JPS638915A - Thin film cooling element and its control method - Google Patents

Abstract

PURPOSE:To make the power consumption of the whole element constant by stacking a Peltier element and a heating resistance body on a substrate and constituting a thin film cooling element, and computing the power consumption of the Peltier element which varies with humidity and controlling electric power supplied to the heating resistance body. CONSTITUTION:The Peltier element 2 and heating resistance body 50 are stacked on the substrate and the heating resistance body 50 is so controlled that the sum of the power consumption of the Peltier element 2 and the power consumption of the heat resistance body 50 is always constant. The temperature rise value of the substrate of the thin film cooling element, therefore, becomes constant. Further, when a thermocouple is used to detect the water drop temperature of the cooling part for the Peltier element 2 and obtain an output corresponding to the temperature difference between the substrate temperature and water drop temperature, the water drop temperature is accurately obtained from the room temperature. Further, when a resistance bulb is stacked on the substrate, the temperature rise value to the room temperature of the substrate is constant, so the room temperature is accurately found to obtain the absolute humidity from the water drop temperature and the relative humidity from the water drop temperature and room temperature.

Description

Detailed Description of the Invention "Target Technical Field" This invention integrates a Peltier element and a heating resistor in a thin film on a substrate, and calculates the temperature of the substrate and the room temperature at the time when water droplets are generated at the endothermic junction of the Peltier element. The present invention relates to a thin film cooling element for determining humidity and a method for controlling the same.

"Background of the Invention" A humidity detection element is constructed by integrating a Peltier element and a temperature sensing resistor for detecting room temperature on a substrate, and the current supplied to the Peltier element is controlled so that water droplets are generated at the heat-absorbing joint of the Peltier element. At that time, the water droplet generation temperature near the heat-absorbing junction of the Peltier element and the room temperature are measured, and the humidity is determined from these two temperatures.In the thin film cooling element, the current supplied to the Peltier element changes depending on the humidity in the air. do. That is, as shown in FIG. 10, the power consumption A of the Peltier element changes depending on the humidity. Furthermore, the power consumption B of the entire humidity detection element varies depending on the power consumption of the Peltier element. Further, the temperature rise value of the substrate of the humidity detection element is not constant but varies depending on the relative humidity. For this reason, the room temperature and water droplet generation temperature obtained from the temperature sensing resistor integrated on the substrate that detects the room temperature include the temperature rise value of the substrate, and this temperature rise value is not constant (and therefore calculation correction is not easy. It is very difficult to calculate the temperature behavior in a transient state when the power consumption fluctuates due to a change in humidity, which poses a problem in terms of humidity detection accuracy.

"Objective" In view of the above-mentioned problems, the present invention aims to maintain a constant rise value of a substrate in a thin film cooling element with respect to room temperature, and to accurately detect water droplet temperature from room temperature.

``Summary'' In order to achieve the object, this invention configures a thin film cooling element by integrating a Peltier element and a heating resistor on a substrate, and reduces the power consumption of the Peltier element, which changes depending on humidity. The voltage and supply to the element are calculated based on the flow, the power supplied to the heating resistor is controlled, and the power consumption of the entire element is always kept constant.

"Example" First, an example in which the thin film cooling element of the present invention is applied to a humidity detection element will be described according to its manufacturing process.

FIG. 1 is a perspective view of this embodiment during manufacture.

The substrate 20 is made of a metal such as stainless steel or a material such as a single crystal silicon wafer. On this substrate 20, silicon nitride (Si), which has good moisture resistance, is first formed as an insulating layer 22.
, N4) film to a thickness of about 6000 A using a plasma CVD apparatus.

Next, the first Peltier metal 24. First thermocouple metal 28
．． Then, a P-type lead tellurium (PbTe) thin film having a thickness of 2 μm, which will become the temperature sensing resistor 32, is formed on the insulating layer 22 by vapor deposition.

Then, using the ear side technique, this P-type tellurium lead thin film was selected to form the notch of the first Peltier metal 24°, the first thermocouple metal 28, and the resistance temperature detector 32 as shown in FIG. Etching.

