Piezoresistor automatic welding workstation based on positioning and pressing structure

Abstract

The invention relates to the technical field of piezoresistor welding, and discloses a piezoresistor automatic welding workstation based on a positioning and pressing structure, the piezoresistor automatic welding workstation comprises a placing part, the placing part comprises a tool jig embedded in a workbench, and a placing cavity is formed in the tool jig. The piezoresistor automatic welding workstation based on the positioning and pressing structure can effectively solve the problems that in the prior art, in order to prevent an electrode plate and a chip element which are attached from displacement caused by external force or heat, welding quality and product performance are affected, auxiliary tools such as a clamp need to be used for fixing the electrode plate and the chip element and then conveying the electrode plate and the chip element into a reflow soldering furnace, and welding quality and product performance are affected. The problems of high product reject ratio, waste of raw materials, need of investment of extra manpower and time for rework detection and low economic benefit due to the fact that welding defects such as pseudo soldering, short circuit or open circuit can be caused by phenomena such as position deviation during chip mounting, infirm clamp fixation and element displacement in a reflow soldering process and the like in the prior art are solved.

Description

Technical Field

[0001] The invention relates to the technical field of varistor welding, and in particular to a varistor automatic welding workstation based on a positioning and pressing structure. Background Art

[0002] Varistors are usually made of semiconductor materials such as zinc oxide. Their resistance value changes significantly with the change of voltage at both ends. They are usually in the form of sheets or blocks, with two electrodes, connected in series or parallel with other components in the circuit. In the production of varistors, solder paste needs to be applied to the welding part between the electrode and the chip, and the two electrodes need to be aligned and attached to the chip, fixed with a fixture and transported to a reflow oven for heating.

[0003] In the prior art, in order to prevent the electrode sheets and chip components from being displaced by external force or heat after bonding, thereby affecting the welding quality and product performance, the three need to be fixed with the help of auxiliary tools such as clamps and then sent to the reflow oven. There are many operation links, and position deviations will occur during patching, the clamps are not firmly fixed, and components are displaced during the reflow process. These phenomena can all cause welding defects such as cold soldering, short circuit or open circuit, resulting in an increase in the product defect rate. This not only causes a waste of raw materials, but also requires additional manpower and time for rework inspection, which seriously affects the economic benefits of the company. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the present invention provides a varistor automatic welding workstation based on a positioning and clamping structure, which can effectively solve the problem in the prior art that in order to prevent the electrode sheets and chip components after bonding from being displaced by external force or heat, thereby affecting the welding quality and product performance, the three need to be fixed with the help of auxiliary tools such as clamps and then sent to a reflow soldering furnace. There are many operation links, and position deviations will occur during patching, the clamps are not firmly fixed, and components are displaced during the reflow soldering process, all of which can cause welding defects such as cold soldering, short circuit or open circuit, resulting in an increase in the product defective rate, which not only causes a waste of raw materials, but also requires additional manpower and time for rework inspection, resulting in low economic benefits.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0006] The present invention provides a varistor automatic welding workstation based on a positioning and pressing structure, comprising:

[0007] A placement part, the placement part includes a jig embedded in the workbench, a placement cavity is opened inside the jig, the jig is provided with a fixing component for fixing an external varistor element through the accommodation cavity opened inside the jig, and the placement cavity is connected with the interior of the accommodation cavity;

[0008] The welding part includes a cylinder, two of which are symmetrically distributed on the upper and lower sides of the jig, and the cylinder is fixedly connected to a hot press plate through a heat insulation plate arranged at the output end thereof, and a heat conductive block fitted with an external element is fixedly connected to the hot press plate on the side close to the jig, and the heat insulation plate is slidably connected to the side of the jig through a guide rail arranged on one side thereof, and a heating pipe is embedded in the hot press plate;

[0009] Among them, the fixing component includes a pressure block, which slides horizontally with the inside of the accommodating cavity through a sliding bar fixed on its side, and the side of the pressure block away from the placement cavity is rotatably connected to a rotating plate, and the side of the rotating plate away from the pressure block is rotatably connected to a vertical plate that slides vertically with the inside of the accommodating cavity.

