1. Field of the Invention
The present invention relates to a method of manufacturing a thermal head.
2. Description of the Related Art
There has been conventionally known a method of manufacturing a thermal head for use in thermal printers (see, for example, Japanese Patent Application Laid-open No. 2010-94939). In the method of manufacturing a thermal head described in Japanese Patent Application Laid-open No. 2010-94939, a concave portion is formed in one surface of an upper substrate, and a support substrate is bonded onto the upper substrate so as to close the concave portion, and after that, heating resistors are formed on a rear surface of the upper substrate in a region opposed to the concave portion, to thereby manufacture a thermal head which has a cavity portion between the upper substrate and the support substrate.
In the thermal head manufactured in this way, the cavity portion functions as a heat-insulating layer of low thermal conductivity to reduce an amount of heat transferring from the heating resistors toward the support substrate side via the upper substrate, to thereby increase an amount of heat to be utilized for printing and increase heating efficiency. The heating efficiency is determined by the dimensions of the concave portion, the thickness dimension of the upper substrate between the heating resistors and the cavity portion, and the like. It is therefore required to reduce fluctuations in such dimensions.
However, in manufacturing the thermal heads, there may be fluctuations in dimensions of the concave portions in the same substrate or fluctuations in dimensions of the concave portions among the substrates. Therefore, the conventional manufacturing method has a problem that fluctuations in heating efficiency cannot be suppressed and it is difficult to manufacture a thermal head having stable quality.
The present invention has been made in view of the above-mentioned circumstances, and it is an object thereof to provide a method capable of manufacturing a thermal head having high heating efficiency and stable quality.
In order to achieve the above-mentioned object, the present invention provides the following measures.
The present invention provides a method of manufacturing a thermal head, including: forming a groove portion, which is opened in one surface of at least one of a first substrate and a second substrate to be disposed on the first substrate in a stacked state, the first substrate and the second substrate each being of a plate shape; measuring a width dimension of the groove portion formed in the forming of the groove portion; bonding the first substrate and the second substrate to each other in the stacked state so as to close an opening of the groove portion formed in the forming of the groove portion; thinning the second substrate, which is bonded onto the first substrate in the bonding, to a thickness set based on the width dimension of the groove portion measured in the measuring; and forming a heating resistor on a surface of the second substrate, which is thinned in the thinning, in a region opposed to the groove portion.
According to the present invention, the groove portion, which is formed in the groove portion forming step, is closed by bonding the first substrate and the second substrate to each other in the stacked state in the bonding step, to thereby form a stacked substrate having a cavity portion at a stacked portion between the first substrate and the second substrate. Further, the heating resistor, which is formed in the resistor forming step, is disposed so as to be opposed to the groove portion, and hence the cavity portion functions as a hollow heat-insulating layer that prevents heat from transferring toward the first substrate side from the heating resistor via the second substrate, to thereby increase heating efficiency.
In this case, the heating efficiency is determined by the dimensions of the groove portion, the thickness of the second substrate (distance from the heating resistor to the cavity portion), and the like. In the present invention, the thickness of the second substrate to be thinned in the thinning step is set based on the width dimension of the groove portion measured in the measuring step. Accordingly, fluctuations in width dimension of the groove portion can be cancelled through adjustment to the thickness of the second substrate. This reduces the occurrence of a defective, and thus a thermal head having high heating efficiency and stable quality can be manufactured.
The present invention provides a method of manufacturing a thermal head, including: forming a groove portion, which is opened in one surface of at least one of a first substrate and a second substrate to be disposed on the first substrate in a stacked state, the first substrate and the second substrate each being of a plate shape; measuring a depth dimension of the groove portion formed in the forming of the groove portion; bonding the first substrate and the second substrate to each other in the stacked state so as to close an opening of the groove portion formed in the forming of the groove portion; thinning the second substrate, which is bonded onto the first substrate in the bonding, to a thickness set based on the depth dimension of the groove portion measured in the measuring; and forming a heating resistor on a surface of the second substrate, which is thinned in the thinning, in a region opposed to the groove portion.
According to the present invention, the thickness of the second substrate to be thinned in the thinning step is set based on the depth dimension of the groove portion measured in the measuring step. Accordingly, fluctuations in depth dimension of the groove portion can be cancelled through adjustment to the thickness of the second substrate. Therefore, a thermal head having high heating efficiency and stable quality can be manufactured.
The present invention provides a method of manufacturing a thermal head, including: forming a groove portion, which is opened in one surface of at least one of a first substrate and a second substrate to be disposed on the first substrate in a stacked state, the first substrate and the second substrate each being of a plate shape; measuring a width dimension and a depth dimension of the groove portion formed in the forming of the groove portion; bonding the first substrate and the second substrate to each other in the stacked state so as to close an opening of the groove portion formed in the forming of the groove portion; thinning the second substrate, which is bonded onto the first substrate in the bonding, to a thickness set based on the width dimension and the depth dimension of the groove portion measured in the measuring; and forming a heating resistor on a surface of the second substrate, which is thinned in the thinning, in a region opposed to the groove portion.
