Optical sensor and method for manufacturing optical sensor

Abstract

To provide an optical sensor that can stably protect a mounted IC chip and improve workability during manufacture, and a method for manufacturing the same.SOLUTION: An optical sensor includes a circuit board, a light receiving and emitting unit mounted on the circuit board for emitting and receiving light, an IC chip mounted on the circuit board, and a coating layer formed on the IC chip, and the circuit board has a component mounting area and a component mounting prohibited area, the IC chip is positioned in an area of the component mounting area adjacent to the component mounting prohibited area, and the coating layer is made of a coating agent having a thixotropy of 4.5 or more and 6.5 or less.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to optical sensors and methods for manufacturing the same. [Background technology]

[0002] An optical sensor is known that includes a light-emitting element that emits measurement light to be irradiated onto a measurement object and a light-receiving element that receives reflected light from the measurement light. The optical sensor is used, for example, to detect patch images formed on an intermediate transfer belt of a tandem image forming apparatus for measuring toner concentration and color shift. Patent Document 1 discloses an optical sensor that includes a sensor substrate that includes a light-emitting element and a light-receiving element for detecting reflected light from the patch image, and a circuit board that supports the sensor substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-128983 Summary of the Invention [Problem to be solved by the invention]

[0004] In general, in optical sensors, the control IC (IC chip) is mounted on a circuit board by wire bonding and then covered with encapsulating resin. In this case, the encapsulating resin tends to spread along the surface of the circuit board before solidifying, which can lead to problems such as poor appearance of the optical sensor, reduced protection performance for the control IC, and long manufacturing times due to poor workability during manufacturing.

[0005] An object of the present disclosure is to provide an optical sensor that can stably protect a mounted IC chip and improve workability during manufacturing, and a method for manufacturing the same. [Means for solving the problem]

[0006] An optical sensor according to one aspect of the present disclosure includes a circuit board, a light receiving and emitting unit mounted on the circuit board for emitting and receiving light, an IC chip mounted on the circuit board, and a coating layer formed on the IC chip, wherein the circuit board has a component mounting area and a component mounting prohibited area, the IC chip is disposed in an area of ​​the component mounting area adjacent to the component mounting prohibited area, and the coating layer is made of a coating agent having a thixotropy of 4.5 or more and 6.5 or less.

[0007] A method for manufacturing an optical sensor according to another aspect of the present disclosure includes mounting an optical receiver / transmitter in a component mounting area of ​​a circuit board having a component mounting area and a component mounting prohibited area, mounting an IC chip in an area of ​​the component mounting area of ​​the circuit board adjacent to the component mounting prohibited area, connecting terminals of the IC chip to the circuit board with wires, and forming a coating layer using a coating agent having a thixotropy of 4.5 or more and 6.5 or less to cover the wires and the IC chip. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide an optical sensor that can stably protect a mounted IC chip and improve workability during manufacturing, and a method for manufacturing the same. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view that schematically shows the internal structure of a color printer to which the optical sensor of the present disclosure is applied. [Figure 2] FIG. 2 is a perspective view showing an example of the arrangement of a concentration sensor, which is an example of an optical sensor. [Figure 3] 3A and 3B are schematic diagrams showing the principle of detecting black toner. [Figure 4] 4A and 4B are schematic diagrams showing the principle of color toner detection. [Figure 5] FIG. 5 is a simplified cross-sectional view illustrating an optical sensor according to one embodiment of the present disclosure. [Figure 6] FIG. 6(A) is a rear view showing an optical sensor according to an embodiment of the present disclosure, and FIG. 6(B) is a side view showing the same. [Figure 7] FIG. 7 is an enlarged side view of the periphery of an IC chip of an optical sensor according to an embodiment of the present disclosure. [Figure 8] FIG. 8 is an enlarged view showing a state in which a sealing resin is applied to the optical sensor shown in FIG. [Figure 9] FIG. 9 is a diagram showing a procedure for applying the sealing resin shown in FIG. [Figure 10] 10(A) and 10(B) are diagrams showing the state of adhesion of the sealing resin depending on the method of application of the sealing resin. [Figure 11] FIG. 11 is an enlarged side view of the periphery of an IC chip of an optical sensor according to a modified embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] An optical sensor according to an embodiment of the present disclosure will be described in detail below with reference to the drawings. The optical sensor according to the present disclosure is a module that measures the physical properties of an object by irradiating the object with measurement light and receiving the reflected light. There are no particular limitations on the object to be measured, and the object may be a solid, semi-solid, liquid, powder, or the like. There are also no particular limitations on the physical properties to be measured, as long as they can be analyzed from the reflected light. For example, the optical sensor according to the present disclosure is suitable for measuring the color and density of the object to be measured. In the embodiment described below, an optical sensor that is installed in a color printer to detect the density of toner used in image formation will be exemplified.

