JPH1154905A - Pulse heat type junction device and method for controlling it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the quantity of heat transferred to a work at the time of joining the work to the section to be joined of a heater so as to prevent the flowing out of solder from the section to be joined by controlling the pressing force applied to the section to be joined upon detecting that the temperature of the heater reaches a set lower limit temperature which is lower than a temperature profile while the temperature of the heater is raised. SOLUTION: When a discriminating means 82 judges that the temperature of a heater reaches a first lower limit temperature while the temperature of the heater is raised, a CPU 70 sends a signal to a pressing force control means 68 and a cylinder 18 lowers a heater chip 22 and presses the chip 22 against a work with a set pressure. When the discriminating means 82 detects that the temperature of the heater reaches a second lower limit temperature as the heating step of the heater enters a second step, the control means 68 lowers the pressing force by lowering the air pressure supplied to the cylinder 18 by means of a pressure adjusting section 66. Since the pressing force is lowered when the temperature of the heater approaches the melting temperature of solder in such a way, the flowing out of molten solder to the outside from a section to be joined can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse heating type welding apparatus for locally heating and joining a joined portion by supplying a pulse current to a heater pressed against the joined portion,
It relates to the control method.

[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 joint is locally heated and melted by this heat, and joined. 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.

[0006]

Heretofore, conventionally, the supply of the heater current is started while the heater chip is pressed against the portion to be joined at a constant pressure, and the heating is started. Therefore, the heater is pressed against the part to be joined even during the heating, and the amount of heat transmitted from the heater to the part to be joined and further to the object (work) such as an IC is increased. Depending on the work such as an IC, it is required to minimize the heating at the time of joining. However, in the conventional apparatus, since the amount of heat transmitted to the work is large, there is a problem that the reliability of a product incorporating the work is reduced. there were.

In a conventional apparatus, a heater is heated to a joining temperature while being pressed against a portion to be joined with a constant pressing force, and is maintained at a constant set temperature for a constant time. Therefore, for example, in the case of solder joining, a constant pressing force is applied from before to after the solder is melted, so that the molten solder is pushed out from between the portions to be joined to the periphery thereof. For this reason, not only the amount of solder remaining in the portion to be joined is reduced, but also the molten solder flowing out therearound may cause a short circuit. For this reason, there has been a problem that the reliability of bonding is reduced.

Therefore, according to the present invention, the pressing force suitable for the changing heater temperature can be set to perform more precise and optimum joining control, and the amount of heat transmitted to the work at the time of joining can be reduced, or the molten material can be melted from the portion to be joined. It is a first object of the present invention to provide a control method of a pulse heating type bonding apparatus suitable for preventing a solder from flowing out.

It is a second object of the present invention to provide a control method of a pulse heating type joining apparatus which can reduce the amount of heat transmitted to a work at the time of joining to improve the reliability of a product. It is a third object of the present invention to provide a control method of a pulse heating type bonding apparatus that prevents molten solder from flowing out of a portion to be bonded and improves the reliability of solder bonding.

It is a fourth object of the present invention to provide a control method capable of reducing the amount of heat transmitted to a work at the time of joining and preventing molten solder from flowing out of a portion to be joined. It is a fifth object of the present invention to provide a bonding apparatus directly used for performing these methods.

[0011]

According to the present invention, the first object of the present invention is to heat a portion to be welded by pressing it with a heater and to feed back the heater temperature so that the heater temperature follows a preset temperature profile. In a control method used for a pulse heating type bonding apparatus for bonding a bonding portion,
A pulse heating type joining apparatus, wherein when the heater temperature rises, it is detected that the heater temperature has reached a lower limit temperature set lower than the temperature profile, and the pressing force of the heater on the portion to be joined is controlled. Control method.

The second object can be achieved by bringing the heater into contact with the portion to be joined and starting pressing after the heater temperature reaches the lower limit temperature. The third object can be achieved by detecting that the heater temperature has reached the lower limit temperature and reducing the pressing force of the heater which has been pressed against the portion to be joined and has already started heating.

