JPH0367475B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a parallel gap welding device used in a precision pressure welding device for mounting electronic components on a board, and particularly to control of a welding power source thereof.

[Conventional technology]

Figure 4 shows, for example, "Abio Technology" 1982 Vol1
This shows the power supply circuit described in Nippon Avionics, where 1 is the board and 2 is the board.
3 is a conductive film which is a material to be bonded on a substrate, 3 is a material to be bonded such as a flat pack IC lead, 4,
5 is an electrode for flowing welding current, and 6 is an electrode holder. 7 is a welding machine power supply, 8 is a step-down and rectifier circuit, 9 is a storage battery, 10 is a timer for setting the energization time, 11 is a reference voltage generator for setting the welding voltage,
12 is a comparison amplifier that compares the reference voltage and the feedback voltage from the electrode and amplifies the difference; 13 is a DC amplifier; and 14 is a current control switch that adjusts the welding current.

The conventional constant voltage type parallel gap welding machine is constructed as described above, and the voltage between the electrodes 4 and 5 is set to a value set by the reference voltage generator 11.
The voltage from the electrode is fed back to the comparison amplifier 12, and the current value is adjusted by the current control switch 14 through the DC amplifier 13. At this time, the temperature of the conductive film 2 and the material to be joined 3 rises due to heat generated by the electricity, and after a time set by the timer 10, the current is cut off, and the material to be joined 3 and the conductive film 2 are joined.

[Problem that the invention seeks to solve]

In the above-mentioned parallel gap welding device that performs welding by keeping the inter-electrode voltage constant, the voltage between electrodes 4 and 5 is kept constant;
When the contact resistance between the electrodes 4 and 5 and the material to be joined 3 is large, the current decreases, and on the other hand, when the contact resistance is small, the current increases. As a result, the maximum temperature reached at the joint varied, causing variations in welding results. Furthermore, even if the same current flows, the temperature rise will be different due to differences in the shape of the materials to be joined 3, differences in the thickness of the conductive film 2, differences in contact resistance between the materials to be joined 3 and the conductive film 2, etc. occurred, and the welding results varied.
In particular, when the objects to be welded are micro parts such as electronic parts, the welding phenomenon progresses quickly and only slightly.
Welding results vary greatly even if the amount of heat input during 1 ms differs, and the various variations described above led to welding defects due to insufficient heat input or excessive heat input. Particularly in the case of excessive heat input, the materials to be joined 3 and the conductive film 2 may be fused, which has been a big problem.

This invention was made to solve this problem, and even if there are some variations in contact resistance between the electrode and the materials to be joined, variations in the shape of the materials to be joined, etc., uniform welding results are always obtained. The purpose is to obtain a parallel gap welding device that provides the following.

[Means for solving problems]

The parallel gap welding device according to this invention includes:
A detector that detects the voltage from the materials to be welded while electricity is being applied, a detector that detects the welding current, a circuit that calculates the state of the materials to be welded based on the detected voltage and current, and feeds the output of this circuit back to the welding machine power source. , is equipped with a circuit that controls energization.

[Effect]

In this invention, the voltage is directly detected from the welding material, the state change inside the welding material is calculated from this value and the welding current value, and when the calculation result reaches a predetermined value, a current cutoff signal is issued for welding. Feedback is given to the machine power source and welding is completed. Therefore, a stable welding result can always be obtained regardless of variations in contact resistance between the electrode and the materials to be joined, variations in the shape of the materials to be joined, etc.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention, and 1 to 7 are the same or equivalent parts as the above-mentioned conventional device. Reference numerals 15 and 16 are detectors for extracting voltage from the surface of the material 3 to be joined, and in this embodiment, a pair of needle-shaped probes are used, and these are arranged on both sides of the electrodes 4 and 5. Reference numerals 17 and 18 are mounting jigs for mounting this probe. 19 is a differential amplifier circuit that amplifies the difference between the outputs of voltage detectors 15 and 16; 20 is a current detector that detects the welding current and converts it into a voltage according to the current value; and 21 is a circuit that calculates the detected amount. In this embodiment, it consists of a circuit that calculates the resistance change of the materials to be joined.
22 is a resistance calculation circuit, 23 is a hold circuit that holds the resistance value after several seconds of energization, 24 is a difference circuit that makes a difference between the output from the resistance calculation circuit 22 and the output from the hold circuit 23, which changes every moment, and 25 is a certain constant value. A reference value setting circuit 26 is a comparison circuit that compares the outputs of the difference circuit 24 and the reference value setting circuit 25. 27 is a current cutoff signal generation circuit that converts the output from the comparison circuit into a welding current cutoff signal.

