ceramic, and then exposure / development of the photosensitive resist is performed. The exposed portion of the sintered ceramic that requires plating formation is exposed, the portion of the sintered ceramic that does not require plating formation is covered with the photosensitive resist, and the surface of the sintered ceramic is treated with an acidic etching solution. Then, etching is performed in a depth range of 1/10 to 2 times the average particle diameter of the sintered ceramic, and a plating catalyst is applied to the sintered ceramic surface after the etching, followed by plating containing at least Ni In this method, the plating is selectively formed on the sintered ceramic.

  The invention according to claim 2 is the method for selectively forming the plating on the sintered ceramic according to claim 1, wherein the plating is NiB plating or NiP plating.

  The invention according to claim 3 is an electrode forming method of an ink jet head in which an electrode is formed by plating on a sintered ceramic constituting the ink jet head, and a photosensitive resist is applied to the electrode forming surface of the sintered ceramic. By exposing and developing the photosensitive resist, the portion of the sintered ceramic that requires electrode formation is exposed, and the portion of the sintered ceramic that does not require electrode formation is covered with the photosensitive resist. Etching is performed on the surface of the sintered ceramic with an acidic etching solution within a depth range of 1/10 to 2 times the average particle diameter of the sintered ceramic, and a plating catalyst is applied to the surface of the sintered ceramic after the etching. After forming the electrode, the electrode is formed by plating containing at least Ni. It is.

  The invention according to claim 4 is the electrode forming method for an ink jet head according to claim 3, wherein the plating is NiB plating or NiP plating.

  Embodiments of the present invention will be described below.

  In the present invention, the sintered ceramic means a powdered metal oxide, sulfide or the like heated to a melting point or lower or a partial melting point to form a strong bonded body. For example, it is prepared using powders such as various metal oxides such as alumina, silica, and titania, silicon nitride, boron nitride, and silicon carbide. Particularly, as a sintered ceramic as a piezoelectric material used as an actuator constituting an inkjet head, ceramics such as PZT (lead zirconate titanate) and PLZT (lead lanthanum zirconate titanate), mainly PbOx, ZrOx, It is preferable that the mixed microcrystal of TiOx contains a trace amount of metal oxide known as a softening agent or hardening agent, for example, an oxide such as Nb, Zn, Mg, Sn, Ni, La, or Cr. Among them, PZT can be preferably used as an actuator for an ink jet head because it has a high packing density, a large piezoelectric constant, and good workability.

  When the sintered ceramic is used as an actuator constituting such an ink jet head, the average particle diameter is preferably 1 to 8 μm. If it is smaller than 1 μm, sufficient sensitivity cannot be obtained. On the other hand, if it is larger than 8 μm, the variation in machining quality becomes large, which is not preferable.

  Therefore, the case where electrodes are formed by plating on an actuator of an inkjet head made of sintered ceramic will be described with reference to the drawings.

  FIGS. 1-6 is explanatory drawing explaining the method of forming an electrode by plating to the actuator of an inkjet head.

  In FIG. 1, reference numeral 1 denotes an actuator of an ink jet head. Here, the thin PZT plate 1a formed by sintering PZT powder and the thick PZT plate 1b are respectively polarized and bonded with an adhesive such as an epoxy adhesive so that the polarization directions are opposite to each other. The laminate is composed of

  Thus, a photosensitive resist is applied to the upper surface of the thin PZT plate 1a of the actuator 1 on which the PZT plates 1a and 1b are laminated, and a resist film 2 is formed.

  In general, a photosensitive resist contains an alkali-soluble resin, a quinonediazide compound, a plating deposition-inhibiting component, and the like. As the alkali-soluble resin, a novolak resin, an acetone-pyroganol resin, a polyhydroxystyrene resin, an acrylic resin, or the like is used. In particular, in the present invention, an etching process is performed using an acidic etchant described later in the subsequent process. Therefore, those using novolak resin are preferable, and specifically, a positive resist containing 30% or more of novolak resin using a quinonediazide compound as a photosensitive material is preferable. Examples of such a photosensitive resist include OFPR800, P-LA100, P-HA100, and N-CA500 manufactured by Tokyo Ohka Kogyo Co., Ltd.

  The required characteristics of the photosensitive resist are required to have resistance to the plating solution and the treatment solution before plating, and in addition, the characteristics to hinder plating deposition on the resist are required. A resist having the above composition and having these characteristics is suitable for the present invention. In the plating film formation in the present invention, the formation of an abnormal plating film on the photosensitive resist is improved by obtaining high selectivity between the plating forming part and the non-forming part, and an appropriate photosensitive resist and Become.

  The dry film thickness of the resist film 2 with this photosensitive resist is preferably 1 to 10 μm. If it is thinner than 1 μm, the coating may be insufficient, and if it is thicker than 10 μm, developability after exposure deteriorates, which is not preferable. More preferably, the thickness is 2 to 6 μm.

