Substrate assembly and liquid dispensing head

Abstract

To provide a substrate joint body that can suppress a substrate from enlarging in size while securing strength of the substrate.SOLUTION: A substrate joint body 14 comprises a first substrate 1 having a first flow path 8a and a second flow path 8b, and a second substrate 2 jointed to the first substrate 1 through an adhesive 3. The first substrate 1 further has concave parts 12 communicating with the first flow path 8a. When viewed from a direction orthogonal to the first substrate 1, the concave parts 12 are formed in a region 17 between the first flow path 8a and the second flow path 8b, from the first flow path 8a toward the second flow path 8b, where the adhesives 3 are stored in the concave parts 12.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a substrate assembly and a liquid ejection head using the substrate assembly.

Background Art

[0002] Structures obtained by microfabricating silicon or the like are widely used in the fields of MEMS and functional devices of electric machines. As an example, there is a liquid ejection head that ejects liquid. As an example of its use, there is a liquid ejection head of a liquid ejection recording system that lands ejected droplets on a recording medium to perform recording. The liquid ejection head includes a substrate provided with an energy generating element that generates energy used to eject liquid, and a discharge port that discharges ink supplied from a liquid supply port provided on the substrate.

[0003] As an example of a method for manufacturing a liquid ejection head, there is a method of forming by bonding a plurality of substrates with an adhesive. In this case, the liquid ejection head has a substrate assembly in which a plurality of substrates are bonded. The bonding of the plurality of substrates is performed by pressing the substrates against each other with an adhesive applied. Due to this pressing, the adhesive may protrude from the bonding surface and, for example, enter the flow path. When the adhesive enters the flow path, the flow path may be filled with the adhesive, which may affect the recording quality of the liquid ejection head.

[0004] Therefore, Patent Document 1 proposes a liquid ejection head that suppresses the protrusion of the adhesive into the discharge port and the flow path that occurs when bonding a plurality of substrates, and improves the reliability against ink clogging and the ejection characteristics. In this liquid ejection head, an adhesive entry region (hereinafter, referred to as an adhesive escape groove or simply an escape groove) into which the adhesive extruded by the bonding can enter is provided on the bonding surface of the plurality of substrates. Thereby, the adhesive extruded by the bonding of the substrates enters the escape groove, so that the protrusion of the adhesive into the flow path or the like is suppressed.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2001-162802 [Overview of the project] [Problems that the invention aims to solve]

[0006] Figure 7 is a schematic diagram showing a substrate joint 14 according to a comparative example of the present invention. Figure 7(a) is a plan view of the first substrate 1, showing the side that is joined to the second substrate 2. Figure 7(b) is a cross-sectional view of the H-H' section of Figure 7(a). Figure 7(c) is a plan view of the second substrate 2, showing the side opposite to the side that is joined to the first substrate 1. Figure 7(d) is a cross-sectional view of the I-I' section of Figure 7(c). Figure 7(e) is a cross-sectional view of the substrate joint 14 formed by joining the first substrate 1 and the second substrate 2 shown in Figures 7(b) and (d).

[0007] As shown in Figure 7(a), a relief groove 13 is formed between the first channel 8a and the second channel 8b formed in the first substrate 1. This relief groove 13 can hold the adhesive that has squeezed out from the joining surface due to the pressure applied when joining the first substrate 1 and the second substrate 2, thereby preventing the adhesive from flowing into the first channel 8a and the second channel 8b.

[0008] Since the relief groove 13 is formed by excavating the substrate, the strength of the substrate decreases around the relief groove 13. Therefore, as shown in Figure 7, when the relief groove 13 is formed, the strength of the first substrate 1 decreases along the extension direction (Y direction) of the relief groove 13. One way to avoid this is to increase the distance in the X direction between the first flow channel 8a and the relief groove 13, and the distance in the X direction between the second flow channel 8b and the relief groove 13. Increasing the distance in the X direction between the first flow channel 8a or the second flow channel 8b and the relief groove 13 expands the area around the relief groove 13 where the substrate is not excavated, thus improving the strength of the substrate. However, if the distance between each flow channel and the relief groove 13 is increased, the first substrate 1 will become larger in the X direction, which may result in an increase in the size of the first substrate 1.