[0010] Furthermore, a support rod is slidably connected to the inner wall surface of the placement cavity, and the support rod is connected to a T-shaped plate via an elastic member arranged on the upper surface.

[0011] Furthermore, two groups of the pressing blocks are provided, and the two groups of the pressing blocks are symmetrically distributed with the placement cavity as the center, and a clamping groove is provided on one side of the pressing block away from the rotating plate.

[0012] Furthermore, the accommodating cavity is rotatably connected to an L-shaped rod via a shaft fixed to its inner wall surface, the L-shaped rod is symmetrically distributed on both sides of the pressure block, and the circumferential outer surface of the shaft is sleeved with a torsion spring connected to the inside of the L-shaped rod.

[0013] Furthermore, a connecting rod which fits the outer surface of the L-shaped rod is fixedly connected to the side of the slide bar away from the pressing block.

[0014] Furthermore, a side pressure block is fixedly connected to a side of the L-shaped rod away from the connecting rod, and a side of the connecting rod close to the L-shaped rod adopts a curved surface design.

[0015] Furthermore, the lower surface of the vertical plate passes through the jig and is fixedly connected with a counterweight block, and a connecting piece is provided below the counterweight block.

[0016] Furthermore, the connecting member includes a fixed block, which is fixedly connected to the upper surface of a heat-conducting block near the bottom of the jig, and the fixed block is connected to a supporting plate via an elastic bent plate arranged on its upper surface.

[0017] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0018] The present invention is provided with a hot pressing plate, a heating pipe and a heat conducting block. Two hot pressing plates are symmetrically arranged above and below. The hot pressing plates are driven by the cylinders on the upper and lower sides to move simultaneously to the middle tooling and fixture. The internal heating pipe transmits heat to the inside of the heat conducting block in contact with the varistor element. The device combines the patch with the heating process, abandons the traditional welding method of fixing with a clip and then transporting it to the reflow oven, and uses the cylinder to achieve precise heating and extrusion of the electrode sheet 1, chip and electrode sheet 2 in the tooling and fixture, thereby improving production efficiency, reducing manual intervention, reducing the defective rate caused by human error, and being convenient, making the entire production process more compact and efficient. At the same time, the fixed component in the accommodating cavity ensures that the relative position of the electrode sheet and the chip is accurate during hot pressing, which is conducive to uniform melting and flow of the solder paste, ensuring the quality of the solder joints, reducing welding defects such as cold solder joints, leaking solder joints, and uneven solder distribution, improving the strength and conductivity of the solder joints, and enhancing the stability of the electrical and mechanical properties of the varistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 It is a schematic diagram of the three-dimensional structure of an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the structure of a hot pressing plate, a heating tube, a heat insulating plate and a fixing block according to an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the structure of the jig, counterweight and supporting plate according to an embodiment of the present invention;

[0023] Figure 4 For the embodiment of the present invention Figure 3 A schematic diagram of the structure with a partial enlargement at the center;

[0024] Figure 5 This is a schematic diagram of the structure of the connecting piece and the counterweight block according to an embodiment of the present invention;

[0025] Figure 6 It is a schematic diagram of the structure of the fixing assembly and the supporting plate according to an embodiment of the present invention;

[0026] Figure 7 It is a schematic diagram of the separation structure of the fixing assembly according to an embodiment of the present invention;

[0027] Figure 8 A cross-sectional view of a jig according to an embodiment of the present invention;

[0028] Fig. 9 This is a schematic diagram of the structure of a hot pressing plate, a heat conducting block and a supporting plate according to an embodiment of the present invention;

[0029] Fig.10 It is a schematic structural diagram of a support rod, an elastic member and a T-shaped plate according to an embodiment of the present invention.

[0030] The numbers in the figure represent respectively: 1. placement part; 11. tooling and fixture; 111. placement cavity; 112. accommodating cavity; 12. fixing component; 121. pressure block; 122. rotating plate; 123. vertical plate; 124. L-shaped rod; 125. torsion spring; 126. connecting rod; 127. side pressure block; 128. counterweight block; 13. support rod; 131. elastic member; 132. T-shaped plate; 2. welding part; 21. heat insulation board; 22. hot pressing plate; 221. heating pipe; 222. heat conducting block; 23. connecting part; 231. fixing block; 232. elastic bending plate; 233. supporting plate. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The present invention will be further described below in conjunction with the embodiments.