That is, the first Peltier metal 24 has a plurality of strip-shaped knots extending from the periphery of the surface of the insulating layer 22 to the center arranged at predetermined intervals, and the first thermocouple metal 28 has Like the Peltier metal 24, it is a band-shaped knot extending from the periphery to the center.

Further, the temperature sensing resistor 32 is patterned around the surface of the insulating layer 22 so as to surround the first Peltier metal 24 and the first thermocouple metal 28 . Note that this resistance temperature detector 32 functions as a room temperature detection means.

Furthermore, a heating resistor 50 is turned around the surface of the insulating layer 22 so as to surround the temperature measuring resistor 32, and this heating resistor has a function as a heating means.

Next, on the surface where the first Peltier metal 24 and the like have been patterned as described above, a silicon nitride film as the insulating layer 22 is formed to a thickness of about 3,000 mm using a plasma CVD apparatus.

Thereafter, by selectively etching this silicon nitride film using a side-side technique, a contact hole for a joint between the first Vertier metal 24 and the second Peltier metal 25 to be formed later, and a first A hole is created for a junction between the second thermocouple metal 28 and the second thermocouple metal 29 that will be formed later. These contact holes are formed at the ends of first Peltier metal 24 and first thermocouple metal 28.

Next, a thin film of n-type tellurium lead having a thickness of approximately 2 μm, which will become the second Peltier metal 25 and the twentieth thermocouple metal 29, is formed by vapor deposition over the entire surface of the insulating layer 22 including the contact hole.

Thereafter, selective etching is performed using a four-cut technique to form the pattern of the second Peltier metal 25 and second thermocouple metal 29 shown in FIG.

That is, the second Peltier metal 25 connects the central end of the first Peltier metal 24 (the contact hole is formed in the upper part) and the first Peltier metal 24.
The peripheral side end of another first Peltier metal 24 adjacent to 4 (a contact hole is also formed in this upper part)
It is patterned into a strip to connect the two.

However, only one end of one of the plurality of second Peltier gold pAs 25 is joined to the first Peltier metal 24, and the other end becomes one electrode part of the Vertier cooling means described later. In addition, a plurality of first Peltier metals 24
Only one end of one of them is joined to the second Peltier metal 25, and the other end becomes the other electrode part of the Peltier cooling means.

By this patterning, the first Peltier metal 24 and the second Peltier metal 25 are alternately and continuously connected and electrically integrated to form a Vertier element, that is, a Peltier cooling means.

That is, among the joints between the first Peltier metal 24 and the second Peltier metal 25, those located at the center of the substrate 20 are referred to as the first joint group 26, and those located at the periphery are referred to as the second joint group. In the case of the joint group 27, passing a current in a predetermined direction causes the first joint group 26 to absorb heat and the second joint group 27 to generate heat. Utilizing this heat absorption effect, it is possible to cool the central part of the element where the first joint group 26 is concentrated.

The 20th thermocouple metal 29 has a band-like pattern extending from the central end of the first thermocouple metal 28 in which the contact hole is formed to the peripheral portion in parallel with the first thermocouple metal 28. The junction between the first thermocouple metal 28 and the second thermocouple metal 29 becomes the temperature sensing part 30, and the other ends of both metals become the electrode parts of the thermocouple as cooling temperature detection means.

Next, a silicon nitride film, which will become the insulating layer 22, is again formed to a thickness of about 6000 A using a plasma CVD apparatus so as to cover the Peltier cooling means, the room temperature detection means, and the cooling measurement detection means. By selectively etching the film, contact holes are formed in each electrode portion of the Peltier cooling means, the cooling temperature detecting means, and the room temperature detecting means.

After that, a thin metal film of aluminum or the like with a thickness of about 1μ is applied.
Pads 34a, 34b of the Peltier cooling means as shown in the perspective view of FIG. Pads 35a, 35b of cooling temperature detection means, pad 36 of room temperature detection means
a, 36b, the pads 55a, 55b of the heating means and the water droplet detection means 33 are patterned.

As can be seen from the perspective view of FIG. 2, the water droplet detection means 33 is
Two comb-shaped electrodes 33a and 33b in the center of the element
A flat capacitor is formed by facing each other so as to interlock with each other.

