JPH07266059A - Method for quality control of welding, and device thereof - Google Patents

Abstract

PURPOSE:To maintain an electrode in the best condition, and simultaneously to enable the judgment of a welding quality to be conducted by calculating a resistance value from voltage and current to be applied to a welding electrode, and judging the solenoid state of the welding electrode, comparing this value with a threshold. CONSTITUTION:The values of a voltage detected by a welding electrode 5 and a current detected by a current detector 20, are inputted to a CPU part, and a first resistance value is calculated. By comparing this resistance value with a first threshold value, when the resistance value is within the range of threshold value, it is considered that there is no soiling on the welding electrode 5, and the continuation of welding is judged. When the resistance value exceeds the threshold value, the stoppage of welding is judged. After the completion of welding, a very small amount of current is made to flow through the welding electrode 5 at a state in which an object to be welded is held, and current and voltage for a second feedback are detected again. The values of the detected current and voltage are inputted to a CPU part 22D, and a second resistance value is calculated. When comparing this second resistance value with a second threshold value, and when the second resistance value is within the range of the second threshold value, the welding quality of the object to be welded is judged satisfactory. When the second resistance value exceeds the second threshold value, the welding quality is judged defective.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is for repairing a printed circuit board, welding various sensors to an ultrafine wire or a ribbon material, and managing the dirty state of the welding electrode and the welding quality of the welding location. The present invention relates to a possible welding quality control method and apparatus.

[0002]

2. Description of the Related Art Generally, resistance welding is one of the methods for repairing a printed circuit board or joining various sensors to an ultrafine wire or a ribbon material. This resistance welding is a method in which a welding current is applied to the object to be welded, and the object is melted and joined by the jule heat generated at that time.

There are various types of power sources for resistance welding, one of which uses the energy stored in a capacitor connected to the output side of a rectifier to control the current with a transistor. There is a transistor system for welding.

As shown in FIG. 4, AC100V of the commercial AC power supply is stepped down to AC24V by the transformer 1, converted into DC24V by the rectifier 2 and charged in the capacitor 3. The energy stored in the capacitor 3 is supplied to the welding electrode 5 with its current controlled by the power transistor 4. Therefore, as shown in FIG. 5, when the welding electrode 5 comes into contact with the object to be welded, a welding current flows through the printed circuit board 10 as the object to be welded and the repair ribbon 11 to generate Jule heat. Resistance welded.

On the other hand, a wire (not shown) for pickup is connected to the welding electrode 5, the voltage V of the welding electrode 5 is detected by this, and this voltage V is amplified by the feedback amplifier 6. Then, it is input to the voltage control unit 7. In the voltage control unit 7, the voltage V is compared with the setting condition input from the welding condition setting unit 8 and voltage feedback control is performed so that a current flows through the power transistor 4 for a set time. As described above, the conventional method employs the voltage control method in which the welding current from the power transistor 4 and the time during which the current flows are controlled.

[0006]

However, as shown in FIG. 5, for example, the printed circuit board 10 is made of synthetic resin, and the disconnection points of the printed wiring formed on the printed circuit board 10 are When welding with the repair ribbon 11 for repair, the printed circuit board 10 is used during welding.
Is locally heated to about 1000 ° C. by the welding electrode 5. Therefore, the synthetic resin of the printed circuit board 10 at the heated portion is melted, sublimates and adheres to the lower surface of the welding electrode 5, and the insulating film 1 of the synthetic resin as the insulator is formed.
2 is formed.

As described above, when the welding electrode 5 is covered with the insulating film 12 and is in a so-called dirty state, no welding current flows through the welding electrode 5. Therefore, in this case, if the voltage control method is adopted, even if a voltage is applied to the welding electrode 5 and detected, no welding current actually flows through the object to be welded. A bad condition has occurred. In such a case, there is a problem that it is not possible to determine whether or not the welding current actually flows through the work piece, and furthermore, the state of defective welding cannot be found. Moreover, when determining the welding state, it was visually inspected, which was inconvenient.