[0033] Example:

[0034] See also Figure 1-Figure 10 The present invention provides a technical solution: a varistor automatic welding workstation based on a positioning and clamping structure, comprising:

[0035] The placement part 1 includes a jig 11 embedded in the workbench, a placement cavity 111 is provided inside the jig 11, and the jig 11 is provided with a fixing component 12 for fixing an external varistor element through a receiving cavity 112 provided inside the jig 11, and the placement cavity 111 is connected with the interior of the receiving cavity 112; the length and width of the placement cavity 111 are both greater than the length and width of the external varistor element.

[0036] The welding part 2 includes a cylinder. Two cylinders are provided and symmetrically distributed on the upper and lower sides of the jig 11. The cylinder is fixedly connected to a hot press plate 22 through a heat insulation plate 21 arranged at its output end. The hot press plate 22 is fixedly connected to a heat conductive block 222 that fits with the external element on one side close to the jig 11. The heat insulation plate 21 is slidably connected to the side of the jig 11 through a guide rail arranged on one side thereof. A heating pipe 221 is embedded in the hot press plate 22; heat insulation plates 21 are provided on both the front and rear sides of the hot press plate 22 near the bottom, and the heat insulation plate 21 is provided only on the side close to the guide rail of the hot press plate 22 located above.

[0037] Among them, the fixing component 12 includes a pressure block 121, which slides horizontally with the inside of the accommodating cavity 112 through a sliding bar fixed on its side. The side of the pressure block 121 away from the placement cavity 111 is rotatably connected to a rotating plate 122, and the side of the rotating plate 122 away from the pressure block 121 is rotatably connected to a vertical plate 123 that slides vertically with the inside of the accommodating cavity 112.

[0038] The inner wall surface of the placement cavity 111 is vertically slidably connected with a support rod 13 , and the support rod 13 is connected with a T-shaped plate 132 via an elastic member 131 arranged on the upper surface, and the T-shaped plate 132 is vertically slidably connected to the inside of the support rod 13 .

[0039] Two groups of pressing blocks 121 are provided. The two groups of pressing blocks 121 are symmetrically distributed front and back with the placement cavity 111 as the center. A clamping groove is provided on one side of the pressing block 121 away from the rotating plate 122 .

[0040] The accommodating cavity 112 is rotatably connected to an L-shaped rod 124 via a shaft fixed to its inner wall surface. The L-shaped rod 124 is symmetrically distributed on the left and right sides of the pressing block 121 , and a torsion spring 125 connected to the inside of the L-shaped rod 124 is sleeved on the circumferential outer surface of the shaft.

[0041] A connecting rod 126 that fits the outer surface of the L-shaped rod 124 is fixedly connected to the side of the slide bar away from the pressing block 121 .

[0042] A side pressure block 127 is fixedly connected to the side of the L-shaped rod 124 away from the connecting rod 126. The side of the connecting rod 126 close to the L-shaped rod 124 adopts an arc surface design. A side pressure groove is provided on the side of the side pressure block 127 away from the L-shaped rod 124. The depths of the groove and the side pressure groove are both greater than the thickness of the chip.

[0043] The lower surface of the vertical plate 123 passes through the jig 11 and is fixedly connected to a counterweight block 128 , and a connecting member 23 is provided below the counterweight block 128 .

[0044] The connecting member 23 includes a fixing block 231 , which is fixedly connected to the upper surface of a heat conducting block 222 near the bottom of the jig 11 . The fixing block 231 is connected to a supporting plate 233 via an elastic bent plate 232 arranged on its upper surface.

[0045] In practical applications, the jigs and tools 11 are embedded inside the workbench, and multiple groups are provided so that welding operations can be performed simultaneously.

