Abstract:
An object is heated to a preheating temperature in an atmosphere of a reducing gas under the atmospheric pressure while adjusting the setting of the emissivity of a non-contact temperature measuring part and regulating the temperature of the object according to the measured value measured by a contact temperature measuring part. The pressure of the atmosphere is reduced. The object is further heated to a heating temperature under a lowered pressure while regulating the temperature of the object according to the measured value measured by the non-contact temperature measuring part whose setting of the emissivity is adjusted during the heating process to the preheating temperature. The pressure of the atmosphere is increased back to the atmospheric pressure while maintaining the heating temperature of the object. The temperature of the object is decreased under the atmospheric pressure. With this, in the process of heating an object under a lowered pressure, the actual temperature of the object is managed over the whole steps, and the object can be most suitably heated according to the actual temperature.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a heating technique for heating an object under lowered pressure. For example, the present invention relates to a heater for solder joining a board and an electronic product under lowered pressure and a heating method thereof. Furthermore, the present invention relates to a method of manufacturing an electronic product by the heater. 
       BACKGROUND ART 
       [0002]    As a method of manufacturing an electronic product to be manufactured by solder joining a first joining member (e.g. a substrate) and a second joining member (e.g. an electronic component), there is a method achieved by supplying solder to the first joining member, placing the second joining member thereon, and heating them to be soldered to each other in a heater. In this solder joining using such heating method, however, holes (hereinafter, referred to as voids) may be generated in a solder joint portion. The presence of the voids may cause peeling of the joint portion or a decrease in heat conduction efficiency from the second joining member (the electronic component) to the first joining member (the substrate). 
         [0003]    To avoid a deterioration in product quantity resulting from the voids, therefore, a decompressing type heater for solder joining under lowered pressure is sometimes used. Even if gas is taken in the solder and voids are generated under lowered pressure, the voids are contracted when the atmosphere is returned to atmospheric pressure by supply of inert gas or the like. A method of manufacturing an electronic product by solder joining under lowered pressure is disclosed in Patent Literature 1. 
       CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP2005-205418A 
     SUMMARY OF INVENTION 
     Technical Problem 
       [0004]    Meanwhile, in the manufacturing of an electronic product by the decompressing type heater, a heater temperature and others in a furnace are controlled to ensure the quality of the electronic product to be manufactured. This is because the characteristics of the electronic product tend to change if the temperature of the electronic product becomes too high and, on the other hand, appropriate solder joining could not be performed if the temperature of solder is insufficient. To ensure the characteristics of the electronic product and the solder joining, it is therefore preferable to ascertain the actual temperature of an object rather than the atmospheric temperature. 
         [0005]    However, in the method of manufacturing the electronic product by the decompressing type heater, it is hard to accurately measure the temperature of the object because the pressure in the heater changes. This is because, in the case of measuring the temperature of the object by use of a contact thermometer as shown in  FIG. 1 , a gap exists between the object and the contact thermometer as shown in  FIG. 2  (an enlarged view of a region II in  FIG. 1 ). 
         [0006]    This causes the following problem under lowered pressure. As atmospheric gas in the gap is reduced in pressure, the thermal conductivity of the gap decreases and changes. Accordingly, a difference (deviation) is caused between the actual temperature of the object and the temperature measured by the contact thermometer. By this change in thermal conductivity, the temperature measured by the contact thermometer is lower than the actual temperature of the object. Thus, when a heating condition of the object is controlled based on a measured value of the contact thermometer, the temperature of the object would increase more than a target value. 
         [0007]    On the other hand, even by the use of a radiation thermometer, it is difficult to accurately measure the temperature of the object by the radiation thermometer alone. Because the object is heated to a temperature (a pre-heating target temperature) lower than the solidus of solder under atmospheric pressure and then the temperature is kept for a while for pre-heating, and the surface of the object is deoxidized and cleaned by the pre-heating in a reducing gas. Accordingly, the surface condition of the object is changed. If the emissivity of the radiation thermometer is set in correspondence with the object before cleaning, the measured temperature diverges from the actual temperature of the object as the surface condition of the object changes. That is, when the pressure and the surface condition of the object change, the temperature of the object could not be measured accurately even if the contact thermometer or the radiation thermometer is used singularly. 
