Method for manufacturing liquid ejection head, liquid ejection head

Abstract

To provide a method for manufacturing a liquid discharge head and a liquid discharge head which can solve problems that an adhesive protrudes from a joined surface and an adhesive flows in a flow channel, and can further suppress protrusion of an adhesive from a joined surface.SOLUTION: A recess 151 and a plurality of projections 121 are formed in at least any one of a first surface 4 of a first substrate 131 and a second surface 5 of a second substrate 132, wherein at least any one among a plurality of projection intervals obtained from the plurality of projections 121 is at most dc [mm] represented by the following expression: dc=0.17H0.75T0.40 P-0.15. Young's moduli of the first substrate 131 and the second substrate 132 are 100 GPa or more, T [μm] is thickness of the substrate, H [μm] is a height of the projection 121, and P [MPa] is a pressure in joining.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a liquid ejection head, and a liquid ejection head. [Background technology]

[0002] A recording device that performs recording by discharging liquid onto a recording medium such as paper includes a liquid discharge head that discharges liquid from a discharge port. As an example, the liquid discharge head is formed by stacking a plurality of substrates for different purposes. An adhesive is used to bond the stacked substrates together.

[0003] When bonding the substrates, if a large amount of adhesive is used, or if the substrates are significantly bent when pressed for bonding, the adhesive may overflow from the bonding surface and flow into the flow paths, etc. If the adhesive flows into the flow paths, the flow paths will be filled with adhesive to that extent, affecting the flow of the liquid.

[0004] In response to this problem, Patent Document 1 proposes a liquid ejection head in which a recess (also called an escape groove) is formed around the flow path, and a protrusion is formed near the recess. By forming a recess, the adhesive that protrudes from the joining surface can be retained by the recess, and the adhesive can be prevented from flowing into the flow path, etc. Furthermore, by forming a protrusion around the recess, the protrusion acts as a tension rod, and even if the substrates are pressed when they are joined, the substrates can be prevented from bending significantly. This makes it possible to prevent the adhesive from protruding due to the bending of the substrates when they are joined. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5933146 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, convex portions are formed along concave portions, but convex portions are not formed in areas where concave portions are not formed. Therefore, the substrates in the areas where convex portions are not formed are significantly deflected by pressure during bonding. As a result, the adhesive may overflow from the bonding surface and flow into the flow path, etc.

[0007] In view of the above-mentioned problems, an object of the present invention is to provide a liquid ejection head and a manufacturing method thereof that can further suppress the adhesive from squeezing out from the bonding surfaces. [Means for solving the problem]

[0008] In order to solve the above problem, the present invention provides a method for manufacturing a liquid ejection head comprising a first substrate having a first surface and a second substrate having a second surface, the first surface and the second surface being bonded together with an adhesive, the method comprising: a preparation step of preparing the first substrate and the second substrate; a coating step of coating at least one of the first surface and the second surface with an adhesive; and a bonding step of applying pressure to the first substrate and the second substrate to bond the first surface and the second surface, wherein a recess is formed on at least one of the first surface of the first substrate and the second surface of the second substrate in the preparation step, a plurality of protrusions are formed on at least one of the first surface of the first substrate and the second surface of the second substrate in the preparation step, and when the arrangement distance between adjacent protrusions among the plurality of protrusions is defined as a protrusion spacing, at least one of the plurality of protrusion spacings obtained from the plurality of protrusions is equal to or less than dc [mm] represented by the following formula: dc=0.17H 0.75 T 0.40 P -0.15

[0009] Here, the Young's modulus of the first substrate and the second substrate is 100 GPa or more, T [μm] is the thickness of the thinner of the first substrate and the second substrate, H [μm] is the height from the first surface or the second surface on which the convex portion is formed, and P [MPa] is the pressure in the bonding process. Effect of the Invention

[0010] According to the present invention, it is possible to provide a liquid ejection head and a manufacturing method thereof that can further suppress the adhesive from squeezing out from the bonding surfaces. [Brief description of the drawings]

[0011] [Figure 1] FIG. [Diagram 2] 3A to 3C are schematic diagrams illustrating manufacturing steps of the liquid ejection head. [Diagram 3] 3 is a flowchart of each step shown in FIG. 2. [Figure 4] FIG. [Diagram 5] 1 is a graph showing the relationship between the height H of a protrusion [μm] and the distance dc [mm]. [Figure 6] A graph showing the relationship between substrate thickness T [μm] and distance dc [mm]. [Figure 7] A graph showing the relationship between press pressure P [PMa] and distance dc [mm]. [Figure 8] FIG. 2 is a plan view showing a state where a first substrate and a second substrate are bonded together. [Figure 9] FIG. 11 is a diagram showing another example of the arrangement of protrusions. [Figure 10] FIG. 13 is a graph showing the relationship between the pressing pressure P [PMa] and the strength of the protrusions. [Figure 11] 4A to 4C are diagrams showing examples of the shape of a flow path opening portion and the shape of a convex portion. [Figure 12] FIG. 11 is a schematic view showing a convex portion according to a second embodiment. [Figure 13] FIG. 11 is a schematic view showing a convex portion according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (First embodiment) (Liquid ejection head) FIG. 1 is a cross-sectional view of a liquid ejection head 1 in this embodiment. The liquid ejection head 1 is mainly composed of an ejection port forming member 119, a flow path forming member 118, a first substrate 131, and a second substrate 132. The ejection port forming member 119 has an ejection port 101 for ejecting liquid (ink). The flow path forming member 118 has a flow path 102 for flowing liquid to the ejection port 101. The first substrate 131 has a pressure generating element 107 for generating pressure for ejecting liquid from the ejection port 101, a first through hole 2 communicating with the flow path 102, and a convex portion 121, which will be described in detail later. The second substrate 132 has a second through hole 3 communicating with the first through hole 2 and a concave portion 151. The first substrate 131 and the second substrate 132 are joined by an adhesive 123.