[0046] In the initial state, the cylinders on both the upper and lower sides of the welding part 2 drive the hot press plate 22 to the side far from the jig 11. The counterweight block 128 in the jig 11 has a certain weight. The vertical plate 123 slides vertically downward under the joint gravity of itself and the vertical plate 123. When the vertical plate 123 moves downward, it will drive the rotating plate 122 to tilt downward toward the side close to the vertical plate 123, and move as a whole to the side away from the chip. Similarly, the pressure block 121 is rotatably connected with the rotating plate 122, and moves synchronously with the rotating plate 122 to the side away from the chip. When the pressure block 121 moves, it slides horizontally with the inner wall surface of the accommodating cavity 112 through the sliding bar fixed on its side. Under the action of the torsion spring 125, the L-shaped rod 124 and the side pressure block 127 do not contact the piezoresistive element, and the fixed component 12 is completely hidden inside the accommodating cavity 112.

[0047] The process of loading the electrode sheet and chip:

[0048] The neatly stacked electrodes and chips are sucked into the placement cavity 111 in the jig 11 by using an optical positioning patch device. At this time, the support rod 13 is located at the bottom of this travel range under the action of gravity, and the T-shaped plate 132 is in an unfolded state under the action of the elastic member 131 (the elastic member 131 can be a leaf spring or a spring). The varistor elements to be welded are stacked in the order of electrode sheet 1, chip and electrode sheet 2, and the adjacent surfaces of the three are coated with solder paste by an external coating device. When placed, electrode sheet 1 is at the bottom, and the lower surface of electrode sheet 1 fits the upper surface of T-shaped plate 132.

[0049] The process of hot pressing welding varistor components:

[0050] The length and width of the chip are greater than the length and width of the electrode sheet. A card slot is provided on the side of the pressure block 121 away from the rotating plate 122, and a side pressure slot is also provided on the side of the side pressure block 127 close to the placement cavity 111. The depth of the side pressure slot is equal to that of the card slot, and both are greater than the thickness of the chip, which can adapt to the phenomenon of asynchronous fitting of the heat conductive blocks 222 on the upper and lower sides, and avoid damage to the varistor element. The inner wall edges of the card slot and the side pressure slot are both designed with arc edges, and the inner walls of the card slot and the side pressure slot are designed with flexible materials. There are six connecting ports between each placement cavity 111 and the accommodating cavity 112, two of which are used to penetrate the pressure block 121 and are located in the front and rear directions of the varistor element, and four are used to penetrate the side pressure block 127 and are located in the left and right directions of the varistor element. In the initial state, the elastic bent plate 232 is in an unfolded state, and the upper surface of the supporting plate 233 in this state is slightly lower than the upper surface of the heat conductive block 222.

[0051] During hot pressing, a heat insulation plate 21 is fixed at the output end of the cylinder, and the heat insulation plate 21 drives the hot pressing plate 22 to slide vertically on the guide rail. The cylinder at the bottom drives the hot pressing plate 22 to move vertically upward, and the cylinder at the top drives the hot pressing plate 22 to move vertically downward. The hot pressing plates 22 on both sides drive the heat conducting block 222 to move synchronously toward the middle jig 11. When the cylinder at the bottom drives the hot pressing plate 22 to move upward, the supporting plate 233 first fits with the lower surface of the counterweight block 128 hanging below, and the adjacent surfaces of the two are in a parallel state. As the heat insulation plate 21 continues to rise, the supporting plate 233 drives the counterweight block 128 to move vertically upward.

[0052] The counterweight block 128 is fixedly connected to the lower surface of the vertical plate 123, and drives the vertical plate 123 to move vertically upward inside the accommodating chamber 112. The side of the rotating plate 122 away from the pressing block 121 is lifted. Since the other side of the rotating plate 122 is rotatably connected to the pressing block 121, it is always in the same horizontal plane and slides inside this horizontal plane due to the limiting effect of the slide bar (the slide bar is parallel to the upper surface of the tooling 11 and is always in a horizontal state). Therefore, the rotating plate 122 moves toward the side of the placement chamber 111 as a whole, and pushes the pressing block 121 to move toward the side of the placement chamber 111. The rotating plate 122 is away from one end of the varistor element, and moves horizontally toward the side of the placement chamber 111 while moving vertically upward. The angle between the rotating plate 122 and the vertical plate 123 gradually decreases until the angle between the two reaches ninety degrees, the rotating plate 122 is in a horizontal state, and the upper surface of the counterweight block 128 fits the lower surface of the tooling 11. At this time, the side of the pressing block 121 away from the rotating plate 122 is no longer in the accommodating cavity 112, but extends to the inside of the placement cavity 111. The inner wall of the card slot opened in the middle of the outer surface of the pressing block 121 fits the side of the chip, and the outer surface of the pressing block 121 fits the side of the electrode sheet 1 and the electrode sheet 2.