[0013] A fourth object is to provide the temperature profile,
While setting to heat in two stages, a first-stage heating for heating to a first set temperature lower than the joining temperature of the joining portion and a second-stage heating for heating to a second set temperature higher than this,
When it is detected that the heater temperature has reached the first lower limit temperature lower than the first set temperature, the heater is brought into contact with the portion to be joined and pressing is started, and the heater temperature reaches the second lower limit temperature lower than the second set temperature. This is achieved by detecting the arrival and reducing the pressing force of the heater.

The same object is the case of single-stage heating in which the heater temperature rises substantially linearly from the start of heating to a set temperature higher than the bonding temperature.
This can also be achieved by setting a lower limit temperature, starting pressing the heater at the first lower limit temperature on the low temperature side, and reducing the pressing force at the second lower limit temperature.

A fifth object of the present invention is to provide a pulse heating type joining apparatus in which a portion to be joined is heated by pressing a portion to be joined with a heater and feeding back the heater temperature to follow a preset temperature profile. Heater temperature detecting means for detecting the heater temperature, memory means for storing the temperature profile and a lower limit temperature set lower than the temperature profile, and detecting that the heater temperature has reached the lower limit temperature during the rise. Determining means, pressure adjusting means for changing the pressing force of the heater on the bonded part, and pressing force control means for controlling the pressing force of the heater on the bonded part based on the output of the determining means. This can be achieved by a pulse heating type bonding apparatus characterized by comprising:

In this case, the pressing force control means detects that the heater temperature has reached the lower limit temperature by the judging means. Can reduce the amount of heat transmitted to the vehicle. Further, if the pressing force of the heater is reduced because the heater temperature has reached the lower limit temperature, the third object, that is, the molten solder can be prevented from flowing out of the portion to be joined.

Further, the temperature profile is to be heated in two stages. When the heater temperature reaches the first lower limit temperature during the first stage heating, pressing of the heater is started, and during the second stage heating, the second lower limit temperature is started. If the pressing force of the heater is reduced when the temperature reaches, both the purpose of reducing the amount of heat transmitted to the work and preventing the loss of the molten solder can be achieved.

[0018]

[Action] If the heater starts to be pressed against the joint at the lower limit temperature lower than the joining temperature (solder melting temperature) of the joint, the time during which the heater is in contact with the joint is shortened, and the amount of heat transmitted to the work is reduced. Decrease. Further, when the heater is pressed before reaching the lower limit temperature, if the pressing force of the heater is reduced at the lower limit temperature, it is possible to prevent the molten solder from being pushed out of the part to be joined and flowing away.

Further, two kinds of lower limit temperatures (first and second lower limit temperatures) are set, and when the first lower limit temperature is reached, the heater is pressed against the portion to be joined, and when the second lower limit temperature is reached, the heater is pressed. If the pressure is reduced, it is possible to simultaneously protect the work and prevent the molten solder from flowing out.

[0020]

Embodiment

FIG. 1 is an external view of a bonding apparatus according to an embodiment of the present invention, FIG. 2 is a simplified view of a control system thereof, and FIG. 3 is a heater current waveform (a) and its zero cross signal (b). )
FIG. 3 is a diagram showing 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.

In FIG. 1, reference symbol H indicates a head portion, and P indicates a pulse heat power source. The head unit H has a base 10, a driving unit 12 disposed above and facing the base 10, and a foot switch 14. The printed circuit board 16 is mounted on the base 10.
Is held. The driving section 12 has a movable section 20 which is moved up and down by an air cylinder 18. The movable section 20 holds a heater chip 22 located above the printed circuit board 16. The heater chip 22 descends integrally with the movable part 20 by the operator stepping on the foot switch 14 and supplying air to the air cylinder 18,
The printed board 16 is pressed with a predetermined pressure.

The heater chip 22 is made of molybdenum (M _O ) or the like, and is formed in a substantially U-shape as viewed from the front as shown in FIG. The heater chip 22 is heated by a pulse-like heater current I supplied from a power supply P.
The work includes a circuit pattern 24 on the printed circuit board 16, a solder layer 26 supplied by pre-soldering the circuit pattern 24 or dipping the circuit pattern 24 in a molten solder layer, and an IC or the like superimposed on the solder layer 26. The lead 28 is formed.