         [0008]    The present invention has been made to solve the above problems of the prior arts and has a purpose to provide a decompressing type heater and a heating method thereof capable of controlling an actual temperature of an object in all the steps of heating the object under lowered pressure to heat the object appropriately based on the actual temperature, and a method of manufacturing an electronic product by solder joining using the heater and the heating method. 
       Solution to Problem 
       [0009]    A decompressing type heater of the present invention made to achieve the above purpose is decompressing type heater having a heat treatment chamber formed with an outlet port, the heater being configured to pre-heat an object placed in the heat treatment chamber to a pre-heating temperature under atmospheric pressure and heat the object to a higher temperature than the pre-heating temperature under lowered pressure, the heater comprising: a heater for heating the object in the heat treatment chamber; a contact temperature measuring part for measuring the temperature of the object in contact relation therewith in the heat treatment chamber; a non-contact temperature measuring part for measuring the temperature of the object in non-contact relation therewith in the heat treatment chamber; and a controlling part for controlling the heater and adjusting the non-contact temperature measuring part, the controlling part being adapted to adjust the non-contact temperature measuring part to eliminate a difference of a measured value of the non-contact temperature measuring part with respect to a measured value of the contact temperature measuring part during pre-heating under atmospheric pressure, and to control the heater based on the measured value of the adjusted non-contact temperature measuring part during heat treatment under lowered pressure. The above decompressing type heater can accurately measure the temperature of the object to be heated under lowered pressure as well as under atmospheric pressure, and performs heat treatment of the object under accurate temperature control based on the actual temperature of the object. 
         [0010]    In the aforementioned decompressing type heater, preferably, the non-contact temperature measuring part is a radiation thermometer for detecting infrared rays emitted from the object to be heated, and the controlling part adjusts setting of emissivity in the radiation thermometer during the pre-heating under atmospheric pressure. This can accurately measure the temperature of the object even under lowered pressure. 
         [0011]    In the aforementioned decompressing type heater, preferably, the non-contact temperature measuring part is a radiation thermometer for detecting infrared rays emitted from the object to be heated, and the controlling part adjusts a correction coefficient of an output value of the radiation thermometer during the pre-heating under atmospheric pressure. This can accurately measure the actual temperature of the object as above. 
         [0012]    In the aforementioned decompressing type heater, preferably, the heat treatment chamber is formed with a gas inlet port, and the pre-heating under atmospheric pressure is performed while a reducing atmospheric gas is supplied into the heat treatment chamber. Accordingly, the deoxidizing reaction occurs in the surface of the object, thereby cleaning the surface. 
         [0013]    In the aforementioned decompressing type heater, preferably, the heater includes a gas supplying unit for supplying atmospheric gas into the heat treatment chamber through the gas inlet port. Thus, a reducing atmospheric gas can be fed into the heat treatment chamber. 
         [0014]    The aforementioned decompressing type heater, preferably, further includes an exhausting unit connected to the outlet port to discharge gas from the heat treatment chamber to lower internal pressure. This makes it possible to lower the pressure in the heat treatment chamber. 
         [0015]    Furthermore, a heating method of the present invention is a method of heating an object under temperature control using a contact temperature measuring part and a non-contact temperature measuring part, the method comprising: heating the object to a pre-heating temperature lower than a heat treatment temperature in an atmosphere of deoxidizing gas under atmospheric pressure while adjusting setting of emissivity in the non-contact temperature measuring part based on a measured value of the contact temperature measuring part and controlling the temperature of the object, and further heating the object to the heat treatment temperature under lowered pressure while controlling the temperature of the object based on a measured value of the non-contact temperature measuring part having the setting of emissivity adjusted in the process of heating to the pre-heating temperature. This method can heat the object while strictly controlling the temperature thereof without being affected by changes in atmospheric pressure and cleaning of the object. 