[0013] (Method of manufacturing liquid ejection head) FIG. 2 is a schematic diagram of each manufacturing process of the liquid ejection head 1 of this embodiment. FIG. 3 is a flowchart of each process shown in FIG. 2. First, a first substrate 131 having a circuit (not shown) and a pressure generating element 107 formed on its surface is prepared (preparation process) (FIG. 2(A) and S1 in FIG. 3). The material of the first substrate 131 is preferably silicon or a material having an elastic modulus equal to or greater than that of silicon. This is to prevent the substrate from being deformed in the bonding process (FIG. 2(F)) described later. Examples of materials having an elastic modulus greater than that of silicon include silicon carbide, silicon nitride, SUS, and various ceramics (alumina, cermet, boron carbide, zirconia, mullite, gallium nitride, and aluminum nitride). The same is true for the material of the second substrate 132 (FIG. 2(D)), and silicon or a material having an elastic modulus equal to or greater than that of silicon is preferable.

[0014] Next, the first substrate 131 is cut from the first surface 4 of the first substrate 131 so that the first substrate 131 has a desired thickness, while forming the first through-hole 2 (FIG. 2(b), S2 in FIG. 3). Examples of processing methods for thinning the first substrate 131 to a desired thickness include grinding and wet etching using a chemical solution such as fluoro-nitric acid. Examples of methods for forming the first through-hole 2 include dry etching, wet etching, laser, and sandblasting. The first surface 4 refers to the surface opposite to the surface on which the pressure-generating element 107 is formed.

[0015] Next, a plurality of convex portions 121 are formed on the first surface 4 of the first substrate 131 (FIG. 2(c) and S3 in FIG. 3). The convex portions 121 can be formed by forming a mask on the first surface 4 of the first substrate 131 on which the first through-holes 2 have been processed, and then etching the mask. The mask can be formed by laminating a resist processed into a dry film, or by forming a resist by a spray coating method. Note that a mask for etching the convex portions 121 may be formed on the first surface 4 of the first substrate 131 before the first through-holes 2 are formed. A material that is highly thermally stable and stable against the processing process of the first through-holes 2 is suitable for the mask. Examples of such materials include organic resins that are insoluble in resists and stripping solutions, and inorganic films such as silicon oxide films and silicon nitride films formed by vapor phase growth. After etching the first substrate 131 through the mask to process the convex portions 121, the mask is removed by a method such as stripping solution, oxygen plasma ashing, or dry etching. At this time, in order to remove the etching deposit adhering to the protrusion 121, a remover for etching deposits or the like may be used.

[0016] Another method for forming the protrusions 121 is to pattern a film formed by vapor phase growth. Examples of materials include SiO, SiN, SiC, SiCN, SiOC, Al, Ti, W, and Au. In particular, a film to which carbon is added has improved resistance to ink, so it is preferable to use a material containing carbon. Furthermore, other methods for forming the protrusions 121 include patterning a photosensitive resin such as a dry film, or patterning an organic film such as a permanent resist film. This method makes it easy to form high protrusions.

[0017] Next, a second substrate 132 having a recess 151 formed therein is prepared (FIG. 2(d) and S4 in FIG. 3). The recess 151 functions as an adhesive escape groove that can store excess adhesive 123. Next, a second through hole 3 is formed in the second substrate 132 in a similar manner to the first through hole 2 in the first substrate 131. Then, adhesive 123 is applied onto the second surface 5 (application step) (FIG. 2(e) and S5 in FIG. 3). The second surface 5 is the surface that is to be joined to the first surface 4.

[0018] Next, the first substrate 131 and the second substrate 132 are bonded (bonding process) (FIG. 2(f), S6 in FIG. 3). The first substrate 131 and the second substrate 132 are aligned by an alignment device, and temporarily fixed by clamping the substrates with a clamping mechanism or the like. Then, the temporarily fixed first substrate 131 and second substrate 132 are transferred to a bonding device. The first substrate 131 and the second substrate 132 are heated to a predetermined temperature in the bonding device, and then bonded by pressing them with a predetermined time and pressure. These bonding parameters are appropriately set according to the adhesive material. Also, bonding in a vacuum is preferable in order to prevent air bubbles from being mixed into the bonded portion.

[0019] Finally, a flow path forming member 118 and a discharge port forming member 119 are formed on the first substrate 131, and the liquid discharge head 1 is completed (FIG. 2(g), S7 in FIG. 3). For example, a dry film resist is laminated on the first substrate 131, and then exposed and developed to form the flow path forming member 118 and the discharge port forming member 119.

[0020] In the above description, an example in which a plurality of convex portions 121 are formed on the first substrate 131 has been described, but the present invention is not limited to this. That is, the convex portion 121 may be formed on the second substrate 132. Furthermore, the convex portion 121 may be formed on both the first substrate 131 and the second substrate 132. In addition, an example in which the concave portion 151 is formed on the second substrate 132 has been described, but the present invention is not limited to this. That is, the concave portion 151 may be formed on the first substrate 131. Furthermore, the concave portion 151 may be formed on both the first substrate 131 and the second substrate 132. In summary, it is sufficient that the convex portion 121 and the concave portion 151 are formed on the bonding surfaces (the first surface 4 and the second surface 5) of the two substrates. In addition, the adhesive 123 is applied to the second substrate 132, but the adhesive 123 may be applied to the first substrate 131.

