Patent Publication Number: US-2005121495-A1

Title: Temperature control system for solder handling devices and method for temperature control for those devices

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is based on a Japanese patent application serial No. 2003-409868, filed with the Japan Patent Office on Dec. 9, 2003, the contents of which are hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a temperature control system for solder handling devices such as a soldering iron, a tweezer type heater (referred to as a heater tweezer hereinafter), a solder sucker, and a hot air blower, and also relates to a method for temperature control for those devices. More particularly, the present invention pertains to such a temperature control system or method for a plurality of solder handling devices which are selectively connected with a temperature controller for the temperature control.  
      2. General Background and State of the Art  
      Various types of solder handling devices have been used for soldering and other solder handling procedures in relation to electric and electronic parts and substrates on which the parts are mounted by solder. Such solder handling devices may include a soldering iron, a heater tweezer for clamping an electric or electronic part therebetween and reflowing solder for installation and removal of the part, a solder sucker for reflowing and sucking solder on the substrate, and a hot air blower or gun for blowing hot air against the parts or substrate to reflow and blow away solder. Each of the solder handling devices is provided with a heater for heating a heating member or medium such as a tip of the soldering iron, tips of the tweezer heater, a nozzle of the solder sucker, and the air to be blown out of the blower. Those solder handling devices may be provided with a temperature controller for the control of electric power to be supplied to the heater such that the heating member or medium is heated to a desired target temperature.  
      For such temperature control, a high level of temperature restoring characteristics is required to raise the temperature of the heating member or medium rapidly and smoothly to a target value and stably maintain the target temperature. For such high level of temperature restoring characteristic, a feedback control is suitable which detects current or instantaneous actual temperature of the heating member or medium and supplies the appropriate amount of electric power to the heater in accordance with the detected temperature. A proportional control (P control) and a proportional integral and differential control (PID control) are generally employed for such feedback control.  
      It is important for the temperature control that the difference between a set or target temperature intended by a user and the actual temperature of the heating member or medium during use is converged to a small valve. In other words, it is important that the actual temperature is measured with high accuracy so that a compensation may be made to the measured value. A Japanese unexamined patent publication No. 11-10328 discloses a soldering iron device in which the temperature measurement is made with high accuracy by first detecting the difference between a set temperature and an actual temperature measured by an external temperature measuring device, and then making a temperature compensation in accordance with the detected difference.  
      It is also favorable that some safeguard is provided to prevent the user from setting a temperature for the heating member or medium that deviates from a standard temperature range. A device is known which has a predetermined limit for the temperature to be set for the heating member or medium and which invalidates the setting of a temperature beyond the limit. A Japanese examined patent publication No. 7-90363 discloses a temperature controllable soldering iron having a handle in which a key including a resistor for finally determining a set or target temperature is interchangeably installed. The latter soldering iron requires that another key having a resistor of different resistance value corresponding to a newly set temperature is installed for changing the set temperature. Accordingly, only a proper person such as a foreperson having such a key can change the set or target temperature.  
      In general, the solder handling device which is to be held by a user for the solder handling and a temperature controller which serves as the power supply and temperature control device for the solder handling device, are separated from each other for easiness of handling and are connected to each other by an electric cord. The solder handling device varies with its intended use, such as soldering, removal and installation of parts, sucking of solder and blowing away of solder, while the temperature controller is substantially the same in its functions for any of these types of solder handling device. In view of this, a solder-handling-device-interchangeable system is known in which a temperature controller is commonly used for a plurality of types of solder handling devices. In such a system, solder handing devices are selectively connected with the common temperature controller through connectors provided between the solder handling devices and the temperature controller.  
      However, the known solder-handling-device-interchangeable system has a problem that the temperature restoring characteristic is inferior for some type of solder handling devices. For example, the temperature rises to a set temperature rapidly and smoothly when a particular solder handling device is connected to the temperature controller, while the temperature rises so rapidly as to cause overshoot wherein the actual temperature goes beyond desired or target temperature, when another type of solder handling device is connected to the temperature controller. In other case, the actual temperature rises so slowly for certain types of solder handling device that it takes too much time for the temperature controller to restore the set value.  
      The known system has another problem in that the accuracy of temperature measurement is inferior for a certain type of solder handling device. For example, highly accurate temperature measurement is available for a particular solder handling device, while the accuracy of temperature measurement is so low as to cause too much of a difference between the set temperature and the actual temperature for another type of solder handling device.  
      In addition, when a limit or limits are set for the setting of a target temperature in order to prevent a user from setting a target temperature that deviates largely from a standard value, the limit may be improper for some types of solder handling devices. For example, the limit may be proper for a particular type of solder handling device, but the limit is too high or too low, or a range between an upper and lower limits is too large or too small, for another type of solder handling device.  