         [0016]    Moreover, a method of manufacturing an electronic product of the present invention is A method of manufacturing an electronic product by heating an object including a plurality of members to be joined under lowered pressure to solder join them, the method comprising: heating the object to a pre-heating temperature at which solder does not melt in an atmosphere of deoxidizing gas under atmospheric pressure while adjusting setting of emissivity in the non-contact temperature measuring part based on a measured value of the contact temperature measuring part and controlling the temperature of the object; lowering pressure; further heating the object to the heat treatment temperature under lowered pressure while controlling the temperature of the object based on a measured value of the non-contact temperature measuring part having the setting of emissivity adjusted in the process of heating to the pre-heating temperature; returning the pressure of the atmosphere to the atmospheric pressure while maintaining the heat treatment temperature of the object; and solidifying the solder under the atmospheric pressure to solder join the object. This manufacturing method of an electronic product can solder join the object while strictly controlling the temperature of the object to be solder joined. Furthermore, this is unlikely to generate voids in the solder. It is further possible to prevent changes in the characteristics of the electronic product. 
       ADVANTAGEOUS EFFECTS OF INVENTION 
       [0017]    According to the present invention, there are provided a decompressing type heater and a heating method thereof capable of controlling an actual temperature of an object in all the steps of heating the object under lowered pressure to heat the object appropriately based on the actual temperature, and a method of manufacturing an electronic product by solder joining using the heater and the heating method. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0018]      FIG. 1  is a view (Part  1 ) to explain a contact temperature measuring part during measurement; 
           [0019]      FIG. 2  is a view (Part  2 ) to explain the contact temperature measuring part during measurement; 
           [0020]      FIG. 3  is a view to explain a configuration of a decompressing type heater according to the present invention; 
           [0021]      FIG. 4  is a view to explain the decompressing type heater during heating according to the present invention; 
           [0022]      FIG. 5  is a graph to explain a method of manufacturing an electronic product by use of the decompressing type heater according to the present invention; 
           [0023]      FIG. 6  is a block diagram to explain a temperature controlling method employed in the decompressing type heater according to the present invention; 
           [0024]      FIG. 7  is a graph to explain the temperature controlling method in the method of manufacturing the electronic product by the decompressing type heater according to the present invention; 
           [0025]      FIG. 8  is a graph to explain a temperature controlling method in a method of manufacturing an electronic product by a decompressing type heater in a prior art; and 
           [0026]      FIG. 9  is a block diagram to explain another example of the temperature controlling method employed in the decompressing type heater according to the present invention. 
       
    
    
     REFERENCE SIGNS LIST 
       [0000]    
       
           10  Substrate 
           20  Electronic component 
           30  Solder 
           100  Decompressing type heater 
           110  Contact temperature measuring part 
           112  Temperature indicator 
           120  Radiation thermometer 
           121  Radiation thermometer controller 
           130  Heater 
           140  Inlet port 
           150  Outlet port 
           170  Heater controller 
           180  Control part 
           190  Chamber 
           200  Temperature controlling system 
           340  Gas supply unit 
           350  Exhaust unit 
       
     
       DESCRIPTION OF EMBODIMENTS 
       [0044]    A detailed description of a preferred embodiment of the present invention will now be given referring to the accompanying drawings. This embodiment embodies the present invention about a decompressing type heater, a heating method thereof, and a method of manufacturing an electronic product by using them. 
         [0045]    The decompressing type heater is first explained below. As shown in  FIG. 3 , a decompressing type heater  100  includes an inlet port  140 , an outlet port  150 , a contact temperature measuring part  110 , a radiation thermometer  120 , a heater  130 , a cylinder  131 , a quartz window  160 , and a chamber  190 . 
         [0046]    The decompressing type heater  100  is arranged to perform heat treatment of an object to be heated in the chamber  190 . The chamber  190  is a heat treatment chamber which is air-tightly closed during heat treatment and the internal atmosphere is replaced through the outlet port  150  and the inlet port  140  for atmosphere replacement. Furthermore, the chamber  190  is configured to be controllable of the internal pressure thereof. Specifically, the pressure in the chamber  190  is lowered by discharging gas through the outlet port  150  and returned to atmospheric pressure by taking in gas through the inlet port  140 . In use, the outlet port  150  is connected to an exhaust unit  350  such as a vacuum pump and the inlet port  140  is connected to a gas supply unit  340  for supplying reducing gas, inert gas, or the like. 