[0021] (Arrangement of protrusions) FIG. 4 is an enlarged cross-sectional view of the vicinity of the convex portion 121 when the first substrate 131 and the second substrate 132 are bonded. Note that FIG. 4 is illustrated upside down from the diagrams shown in FIG. 1 and FIG. 2, and the concave portion 151 is omitted. FIG. 4(a) is a diagram illustrating a configuration as a comparative example. FIG. 4(b) is a diagram illustrating this embodiment. When the convex portion 121 formed on the first substrate 131 contacts the second substrate 132, the convex portion 121 functions as a pillar for suppressing deformation of the two substrates. This makes it possible to suppress the first substrate 131 and the second substrate 132 from being excessively deformed by the pressure applied when the first substrate 131 and the second substrate 132 are bonded. The convex portion 121 supports the bonding surfaces of the two substrates, and the distance (gap) between the first substrate 131 and the second substrate 132 can be kept approximately constant. This makes it possible to prevent the adhesive 123 from spilling out from the bonding surface due to the narrowing of the gap between the first substrate 131 and the second substrate 132, and further to prevent the adhesive from flowing into the flow path, etc. Here, the bonding surface refers to the first surface 4 of the first substrate 131 and the second surface 5 of the second substrate 132.

[0022] However, as shown in FIG. 4(a), if the arrangement interval (protrusion interval) d between adjacent protrusions is large, there is nothing nearby to support the portion of the substrate where the protrusion 121 is not formed. For this reason, when the substrate is pressed in the bonding process, either the first substrate 131 or the second substrate 132 may be significantly deformed. At this time, the substrate with the smaller thickness has a larger deformation amount, which is the second substrate 132 in FIG. 4(a). When the substrate is significantly deformed, the gap between the substrates becomes smaller, the adhesive 123 is crushed, and the amount of the adhesive 123 protruding from the bonding surface becomes large. The protrusion interval d is the distance between the centers of two adjacent protrusions.

[0023] Therefore, in this embodiment, as shown in FIG. 4(b), the convex interval d is set to the distance dc or less (how to obtain the distance dc will be described later). By setting the convex interval d to the distance dc or less, the convex portions 121 can be formed at an appropriate density. This can prevent the substrate from being significantly deformed. As a result, the adhesive can be further prevented from overflowing from the bonding surface. When the convex interval d is greater than the distance dc, the substrate is significantly deformed as shown in FIG. 4(a). The substrate is significantly deformed when the substrates are deformed to the extent that they almost come into contact with each other (the distance between the substrates is 1 μm or less). In other words, even if the substrates are pressed during the bonding process, by setting the convex interval d to the distance dc or less, it is possible to prevent the first substrate 131 and the second substrate 132 from being deformed to the extent that they come into contact with each other (the distance between the substrates is 1 μm or less). Since a plurality of convex portions 121 are formed on the substrate, a plurality of convex intervals d can be extracted. However, in the present invention, it is sufficient that at least one of the plurality of extracted convex intervals d is equal to or less than the distance dc. However, from the viewpoint of further suppressing deformation of the substrate, it is more preferable that all of the extracted convex-portion intervals d are equal to or less than the distance dc.

[0024] (Spacing between convex parts) In order to derive the above-mentioned formula for calculating the distance dc, the inventors examined the dependency of the distance dc on the height of the convex portion, the thickness of the substrate, and the pressing pressure during bonding.

[0025] An 8-inch silicon substrate with a thickness of 725 μm and a polished single side was used as the first substrate 131, and an 8-inch silicon substrate with a thickness of 625 μm and a polished double side was used as the second substrate 132. Then, a plurality of cylinders with a diameter of 300 μm were formed as the convex portion 121 on the first surface 4 of the first substrate 131. Here, the convex portion height H [μm] refers to the height from the first surface 4 to the apex of the convex portion. Benzocyclobutene resin was formed on the second substrate 132 to a thickness of 0.5 μm, and the first substrate 131 and the second substrate 132 were bonded together at a press pressure of 0.0636 MPa. Then, the bonded substrate was observed with an infrared microscope or an ultrasonic microscope to confirm whether the distance (gap) between the two substrates was 1 μm or less. The convex portion height H [μm] was changed stepwise and the above process was repeated to investigate the relationship between the convex portion height H [μm] and the distance dc [mm].

[0026] Figure 5 shows the results of the verification (distance d c The plot in Fig. 5 shows the experimental results. The solid line in Fig. 5 shows the dependence of the distance dc [mm] on the power function H α The calculation results of the model assuming a dependence on (α=0.75) are shown. When the height H [μm] of the convex part increases, d c According to the study by the inventors, as shown in FIG. c [mm] is the power function of H [μm] H α It was found that the experimental results can be explained by a model assuming a dependence of (α=0.75) (it can be seen that the plot and the solid line match).

[0027] Next, the thickness T [μm] of the second substrate 132 was changed to examine the relationship between the substrate thickness T [μm] and the distance dc [mm]. A silicon substrate with a thickness not exceeding that of the first substrate 131, that is, a thickness of 150 to 625 μm, was prepared as the second substrate 132. The height H of the protrusions formed on the first substrate 131 was prepared to be 2 to 9.5 μm. The other conditions were the same as those in FIG. 5.

[0028] Figure 6 shows the results of the verification (distance d c The plot in Fig. 6 shows the experimental results. The solid line in Fig. 6 shows the power function T of the distance dc [mm]. β 6 shows the calculation results of a model that assumes a dependency on the distance dc (β=0.4). In the present invention, the substrate thickness T [μm] refers to the average thickness of the thinner of the two substrates (first substrate 131 and second substrate 132). The relationship between the substrate thickness T [μm] and the distance dc [mm] described below is derived by taking the average thickness of the thinner substrate as T [μm]. Under the conditions of FIG. 6, since the second substrate 132 is thinner, the thickness of the second substrate 132 is adopted as the substrate thickness T [μm]. As shown in FIG. 6, the larger the substrate thickness T [μm], the shorter the distance d c According to the study by the inventors, as shown in FIG. c [mm] is a power function of T [μm] β It was found that the experimental results can be explained by a model assuming a dependence of (β=0.4) (it can be seen that the plot and the solid line match).