Next, a silicon nitride film is deposited on both the front and back sides of the device using plasma CVD.
It is produced to a thickness of about 6000 Å using D equipment. This is because silicon nitride is an extremely stable material and is therefore used as a protective film.

Then, using the four-cut technique, the silicon nitride film at the center of the back side of the substrate 20 is selectively removed by plasma etching to form an opening, and the substrate 20 is etched through this opening.
is removed by etching down to the insulating layer 22. FIG. 3 is a sectional view showing the state at this time, and it can be seen that a recess 21 is formed in the center of the substrate 20 by etching from the back surface of the substrate 20.

As a final step, as shown in the schematic perspective view of FIG. 4, by selectively etching a portion of the silicon nitride film on the element surface around the recess 21 using a four-cut technique, the element surface and the recess are etched. A through hole 23 is formed to communicate with the electrode 33a.

33b, . . . , 36a, 36b, bonding pad openings for connection with external circuits are formed. The through hole 23 is formed to eliminate the pressure difference between the air inside the recess 21 and the atmosphere in contact with the upper surface of the insulating layer 22. After that, the board is diced,
Each chip is cut out and packaged in a predetermined manner.

Through the above steps, the humidity detection element of this example is manufactured.

Note that although the recesses 21 are formed by etching from the back surface of the substrate 20, a microbridge structure realized by anisotropic etching of a silicon substrate may also be applied, as shown in the perspective views of FIGS. 5 and 6. It is possible.

Also, the first Peltier metal 24. Second Peltier metal 2
It goes without saying that the pattern No. 5 is not limited to the pattern of the embodiment, as long as the first joint group 26, which is the cooling part, can be concentrated at a predetermined location.

Further, in this embodiment, the Peltier cooling means 2 constitutes one series circuit by alternately connecting the first Peltier metal 24 and the second Peltier metal 25, but at least one series circuit It is sufficient that the circuits are formed, and two or more sets of series circuits may be connected in parallel.

Furthermore, depending on the metal used, the junction between the first Peltier metal 24 and the second Peltier metal 25 may not be an ohmic junction but a semiconductor junction (for example, a Schottky junction).
However, in such a case, by making an electrical connection through a metal of nickel isothermal 3, it is possible to suppress the generation of Joule heat in the cooling part and prevent a decrease in cooling capacity.

Furthermore, depending on the metal used, the junction between the first Peltier metal 24 and the second Peltier metal 25 may not be an ohmic junction but a semiconductor junction (for example, a Schottky junction).
However, in such cases, by making electrical connections through nickel isothermal 3 metal, it is possible to suppress the generation of Joule heat in the cooling section and prevent a decrease in cooling capacity. .

Next, a circuit configuration when the humidity detection element of this embodiment is actually used as a dew point hygrometer will be explained based on the block diagram of FIG.

The part surrounded by the dashed line is the humidity detection element 1, and the Peltier cooling means 2. Water drop detection means 3. Cooling temperature detection means 4. Room temperature detection means 52 includes heat generation means 13.

The current generating circuit 6 is a circuit that supplies a necessary current to the Peltier cooling means 2, and is a circuit that determines the cooling capacity of the Peltier cooling means 2.

The water droplet detection circuit 7 is a circuit that directly detects a change in impedance of the water droplet detection means 3, and detects this change to determine the presence or absence of water droplets. That is, the presence or absence of water droplets is detected by utilizing the fact that the capacitance of the capacitor constituting the water droplet detection means 3 increases (changes) due to adhesion of water droplets.

In the temperature difference detection circuit 8, a thermocouple serving as the cooling temperature detection means 4 detects an electromotive force generated based on the difference between the cooling part and the room temperature in the Peltier cooling means 2, and detects the difference between the cooling part and the room temperature from this electromotive force. This is a circuit that detects temperature differences.

The room temperature detection circuit 9 is connected to the temperature-measuring resistor 32 as the room-temperature detecting means 5, and has a function of detecting the room temperature Ta from the resistance change of the temperature-measuring resistor 32.

The current generating circuit 15 is 1! necessary for the heat generating means 13! This is a circuit that supplies current.

