JP3068526B2 - Heater temperature detection device for pulse heating type bonding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater temperature detecting device used in a pulse heating type joining apparatus for locally heating and joining a joined portion by supplying a pulse current to a heater pressed against the joined portion. Things.

[0002]

2. Description of the Related Art Conventionally, a pulse heating method has been used as a joining apparatus used for thermocompression bonding of lead wires of a thick-film printed wiring board, a thin-film printed wiring board, and the like, and reflow soldering of IC leads and the like to a printed wiring board. Are known.

In this method, a heater chip made of a high-resistance material such as molybdenum ( _MO ) is pressed against a portion to be joined, and in this state, a large pulse-like current flows through the heater chip to generate Joule heat. The heat is generated, and the heat is locally heated and melted by this heat to join. For example, in the case of reflow soldering, the solder sandwiched between a pair of parts to be joined is melted, and then the pulse current is stopped, and the parts to be joined are cooled and the temperature of the solder becomes equal to or lower than the solidification temperature of the solder. Part.

Accordingly, in this type of bonding apparatus, a head having lifting / lowering drive means for pressing or separating a heater chip from a part to be bonded, and a pulse current that changes in accordance with the heating time of the heater chip are generated. And a pulse heat power supply. In this case, the pulse heat power supply feeds back the temperature of the heater chip, that is, the heater temperature, and controls the heater current so that the heater temperature has a preset time / temperature control characteristic (referred to as a temperature profile).

That is, the phase of the heater current (AC) is controlled so as to reduce the difference between the target temperature obtained from the temperature profile and the feedback heater temperature, and the heater temperature follows the change in the target temperature.

This device requires a heater temperature detecting device for detecting the heater temperature. For this reason, thermocouples have been widely used conventionally. The thermocouple here measures the thermoelectromotive force while fixing one of the joining points of the dissimilar metals (hot junction) to the heater and maintaining the other (cold junction) at a constant reference temperature. is there. Since this thermoelectromotive force is determined based on the temperature difference between the hot junction and the cold junction, when the temperature of the cold junction is other than the reference temperature, for example, room temperature,
The heater temperature obtained based on the measured thermoelectromotive force is not an accurate heater temperature.

[0007]

However, in the conventional apparatus, there is no functional inconvenience if the temperature can be measured with sufficient accuracy around the maximum temperature of the heater normally required for bonding. Therefore, the reference temperature of the cold junction is set to, for example, about 20 ° C., and the room temperature is allowed to slightly deviate from this reference temperature.

Although the reference temperature is manually adjusted to correct the measured temperature, this adjustment operation is very troublesome. As described above, in the conventional method, when the temperature of the cold junction deviates from the reference temperature, it becomes difficult to accurately measure the heater temperature. Therefore, the heater temperature cannot be controlled with high accuracy, and the uniformity of the product cannot be maintained. And the yield is reduced.

On the other hand, if the thermocouple is deteriorated or the thermocouple is separated from the heater, the heater may be overheated, causing a failure such as heat in a work such as an IC or a thermal deformation of a printed circuit board. Therefore, monitoring of the heater temperature rising speed immediately after the start of the supply of the heater current is performed. For example, the lower limit temperature (for example, 280 ° C.) slightly lower (for example, 20 ° C. lower) than the maximum temperature of the heater set by the temperature profile, that is, the set temperature (for example, 300 ° C.).
Is set, and the time required to reach the lower limit temperature is monitored to estimate whether the thermocouple is normal or not or whether the thermocouple is properly heated.

It is also conceivable to use a temperature profile for heating the heater in two stages. That is, in the first stage heating, for example, heating is performed to a set temperature of 150 °, and after a lapse of a predetermined time, heating is started in the second stage, for example, to a set temperature of 300 ° C. In this case, it is conceivable to monitor the heater temperature increasing speed during the heating of the first stage and the second stage by setting the respective lower limit temperatures as described above.

[0011] When the lower limit temperature slightly lower than the heating set temperature is set as described above, or when the heating is divided into two stages of the first stage and the second stage, the heater temperature can be accurately determined over a wide temperature range. Need to be measured. However, the conventional method has a problem that the heater temperature cannot be measured with high accuracy in a wide temperature range.

Therefore, the present invention can detect the heater temperature with high accuracy over a wide temperature range, improve the uniformity of the product, increase the yield, and use a pulse which requires no manual adjustment operation. An object of the present invention is to provide a heater temperature detecting device for a heat-type joining device.