[0029] Finally, the relationship between the pressing pressure P [MPa] and the distance dc [mm] was investigated by changing the pressing pressure P [MPa] during bonding. The convex height H [μm] was 4.5 μm and 9.5 μm. The other conditions were the same as in Figure 5.

[0030] Figure 7 shows the results of the verification (pressure P [PMa] vs. distance d cThe plot in FIG. 7 shows the experimental results. The solid line in FIG. 7 shows the power function P of the distance dc [mm]. -γ As shown in Fig. 7, the larger the pressure P during bonding, the greater the distance d c According to the inventors' study, as shown in FIG. c [mm] is the power function of P [MPa] -γ It was found that the experimental results can be explained by a model assuming a dependence of (γ=0.15) (it can be seen that the plot and the solid line match).

[0031] From the above verification results, the inventors have c It was found that [mm] can be expressed by the following formula (1). d c =C*H α *t β *P -γ (1)

[0032] where H is the height of the protrusion [μm], T [μm] is the thickness [μm] of the thinner of the two substrates to be joined, and P [MPa] is the pressure during joining. The other parameters are constants: C = 0.1694, α = 0.75, β = 0.4, and γ = 0.15. Therefore, equation (1) can be expressed as the following equation (2). dc=0.17H 0.75 T 0.40 P -0.15 (2)

[0033] To be precise, the higher the elastic modulus of the substrate, the smaller the distance dc. Therefore, the distance dc also depends on the elastic modulus of the substrate. The above equations (1) and (2) are valid when the Young's modulus of the substrate is 100 G or more.

[0034] When bonding substrates coated with adhesive, the bonding process does not proceed spontaneously, as in plasma activated bonding, for example. Therefore, it is necessary to press the adhesive with a certain amount of pressure. Otherwise, voids may occur on the bonding surface, or the adhesive may not conform to the bonding surface and may peel off. To prevent voids from occurring during bonding and to bond the two sets of substrates closely, it is necessary to press with a pressure P of at least 0.001 MPa.

[0035] In addition, the pressure P must be kept below 100 MPa, because if pressing is performed with excessive pressure, the substrate on which the protrusions and depressions are formed will crack due to the pressure.

[0036] Therefore, the preferred range of the pressure P in the present invention is 0.001 MPa or more and 100 MPa or less. At that time, the preferred range of dc can be expressed by the following formula (3) using the above formula (2). 0.0017H^0.75T^0.40 ≦ dc ≦170H^0.75T^0.40 (3) From the viewpoint of further suppressing deformation of the substrate, as well as suppressing bonding voids and preventing cracks in the substrate and protrusions, it is more preferable that all of the extracted protrusion intervals d be within the range of formula (3).

[0037] (Positional relationship between flow path and convex portion) The positional relationship between the opening of the flow path on the bonding surface and the convex portion 121 will be described. Fig. 8 is a plan view of the first substrate and the second substrate bonded together. Note that the concave portion 151 is omitted from the illustration. The thin white rectangle indicates the second through hole 3, the dashed line indicates the first through hole 2, the dashed line indicates the outer edge of the substrate (the outer edge of the liquid ejection head) 141, and the rectangular shape indicates the convex portion 121. The distance dc is indicated by an arrow.

[0038] 8(A) shows an example in which all of the convex portions 121 are formed between the flow paths (second through holes) 3. Distances X1, X2, and X3, which are the convex portion intervals, are designed to be dc or less. By forming the convex portions 121 between the flow paths, it is possible to suppress deformation of the substrate, particularly around the flow paths, and to suppress the adhesive from flowing into the flow paths.

[0039] FIG. 8(B) shows an example in which a convex portion 121 is formed between the outer edge 141 of the substrate and the flow path 3. The distances X4, X5, X6, and X7, which are the convex portion intervals d, are all designed to be equal to or less than dc. Electrodes, drive circuits, and dicing lines are installed in the area between the outer edge 141 and the flow path 3. These areas have no or few recesses (relief grooves), so there is no escape route for the adhesive. Therefore, if the adhesive in this area is crushed, the amount of adhesive that flows to the flow path increases, and the impact is serious. Therefore, as shown in FIG. 8(b), forming a convex portion 121 between the outer edge 141 and the flow path has a significant effect on suppressing the flow of the adhesive to the flow path.

[0040] 8(C), all of the flow path openings 3 are included in region A (closed curve A) formed when connecting the protrusions 121 close to the outer edge 141 of the substrate. Furthermore, in region A, distances X8, X9, X10, X11, X12, and X13, which are the protrusion intervals d, are all less than dc. By forming the protrusions 121 in this manner, it is possible to significantly suppress deformation of the first substrate 131 and the second substrate 132 at least in region A, and further suppress the flow of the adhesive from the bonding surface.

[0041] Next, from another perspective, the positional relationship between the convex portion and the flow path opening will be explained. During the manufacturing process, foreign matter can get on the wafer due to various factors. If foreign matter occurs on the bonding surface (top surface) of the convex portion, it is likely to become a void with the foreign matter as a nucleus. When a void occurs, ink will leak through that area, adversely affecting the ejection performance.

[0042] Considering that foreign matter occurring on the joint surface (upper surface) of the convex portion becomes a void, it is preferable that the convex portion 121 is separated from the flow path opening. It is also preferable that the convex portion 121 is separated from the recesses other than the flow path. This is because if a foreign matter void occurs on the joint surface (upper surface) of the convex portion while the flow path opening is in contact with the convex portion 121, the recess and the void will undesirably communicate with each other. As a result, the recess will not be sealed with the adhesive, and the function that the recess should perform will be impaired.