  Next, as shown in FIG. 2, a photomask 3 formed so as to distinguish a portion not forming an electrode, that is, a portion not forming a plating, is placed on the upper surface of the photosensitive resist 2. The photomask 3 is a positive type photomask in which a mask portion 32 is formed by patterning a transparent quartz plate 31 by vapor deposition of chromium. The photomask 3 is exposed by ultraviolet irradiation and developed by being immersed in a developer. As a result, as shown in FIG. 3, the uncovered portion covered by the mask portion 32 of the photomask 3 disappears during development and the surface of the actuator 1 is exposed, and the resist film 2 remains in the exposed portion. To do. The portions where the resist film 2 disappears during the development become the electrode forming portions 4 respectively.

  Next, as shown in FIG. 4, the actuator 1 is provided with the same number of grooves as the electrode forming portion 4 with a depth from the resist film 2 forming surface to the middle portion of the thick PZT plate 1 b using a dicing saw 5. By grinding, a plurality of parallel channels 11 are juxtaposed. At this time, each channel 11 is formed by grinding a groove from the end opposite to each electrode forming portion 4 on the surface of the actuator 1 to each electrode forming portion 4. As a result, as shown in FIG. 5, only the surface of the actuator 1 except for the inside of each channel 11 and each of the electrode forming portions 4 is covered with the resist film 2. In the present embodiment, the four electrode forming portions 4 are formed in the actuator 1 and the four channels 11 are ground. However, the number of the channels 11 is not limited.

  Thereafter, the actuator 1 is immersed in an acidic etching solution to etch the surface of the actuator 1.

  Examples of the liquid used for etching include hydrofluoric acid, acidic ammonium fluoride solution, borofluoric acid, borofluoric acid metal salt, phosphoric acid, nitric acid, sulfuric acid, hydrochloric acid, chromic acid and the like, and these may be used alone. However, a plurality of these may be combined. Among these, a combination of acidic ammonium fluoride and nitric acid and a borofluoric acid are preferable.

  By immersing in such an acidic etching solution, the surface of the sintered ceramic exposed to the electrode forming portion 4 is scraped. In the present invention, the etching with the acidic etching solution is a process that forms the actuator 1. The depth is in the range of 1/10 to 2 times the average particle size of the sintered ceramic. FIG. 7A shows a state where etching is performed at a depth of 1/10 times the average particle diameter of the sintered ceramic, and FIG. 7B shows a depth twice as large as the average particle diameter of the sintered ceramic. The state when etching is performed is shown. In the figure, a represents ceramic particles, r represents residual resist, and the hatched portion represents an etched region.

  Although it is known that the surface is roughened by etching for the purpose of cleaning the substrate and adhesion of the plating film, in this case, etching of less than 1/10 of the average particle diameter is sufficient. The problem of residual resist was not considered at all. However, as in the present invention, when patterning using a resist is performed, the remaining of the resist can be prevented by etching in a depth range of 1/10 to 2 times the average particle diameter. In other words, as shown in the figure, by etching in an acid etching solution within a depth range of 1/10 times or more and 2 times or less of the average particle diameter of the sintered ceramic, it cannot be completely removed by exposure / development processing. Residual resist r between the sintered ceramic particles is removed.

  When the etching depth is less than 1/10 times, the residual resist r between the sintered ceramic particles a cannot be removed by etching, and the residual resist r causes plating deposition failure. Moreover, when it becomes deeper than twice, it will be in the situation which etches under a resist coating part, an electrode width will become larger than a design value, the short circuit defect at the time of FPC (flexible printed circuit board) joining will increase, In some cases, plating deposition defects may occur due to contamination of the surrounding area due to partial peeling. More preferably, the depth is 1/5 or more and 1 or less.

  The depth of etching is controlled by appropriately adjusting the immersion time in the acidic etching solution.

  After the etching process, a plating catalyst is applied to the surface of the actuator 1. The plating catalyst is performed as a pretreatment for efficiently depositing plating on the surface of the sintered ceramic serving as the electrode forming portion 4. For example, in the case of electroless plating, palladium (Pd) serving as a catalyst nucleus is adsorbed. Those are preferably used.

  After application of the plating catalyst, plating is formed on the electrode forming portion 4. That is, the actuator 1 is immersed in a plating solution, and a plating film is deposited on the surface of the actuator 1.

  The plating metal used here contains at least nickel (Ni). At least Ni is contained because of its relatively high corrosion resistance, good solderability, electrode bonding properties such as wire bonding and ACF (anisotropic conductive film) bonding, and good film adhesion to the substrate. Can be cited as the reason. Further, there is an advantage that multilayer plating such as gold (Au) plating on the plating containing Ni is easy.