         [0047]    An example of using the decompressing type heater  100  for solder joining is explained referring to  FIG. 4 . The heater  100  is configured as above to heat a substrate  10 , an electronic component  20 , and solder  30  placed therein under lowered pressure, thereby melting the solder  30  and joining the substrate  10  and the electronic component  20 . 
         [0048]    The heater  130  serves to heat the substrate  10  in contact relation therewith. The cylinder  131  is a lifting mechanism for moving the heater  130  up and down. The lifting mechanism may be not only the cylinder but also any mechanism capable of moving up and down a table-like member to be lifted. The lifting mechanism may be connected to the contact temperature measuring part  110  instead of the heater  130 . The contact temperature measuring part  110  is placed in contact with a portion of the substrate  10  to measure a temperature of the contact portion. At a leading end of the contact temperature measuring part  110 , there is a gap from the object as shown in  FIG. 2 . The radiation thermometer  120  is a non-contact temperature measuring part using infrared rays to measure the surface temperature of the substrate  10  in non-contact relation therewith. The quartz window  160  is a window provided to allow the radiation thermometer  120  to detect the infrared rays emitted from the substrate  10 . Herein, the non-contact temperature measuring part is not limited to the type using infrared rays and may be any non-contact temperature sensor if only a temperature error occurs between an actual temperature and a measured temperature as the surface condition of the substrate  10  changes before and after pre-heating mentioned later. 
         [0049]    The method of manufacturing the electronic product by use of the decompressing type heater  100  is explained below referring to  FIGS. 4 and 5 . The electronic product manufacturing method in this embodiment includes two-stage heating. In a first heating step (a pre-heating step), the substrate  10  is heated under atmospheric pressure to a pre-heating target temperature in a mixed gas atmosphere of inert gas and reducing gas. During this pre-heating, the surface of wiring on the substrate  10  is deoxidized and hence wettability to the solder  30  is increased. Thus, appropriate solder joining can be achieved. Then, the pressure is decreased to a pressure P 1  (e.g. 10 kPa or lower) while the pre-heating target temperature is maintained. 
         [0050]    A second heating step is performed under lowered pressure, because solder joining under lowered pressure prevents the generation of voids. Even if voids appear under lowered pressure, the voids should contract when the internal pressure of the decompressing type heater  100  is returned to atmospheric pressure. After this heating, the internal pressure of the heater  100  is returned to atmospheric pressure and then the temperature is decreased to solidify the solder  30 . 
         [0051]    Herein, the pre-heating target temperature of the substrate  10  is a target temperature in the first heating step to pre-heat the substrate  10  and thus is set lower than a solidus temperature of the solder  30  in order to prevent the solder  30  from starting to melt. A final target temperature of the substrate  10  is set higher than a liquidus temperature of the solder  30  in order to sufficiently melt the solder  30  to spread in a wet state. However, it must not exceed an upper temperature limit of the electronic component  20 . The solidus temperature of the solder  30  used herein is about 235° C. and the liquidus temperature of the solder  30  is about 240° C. 
         [0052]    An object, i.e., the substrate  10  on which the solder  30  and the electronic component  20  are placed, is first put in the decompressing type heater  100 . The object is set on the heater  130 . After that, a mixture of inert gas such as nitrogen and reducing gas such as hydrogen is supplied into the heater  100 . The internal pressure of the heater  100  after atmosphere replacement is almost equal to atmospheric pressure. 
         [0053]    The heater  130  is then moved up by the cylinder  131 . When the substrate  10  comes into contact with the contact temperature measuring part  110 , the upward movement of the heater  130  is stopped. 
         [0054]    (Time t 0 ) 
         [0055]    Then, the first heating step is performed. The time at which the heater  130  starts to heat the substrate  10  is referred to as t 0 . 
         [0056]    (Time t 0  to t 1 ) 
         [0057]    After time t 0 , the substrate  10  is heated by the heater  130  under atmospheric pressure. The solder  30  and the electronic component  20  are heated through the substrate  10 . Since the atmosphere has been replaced with the reducing gas, the heating during this period causes a deoxidization reaction at the oxidized surfaces of the substrate  10 , solder  30 , and electronic component  20 . By this cleaning, the surface wettability of the substrate  10  with respect to the solder  30  is enhanced. 