[0053] At the same time, when the pressure block 121 moves horizontally toward the side of the placement cavity 111, the connecting rod 126 fixed at the end of the slide bar also moves synchronously toward the side of the placement cavity 111, and the arc edge end of the connecting rod 126 away from the slide bar begins to contact the outer surface of the L-shaped rod 124, and the L-shaped rod 124 begins to rotate around the shaft under the push of the connecting rod 126, and the side pressure block 127 at the outer end of the L-shaped rod 124 gradually moves toward the placement cavity 111, and the torsion spring 125 on the circumferential outer surface of the shaft begins to compress until the side pressure block 127 extends to the inside of the placement cavity 111, and the outer surface of the side pressure block 127 fits with the side edges of electrode sheet 1 and electrode sheet 2, and the inner wall of the side pressure groove opened on the outer surface of the side pressure block 127 fits with the side edge of the chip, and the side pressure block 127 and the pressure block 121 extend synchronously toward the inside of the placement cavity 111 and fit with the side edge of the varistor element. Each of the front and rear sides of the placement cavity 111 is equipped with a pressing block 121, and two side pressing blocks 127 are arranged on the left and right sides of each pressing block 121. The two pressing blocks 121 and the four side pressing blocks 127 are located on the left and right sides of the placement cavity 111. The four side edges of the varistor element are limited at the same time to ensure that the axis lines of the electrode sheet 1, the chip, and the electrode sheet 2 are consistent and completely in the middle position.

[0054] At this time, the fixing assembly 12 has completed the correction and limiting of the varistor element, the upper surface of the counterweight block 128 is in contact with the lower surface of the jig 11, and the lower surface of the counterweight block 128 is in contact with the upper surface of the supporting plate 233. The elastic bent plate 232 is still in the expanded state. When the cylinder below continues to push the hot pressing plate 22 upward, the cylinder above also continues to push the hot pressing plate 22 downward. The supporting plate 233 is fixed in this position and does not move. The fixing block 231 moves upward with the insulation plate 21. Therefore, the elastic bent plate 232 between the supporting plate 233 and the fixing block 231 is squeezed, and the elastic bent plate 232 begins to compress and deform. At the same time, the heat conductive block 222 enters into the placement cavity 111, and the upper surface of the heat conductive block 222 gradually becomes higher than the lower surface of the support rod 13. The heat conductive block 222 is composed of multiple blocks, which form a circle as a whole. In the vertical direction, the heat conductive block 222 is not set at the position where the support rod 13 exists, so that the upper surface of the heat conductive block 222 can smoothly penetrate the support rod 13 and fit with the lower surface of the electrode sheet.

[0055] When rising, the heat-conducting block 222 below enters the interior of the placement cavity 111, and the upper surface of the hot pressing plate 22 below contacts the lower surface of the support rod 13, and drives the support rod 13 to slide vertically upward. Since the side of the varistor element is limited in the space surrounded by the fixing assembly 12, the T-shaped plate 132 is still fixed in this position, and the support rod 13 is lifted upward by the hot pressing plate 22, and moves upward within its movable range. The elastic member 131 between the support rod 13 and the T-shaped plate 132 is squeezed and begins to deform elastically. At the same time, the heat-conducting block 222 above begins to approach the upper surface of the electrode sheet 2. When the upper surface of the heat-conducting block 222 below fits the lower surface of the electrode sheet 1, the lower surface of the heat-conducting block 222 above fits the upper surface of the electrode sheet 2, and the two apply relative forces, and the electrode sheet 1 fits tightly to the chip, and the electrode sheet 2 also fits tightly to the chip, so that the electrode sheet 1, the chip and the electrode sheet 2 are in close contact.