[0009] Therefore, in view of the above problems, the present invention aims to provide a substrate bond that can ensure the strength of the substrate while suppressing an increase in the size of the substrate, in a substrate in which a relief groove for the adhesive is formed. [Means for solving the problem]

[0010] To solve the above problems, the present invention provides a substrate assembly comprising: a first substrate having a first channel and a second channel formed adjacent to the first channel, and having a region that separates the first channel and the second channel; and a second substrate having a plurality of channels opening in a flat surface corresponding to the first channel and the second channel, respectively, and being joined to the bonding surface of the region of the first substrate via an adhesive, wherein the region further has a recess that communicates with the first channel and the bonding surface, The recess communicates only with the first flow path, and The recess is formed in the region between the first flow channel and the second flow channel, extending from the first flow channel to the second flow channel, and the adhesive is contained in the recess. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a substrate bond that can suppress the increase in size of the substrate while ensuring the strength of the substrate, even in a substrate in which a relief groove for the adhesive is formed. [Brief explanation of the drawing]

[0012] [Figure 1] A perspective view showing the liquid dispensing head. [Figure 2] A schematic diagram showing the first substrate and the second substrate. [Figure 3] A schematic diagram showing the first substrate and the second substrate in the second embodiment. [Figure 4] A schematic diagram showing the first substrate in another embodiment. [Figure 5] A schematic diagram showing the first substrate in another embodiment. [Figure 6]A schematic diagram showing the first substrate in another embodiment. [Figure 7] This is a schematic diagram illustrating a conventional example. [Modes for carrying out the invention]

[0013] (First Embodiment) Figure 1 is a schematic diagram showing an example of the configuration of a liquid discharge head 15 in a first embodiment of the present invention. In Figure 1, the first substrate 1 and the second substrate 2 are joined together via an adhesive 3. Figure 1(a) is a top view of the liquid discharge head 15. Figure 1(b) is a top view of the joining surface side of the second substrate 2. Figure 1(c) is a cross-sectional view of the A-A' section in Figures 1(a) and (b). In Figure 1(c), the surface of the first substrate 1 has an energy generating element 5, particularly an electrothermal conversion element or piezoelectric element for discharging liquid, and may also include wiring (not shown) for driving the discharge energy generating element. The energy generating element 5 is formed on the first substrate 1 so as to correspond to the position of the discharge port 4. A discharge port forming member 6 and an electrode 7 are formed on the first substrate 1.

[0014] The liquid passes through the first channel 8a formed in the second substrate 2 and the first substrate 1, receives discharge energy from the energy generating element 5, and is discharged from the discharge port 4. The liquid that is not discharged from the discharge port 4 is recovered from the second channel 8b. Therefore, the first channel 8a functions as a supply channel for supplying liquid to the discharge port, and the second channel 8b functions as a recovery channel for recovering liquid from the discharge port. The second channel 8b is a channel formed adjacent to the first channel 8a.

[0015] Silicon is preferred as the material for the first and second substrates, but other materials such as silicon carbide, silicon nitride, various types of glass such as quartz glass and borosilicate glass, various ceramics such as alumina and gallium arsenide, and resins may also be used.

[0016] As a method for forming the first flow path 8a and the second flow path 8b penetrating the substrate, dry etching, wet etching, laser processing, etc. can be mentioned. Further, in order to adjust the height in the cross-sectional direction of the flow path, the member can also be thinned by back grinding or polishing by CMP.

[0017] As the adhesive 3, a material with high adhesion to the substrate is preferably used. Further, a material with less mixing of bubbles and the like and high coating property is preferable, and a low-viscosity material that is easy to reduce the thickness of the adhesive 3 is preferable. The material of the adhesive 3 preferably includes any resin selected from the group consisting of epoxy resin, acrylic resin, silicone resin, benzocyclobutene resin, polyamide resin, polyimide resin, and urethane resin.

[0018] As the curing method of the adhesive 3, a thermosetting method and an ultraviolet delayed curing method can be mentioned. In addition, when any of the substrates has ultraviolet transmittance, an ultraviolet curing method can also be used. The joining of the first substrate 1 and the second substrate 2 is performed by heating the substrate to a predetermined temperature in a joining apparatus and then applying pressure for a predetermined time and pressure. These joining parameters are appropriately set according to the adhesive material. Further, it is preferable to join in a vacuum in order to suppress the mixing of bubbles into the joining portion. In addition, after joining, it is preferable to further heat the substrate assembly to sufficiently promote curing. The step of forming the discharge port forming member 6 on the first substrate 1 may be before or after the substrate joining.