         [0058]    (Time t 1 ) 
         [0059]    The time at which the substrate  10  reaches the pre-heating target temperature is referred to as t 1 . At that time, the solder  30  does not reach the solidus temperature and does not melt yet. Furthermore, it is an advanced state of the cleaning of the substrate  10 , solder  30 , and electronic component  20 . 
         [0060]    (Time t 1  to Time t 2 ) 
         [0061]    After time t 1 , the gas is discharged from the heater  100  through the outlet port  150 . Accordingly, the internal pressure of the heater  100  decreases. The temperature of the substrate  10  remains almost equal to the temperature of the substrate  10  at time t 1 . 
         [0062]    (Time t 2 ) 
         [0063]    At the time when the internal pressure of the heater  100  has decreased, the gas discharging through the outlet port  150  is stopped. This time is referred to as t 2 . 
         [0064]    (Time t 2  to Time t 5 ) 
         [0065]    After time t 2 , the second heating step is started. This heating is conducted while the internal pressure of the heater  100  is maintained in a lowered state. 
         [0066]    (Time t 3 ) 
         [0067]    The time at which the temperature of the substrate  10  reaches the solidus temperature of the solder  30  is referred to as t 3 . At this time, the solder  30  and the electronic component  20  should have reached the temperature almost equal to the substrate  10 . Thus, the solder  30  starts to melt. 
         [0068]    (Time t 4 ) 
         [0069]    The time at which the temperature of the substrate  10  reaches the liquidus temperature of the solder  30  is referred to as t 4 . At this time, the solder  30  and the electronic component  20  should have reached the temperature almost equal to the substrate  10 . Thus, almost the entire solder  30  is in a molten state. 
         [0070]    (Time t 5 ) 
         [0071]    The time at which the substrate  10  reaches the final target temperature is referred to as t 5 . At time t 5 , the heating by the heater  130  is stopped. At this time, the solder  30  has completely melted and spread in a wet state. In this state, even if voids have appeared in the solder  30 , the internal pressure of the voids is almost equal to the internal pressure of the heater  100 . 
         [0072]    (Time t 5  to Time t 6 ) 
         [0073]    After time t 5 , inert gas or a mixture of inert gas and reducing gas is supplied little by little into the heater  100  through the inlet port  140  while the temperature of the substrate  10  is maintained constant. Accordingly, the internal pressure of the furnace gradually increases. At this time, the solder  30  remains melted. Even if voids have appeared in the solder  30 , the voids will contract as the internal pressure of the heater  100  increases. 
         [0074]    (Time t 6 ) 
         [0075]    When the internal pressure of the heater  100  becomes almost equal to atmospheric pressure, the gas supply through the inlet port  140  is stopped. This time is referred to as t 6 . At this time, the solder  30  is in a molten state. If voids had appeared in the solder  30  from time t 2  to time t 5 , the voids have already contracted. 
         [0076]    (Time t 6  to Time t 7 ) 
         [0077]    After time t 6 , the temperature of the substrate  10  is decreased while atmospheric pressure is maintained. Thus, the solder  30  is solidified. 
         [0078]    (Time t 7 ) 
         [0079]    The time at which the temperature of the substrate  10  becomes a normal temperature is referred to as t 7 . By this time, the solder  30  has been solidified. Although the time at which the substrate  10  becomes the normal temperature is referred to as t 7  in this embodiment, it is not limited to the normal temperature if only it becomes sufficiently lower than the solidus temperature of the solder  30 . After time t 7 , the substrate  10  is taken out of the decompressing type heater  100 . 
         [0080]    As above, solder joining of the substrate  10  and the electronic component  20  is finished. 
         [0081]    The following explanation is given to a temperature controlling method in the heating process of the decompressing type heater  100  in this embodiment.  FIG. 6  is a block diagram to explain a temperature controlling system  200  of the heater  100 . The temperature controlling system  200  of the heater  100  includes a controlling part  180 , a contact-temperature-measuring-part temperature indicator (“temperature indicator”)  112 , a radiation thermometer controller  121 , and a heater controller  170 . 