  As the type of Ni plating, NiB plating containing boron (B) and NiP plating containing phosphorus (P) are preferable, and NiB plating is particularly preferable from the viewpoint of low electrical resistance. NiB plating and NiP plating may be laminated and used.

  After the plating process, when the resist film 2 on the surface of the actuator 1 is peeled off, as shown in FIG. 6, a plating metal by electroless plating is deposited only on the electrode forming portion 4 where the sintered ceramic is exposed. The electrode 6 is selectively formed on the surface of 1. At this time, unnecessary plating deposited on both side surfaces, bottom surface, front and rear end surfaces of the actuator 1 may be removed by polishing.

  Thereafter, in order to create an ink jet head using such an actuator 1, as shown in FIG. 7 is bonded using an adhesive, and the nozzle plate 8 in which the nozzle holes 8a corresponding to the respective channels 11 are opened across the front end surface of the cover substrate 7 and the front end surface of the actuator 1 is used. And glue. Further, a manifold 9 constituting an ink supply chamber for supplying ink into each channel 11 is adhered to the upper surface of the cover substrate 7 using an adhesive, and a drive circuit is connected to each electrode 6 formed on the upper surface of the actuator 1. The FPC 10 in which the wiring electrically connected to the pattern is formed is bonded using ACF or the like.

  In the above embodiment, the electrode is formed on the sintered ceramic constituting the ink jet head. However, the present invention is selectively performed by exposing and developing the photosensitive resist on the sintered ceramic. The present invention can be applied to the case where plating is formed, whereby uniform plating with no precipitation failure can be formed in the plating formation portion.

  In addition, when forming electrodes by plating on a sintered ceramic substrate at a fine pitch, such as when forming an electrode of an inkjet head or forming a wiring pattern with fine electrodes on a ceramic substrate, etc. As the pitch of the electrodes becomes narrower, the plating thickness that can be formed naturally is limited in order to avoid short circuits between adjacent electrodes. For this reason, as the plating thickness becomes thinner, it becomes more susceptible to the resist remaining on the sintered ceramic that cannot be completely removed by development processing, and the occurrence of plating deposition defects is more frequently observed.

  Therefore, in the present invention, when the electrodes are formed on the sintered ceramic in this way, the pitch of each electrode is 200 μm or less, more preferably 150 μm or less. Become. This pitch is the distance between the centers of adjacent electrodes. The width of the electrode and the distance between the electrodes are ½ of that.

  Similarly, if the plating thickness is thin, it is likely to be affected by the remaining resist. Therefore, in the present invention, a thin plating with a thickness of 5 μm or less, more preferably 3 μm or less, formed on the sintered ceramic is used. When it is formed, a remarkable effect is exhibited.

Hereinafter, the effect of the present invention is illustrated by examples.
(Example 1)
By polarizing a thin PZT plate and a thick PZT plate obtained by molding and sintering PZT powder (average particle size: 2 μm) manufactured by Sumitomo Electrodevices, respectively, and applying an adhesive so that the polarization direction is opposite A stacked actuator was prepared.

<Resist processing step>
A liquid resist “OFPR800” manufactured by Tokyo Ohka Co., Ltd. was applied to the surface of the thin plate of the actuator on the PZT plate side with a spin coater so that the film thickness when dried was 4 μm ± 2 μm.

After coating, pre-bake treatment is performed at 90 ° C. for 30 minutes, a photomask is placed on the actuator so as to cover the resist surface as an electrode forming portion, and ultraviolet light of 200 mW / cm ² and 365 nm is irradiated for 1 minute through the photomask. did.

  Thereafter, the film was immersed in a developer “NMD-3” manufactured by Tokyo Ohka Kogyo Co., Ltd. for 2 minutes for development, and as shown in FIG. 3, an electrode forming portion where the resist was selectively removed was formed on the surface of the actuator. Thereafter, this actuator was post-baked at 100 ° C. for 1 hour.

<Groove formation process>
A groove serving as an electrode forming portion channel was formed by a dicing saw from the resist processing surface side of the actuator after the resist processing. Thereby, as shown in FIG. 5, only the surface of the actuator excluding the inside of each channel and each electrode forming portion is covered with the resist film. The channel width was 40 μm, the pitch was 85 μm, and 450 channels were formed in parallel.

<Etching process>
The grooved actuator was immersed in a pH 3 acidic ammonium fluoride solution (15%) while swinging. After this immersion treatment, the substrate was immersed in a nitric acid (30%) solution while swinging. Table 1 shows the etching process time, etching depth (etching amount), and the ratio to the average particle diameter.

<Catalyst application process>
After the etching process, the actuator was immersed for 30 seconds in a 4% SnCl ₂ solution (adjusted to pH 1 with HCl). After this immersion treatment, the substrate was immersed in a 0.04% solution of PdCl ₂ for 30 seconds while swinging to give a palladium catalyst as a plating catalyst to the exposed portion of the sintered ceramic of the actuator.