[0013]

According to the present invention, a first object is to press a heater against a portion to be joined, supply a pulse current to the heater and heat the heater, and feed back the heater temperature to set a predetermined heater temperature. In a heater temperature detecting device used in a pulse heating type joining device that performs joining by following a profile, a temperature at a hot junction at one end is fixed to the heater and a temperature at a temperature near a cold junction of the thermocouple is detected. At the time of zero crossing of the sensor and heater current
A heater for a pulse heating type joining apparatus, comprising: a temperature compensator for adding an output of the temperature sensor to the sampled thermoelectromotive force of the thermocouple; and a display device for displaying an output of the temperature compensator. Achieved by a temperature sensing device.

The temperature compensating section may be formed by an analog circuit or a digital circuit. In the case of using an analog circuit, it is possible to amplify the thermoelectromotive force, add the output of the temperature sensor in an analog manner, and display the result on a display device such as a voltmeter.

When a digital circuit is used, the output of the thermoelectromotive force and the output of the temperature sensor may be A / D converted, and these digital signals may be added and displayed on a display device. In this case, if the thermoelectromotive force and the temperature sensor output are selected by a changeover switch and alternately guided to one A / D converter, the sampling timing can be controlled by the changeover switch, and the A / D converter can be controlled. You can do it with just one.

If the compensation data for correcting the linearity of the thermoelectromotive force is stored in the memory means, and the compensation is performed based on the compensation data, the heater temperature can be detected with higher accuracy. In this case, a plurality of compensation data for different types of thermocouples may be stored in the memory means, and compensation data corresponding to the thermocouple actually used may be selected and used.

[0017]

When the power switch is turned on, the heater is pressed against the work, and the heater current flows, the heater generates heat. A heater current flows through the heater based on the temperature profile, and the heater temperature is controlled according to the temperature profile.

The hot junction of the thermocouple is fixed to the heater, and the temperature near the cold junction detected by the temperature sensor is determined by the heater current.
It is added to the thermoelectromotive force of the thermocouple sampled at the time of the locross . For this reason, the heater temperature obtained from the thermoelectromotive force is corrected by the output of the temperature sensor to display an accurate temperature. It is desirable that the change of the thermoelectromotive force with respect to the measured temperature of the thermocouple has linearity, but there are some thermocouples whose actual linearity is insufficient. In this case, data (compensation data) for correcting the deviation from the linearity is stored in a memory means such as a ROM, and the detection accuracy is further improved by correcting the thermoelectromotive force using the compensation data. be able to.

[0019]

FIG. 1 is an external view of a joining apparatus according to an embodiment of the present invention, FIG. 2 is a simplified view of a control system thereof, and FIG.
FIG. 3 is a diagram showing a heater current waveform (a), its zero cross signal (b), and a reset signal R (c). FIG. 4 is a diagram showing a heater current detection circuit, and FIG. 5 is a display example of a display device. FIG. 6 is a functional block diagram of the control circuit, and FIG. 7 is a circuit diagram of a temperature compensator of the thermocouple.

In FIG. 1, reference symbol H indicates a head portion, and P indicates a pulse heat power supply. The head portion H has a base 10, a driving unit 12 disposed above and facing the base 10, and a foot pedal 14. The base 10 holds a work including a printed circuit board 16, and the drive unit 12 holds a heater chip 18 that moves up and down above the printed circuit board 16. The heater chip 18 descends when an operator steps on the foot pedal 14, and presses the printed circuit board 16 with a predetermined pressure.

The heater chip 18 is made of molybdenum ( _MO ) or the like, and is formed in a substantially U-shape when viewed from the front as shown in FIG. The heater chip 18 is heated by a pulse-like heater current I supplied from a power source P.
The work includes a circuit pattern 20 on the printed circuit board 16, a solder layer 22 supplied by pre-soldering the circuit pattern 20 or dipping the circuit pattern 20 in a molten solder layer, and an IC or the like superimposed on the solder layer 22. It is formed with the leads 24.

The heater chip 18 is pressed against the work by the drive unit 12 and generates heat when a heater current is supplied. Due to the heat generated by the heater 18, the solder layer 22 is melted. Thereafter, the heater current is cut off and the solder layer 22 is cooled to solidify the solder, and then the heater chip 18 is raised. During this time, the heater temperature T is detected by the thermocouple 26 adhered to the heater chip 18.