[0019] FIG. 2(a) is a plan view of the joining surface which is the surface on the opposite side of the discharge port 4 of the first substrate 1. FIG. 2(b) is a cross-sectional view taken along the line B-B' of FIG. 2(a). FIG. 2(c) is a cross-sectional view of the cross-section taken along the line C-C' of FIG. 2(a). FIG. 2(d) is a plan view of the surface on the opposite side of the joining surface of the second substrate 2. FIG. 2(e) is a cross-sectional view of the cross-section taken along the line D-D' of FIG. 2(d). FIG. 2(f) is an enlarged view within the dotted line of FIG. 2(a). FIG. 2(g) is a cross-sectional view of the cross-section taken along the line B-B' of FIG. 2(a) after the first substrate 1 and the second substrate 2 are joined via the adhesive 3. FIG. 2(h) is a cross-sectional view of the cross-section taken along the line C-C' of FIG. 2(a) after the first substrate 1 and the second substrate 2 are joined via the adhesive 3.

[0020] In the present invention, when viewed from a direction orthogonal to the first substrate (when viewing the plan view shown in FIG. 2(a)), a recess (adhesive escape groove) 12 is formed extending from the first flow path 8a toward the second flow path 8b. The recess 12 functions as an adhesive escape groove. The region where the recess 12 is formed is the region 17 between the first flow path 8a and the second flow path 8b. With such a configuration, a region 16 where no recess 12 is formed exists between the first flow path 8a and the second flow path 8b. Since no recess is formed in the region 16, the rigidity of the region 16 is high, and as a result, the necessary strength of the first substrate 1 can be ensured by the portion of the region 16. Therefore, it is not necessary to increase the size of the substrate to ensure strength, and according to the present invention, the strength of the substrate can be ensured while suppressing an increase in the size of the substrate.

[0021] A general escape groove as shown in FIG. 7 is not in communication with the flow paths (the first flow path 8a, the second flow path 8b) and is formed independently. In this case, if the substrate is heated with bubbles in the adhesive in the escape groove, the bubbles in the adhesive may expand, which may reduce the adhesive reliability. On the other hand, according to the present invention, by adopting a configuration in which the recess is partially in communication with the flow paths (the first flow path 8a, the second flow path 8b), even if bubbles enter the adhesive, the bubbles can escape into the flow paths. Thereby, a decrease in adhesive reliability can also be suppressed.

[0022] Before joining the first substrate 1 and the second substrate 2, the first channel 8a and the second channel 8b are in communication with each other via the recess 12. However, when liquid flows through the first channel 8a and the second channel 8b, it is preferable to prevent the liquid from flowing from the first channel 8a through the recess 12 to the second channel 8b. If liquid were to flow from the first channel 8a through the recess 12 to the second channel 8b, problems may occur, for example, due to a flow rate different from the pre-expected flow rate. Therefore, after joining the first substrate 1 and the second substrate 2, it is preferable that the first channel 8a and the second channel 8b are not in communication. For this reason, in this embodiment, as shown in Figure 2(h), it is preferable that the recess 12 be filled with adhesive after joining the substrates. This makes the first channel 8a and the second channel 8b independent of each other.

[0023] The recesses 12 are located within the region 17 between the first channel 8a and the second channel 8b, and are formed extending from the first channel 8a to the second channel 8b. Their location and number are not restricted. An appropriate number of recesses should be placed so that excess adhesive does not flow into the first channel 8a and the second channel 8b.

[0024] The recesses 12 may be machined simultaneously with the first flow path 8a and the second flow path 8b, or they may be machined separately. The number of recesses 12 is not limited. It is preferable to adjust the number of recesses 12 appropriately, taking into account the amount of adhesive 3 used for bonding the substrates.

[0025] (Second embodiment) A second embodiment will now be described. However, the same reference numerals are used for parts that are the same as in the first embodiment, and their descriptions are omitted. Figure 3(a) is a plan view of the bonding surface, which is the side of the first substrate 1 opposite to the discharge port 4. Figure 3(b) is a cross-sectional view of Figure 3(a) along the line E-E'. Figure 3(c) is a cross-sectional view of Figure 3(a) along the line F-F'. Figure 3(d) is a plan view of the second substrate 2 opposite to the bonding surface. Figure 3(e) is a cross-sectional view of Figure 3(d) along the line G-G'. Figure 3(f) is an enlarged view of the area within the dotted line in Figure 3(a). Figure 3(g) is a cross-sectional view of Figure 3(a) along the line E-E' after the first substrate 1 and the second substrate 2 have been bonded via the adhesive 3. Figure 3(h) is a cross-sectional view of Figure 3(a) along the line F-F' after the first substrate 1 and the second substrate 2 have been bonded via the adhesive 3.

