JPH07202322A - Thermistor - Google Patents

Abstract

PURPOSE:To simultaneously insure improvement in reliability of a thermistor element and highly accurate temperature control of a semiconductor laser when a thermistor is used to operate a semiconductor laser module. CONSTITUTION:In a thermistor 14, a semiconductor laser 1 is placed on a spacer 13 on an upper face of a heat sink 12 equipped with a thermistor element 3 for detecting temperature of the semiconductor laser 1. Thus heat resistance to the semiconductor laser 1 and the thermistor element 3 with respect to an electronic cooling element 7 is approximately equal to each other. Since therefore a temperature change of the semiconductor laser 1 can be correctly detected, temperature control of the semiconductor laser 1 can be done accurately. In addition, the thermistor element 3 is sealed by glass. Therefore no increase in a resistance value may occur due to peeling of the thermistor 3 from an electrode 5 due to a change with time, thereby improving reliability of the thermistor element 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermistor mounted inside a semiconductor laser module used for optical communication or optical information processing.

2. Description of the Related Art Oscillation conditions such as an oscillation wavelength and a light output of a semiconductor laser change with temperature. Therefore, in the semiconductor laser module used for the optical fiber transmission device,
It is necessary to control the temperature of the semiconductor laser because of stable oscillation conditions for stable signal transmission. In such a semiconductor laser module, the temperature of the semiconductor laser is controlled using a control circuit that controls the electronic cooling element based on the temperature detection result of the thermistor that detects the temperature of the semiconductor laser. FIG. 2 is a perspective view showing the structure of the temperature control portion of a semiconductor laser module using a conventional thermistor. The semiconductor laser module includes a semiconductor laser 1 for emitting a laser beam and a heat sink 2 for fixing the semiconductor laser 1.
A thermistor element body 3 sealed with glass, which is a temperature sensor for detecting the temperature of the semiconductor laser 1, a substrate 4 on which the thermistor element body is installed, an electrode 5 formed on the upper surface of the substrate 4, It comprises a substrate 4 and a thermistor 6 including the thermistor body 3 placed on the substrate 4, and an electronic cooling element 7 for cooling the semiconductor laser 1. The semiconductor laser 1 is installed on the heat sink 2, and the thermistor body 3 is installed on another substrate 4. Therefore, when the heat sink 2 on which the semiconductor laser 1 is installed and the thermistor 6 are installed on the electronic cooling element 7, the heat conduction paths from the electronic cooling element 7 to the semiconductor laser 1 and the thermistor element body 3 are different from each other. There is a difference in resistance. Therefore, the temperature change of the semiconductor laser 1 cannot be accurately monitored. As a result, there is a problem that the temperature of the semiconductor laser 1 cannot be controlled accurately.
Regarding the structure of the temperature control part of such a semiconductor laser module, refer to Nakagawa et al. "LD Module with Cooling Element with Excellent Frequency Response", 1988 National Conference of IEICE, C-450, pages 1-555. Is shown in. FIG. 3 is a perspective view showing the structure of the temperature control portion of the semiconductor laser module which is improved so that the semiconductor laser 1 can be temperature-controlled with high accuracy. The structure of FIG. 3 has a heat sink 8 for fixing the semiconductor laser 1, a thermistor 9 which is a temperature sensor for detecting the temperature of the semiconductor laser 1, a stem 10 for fixing the thermistor 9, and both sides of the thermistor 9. It has a metallized electrode 11. The stem 10 is installed on the electronic cooling element 7, the thermistor 9 is installed on the stem 10, the heat sink 8 is installed on the thermistor 9, and the semiconductor laser 1 is installed on the heat sink 8. Therefore, by installing the thermistor 9 between the semiconductor laser 1 and the electronic cooling element 7, the heat generated by the semiconductor laser 1 passes through the heat sink 8 and then the upper surface of the electronic cooling element 7 as in the case of FIG. , And flows directly into the thermistor 9 without going through the substrate 4.
Therefore, unlike the case of FIG. 2, a temperature difference proportional to the thermal resistance does not occur due to heat passing through the upper surface of the electronic cooling element 7 and the substrate 4. The structure of the temperature control part of such a semiconductor laser module is described in the document (Japanese Patent Laid-Open No. 61-131580).