Next, the pulse heat power supply P will be described with reference to FIGS. In FIG. 2, reference numeral 30 denotes a transformer, and 32 denotes a controller. The transformer unit 30 includes a welding transformer 34, and a primary winding of the welding transformer 34 is supplied with a 200V single-phase AC voltage whose phase is controlled by the SCR stack 36. A low-voltage alternating current induced in the secondary winding of the welding transformer 34 is supplied to the heater chip 18.

The phase of the AC power supplied to the primary side of the welding transformer 34 is detected by the insulating transformer 38 and input to the phase control circuit 40 in the control unit 32. The phase control circuit 40 synchronizes with a synchronization signal (SYNC) indicating a zero crossing point at which the AC power supply voltage becomes zero, and
A gate signal G having the conduction angle θ (FIG. 3) set by the PU 70 is sent to the SCR drive circuit 42. The gate signal G is converted to a gate drive signal of a predetermined voltage level by the SCR drive circuit 42,
The CR is alternately turned on and off.

The current on the secondary side of the welding transformer 34, that is, the heater current I is determined by a current detector 44 using a Hall element or the like.
Is amplified by an amplifier (AMP) 46 to a predetermined voltage level, and the signal i is input to an integrator 48 in the control unit 32. This integrator 48 is, as shown in FIG.
It has an integrating capacitor 52 connected to the collector of the transistor 50, and a switching transistor 54 for discharging the electric charge of the integrating capacitor 52. The output of the current detector 44 is amplified and becomes a signal i, which is led to the base of the PNP transistor 50 and is connected to the capacitor 5.
2 is changed.

The switching transistor 54 is turned on by the reset signal R (FIG. 3) obtained by the phase control circuit 40. At this time, the charge of the capacitor 52 is discharged through the transistor 54. As a result, the capacitor 52
Indicates the integral value of the heater current I shown in FIG. 3 every half cycle. This output is guided to a changeover switch (multiplexer) 56. Note that the reset signal R takes a short time t _R (see FIG. 3) for the synchronization signal SYNC.
This signal is output with only a delay, and resets the capacitor 52 slightly after the zero-cross point of the AC power supply.

Numeral 58 denotes a temperature compensator for correcting the thermoelectromotive force output from the thermocouple 26. This temperature compensator 58 is configured as shown in FIG. Hot junction A of the thermocouple 26
Is fixed to the heater chip 18 by welding or the like. For the thermocouple 26, for example, chromel or alumel is used. The thermoelectromotive force generated at the cold junction B of the thermocouple 26 is amplified by the amplifier 60. The temperature near the cold junction B is detected by a temperature sensor 62 such as a resistance thermometer, and the output voltage is added to the output voltage of the amplifier 60 by an adder 64. The output of the adder 64 is a changeover switch (multiplexer)
Guided to 56.

Since an expensive metal is used for the thermocouple 26, it is uneconomical if the distance between the heater chip 18 and the cold junction B is long. Therefore, a compensating lead 66 may be connected to the thermocouple 26. That is, a compensating lead wire 66 made of, for example, copper or constantan is connected between the thermocouple 26 and the cold junction B. The cold junction B and the amplifier 60 are connected by a normal copper conductor.

The changeover switch 56 is provided with a signal indicating the heater current I output from the integrator 48 and a temperature compensator 58.
A signal indicating the heater temperature T whose temperature has been compensated for is selected with a time lag, and the digital signal is sent to the CPU 70 by the A / D converter 68. Here, since the integrator 48 is reset at twice the frequency of the AC power supply, the changeover switch 56
Needs to sample the capacitor voltage at the same frequency as the reset signal R. For example, if the power frequency is 50
At a sampling frequency of the changeover switch 56 100H _Z in the case of H _Z, sampling the heater current I every 10msec other words.

On the other hand, since the output of the temperature compensator 58 indicating the heater temperature T is not subject to such a regulation of the power supply frequency, the switch 56 is set to, for example, 0.5 sec (500 msec).
c, 2H _Z ). When the energization time of the heater chip 18 is sufficiently short, the sampling cycle of the heater temperature T is shortened, for example, for 0.2 seconds.
It is preferable that the temperature graphic display described later be made to look smooth. At this time, since the thermocouple may be affected by a change in the heater current I, it is desirable that the detection of the heater temperature T is also performed at a timing when the heater current I becomes zero. Thus in synchronization with the aforementioned synchronous signal (CYNC) it was to sample.