[0011] [Color printer instructions] First, the configuration of a color printer to which the optical sensor of the present disclosure is applied will be described. FIG. 1 is a cross-sectional view that schematically shows the internal structure of a tandem color printer 1. The color printer 1 includes image forming units 2Y, 2C, 2M, and 2Bk, an optical scanning device 23, an intermediate transfer unit 28, and a fixing unit 29, all housed in a main body housing 10. A paper output tray 11 is provided on the top surface of the main body housing 10. A sheet output port 12 opens opposite the paper output tray 11. A manual paper feed tray 13 is provided on a side wall of the main body housing 10, and a paper feed cassette 14 that stores sheets for automatic paper feeding, etc., is provided in the bottom of the main body housing 10.

[0012] Image forming units 2Y, 2C, 2M, and 2Bk are units that form toner images of yellow, cyan, magenta, and black, respectively, and are arranged in tandem at a predetermined interval horizontally. Each image forming unit 2Y, 2C, 2M, and 2Bk includes a photosensitive drum 21 having a peripheral surface that supports an electrostatic latent image and a toner image, a charger 22 that charges the peripheral surface of the photosensitive drum 21, a developer 24 that applies developer to the electrostatic latent image to form a toner image, yellow, cyan, magenta, and black toner containers 25Y, 25C, 25M, and 25Bk, respectively, that supply toner of each color to the developer 24, a primary transfer roller 26 that performs primary transfer of the toner image formed on the photosensitive drum 21, and a cleaning device 27 that removes residual toner from the peripheral surface of the photosensitive drum 21. An optical scanning device 23 scans the peripheral surface of each photosensitive drum 21 with a beam in the main scanning direction as the scanned surface, forming an electrostatic latent image on the peripheral surface for forming a toner image.

[0013] The intermediate transfer unit 28 performs primary transfer of the toner images formed on the photosensitive drums 21. The intermediate transfer unit 28 includes a transfer belt 281 that rotates while contacting the circumferential surface of each photosensitive drum 21, and a drive roller 282 and a driven roller 283 around which the transfer belt 281 is wound. The toner images on the photosensitive drums 21 of each color are primarily transferred and superimposed onto the same location on the transfer belt 281. As a result, a full-color toner image is formed on the transfer belt 281. A secondary transfer roller 15 is disposed opposite the drive roller 282, sandwiching the transfer belt 281 between them to form a secondary transfer nip T. The full-color toner image on the transfer belt 281 is secondarily transferred onto a sheet at the secondary transfer nip T.

[0014] The fixing unit 29 includes a fixing roller 291 with a built-in heat source, and a pressure roller 292 that forms a fixing nip N together with the fixing roller 291. The fixing unit 29 applies heat and pressure to the sheet, onto which a toner image has been transferred in the secondary transfer nip T, in the fixing nip N, thereby performing a fixing process in which the toner is fused to the sheet. The sheet that has undergone the fixing process is discharged from the sheet discharge port 12 toward the paper discharge tray 11.

[0015] A density sensor 16 is disposed inside the main body housing 10. The density sensor 16 is an example of an optical sensor of the present disclosure. The density sensor 16 is disposed near the secondary transfer nip T, facing the outer circumferential surface of the transfer belt 281 on which the toner image is carried. The density sensor 16 optically detects the density of the toner image formed on the transfer belt 281 and converts it into an electrical signal.