The heater chip 22 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 22, the solder layer 26 is melted. Thereafter, the heater current is cut off to cool the solder, and the solder is solidified before the heater chip 22 is raised. During this time, the heater temperature T is detected by the thermocouple 30 adhered to the heater chip 22. Further, the pressing force P of the heater chip 22 against the work can be changed in, for example, two stages as described later.

Next, the pulse heat power supply P will be described with reference to FIGS. In FIG. 2, 32 is a transformer unit, and 34 is a control unit. The transformer section 32 includes a welding transformer 36, and a primary winding of the welding transformer 36 is supplied with a 200 V single-phase AC voltage whose phase is controlled by the SCR stack 38. A low-voltage alternating current induced in the secondary winding of the welding transformer 36 is supplied to the heater chip 22.

The phase of the AC power supplied to the primary side of the welding transformer 36 is detected by the insulating transformer 40 and input to the phase control circuit 42 in the control unit 34. The phase control circuit 42 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 44. The gate signal G is converted into a gate drive signal of a predetermined voltage level by the SCR drive circuit 44 and
The CR is alternately turned on and off.

The current on the secondary side of the welding transformer 36, that is, the heater current I is determined by a current detector 46 using a Hall element or the like.
Is amplified to a predetermined voltage level by an amplifier (AMP) 47, and the signal i is input to an integrator 48 in the control unit 34. 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 46 is amplified and becomes a signal i, which is led to the base of the PNP transistor 50 and 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 42. 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. The reset signal R is a signal that is output with a slight time t _R behind the synchronization signal SYNC, and resets the capacitor 52 with a slight delay at the time of the zero crossing of the AC power supply.

The output voltage of the thermocouple 30 is amplified by an amplifier 58 as compensation means and guided to a changeover switch 56. The changeover switch 56 selects a signal indicating the heater current I output from the integrator 48 and a signal indicating the heater temperature T at a time interval, and sends the digital signal to the CPU 70 by the A / D converter 60. . Here, 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 selector switch 56 when the power supply frequency is 50H _Z is 100
At a sampling frequency of H _Z, 10 msec in other words
The heater current I is sampled every time.

On the other hand, since the output of the amplifier 58 indicating the heater temperature T is not subject to such regulation of the power supply frequency, the changeover switch 56 is set to, for example, 0.5 sec (500 msec, 2 msec).
It is sufficient to select for each _HZ ). The heater chip 22
When the power supply time is sufficiently short, it is preferable to shorten the sampling period of the heater temperature T, for example, to 0.2 seconds so that the graphic display of the temperature described later can be seen smoothly.

The temporal changes of the heater temperature T and the heater current I detected in this way can be graphically displayed on the display device 62 of the pulse heat power source 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 greater during the heating immediately after the start of energization, then the heater current is sharply in order to prevent overshoot of the current I, also constant heater current I after reaching a predetermined temperature T _O.

The air pressure output from the air pump 64 is supplied to the cylinder 18 provided in the driving section 12 of the head section H after being adjusted by the pressure adjusting section 66. That is, the constant air pressure output from the air pump 64 is adjusted to one or a plurality of predetermined pressures by the pressure adjusting unit 66, and the air cylinder 18
Supplied to The pressure adjusting section 66 can be formed by, for example, one or a plurality of relief valves operated by an electromagnetic valve. This pressure adjusting unit 66 is a pressing force control unit 6 of the control unit 34.
8 is controlled.

[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 62, the A / D converter 60, and the pressing force control unit 68 are connected via a bus 72. The input device 78 and the display device 64 are connected to the bus 72 via I / O interfaces 74 and 76, respectively. The foot switch 14 is also connected to the bus 72 via an interface 80.

The input device 78 inputs numerical values, instructions, and the like from a switch group 78A provided on the front surface of the case of the pulse heat power supply P shown in FIG. The display device 62 displays the change in the heater temperature and the like as described above. The display device 62 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 bus 72 is also connected with a judgment means 82, a memory means 84, and the like. The judging means 82 has a function of judging whether or not the heater temperature T has reached the set lower limit temperature, and changing the pressing force when the temperature has reached.