The temporal changes of the heater temperature T and the heater current I detected as described above can be graphically displayed on the display device 72 of the pulse heat power supply P shown in FIG. For example, a graphic can be displayed as shown in FIG. Here, a case where the heater temperature T is simply controlled to be constant at the set temperature T _O , that is, a case where one-stage heating is performed is shown. Therefore heater current I is increased while power immediately after the start of heating, then the heater current is sharply in order to prevent overshoot of the current I, also constant heater current I after reaching a predetermined set temperature T _O.

[0032]

[Control Circuit] Next, a control circuit will be described with reference to FIGS. Reference numeral 70 denotes a CPU (microcomputer) to which the phase control circuit 40, A / D converter 68, and memory means 74 such as ROM are connected via a bus 76. The bus 76 includes I / O interfaces 78 and 8
0 through the input device 82 and the display device 7 described above.
2 are connected. The bus 76 is also connected via an interface 84 to a microswitch 86 that detects that the pressing force of the heater chip 18 has reached a certain level or more.

The input device 82 is for inputting numerical values, instructions, and the like from a switch group 82A provided on the front surface of the case of the pulse heat power supply P shown in FIG. The display device 72 displays the change in the heater temperature and the like as described above. The display device 72 may display an error when an abnormality occurs in the operation. This error display may be displayed using a separately provided LED (light emitting diode) or a warning buzzer may be sounded.

The CPU 70 has functions such as a judgment means 88 and a temperature control means 90. The determining means 88 determines the heater temperature T
Is determined to have reached the set temperatures T ₁ and T ₂ and the lower limit temperatures T _L1 and T _L2 slightly lower (about 20 ° C.). The temperature control means 90 controls the heater temperature T.

The memory means 74 stores a temperature profile, that is, a control pattern for a target heater temperature time, and a lower limit temperature _TL for judging a rising speed of the heater temperature T. The pattern, temperature, time, lower limit temperature T _{L, and the} like of the temperature profile can be changed by the input device 82. The judgment means 88 and the temperature control means 9
0 may be formed by a circuit different from the CPU 70.

[0036]

[Outline of Operation] Next, the outline of the operation of this apparatus will be described with reference to the operation timing chart of FIG. P ₀ indicated by a solid line in FIG. 8 is a temperature profile, which is stored in the memory 74. This temperature profile P ₀ indicates a target temperature during heating. In this embodiment, heating is performed in two stages.

The temperature profile P ₀ sets a first set temperature T ₁₀ (for example, 200 ° C.) in the first stage heating and a second set temperature T ₂₀ (for example, 300 ° C.) in the second stage heating. In addition, the lower limit temperature T _L1 in each heating stage (for example, 1
80 ° C.) and T _L2 (for example, 280 ° C.).
These set values are also stored in the memory means 84.

When using this apparatus, a work is placed under the heater chip 18 as shown in FIG. 2, and the foot pedal 14 (FIG. 1) is depressed. Then, the head H descends.
When the head H moves down and the pressure at which the heater chip 18 presses the work reaches a predetermined pressure, a microswitch (not shown) detects this (time point b). In FIG. 8, an actuating signal (ACT signal) indicates the output of the microswitch, and is turned on when the pressure of the heater chip 18 is equal to or higher than a predetermined pressure. Heating of the heater is started after a lapse of a fixed time, that is, a squeeze time (SQ.TIME) t _sq from the time point b. The squeeze time t _sq is a delay time from when the ACT signal is received to when the heater heating is started,
This is provided to ensure the contact between the heater chip 18 and the work.

The time point c at which the squeeze time t _sq elapses is the start of heating, and the current starts to flow. While monitoring the heater temperature T, the CPU 70 determines the phase angle θ of the heater current that minimizes the difference between the temperature profile P ₀ and the actual heater temperature T. The phase control circuit 40 controls the gate of the SCR so as to have the phase angle θ.

