KR20080002056A - Optical liquid level sensor and method for fabricating the same - Google Patents

Abstract

An optical liquid level sensor and a manufacturing method thereof are provided to detect presence of liquid using light reflection or penetration characteristics and to measure a liquid level in a small storage tank using a liquid detecting sensor. An optical liquid level sensor(100) comprises a Printed Circuit Board(PCB,110), a pair of a light emitting unit(120) and a light receiving unit(130), a first molding unit(150), and a second molding unit(160). The pair of the light emitting unit and the light receiving unit is mounted on the electric circuit pattern of the PCB. The first molding unit isolates the light emitting unit and the light receiving unit. The second molding unit is formed on the light emitting unit, the light receiving unit, and the first molding unit to send light of the light emitting unit to the light receiving unit. A manufacturing method thereof includes a step of forming the first molding unit with two apertures, on the PCB by using a light shielding material; a step of mounting the light emitting unit and the light receiving unit at the aperture of the first molding unit; and a step of forming the second molding unit on the first molding unit to send the light of the light emitting unit to the light receiving unit.

Description

Optical liquid level sensor and method for fabricating the same

1 is a cross-sectional view for explaining an optical liquid level sensor according to an embodiment of the present invention.

2 is a process flowchart for explaining a method of manufacturing an optical liquid level sensor according to an embodiment of the present invention.

3A, 4A, and 5A are process plan views for explaining a method of manufacturing an optical liquid level sensor according to an embodiment of the present invention.

3B, 4B and 5B are cross-sectional views illustrating a method of manufacturing an optical liquid level sensor according to an embodiment of the present invention.

(Explanation of symbols for the main parts of the drawing)

100; Optical liquid level sensor 110; Board

120; Light emitting unit 130; Receiver

140; Adhesive 150; First molding part

160; 2nd molding part

The present invention relates to an optical liquid level sensor and a method for manufacturing the same, and more particularly, to an optical liquid level sensor and a method for manufacturing the same, which detect the presence or absence of a liquid using light reflection or transmission properties, and which can be miniaturized.

As is well known, a sensor is a functional element for detecting, detecting, determining, and measuring a physical quantity such as temperature, pressure, or humidity, and its types vary according to the purpose or driving principle. Among these sensors, the optical liquid level sensor includes a light emitting chip and a light receiving chip mounted on a lead frame, as disclosed in US Pat. No. 4,962,395. The light emitting chip and the light receiving chip are sealed through a molding made of a transparent material. The optical liquid level sensor determines the presence or absence of liquid using total reflection.

Total reflection means that when light is incident from an optically dense medium (large refractive index material) to a small medium (small refractive index material), the incident light is above a certain angle (critical angle). This is all reflected. Using this property, an optical liquid level sensor is manufactured such that total reflection occurs at the interface between the molding and the external environment, that is, liquid or air. Accordingly, the amount of light received by the light receiving chip of the light emitted from the light emitting chip varies according to the liquid condition or the air condition in the external environment contacting the molding part. Through this principle, the optical liquid level sensor checks for the presence of liquid at that location.

However, the optical liquid level sensor as described above mounted and molded the light emitting chip and the light receiving chip on the lead frame, so that the total volume thereof was considerable. Therefore, there is a difficulty in applying to a fuel cell or the like that is being developed as a power source of a small portable electronic device that has recently been developed. In addition, there is a problem that the molding part is transparent, so that external light is received by the light-receiving chip, causing malfunction, and there is also a problem that a separate light guide product must be used.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems of the prior art, and the present invention is to provide an optical liquid level sensor capable of miniaturizing and detecting the presence or absence of a liquid using light reflection or transmission properties, and a method of manufacturing the same. The purpose.

Another object of the present invention is to provide a liquid level measurement system capable of measuring the liquid level of a small reservoir using a liquid detection sensor.

An optical liquid level sensor of the present invention for achieving the above object comprises a printed circuit board having an electrical circuit pattern; A pair of light emitting part and a light receiving part mounted on an electric circuit pattern of the printed circuit board; A first molding part separating the light emitting part from the light receiving part; And a second molding part formed on the light emitting part, the light receiving part, and the first molding part to transmit the light of the light emitting part to the light receiving part.