      The calibration measurement taken in the above mentioned Japanese examined patent publication No. 7-90363 may cope with the problem of temperature setting. As the soldering iron of the publication is provided with a key for determining a set temperature, the target temperature is automatically changed when another solder handling device is in use, provided that each solder handling device has a key including a resistor particular to the device. However, the resistor of the key represents a pinpoint value so that the key must be frequently interchanged every time the target or desired temperature is required to be changed. In addition, a lot of keys must be provided for changing the target temperature at many intervals.  
      Still further, the known system is provided with a single temperature sensor for the sake of common use of the temperature controller and is adapted to supply the same amount of electric power to a pair of heaters for the two tips of a tweezer heater in accordance the output of a single sensor in one of the two tips. In that case, the temperature of one of the tips is not detected, and is likely to deviate from a desired value.  
     INVENTION SUMMARY  
      It is a primary object of the present invention to provide a temperature control system in which a plurality of solder handling devices are selectively coupled or connected with a temperature controller and in which the temperature of a heating member or members is controlled in a manner appropriate to the coupled or connected device.  
      It is another object of the present invention to provide the temperature control system in which a temperature controller controls each solder handling device with a high level of temperature restoring characteristics that is appropriate to the device.  
      It is a further object of the present invention to provide a temperature control system in which a plurality of solder handling devices are selectively coupled or connected with a temperature controller and in which the temperature controller identifies the solder handling device connected thereto and supplies electric power to the device with the power supply being controlled in accordance with the identification.  
      It is still another object of the present invention to provide a temperature control system in which a plurality of solder handling devices are selectively coupled or connected with a temperature controller and in which the temperature controller identifies the solder handling device connected thereto and determines a limit or a range for setting of a target temperature in accordance with the identification.  
      It is yet another object of the present invention to provide a temperature control system in which a plurality of solder handling devices are selectively coupled or connected with a temperature controller and in which the temperature controller identifies the solder handling device connected thereto and detects actual temperature of a heating member or medium with high accuracy and reliability.  
      To attain one or more of the above-mentioned objects, a temperature control system according to the present invention comprises a temperature controller and a plurality of solder handling devices which are selectively connected with the temperature controller, and wherein each solder handling device includes a heating member or medium, a heater for heating the heating member or medium and a temperature sensor for detecting temperature of the heating member, and the temperature controller includes a device identifier for identifying the solder handling device connected thereto, a power supply for supplying electric power to the solder handling device and a power supply control for controlling the supplied power in accordance with the temperature detected by the temperature sensor and the identification of the solder handling device.  
      According to an aspect of an embodiment of the present invention, in a method for controlling temperature of a solder handling device in a system in which a plurality of solder handling devices are selectively connected with a temperature controller which supplies electric power and control temperature of heating member provided on the device or heating medium generated by the device, the method comprises the steps of identifying the solder handling device connected to the temperature controller, and determining temperature control characteristic to be employed for the control of the temperature of the heating member or medium, the characteristic being determined in accordance with the identified solder handling device.  
      According to another aspect of an embodiment of the present invention the temperature controller includes a temperature control characteristic section for determining a temperature control characteristic for each solder handling device, the power supply is controlled in accordance with the determined temperature control characteristic.  
      The above and other features, objects and advantages of the present invention will become more apparent from reading of the following description of a preferred embodiment with reference to the following drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic illustration of a temperature control system for a solder handling device according to an embodiment of the present invention;  
       FIG. 2  shows circuits of a soldering iron and its connector;  
       FIG. 3  shows circuits of a tweezer heater and its connector;  
       FIG. 4  shows circuits of a micro-tweezer heater and its connector;  
       FIG. 5  shows circuits of a solder sucking or absorbing device and its connector;  
       FIG. 6  is a block diagram showing the circuit of the temperature control system;  
       FIG. 7  is a diagram showing temperature control characteristics of the temperature control system;  
       FIG. 8  is a flow chart schematically showing operation of a temperature control section of the temperature control system;  
       FIG. 9  is a diagram showing change of temperature at a tip of a solder handling device; and  
       FIG. 10  shows a circuit for identifying a solder handling device according to another embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring to  FIG. 1  showing a temperature control system  1  according to an embodiment of the present invention, the system is composed of solder handling devices  10   a,    10   b,    10   c,    10   d,  and  10   e  and a temperature controller  40 . The solder handling devices may include a soldering iron  10   a,  a heater tweezer  10   b,  a micro heater tweezer  10   c,  a solder sucker or absorber  10   d  and a hot-air gun or blower  10   e  which are selectively connected with the temperature controller  40  through their respective connectors  14   a,    14   b,    14   c,    14   d  and  14   e.  Each of the solder handling devices  10   a,    10   b,    10   c,    10   d,  and  10   e  includes a heater or heaters and a heating member or heating members, or heating medium generator such as a tip or tips or hot-air blower.  