If the heater temperature T reaches the first lower limit temperature T _L1 within a predetermined time, the CPU 70 determines that proper heating is being performed. And upon reaching the first predetermined temperature T _10, starting the counting of the heating time of the first stage heating. Then, the second stage heating is started after the elapse of this time. If the heater temperature T reaches the second lower limit temperature _TL2 within a predetermined time, the CPU 70 determines that proper heating is being performed. Then from the time of reaching the second predetermined temperature T ₂₀ starts counting the heating time of the second stage heating, and outputs the heating ends at lapse d time (heat-end) signal H _END, shut off the heater current I At the same time, the cooling signal CL is turned on to perform cooling.
This cooling may be performed forcibly by applying a cooling air, or may be left to wait for natural cooling.

When the heater current is cut off, the heater temperature T starts decreasing. In the memory 74, a set temperature T _S lower than the solder solidification temperature when the heater temperature drops is preset, and the judging means 88 sets the heater temperature T to the set temperature T _S.
When detecting that the temperature has dropped to _S , the CPU 70 turns off the cooling signal CL and sounds a buzzer. The operator hears the buzzer and then returns the foot pedal 14,
The heater chip 18 is raised. That is, the heater chip 18 is separated from the work.

In this embodiment, the heater temperature T is graphically displayed on the display device 72 of the pulse heat power source P.
For example, in this case, a time change of the heater temperature T can be graphically displayed on the display device 72 using a liquid crystal plate or the like. If the change in the heater temperature is graphically displayed so as to be comparable with the temperature profile P ₀ , the difference between the target temperature and the actual temperature can be easily visually confirmed, which is convenient.

[0043]

FIG. 9 is a diagram showing an embodiment in which the heater temperature T is displayed on an analog display meter different from the display device 72 of the pulse heat power source P. In this figure, the same parts as those in FIG. 7 described above are denoted by the same reference numerals, and the description thereof will not be repeated.

In this figure, reference numeral 72B denotes a display device, which is constituted by an analog voltmeter. The analog output voltage of the adder 64 is guided to the display meter 72B to display the voltage. A scale of the heater temperature T corresponding to the voltage is provided on the display meter 72B, and the heater temperature T can be immediately read from the scale. When the output voltage of the adder 64 fluctuates under the influence of the periodic fluctuation of the heater current, it is preferable to interpose the smoothing circuit 100 between the adder 64 and the display meter 72B.

FIG. 10 is a view showing another embodiment. This embodiment is constituted by a digital circuit. In this figure, reference numeral 102 denotes an analog amplifier, which amplifies the thermoelectromotive force of the thermocouple 26. An amplifier 104 similarly amplifies the output voltage of the temperature sensor 62 provided at the cold junction B of the thermocouple 26. 106 (106A, 106B) is a changeover switch, and 108 is an A / D converter. Changeover switch 106
Selects one of the outputs of amplifiers 102 and 104 and
The output is guided to a / D converter 108, where it is converted into a digital signal, and the respective output is guided to a compensating means 110 or a latch (temporary storage circuit) 112.

Reference numeral 114 denotes a memory means, which is formed of a non-volatile memory such as a ROM, and stores data for correcting the non-linearity of the thermocouple 26, that is, compensation data. When the changeover switch 106A selects the thermoelectromotive force output from the amplifier 102, the thermoelectromotive force is converted into a digital signal by the A / D converter 108, and is further input to the compensation means 110 by the changeover switch 106B. The compensating means 110 corrects the linearity of the thermoelectromotive force of the thermocouple 26 using the compensation data stored in the memory means 114.

When the changeover switch 106A selects the cold junction temperature output from the amplifier 104, the cold junction temperature is converted into a digital signal by the A / D converter 108 and then guided to the latch 112 by the changeover switch 106B. This signal is temporarily stored in the latch 112. The output of the compensator 110 and the data stored in the latch 112 are added to the adder 11.
6, and the result is displayed on, for example, a digital display device 72C.

Since the compensation data used in the compensation means 110 varies depending on the type of the thermocouple 26, it is preferable that the memory means 114 previously store a plurality of compensation data corresponding to different types of thermocouples. In this case, the compensation data to be used may be determined based on the selection signal Sn supplied from the outside. If a plurality of compensation data are stored in advance in this way, even when the type of thermocouple is changed, it can be easily handled only by inputting the selection signal Sn, which is convenient.

[0049]

According to the first aspect of the present invention, as described above, the temperature near the cold junction of the thermocouple is detected by the temperature sensor, and the result is added to the thermoelectromotive force to detect the heater temperature. Therefore, even if the cold junction temperature changes, an accurate heater temperature can always be detected.