[0008]

According to the present invention, there are provided a first threshold value which indicates an allowable range of a dirty state of a welding electrode, and a second threshold value which indicates a criterion for judging welding quality of an object to be welded. Is input to the CPU as a set value for determination, the first-time voltage and current applied to the welding electrode are respectively detected, and the first resistance value is detected from the detected first-time voltage and current. When the first resistance value is within the first threshold value indicating the contamination state of the welding electrode, the welding is continued, and when it exceeds the first threshold value, the welding is stopped. After the welding of the object to be welded, a weak current is applied to the welding electrode while sandwiching the object to be welded, and the second voltage and current applied to this welding electrode are detected. A second resistance value is calculated from the second voltage and current, and this second resistance value is the welding state of the work piece. The second time within the threshold, it is determined that good welding is a criterion that indicates a time exceeding the second threshold value is obtained so as to determine the welding defect.

Further, according to the present invention, a current detector for detecting a part of the welding current flowing through the welding electrode, a voltage detecting portion for detecting a voltage applied to the welding electrode, and a voltage and a current from the voltage detecting portion. The amplifying section for amplifying the current from the detector and the CPU section each have a first threshold value indicating the allowable range of the dirty state of the welding electrode and a second threshold value indicating the criterion for determining the welding quality of the workpiece. The threshold value and the set value for determination are set and input, and the first resistance value is calculated from the voltage and current values of the first time input to the CPU section from the amplification section, and the first resistance value and The contamination state of the welding electrode is determined by comparing with the first threshold value, and the second resistance value is calculated from the second voltage and current values input from the amplifying section after welding is completed.
The second resistance value and the second threshold value are compared to determine the welding quality of the object to be welded, and the display unit displays the determination result from the determination unit. .

[0010]

The current stored in the capacitor 3 is controlled by the power transistor 4, the welding voltage and the welding current are applied to the welding electrode 5, and the object to be welded is resistance-welded. Part of the welding current is detected by the current detector 20,
The welding voltage is detected by the welding electrode 5.

The detected feedback voltage and current values are both A / D-converted and input to the CPU section 22D, and the feedback value and the feedback control set value set in the CPU section 22D. Are compared and controlled, and the result is D / A converted and fed back to the power transistor 4. Therefore,
The power transistors 4 are controlled by a voltage control mode, a current control mode and a power control mode, respectively.

On the other hand, the first detected voltage and current are input to the CPU unit 22D, and the first resistance value R ₁ is calculated from these values. The calculated resistance value R ₁ is compared with the first threshold value. If the resistance value R ₁ is within the range of the first threshold value, it is determined that the welding electrode 5 is not contaminated and welding is continued. If it exceeds the threshold, it is judged that welding is stopped.

After the welding to the object to be welded is completed, a weak current is passed again with the object to be welded being sandwiched between the welding electrodes 5, and in the same manner as above, the current I and the voltage V for the second feedback are set. The detected current I and voltage V are detected again and the CPU 22
Input to D. A second resistance value R ₂ is calculated from these values and compared with a second threshold value.

When the second resistance value R ₂ is within the range of the second threshold value, the welding quality of the workpiece is judged to be good,
If the second threshold value is exceeded, the welding quality is judged to be poor.

[0015]

Embodiments of the present invention will be described in detail with reference to FIGS. FIG. 1 is a configuration diagram of a main part showing an embodiment of the present invention, FIG. 2 is a detailed configuration diagram of FIG. 1, and FIG. 3 is a flow chart showing an embodiment of the present invention. The same parts as those of the conventional example have the same names, are given the same reference numerals, and explanations thereof will be omitted.

1 and 2, 1 is a transformer, 2 is a rectifier, 3 is a capacitor, 4 is a power transistor, and in the case of this embodiment, a power MOSFET is used. It is used by connecting 10 MOSFETs in parallel and can output up to 1800A. 5 is a welding electrode. Reference numeral 9 denotes a charge control unit, which controls the phase of the thyristor of the rectifier 2 in order to maintain the output of the rectifier 2 at 24V DC.