[0043] In the case where the recess has a function other than a flow path, such as storing and packaging a functional element, various gases may enter the recess when the recess communicates with the void. Or ink may enter the recess. As a result, the functional element may malfunction. In addition, in the case where the recess functions as various alignment marks (such as a bonding misalignment measurement mark or a bonding alignment mark), the void may change the visible shape of the alignment mark, making it impossible to recognize.

[0044] Furthermore, convex parts are formed in the entire area of ​​the wafer, including the invalid chip area, and the distance between the centers of the adjacent convex parts in the wafer is d c The distance between the centers of the nearest adjacent protrusions is d c By eliminating the need for any location where a protrusion can be placed at a distance greater than the gap between the first and second substrates, the gap between the first and second substrates can be maintained over the entire area of ​​the wafer, which further prevents the adhesive from flowing into the flow paths inside the chip.

[0045] Therefore, it is preferable that the protrusion 121 is not in contact with the opening of the flow path or the opening of the recess other than the flow path, and more preferably, is as far away from these openings as possible. In particular, the vicinity of the periphery of the chip is a preferable location for arranging the protrusion 121, since generally, there are no openings of the recess and the vicinity is the position furthest from the openings of the recess.

[0046] For example, the chip cutting line (such as a dicing line) where a cutting tool (such as a dicing blade or laser) comes into contact to separate a wafer into chip shapes is usually located at the outermost periphery of the chip, and is therefore a preferred location for locating the convex portion 121. A preferred example is shown in Figure 9. Each chip area is separated by a chip boundary line 141 on the wafer. In each chip, the convex portion bonding surface 146 is located outside the boundary (dicing line boundary 145) between the area that is processed to separate the chips by dicing or the like (dicing line) and the area that is not processed.

[0047] An effective chip area 148 used for products is formed toward the center of the wafer at a certain distance from the wafer edge 147. As shown in Fig. 9, if convex portions 121 are formed in the dicing line area of ​​the effective chip and the convex portion interval d (shown in Fig. 7) is arranged at or below dc (shown in Fig. 7), substrate deformation in the effective chip can be suppressed and the adhesive can be prevented from being crushed.

[0048] Furthermore, as shown in Figure 9, if a convex portion 121 is formed in the dicing line area for the invalid chip area 149 that is located closer to the wafer edge 147 than the valid chip area 148, this is preferable because it prevents the adhesive from being crushed in the invalid chip area 149 and flowing into the valid chip area 148.

[0049] Furthermore, if there are protrusions 121 on the dicing lines, they may cause problems when the chip is cut, so protrusions 121 may be provided near the periphery of the chip adjacent to the dicing lines. Furthermore, they may be provided at each corner of the chip adjacent to the intersection where two sets of dicing lines intersect. In this case, the chip cutting process is not adversely affected by the protrusions 121, and gaps can be maintained across the entire chip, which is preferable.

[0050] A preferred convex shape of the present invention will now be described. A substrate with convex portions produced by the same manufacturing method as the sample examined in Figs. 5 to 7 was pressed against a bare silicon substrate without any adhesive. Pressing was performed at a sufficiently strong pressure of 0.063 MPa, and the state of the convex portions after pressing in the bonded state of the substrates was observed with an infrared microscope to check for the presence or absence of damage. The results are shown in Fig. 10.

[0051] As can be seen from Figure 10, even with the same pressure, the smaller the diameter of the protrusion, the more likely it is to break. Larger diameters are less likely to break, and no breakage has been observed for protrusions of φ100 μm or more. Since tiny structures such as protrusions are generally brittle near their edges, it is speculated that in protrusions with small diameters on the bonding surface, the effect of the edges becomes greater, causing breakage.

[0052] Therefore, it is preferable that the bonding surface shape of the protrusion is made wider to reduce the influence of the end, and it is preferable that the width of the bonding surface in both the X direction and the Y direction is made 100 μm or more. In this way, it is possible to prevent the protrusion from being destroyed by pressing.

[0053] FIG. 11 shows examples of the flow path opening shape and the convex shape. It is not preferable if the convex portion 121 surrounds the flow path opening 3 as in FIG. 11(a). The first reason is that, as described above, foreign matter voids that may occur on the convex joining surface increase the possibility of causing leakage from the flow path opening. The second reason is that the adhesive expelled by the convex portion 121 during joining flows to the flow path opening 3 and is likely to cause blockage. The adhesive portion that comes into contact with the convex joining surface is expelled during joining. If the flow path opening 3 is surrounded, the adhesive will flow toward the flow path opening 3 from all directions with nowhere to escape.

[0054] Therefore, when arranging the convex portion 121 near the flow path opening 3, it is necessary to avoid a situation in which the convex portion 121 continuously surrounds the flow path opening 3 as shown in FIG. 11(a), and by providing a discontinuous portion as shown in FIG. 11(b), the adhesive is less likely to flow toward the flow path opening 3.

[0055] 11(c), the flow of the adhesive can be further suppressed, which is more preferable if the shape and position of the protrusion 121 are set so that it is adjacent to only one side of the flow path opening 3. Adjacent here means that one of the multiple sides having the flow path opening is the shortest with respect to all parts of the protrusion.

[0056] As discussed above, in order to prevent the protrusions 121 from approaching each other due to deformation of the first substrate 131 and the second substrate 132, it is effective to reduce the distance between the protrusions, which leads to an increase in the number of protrusions. Also, in order to prevent the protrusions 121 from being broken, it is effective to increase the width of the protrusions.

[0057] On the other hand, if a foreign matter occurs in a part other than the bonding surface of the convex portion, the foreign matter can be embedded in the gap in the bonding surface between the first substrate and the second substrate, thereby suppressing the occurrence of foreign matter voids, which is one of the advantages of the present invention.