[0016] FIG. 2 is a perspective view showing an example of the arrangement of the density sensor 16. In FIG. 2, the density sensor 16 is illustrated as a first density sensor 16A and a second density sensor 16B spaced apart from each other in the main scanning direction. The first density sensor 16A is disposed at a first density detection position DP1 on the toner carrying surface 28T of the transfer belt 281, and the second density sensor 16B is disposed at a second density detection position DP2, facing each other. The two density sensors 16A and 16B optically detect toner detection patches dp carried on the toner carrying surface 28T. The toner detection patches dp include, for example, density detection patches for detecting the toner concentration of each color and position detection patches for detecting the printing position of each color. The transfer belt 281 rotates in the direction indicated by the white arrow in FIG. 2. The first density sensor 16A detects the toner concentration along a first inspection line DL1 extending from the first density detection position DP1 in the sub-scanning direction. The second density sensor 16B detects the toner density along a second inspection line DL2 that extends in the sub-scanning direction from the second density detection position DP2. An embodiment in which only one of the first density sensor 16A and the second density sensor 16B is disposed opposite the transfer belt 281 may also be adopted.

[0017] [Toner detection principle] Next, the principle of optically detecting toner on transfer belt 281 will be described with reference to Figures 3 and 4. Figure 3 is a schematic diagram showing the detection principle of black toner BT, and Figure 4 is a schematic diagram showing the detection principle of color toner CT. A light-emitting element E1 and a light-receiving element E2 are arranged facing the toner carrying surface 28T of transfer belt 281. The light-emitting element E1 is, for example, an LED (Light Emitting Diode) that can emit light of a predetermined wavelength. The light-receiving element E2 is, for example, a PD (Photo Diode) that receives light, photoelectrically converts it, and outputs a current according to the amount of light.

[0018] FIG. 3A shows the light emission and reception state when there is no black toner BT on the transfer belt 281. The toner carrying surface 28T is a smooth surface that generates specular reflection when irradiated with light. Measurement light L1 is emitted from the light-emitting element E1. The measurement light L1 is irradiated at a predetermined emission angle θ1 toward the density detection position DP on the toner carrying surface 28T. The measurement light L1 is reflected by the toner carrying surface 28T, generating specularly reflected light L2. The specularly reflected light L2 is incident on the light-receiving element E2. The light-receiving element E2 outputs a current AM1 corresponding to the amount of light received.

[0019] FIG. 3B shows the light emission and reception state when black toner BT is present on the transfer belt 281. A portion of the measurement light L1 irradiated toward the toner carrying surface 28T is absorbed by the black toner BT. In other words, the specularly reflected light L2 is substantially not generated in the area of ​​the toner carrying surface 28T where black toner BT is present. As a result, the amount of specularly reflected light L2 incident on the light receiving element E2 decreases. The light receiving element E2 outputs a current AM2 corresponding to the reduced amount of light. Naturally, the relationship AM1>AM2 holds. Whether or not black toner BT is present is detected based on the fluctuation in the current output of the light emitting element E1 accompanying such a change in the amount of received specularly reflected light L2.

[0020] Figure 4(A) shows the light emission and reception state when no color toner CT is present on the transfer belt 281. Measurement light L1 is emitted from the light-emitting element E1. The emission optical system for measurement light L1 is adjusted so that measurement light L1 is irradiated onto the concentration detection position DP at an emission angle θ2 larger than the emission angle θ1 in Figure 3(A). Measurement light L1 is reflected by the toner carrying surface 28T, generating specularly reflected light L2. Light-receiving element E2 is positioned at a position where specularly reflected light L2 does not enter. Therefore, the output of light-receiving element E2 is essentially zero.

[0021] FIG. 4B shows the light emission and reception state when color toner CT is present on the transfer belt 281. A portion of the measurement light L1 irradiated toward the toner carrying surface 28T is irradiated onto the color toner CT and diffusely reflected. In other words, not all of the measurement light L1 becomes specularly reflected light L2, but a portion becomes diffusely reflected light L3. A portion of the generated diffusely reflected light L3 is incident on the light receiving element E2. The light receiving element E2 outputs a current AM3 corresponding to the amount of diffusely reflected light L3 received. The color toner CT is detected based on the change in output of the light receiving element E2 from 0 to AM3. The optical sensor described below applies the above-mentioned detection principle.