According to the present invention, the thickness of the second substrate is set based on the width dimension and the depth dimension of the groove portion. Accordingly, fluctuations in dimensions of the groove portion can be cancelled with good accuracy through adjustment to the thickness of the second substrate. Therefore, a thermal head having high heating efficiency and high quality can be manufactured.
The present invention provides the effect that a thermal head having high heating efficiency and stable quality can be manufactured.
In the accompanying drawings:
Now, a method of manufacturing a thermal head according to an embodiment of the present invention is described below with reference to the accompanying drawings.
The method of manufacturing a thermal head according to this embodiment is for manufacturing, for example, as illustrated in
The manufacturing method of this embodiment includes, as illustrated in a flowchart of
The manufacturing method of this embodiment further includes an electrode portion forming step SA7 of forming electrode portions 17A and 17B connected to the heating resistors 15 on the surface of the upper substrate 14, a protective film forming step SA8 of forming a protective film 19 which partially covers the surface of the upper substrate 14 including the heating resistors 15 and the electrode portions 17A and 17B, and a cutting step SA9 of cutting the resultant substrate into the individual thermal heads 10.
Hereinafter, the respective steps are specifically described.
In the concave portion forming step SA1, as the support substrate 12, for example, an insulating glass substrate having a thickness approximately ranging from 300 μm to 1 mm is used. First, the large-size support substrate 12 is divided into regions for the individual thermal heads 10. For example, in
A larger width dimension and a larger depth dimension of the concave portions 21 are more effective in terms of thermal efficiency, but it is necessary to suppress the dimensions within a predetermined range in order to suppress fluctuations in quality among products. Further, if the width dimension of the concave portion 21 is excessively large, the strength of the upper substrate 14 is weakened. In addition, increasing the depth dimension of the concave portion 21 disadvantageously leads to an increase of manufacturing cost.
The concave portion 21 can be formed by performing, for example, sandblasting, dry etching, wet etching, laser machining, or drill machining on the one surface of the support substrate 12. When sandblasting is performed, the one surface of the support substrate 12 is covered with a photoresist material. Then, the photoresist material is exposed to light using a photomask of a predetermined pattern so as to be cured in part other than the region for forming the concave portion 21.
After that, the surface of the support substrate 12 is cleaned and the uncured photoresist material is removed. Thus, an etching mask (not shown) having an etching window formed in the region for forming the concave portion 21 can be obtained. In this state, sandblasting is performed on the surface of the support substrate 12 to form the concave portion 21 having a predetermined depth.
Further, when etching, such as dry etching and wet etching, is performed, similarly to the above-mentioned processing by sandblasting, the etching mask having the etching window formed in the region for forming the concave portion 21 is formed on the one surface of the support substrate 12. In this state, etching is performed on the surface of the support substrate 12 to form the concave portion 21 having a predetermined depth.
As such an etching process, for example, wet etching using a hydrofluoric acid-based etchant or the like is available, as well as dry etching such as reactive ion etching (RIE) and plasma etching. As a reference example, in a case of a single-crystal silicon support substrate, wet etching may be performed using an etchant such as a tetramethylammonium hydroxide solution, a KOH solution, or a mixed solution of hydrofluoric acid and nitric acid.
Next, in the measuring step SA2, for example, a measuring microscope, a contact type surface roughness tester, a non-contact type laser displacement meter, or the like is used to measure the width dimensions and the depth dimensions of the concave portions 21 (Step SA2). As to a single large-size support substrate 12, it is desired to measure the width dimensions and the depth dimensions of the plurality of concave portions 21 to calculate an average width dimension and an average depth dimension.
Next, in the condition setting step SA3, based on data on an average value of the width dimensions and an average value of the depth dimensions of the plurality of concave portions 21 measured in the measuring step SA2, process conditions of the upper substrate 14 are set (Step SA3).
For example, a ranking table as shown in
As shown in
Further, as shown in
Accordingly, for example, in the ranking table of the width of the concave portion 21 shown in
Further, for example, in the process conditions of the thickness of the upper substrate 14 shown in
Next, in the bonding step SA4, a glass substrate made of the same material as that of the support substrate 12 is used as the upper substrate 14. A thin glass substrate having a thickness of 100 μm or smaller is difficult to manufacture and handle, and expensive. Thus, instead of bonding an originally thin upper substrate 14 onto the support substrate 12, the upper substrate 14 which is thick enough to be easily manufactured and handled is bonded onto the support substrate 12, and then the upper substrate 14 is processed to a desired thickness in the thinning step SA5 (Step SA4).
