Thermal measuring and testing – Temperature measurement – By electrical or magnetic heat sensor
Reexamination Certificate
2000-11-30
2002-10-15
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Temperature measurement
By electrical or magnetic heat sensor
C136S233000
Reexamination Certificate
active
06464393
ABSTRACT:
BACKGROUND OF THE INVENTON
1. Field of the Invention
This invention relates to an improvement of a surface temperature sensor head. A laser diode (LD) is one of the most important key devices of optical communication systems.
This invention claims the priority of Japanese Patent Application No.11-344569 (344569/1999) filed Dec. 3, 1999 which is incorporated herein by reference.
Since high density current flows in a tiny LD chip, the current produces large heat in the laser diode. The large heat raises the temperature of the LD chip. The high temperature deteriorates the properties and decreases the reliability of the LD. Further, the large heat changes the oscillation frequency of the LD or shortens the lifetime of the LD. Thermal analysis on the LDs has been energetically carried out for enhancing the property and the efficiency of LDs.
The multiwavelength transmission technology attracts attention. Application of LDs to the light source of the multiwavelength transmission requires more rigorous temperature control of the LDs, because the change of the temperature varies the oscillation frequency of the LDs. The change of the oscillation frequency also varies the performance of wavelength division multiplexers (WDMs) and the sensitivity of photodetecting devices. The temperature of the LD should be controlled for prohibiting the oscillation frequency from changing. Enhancement of the importance of the temperature control requires further progress of thermal analysis technology for measuring the temperature distribution in a tiny LD chip.
General semiconductor devices, for example, LSIs, tend to pursue the higher speed and larger data capacity. However, increasing heat generation prevents the semiconductor devices from accomplishing the higher speed and higher data capacity. A further development of the LSIs requires the progress of the thermal analysis technology.
Inspection and examination of LSIs request the technology which enables the operators to carry out electric measurements and the thermal measurements simultaneously at a high speed.
The present invention aims at answering the requests for improved thermal analysis technology. The present invention proposes a surface temperature sensor head available for the thermal analysis or inspection of the LDs, LSIs or other electronic devices. This invention will serve a sensor head of a non-destructive temperature probe for seeking temperature distribution by measuring temperature. at a plurality of small spots of an object without breaking the object.
2. Description of Related Art
The thermal analysis technology investigates spatial temperature distribution of an object by various means. The measuring of temperature requires temperature sensors. There are various kinds of temperature sensors, for example, thermocouples, thermistors, radiation thermometers and so on. The temperature sensors measure temperature on different bases.
The thermocouple is a sensor which makes use of the voltage thermally induced at the junction which is proportional to the temperature difference between two joints of two different metal wires. Since the thermocouple utilizes thermoelectromotive force, the temperature of an object is measured by fixing a tip (unction of two metals) of the thermocouple tightly to a spot of the object with a paste or silver solder of good thermal conductivity. Since the tip.should be tightly in contact with the object, the paste or solder fixes the tip on a surface of the object. The paste fixation forbids the thermocouple to move the tip. It is difficult for the thermocouple to measure temperature at a plurality of spots on an object because of the difficulty of moving the tip. The modes of measurement are restricted by the fact that the tip should be tightly touched to the object.
Some other sensors make use of the change of electric resistance depending upon temperature. They are a thermistor thermometer and a platinum thermometer resistor. The thermistor should also be fixed to an object by paste or solder for maintaining a tight contact between the sensor and object. The difficulty of moving a sensing part accompanies the thermistors.
A micro-radiation thermometer is a sensor which measures temperature at many points of an object and displays the temperature distribution on an image. Radiation power from a heated object is determined by Rayleigh-Jeans' Law. The peak wavelength of the radiation is proportional to an inverse of the absolute temperature of the object. The whole radiation per a unit area is in proportion to a quadruple of the absolute temperature by Stefan-Boltzmann's Law. The radiation thermometer measures the temperature or temperature distribution on a surface by the wavelength distribution and the total power of infrared radiation from the surface of the object. Unlike the thermocouples or thermistors, the radiation thermometer is a non-contact type sensor. The non-contactness enables the radiation thermometer to measure the temperature of an object from a remote spot. The radiation thermometer can obtain spatial temperature distribution by changing the directions for measuring the radiation on the object.
The purpose of the present invention is to obtain exact temperature distribution on a small device, for example, an LD, an LSI or so. Prior art which aimed at a similar purpose should be described.
{circle around (1)} Japanese Patent Laying Open No.4-191626 (191626/'92) “Surface temperature measuring sensor” tried to measure the exact temperature of an object by making use of a sheathed thermocouple and a copper disc. The tip of the sheathed thermocouple is fixed in the copper disc. The sensor measures the temperature of an object by boring a hole on the object and inserting the copper disc having the sheathed thermocouple into the hole.
The object is heat exchangers, steam turbines, reaction furnaces and so on. The reason why the thermocouple is sheathed by an insulator is that the thermocouple must be insulated from the metal objects. The reason why the copper disc is fixed to the tip of the thermocouple is that the temperature of the object can be measured exactly and speedy by maintaining a tight and stable contact with the object. It takes only a short time. for the object to attain thermal equilibrium with the copper disc having a high thermal conductivity and large heat capacitance. The sensor measures the temperature of the copper disc which keeps the thermal equilibrium with the object.
If the tip of the thermocouple is bluntly pushed to the object without the copper disc, unstable air gaps existing between the tip and object suppress heat conduction, inhibit thermal equilibrium and forbid the sensor to measure the exact temperature of the object. The copper disc helps the sensor of {circle around (1)} to shield noise and measure the exact temperature of the object.
In the examination of LSIs, the properties should be tested for the LSIs in a regularly driven and thermally controlled state. LSI examinations often use a “probe-card type” prober having plenty of probing needles which can come into simultaneous contact with all the electrode pads on the object LSI. The examination apparatus measures the properties and characters of the LSIs by bringing all the needles of the probe-card type prober into the counterpart electrode pads of the LSI in the thermally controlled state.
The temperature control requires a couple of a heater and a temperature sensor. In general, a thermocouple is fitted on a susceptor for sustaining a wafer as a substrate for producing LSIs for protecting the wafer from contamination. The LSI testing apparatus measures the properties and characteristics by monitoring the temperature of an object LSI by the thermocouple, maintaining the LSI at a predetermined temperature by the heater, supplying the object LSI with driving currents, source and ground voltages and input signals and monitoring output currents, output voltages and output signals.
{circle around (2)} Japanese Patent Laying Open No.4-359445 (359445/'92), “Heat testing probing apparatu
Gutierrez Diego
Jagan Mirellys
McDermott & Will & Emery
Sumitomo Electric Industries Ltd.
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