The light emitting portion emits light using a light emitting element, and preferably, a light emitting diode is used as the light emitting element. The light receiving unit may be received using a light receiving element, and for example, a photo transistor, a photo diode, or a direct photo sensor may be used. The light emitting or light receiving element may be mounted on a substrate by a conventional mounting method. In a preferred embodiment, a light emitting diode chip and / or a light receiving sensor chip is attached to a substrate using a conductive adhesive, and a chip pad is used as a conductive wire. It can be mounted by connecting a pad of the substrate.

In the present invention, that the first molding part isolates the light emitting part from the light receiving part means that the light emitted from the light emitting element is not transmitted directly through the first molding part because the first molding part is opaque. .

In the practice of the present invention, it is preferable to prevent the light emitted from the light emitting portion from being dispersed and to be isolated from the peripheral portion so as to prevent the light receiving portion from being affected by the ambient disturbance light. In a preferred embodiment of the present invention, it is preferable that the first molding part stacks dams around the light emitting part and the light receiving part so as to be opened so as to isolate each other and the surroundings.

In the present invention, the second molding part is transparent, and is made of plastic resin, preferably epoxy so that light emitted from the light emitting part in the air is incident on the light receiving part by total reflection. In the present invention, the second molding portion is not limited in shape as long as it can guide light of the light emitting portion to the light receiving portion. In one embodiment of the present invention, the second molding portion may have a prism shape or a dome shape having a first inclined surface and a second inclined surface.

In one aspect, a method of manufacturing an optical liquid level sensor according to the present invention

Forming a first molding part having two openings using a light shielding material on a printed circuit board;

Mounting a light emitting part and a light receiving part in the opening of the first molding part;

Forming a second molding part on the first molding to transmit the light of the light emitting part to the light receiving part; And

It includes; cutting to have a pair of light emitting portion and the light receiving portion.

In one aspect, the present invention provides a liquid level measurement system,

A substrate; A pair of light emitting part and a light receiving part mounted on an electric circuit pattern of the printed circuit board; A first molding part separating the light emitting part from the light receiving part; A sensor including a second molding part formed on the light emitting part, the light receiving part, and the first molding part to transmit the light of the light emitting part to the light receiving part has the second molding part contacting the storage liquid, and the printed circuit board is in contact with the outside of the storage tank. It is installed in accordance with the height through the wall surface, wherein the printed circuit board provides a measurement system, characterized in that electrically connected.

In the present invention, the printed circuit board is preferably interconnected using a flexible circuit board to enable a thin film measuring system.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Like numbers refer to like elements throughout.

1A is a perspective view illustrating an optical liquid level sensor according to an exemplary embodiment of the present invention, and FIG. 1B is a cross-sectional view illustrating an optical liquid level sensor according to an exemplary embodiment of the present invention.

1A and 1B, an optical liquid level sensor 100 according to an exemplary embodiment of the present invention includes a pair of light emitters 120 and a light receiver 130 mounted on a substrate 110 and the pair of light emitters 120 and 130. And a first molding part 150 and a second molding part 160 surrounding the light emitting part 120 and the light receiving part 130.

In general, the substrate 110 may be a printed circuit board 110 (PCB) having a predetermined electric circuit pattern formed on an upper surface thereof. The pair of light emitting parts 120 and the light receiving parts 130 are mounted on the substrate 110 through a conductive adhesive 140 or a tape, and are preferably arranged in parallel on the substrate 110. In this case, the light emitting unit 120 may be composed of a light emitting diode made of a compound semiconductor, the light emitting diode should be able to emit light of any one of ultraviolet light, visible light and infrared wavelength.

The light receiver 130 may be configured of any one optical sensor selected from a photodiode of silicon material, a phototransistor of silicon material, and an IC photo sensor, and should be able to convert the amount of received light into an electrical signal.

The first molding part 150 opens a portion on which the light emitting part 120 and the light receiving part 130 are mounted on the substrate 110, and is made of a material capable of blocking light. Preferably, the first molding part 150 may be made of a material containing a plastic resin component having an absorbance of incident light of 50% or more. For example, the first molding part 150 may be made of a black epoxy resin. It is not intended to limit.

The second molding part 160 isolates the light emitting part 120 and the light receiving part 130 from the external environment on the first molding part 150, and is transparent and has a refractive index of 1.4 or more and 2.0 or less. It is preferable that it consists of a material containing a component. In addition, the shape of the second molding part 160 may be formed in a prism shape or a hemispherical dome shape (not shown in the drawing). At this time, when the molding part is formed in a prism shape, the inclined surfaces are referred to as the first inclined surface 160A and the second inclined surface 160B, respectively.