The memory means 84 stores a temperature profile, that is, a control pattern for the time of the target heater temperature, and a lower limit temperature for changing the pressing force.
The pattern, temperature, and time of the temperature profile can be changed by the input device 78. The determination means 84 may cause the CPU 70 to have the function.

[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. In FIG. 7, P ₀ indicates a temperature profile. This temperature profile P ₀ indicates a target temperature during heating. The broken line in the figure indicates the actual heater temperature T. With heating in two stages in this embodiment, rise-up time t _up1, t _up2 is provided a time required in the temperature rise.

A first lower limit temperature T _L1 = T ₁₀ -a determined by subtracting a fixed temperature from a first set temperature T ₁₀ (for example, 150 ° C.) in the first stage heating, and a second set temperature in the second stage heating. A second lower limit temperature T _L2 = T ₂₀ -b determined by subtracting a constant temperature from T ₂₀ (for example, 300 ° C.) is also set. Here, a and b can be set to, for example, 20 ° C., and the lower limit temperatures T _L1 and T _L2 can be set to 130 ° C. and 280 ° C.
These set values are also stored in the memory means 84.

When using this apparatus, first, a work is placed under the heater chip 22 as shown in FIG. 2, and the foot pedal 14 (FIGS. 1, 6) is depressed. Then, the heater 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 42 controls the gate of the SCR so as to have the phase angle θ. Note that the actual heater temperature T is higher than the temperature profile P ₀ before the start of heating. This means that the temperature profile P ₀ is 0 ° C. before the start of heating, whereas
This is because the actual heater temperature T is relatively high due to the outside air temperature or the residual heat of the previous bonding process.

When the judging means 82 detects that the heater temperature T has risen and has reached the first lower limit temperature TL1, the CPU 82
70 sends a signal to the pressing force control means 68. Then, the pressing force control means 68 sends a signal to the pressure adjusting section 66 to cause the cylinder 18 to supply a predetermined air pressure. Therefore, the cylinder 18
Lowers the heater chip 22 to press the work with the first set pressure p _R1 .

When the heater temperature T reaches the first lower limit temperature T _L1 , the CPU 70 starts counting the heating time t _h1 of the first-stage heating. Then, the second time from the lapse of this time t _h1
Enter step heating. During this second-stage heating, the heater temperature T becomes the second
When the determination means 82 detects that the temperature has reached the lower limit temperature T _L2 , the CPU 70 sends a signal to the pressing force control unit 68 to reduce the pressing force of the heater chip 22 to p _R2 . The pressing force controller 68 reduces the air pressure supplied to the cylinder 18 by the pressure adjusting unit 66 based on this signal, and sets the pressing force to p _R2 .

The CPU 70 starts counting the heating time t _h2 of the second-stage heating from the time when the heater temperature T reaches the second lower limit temperature T _L2 , and cuts off the heater current I when the time t _h2 elapses. I do. The interruption of the heater current causes the heater temperature T to start decreasing. The memory means 84 has a set temperature T _S lower than the solder solidification temperature when the heater temperature is lowered.
Is set in advance, and when the judging means 82 detects that the heater temperature T has dropped to this set temperature T _S , the CPU 70
Sends a signal to the pressing force controller 68 to raise the heater chip 22. That is, the heater chip 22 is separated from the work.

According to this embodiment, the heater chip 22
Is pressed against the work after rising to the first lower limit temperature TL1, so that the heating time of the work is shortened, and the work can be protected from thermal damage. Also, since the pressing force is increased during the first-stage heating, the heat of the heater chip 22 is smoothly transmitted to the work, so that the work can be heated quickly, and the pressing force is reduced near the solder melting temperature. It can be prevented from flowing out of the joined part. In addition, there is no possibility that the solder flowing out of the joints short-circuits the surrounding circuits.