[0058] The probability of foreign matter occurring on the convex bonding surface is considered to be proportional to the ratio X of the area of ​​the entire convex bonding surface to the bonding area between first substrate 131 and second substrate 132. Therefore, it is preferable to set the number of convex portions to the minimum number necessary to maintain the gap between the substrates, and it is preferable to set the area of ​​the convex portions to the minimum area that does not break during pressing.

[0059] Designing X to be 0.5 or less is preferable because at least the probability that foreign particles will not occur on convex parts is higher than the probability that they will occur. Furthermore, assuming that the probability of foreign particles occurring follows a normal distribution, with the standard deviation being σ, if X is 0.317 or less, the probability of foreign particles occurring on convex parts can be kept outside the 1σ range, which is preferable because it greatly reduces the void occurrence rate. If X is 0.0027 or less, it can be kept outside the 3σ range, which is preferable because it allows a high level to be achieved from the perspective of quality control.

[0060] Reducing the number of protrusions is an effective way to reduce X to this range, and therefore increasing dc by increasing the height H of the protrusions in formula (1) or (2) is effective.

[0061] In addition, in the present invention, the adhesive is hardly crushed and flows into the flow path, so it is easy to make the adhesive thick. Since the adhesive can be made thick, even if the height H of the convex portion is made large, there is almost no problem that the gap between the substrates cannot be filled due to insufficient adhesive.

[0062] As the height H of the protrusions is increased, foreign matter is more likely to occur in areas without protrusions, as described above, but at the same time, the gap between the bonding surfaces increases, so even if larger foreign matter occurs, it is more likely to be buried in the adhesive. This means that even if larger foreign matter occurs, it is less likely to become a void. In this way, the present invention can simultaneously suppress the flow of the adhesive into the flow path and suppress the generation of voids caused by foreign matter.

[0063] In order to exert the effect of the convex portion, H is preferably 0.5 μm or more, but considering the increase in the distance between the convex portions as described above, a more preferable range is more than 3 μm. On the other hand, if the convex portions are too high, the amount of adhesive to fill the gap becomes enormous, and there is a concern that the subsequent processing process cannot be performed due to the increase in the warpage of the wafer caused by the increase in adhesive stress, or that the wafer may crack. Therefore, H is preferably 150 μm or less.

[0064] The thickness of the adhesive 123 is preferably at least thick enough to seal the periphery of the ink opening and prevent leakage. Also, if it is transferred at the same thickness as the convex portion height H, it is preferable because it can fill almost the entire space between the first substrate and the second substrate. However, if it is made thicker than the convex portion height, it is not preferable because excess adhesive will flow into the flow path.

[0065] In the present embodiment, an example has been shown in which convex portion 121 is formed on the bonding surface of the first substrate, and adhesive is formed on the bonding surface of the second substrate, but the present invention is not limited to this configuration, and adhesive may be formed on the first substrate side, and convex portion 121 on the second substrate side. Also, the surface to which the adhesive is transferred may be the substrate side with convex portion 121, rather than the substrate side without convex portion 121.

[0066] Second embodiment 13 shows a method for manufacturing the substrate assembly and liquid ejection head according to the second embodiment. A first substrate 131 and a second substrate 132 are manufactured using the same technique as in the first embodiment.

[0067] A first flow path 112 and a first through hole 2 are formed in the first substrate 131, and a convex portion 121 is further formed on the bonding surface. Meanwhile, a third flow path 114 is formed on the bonding surface side of the second substrate 132. At this time, a recessed escape groove 151 is also formed in addition to the third flow path 114. Thereafter, an adhesive 123 is applied to the second substrate 132 side, and the first substrate and the second substrate are bonded together.

[0068] The escape groove 151 of the second substrate 132 expels adhesive by the volume of the protrusion 121 when the protrusion 121 of the first substrate 131 is joined. The escape groove 151 has a function of preventing the expelled adhesive from flowing and overflowing into the flow path.

[0069] The clearance groove 151 does not need to be large as long as it can absorb the volume of the protrusion 121. It is preferable that the opening area is at least equal to the bonding area of ​​the protrusion 121. It is also preferable to form the clearance groove 151 on the surface where the protrusion 121 is bonded.

[0070] This is because, as a first advantage, the presence of escape groove 151 at a position opposite convex portion 121 makes it easier for adhesive 123 to enter escape groove 151 when pressed by convex portion 121. As a second advantage, the chip area is easily shrunk because escape groove opening 152 and convex portion bonding surface 155 can be overlapped. In particular, if escape groove opening 152 is accommodated within convex portion bonding surface 155, there is no need for additional space to be reserved for the escape groove.

[0071] It is necessary to make the size of the escape groove opening 152 small enough that the convex portion joining surface 155 does not fit in the escape groove opening 152. Otherwise, the convex portion 121 may fall into the escape groove 151 and may not function as a convex portion.

[0072] An example of the relative positions and shape relationship between the escape groove and the convex portion is shown in Fig. 13. If the escape groove opening 152 is included inside the convex portion bonding surface 155 as shown in Fig. 13(a), there is no need to secure additional space, which is advantageous in terms of chip shrink.

[0073] 13(b), the escape groove 151 may be divided into a plurality of grooves. In this case, the pressure that the convex bonding surface 155 receives from the second substrate can be more uniform than in the case of a single groove as in FIG. 11(a). This reduces the risk of the convex 121 being damaged by the load concentrating on a portion of the convex bonding surface 155.

[0074] 13(c), the escape groove opening 152 may protrude beyond the convex joining surface 155, and at least a part of the escape groove opening 152 may be in contact with the convex joining surface 155. This is because, when pressed by the convex portion, the adhesive flows efficiently to the escape groove opening part in contact, and the adhesive flows throughout the escape groove. Since it is sufficient that some part of the escape groove 151 is in contact with the convex portion 121, there is an advantage in that the escape groove 151 can be made larger.