The microcomputer IO has a current generating circuit 6.15.
Water drop detection circuit 7. Temperature difference detection circuit 8. It is connected to the room temperature detection circuit 9 via a bus 12, and controls the current generation circuits 6 and 15 according to the presence or absence of water droplets detected by the water droplet detection circuit 7, and also controls the temperature difference ΔT detected by the temperature difference detection circuit 8. It has a function of calculating absolute humidity and relative humidity using the indoor temperature Ta detected by the room temperature detection circuit 9.

The interface 11 is connected to the microcomputer 10 and has a function of sending information regarding the dew point temperature, absolute humidity, relative humidity, etc. of the microcomputer 10 to an external device (not shown).

Next, the operation of the dew point hygrometer configured as described above will be explained according to a flowchart executed by the microcomputer 10 shown in FIG.

First, the microcomputer 10 instructs the current generation circuit 6 to cause the maximum current to flow through the Peltier cooling means 2 (step 101).

When a current flows through the Peltier cooling means 2, the joint group 26.2
7, the Beltier effect occurs. That is, an endothermic action occurs in the first joint group 26, and an exothermic action occurs in the second joint group 27.

The first joint group 26 is concentrated in the center of the humidity detection element 1, and is formed in a thin film layer with both the front and back surfaces exposed to the air, so it is thermally insulated. There is.

Therefore, cooling of the vicinity of the first joint group 26, that is, the cooling portion, can be achieved with an extremely small amount of current.

On the other hand, the second joint group 27 is distributed around the humidity detection element 1 and is formed in a thin film layer that is in close contact with the substrate 20, so that the heat generated therefrom is immediately transmitted into the substrate 20. . Therefore, there is almost no temperature rise in the vicinity of the second joint group 27, and there is no effect on the cooling effect of the first joint group 26.

Therefore, the cooling part located in the center of the humidity detection element 1 is quickly cooled to below the dew point temperature, and the insulating layer further above the water droplet detection means 3 formed on this cooling part A dew condensation phenomenon appears on 22, and water droplets adhere to it.

As mentioned above, the water droplet detection means 3 consists of two opposing electrodes 33a and 33b separated from each other, so when a water droplet adheres to the insulating layer 22, the dielectric constant increases and the gap between the electrodes 33a and 33b increases. The impedance will drop rapidly.

The water droplet detection circuit 7 detects a change in the impedance of the water droplet detection means 3, and the microcomputer 10 knows the presence or absence of water droplets from the output of the water droplet detection circuit 7 (step 102).
.

The water droplet detection circuit 7, for example, excites the water droplet detection means 3 with an oscillation pulse of a constant period, converts the impedance value of the water droplet detection means 3 into a corresponding voltage value using an integrating circuit,
A conceivable configuration is to use a comparator that compares this voltage value with a predetermined level to detect the presence or absence of water droplets.

By cooling the cooling part of the Peltier cooling means 2 with the maximum current, water droplets adhere within a predetermined time, and when the water droplet detection circuit 7 detects this, the microcomputer 10 reduces the cooling current by 8% (step 105). At this time, if water droplets do not adhere even after a predetermined period of time has elapsed, since the atmospheric condition is outside the measurement range, a display signal to that effect is output (steps 103, 104).

After reducing the cooling current by 8%, a predetermined period of time has elapsed.

At this point, the presence or absence of water droplets is determined again (step 106).
). If the water droplet detection circuit 7 continues to output a water droplet presence signal even after the cooling current decreases, the microcomputer 10 further reduces the total cooling current by 8% (step 10).
5) Through such circulation, the Peltier cooling means 2
Gradually reduce the cooling capacity of.

Due to the decrease in the cooling capacity of the Peltier cooling means 2, water droplets no longer adhere to the water, and furthermore, the water droplets begin to disappear due to evaporation.

When the water droplet detection circuit 7 detects the disappearance of water droplets, the cooling current is increased by M (<N)% to increase the cooling capacity and return to the dew point temperature at which water droplets begin to adhere (step 107).