[0022] 5 is a cross-sectional view showing a portion of the concentration sensor 16 according to this embodiment. The concentration sensor 16 includes a sensor substrate 3, a lens unit 4, a first light-shielding wall 45, a second light-shielding wall 46, and a main substrate 5 (FIG. 6). As described above, the measurement target of the concentration sensor 16 is a toner patch printed on the toner carrying surface 28T of the transfer belt 281.

[0023] The sensor substrate 3 is mounted on the main substrate 5, which will be described in detail later, and functions as a light receiving and emitting unit that emits and receives light. The sensor substrate 3 includes a substrate 30 having a mounting surface 3M and an element group 3E arranged in a row on the mounting surface 3M. A circuit pattern for mounting the element group 3E is printed on the mounting surface 3M of the substrate 30. The sensor substrate 3 is arranged so that the mounting surface 3M faces the toner carrying surface 28T. A semiconductor substrate such as a silicon substrate may be used as the substrate 30, and the sensor substrate 3 may be mounted in such a manner that each element of the element group 3E is directly formed on the semiconductor substrate.

[0024] The element group 3E includes a first light-emitting / light-receiving pair 31 for detecting black toner BT and a second light-emitting / light-receiving pair 32 for detecting color toners CT. The first light-emitting / light-receiving pair 31 consists of a first light-emitting element 33 and a first light-receiving element 34 arranged at a predetermined interval on the mounting surface 3M. The second light-emitting / light-receiving pair 32 consists of a second light-emitting element 35 and a second light-receiving element 36 arranged at a predetermined interval on the mounting surface 3M at a position different from the first light-emitting / light-receiving pair 31.

[0025] The first light-emitting element 33 and the second light-emitting element 35 are LEDs that emit light of a predetermined wavelength. The first light-receiving element 34 and the second light-receiving element 36 are PDs that output a current corresponding to the amount of light received. The elements of the element group 3E are arranged in a line in the main scanning direction shown in FIG. 2. Specifically, the elements of the element group 3E are arranged in a line on the mounting surface 3M in the order of the first light-emitting element 33, the first light-receiving element 34, the second light-receiving element 36, and the second light-emitting element 35. The elements of the element group 3E do not necessarily have to be arranged in a strict line, and may be arranged in a line with an offset that is equivalent to a line. The arrangement direction of the element group 3E may also be the sub-scanning direction.

[0026] The lens unit 4 is disposed in front of the mounting surface 3M, i.e., between the sensor substrate 3 and the toner carrying surface 28T. The lens unit 4 includes a first lens portion 41, a second lens portion 42, a third lens portion 43, and a fourth lens portion 44 as lenses that condense light. On the optical path of the first light-emitting / receiving pair 31, the first lens portion 41 is disposed in front of the first light-emitting element 33, and the second lens portion 42 is disposed behind the first light-receiving element 34. On the optical path of the second light-emitting / receiving pair 32, the third lens portion 43 is disposed in front of the second light-emitting element 35, and the fourth lens portion 44 is disposed behind the second light-receiving element 36. These four lens portions are held by a holder portion 40.

[0027] The first lens unit 41 collects light emitted by the first light-emitting element 33 to generate a first measurement light beam L11 that is irradiated as a spot at a predetermined position on the toner carrying surface 28T. The second lens unit 42 collects specularly reflected light L2 from the first measurement light beam L11 that is reflected by the toner carrying surface 28T and guides the light to the first light-receiving element 34. In other words, the first light-receiving element 34 is positioned to receive the specularly reflected light L2. The third lens unit 43 collects light emitted by the second light-emitting element 35 to generate a second measurement light beam L12 that is irradiated as a spot at a predetermined position on the toner carrying surface 28T. The fourth lens unit 44 collects diffusely reflected light L3 from the second measurement light beam L12 that is reflected by the toner carrying surface 28T and guides the light to the second light-receiving element 36. The second light-receiving element 36 is positioned to receive the optical image of the diffusely reflected light L3 generated by the fourth lens unit 44.