      The temperature controller  40  serves to supply electric power to the heater or heaters of the solder handling device and control the temperature of the heating member or members or heating medium. A circuit for the power supply and the temperature control is incorporated in a casing of box shape. The temperature controller is provided, on its front panel, with a single connector  41  which serves as a controller connector that can be connected with any of the connectors  14   a,    14   b,    14   c,    14   d  and  14   e  of the solder handling devices  10   a,    10   b,    10   c,    10   d,  and  10   e.  An input member  61  is adapted to be operated by a user or operator to set a temperature of the heating member or medium and input other data which will be described later. A display  63  is adapted to display the set temperature and a current temperature of the heating member or members or medium.  
      When the soldering iron  10   a  is connected to the temperature controller  40  through the connector  14   a,  electric power is supplied from the temperature controller  40  to a heater of the soldering iron  10   a  to heat a tip  11   a,  and the tip  11   a  is maintained at a given temperature by the temperature controller  40 . The soldering iron  10   a  may vary in its size and shape of the tip  11   a  and accordingly in its thermal capacity and thermal output. In that case, an identifying number may be marked on the soldering iron to identify the type of the soldering iron and/or its tip. Then, the operator should input the identifying number to the temperature controller  40  by the input member  61 , and the temperature controller  40  automatically controls the temperature of the tip  11   a  so as to adapt the temperature control manner to the type of the soldering iron. To this end, the temperature controller  40  may set a proper target temperature for the tip  11   a  in accordance with the type of the soldering iron or its tip. An LED  34   a  is provided on the soldering iron  10   a  in the rear portion thereof to indicate whether the identifying number has been inputted. The LED  34   a  may be lit continuously when the identifying number has been inputted, while the LED  34   a  may be winked to urge the operator to input the identifying number when the identifying number has not been inputted.  
      When the heater tweezer or tweezer type heating tool  10   b  is connected with the temperature controller  40  through the connector  14   b,  the temperature controller  40  supplies electric power to the heaters of the heater tweezer  10   b  and heats its pair of tips  11   b  and  12   b.  The heaters are provided for respective tips  11   b  and  12   b.  The heater tweezer  10   b  has a pair of legs which are urged to assume the positions where they are away from each other. When a user pushes down a manipulation member  13   b,  one of the legs is moved toward the other leg to clamp an electric or electronic part between the tips  11   b  and  12   b.  Then, heat is applied to the electric or electronic part from the heated tips  11   b  and  12   b  to reflow solder, thereby enabling installation or removal of the electric or electronic part with respect to a substrate such as a circuit board. An example of such tweezer heater  10   b  is disclosed in a U.S. patent application Ser. No. 10/224,272 which has been assigned to the co-assignee of the present application, and its disclosure is incorporated herein by the reference. The temperatures of the tips  11   b  and  12   b  are controlled by the temperature controller  40  to be maintained at values which are proper or appropriate for the tweezer heater  10   b.    
      The micro heater tweezer  10   c  may be connected with the temperature controller  40  through the connector  14   c  such that electric power is supplied to the heaters of the micro tweezer heater  10   c  for heating a pair of tips  11   c  and  12   c  with the temperatures of the tips  11   c  and  12   c  being controlled by the controller  40 . The heaters are provided for respective tips  11   c  and  12   c.  The micro tweezer heater  10   c  has substantially the same structure as that of the tweezer heater  10   b  but is small in size so that it is adapted for operation in narrow positions and/or for manipulation or handling of smaller electric and electronic parts. The micro tweezer heater  10  is provided with a manipulation member  13   c  which is operated by a user to open and close its legs to clamp the electric or electronic part therebetween and reflow its solder for installation and removal of the part with respect to a substrate.  
      When a solder sucker  10   d  is connected through the connector  14   d  to the temperature controller  40 , electric power is supplied to the heater of the solder sucker  10   d  which, in turn, heats nozzle portion  11   d  of the solder sucker  10   d  to reflow solder attached to an electric or electronic part or a substrate when the nozzle portion  11   d  is brought into contact with or make close to the solder. The solder sucker  10   d  is formed with a through-hole from the nozzle to a reservoir or tank provided within the sucker  10   d  and communicated with a vacuum pump (not shown) through an outlet  12   d  such that the reflowed solder is sucked by negative pressure of the vacuum pump. The sucked solder is temporarily reserved in the reservoir which exchanged with other empty reservoir when it becomes full. The solder sucker  10   c  is provided with a trigger  13   d  which is to be operated by a user to turn on a trigger switch for actuating the vacuum pump. The temperature controller  40  controls the temperature of the nozzle  11   d  to maintain the temperature at a value suitable for the solder sucking.  