Operation of the optical liquid level sensor 100 of the present invention as described above is as follows.

First, the light emitter 120 emits light. The light emitted from the light emitter 120 is emitted upward through the opened portion of the first molding part 150. In this case, the light that is not emitted to the upper portion of the light emitting part 120 is absorbed by the first molding part 150. Some of the light emitted upward from the light emitting part 120 is incident on an interface between the second molding part 160 and an external environment, for example, air or liquid, that is, the first inclined surface 160A. In this case, the total reflection of the incident light is determined according to the environment of the first inclined surface 160A.

In more detail, when the light incident at 45 ° with the first inclined surface 160A of the second molding part 160 has a refractive index of the second molding part 160 is 1.5 or more, the first inclined surface 160A In the case of bordering with air, total reflection occurs on the first inclined surface 160A.

In addition, when the first inclined surface 160A borders a liquid such as water (refractive index 1.33), total reflection does not occur in the first inclined surface 160A, and light is refracted and transmitted.

The light totally reflected by the first inclined surface 160A is directed to the second inclined surface 160B, and some of the light may be totally reflected according to the environment of the second inclined surface 160B. That is, when the second inclined surface 160B borders air, the light is totally reflected on the second inclined surface 160B.

Light totally reflected by the second inclined surface 160B is received by the light receiving unit 130 toward the light receiving unit 130.

The light receiving unit 130 transmits information on the amount of light received to the outside, and determines the presence or absence of liquid at the position of the optical liquid level sensor 100 according to the embodiment of the present invention according to the information.

2 is a flowchart illustrating a method of manufacturing an optical liquid level sensor according to an embodiment of the present invention.

Referring to FIG. 2, the method of manufacturing the optical liquid level sensor 100 according to the embodiment of the present invention may include forming a first molding part 150 having two openings 150A (S1), and 1 mounting the light emitting unit 120 and the light receiving unit 130 on the substrate 110 using the conductive adhesive 140 in the opening 150A of the molding unit 150 (S2) and the mounted light emitting unit Forming the second molding part 160 by molding the 120 and the light receiving part 130 (S3), and cutting the optical liquid level sensor including a pair of the light emitting part 120 and the light receiving part 130 ( By proceeding to the step (S4) of separating the 100, it is possible to manufacture the optical liquid level sensor 100 of the present invention.

3A, 3B, 4A, 4B, 5A, and 5B are process plan views and process cross-sectional views illustrating a method of manufacturing an optical level sensor according to an exemplary embodiment of the present invention. Hereinafter, a method of manufacturing an optical liquid level sensor according to an exemplary embodiment of the present invention will be described with reference to FIG. 2.

First, in the step S1 of forming the first molding part 150 having two openings 150A, as shown in FIGS. 3A and 3B, the light emitting part 120 and the light emitting part 120 are formed on the substrate 110. A first molding part 150 having two openings 150A, which are spaces in which the light receiving part 130 is accommodated, is formed. In this case, the substrate 110 may be a printed circuit board 110 (PCB) divided into respective zones to mount a plurality of pairs of the light emitting unit 120 and the light receiving unit 130.

In addition, the first molding part 150 is formed to have openings 150A through which the light emitting part 120 and the light receiving part 130 of the substrate 110 are mounted, respectively. May be made of a material including a plastic resin component having an absorption rate of incident light of 50% or more, and for example, may be made of a black epoxy resin.

After forming the first molding part 150, the light emitting part 120 and the light receiving part 130 are formed on the substrate 110 by using the conductive adhesive 140 in the opening 150A of the first molding part 150. In the step (S2) to be mounted on the first, the light emitting unit 120 and the light receiving unit 130 pairs are prepared. In this case, the light emitting unit 120 may be composed of a light emitting diode made of a compound semiconductor, the light emitting diode should be able to emit light of any one of ultraviolet light, visible light and infrared wavelength.

In addition, the light receiving unit 130 may be configured of any one optical sensor selected from a silicon photodiode, a silicon phototransistor, and an IC photosensor, and should be able to convert the amount of light received into an electrical signal. .

Then, as illustrated in FIGS. 4A and 4B, the conductive adhesive 140 is coated on the lower surfaces of the light emitting part 120 and the light receiving part 130, and the opening of the first molding part 150 is applied using the conductive adhesive 140. The light emitting unit 120 and the light receiving unit 130 are mounted on the substrate 110 through 150A.