[0028] The first light-shielding wall 45 and the second light-shielding wall 46 are non-transparent members that do not allow light to pass through. The first light-shielding wall 45 is disposed in front of the mounting surface 3M, between the first light-emitting element 33 and the first light-receiving element 34. The first light-shielding wall 45 prevents light emitted from the first light-emitting element 33 from traveling directly toward the first light-receiving element 34 without passing through the toner carrying surface 28T. In other words, the first light-shielding wall 45 prevents light before being collected by the first lens unit 41 from being received by the first light-receiving element 34. The second light-shielding wall 46 is disposed in front of the mounting surface 3M, between the second light-emitting element 35 and the second light-receiving element 36. The second light-shielding wall 46 prevents light emitted from the second light-emitting element 35 from traveling directly toward the second light-receiving element 36. In other words, the second light-shielding wall 46 prevents light before being collected by the third lens unit 43 from being received by the second light-receiving element 36.

[0029] An open space OS is provided in front of the mounting surface 3M between the first light-emitting and light-receiving pair 31 and the second light-emitting and light-receiving pair 32, or in this embodiment, between the first light-receiving element 34 and the second light-receiving element 36. The open space OS is a non-light-shielding space in which there are essentially no light-shielding components. The open space OS is partitioned by the first light-shielding wall 45, the second light-shielding wall 46, and the lens unit 4. Note that the open space OS does not have to be a complete space, and small protrusions or structures that do not have an optical effect may be present.

[0030] Fig. 6(A) is a rear view showing the concentration sensor 16 according to one embodiment of the present disclosure, and Fig. 6(B) is a side view of the same. The main board 5 of the concentration sensor 16 supports the sensor board 3 and includes various electronic components. The main board 5 is fixed to the device body of the color printer 1. As shown in each diagram in Fig. 6, the main board 5 has a circuit board 50, and an IC chip 51 and a connector 52 mounted on the circuit board 50. Note that other electronic components are also mounted on the circuit board 50, but their description will be omitted here.

[0031] The circuit board 50 is made of a rectangular plate-like member extending in a predetermined longitudinal direction. This direction is the same as the direction in which the first light-emitting element 33, the first light-receiving element 34, the second light-emitting element 35, and the second light-receiving element 36 are arranged. As an example, the circuit board 50 is made of epoxy glass. Furthermore, as shown in FIG. 6, the sensor board 3 shown in FIG. 5 is mounted on one surface of the circuit board 50, approximately in the center in the longitudinal direction. Wiring and circuits (not shown) are formed on the circuit board 50, and electrically connect each element of the sensor board 3, the IC chip 51, the connector 52, etc. to each other.

[0032] The circuit board 50 has a component mounting area M1 and a pair of component mounting prohibited areas M2. In addition, a pair of visual inspection patterns 50A (pattern printed portions) are formed on the circuit board 50. As an example, the circuit board 50 is made of a green base material, and the visual inspection patterns 50A are white linear portions applied to the board. In other words, the area sandwiched between the pair of visual inspection patterns 50A corresponds to the component mounting area M1. The areas longitudinally outward of each visual inspection pattern 50A correspond to the pair of component mounting prohibited areas M2. In this way, in this embodiment, the component mounting area M1 and the component mounting prohibited areas M2 are separated by the visual inspection patterns 50A.

[0033] A first opening H1 and a second opening H2 are formed in the pair of component mounting prohibited areas M2. The first opening H1 is a circular opening in the circuit board 50. The second opening H2 is an elongated hole-shaped opening in the circuit board 50 on the opposite side from the first opening H1. Fixing bolts are inserted through the first opening H1 and the second opening H2 when the density sensor 16 is attached to the main housing 10 (device main body) of the color printer 1. The outer end of the second opening H2 may be shaped so that it opens to the edge of the circuit board 50. In other words, the second opening H2 may be shaped so that the edge of the circuit board 50 is notched.