FIG. 2 is a waveform diagram for explaining the operation of the parallel gap welding apparatus constructed as described above. In the figure a, 28 is a conduction point starting point, 29 is a resistance hold starting point, 30 is a current cutoff point, and 31 is a welding current waveform. Reference numeral 32 in FIG. 3B is the voltage waveform of the output of the differential amplifier circuit 19. 33 in c of the figure is the waveform of the resistance difference output from the differential circuit 24;
34 is a reference value of the reference value setting circuit 25.

When welding is started after the electrodes 4 and 5 are brought into contact with and pressurized to the material 3 to be welded, the current value decreases as shown in the current waveform 31 due to the generation of electricity. At this time, the voltage waveform 32 does not change significantly. When the hold circuit 23 starts holding the resistance value at timing 29, several milliseconds after the welding machine power supply 7 and the contact between the welding material 3 and the conductive film 2 become stable, as the temperature of the joint increases, The specific resistance increases,
The resistance difference waveform 33 rises. As the energization time elapses, the contact resistance between the electrodes 4 and 5 and the material to be joined 3 decreases, and as a result, the current waveform 31 changes from decreasing to constant or increasing. At this time, voltage waveform 32
increases, so the waveform 33 of the resistance difference continues to rise. When the current is further continued, the upper part of the material to be joined 3 begins to melt, and a depression is formed. When this depression is formed, the cross-sectional area through which the current flows decreases, so the waveform 33 of the resistance difference rises rapidly, and when it reaches a predetermined reference value 34, the current cutoff signal generation circuit 27 sends a signal to the welding machine power supply. A cutoff signal is sent to and the welding ends.

FIG. 3 shows another embodiment in which a voltage detector is attached to the electrode itself, in which a conductor is insulated and attached to the electrode. The same operation can be obtained by using any method of attachment, such as adhesion, vapor deposition, or plating. This third
According to the figure, the desired purpose can be achieved even for minute parts that do not have a place for attaching the probe shown in FIG.

It goes without saying that the voltage detector according to the present invention is not limited to the above-mentioned embodiments, and can be modified as appropriate based on its purpose.

〔Effect of the invention〕

As explained above, this invention detects the voltage directly on the material to be welded while the current is being applied, monitors changes in its state, and feeds back the results to the welding machine power supply, thereby always providing the best and stable welding results. effective.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, FIG. 2 is a waveform diagram showing the operation of the embodiment of FIG. 1, and FIG. 3 is a voltage detector diagram showing another embodiment of the invention. Fig. 4 is a block diagram showing a conventional parallel gap welding device. In the figure, 15 and 16 are voltage probes, 19
2 is a differential amplifier circuit, 20 is a current detector, 21 is an arithmetic circuit, 22 is a resistance calculation circuit, 23 is a hold circuit, 24 is a difference circuit, 25 is a reference value setting circuit, 2
6 is a comparison circuit, and 27 is a current cutoff signal generation circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. In a parallel gap welding device that joins the two materials to be welded by bringing a pair of electrodes into contact with one of the materials to be welded and applying pressure and electricity to the two materials, one of the materials to be welded is a detector that detects the voltage from the source, a detector that detects the welding current, a circuit that calculates the state of the material to be welded based on the above detected amounts and sends out an output when it reaches a predetermined state, and the output of this circuit. A parallel gap welding device characterized in that it is equipped with a circuit that feeds back the power to the welding machine power source and cuts off the current. 2. The parallel gap welding apparatus according to claim 1, wherein the detector for detecting the voltage is constituted by a metal needle-like probe attached to both sides of a pair of electrodes or an electrode holder. 3. The parallel gap welding apparatus according to claim 1, wherein the detector for detecting voltage is constituted by a conductor attached to the electrode itself. 4 The circuit that calculates the detected amount is a circuit that divides the voltage by the current to calculate the resistance value, a circuit that holds that value, a difference circuit that subtracts the hold value and the current value,
2. The parallel gap welding apparatus according to claim 1, further comprising a circuit that sends an output when the differential output reaches a predetermined value.