When the water droplet detection circuit 7 detects adhesion of water droplets (step 1
08), the microcomputer 10 detects the temperature difference ΔT between the cooling unit and the room temperature detected by the cooling temperature detection means 4 and the room temperature Ta detected by the room temperature detection means 5 through the temperature difference detection circuit 8 and the room temperature detection circuit 9, respectively. and read it (steps 110 and 111).

Note that the cycle of increasing the cooling current by M% (step 1)
07, 108, and 109), if the cooling current reaches the maximum, it means that the atmospheric condition is outside the measurement range, and a display signal to that effect is output (step 104).

As described above, the cooling temperature detecting means 4 also includes thermocouples 28 and 29, which have a temperature sensing portion 30 located approximately in the center of the element 1, and the other ends of the thermocouples 28 and 29 are connected to the periphery of the element 10, that is, the substrate that is not in the recess 21. 20, this temperature difference ΔT is the difference between the temperature value of the substrate 20, which is close to room temperature, and the temperature value of the cooling section of the Beltier cooling means.

As described above, the room temperature detection means 5 includes the temperature measuring resistor 32, and detects the room temperature value by converting a change in resistance value due to a change in room temperature into a voltage value by flowing a minute current.

The microcomputer 10 calculates the temperature difference ΔT and the indoor temperature Ta.
is read, T d = Ta - Δ T is determined (step 112). This Td is the dew point temperature of the cooling section of the Beltier cooling means 2.

A ROM (not shown) in the microcomputer 10 includes:
The well-known graph of the relationship between ambient temperature and saturated steam pressure shown in FIG. 9 is tabulated by function approximation. Therefore, when the indoor temperature Ta and the dew point temperature Td are determined, the microcomputer 10 uses this table to calculate the saturated water vapor pressures Pa and Pd at the indoor temperature Ta and the dew point temperature Td.
You can find it.

Since absolute humidity is defined by this saturated water vapor pressure Pd, and relative humidity is defined by Pd/Pa, all humidity values can be found by calculation (step 113).
.

The microcomputer 10 inputs dew point temperature Td and absolute humidity Pd via an interface 11 according to the user's needs.
, output relative humidity P d / Pa to external device (
Step 114).

In the steps of the above flowchart, a method has been shown in which the cooling current is gradually decreased by N% from the maximum value, and after the dew condensation phenomenon disappears, the cooling current is gradually increased by M% to achieve the dew point. Then, find the large dew point temperature by setting the value of N to be smaller than the value of M, and then fine-tune (
Responsiveness by finding accurate dew point temperature? However, the cooling current may be slowly decreased from the maximum value from the beginning, and the temperature data at the time when dew condensation occurs may be used as the dew point temperature. Furthermore, the cooling current may be increased from the minimum value or it may be effectively changed by changing the duty ratio.

FIG. 9 is a flowchart of a timer interrupt, and the interrupt synchronization is set to a time shorter than the humidity change, for example, 5 seconds. At the time of the interrupt, the microcomputer 10 jumps from the main routine of FIG. 8 to the interrupt routine of FIG. 13, and calculates the power consumption PPL from the current IPL and voltage Vpt supplied to the Beltier cooling means 2 (step 121). ). Next, this power consumption and the total target power PT, that is, the power consumption PP of the Beltier cooling means 2
The difference between L and the sum (constant value) of the power consumption of the room temperature detection circuit 9, that is, the power PH to be supplied to the heat generating means 13 is calculated (step 122). And from this electric power, the heating means 13
Calculate the current IH to (step 123). As a result, the current II is supplied from the current supply circuit 5 to the heating means 13, and its value is updated (step 124). Then, the interrupt timer is set again, which causes the program to start (step 125) L and return to the main routine, but after a predetermined period of time has elapsed, the timer interrupt routine is entered.

Further, in the above embodiment, two electrodes 33 facing each other were used as water droplet detection means, but a moisture sensing element, for example, Zn3 (P
O4)2, Zns (PO4)2 and LiPO4 may also be used.

Furthermore, since it can be manufactured using so-called IC technology, by using a silicon wafer with integrated electronic circuits as the substrate, signal pre-processing functions and the like can be integrated, making it possible to create an intelligent device.

