JP6231241B2 - Flow measuring device - Google Patents

Description

  The present invention relates to a flow rate measuring device that measures a flow rate of a fluid, and more particularly to a flow rate measuring device that measures an air flow rate of an internal combustion engine.

As a background art in this technical field, there is JP-A-2001-12987 (Patent Document 1). In Patent Document 1, since a step is not formed in a structure in which a depression is provided in a laminated substrate and a semiconductor sensor element is disposed there, a resin sealing film can be formed at a predetermined position with high reproducibility by a printing method. It is described. In particular, in a semiconductor sensor element having a small sensor itself, if the shape of the resin sealing film formed in the vicinity of the sensor varies, it is important because it directly leads to variations in output characteristics. By adopting such a structure, it is said that a thermal air flow sensor with improved accuracy and high reliability can be provided.

Japanese Patent Laid-Open No. 2001-12987

      Since the semiconductor sensor element is exposed in the air passage, the semiconductor sensor element is placed in an environment where it is directly exposed to corrosive gas, gasoline, engine oil, or the like. Therefore, it is necessary to protect the bonding pad and the connecting wire from corrosion with a sealing material. If the shape of the sealing material varies, it itself causes variations in output characteristics, so it is necessary to determine the shape and position with high accuracy. According to Patent Literature 1, it is possible to form a resin sealing film corresponding to a sealing material at a predetermined position with good reproducibility by disposing a semiconductor sensor element in a depression of a laminated substrate. However, epoxy resins, fluororesins, gels and the like that are generally used as sealing materials require thermosetting. For example, looking at the temperature dependence of the viscosity of the epoxy resin, it is known that the viscosity is greatly reduced during the curing sequence. For this reason, even if positioning is performed with high accuracy, the sealing material flows, and as a result, the intended position and shape cannot be obtained, and it is difficult to reduce variations in the characteristics of the flow rate measuring device.

      An object of the present invention is to provide a highly accurate flow rate measuring apparatus with little characteristic variation.

  In order to solve the above problems, for example, the configuration described in the claims is adopted.

  The present application includes a plurality of means for solving the above-described problems. For example, the organic protective film is formed by providing a region in which the organic protective film is not formed between the diaphragm and the pad. , Separated into a first organic protective film formed on the diaphragm side and a second organic protective film formed on the pad side, and an end of the first organic protective film on the pad side Is a predetermined distance away from the heating resistor, and the end of the sealing material on the side of the heating resistor is the end of the second organic protective film from the end of the first organic protective film on the pad side. Between the pad side ends.

  According to the present invention, it is possible to provide a highly accurate flow rate measuring device with little characteristic variation.

It is an example of sectional drawing of the mounting board | substrate of the flow measuring device by this invention. It is an example of the top view of the flow volume detection element of the flow volume measuring apparatus by this invention. It is another Example of sectional drawing of the flow volume detection element of this invention. It is another Example of sectional drawing of the flow volume detection element of this invention. It is another Example of sectional drawing of the flow volume detection element of this invention.

  Hereinafter, embodiments for carrying out the invention will be described with reference to FIGS.

  First, Embodiment 1 which is an embodiment of the present invention will be described.

  As shown in FIG. 1, a depression 107 is provided on the mounting substrate 101, and a flow rate detection element 108 and a control circuit element 104 having a heating resistor provided on a diaphragm 106 are mounted. The signal of the flow rate detection element 108 is connected to the wiring part 102 on the mounting substrate by, for example, a gold wire 105a. Further, the wiring 102 on the mounting substrate and the control circuit element 104 are connected by, for example, a gold wire 105b to perform signal processing, and are output from the pad 103 to the output terminal as an output signal.

Since the flow rate detecting element mounting portion A is directly exposed to the outside, it is necessary to protect the aluminum pad portion and the gold wire 105a from corrosive gas, gasoline, engine oil, and the like. In this embodiment, the sealing material 110 is potted to protect the aluminum pad portion and the gold wire 105a. In the case of such a mounting configuration, the position and shape of the sealing material 110 are important.

  This is because the resistance value varies depending on the stress due to the difference in linear expansion coefficient between the flow rate detection element 108 and the sealing material 110 and the residual stress of the sealing material 110. Stress due to difference in linear expansion coefficient This effect appears in the temperature characteristics. For example, even if the output characteristics are adjusted at room temperature, the characteristics change because the stress applied to the flow rate detection element 108 changes due to a change in the ambient temperature.

Moreover, the influence of the residual stress of the sealing material 110 appears as a change in durability characteristics. The physical property value of the sealing material 110 varies depending on the high temperature environment and the thermal cycle, and the characteristics change. Naturally, these effects become larger as the sealing material 110 is closer to the heating resistor 106. Therefore, the heating resistor 201 provided on the sealing material 110 and the diaphragm 106 needs to maintain a certain distance.