Reference numeral 20 denotes a current detector. In the case of this embodiment, a hall current detector is used and is connected to the output side of the power transistor 4. This current detector 2
0 is for detecting a part of the welding current supplied to the welding electrode 5, and the detected current is three current feedback amplifiers 21 connected in parallel to each other in the amplifier 21.
It is applied to I _A , 21 I _B , and 21 I _C to obtain a feedback signal. Among them, the current fed back to a current feedback amplifier 21I _C, is output to the analog output terminal 19,
The welding waveform of the electric current is observed.

At the analog output terminal 19, as will be described later, other welding waveform voltages can be observed with a storage scope (not shown) or the like.

Here, the hole current detector is a device which can measure the magnetic flux generated in proportion to the current in a non-contact manner by the combination of a magnetic iron core and a magnetic sensor (hole element). The current for feedback may be detected by other methods without being limited to the above embodiment.

The amplifier section 21, in the case of this embodiment, the current feedback amplifier 21I _A ~21I _C, voltage feedback amplifier 21V _A ~21V _C, power feedback amplifier 21W _A through 21
W _C and a multiplier 21M, and a voltage detection unit that detects a part of the welding voltage by the current I fed back from the current detector 20 and the detection wire connected to the welding electrode 5 (Fig. The voltage V detected by (not shown) and fed back to the input side is input.

Here, in the embodiment, the amplifier 21 is provided with the multiplier 21M, the detected voltage and current are multiplied by this multiplier 21M to calculate the power, and the power control by this power is also performed. It is configured to be able to. That is,
Power feedback amplifiers 21W _{A to} 21W _C and multiplier 21
M is necessary for power control, and in this power control, the detected current and voltage are multiplied by the multiplier 21M to calculate power. As in the case of controlling the voltage and current of the calculated power, the power feedback amplifier 21
W _{A to} 21 W _C , A / D converter 22C, CPU unit 22
Power from D, D / A converter 22B and differential amplifier 22A
This power transistor 4 is fed back to the transistor 4.
Is configured to be feedback controlled.

Here, the resistance welding power source in this embodiment includes a transformer 1, a rectifier 2, a capacitor 3, a power transistor 4, a charge controller 9, an amplifier 21, a controller 22,
The welding condition setting unit 23 is provided and is provided with three control modes of voltage control, current control, and power control. Therefore, although the description including the power control is made below, the control mode is not limited in the present invention, and at least the voltage and the current for calculating the resistance value should be detected. is necessary.

Reference numeral 22 is a control unit, which controls the differential amplifier 22A and D /
A converter 22B, A / D converter 22C and CPU unit 2
2D, and the feedback values of the voltage V, the current I, and the power W from the amplification unit 21 are converted into digital signals by the A / D converter 22C and then input to the CPU unit 22D. The feedback values of the feedback voltage V, current I, and power W are compared with the feedback control voltage, current, and power set values respectively set by the welding condition setting unit 23 and set by the CPU unit 22D. The value and the feedback value are both controlled to be the same value, and this value is converted to an analog signal by the D / A converter 22B, compared and amplified by the differential amplifier 22A, and then fed to the power transistor 4. It is transmitted as a gate signal.

The welding condition setting section 23 initializes the setting values of the voltage, current, and power for feedback control that show the optimum welding conditions, and also shows the first range that shows the allowable range of the contamination state of the welding electrode 5. The threshold value and the second threshold value indicating the criterion for judging the welding quality of the workpiece are set as the set values serving as the criterion for judgment, and the voltage and current for feedback control are respectively set by the key switch 23A. Each set value of electric power and the set value for determination are input. Then, a control mode of any of voltage control, current control, and power control corresponding to the set value for feedback control is set.

Reference numeral 24 is a judging section for judging the contamination state of the welding electrode 5 to judge whether the welding is to be continued or stopped, and to judge whether the welding quality of the workpiece is good or not. The first section is inputted from the amplifying section 21. The voltage V, the current I, and the power W at the second time are converted into digital signals by the A / D converter 22C, respectively, and the CPU
The first resistance value R ₁ is calculated from the current I and the voltage V input to the section 22D.