In the bonding step SA4, first, etching masks are all removed from the surface of the support substrate 12, followed by cleaning. Then, the upper substrate 14 is laminated to the surface of the support substrate 12 so as to close all of the concave portions 21. For example, the upper substrate 14 is directly laminated to the support substrate 12 at room temperature without using an adhesive layer.
The one surface of the support substrate 12 is covered with the upper substrate 14 to close the opening of each of the concave portions 21, to thereby form a plurality of cavity portions 23 between the support substrate 12 and the upper substrate 14. In this state, the laminated support substrate 12 and upper substrate 14 are subjected to heat treatment so that the substrates are bonded to each other by thermal fusion (Step SA4). Hereinafter, the resultant substrate obtained by bonding the support substrate 12 and the upper substrate 14 to each other is referred to as a stacked substrate 13.
Next, in the thinning step SA5, based on the process conditions set in the condition setting step SA3 (see
For the etching of the upper substrate 14, various types of etching can be used as in the concave portion forming step SA1. Further, for the polishing of the upper substrate 14, for example, chemical mechanical polishing (CMP), which is used for high accuracy polishing for a semiconductor wafer and the like, can be used. Next, in the resistor forming step SA6, the plurality of heating resistors 15 are formed in each of regions of the surface of the upper substrate 14, which are opposed to each of the concave portions 21 (Step SA6). The heating resistors 15 are formed so as to individually straddle each of the cavity portions 23 in a width direction, and are arrayed at predetermined intervals in a longitudinal direction of each of the cavity portions 23.
When the heating resistors 15 are formed, there can be used a thin film forming method such as sputtering, chemical vapor deposition (CVD), or deposition. A thin film is formed from a heating resistor material such as a Ta-based material or a silicide-based material on the upper substrate 14. The thin film is shaped by lift-off, etching, or the like to form the heating resistors 15 having a desired shape.
Next, in the electrode portion forming step SA7, similarly to the resistor forming step SA6, the film formation is performed with use of an electrode material on the upper substrate 14 by using sputtering, deposition, or the like. Then, the film thus obtained is shaped by lift-off or etching, or the electrode material is screen-printed and is, for example, baked thereafter, to thereby form the electrode portions 17A and 17B (Step SA7). Examples of the electrode material which may be used include Al, Al—Si, Au, Ag, Cu, and Pt.
The electrode portions 17A and 17B include: individual electrodes 17A connected to one ends of the respective heating resistors 15 in a direction perpendicular to an array direction thereof; and a common electrode 17B integrally connected to the other ends of all of the heating resistors 15. The heating resistors 15 and the electrode portions 17A and 17B are formed in an arbitrary order. In the patterning of a resist material for the lift-off or etching for the heating resistors 15 and the electrode portions 17A and 17B, the patterning is performed on the photoresist material by using a photomask.
Next, in the protective film forming step SA8, the film formation is performed with use of a protective film material on the upper substrate 14 on which the heating resistors 15 and the electrode portions 17A and 17B are formed, whereby the protective film 19 is formed (Step SA8). Examples of the protective film material which may be used include SiO2, Ta2O5, SiAlON, Si3N4, and diamond-like carbon. Further, examples of film forming methods which may be used include sputtering, ion plating, CVD, and the like. The protective film 19 is formed, and hence the heating resistors 15 and the electrode portions 17A and 17B can be protected from abrasion and corrosion.
Next, in the cutting step SA9, the large-size stacked substrate 13 is cut into regions of the individual thermal heads 10 (Step SA9). In this embodiment, twenty-four thermal heads 10 are formed from the single large-size stacked substrate 13.
An action of the thermal head 10 manufactured in this way is described.
When a voltage is selectively applied to the individual electrodes 17A, a current flows through the heating resistors 15 which are connected to the selected individual electrodes 17A and the common electrode 17B opposed thereto, to thereby allow the heating resistors 15 to generate heat. The heat generated by the heating resistors 15 is transferred toward the protective film 19 side to be utilized for printing and the like, and a part of the heat is also transferred toward the support substrate 12 side via the upper substrate 14.
The upper substrate 14 having the heating resistors 15 formed on the surface thereof functions as a heat storage layer that stores the heat generated by the heating resistors 15. On the other hand, the cavity portion 23 disposed between the upper substrate 14 and the support substrate 12 so as to be opposed to the heating resistors 15 functions as a hollow heat-insulating layer that prevents the heat from transferring toward the support substrate 12 side from the heating resistors 15.
Therefore, because of the cavity portion 23, it is possible to prevent a part of the heat generated by the heating resistors 15 from transferring toward the support substrate 12 side via the upper substrate 14. Accordingly, an amount of heat transferring from the heating resistors 15 toward the protective film 19 side to be utilized for printing and the like can be increased to increase use efficiency.