<Plating film formation process>
The actuator after applying the catalyst was immersed for 10 minutes in a solution in which a plating solution “Niboron 70” manufactured by Okuno Pharmaceutical Co., Ltd. was adjusted to 60 ° C. and pH 6.5, and subjected to NiB plating film formation. The thickness of the plating film at this time was 2.0 μm.

<Resist stripping process>
The actuator after plating film formation was immersed in an acetone solution, the resist on the actuator surface was dissolved and peeled off, washed, and as shown in FIG. 6, plating electrodes were formed in each channel and on the actuator surface connected thereto. An actuator was created.

(Example 2)
Example 1 was the same as Example 1 except that the etching processing time was changed as shown in Table 1.

(Example 3)
In the etching process, the treatment solution was replaced with acidic ammonium fluoride + nitric acid, and borofluoric acid (1%) was used. Except that the immersion treatment was performed while the actuator was swung for the time shown in Table 1, the same as in Example 1. did.

Example 4
In the etching process, the treatment solution was replaced with acidic ammonium fluoride + nitric acid, and borofluoric acid (5%) was used. did.

(Comparative Examples 1 and 2)
Example 1 was the same as Example 1 except that the etching processing time was changed as shown in Table 1.

(Evaluation)
Visual observation and continuity test were performed on the plated electrode formed on the surface of the actuator, and the following criteria were evaluated.
(Double-circle): The plating deposition defect was not recognized but the surface was formed uniformly.
A: No plating deposition failure was observed.
(Triangle | delta): Although plating deposit defect has generate | occur | produced partially, it was able to conduct | electrically_connect.
X: Plating deposition failure occurred and conduction was not possible.

  The results are shown in Table 1.

  In Comparative Example 2, neither plating deposition failure nor conduction failure occurred, but a short circuit between adjacent electrodes occurred due to the occurrence of thickening of the plating width.

Explanatory drawing explaining the method of forming an electrode by plating on the actuator of an inkjet head Explanatory drawing explaining the method of forming an electrode by plating on the actuator of an inkjet head Explanatory drawing explaining the method of forming an electrode by plating on the actuator of an inkjet head Explanatory drawing explaining the method of forming an electrode by plating on the actuator of an inkjet head Explanatory drawing explaining the method of forming an electrode by plating on the actuator of an inkjet head Explanatory drawing explaining the method of forming an electrode by plating on the actuator of an inkjet head (A) is a figure which shows the mode at the time of etching at the depth of 1/10 times the average particle diameter of a sintered ceramic, (b) is an etching at the depth of 2 times the average particle diameter of a sintered ceramic. Showing the situation when Exploded perspective view showing structure of inkjet head The figure which shows the appearance of the sintered ceramic after the photosensitive resist is removed

Explanation of symbols

1: Actuator 1a: Thin PZT plate 1b: Thick PZT plate 11: Channel 2: Resist film 3: Photomask 4: Electrode forming part 5: Dicing saw 6: Electrode 7: Cover substrate 8: Nozzle plate 8a: Nozzle Hole 9: Manifold 10: FPC

Claims (4)

  A method of selectively forming a plating on a sintered ceramic, wherein a photosensitive resist is applied to a surface on which the sintered ceramic is formed, and then the photosensitive resist is exposed and developed to thereby form a plating. The required portion of the sintered ceramic is exposed, the portion of the sintered ceramic that does not require plating is covered with the photosensitive resist, and the surface of the sintered ceramic is acid-etched with an average of the sintered ceramic. Etching is performed in a depth range of 1/10 to 2 times the particle diameter, and a plating catalyst is applied to the surface of the sintered ceramic after the etching, and then plating is formed by plating containing at least Ni. A method of selectively forming plating on a sintered ceramic.   2. The method for selectively forming a plating on a sintered ceramic according to claim 1, wherein the plating is NiB plating or NiP plating.   An electrode forming method for an ink jet head in which an electrode is formed by plating on a sintered ceramic constituting an ink jet head, wherein a photosensitive resist is applied to an electrode forming surface of the sintered ceramic, and then the exposure of the photosensitive resist is performed. By developing, exposed portions of the sintered ceramic that require electrode formation are exposed, and the portions of the sintered ceramic that do not require electrode formation are covered with the photosensitive resist, and the surface of the sintered ceramic is subjected to acidic etching. Etching at a depth in the range of 1/10 to 2 times the average particle diameter of the sintered ceramic with a liquid, and after applying a plating catalyst to the sintered ceramic surface after the etching, at least Ni is included An electrode forming method for an ink jet head, wherein the electrode is formed by plating.   4. The method for forming an electrode of an ink jet head according to claim 3, wherein the plating is NiB plating or NiP plating.

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