RU2115527C1 - Head for resistance spot miniature welding - Google Patents

Abstract

FIELD: welding equipment, applicable for connection of leads of electronic equipment units to lands of printed circuit boards, circuits and semiconductor materials. SUBSTANCE: head has a base, carriages with electrode assemblies installed on it, electrode-positioning mechanism, and electrode-positioning mechanism drive; the base is made as a plate with three carriages with electrode assemblies fastened to its lower surface, two of them are installed for radial displacement, and the third one is fixed; the first two carriages are installed at an angle of 90 deg relative to each other, and the third one-in the same plane aligned with the first carriage. The electrode-positioning mechanism represents a gear set kinematically linked with common reversing drive, one of the gear set wheels is installed on the electrode- positioning mechanism drive, and the other - on the axle of rotation common with the base and made with shaped lateral and lower surfaces, it also has two groups of carriers, each carrier of the same group is rigidly linked with moving carriage of the electrode shaped surface of gear-wheel, and each carrier of the other group has a movable joint through a swinging link of the electrode assembly to one of the electrodes and is engageable with the lower shaped surface of the gear-wheel. The swinging links are spring- loaded, shock-absorbing members are installed between the links and electrode holders. The electrode-positioning mechanism is furnished with rotation stops. The axle of rotation has a central hole. EFFECT: improved design of head for resistance miniature welding. 5 cl, 4 dwg

Description

 The invention relates to welding equipment and is intended to connect the findings of electronic products to the contact pads of printed circuit boards, circuits and semiconductor materials.

 A device for precision contact spot and relief micro-welding, which contains an electrode suspension made in the form of a parallelogram of two identical flat springs and having the ability to swing around a fixed axis, a movable rod connected to the actuator, a pressure mechanism and a work table mounted on a fixed base.

 The disadvantage of this device is that the latter is made according to a single-electrode circuit, as a result of which the welding process is possible when the welding current is supplied from a power source of one polarity to the electrode and the other to the contact area of the board. Therefore, with a large number of welds, the productivity will be low, since it is necessary to transfer the output from the power source from one contact pad to another.

 This disadvantage is largely eliminated in the installation for resistance spot welding [1], selected as a prototype. The installation comprises a bed, a movable carriage, a source of welding current, electrodes, each of which is equipped with a pressure drive, a site for installing a working gap between the electrodes.

 The prototype uses a two-electrode circuit (the principle of a split electrode), which provides welding only on one axis, for example, X. For welding on the other (and there is a need for this, since some electronic products contain conclusions on the coordinates X and Y), either a turn is required heads, or rearrangement of the board. In addition, the movement of the electrodes in the vertical plane and their extension are carried out from individual drives, and this is an increase in the weight of the structure, which is also facilitated by the presence of loads of pressure drives. Both shortcomings ultimately lead to reduced performance.

 The technical problem to be solved is the creation of a head for contact spot microwelding.

 The expected technical result consists in expanding the technological capabilities of the device and increasing its productivity (the number of welds per unit time).

The solution to the technical problem lies in the fact that in the presented head for contact spot microwelding containing a base, carriages with electrode assemblies, a mechanism for moving electrodes, a displacement drive, the base is made in the form of a plate, three carriages with electrode assemblies fixed to its lower surface, two with radially displaceable, and the third stationary, wherein the two first carriages mounted at an angle of 90 ^o to each other, and the third - in the same plane, coaxially with the first transfer mechanism electrodes etc. constitutes a gear pair kinematically connected with a common reversible drive, one of the wheels of which is mounted on the displacement drive, and the other on the axis of rotation common to the base and is made with profile side and lower surfaces, as well as two drove groups, each drove one group is rigidly connected with the moving carriage and interacts with the side profile surface of the gear wheel, and each carrier of the second group is movably connected through the rocking lever of the electrode assembly to one of the electrodes and interacts uet a bottom surface profile of a gear wheel, the rocker arms are sprung, between the lever and the electrode holders mounted damping member provided with the moving mechanism stops rotation, the rotational axis is formed with a central opening.

The use of a three-electrode circuit allows welding along the X and Y axes, while excluding the operation of turning the head through an angle of 90 ^o . Pairwise inclusion in the operation of the electrodes is provided by the movement of carriages with electrode assemblies along the guides by means of a movement mechanism.

The presence of a single reversible drive kinematically connected with the mechanism of vertical movement of the electrodes and their extension (setting the working gap), containing a gear wheel with two specially shaped surfaces that interact through carriers with electrode holders, provides:
a) software control of the movement of the electrodes by applying an electrical signal to the movement drive;
b) reducing the weight of the structure.

 The mounting of the electrode assembly on the swing arm allows the electrode to rise in a vertical plane, with a leaf spring being used as a drive.

 The presence of a shock-absorbing element is necessary to reduce the loads on the electrode assembly when the electrode touches the output of the product that is welded to the contact pad, since the speed of movement of the head is quite high at the required productivity of several welds per second.