The resistance value R ₁ is compared with a set value (resistance value) set as a reference for judgment to judge the contamination state of the welding electrode 5. The first resistance value R ₁ corresponds to the resistance value of the welding electrode 5 and represents the state at that location. In addition, the electric power input to the CPU unit 22D is
It is fed back to the power transistor 4 as power for power feedback control.

Similarly, after welding is completed, the second-time voltage V, current I, and power W input from the amplifier 21 are converted into digital signals by the A / D converter 22C, respectively, and the CPU
The second resistance value R ₂ is calculated from the current I and the voltage V which is input to the section 22D. The resistance value R ₂ is compared with a set value (resistance value) set as a reference for determining the welding quality, and the quality is determined.

The set values represented by the resistance values R ₁ and R ₂ which are the criteria for judgment are input to the threshold value setting section 25.
Actually, the upper and lower limits of these values are set by the key switch 23A and are input to the CPU section 22D as set values for determination.

Reference numeral 26 denotes a display unit, which is composed of an LCD 26A and an LED buzzer 26B, displays the determination result of the determination unit 24, and displays an emergency condition of the main body of the apparatus, for example, abnormal heating of the transformer 1, power transistor. An error message is displayed in case of short circuit breakdown of No. 4 or abnormality of welding operation itself, for example, overcurrent.

Reference numeral 27 denotes an I / O input / output terminal, which switches welding conditions from the outside through an I / O interface connector,
Various timing signals are output. Reference numeral 28 denotes a communication line end, which is configured so that welding conditions can be input from an external device (such as a personal computer), an output value can be displayed on the external device, and a determination result from the determination unit 24 can be output.

Next, the operation will be described. The voltage of AC100V from a commercial AC power supply (not shown) is stepped down to AC24V by the transformer 1 and then DC2 by the rectifier 2.
It is converted to 4V and the capacitor 3 is charged. In order to keep this charging voltage constant at 24V, the thyristor of the rectifier 2 is phase-controlled.

The energy stored in the capacitor 3 is
The current is controlled by the power transistor 4 and the welding current is supplied to the welding electrode 5. When the welding electrode 5 comes into contact with the object to be welded, a welding current flows through the printed circuit board 10 as the material to be welded and the repair ribbon 11, and jule heat is generated there to perform resistance welding.

[0033] Some of the welding current is detected by the current detector 20, the current is fed back to a current feedback amplifier 21I _A ~21I _C as the feedback current, from the current feedback amplifier 21I _C, analog output It is output to 19 and the welding current waveform is observed. Other current feedback amplifier 21
The output of I _A is sent to the differential amplifier 22A via the servo terminal 18.
To, the output of the current feedback amplifier 21I _B, E - field end 1
It is input to the A / D converter 22C via 8 and converted into a digital signal and input to the CPU section 22D.

On the other hand, at the welding electrode 5, a part of the welding voltage applied to this welding electrode 5 is detected by a pickup wire (not shown), and this voltage is used as a feedback voltage for a voltage feedback amplifier. It is returned to 21V _{A to} 21V _C. From the voltage feedback amplifier 21V _{C, the} voltage is output to the analog output terminal 19 and the welding voltage waveform is observed. The other output of the voltage feedback amplifier 21V _A is sent to the differential amplifier 22A of the control unit 22 via the servo terminal 18, and the output of the voltage feedback amplifier 21V _B is also sent to the differential amplifier 22A via the hold terminal 18. It is input to the A / D converter 22C of the control unit 22, converted into a digital signal, and input to the CPU unit 22D.

On the other hand, a part of the welding current I detected by the current detector 20 and the voltage V detected as the welding voltage applied to the welding electrode 5 are input to the multiplier 21M for feedback. The electric power W, which is the product of the voltage V and the current I, is calculated. This feedback power W is the power feedback amplifier 2
Input to 1W _{A to} 21W _C , power feedback amplifier 21W
_{From C,} it is output to the analog output end 19 and the welding power waveform is observed. The output of the other power feedback amplifier 21W _A is sent to the differential amplifier 22A of the control unit 22 via the servo end 18, and the output of the power feedback amplifier 21W _B is also sent to the differential end 22A of the control unit 22 via the hold end 18. A / D converter 22 of control unit 22
It is input to C, converted into a digital signal, and the CPU unit 22
Input to D.