         [0082]    The controlling part  180  is configured to control the temperature and the pressure in the decompressing type heater  100  and replace atmosphere thereof. The temperature indicator  112  is used to display the temperature measured by the contact temperature measuring part  110  and transmit temperature data to the controlling part  180 . The radiation thermometer controller  121  is configured to transmit temperature data measured by the radiation thermometer  120  to the controlling part  180 . The heater controller  170  is configured to control output of the heater  130  for heating the substrate  10 . 
         [0083]    The temperature controlling method by the temperature controlling system  200  of the decompressing type heater  100  is explained with reference to  FIG. 7  as well as  FIG. 6 . 
         [0084]    At time t 0 , the contact temperature measuring part  110  is in contact with the substrate  10 . The temperature measuring part  110  measures the temperature of a contact portion with the substrate  10 . The temperature measured by the temperature measuring part  110  is transmitted to the temperature indicator  112 . Then, the temperature measured by the temperature measuring part  110  is further transmitted from the temperature indicator  112  to the controlling part  180 . 
         [0085]    On the other hand, the radiation thermometer  120  also measures the surface temperature of the substrate  10 . The temperature measured by the radiation thermometer  120  is transmitted to the radiation thermometer controller  121 . Then, the temperature measured by the radiation thermometer  120  is further transmitted from the radiation thermometer controller  121  to the controlling part  180 . 
         [0086]    Specifically, the controlling part  180  receives both the temperature of the substrate  10  measured by the contact temperature measuring part  110  and that by the radiation thermometer  120 . 
         [0087]    From time t 0  to time t 1 , pre-heating of the substrate  10  is conducted. Because the deoxidizing atmosphere has been provided, cleaning of the substrate  10  is sufficiently advanced by the pre-heating. This causes a change in emissivity of infrared rays from the surface of the substrate  10 . Therefore the radiation thermometer  120  could not accurately measure the temperature of the substrate  10  with the emissivity setting unchanged from that before cleaning. On the other hand, the internal pressure of the heater  100  is almost equal to atmospheric pressure. The contact temperature measuring part  110  can measure accurate temperature. From time t 0  to time t 1 , accordingly, the controlling part  180  uses values measured by the contact temperature measuring part  110  as the temperature of the substrate  10 . 
         [0088]    For a period from time t 0  to time t 1 , the controlling part  180  adopts the temperature from the contact temperature measuring part  110  while adjusting the setting of the emissivity in the radiation thermometer  120 . The controlling part  180  calculates the emissivity to be set in the radiation thermometer  120  so that the radiation thermometer  120  outputs the temperature equal to the temperature measured by the contact temperature measuring part  110 . 
         [0089]    This calculated emissivity is fed back to the radiation thermometer controller  121 . Thus, the emissivity corresponding to the cleaning of the substrate  10  is newly set in the radiation thermometer  120 . The use of the radiation thermometer  120  having the adjusted emissivity makes it possible to accurately measure the actual temperature of the substrate  10 . After completion of adjustment, the temperature of the cleaned substrate  10  can be measured by the radiation thermometer  120  under either of atmospheric pressure and lowered pressure. 
         [0090]    After time t 1 , the internal pressure of the decompressing type heater  100  decreases. For this period, the temperature measured by the contact temperature measuring part  110  is read as a value lower than the actual temperature of the substrate  10 . This is because there is the aforementioned gap as shown in  FIG. 2  whereby decreases the thermal conductivity of gas. 
         [0091]    After time t 1 , therefore, the temperature of the substrate  10  measured by the radiation thermometer  120  having the adjusted emissivity is adopted instead of the contact temperature measuring part  110 . Based on the temperature measured by the radiation thermometer  120 , the heating condition of the heater  130  is set. Furthermore, the time at which the temperature of the substrate  10  measured by the radiation thermometer  120  reaches the final target temperature is referred to as t 5 . 
         [0092]    At time t 6 , the internal pressure of the decompressing type heater  100  is almost equal to atmospheric pressure. The temperature of the substrate  10  is therefore measured again by the contact temperature measuring part  110 . After time t 6 , the temperature of the substrate  10  may be measured only by the contact temperature measuring part  110 . 