[0034] The IC chip 51 includes a core chip, which is an integrated circuit. The IC chip 51 is mounted on the circuit board 50 using a COB (Chip On Board) method and is electrically connected by wire bonding. A coating layer 50S, which will be described in detail later, is formed on the IC chip 51. As shown in FIG. 6, the IC chip 51 is disposed in an area of ​​the component mounting area M1 adjacent to the component mounting prohibited area M2. More specifically, one side edge of the IC chip 51 is disposed adjacent to one visual inspection pattern 50A. Of the first opening H1 and the second opening H2, the IC chip 51 is disposed in a position closer to the second opening H2.

[0035] The connector 52 is disposed near the visual inspection pattern 50A on the opposite side from the IC chip 51. As shown in Figure 6(A), the IC chip 51 and the connector 52 are disposed on opposite sides of the short side of the main board 5. The connector 52 receives a connector terminal (not shown) extending from the main body housing 10 of the color printer 1, and enables the transmission and reception of drive voltages and various signals between the main body housing 10 and the density sensor 16.

[0036] Next, the coating layer 50S in Fig. 6(A) will be described in detail. Fig. 7 is an enlarged side view of the periphery of the IC chip 51 of the concentration sensor 16 according to this embodiment. Fig. 8 is an enlarged view showing the concentration sensor 16 shown in Fig. 7 in a state where a sealing resin has been applied.

[0037] As shown in FIG. 7, an IC chip 51 is placed on a circuit board 50 via Ag paste AP and electrically connected by wire bonding using wires W. As an example, the wires W are made of Au wires. Then, a coating agent S is discharged from a needle 100 (application nozzle) to form a coating layer 50S (FIG. 8) so as to cover the wires W and the IC chip 51. As an example, an air pulse dispenser can be used for the needle 100. Note that FIG. 8 illustrates the connection portion of the wires W on the circuit board 50 side (substrate-side connection portion WS). Also, as an example, the height h of the wires W relative to the circuit board 50 in FIG. 7 is about 0.5 mm to 0.6 mm.

[0038] As shown in FIG. 7, in order to eject the coating agent S from the needle 100, it is desirable that the viscosity of the coating agent S be low. On the other hand, as shown in FIG. 6, since the IC chip 51 is located near the component mounting prohibited area M2, it is necessary to suppress the flow of the coating agent S after application. For this reason, in this embodiment, a coating agent S with low viscosity and high thixotropy is used. Thixotropy (TI value) indicates the property of viscosity change when an external force is applied, and a coating agent with higher thixotropy has a higher viscosity in a static state and a lower viscosity in a dynamic state. By using a coating agent S with high thixotropy, it is possible to achieve both good application performance and shape retention after application.

[0039] The thixotropy of the coating agent S is preferably 4.5 or more and 6.5 or less, and more preferably 5.0 or more and 6.0 or less, under the conditions of 2 rpm / 20 rpm. In this case, the flow of the coating agent S during application can be further suppressed. The thixotropy is calculated from the ratio of viscosity values ​​at two rotation speeds. As described above, in this embodiment, the viscosity is measured at two rotation speeds, 2 rpm and 20 rpm.

[0040] Furthermore, the viscosity of the coating agent S is preferably 80 to 100 (Pa·sec) when rotating at 20 rpm, ensuring the fluidity of the coating agent S within the nozzle of the needle 100 and improving the workability of the application process.

[0041] 9 is a diagram showing the procedure for applying the coating agent S (sealing resin) shown in FIG. 8. FIGS. 10A and 10B are diagrams showing the state of adhesion of the sealing resin depending on the method of application. In this embodiment, as shown in FIG. 9, starting from the outside of the substrate-side connection portion WS in wire bonding, the coating agent S is applied in a single stroke from the outside of the IC chip 51 toward the center, from S1 to S10 in FIG. 9. In other words, the coating agent S is continuously applied in a spiral shape from the outside of the wire W toward the center of the IC chip 51.