[0056] At the same time, the heat-conducting block 222 can transfer the heat of the heating tube 221 to the surface of the varistor element, apply pressure to the varistor element and provide high temperature, so that the solder paste between the varistor elements melts from solid to liquid. After the shape of the solder paste changes, the thickness occupied also changes, and the overall thickness of the electrode sheet 1, the chip, and the electrode sheet 2 becomes smaller. Under the action of pressure, the liquid solder fully wets the surface of the electrode sheet and the chip, fills the tiny gap between them, and metallurgically combines with the metal surface to form a firm solder joint. During the hot pressing process, the fixing component 12 always limits the electrode sheet 1, the chip and the electrode sheet 2 around, which can ensure that the electrode sheet 1, the chip and the electrode sheet 2 maintain accurate relative positions during the hot pressing process, and avoid displacement, offset or misalignment caused by external forces during hot pressing or thermal expansion of materials. This is crucial for the performance consistency of the varistor, which can ensure that the electrical connection between the electrode and the chip is stable and reliable, and improve the product yield.

[0057] The process of unloading after welding is completed:

[0058] After welding is completed, heating is stopped, and the cylinder drives on the upper and lower sides drive the hot pressing plate 22 to move vertically away from the jig 11. The liquid solder solidifies during the cooling process, firmly connecting the electrode sheet 1, the chip and the electrode sheet 2 together to form a whole. During the cooling process, the structure of the solder joint will gradually become finer, thereby improving the strength and conductivity of the solder joint.

[0059] During the descent of the hot press plate 22 below, the upper surface of the heat conductive block 222 gradually separates from the lower surface of the electrode sheet 1. After moving down a certain distance, the upper surface of the hot press plate 22 no longer exerts pressure on the support rod 13 to support it upward. The support rod 13 falls downward under the action of gravity and is at the lowest point within its travel range. At the same time, the elastic member 131 between the support rod 13 and the T-shaped plate 132 restores its elastic potential energy until the upper surface of the hot press plate 22 is completely separated from the lower surface of the support rod 13. Since the solder paste between the chip and the electrode sheet 1 melts when the electrode sheet 1 is pressed toward the chip during the pressing process, the gap between the two is reduced. Therefore, in this state, the lower surface of the electrode sheet 1 no longer contacts the upper surface of the T-shaped plate 132, and there is a certain gap between the two. At this time, the varistor is in a suspended state, supported by the surrounding fixed components 12, which is conducive to easily sucking the varistor from the inside of the placement cavity 111 during subsequent unloading.

[0060] At the same time, the elastic bending plate 232 gradually returns to its initial state, and the lower surface of the counterweight block 128 is still in contact with the upper surface of the supporting plate 233. As the hot press plate 22 below continues to move downward, the upper surface of the counterweight block 128 gradually separates from the lower surface of the jig 11, and the vertical plate 123 slides vertically downward under the gravity of itself and the counterweight block 128. When the vertical plate 123 moves downward, it will drive the rotating plate 122 to tilt downward toward the side close to the vertical plate 123. The angle between the rotating plate 122 and the vertical plate 123 gradually increases from ninety degrees, and the rotating plate 122 is transformed from a horizontal state to an inclined state and moves as a whole away from the chip. Similarly, the pressure block 121 is rotatably connected to the rotating plate 122, and moves synchronously with the rotating plate 122 to the side away from the chip. When the pressure block 121 moves, it slides horizontally with the inner wall surface of the accommodating cavity 112 through the sliding bar fixed on its side. After the L-shaped rod 124 loses the pressing effect of the connecting rod 126, it rotates around the shaft under the action of the torsion spring 125, the side pressure block 127 no longer contacts the varistor element, and the pressing block 121 no longer contacts the varistor element, and the fixing component 12 is completely hidden inside the accommodating cavity 112.

[0061] The welded varistor element loses its limit and falls slightly downward, and the lower surface of the electrode sheet 1 contacts the upper surface of the T-plate 132 again. The welded varistor element is sucked and unloaded by using an external optical positioning chip mounting device. In this process, since the area of ​​the placement cavity 111 is larger than the chip area, it is avoided that the surrounding of the varistor element and the inner wall of the placement cavity 111 are attached to each other during the unloading process to generate a large friction force, causing a jamming phenomenon during suction, resulting in solder paste wire drawing in the finished product, etc., thereby ensuring the welding quality.