Here, the voltage, current, and power values indicating the optimum welding conditions are initialized by the key switch 23A, and the set values for feedback control are input to the CPU section 22D. Current I for feedback input to 22D,
The value of the voltage V, the power W, and the set value of each are set to the differential amplifier 2
It is compared and amplified at 2A, and the set value and feedback current I,
Make sure that the values of voltage V and power W are the same,
A gate signal is sent to the power transistor 4, and the welding state is controlled by any one of the selected voltage control mode, current control mode, and power control mode. It should be noted that which control mode is selected is selected depending on the material and application of the workpiece.

Next, a method of controlling the welding quality will be described with reference to FIGS. 1, 2 and 3. Where the CPU
In the portion 22D, a first threshold value indicating a permissible range of the dirty state of the welding electrode 5 as a set value of the upper and lower limits from the key switch 23A and a second threshold value indicating a range of non-defective products as a criterion for determining the welding quality of the welding location. And the thresholds are set and input (step 50).

Next, an object to be welded (not shown) is placed on a table (not shown), and the welding electrode 5 is placed on the object to be welded.
With the load lightly applied, a preliminary initial voltage is applied for a short time so as not to damage the work piece (step 5).
1). At this time, the voltage V, the current I detected as described above and the electric power W (step 52) calculated from these values are input to the CPU unit 22D as described above.

Of the power W, current I, and voltage V input to the CPU section 22D, the first resistance value R is calculated from the current I and voltage V.
₁ is calculated (step 53). Then, the calculated first resistance value R ₁ is compared with the first threshold value,
A first determination is made to see the dirty state of the welding electrode 5 (step 54). That is, if it is within the range of the first threshold value, it is determined that the welding electrode 5 is not contaminated and it is determined that the welding should be continued, and the current is supplied to carry out the welding (step 56).

When the value exceeds the threshold value, that is, when the calculated resistance value R is larger than the set value, the tip surface of the welding electrode 5 is made of the synthetic resin insulating film 12 (FIG. 5). Since it is covered, the welding electrode 5 is determined to be contaminated and the welding is judged to be stopped, the welding is stopped (step 55), a message is displayed on the LCD 26A screen of the display unit 26, and the LED buzzer is displayed. An alarm is issued at -26B. Therefore, in this case, the welding electrode 5 is replaced or washed. The power W input to the CPU section 22D is used for power control of the power transistor 4.

After the welding of the object to be welded, a weak current is applied to the welding electrode 5 with the object to be welded being sandwiched, and the second current I and voltage V are detected again in the same manner as described above (step 57). This detected second current I and voltage V
The power W is calculated from the value of (step 5
8), respectively the current feedback amplifier 21I _B, voltage feedback amplifier 21V _B, after being amplified by the power feedback amplifier 21W _B, E - likewise control unit 22 via the shield terminal 18 A /
It is input to the D converter 22C, converted into a digital signal, and input to the CPU unit 22D.

Then, a second judgment is made to see if the welding quality of the work piece is good or bad. That is, the second resistance value R ₂ is calculated from the values of the current I and the voltage V input to the CPU section 22D (step 59), and this resistance value R ₂ and the second threshold value are compared (step 59). Step 60).

As a result, when the resistance value R ₂ is within the range of the second threshold value, it is judged that the welding quality of the workpiece is good (step 62). When the resistance value R ₂ exceeds the second threshold value, that is, when the calculated resistance value R ₂ is large, it is judged that the welding quality of the workpiece is poor (step 61). The work piece is judged to be defective. As a result, a message is displayed on the LCD 26A screen of the display unit 26, and an alarm is issued by the LED buzzer 26B.