[0075] The escape groove 151 of the present invention only needs to be formed locally on the bonding surface of the convex portion, so there is no need to increase the escape groove area. Therefore, there is little risk of the substrate strength decreasing. Furthermore, in the present invention, since it is preferable to form the convex portion at a position far from the flow path opening as described above, the escape groove 151 is also formed at a portion away from the flow path. (In FIG. 10(e), it is formed at a position away from the third flow path 114.) Therefore, there is little risk of a crack occurring across the third flow path 114 and the escape groove 151 due to damage to the substrate during the processing step.

[0076] The escape groove 151 may be processed simultaneously with the third flow path 114, or may be processed separately. Furthermore, the convex portion 121 and the escape groove 151 are formed independently on different substrates, and therefore can be formed easily in terms of manufacturing method. The escape groove 151 can be manufactured using the method for manufacturing the flow path described in the first embodiment. Furthermore, the adhesive is applied to the second substrate 132 side, but it may be applied to the first substrate 131 side. The same effect can be expected. The application method described in the first embodiment can also be used.

[0077] This embodiment can prevent the adhesive between the substrates from being crushed by the convex portion 121 while also preventing the adhesive expelled by the convex portion 121 from flowing, thereby further suppressing the flow of adhesive toward the flow path opening.

[0078] After bonding, the adhesive is cured in the same manner as in the first embodiment, and a discharge port forming member is formed on the bonded substrate, completing the liquid discharge head. EXAMPLES

[0079] For the first substrate, a photolithography process was used to form aluminum wiring, an interlayer insulating film made of silicon oxide thin film, a heater thin film pattern made of tantalum nitride, and contact pads for electrical connection to an external control unit on the surface (mirror surface) of an 8-inch silicon substrate (thickness: 730 μm).

[0080] A 180 μm thick ultraviolet curing tape was attached to the surface of the first substrate as a protective tape, and the first surface 4 of the first substrate was thinned to a substrate thickness of 500 μm using a grinding device. The ground surface was then polished by a CMP device to smooth it. After smoothing using a slurry mainly composed of colloidal silica and a polyurethane polishing pad in the CMP device, the polished surface was washed with a cleaning solution consisting of a mixture of 8 wt % ammonia, 8 wt % hydrogen peroxide, and 84 wt % pure water to remove the slurry.

[0081] After that, a mask for the convex portion was formed on the first surface 4 side of the first substrate. The mask for the convex portion is a mask for processing the convex portion described in the first embodiment. The material was polyamide resin, which was applied to the entire substrate by spin coating to a thickness of 2 μm, and cured by heat treatment at 250°C for 1H. Then, a novolac-based resist was applied thereon, exposed by a double-sided alignment exposure device, and developed by a developing device to pattern the resist. Dry etching was performed using plasma generated by discharging O2 gas and CF4 gas through the resist, and the mask for the convex portion was processed. After etching, the resist was removed, and the mask for the convex portion was completed.

[0082] Next, a resist mask for processing the second flow path was formed on the back side of the first substrate using the same method as above. After that, the grooves that would become the second flow path were etched. For etching, the Bosch process was used, which repeats etching with SF6 gas and deposition with CF4 gas. Etching was stopped when the average groove depth reached 300 μm. After the protective tape was removed by irradiating it with ultraviolet light, the resist and etching deposits were removed with a stripping solution whose main component was hydroxylamine.

[0083] Next, a protective tape was attached to the back side of the wafer, a resist mask was formed on the front side, and a first flow path consisting of multiple holes was processed by dry etching from the front side of the substrate. After etching, the protective tape was removed, and the resist and deposits were removed with a stripping solution.

[0084] A protective tape was again laminated on the front side of the first substrate, and a protrusion made of a convex shape was formed on the bonding surface by processing to a depth of 3 μm using the Bosch process through the mask for the protrusion formed on the back side of the substrate. After the formation of the protrusion, the mask for the protrusion was removed by ashing with oxygen plasma. The protrusion was formed in the arrangement shown in the figure.

[0085] A 300μm thick silicon substrate with mirror finish on both sides was prepared as the second substrate. A benzocyclobutene resin solution was used as an adhesive and applied to the surface of the second substrate to a thickness of 3μm. The second substrate was then baked at 100℃ for 4 minutes to volatilize the solvent in the adhesive.

[0086] Next, the first and second substrates were aligned using a bonding alignment device, and the two wafer edges were pressurized with a clamping jig to temporarily fix them. The temporarily fixed sample was transferred into the bonding device, heated to 150°C in a vacuum, and pressed and bonded with 3000N for 5 minutes, after which the sample was cooled and removed from the bonding device. The sample was then heat-treated at 250°C for 1 hour in a separate oven in a nitrogen atmosphere to harden it.

[0087] After that, a protective tape is formed on the first substrate side, and a resist mask for processing the third flow path is formed on the back side of the second substrate. The third flow path is processed using the Bosch process. After processing the third flow path, the adhesive layer exposed at the bottom is dry-etched by RF discharge of a mixed gas of CF4 and O2 to connect the second flow path and the third flow path. After removing the protective tape, the resist and etching deposits are removed with a stripping solution mainly composed of hydroxylamine.