[0062] In summary, the jig 11 has the following advantages when welding varistor elements:

[0063] Advantage 1: The welding workstation in the present invention combines the patch with the heating process, abandoning the traditional welding method of fixing with clips and then transporting to the reflow oven. It adopts two upper and lower hot pressing plates 22, and conducts heat to the heat-conducting block 222 near the side of the tooling fixture 11 through its internal heating tube 221, and uses the cylinder to achieve precise heating and extrusion of the electrode sheet 1, chip and electrode sheet 2 in the tooling fixture 11. It improves production efficiency, reduces manual intervention, reduces the defective rate caused by human errors, and is convenient, making the entire production process more compact and efficient.

[0064] Advantage 2: Before the upper and lower hot pressing plates 22 are attached to the varistor element, the positions of the electrode sheet 1, the chip and the electrode sheet 2 are corrected from the front and back and left and right directions through the pressing block 121 and the side pressing block 127 in the fixed component 12 to ensure that the axis lines of the three are consistent and in the middle position, providing position accuracy guarantee for high-quality welding. The action of the fixed component 12 is closely coordinated with the hot pressing process of the welding part 2. During the process of the hot pressing plate 22 pushing the counterweight block 128 up, the pressing block 121 and the side pressing block 127 gradually extend and limit the varistor element in the middle, and still maintain a fixed action until the welding is completed. This dynamic adaptation method can provide limit at the stage of fine-tuning the position of the varistor element, ensuring the stability of the position of the element before and during hot pressing. The fixed component 12 ensures that the relative position of the electrode sheet and the chip is accurate during hot pressing, which is conducive to uniform melting and flow of the solder paste, ensuring the quality of the solder joints, reducing welding defects such as cold solder joints, leaking solder joints, and uneven solder distribution, improving the strength and conductivity of the solder joints, and enhancing the stability of the electrical and mechanical properties of the varistor.

[0065] Advantage three, the fixing component 12 applies a limiting force uniformly on all sides of the varistor element, wherein the limiting force is relatively small, and limiting and correction are only achieved on all sides. Combined with the uniform hot pressing of the upper and lower hot pressing plates 22, the varistor element is subjected to uniform force at all parts during the hot pressing process, thereby preventing problems such as chip breakage and electrode sheet deformation caused by local uneven force, and reducing the production of defective products. At the same time, the card groove on the outer surface of the pressure block 121 and the inner wall of the side pressure groove on the outer surface of the side pressure block 127 are designed with flexible materials and have arc edges, thereby avoiding hard scratches or damage to the chip and electrode sheet during the fixing process, protecting the surface and internal structure of the component from damage, and improving product reliability.

[0066] Advantage 4: The elastic member 131 and the elastic bent plate 232 under the T-plate 132 play a role of buffering and adaptive adjustment during the hot pressing welding process. The elastic member 131 can be elastically deformed according to the hot pressing pressure and the thickness change of the varistor element (before hot pressing welding, the solder paste is solid, large in volume, and thicker in thickness. After hot pressing welding, the solder paste melts and the thickness becomes smaller), ensuring that the supporting force of the element during hot pressing is moderate and stable.