Forming the mounted light emitting unit 120 and the light receiving unit 130, which is performed after mounting the light emitting unit 120 and the light receiving unit pair on the substrate 110, to form the second molding unit 160. Step S3 is a step of forming the second molding part 160 by molding the light emitting part 120 and the light receiving part pair 130 to be isolated from the external environment using a transparent material.

In this case, the second molding part 160 may be formed in a prism shape including a first inclined surface 160A and a second inclined surface 160B, or may be formed in a hemispherical dome shape.

Meanwhile, in the above, the second molding part 160 is formed by molding, for example. However, the second molding part 160 is manufactured in advance, and thus the light emitting part 120 and the light receiving part 130 are formed. May be mounted on the substrate 110 and then assembled.

After the second molding part 160 is formed, the optical liquid level sensor 100 including the pair of light emitting parts 120 and the light receiving part 130 is cut and separated (S4). A step of cutting and separating the substrate 110 on which the pair of the unit 120 and the light receiving unit 130 are mounted and the second molding is completed is performed by a unit including one light emitting unit 120 and the light receiving unit 130 pairs. As a result, the individual optical liquid level sensor 100 having one light emitting unit 120 and the light receiving unit pair 130 is completed.

Thereafter, although not shown in the drawing, the optical liquid level sensor 100 may be mounted on the flexible circuit board 110 (FPC) to measure the height of the liquid in various ways. It can also be manufactured as a module.

As described above, the optical liquid level sensor 100 according to the exemplary embodiment of the present invention sequentially applies a process similar to a semiconductor package process to manufacture the light emitting unit 120 and the light receiving unit 130 on the substrate 110. The structure of the first molding part 150 and the second molding part 160 may be integrated.

In addition, by integrating each component, the product can be downsized to a size of up to 5 mm or less. Therefore, the present invention can also be applied to fuel cells and the like, which are being developed as power sources of small portable electronic devices that are being developed recently. This is because the refractive index of methanol, the main fuel source of the fuel cell, is 1.328, which is similar in optical properties to water.

In addition, the productivity of the product can be improved by consistently advancing each component part to a packaging process instead of an assembly process.

As described above, according to the present invention, the present invention can provide an optical liquid level sensor 100 and a method of manufacturing the same, which detect the presence or absence of a liquid using light reflection or transmission properties, and which can be miniaturized.

While the foregoing has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (10)

A printed circuit board on which an electric circuit pattern is formed; A pair of light emitting parts and a light receiving part mounted on an electric circuit pattern of the printed circuit board; A first molding part separating the light emitting part from the light receiving part; And A second molding part formed on the light emitting part, the light receiving part, and the first molding part to guide the light of the light emitting part to the light receiving part; Optical module package comprising a. The optical module package of claim 1, wherein the second molding part guides the light of the light emitting part to the light receiving part through total reflection. The optical module package of claim 1, wherein the light emitting part is made of a compound semiconductor. The optical module package of claim 1, wherein the light receiving unit is selected from a group consisting of a silicon photodiode, a silicon phototransistor, and an IC photo sensor. The optical module package of claim 1, wherein the first molding part is a plastic capable of absorbing light emission of the light emitting part. The optical module package of claim 1, wherein a dam is formed around the mounted optical elements to open the upper part. The optical module package of claim 1, wherein the second molding part has a refractive index of 1.4 or more and 2.0 or less. The optical module package of claim 1, wherein the second molding part has a prism shape, a hemispherical shape, or an angular structure. A printed circuit board on which an electric circuit pattern is formed; A pair of light emitting parts and a light receiving part mounted on an electric circuit pattern of the printed circuit board; A first molding part separating the light emitting part from the light receiving part; And A second molding part formed on the light emitting part, the light receiving part, and the first molding part to guide the light of the light emitting part to the light receiving part; Optical module package for level measurement comprising a. A substrate; A pair of light emitting part and a light receiving part mounted on an electric circuit pattern of the printed circuit board; A first molding part separating the light emitting part from the light receiving part; A sensor including a second molding part formed on the light emitting part, the light receiving part, and the first molding part to transmit the light of the light emitting part to the light receiving part has the second molding part contacting the storage liquid, and the printed circuit board is in contact with the outside of the storage tank. Measuring system, wherein the printed circuit board is electrically connected to the wall through the wall.

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