[0026] This embodiment is characterized in that the recess 12 communicates with only one of the flow channels (the first flow channel 8a in the figure). In the first embodiment, the recess 12 communicated with both the first flow channel 8a and the second flow channel 8b. Therefore, in order to make the first flow channel 8a and the second flow channel 8b independent flow channels, it was necessary to seal the recess 12 with adhesive. However, in this embodiment, since the recess 12 communicates with only the first flow channel 8a, the first flow channel 8a and the second flow channel 8b are formed independently from the beginning. Therefore, it is not necessary to seal the recess 12 with adhesive 3, which leads to an improvement in yield.

[0027] As described above, in the first embodiment, it was necessary to seal the recess 12 with adhesive 3 in order to keep the first channel 8a and the second channel 8b independent of each other. Therefore, the depth of the recess 12 had to be shallow so that it could be easily filled with adhesive 3. Here, the depth of the recess 12 refers to the depth from the surface (main surface) 18 (Figure 3(c)) on which the adhesive of the first substrate 1 is applied. On the other hand, in this embodiment, since the first channel 8a and the second channel 8b are already independent, it is not necessary to seal the recess 12 with adhesive. Therefore, the recess 12 can be formed to a greater depth.

[0028] The deeper the recess 12, the larger the volume of adhesive 3 it can hold, allowing it to accommodate more excess adhesive. However, if the recess 12 is made too deep, the strength of the substrate may decrease. Therefore, the depth of the recess 12 is preferably 0.5 to 0.9 times the thickness (length in the Z direction) of the first substrate 1. This allows for a larger capacity to hold adhesive 3 while suppressing a decrease in the strength of the substrate.

[0029] (Other embodiments) Other embodiments will be described. Descriptions of parts similar to those described above will be omitted. Figures 4 to 6 are diagrams corresponding to Figure 2(f), showing a configuration in which a recess is also formed in the second channel 8b. The recess formed in the second channel 8 (the second recess) is denoted as recess 12'. Figure 4 shows an example in which the recess 12 formed in the first channel 8a and the recess 12' formed in the second channel 8b are formed symmetrically. In Figure 4, the recess 12 and recess 12' are symmetrical with respect to the center line of region 17 as the axis of symmetry. The symmetrical formation of recess 12 and recess 12' prevents excess adhesive from being concentrated in certain areas of the recess. That is, the excess adhesive can be distributed uniformly. Uniform distribution of the excess adhesive allows for a more uniform thickness of the substrate bonded body 14 after bonding, leading to improved manufacturing accuracy.

[0030] Figure 5(a) shows a configuration in which recesses 12 and 12' are formed beyond the central position (center line) of region 17. Figure 5(b) is a modified example of Figure 5(a). By forming recesses 12 and 12' as shown in Figure 5, when viewed from the Y-axis direction, there is a portion where recess 12, which communicates with the first flow path 8a, and recess 12', which communicates with the second flow path 8b, partially overlap. As a result, even if excess adhesive flows in the Y-axis direction when the first substrate 1 and the second substrate 2 are joined, the overlapping portion of the two recesses 12 and 12' can suppress the flow of adhesive in the Y-axis direction.

[0031] Figure 6(a) shows a form in which the recess 12 has a tapered shape. That is, the width of the recess decreases as it moves away from the flow path. Figure 6(b) is a modified example of Figure 6(a). By forming a recess 12 with this shape, excess adhesive from the bonding process can be easily moved towards the tip of the recess 12 by capillary action. This allows the excess adhesive to be contained at a position further away from the flow path, and further suppresses the leakage of adhesive into the flow path. [Examples]

[0032] (Example 1) A first substrate 1 is prepared, on which an energy generating element 5 made of TaSiN used for ejecting droplets, an electrical circuit (not shown) for driving the energy generating element 5, and an electrical connection part (not shown) that is electrically connected to an electrical connection substrate are formed. A silicon substrate was used as the substrate and was thinned to a substrate thickness of 625 μm using a grinding device.