      The hot air blower or gun  10   e  includes a heater for heating air supplied from an external blower or fan (not shown). The heated hot air is blown against the solder on an electric or electronic part or substrate through the nozzle to reflow the solder. The hot air serves as heating medium heated by the heater and heating the solder. The hot air blower  10   e  may be connected with the temperature controller  40  through a connector  14   e  such that the temperature of the hot air is controlled to be maintained at a value suitable for the hot air to be blown against the solder.  
      As described above, the controller connector  41  of the temperature controller is adapted to be connected with any of the connectors  14   a,    14   b,    14   c,    14   d  and  14   e  so that the temperature controller  40  can control any of the solder handling devices  10   a,    10   b,    10   c,    10   d  and  10   e  in the manner suitable for each of the solder handling devices  10   a,    10   b,    10   c,    10   d  and  10   e.  To this end, the temperature controller  40  is adapted to identify the solder handling device connected thereto. Description will be made in more detail in the following with respect to circuits for identifying the solder handling device.  
       FIG. 2  is a circuit diagram showing circuits of the soldering iron  10   a  and the connector  14 a. The connector  14   a  includes a heater terminal  15   a,  thermistor terminal  16   a,  a device identification terminal  17   a  and a ground terminal  18   a  as effective terminals. The soldering iron  10   a  includes a heater  23   a,  a temperature sensor  25   a  of a thermocouple, a thermistor  32   a,  LED  34   a  and a device identifying resistor  30   a.    
      The heater  23   a  and the temperature sensor  25   a  are connected in series between the heater terminal  15   a  and the ground terminal  18   a.  The heater  23   a  is provide within the tip  11   a  to heat the tip  11   a.  The temperature sensor  25   a  is located within or close to the tip  11   a  to detect the temperature of the tip  11   a.  The thermistor  32   a  is connected between the thermistor terminal  16   a  and the ground terminal  18   a.  The thermistor  32   a  is located within the soldering iron  10   a  at a base portion or close to the connector thereof to detect a temperature at that location for compensation for the controlled temperature of the tip  11   a.  The LED  34   a  and the device identifying resistor  30   a  are connected in series between the device identification terminal  17   a  and the ground terminal  18   a.  The LED  34   a  is lit continuously when the soldering iron identifying number or code has been inputted, and it is winked or blinks when the soldering iron identifying number or code has not been inputted.  
      The device identifying resistor  30   a  has a resistance value Ra that is specific to the soldering iron  10   a.  Each solder handling device  10  is provided with an identifying resistor having a resistance value that is specific to that solder handling device. In other words, the solder handling devices  10   a,    10   b,    10   c,    10   d  and  10   e  are respectively provided with resistors of different values of resistance which respectively represent the solder handling devices  10   a,    10   b,    10   c,    10   d  and  10   e,  with the values of resistance respectively corresponding to the solder handling devices. Thus, a device identifying circuit of the temperature controller  40  can identify the solder handling device by the resistance value.  
      As the device identifying resistor  30   a  and LED  34   a  are connected to the common terminals  17   a  and  18   a,  the number of terminals is saved to simplify the circuit. The serial connection of the heater  23   a  and the temperature sensor  25   a  also contribute to the saving of the number of terminal and simplification of the circuit. In the latter case, the heater  23   a  and the temperature sensor  25   a  are alternatively actuated by time sharing. The heater  23   a  is energized intermittently or at intervals, and the output of the temperature sensor  25   a  is read by the temperature controller  40  while electric power is not supplied to the heater  23   a.    
       FIG. 3  is a circuit diagram of the heater tweezer  10   b  and the connector  14   b.  The connector  14   b  includes a first heater terminal  15   b,  a thermistor terminal  16   b,  a device identification terminal  17   b,  a first ground terminal  18   b,  a second heater terminal  19   b,  and a second ground terminal  20   b,  as effective terminals. The heater tweezer  10   b  includes a first heater  23   b,  a first temperature sensor  25   b  of a thermocouple, a thermister  32   b,  a device identifying resistor  30   b,  a second heater  24   b  and a second temperature sensor  26   b  of a thermocouple.  