[0067] Advantage 5: The distance from the lower surface of the support rod 13 to the upper surface of the T-shaped plate 132 is determined by the compression and expansion of the elastic member 131. At the same time, the support rod 13 can slide up and down a certain distance inside the placement cavity 111. The up and down floating of the T-shaped plate 132 can effectively avoid the slight deviation when the cylinder moves, and avoid the state where the heat-conducting blocks 222 on the upper and lower sides are not in contact with the varistor element at the same time, causing excessive pressure and damage: when the upper heat-conducting block 222 is first in contact with the upper surface of the varistor element, the support rod 13 is at the bottom of its travel range, and the elastic member 13 1 is in the unfolded state, the lower surface of the piezoresistive element contacts the upper surface of the T-shaped plate 132. If the travel distance of the upper heat-conducting block 222 exceeds the normal, the elastic member 131 is compressed, and the piezoresistive element as a whole drives the T-shaped plate 132 to press downward; when the travel distance of the lower heat-conducting block 222 exceeds the normal, the support rod 13 moves upward within its travel range, the T-shaped plate 132 fits with the lower surface of the piezoresistive element and is fixed, and the elastic member 131 begins to compress, which can adjust the travel difference caused by the cylinder and ensure the stability during welding.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A varistor automatic welding workstation based on a positioning and clamping structure, characterized in that: include: A placement portion (1), the placement portion (1) comprising a jig (11) embedded in a workbench, a placement cavity (111) being provided inside the jig (11), the jig (11) being provided with a fixing component (12) for fixing an external piezoresistive element via a receiving cavity (112) provided inside the jig (11), the placement cavity (111) being communicated with the interior of the receiving cavity (112); A welding part (2), the welding part (2) comprising a cylinder, two cylinders being provided and symmetrically distributed on the upper and lower sides of the jig (11), the cylinder being fixedly connected to a hot pressing plate (22) via a heat insulating plate (21) provided at the output end thereof, the hot pressing plate (22) being fixedly connected to a heat conducting block (222) fitted with an external element on a side close to the jig (11), the heat insulating plate (21) being slidably connected to a side of the jig (11) via a guide rail provided on one side thereof, and a heating pipe (221) being embedded in the hot pressing plate (22); The fixing assembly (12) comprises a pressing block (121), the pressing block (121) being slidably connected to the interior of the accommodating cavity (112) via a sliding bar fixed on a side thereof, the pressing block (121) being rotatably connected to a rotating plate (122) on a side away from the placement cavity (111), and the rotating plate (122) being rotatably connected to a vertical plate (123) that slides with the interior of the accommodating cavity (112) on a side away from the pressing block (121).

2. According to claim 1, a varistor automatic welding workstation based on a positioning and pressing structure is characterized in that: The inner wall surface of the placement cavity (111) is slidably connected to a support rod (13), and the support rod (13) is connected to a T-shaped plate (132) via an elastic member (131) arranged on the upper surface.

3. The varistor automatic welding workstation based on the positioning and pressing structure according to claim 1 is characterized in that: Two groups of the pressing blocks (121) are provided. The two groups of pressing blocks (121) are symmetrically distributed with the placement cavity (111) as the center. A clamping groove is provided on one side of the pressing block (121) away from the rotating plate (122).

4. The varistor automatic welding workstation based on the positioning and pressing structure according to claim 3 is characterized in that: The accommodating cavity (112) is rotatably connected to an L-shaped rod (124) via a shaft fixed to the inner wall surface thereof; the L-shaped rod (124) is symmetrically distributed on both sides of the pressing block (121); and a torsion spring (125) connected to the inside of the L-shaped rod (124) is sleeved on the circumferential outer surface of the shaft.

5. The varistor automatic welding workstation based on the positioning and pressing structure according to claim 4 is characterized in that: A connecting rod (126) that fits the outer surface of the L-shaped rod (124) is fixedly connected to the side of the slide bar away from the pressing block (121).

6. The varistor automatic welding workstation based on the positioning and pressing structure according to claim 5 is characterized in that: A side pressure block (127) is fixedly connected to a side of the L-shaped rod (124) away from the connecting rod (126), and a side of the connecting rod (126) close to the L-shaped rod (124) is designed with an arc surface.

7. The varistor automatic welding workstation based on the positioning and pressing structure according to claim 1 is characterized in that: The lower surface of the vertical plate (123) passes through the jig (11) and is fixedly connected to a counterweight block (128), and a connecting piece (23) is provided below the counterweight block (128).

8. The varistor automatic welding workstation based on the positioning and pressing structure according to claim 7 is characterized in that: The connecting member (23) comprises a fixed block (231), the fixed block (231) being fixedly connected to the upper surface of a heat conducting block (222) located near the bottom of the jig (11), and the fixed block (231) being connected to a supporting plate (233) via an elastic bent plate (232) arranged on its upper surface.

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