         [0093]    At time t 6 , furthermore, whether or not the temperature of the substrate  10  measured by the radiation thermometer  120  (the measured temperature of the substrate  10  from time t 1  to t 6 ) was accurate can be checked based on the measured value of the contact temperature measuring part  110 . Herein, the following explanation is given to the case where a difference exists between the measured temperature of the contact temperature measuring part  110  and the measured temperature of the radiation thermometer  120  at time t 6 . 
         [0094]    The difference in measured temperature at time t 6  between the contact temperature measuring part  110  and the radiation thermometer  120  is considered to have occurred due to advanced cleaning of the surface of the substrate from time t 1  to time t 6 . However, since the cleaning has remarkably advanced by the pre-heating from time t 0  to time t 1  and the concentration of the reducing gas is low under lowered pressure, this difference in measured temperature should not be so large. 
         [0095]    By further correcting the emissivity of the radiation thermometer  120 , therefore, the temperature of objects can be measured more accurately in next and subsequent heating operations. At time t 6 , the internal pressure of the heater  100  is almost equal to the atmospheric pressure and thus the accurately measured value can be ascertained by the contact temperature measuring part  110 . Accordingly, the emissivity to be set in the radiation thermometer  120  can be determined at time t 6 . Even at time t 1 , on the other hand, the emissivity to be set in the radiation thermometer  120  is determined by the aforementioned temperature control method. No reason is also found why the emissivity rapidly changes in the course from time t 1  to time t 6 . 
         [0096]    Consequently, from time t 1  to time t 6 , the emissivity is gradually changed from the emissivity to be set at time t 1  to the emissivity to be set at time t 6 . Herein, a difference between the emissivity to be set at time t 1  and the emissivity to be set at time t 6  is not so large. 
         [0097]    As above, the setting of the emissivity in the radiation thermometer  120  can be changed to follow the change in emissivity of the substrate  10  from time t 1  to time t 6 . Thus, in the next and subsequent heating operations, objects can be heated based on more accurate temperatures from time t 1  to time t 6 . 
         [0098]    The temperature of the substrate  10  is measured as mentioned above by the contact temperature measuring part  110  from time t 0  to time t 1 , by the radiation thermometer  120  having the adjusted emissivity from time t 1  to time t 6 , and by the temperature measuring part  110  again from time t 6  to time t 7 . Specifically, when the internal pressure of the decompressing type heater  100  is almost equal to atmospheric pressure, the temperature of the substrate  10  measured by the contact temperature measuring part  110  is adopted. While the internal pressure of the heater  100  is lower than atmospheric pressure, the temperature of the substrate  10  measured by the radiation thermometer  120  is adopted. 
         [0099]    The above configurations can realize the decompressing type heater  100  and the heating method thereof capable of measuring the actual temperature of the substrate  10 , feeding it back to the heating condition of the substrate  10 , and solder joining the substrate  10  and the electronic component  20  along an optimum temperature profile, and the method of manufacturing the electronic product by using them. 
         [0100]    For comparison with the present embodiment, the case of controlling the heating condition of the heater  130  based on only the temperature measured by the contact temperature measuring part  110  is explained with reference to  FIG. 8 . For reference, the temperature measured by the radiation thermometer  120  with unadjusted emissivity is also shown in  FIG. 8 . 
         [0101]    When the internal pressure of the decompressing type heater  100  decreases after time t 1 , a difference occurs between the temperature measured by the contact temperature measuring part  110  and the accurate temperature of the substrate  10 . This is because the aforementioned gap exists as shown in  FIG. 2  and the thermal conductivity of gas in the gap decreases by pressure dropping. Accordingly, the temperature of the substrate  10  measured by the contact temperature measuring part  110  is lower than the actual temperature of the substrate  10 . 
         [0102]    Therefore, in the case of performing the temperature control of the decompressing type heater  100  by only the contact temperature measuring part  110 , when it is judged that the temperature of the substrate  10  reaches the final target temperature and the heating of the substrate  10  by the heater  130  is stopped, the actual temperature of the substrate  10  will have exceeded the final target temperature. 