"Effect" As described above, this invention integrates a Peltier element and a heating resistor on a substrate, and arranges the heating resistor so that the sum of the power consumption of the Peltier element and the power consumption of the heating resistor is always a constant value. Since it is controlled, the temperature rise value of the substrate of the thin film cooling element is constant.

If a thermocouple is used to detect the temperature of water droplets in the cooling section of the mata-peltier element, and an output is obtained according to the temperature difference between the substrate temperature and the water droplet temperature, the temperature increase value relative to the room temperature of the board will be constant, so the temperature rise from room temperature to the water droplet temperature will be can be obtained with precision.

Furthermore, if a resistance temperature detector is integrated on a substrate, the temperature rise value of the substrate relative to room temperature will be constant, so room temperature can be determined with high accuracy. Relative humidity can be obtained with high accuracy from

[Brief explanation of the drawing]

1 and 2 are both perspective views of a humidity detection element which is an embodiment of the thin film cooling element of the present invention during manufacture, and FIG. 3 is a cross-sectional view of an embodiment of the invention during manufacture. 4 is a schematic sectional view showing an embodiment of the present invention, FIGS. 5 and 6 are perspective views showing another method of forming a recessed portion of a substrate, and FIG. 7 is a schematic sectional view showing an embodiment of the invention. A block diagram when the humidity detection element is actually used as a dew point hygrometer, Fig. 8 is a flowchart showing the operation of the microcomputer, Fig. 9 is a timer interrupt float...humidity detection element, 2... Peltier Cooling means, 3.33...
Water drop detection means, 4... Cooling temperature detection means, 5... Room temperature detection means, 6... Current generation circuit, 7... Water drop detection circuit, 8... Temperature difference detection circuit, 9... Room temperature detection circuit, 10... Microcomputer, 11... Incoface, 12... Bus, 13... Heat generating means, 1
5... Current generating circuit, 20... Substrate, 21... Recess, 22... Insulating layer, 23... Through hole, 24...
first Peltier metal, 25... second Peltier metal,
26... First joint group, 27... Second bond group, 28... First thermocouple metal, 29... 20th thermocouple metal, 30... Temperature sensing part , 32... resistance temperature sensor, 3
4...) Kurad, 35... Pad, 36... Pad, 50... Heating resistor, 55... Pad. Patent applicant: Yamatake Newell Co., Ltd. Figure 5 Figure 6 Figure 7 Figure 10 Figure 11' -3X JI

Claims (4)

[Claims] (1) A Peltier element and a heating resistor are integrated into a thin film, and the current supplied to the Peltier element is controlled so as to generate water droplets at the heat-absorbing junction of the Peltier element, and the heat-absorbing element is heated at the time when the water droplets are generated. The temperature near the joint and the room temperature are measured, and the humidity is determined from both temperatures.The temperature of the heat generating resistor is measured so that the sum of the power consumption of the Peltier element and the power consumption of the heat generating resistor is always constant. 1. A method for controlling a thin film cooling element, comprising controlling an applied voltage or a supplied current. (2) A Peltier element and a heating resistor are integrated into a thin film, and the current supplied to the Peltier element is controlled so that water droplets are generated at the endothermic junction of the Peltier element, and the endothermic junction is made at the time when the water droplets are generated. Measure the temperature near the part and the room temperature, calculate the humidity from both temperatures, and make sure that the integral value of the sum of the power consumption of the Peltier element and the power consumption of the heating resistor over a predetermined time always remains a constant value. A method for controlling a thin film cooling element, comprising controlling the heating resistor. (3) A Peltier element and a heating resistor are integrated in a thin film form on a substrate, and a bonding portion having an endothermic effect is arranged in the center of the substrate among the bonding portions of the Peltier element, and the substrate A thin film cooling element in which a portion corresponding to a joint portion having an endothermic action of the Peltier element is removed. (4) A Peltier element, a temperature sensing resistor for detecting room temperature, and a heat generating resistor are integrated in a thin film on a substrate, and among the joints of the Peltier element, a joint having an endothermic action is placed in the center of the substrate. A thin film cooling element disposed in the substrate, wherein a portion of the substrate corresponding to a joint portion having an endothermic action of the Peltier element is removed.