In this case, the heater current fluctuates in a pulse form.
Then, the thermoelectromotive force of the thermocouple may be affected and fluctuated.
possible. Therefore, at the time of the zero cross of the heater current,
The thermo-electromotive force is sampled when the heater current becomes zero.
Ring. Therefore, the heater temperature can be controlled with high accuracy, the uniformity of the product is improved, and the yield can be improved .

Since the detection accuracy is improved particularly over a wide temperature range, the lower limit temperature slightly lower than the set temperature is detected to monitor the heater temperature rising speed, and high-precision control is performed even in the case of two-stage heating. Becomes possible.

[0052] Temperature compensator that corrects the output of the temperature sensor emf, may be constituted by an analog circuit (請
Claim 2 ), a digital circuit may be used.
3 ). In the case of using a digital circuit, if the thermoelectromotive force and the temperature sensor output are selected by a changeover switch and input to the A / D converter, the sampling timing can be freely set by the changeover switch. A / D
Only one converter is required, and the configuration is simplified.

Since the linearity of the output of the thermoelectromotive force may not be good, data (compensation data) for correcting the linearity is stored in the memory means in advance, and the thermoelectromotive force is used by using this data. Is corrected, the accuracy of detecting the heater temperature is further improved ( claim 4 ). When the type of thermocouple to be used changes, a plurality of compensation data corresponding to different types of thermocouple are stored in advance in the memory means.
It is more convenient if one compensation data is selected and used ( claim 5 ).

[Brief description of the drawings]

FIG. 1 is an external view of a bonding apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a pulse heat power supply.

FIG. 3 is a diagram showing a heater current waveform and the like.

FIG. 4 is a diagram showing a heater current detection circuit;

FIG. 5 illustrates a display example of a display device.

FIG. 6 is a functional block diagram of a control circuit.

FIG. 7 is a diagram showing a temperature compensation unit;

FIG. 8 is a control timing chart.

FIG. 9 shows another embodiment.

FIG. 10 shows another embodiment.

[Explanation of symbols]

Reference Signs List 18 heater chip 26 thermocouple 30 transformer section 32 control section 34 welding transformer 58 temperature compensation section 60, 102, 104 amplifier 62 temperature sensor 64, 116 adder 72, 72A, 72B display device 110 compensation means 114 memory means A hot junction B cold junction T heater temperature P _O temperature profile T ₁₀ first predetermined temperature T ₂₀ second set temperature

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01K 7/12

Claims (5)

(57) [Claims] 1. A pulse heating device that presses a heater against a portion to be joined, supplies a pulse current to the heater to heat the heater, and feeds back the heater temperature to cause the heater temperature to follow a preset temperature profile. in heater temperature detecting device used in the equation bonding apparatus, a thermocouple hot junction of one end is fixed to the heater, a temperature sensor for detecting the temperature near the cold junction of the thermocouple, heat
A temperature compensator for adding the output of the temperature sensor to the thermoelectromotive force of the thermocouple sampled at the zero crossing point of the data current, a display device for displaying the output of the temperature compensator,
A heater temperature detecting device for a pulse heating type joining device, comprising: 2. A temperature compensating unit comprising: an analog amplifier for amplifying a thermoelectromotive force; an analog adder for adding an output of a temperature sensor to an output of the amplifier; and a display device for displaying an output of the adder in an analog manner. The heater temperature detecting device of the pulse heating type joining device according to claim 1 . A changeover switch for selecting one of a thermoelectromotive force and an output of a temperature sensor and sampling the thermoelectromotive force in synchronization with a heater current;
2. An A / D converter for converting a signal selected by the switch into a digital signal, and a digital adder for adding the A / D converted thermoelectromotive force and the output of the temperature sensor . Heater temperature detector for pulse heating type bonding equipment. 4. The memory device according to claim 3 , further comprising a memory means for storing compensation data for correcting the linearity of the thermoelectromotive force of the thermocouple, and said compensation data interposed between said A / D converter and a display device. And a compensating means for correcting the thermoelectromotive force using the compensation data, and correcting the A / D converted thermoelectromotive force using the compensation data. 5. The heater temperature detecting device according to claim 4 , wherein a plurality of correction data for different types of thermocouples are stored in the memory means, and compensation data for the thermocouple to be used is selected and used.