  However, the viscosity of the sealing material 110 decreases during thermal curing, and even when the sealing material 110 is applied with high accuracy, the shape changes during the curing sequence and the distance from the heating resistor provided on the diaphragm 106 varies. If you cannot keep the distance, there is a problem that occurs.

FIG. 2 shows a plan view of the flow rate detecting element 108. A heating resistor 201 (detail pattern is not shown) is formed on the diaphragm 106, and is connected to the lead wire 202 and the aluminum pad 203 (wiring pattern is not shown). In this embodiment, the water repellent organic film 109 is provided at a certain distance from the heating resistor 106. With the water repellent organic film 109, even if a shape change due to a decrease in the viscosity of the sealing material 110 occurs during the curing sequence, the water repellent organic film 109 does not flow toward the heating resistor 201 and can prevent characteristic changes. Therefore, the water repellent organic film 109 is provided in the vicinity where the sealing material 110 is applied.

  Further, if polyimide silicone is used as the water-repellent organic film 109, it is a material usually used as a protective film in the semiconductor manufacturing process, and can be formed at the same time as the flow rate detecting element 108 is manufactured, thereby reducing the cost. .

  FIG. 3 is a plan view of the flow rate detecting element 108 of the flow rate measuring device according to the second embodiment. In this embodiment, the water repellent organic film 109 is formed in a region other than the region where the sealing material is applied. Thereby, the flow rate detecting element 108 can be protected from dust colliding with the flow rate detecting element 108, and the dust resistance is improved.

  FIG. 4 is a plan view of the flow rate detecting element 108 of the flow rate measuring device according to the third embodiment. In this embodiment, the water-repellent organic film 109 b is formed in addition to the region where the sealing material is applied and the heating resistor 201 in the diaphragm 106. Since the water repellent organic film is not formed on the heating resistor 201 in the diaphragm 106, the sensitivity is not lowered due to the deterioration of heat transfer, and the surface damage due to dust other than the heating resistor 201 in the diaphragm 106 is prevented. can do.

Further, the water repellent organic film 109a is formed separately from the water repellent organic film 109b. This facilitates position detection of the seal material end during the manufacturing process. For example, it is necessary to cover a sealing material position is, the lower end of the water-repellent organic film 109 a is (aluminum pads 202 side), the lower end portion of the required distance between the sealant heating resistor 201 is water-repellent organic film 109 b If the position is on the (aluminum pad 202 side), the end position of the sealing material only needs to be in the region from the lower end of the water repellent organic film 109a to the lower end of the water repellent organic film 109b, and pattern detection can be performed by automatic inspection. become.

  In the present embodiment, an example in which the water-repellent organic film is separated into two is shown, but it may be separated into two or more if necessary. A hollow pattern may be used as shown in FIG. Thereby, since the patterns are not separated, the film is hardly peeled off.

DESCRIPTION OF SYMBOLS 101 ... Mounting board 102 ... Wiring on mounting board 104 ... Control circuit element 105a, b ... Gold wire 106 ... Diaphragm 107 ... Indentation 108 ... Flow rate detection element 109, 109a, 109b ... Water-repellent organic film 201 ... Heating resistor 202 ... Drawer Line 203 ... Aluminum pad

Claims (5)

A heating resistor provided on the diaphragm;
Pads for electrical connection with the outside by metal wires;
A semiconductor sensor element comprising: a wiring for electrically connecting the pad and the heating resistor;
The semiconductor sensor element is:
It is a surface on the side where the heating resistor is formed, and has at least a first organic protective film and a second organic protective film between the diaphragm and the pad,
The first organic protective film and the second organic protective film are separated by a region where the organic protective film is not formed,
The first organic protective film is formed on the diaphragm side from a region where the organic protective film is not formed,
The second organic protective film is formed on the pad side from a region where the organic protective film is not formed,
The pad-side end of the first organic protective film is separated from the heating resistor by a predetermined distance,
The end of the sealing material is a semiconductor sensor element located between the pad-side end of the first organic protective film and the pad-side end of the second organic protective film.   The semiconductor sensor element according to claim 1, wherein the first organic protective film does not cover the heating resistor.   The semiconductor sensor element according to claim 2, wherein the first organic protective film covers an end portion of the diaphragm.   The semiconductor sensor element according to claim 2, wherein the first organic protective film or the second organic protective film is polyimide silicone.   The semiconductor sensor element according to claim 1, wherein the pad and the wire are protected by a sealing material.

Images