      The first heater  23   b,  the first temperature sensors  25   b,  the thermister  32   b  and the device identifying resistor  30   b  have the same structures and functions as those of corresponding components of the soldering iron  10   a,  i.e. the heater  23   a,  the temperature sensor  25   a,  the thermistor  32   a,  and a device identifying resistor  30   a.  In other words, the circuit for the first tip  11   b  of the heater tweezer  10   b  is substantially same as the circuit for the soldering iron  10   a.  The device identifying resistor  30   b  has a specific resistance value Rb which is different from that of the device identifying resistor  30   a  and which is specific to the heater tweezer  10   b.  Accordingly, the temperature controller  40  identifies the heater tweezer  10   b  by that resistance value.  
      The heater tweezer  10   b  is provided with a circuit for the second heater  24   b  and the second temperature sensor  26   b  in addition to the circuit for the first tip  11   b.  In other words, the heater tweezer  10   b  is provided with a pair of combinations of the heater and temperature sensor, which combinations are respectively installed in the tips  11   b  and  12   b  such that the temperatures of the tips  11   b  and  12   b  are controlled independently of each other. Thus, if temperature of one e.g.  12   b  of the tips drops suddenly, temperature sensor  26   b  for the tip detects the temperature drop and the temperature controller  40  increases power supply to the heater  24   b  for the tip to restore the temperature of the tip  12   b  rapidly. The controller connector  41  of the temperature controller  40  is adapted to be connected with the six terminals of connector  14   b.  Identifying the resistance value of the device identifying resistor  30   b,  the temperature controller  40  knows that the heater tweezer  10   b  is connected thereto, and the temperature controller  40  treats the second heater terminal  19   b  and the second ground terminal  20   b  as effective terminals for the temperature control.  
      The micro heater tweezer  10   c  has substantially the same construction and functions as those of the heater tweezer  10   b.  The resistance value of its device identifying resistor is different from that of any other solder handling devices and is specific to the micro heater tweezer  10   c  such that the temperature controller  40  know that the micro heater tweezer  10   c  is connected thereto.  
       FIG. 4  is a circuit diagram of a circuit for the solder sucker  10   d  and a circuit of its connector  14   d.  The connector  14   d  includes four effective terminals of a heater terminal  15   d,  thermistor terminal  16   d,  a device identification terminal  17   d  and a ground terminal  18   d.  Accordingly the terminals of the connector  14   d  of the solder sucker  10   d  correspond to that of the connector  14   a  of the soldering iron  10   a.  The solder sucker  10   d  includes a heater  23   d,  a temperature sensor  25   d  of a thermocouple, a thermistor  32   d,  a device identifying resistor  30   d  and a trigger switch  30   d.    
      The heater  23   d,  the temperature sensor  25   d  of a thermocouple, the thermistor  32   d  and the device identifying resistor  30   d  have the same structures and functions as those of corresponding components of the soldering iron  10   a,  i.e. the heater  23   a,  the temperature sensor  25   a,  the thermistor  32   a,  and a device identifying resistor  30   a.  The device identifying resistor  30   d  has a specific resistance value Rd which is different from that of any other device identifying resistors and which is specific to the solder sucker  10   d.  Accordingly, the temperature controller  40  identifies the solder sucker  10   d  by that resistance value.  
      When a user operates the trigger  13   d,  the trigger switch  36   d  is turned on to actuate the vacuum pump (not shown) and suck reflowed solder through the nozzle  11   d.    
      The trigger switch  36   d  is connected across the device identifying resistor  30   d.  Accordingly, the resistance value of the device identifying resistor  30   d  is identified while the trigger switch  36   d  is open. As the device identifying resistor  30   d  and the trigger switch  36   d  are connected in parallel with each other between the a device identification terminal  17   d  and a ground terminal  18   d,  the a device identification terminal  17   d  can be used as a trigger signal detecting terminal, thereby saving the number of the terminals and simplifying the circuit construction.  
      The circuit for the hot air blower  10   e  and its connector  14   e  is substantially the same as that of the soldering iron  10   a,  but the LED  34   a  may be dispensed with. The hot air blower  10   e  is provided with a device identifying resistor  30   e  of a specific resistance value Re that is different from that of any other device identifying resistors and which is specific to the hot air blower  10   e.  Accordingly, the temperature controller  40  identifies the hot air blower  10   e  by that resistance value.  
       FIG. 5  shows a device identifying circuit  42  provided in the temperature controller  40 . The device identifying circuit  42  may be selectively connected with any device identifying resistor. In the case shown in  FIG. 5 , the device identifying circuit  42  is connected with the resistor  30   a  of the soldering iron  10   a.  The device identifying circuit  42  shown in  FIG. 5  employs constant voltage type detection.  