 The rotation limiters of the gear wheel mounted on the displacement drive present in the head construction exclude the wheel turning beyond the working angles (-φ ... + φ) and, as a result, the accumulation of errors in the angle and damage to the carrier.

 The hole located in the center of the base is intended for the passage of the optical beam of the system for monitoring the relative position of the electrodes with each other and with respect to the conclusions of electronic products during welding to the contact pads of the board.

 In FIG. 1 shows a head for contact spot microwelding, side view; in FIG. 2 - the same, bottom view; figure 3 - the gear wheel of the drive mechanism with a carrier system and rotation limiters; figure 4 is a kinematic diagram of the movement of drove.

 Presented in FIG. 1 ... 4 head is designed for use in machines for surface mounting of printed circuit boards, circuits.

The head for contact spot microwelding contains a base 1, on the lower surface of which there are three carriages 2a ... 2c with electrode assemblies 3a ... 3c. The carriages 2a and 2b are mounted with the possibility of radial movement in the guides 4, and 2B is stationary. Moreover, the carriages 2b and 2b are placed at an angle of 90 ^{° to} each other, and 2b in the same plane is aligned with the carriage 2a. The mechanism for moving the electrodes 5a and 5b is a gear pair kinematically connected with a common reversible drive 6. The wheel 7 is mounted on the displacement drive, and the wheel 8 is on the axis of rotation 9 common with the base 1, and the wheel 8 is provided with profile side B and lower D surfaces. Drove 10a and 10b are rigidly connected to carriages 2a and 2b and interact with the surface 8 of wheel 8, and the drove 11a and 11b are movably connected via levers 13a and 13b of electrode assemblies 3a and 3b that swing on axes 12 and with electrodes 5a and 5b and interact with surface D wheels 8. The swinging levers 13a and 13b are spring-loaded by means of leaf springs 14. Between the levers 13a ... 13b and the electrode holders 15 ... 15v shock-absorbing elements are installed 16. The movement mechanism is equipped with a rotation limiter 17 that interacts with the microswitches 18a and 18b for disconnecting the pit electric Ia.

 The head for contact spot microwelding works as follows.

In the initial position (Fig.1,2):
- electrodes 5a and 5b, driven by carriers 11a and 11b, are raised;
- electrodes 5a ... 5c are separated to a maximum distance L _max .

Welding along the X axis (carried out by electrodes 5a and 5b). Wheel 8 when applying power to the electric drive rotates clockwise. Before turning through the angle “+ α”, the carrier 10a and 106 and 11a and 116, sliding along the profile surfaces B and D (FIGS. 3 and 4), only electrode 5a is moved (lowered), bringing it to the level of electrode 5c. Further rotation of the wheel 8 is accompanied only by the movement of the carrier 10a with the rest stationary, thereby ensuring the movement of the electrode 5a to the electrode 5b (setting the working gap L _work specified by the welding technology). Movement of carrier 10 a to point D on surface D, i.e. rotation through the angle “+ φ” corresponds to setting the minimum allowable welding technology gap L _min and the operation of the microswitch 18a through the rotation limiter 17.

 Welding along the Y axis (carried out by electrodes 5b and 5c). Wheel 8 when applying power of the opposite polarity to the electric drive moves starts to rotate in the opposite direction (reverse movement counterclockwise), first putting the electrodes in the initial state, and then likewise putting the electrodes 5b and 5c in working condition.

The proposed head for spot bonding has the substantial positive quality in comparison with the prototype, which allows for the exclusion of turning operation through 90 ^o and reducing weight by the use of a single reverse drive to increase the welding performance in several times.

Claims (5)

1. The head for contact spot microwelding containing a base, a carriage, electrode assemblies with swinging levers, a mechanism for moving electrodes, a movement drive, characterized in that it is provided with two additional carriages, and the base is made in the form of a plate, to which all three are fixed a carriage mounted thereon with the electrode assemblies, with two radially displaceable, and the third stationary, wherein the two first carriages mounted at an angle of 90 ^o relative to one another, and in that the third rail the plane is coaxial with the first one, the mechanism for moving the electrodes is made in the form of a gear pair kinematically connected to a common reversible drive, one of the wheels of which is mounted on the movement drive, and the other wheel with profile side and lower surfaces on the axis of rotation common to the base, as well as two groups drove, while each carrier of one group is rigidly connected with the movable carriage with the possibility of interaction with the side profile surface of the gear wheel, and each carrier of the second group is connected by means of a swing Osya electrode assembly of the lever with one of the electrodes to interact with the lower surface of the gear profile.  2. The head according to claim 1, characterized in that the swinging arms are spring loaded.  3. The head according to claim 1, characterized in that between the levers and the electrode holders shock absorbing elements are installed.  4. The head according to claim 1, characterized in that the movement mechanism is equipped with rotation limiters.  5. The head according to claim 1, characterized in that the axis of rotation is made with a Central hole.

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