When the welding of the object to be welded is completed in this way, if the next object to be welded is placed on the table, welding is started in the same procedure as continuing welding ( Step 63). In this way, the welding of all the objects to be welded is completed (step 64).

As described above, the current I, the voltage V, and the power W during welding are periodically sampled, and after the completion of welding, the average value is calculated, and the result is displayed on the LCD 26A screen. In addition, from the I / O input / output terminal 27, a product with good welding quality,
A defective product signal is output.

In the device of this embodiment, voltage control,
It has three control modes: current control and power control.
It is configured so that either one can be selected as needed. Therefore, the control mode can be selected according to the material and application of the workpiece.

[0046]

According to the present invention, the first threshold value indicating the allowable range of the contamination state of the welding electrode and the second threshold value indicating the criterion of the welding quality of the object to be welded are set for the determination. The first voltage and current applied to the welding electrode are respectively detected as values, and the first resistance value is calculated from the detected first voltage and current. When the first resistance value is within the first threshold value indicating the dirty state of the welding electrode, the welding is continued, and when the first resistance value exceeds the first threshold value, the welding is stopped and the object to be welded is stopped. After the welding is completed, a weak current is applied to the welding electrode while sandwiching the object to be welded, the second voltage and current applied to this welding electrode are detected, and the detected second voltage and Second from current
When the second resistance value is within the second threshold value, which is the criterion for indicating the welding state of the workpiece, it is determined that the welding is good, and the second threshold value is When it exceeds, it is judged as a welding failure. Therefore, in a series of welding processes, the welding electrode can be maintained in the best condition at all times and the welding quality can be judged at the same time based on the judgment result of the contamination state of the welding electrode. You can do it.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 shows an embodiment of the present invention and is a detailed configuration diagram of FIG.

FIG. 3 is a flow chart showing an embodiment of the present invention.

FIG. 4 is a configuration diagram showing a conventional example.

FIG. 5 is an explanatory diagram showing a conventional example.

[Explanation of symbols]

 4 Power Transistor 5 Welding Electrode 20 Current Detector 21 Amplifying Section 22 Control Section 22D CPU Section 23 Welding Condition Setting Section 24 Judging Section 25 Threshold Setting Section 26 Display Section

Claims (2)

[Claims] 1. A welding quality control method equipped with a resistance welding power source, comprising: a first threshold value indicating an allowable range of a dirty state of a welding electrode; and a second threshold value indicating a welding quality judgment standard of a workpiece.
Is inputted to the CPU as a set value for determination, the first-time voltage and current applied to the welding electrode are detected, and the detected first-time voltage and current are detected. The first resistance value is calculated from, and this first resistance value is
When it is within the first threshold value indicating the contamination state of the welding electrode, the welding is continued, and when the first threshold value is exceeded, the welding is stopped. A weak current is applied to the welding electrode while sandwiching the object to be welded, and the second voltage and current applied to the welding electrode are detected. From the detected second voltage and current, A second resistance value is calculated, and when the second resistance value is within a second threshold value which is a criterion for indicating the welding state of the object to be welded, it is determined that welding is good. A welding quality control method characterized by determining a welding failure when a threshold value is exceeded. 2. A welding quality control device having a resistance welding power source, a current detector for detecting a part of a welding current flowing through a welding electrode, and a voltage detector for detecting a voltage applied to the welding electrode. An amplification unit for amplifying the voltage from the voltage detection unit and a current from the current detector, respectively, and a first threshold value indicating an allowable range of the contamination state of the welding electrode in the CPU unit and an object to be welded. The second threshold value indicating the welding quality determination standard of is input as a set value for determination, and the first threshold value is input from the amplification unit to the CPU unit.
A first resistance value is calculated from the voltage and current values at the first time, and the first resistance value and the first threshold value are compared to determine the contamination state of the welding electrode. A second resistance value is calculated from the voltage and current values of the second time input from the amplification unit, and the second resistance value and the second threshold value are compared to compare the welding quality of the work piece. A determination unit for determining
A welding quality control device comprising: a display unit that displays the determination result from the determination unit.