      With reference to  FIG. 5 , a resistor  42   a  is connected in series with the device identifying resistor  30   a,  and a constant voltage Vcc is applied across the series connection of the resistors  42   a  and  30   a.  With this connection, the voltage Vg between the device identifying terminal  17   a  and ground terminal  18   a  is shown by the following formula (1). It is to be noted here that the resistance of the LED is out of consideration for the sake of simplicity of consideration, since the resistance of the LED is not substantial. 
 
 Vg =( Ra/ ( Ra+R ))× Vcc    (1) 
 
      Wherein Vcc is a power source voltage, and R is a resistance value of the fixed resistor  42   a  connected between the device identifying terminal  17   a  and a voltage source.  
      As the resistance value Ra of the device identifying resistor  30   a  is a fixed value specific to the soldering iron  10   a,  the voltage Vg derived from the formula (1) has also a fixed value specific to the soldering iron  10   a.  Detecting that voltage Vg by its CPU, the temperature controller  40  determines that the soldering iron  10   a  is connected to the temperature controller  40 .  
      By way of an example, let&#39;s assume that Ra=220Ω, R=390Ω, and Vcc=5V, then, Vg=1.80V from the formula (1). In the case when a tweezer  10   b  having a device identifying resistor Rb of 820Ω is connected to the controller  40 , the output voltage Vg of about 3.39V will be obtained by substituting the value of Rb in place of Ra in the formula (1). Accordingly, when the temperature controller  40  detects the voltage Vg of 1.80V, it determines that it is connected with a soldering iron but not with the tweezer.  
      The device identifying resistor may not be provided in every solder handling device. For example, if the resistor  30   d  is dispensed with in the circuit of solder sucker  10   d  (see  FIG. 4 ), a zero voltage appears between the device identifying terminal  17   d  and the ground terminal  18   d  when the trigger switch  36   d  is turned on, since it is assumed that Rd=∞ at that time. Accordingly, the temperature controller identifies the solder sucker by the zero voltage. If the resistor  30   a  is dispensed with in the circuit of the soldering iron  10   a  (see  FIG. 2 ), then it can be regarded that a resistor of infinite resistance is connected between the device identifying terminal  17   a  and the ground terminal  18   d,  and a voltage Vcc will appear between the terminals.  
       FIG. 6  is a block diagram schematically showing the control system for the solder handing device.  FIG. 6  shows the case where a soldering iron  1   a  is coupled with the temperature controller  40 , which includes an identifying circuit  42 , a heater control circuit  47 , a sensor amplifier  48 , a CPU  50 , an input section  61  and a display section  63 . The heater control circuit  47  supplies electric power to the heater  23   a  in response to instruction from the CPU  50 . Receiving signals from the temperature sensor  25   a  and thermister  32   a,  the sensor amplifier  48  amplifies those signals and sends them to the CPU  50 .  
      The CPU  50  is a main control section of the temperature controller  40 , and serves to identify the solder handling device  10  coupled thereto, by reading or detecting the device identifying voltage Vg, and controls the solder handling device  10  in accordance with that identification. When the soldering iron  10   a,  for example, is connected to the temperature controller  40 , the CPU  50  controls the soldering iron  10   a  using a controlling program and control parameters that are appropriate to the soldering iron  10   a.    
      In more detail, a set temperature set by the user is controlled by the CPU  50  such that the set temperature is within a range that is predetermined for each solder handling device, with the data of the range being stored in the CPU  50 . For example, the range is from 200° C. (lower limit) to 450° C. (upper limit) for the soldering iron  10   a,  from 200° C. (lower limit) to 400° C. (upper limit) for the heater tweezers  10   b  and  10   c,  and from 320° C. (lower limit) to 400° C. (upper limit) for the solder sucker  10   d.  Identifying by the device identifying voltage Vg that a soldering iron, for example, is coupled with the temperature controller, the CPU  50  determines that the range for allowable temperature settings is from 200° C. to 450° C. Thus, if the user intended to set a temperature that is higher than the upper limit of 450° C., the CPU  50  will not accept that setting and will set the temperature at 450° C.  
      The CPU  50  also recognizes or determines a current temperature of the tip  11   a  on the basis of the signal from the sensor amplifier  48 . In general, the temperature detected by the temperature sensor  25   a  differs from the current actual temperature of the tip. Accordingly, the CPU determines the current actual temperature of the tip by compensating for the temperature detected by the temperature sensor  25   a.  The appropriate value or amount of the compensation is pre-determined and memorized for each solder handling device since the appropriate value or amount of the compensation differs with capacity of the heater, heat capacity and other parameter of the tip. The CPU  50  makes the temperature compensation using the compensation value specific to the solder handling device that has been identified as being coupled with the temperature controller  40 . In addition, the temperature detected by the thermister is also taken into account. Thus, the compensation of tip temperature is made with high accuracy in accordance with the solder handling device coupled with the temperature controller  40 .  