[0088] A negative dry film made of epoxy resin was laminated on the surface of the first substrate, and the walls of the discharge port forming member were formed by exposing and developing the film. A dry film was further laminated on top of the walls, and the top plate of the discharge port forming member was formed by exposing and developing the film. The sample was heat-treated in an oven at 200°C for 1 hour to harden the discharge port forming member, and a liquid discharge head was produced. [Explanation of symbols]

[0089] 1 Liquid ejection head 4. First Side 5. The Second Side 121 Convex 123 Adhesive 131 First Substrate 132 Second Board 151 Recess

Claims

1. a first substrate having a first surface and a second substrate having a second surface; In a method for manufacturing a liquid ejection head, the first surface and the second surface are bonded to each other by an adhesive, A preparation step of preparing a first substrate and a second substrate; a coating step of coating at least one of the first surface and the second surface with an adhesive; a bonding step of applying pressure to the first substrate and the second substrate to bond the first surface and the second surface; having a recess and a plurality of protrusions are formed on at least one of the first surface of the first substrate and the second surface of the second substrate in the preparation step; A method for manufacturing a liquid ejection head, characterized in that, when the arrangement distance between adjacent convex portions among the plurality of convex portions is defined as the convex portion spacing, at least one of the multiple convex portion spacings obtained from the plurality of convex portions is equal to or less than dc [mm] represented by the following formula: dc=0.17H ０．７５ T ０．４０ P －０．１５ Here, the Young's modulus of the first substrate and the second substrate is 100 GPa or more, T [μm] is the thickness of the thinner of the first substrate and the second substrate, H [μm] is the height from the first surface or the second surface on which the convex portion is formed to the apex of the convex portion, and P [MPa] is the pressure in the bonding process.

2. The method for manufacturing a liquid ejection head according to claim 1 , wherein all of the plurality of projection intervals are equal to or smaller than dc.

3. A plurality of flow paths are formed in the first substrate and the second substrate, The method for manufacturing a liquid ejection head according to claim 1 , wherein the convex portion is formed in an area between the plurality of flow paths.

4. 4. The method for manufacturing a liquid ejection head according to claim 1, wherein a ratio of a total bonding area of ​​the plurality of projections to a bonding area between the first substrate and the second substrate is 0.5 or less.

5. 4. The method for manufacturing a liquid ejection head according to claim 1, wherein a ratio of a total bonding area of ​​the plurality of projections to a bonding area between the first substrate and the second substrate is 0.317 or less.

6. 6. The method for manufacturing a liquid ejection head according to claim 1, wherein a ratio of a total bonding area of ​​the plurality of projections to a bonding area between the first substrate and the second substrate is 0.0027 or less.

7. 6. The method for manufacturing a liquid ejection head according to claim 1, wherein at least a part of the convex portion is not in contact with an opening of the concave portion.

8. 8. The method for manufacturing a liquid ejection head according to claim 1, wherein the convex portion does not surround the periphery of the opening of the concave portion.

9. a bonding substrate of the first substrate and the second substrate having a chip region; The method for manufacturing a liquid ejection head according to claim 1 , wherein at least one of the protrusions is disposed outside a chip region with respect to an opening of the recess.

10. a bonded substrate formed by the first substrate and the second substrate has a chip region; at least a part of the protrusions is disposed outside the chip region relative to the openings of the recesses, and a closed curve A formed by lines connecting the protrusions surrounds the openings of all the recesses within the chip region; The method for manufacturing a liquid ejection head according to claim 1 , further comprising the step of: (a) forming a liquid ejection head by applying a pressure to a liquid ejection head in a direction perpendicular to the liquid ejection head; (b) forming a liquid ejection head in a direction perpendicular to the liquid ejection head;

11. A method for manufacturing a liquid ejection head as described in any one of claims 1 to 9, characterized in that the bonded substrate consisting of the first substrate and the second substrate has a plurality of chip regions, and there is no place across the plurality of chip regions where a convex portion can be placed with a distance between adjacent convex portions greater than dc.

12. a bonded substrate formed by the first substrate and the second substrate has a plurality of chip regions; a cutting area for dividing the plurality of chip areas is provided around the chip areas; The method for manufacturing a liquid ejection head according to claim 1 , wherein at least a part of the convex portion is formed on the cutting region.

13. 3. The method for manufacturing a liquid ejection head according to claim 1, wherein the width of the bonding surface of the convex portion is 100 [mu]m or more.

14. The method for manufacturing a liquid ejection head according to claim 1 , wherein the height of the convex portion is greater than 0.5 μm.

15. The method for manufacturing a liquid ejection head according to claim 1 , wherein the height of the convex portion is greater than 3 μm.

16. 14. The method for manufacturing a liquid ejection head according to claim 1, wherein the height of the convex portion is 150 [mu]m or less.

17. The method for manufacturing a liquid ejection head according to claim 1 , wherein the convex portion is formed by etching the first substrate.

18. 18. A method for manufacturing a liquid ejection head according to any one of claims 1 to 17, wherein the material of the first substrate and the second substrate is selected from silicon, silicon carbide, silicon nitride, SUS, alumina, cermet, boron carbide, zirconia, mullite, gallium nitride, and aluminum nitride.

19. 19. The method for manufacturing a liquid ejection head according to claim 1, wherein the pressure P is equal to or greater than 0.001 MPa and equal to or less than 100 MPa.

20. a first substrate having a first surface and a second substrate having a second surface; In the liquid ejection head, the first surface and the second surface are bonded together by an adhesive, a recess and a plurality of protrusions are formed on at least one of the first surface of the first substrate and the second surface of the second substrate; A liquid ejection head characterized in that, when the arrangement distance between adjacent convex portions among the plurality of convex portions is defined as the convex portion spacing, at least one of the multiple convex portion spacings obtained from the plurality of convex portions is in the range dc [mm] expressed by the following formula. 0.0017H ０．７５ T ０．４０ ≦ dc ≦170H ０．７５ T ０．４０ Here, the Young's modulus of the first substrate and the second substrate is 100 GPa or more, T [μm] is the thickness of the first substrate or the second substrate which is thinner, and H [μm] is the height from the first surface or the second surface on which the convex portion is formed to the apex of the convex portion.

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