In the structure of the temperature control portion of the semiconductor laser module using the conventional thermistor 9, the bare thermistor 9 is used.
Such a thermistor 9 has a reliability problem such that the metallized electrodes 11 on the upper and lower sides of the thermistor 9 are peeled off with time and the resistance value is increased. The thermistor 6 shown in FIG. 2 solves this reliability problem. By sealing the thermistor body 3 with glass, the reliability of the thermistor body 3 is improved. However, unlike the bare thermistor 9, it is not possible to form the upper and lower metallized electrodes 11, so that the temperature control portion of the semiconductor laser module as shown in FIG. There was a problem that I could not do it. It is an object of the present invention to provide a thermistor which eliminates the above mentioned drawbacks.

To achieve the above object, in a thermistor according to the present invention, a semiconductor laser and a thermistor element body sealed with glass are placed on the same surface of a heat sink.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of the thermistor according to the present invention. The thermistor element body 3 for detecting the temperature of the semiconductor laser 1 is installed on a heat sink 12 different from the heat sink 8 of FIG. The material of the heat sink 12 is A1N (aluminum nitride ceramics)
Is. The semiconductor laser 1 is installed in a space 13 provided in a heat sink 12 in which the thermistor body 3 is installed. The thermistor 14, which is composed of the heat sink 12, the thermistor body 3, the electrode 5, and the space 13, is installed on the electronic cooling element 7. The semiconductor laser 1 and the thermistor body 3 can be installed on the same surface of the same heat sink 12 and closer to the thermistor body 3. Therefore, the semiconductor laser 1 and the thermistor element body 3 have the same thermal resistance as viewed from the electronic cooling element 7,
The thermistor body 3 can accurately detect the temperature of the semiconductor laser 1 viewed from the electronic cooling element 7. For this reason,
The temperature of the semiconductor laser 1 can be accurately controlled. The thermistor 14, unlike the bare thermistor 9 shown in FIG. 3, has the entire thermistor element body 3 and the portion of the electrode 5 in contact with the thermistor element body 3 sealed with gas. Therefore, in the thermistor 14, the resistance value does not increase due to the thermistor element body 3 and the electrode 5 peeling off with time, and the reliability of the thermistor element body 3 is improved. The heat sink 12 may be T-cBN (cubic type boron nitride) instead of A1N (aluminum nitride ceramics).

As described above, in the thermistor according to the present invention, the semiconductor laser can be installed in the vicinity of the thermistor element body which is the temperature sensor portion and on the same surface of the same heat sink. The temperature of the laser can be accurately detected, and the temperature of the semiconductor laser can be accurately controlled. Further, by sealing the thermistor body with glass, the reliability of the thermistor body is improved. Therefore, using the thermistor according to the present invention,
The reliability of the thermistor element can be improved and the temperature of the semiconductor laser can be controlled with high accuracy.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a thermistor according to the present invention.

FIG. 2 is a perspective view showing a configuration of a temperature control portion of a semiconductor laser module using a conventional thermistor.

FIG. 3 is a perspective view showing another configuration of a temperature control portion of a semiconductor laser module using a conventional thermistor.

[Explanation of symbols]

 1 Semiconductor Laser 2 Heat Sink 3 Thermistor Element 4 Substrate 5 Electrode 6 Thermistor 7 Thermoelectric Cooling Element 8 Heat Sink 9 Thermistor 10 Stem 11 Electrode 12 Heat Sink 13 Space 14 Thermistor

Claims (5)

[Claims] 1. A thermistor comprising a heat sink substrate and a thermistor element body provided on the heat sink substrate, wherein a space for placing an object to be temperature controlled is provided on the heat sink substrate. 2. The thermistor according to claim 1, wherein the temperature controlled object is a semiconductor laser. 3. The thermistor according to claim 1, wherein the thermistor body is sealed with glass. 4. The heat sink material is T-cBN.
(Cubic-type boron nitride).
The thermistor shown. 5. The thermistor according to claim 1, wherein the material of the heat sink is A1N (aluminum nitride ceramics).