      From the difference between the set temperature and detected and compensated current temperature, the CPU calculates electric power to be supplied to the heater  50 , and instructs the heater control circuit  47  to supply that calculated amount of electric power. The instruction from the CPU  50  to the heater control circuit  47  may be data representing time period during which the electric power is supplied to the heater, and the heater control circuit supplies electric power to the heater for that instructed time period.  
       FIG. 7  is a diagram showing the temperature control characteristics set predetermined for respective solder handling devices. The abscissa shows the temperature T 1  of the tip or the hot air, while the ordinate shows the amount of temperature control Q which is a parameter of a feedback gain and the like for the heater control circuit  47 . The more the amount of the temperature control is, the more the electric power is supplied, provided that the other conditions are the same.  FIG. 7  shows the temperature control characteristic  70   a  for the soldering iron  10   a,  the temperature control characteristic  70   b  for the heater tweezer  10   b,  and the temperature control characteristic  70   d  for the solder sucker  10   d.  Those characteristics are predetermined and memorized in a memory device associated with the CPU  50  which in turn selects a temperature control characteristic for the solder handling device  10  that has been identified by the device identifying circuit  42 . For example, if the device identifying circuit  42  determines that a soldering iron  10   a  is connected to the temperature controller  40 , the CPU  50  chooses the temperature control characteristic  70   a  for the soldering iron  10   a  and makes instruction to the heater control circuit in accordance with that selected characteristic.  
      Every characteristics shown in  FIG. 7  descend to the right such that the lower the temperature T 1  of the tip or hot air, the more the electric power is supplied to raise the temperature rapidly. In the region where the temperature T 1  is larger, the amount of power supply decreases, thereby avoiding overshoot of the controlled temperature. Although the most appropriated temperature control characteristics are different with the solder handling devices  10 , the characteristic is determined and stored for each solder handling device  10 , and temperature is controlled with the most appropriate characteristic irrespectively of the type of the solder handling device.  
      Next, description will be made of the operation of the temperature control system  1  with reference to  FIG. 8  which is a flowchart schematically showing the temperature control process performed by the CPU  50 . The control flow starts when the power switch is turned on, with any solder handling device being connected with the temperature controller  40 . At Step S 1 , the resistance value of the device identifying resistor is determined from the voltage of the device identifying circuit  42 . Then, at Step S 3 , the type of the solder handling device  10  is identified by the value of the resistance. The flowchart in  FIG. 8  shows the control process for three types of the solder handling devices, i.e. the soldering iron  10   a,  the heater tweezer  10   b  and the solder sucker  10   d,  for the simplicity of explanation, but the same or similar process may be applied to other solder handling devices.  
      If the soldering iron  10   a  is identified as being connected with the temperature controller  40 , the operation of the CPU  50  proceeds to Step S 5  where parameters for the control of the soldering iron  10   a  are set with the characteristic  7   a  shown in  FIG. 7  being selected. Then, the temperature of the heater  23  is controlled in accordance with the characteristic  7   a  (Step S 7 ).  
       FIG. 9  shows a characteristic of temperature change of the tip  11   a  at its raising or initial stage of temperature control process carried out as mentioned above. In the diagram shown in  FIG. 9 , the abscissa shows elapsed time t while the ordinate shows the temperature T 1  of the tip  11   a.  T 2  represents a temperature preset by means of the input section  61 . As shown by the raising characteristic  90  as indicated by the solid line, the temperature of the tip  11   a  rises rapidly while the temperature is low, but it rises gently as the temperature approaches the preset value so that the temperature of the tip  11   a  is raised to the preset value promptly and stably without causing overshooting.  
      The two-dot chain lines or phantom lines show the temperature control characteristic in two cases where the temperature control characteristic  70   a  is set improperly. The temperature rising characteristic curve  89  shows the case where the controlled amount of power supply changes at a low level. In this case, as the amount of power supplied is generally too small, it takes too much time for the temperature of the tip to reach the preset value. The temperature rising characteristic curve  91  shows the case where the controlled amount of power supply changes at a high level. In this case, the amount of power supplied is generally so large that the temperature rises rapidly, causing overshooting in which the actual temperature goes beyond the set temperature. After that, the temperature unstably reaches the preset value with the actual temperature oscillating. Thus, the characteristic curves  89  and  91  shows the cases where the temperature control characteristics do not suit the soldering iron  10   a.  In contrast, according to the embodiment of the present invention, the most appropriate characteristic  70   a  is selected for the soldering iron  10   a,  an ideal temperature restoring characteristic is attained.  