[0042] As a result, as shown by the arrows in Fig. 10(A), the coating agent S enters from the outside of the wire W, thereby densely covering the periphery of the IC chip 51. On the other hand, as shown in Fig. 10(B), if the coating agent S is applied from directly above the wire W, voids Q (spaces) are likely to be formed, which may make it difficult to adequately protect the IC chip 51.

[0043] As described above, in this embodiment, the coating agent S with high thixotropy stably protects the mounted IC chip 51 and improves workability during manufacturing. In particular, since the coating agent S is less likely to flow after application, it is possible to prevent the coating agent S from flowing into the component mounting prohibited area M2. As a result, it is possible to improve the attachment of the concentration sensor 16 via the first opening H1 and the second opening H2. Furthermore, compared to when other coating agents with low thixotropy are used, the need for repeated temporary curing processes and visual inspections after application is reduced. Furthermore, the coating agent S can be easily applied automatically.

[0044] Furthermore, in this embodiment, since the visual pattern 50A is arranged between the IC chip 51 and the component mounting prohibited area M2, the coating agent S is easily blocked by the visual pattern 50A, which further prevents the coating agent S from flowing into the component mounting prohibited area M2.

[0045] In this embodiment, the IC chip 51 is disposed in a region of the first opening H1 and the second opening H2 that is adjacent to the second opening H2. The second opening H2 is longer than the first opening H1, improving the ease of attachment of the concentration sensor 16 when the concentration sensor 16 is mounted. In this case, the distance between the heads of bolts and screws (fastening parts) (not shown) inserted through the second opening H2 and the IC chip 51 is likely to change. In this embodiment, a portion of the coating layer 50S that covers the IC chip 51 is unlikely to spread toward the second opening H2 of the component mounting prohibited area M2, which also prevents interference between the coating layer 50S and the heads of the fastening parts.

[0046] The method for manufacturing the concentration sensor 16 includes the following steps: mounting a sensor substrate 3 (light receiving and emitting unit) that emits and receives light in a component mounting area M1 of a circuit board 50 having the component mounting area M1 and a component mounting prohibited area M2, mounting an IC chip 51 in an area of ​​the component mounting area M1 of the circuit board 50 that is adjacent to the component mounting prohibited area M2, connecting terminals of the IC chip 51 to the circuit board 50 by wire bonding, and forming a coating layer 50S on the IC chip 51 using a coating agent S having a thixotropy (2 rpm / 20 rpm) of 4.5 or more and 6.5 or less, so as to cover the wires W arranged by the wire bonding and the IC chip 51.

[0047] Furthermore, in the manufacturing method, forming the coating layer (50S) includes applying the coating agent (S) from the outside of the wire (W).

[0048] Furthermore, in the manufacturing method, forming the coating layer 50S includes continuously applying the coating agent S in a spiral shape from the outside of the wire W toward the center of the IC chip 51.

[0049] The various structures of the concentration sensor 16 described in this disclosure can also constitute some of the features of the manufacturing method described above.

[0050] Although the concentration sensor 16 (optical sensor) and its manufacturing method according to the present disclosure have been described above, the present disclosure is not limited to this.

[0051] Fig. 11 is an enlarged side view of the periphery of an IC chip of an optical sensor according to a modified embodiment of the present disclosure. In the previous embodiment, as shown in Fig. 7, the component mounting area M1 and the component mounting prohibited area M2 are separated by a visual inspection pattern 50A. However, as shown in Fig. 11, the component mounting area M1 and the component mounting prohibited area M2 may be separated by a groove 50B formed on a circuit board 50. In this case, too, the flow of coating agent S is likely to be retained and blocked by groove 50B, further preventing the coating agent S from flowing into the component mounting prohibited area M2.

[0052] Furthermore, the circuit board 50 may further include a resin film that protects the components on the circuit board 50. One example of the resin film is a known solder resist. The resin film may have an exposed portion between the component mounting area M1 and the component mounting prohibited area M2, where at least a portion of the resin film is cut out to expose the circuit board 50. In this case, too, the coating agent S is likely to be blocked by the exposed portion, further preventing it from flowing into the component mounting prohibited area M2.