         [0103]    As a result, the temperature of the electronic component  20  may exceed the upper limit temperature, causing characteristics changes. Furthermore, it is impossible to ascertain what degree of temperature the substrate  10  has actually reached at time t 5 . In other words, it is impossible to ascertain what degree of temperature the electronic component  20  has reached. Moreover, there are also variations resulting from repeatability of the contact state of the contact temperature measuring part  110  with the substrate  10 . Such disturbance makes it difficult to control the qualities of products. 
         [0104]    On the other hand, even in the measurement using only the radiation thermometer  120 , the actual temperature of the substrate  10  cannot be measured. It is to be noted that such disadvantage is not caused in this embodiment. 
         [0105]    In the above description, the emissivity of the radiation thermometer  120  is adjusted prior to measurement of the actual temperature of the object to be heated. However, the actual temperature of the object to be heated may also be measured without adjustment of the emissivity of the radiation thermometer  120 . For instance, this corresponds to the case where the controlling part  180  corrects an output value of the temperature of the radiation thermometer  120  having unadjusted emissivity. 
         [0106]    During the pre-heating of the object to be heated from time t 0  to time t 1 , a correction coefficient to correct the output value of the radiation thermometer  120  is determined in advance based on the measured value of the contact temperature measuring part  110  and the measured value of the radiation thermometer  120 . By use of this correction coefficient, the actual temperature of the object to be heated from time t 1  to time t 6  can be measured by the radiation thermometer  120 . This can provide the same effects as in the first embodiment. 
         [0107]    In the decompressing type heater of this embodiment as mentioned in detail above, the contact temperature measuring part and the non-contact temperature measuring part are used together. Specifically, under atmospheric pressure, the substrate is heated based on the temperature of the substrate measured by the contact temperature measuring part and, under lowered pressure, the substrate is heated based on the temperature of the substrate measured by the non-contact temperature measuring part. 
         [0108]    As a result, the substrate can be heated while the temperature of the substrate is controlled in all the steps in correspondence with changes in internal pressure of the heater and changes in the surface condition of the substrate resulting from cleaning. Consequently, the decompressing type heater can be realized capable of restraining the occurrence of voids and solder joining the substrate and the electronic component under strict temperature control. 
         [0109]    It is therefore possible to control the heating based on the actual temperature of the substrate, not based on the temperature of the heater. Furthermore, the actual temperature of the measured substrate also acts as a signal to transfer to a next step. Electronic products with no variations in quality can be manufactured accordingly. Thus, solder-joining to the substrate of a semiconductor device needing an atmosphere replacement step can be performed with high reliability. 
         [0110]    The embodiment is merely an example and does not limit the present invention. Thus, the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. For instance, the objects to be solder joined may be not only the substrate and the electronic component but also a cooling member and the substrate. It is further possible to solder join the cooling member, the substrate, and the electronic component together at once. 
         [0111]    The controlling part  180  may be configured to act as all of the temperature indicator  112 , the radiation thermometer controller  121 , and the heater controller  170 , because the same effects are obtained as above. 
         [0112]    The heater may be not only a contact type but also a lamp heater, an induction coil depending on an object, or hot air. After the solder  30  is melted and the internal pressure of the heater is returned to atmospheric pressure, cooling may be performed in a separate furnace. The liquidus temperature and the solidus temperature of the solder are mere examples and depend on the kind of solder to be used. 
         [0113]    The number of the contact temperature measuring part  110  and the radiation thermometer  120  may be plural. If a large difference between the temperature indicated by the contact temperature measuring part  110  and the temperature indicated by the radiation thermometer  120  at time t 6 , an alarm may also be sounded. Any other than the reducing gas may be used if only it has substantially deoxidizing atmosphere from the viewpoint of the object. It is to be noted that there is also a case where air may be used depending on an object. 
         [0114]    The contact temperature measuring part  110  and the radiation thermometer  120  are preferably placed to measure nearer portions of the substrate  10 , because it is assumed that a difference in actual temperature between measured portions is smaller as the measured portions are nearer. 
         [0115]    Furthermore, the decompressing type heater and the heating method thereof of the present invention are not limited to the purpose of solder joining. If it is used for heating under lowered pressure after pre-heating in an atmosphere of reducing gas, the same effects can be obtained.