[0043]

FIG. 8 is a timing chart showing another embodiment. In this embodiment, the rise-up times t _up1 and t _up2 in the temperature profile P ₀ of FIG. 7 are both set to zero. 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. According to this embodiment, the same effect as the embodiment of FIG. 7 can be obtained.

[0044]

FIG. 9 is a timing chart showing another embodiment. The temperature profile P ₀ shown here is for one-stage heating, and has a rise-up time t _up during heating.

In this embodiment, when the heater temperature rises,
The two minimum temperatures T _La and T _Lb are set. These lower limit temperatures T _La and T _Lb are, for example, constant heating a from heating set temperature T ₀ .
The temperature can be set as a value obtained by subtracting b. When the heater temperature T reaches the first lower limit temperature T _La (<T _Lb ), the pressing force of the heater chip 22 is set to a large pressure p _R1 , and when the heater temperature T reaches the second lower limit temperature T _Lb , the pressing force is set to p _R2 ( <
p _R1 ).

[0046] Then shut off the heater current with the lapse of heating time t _h, increases the heater chip 22 when the heater temperature T decreases to the set temperature T _S. According to this embodiment, substantially the same effects as in the embodiment of FIGS.

[0047]

FIG. 10 is a timing chart showing another embodiment. The temperature profile P ₀ shown here is one-step heating in a step-like manner, and the rise-up time t _up during heating is made zero.

In this embodiment, the lower limit temperature T _L = T ₀ -a which is lower than the heating set temperature T ₀ by a certain temperature is set. In FIG. 10A, when the heater temperature T reaches the lower limit temperature T _L , the heater chip 22 is pressed against the work with the pressing force p _R , and reaches the set temperature T _S during cooling after the heater current is interrupted. Then, the heater chip 22 is raised and separated from the work. Therefore, the contact time between the heater chip 22 and the work is shortened, and the work can be protected from thermal damage.

FIG. 10B shows a foot switch 1.
4 (FIGS. 1 and 6) is detected to be turned on, the heater chip 22 is lowered, and pressing is started with the pressing force p _R1 .
When the heater temperature T reaches the lower limit temperature _TL , the pressing force is reduced to _pR2.
(<P _R1 ). Therefore, it is possible to prevent the molten solder from flowing out from the portion to be joined to the surroundings, and it is less likely that the molten solder flowing out around the circuit will short-circuit the circuit.

[0050]

According to the first aspect of the present invention, as described above, the pressing force of the heater chip is controlled when the heater temperature reaches the lower limit temperature. Therefore, the pressing force suitable for the heater temperature during the change is set. And optimal joining can be performed.

In this case, if the heater is brought into contact with the portion to be joined and the pressing is started after the heater temperature reaches the lower limit temperature, the heating time of the portion to be joined is shortened, and the portion to be joined may be thermally damaged. Is reduced (claim 2). Also, if the pressing force is reduced from the time when the heater temperature reaches the lower limit temperature near the joining temperature of the part to be joined, it is possible to prevent the molten solder from flowing out from the part to be joined to the surroundings, and the surrounding circuit can be prevented. Can be prevented from being short-circuited.

When the temperature profile is two-stage heating, a first lower limit temperature lower than the first set temperature of the first stage heating and a second lower limit temperature lower than the second set temperature of the second stage heating are set. Then, pressing of the heater is started at the first lower limit temperature, and the second
Control can be performed to reduce the pressing force at the lower limit temperature (claim 3). In this case, it is possible to prevent the occurrence of thermal failure of the work and the outflow of the molten solder.

The temperature profile rises almost linearly from the start of heater heating to a set temperature higher than the bonding temperature.
Step heating can be used (claim 5). In the case of this one-stage heating, the first and second lower limit temperatures are set during the substantially linear heating, and the heater is brought into contact with the work at the first lower limit temperature.
By reducing the pressing force at the second lower limit temperature, it is possible to prevent thermal damage to the work and prevent molten solder from flowing out (claim 6).