[0053] Furthermore, instead of separating the component mounting area M1 and the component mounting prohibited area M2 as described above, at least one of the pattern printed area, the groove area, and the exposed area may be arranged on the circuit board 50 so as to surround the IC chip 51. In this case, too, the coating agent S is less likely to spread around the IC chip 51, and the inflow into the component mounting prohibited area M2 can be further suppressed. Alternatively, the pattern printed area, the groove area, and the exposed area may all be present.

[0054] In the previous embodiment, the IC chip 51 and the connector 52 are disposed on the same side of the circuit board 50. However, the present disclosure is not limited to this. As an example, the connector 52 may be disposed on the opposite side of the IC chip 51, i.e., on the same side as the sensor substrate 3. In this case, the connector 52 may be disposed around the sensor substrate 3 or, exceptionally, at the edge of the component mounting prohibited area M2 so as not to interfere with the light emission and light reception functions of the sensor substrate 3. In this case, the connector 52, which is taller than the IC chip 51 relative to the circuit board 50, is not disposed around the IC chip 51. This allows for stable wire bonding and coating of the coating agent S on the IC chip 51. Furthermore, the Ag paste AP is not necessarily provided. Furthermore, the sensor substrate 3 is not necessarily provided. [Explanation of symbols]

[0055] 1 color printer 100 needles 16 Density sensor (light sensor) 3 Sensor board 30 Circuit Board 31, 32 First light-emitting / receiving pair, second light-emitting / receiving pair 33, 34 First light emitting element, first light receiving element 35, 36 Second light-emitting element, second light-receiving element 4 Lens unit 5 Main board 50 Circuit Board 50A visual pattern 50B Groove 50S Coat Layer 51 IC chip 52 connectors AP Ag Paste H1 1st opening H2 2nd opening Q Void S coating agent W Wire WS board side connection part

Claims

1. A circuit board; a light receiving / emitting unit mounted on the circuit board for emitting and receiving light; an IC chip mounted on the circuit board; a coating layer formed on the IC chip; Equipped with the circuit board has a component mounting area and a component mounting prohibited area, the IC chip is disposed in an area of ​​the component mounting area adjacent to the component mounting prohibited area, The coating layer is made of a coating agent having a thixotropy of 4.5 or more and 6.5 or less.

2. 2. The optical sensor according to claim 1, wherein the thixotropy of the coating agent is 5.0 or more and 6.0 or less.

3. 3. The optical sensor according to claim 1, wherein the coating agent has a viscosity of 80 to 100 Pa·sec.

4. The optical sensor according to claim 1 , wherein the circuit board has a pattern printed portion that separates the component mounting area from the component mounting prohibited area.

5. The optical sensor according to claim 1 , wherein the circuit board has a groove that separates the component mounting area from the component mounting prohibited area.

6. the circuit board further includes a resin film that protects components on the circuit board; The optical sensor according to claim 1 , wherein an exposed portion where at least a part of the resin film is exposed is provided between the component mounting area and the component mounting prohibited area.

7. 2. The optical sensor according to claim 1, wherein at least one of a pattern printed portion, a groove portion, and an exposed portion in which at least a part of a resin film that protects components on the circuit board is exposed is arranged on the circuit board so as to surround the IC chip.

8. A method for manufacturing an optical sensor, comprising: a circuit board having a component mounting area and a component mounting prohibited area, and a light receiving and emitting unit that emits and receives light mounted in the component mounting area; Mounting an IC chip in an area of ​​the component mounting area of ​​the circuit board that is adjacent to the component mounting prohibited area; connecting a terminal of the IC chip to the circuit board by wire bonding; forming a coating layer on the IC chip using a coating agent having a thixotropy of 4.5 or more and 6.5 or less so as to cover the wires arranged by wire bonding and the IC chip; A method for manufacturing an optical sensor, comprising:

9. The method for manufacturing an optical sensor according to claim 8 , wherein forming the coating layer includes applying the coating agent from the outside of the wire.

10. 10. The method for manufacturing an optical sensor according to claim 8, wherein forming the coating layer includes continuously applying the coating agent in a spiral shape from the outside of the wire toward the center of the IC chip.

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