In this case, the heating efficiency is determined by the width and the depth of the concave portion 21, the thickness of the upper substrate 14 (distance from the heating resistor 15 to the cavity portion 23), and the like. In the method of manufacturing a thermal head according to this embodiment, in the thinning step SA5, the upper substrate 14 is processed to a thickness which is set based on the width dimension and the depth dimension of the concave portion 21. Accordingly, the fluctuations in width dimension and depth dimension among the concave portions 21 can be cancelled through adjustment to the thickness of the upper substrate 14. This reduces the occurrence of a failure, and thus a plurality of thermal heads 10 having high heating efficiency and stable quality can be manufactured.
The embodiment of the present invention can be modified as follows.
For example, in the embodiment of the present invention, in the condition setting step SA3, the evaluation points of the width and the depth of the concave portion 21 are used to set the process conditions of the upper substrate 14. Alternatively, however, based on measurement values of the width dimension and the depth dimension of the concave portion 21, the following expression may be used to set the process conditions (appropriate thickness c (μm) of the upper substrate 14):
c=ln(e−0.0084×c×(1−0.0005×(a−A)+(0.0055×b−0.69)×(b−B)))/−0.0084
where A is a basic design value (μm) of the width of the concave portion 21, B is a basic design value (μm) of the depth of the concave portion 21, “a” is an actual measurement value (μm) of the width of the concave portion 21, and b is an actual measurement value (μm) of the depth of the concave portion 21.
For example, as shown in
Similarly, at another point (measurement value 2), when the actual measurement value “a” of the width of the concave portion 21 is 183 (μm) and the actual measurement value b of the depth of the concave portion 21 is 43 (μm), the appropriate thickness c of the upper substrate 14 is 48.7 (μm). Further, at another point (measurement value 3), when the actual measurement value “a” of the width of the concave portion 21 is 204 (μm) and the actual measurement value b of the depth of the concave portion 21 is 52 (μm), the appropriate thickness c of the upper substrate 14 is 50.3 (μm).
In this way, the above-mentioned expression may be used to set the appropriate thickness of the upper substrate 14, that is, a target value (μm) of the upper substrate 14 in the thinning step SA5.
Further, as another example, as shown in
Further, for example, as shown in
As described above, by using the above-mentioned expression to set the process conditions of the upper substrate 14, the thickness of the upper substrate 14 can be adjusted more accurately so that the fluctuations in width dimension among the concave portions 21 can be cancelled with good accuracy.
Hereinabove, the embodiment of the present invention has been described in detail with reference to the accompanying drawings. However, specific structures of the present invention are not limited to the embodiment and encompass design modifications and the like without departing from the gist of the present invention.
For example, in the above-mentioned embodiment, the upper substrate 14 is processed in units of a large-size stacked substrate 13. However, the upper substrate 14 may be processed to a thickness which is set for each thermal head 10 by measuring the dimensions of the concave portions 21 for the individual thermal heads 10. In this way, thermal heads 10 with more uniform quality can be manufactured. Further, the thermal heads 10 may be individually manufactured by using support substrates 12 and upper substrates 14 which are cut into pieces in advance for the individual thermal heads 10.
Further, in the above-mentioned embodiment, in the condition setting step SA3, the thickness of the upper substrate 14 is set based on both of the width and the depth of the concave portion 21. Alternatively, however, the thickness of the upper substrate 14 may be set based on one of the width and the depth of the concave portion 21.
Further, in the above-mentioned embodiment, in the concave portion forming step SA1, the concave portion 21 is formed in the support substrate 12. However, it is only necessary to form the concave portion 21 in at least one of the support substrate 12 and the upper substrate 14. For example, the concave portion may be formed in one surface of the upper substrate 14, or the concave portions may be formed in both of the support substrate 12 and the upper substrate 14.
Further, in the above-mentioned embodiment, in the bonding step SA4, the support substrate 12 and the upper substrate 14 are bonded to each other by thermal fusion. Alternatively, however, for example, the support substrate 12 and the upper substrate 14 may be bonded to each other by an extremely thin adhesive layer or by anodic bonding. Bonding by a thick adhesive layer is not desirable in terms of thermal efficiency.
Further, in the above-mentioned embodiment, the bonding step SA4 is performed after the measuring step SA2. However, in the case where a non-contact laser displacement meter is used, it is also possible to measure the width and the depth of the concave portion 21 after the bonding step. Therefore, in this case, the measuring step and the condition setting step may be performed after the bonding step and immediately before the thinning step. The order of steps in this case is advantageous in terms of manufacturing control.
Number | Date | Country | Kind |
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2010-213291 | Sep 2010 | JP | national |