      Returning back to the flowchart of  FIG. 8 , if it is determined at Step S 3  that the heater tweezer  10   b  is connected to the temperature controller  40 , the operation proceeds to Step S 15  where parameters for the control of the heater tweezer  10   b  are set with the characteristic  7   b  shown in  FIG. 7  being selected. Then, at Step S 17 , the temperatures of the first and second heaters  23   b  and  24   b  are controlled in accordance with the characteristic  7   b.  In this case, the most appropriate temperature control characteristic  7   b  for the heater tweezer  10   b  is selected and employed for the temperature control, the temperatures of the tips  11   b  and  12   b  are controlled in the manner similar to the temperature raising characteristic  90  shown in  FIG. 9 .  
      It is to be noted that the first and second heaters  23   b  and  24   b  are controlled separately in accordance with the identification that the heater tweezer is connected with the temperature controller  40 . With this separate control, the temperature of either one of the tips  11   b  and  12   b  is restored rapidly and smoothly when it changes greatly independently of the other.  
      If it is determined at Step S 3  that the solder sucker  10   d  is connected to the temperature controller  40 , the operation proceeds to Step S 25  where parameters for the control of the solder sucker  10   d  are set with the characteristic  7   d  shown in  FIG. 7  being selected. Then, at Step S 27 , the temperature of the heater  23   d  is controlled in accordance with the characteristic  7   d.  In this case, the temperature of the tip of the nozzle  11   d  is controlled in the manner similar to that according to the temperature rising characteristic  90  shown in  FIG. 9 . At Step S 31 , it is determined if the trigger switch  36  is closed or not. If the closure of the trigger switch is determined, the operation proceed to Step S 33  where a vacuum pump (not shown) is actuated to suck reflowed solder.  
      As an embodiment of the present invention has been described, the present invention is not limited thereto but various changes and modifications are available within the spirit and scope as defined in the accompanying claims.  
      For example, constant current type circuit as shown in  FIG. 10  may be employed for the device identifying circuit  43 . A constant current circuit includes resistors R 1 , R 2 , R 3 , R 4  and R 5 , a zener diode  44 , an amplifier  45  and transistor  46  which are arranged as shown in  FIG. 10  to output constant current I from the transistor  46  to the device identifying resistor  30   a  and the LED  34   a.  The current I is constant irrespective of the resistance value Ra of the resistor  30   a,  and is, for example, 0.008A which is proper for the energization of the LED  34   a.  As the magnitude of the current I does not change even if other solder handling devices are connected to the temperature controller in place of the soldering iron  10   a,  the LED is energized by the same magnitude of current and emits light of constant brightness. The voltage between the device identifying terminal  17   a  and the ground terminal  18   a,  i.e. the device identifying voltage Vg is shown by following the formula (2), wherein the resistance of the LED is out of consideration for simplicity. 
 
 Vg=I×Ra    (2) 
 
      As is apparent from the formula (2), the resistance value Ra is determined by detecting the device identifying voltage Vg by means of the CPU  50  provided in the temperature controller  40 , since the electric current I is constant. The resistance value Ra indicates that the soldering iron  10   a  is connected to the temperature controller  40  as a solder handling device.  
      As another modification, the device identifying means may be provided in or on the temperature controller  40 . For example, the temperature controller  40  may be provided, on its panel, with multiple connectors  41  of a number in accordance with the number of types of solder handling devices to be coupled with the temperature controller  40 . Each of the connectors  41  is adapted for connection with a specific solder handling device, such that the CPU identifies the solder handling device in accordance with the connector to which the solder handling device is connected, i.e. by detecting which of the connectors is connected with the device. For example, the CPU  50  determines that the soldering iron  10   a  is in use, when the connector  14   a  of the soldering iron  10   a  is connected to a connector that is specific for the connection with the connector  14   a  of the soldering iron  10   a.    
      As still another modification, the temperature controller  40  may be provided, on its front panel, with a single connector which has multiple terminals to be selectively connected with connectors of a plurality of solder handling devices in the manner such that each solder handling device has a particular combination of connector terminals to be connected with a corresponding particular combination of terminals of the single connector of the temperature controller  40 . With this arrangement, the temperature controller and/or its CPU identify the solder handling device connected thereto by means of the combination of the terminals in use.  
      In the above described embodiment, the temperature controller  40  is adapted to be selectively coupled with five types of solder handling devices. The number of the types or kinds of the solder handling device  10  may vary in accordance with requisites for the temperature control system  1 .