According to the seventh aspect of the present invention, there is provided a bonding apparatus directly used for performing the above method. Here, if the pressing force control means starts the pressing of the heater when the heater temperature reaches the lower limit temperature, the heating time of the work is shortened, and the work can be protected from thermal damage. ). According to the apparatus of the ninth aspect, there is provided an apparatus which can be applied to the processing based on the temperature profile of the two-stage heating and can prevent the work from being thermally damaged and also prevent the molten solder from flowing out to the surroundings. can get.

[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 control timing chart.

FIG. 8 is a control timing chart showing another embodiment.

FIG. 9 is a control timing chart showing another embodiment.

FIG. 10 is a control timing chart showing another embodiment.

[Explanation of symbols]

Reference Signs List 18 Air cylinder 22 Heater chip 30 Thermocouple as heater temperature detecting means 32 Transformer unit 34 Control unit 36 Welding transformer 66 Pressure adjusting unit 68 Pressing force control unit 70 CPU 82 Judgment unit 84 Memory unit P0 Temperature profile T _L1 , T _La 1 lower limit temperature T _L2 , T _Lb 2nd lower limit temperature

Claims (9)

[Claims] 1. A pulse heat type joining apparatus for joining a joined portion by heating a portion to be joined by pressing it with a heater and feeding back a heater temperature to follow a preset temperature profile. In the control method, detecting that the heater temperature has reached a lower limit temperature set lower than the temperature profile while the heater temperature is increasing, and controlling the pressing force of the heater on the portion to be joined, wherein A control method for a heat-type bonding apparatus. 2. The method according to claim 1, wherein after the heater temperature reaches the lower limit temperature, the heater is brought into contact with the portion to be welded and pressing is started. 3. The method according to claim 1, wherein the pressing force of the heater is reduced by detecting that the heater temperature has reached a lower limit temperature near the joining temperature of the portion to be joined. 4. The temperature profile includes a first stage heating for heating to a first set temperature lower than a joining temperature of the portion to be joined and a second stage heating for heating to a second set temperature higher than the first set temperature. While heating in stages, it is detected that the heater temperature has reached the first lower limit temperature lower than the first set temperature, the heater is brought into contact with the portion to be joined and pressing is started, and the heater temperature is higher than the second set temperature. 2. The control method for a pulse heating type joining apparatus according to claim 1, wherein when the temperature reaches a low second lower limit temperature, the pressing force of the heater is reduced. 5. The control of the pulse heating type bonding apparatus according to claim 1, wherein the temperature profile increases the heater temperature substantially linearly from a start of heating of the heater to a set temperature higher than a bonding temperature of the bonding portion. Method. 6. A method according to claim 1, wherein the first and second heaters are in the middle of increasing the heater temperature.
A lower limit temperature is set, and it is detected that the heater temperature has reached the first lower limit temperature, the heater is brought into contact with the portion to be joined, pressing is started, and it is detected that the heater temperature has reached the second lower limit temperature. 6. The control method for a pulse heating type bonding apparatus according to claim 5, wherein the pressing force of the heater is reduced by heating. 7. A pulse heating type joining apparatus in which a portion to be joined is heated by pressing with a heater, and the heater temperature is fed back by following the heater temperature to follow a preset temperature profile. Heater temperature detecting means for detecting, a memory means for storing the temperature profile and a lower limit temperature set lower than the temperature profile, and a judging means for detecting that the heater temperature has reached the lower limit temperature during the rise thereof, Pressure adjusting means for changing the pressing force of the heater on the portion to be joined; and pressing force control means for controlling the pressing force of the heater on the portion to be joined based on the output of the determining means. Pulse heating type joining device. 8. The pulse heating type joining apparatus according to claim 7, wherein said pressing force control means causes said heater to come into contact with a portion to be joined and to start pressing when said judging means detects that the heater temperature has reached a lower limit temperature. 9. The pressure adjusting means can change the pressing force of the heater in at least two stages, and the memory means stores first and second lower limit temperatures on a low temperature side and a high temperature side,
9. The pulse heating method according to claim 8, wherein said pressing force control means causes the heater to come into contact with a portion to be joined when the heater temperature reaches said first lower limit temperature and starts pressing, and reduces said pressing force when said heater temperature reaches said second lower limit temperature. Joining equipment.