[0033] A through-hole to form the first channel 8a, a through-hole to form the second channel 8b, and a recess 12 are formed in the first substrate 1. The dimensions of the through-hole are 150 μm × 20 mm rectangles, and the distance between the through-holes is 100 μm. The dimensions of the recess are 10 μm × 40 μm, and the distance between the recesses is 20 μm. Using this patterned positive resist as a mask, the half-shape of the first channel 8a is formed using the Bosch process. Etching is performed for a predetermined time so that the depth of the first channel 8a becomes 450 μm. At this time, the maximum depth from the bonding surface was 315 μm.

[0034] Next, a recess 12 was formed by creating a 50 μm hole on the surface side of the first substrate, in the same manner as when the half-shape of the first channel 8a was formed. A second substrate having a channel corresponding to the first substrate 1 was prepared. Next, a substrate for adhesive transfer was prepared, and a benzocyclobutene solution was spin-coated as the adhesive to a thickness of 3 μm. A PET film was used as the transfer substrate. After coating, a bake treatment was performed at 100°C for 5 minutes to evaporate the solvent. The adhesive formed on the transfer substrate was brought into contact with the bonding surface of the first substrate 1 while applying heat, thereby transferring the adhesive to the first substrate 1.

[0035] Next, the first substrate 1 and the second substrate 2 were aligned using a bonding alignment device and bonded by heating in a vacuum. The bonding was performed at a vacuum of 100 Pa or less and a temperature of 150°C. After bonding was complete and the substrates had cooled, they were removed from the device and heat-treated in a nitrogen atmosphere oven at 250°C for 1 hour to cure the adhesive.

[0036] Next, a negative-type photosensitive resin dissolved in PGMEA solvent was spin-coated onto a PET film, dried in an oven at 100°C to form a dry film, and then transferred to the energy generation element formation surface of the first substrate 1, and the PET film was peeled off. After the dry film was formed, exposure and PEB were performed to create a latent image state in order to form the channel to be formed on the substrate assembly 14. Subsequently, dry films were stacked in the same manner, and the discharge port 4 was exposed and PEB was performed to develop the liquid channel and discharge port together, thereby creating a liquid discharge head. [Explanation of symbols]

[0037] 1. First substrate 2. Second substrate 3. Adhesive 8a First channel 8b Second channel 12 recesses 14. Substrate assembly

Claims

1. A first substrate having a first channel and a second channel formed adjacent to the first channel, and having a region that separates the first channel and the second channel, A second substrate having a plurality of channels opening on a flat surface corresponding to the first channel and the second channel, respectively, and being bonded to the bonding surface of the region of the first substrate via an adhesive, In a substrate bond having, The region further has a recess that communicates with the first flow path and the joint surface, The recess communicates only with the first flow path, and The recess is formed in the region between the first flow path and the second flow path, extending from the first flow path toward the second flow path. A substrate bonded body characterized in that the adhesive is contained in the recess.

2. A first substrate having a first channel and a second channel formed adjacent to the first channel, and having a region that separates the first channel and the second channel, A second substrate having a plurality of channels opening on a flat surface corresponding to the first channel and the second channel, respectively, and being bonded to the bonding surface of the region of the first substrate via an adhesive, In a substrate bond having, The region further has a recess that communicates with the first flow path and the joint surface, The recess is formed in the region between the first flow path and the second flow path, extending from the first flow path toward the second flow path. The first substrate further has a second recess that communicates with the second flow path, The second recess is formed in the region between the first flow path and the second flow path, extending from the second flow path toward the first flow path. A substrate bonded body characterized in that the adhesive is contained in the aforementioned recess and the second recess.

3. The substrate bond according to claim 2, wherein the recess and the second recess are formed symmetrically with respect to the center line of the region between the first flow path and the second flow path as the axis of symmetry.

4. The substrate bond according to claim 2 or 3, wherein the recess and the second recess are formed beyond the center line of the region between the first flow path and the second flow path.

5. The substrate bond according to any one of claims 1 to 4, wherein the width of the recess decreases toward the second flow path.

6. The substrate bond according to claims 2 to 4, wherein the width of the second recess decreases toward the first flow path.

7. A nozzle for dispensing liquid, A substrate bond according to any one of claims 1 to 6, In a liquid dispensing head having, The first flow path is a supply flow path which supplies liquid to the discharge port, The liquid discharge head is characterized in that the second flow path is a recovery flow path for recovering liquid that was not discharged from the discharge port.

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