A ball grid array package solder ball injection device and application method

Abstract

The invention discloses a ball grid array package solder ball injection device and an application method, which belongs to the field of microelectronic packaging, solder ball preparation and circuit printing, and includes a power system, a heat dissipation bracket, a crucible mechanism, a heating device, a nozzle, an inert gas supply system and a signal generating unit; the power system is used to drive the nozzle to reciprocate up and down, including a piezoelectric ceramic stack and a striker, the striker is fixedly connected to the nozzle, the signal generating unit includes a signal generator and a power amplifier, which is used to drive the piezoelectric ceramic stack to expand and contract, and then drive the nozzle to move up and down quickly; the crucible mechanism and the heating device are used to heat and melt the solder wire in the crucible; the heat dissipation bracket is used to reduce the heat transferred to the power system; the inert gas supply system is used to make the high-temperature liquid solder droplets ejected from the nozzle in an inert gas environment to prevent the high-temperature liquid solder droplets from oxidizing. The invention has various functions, is easy to use, has low cost and high reliability.

Description

Technical Field

[0001] The invention belongs to the technical field of microelectronic packaging, solder ball preparation and circuit printing, and in particular relates to a solder ball jetting device based on ball grid array packaging and an application method. Background Art

[0002] The existing solder ball spraying device has certain drawbacks. The device has a single working mode and can only spray droplets but cannot draw lines. It has special requirements for the solder materials used. The work process is long and the efficiency is low. The device parts have high precision requirements, are difficult to manufacture, and have high costs.

[0003] BGA tin planting: BGA is a new packaging technology developed in the 1990s. It is the most mature and applied high-sealing packaging technology. The characteristic of this technology is that solder balls are used to replace external lead frame wires. BGA is a surface mount package for multi-pin large-scale integrated circuits, in which spherical contacts are made in an array on the back of the substrate as pins and large-scale integrated circuits are assembled on the front of the substrate. In this new packaging technology, tin planting is a very critical part. In the electronics industry, laser welding is used in the ball planting process because it can heat locally and protect components from thermal shock. Laser ball planting technology realizes flux-free welding through high-precision laser focusing melting balls, which effectively improves the shortcomings of traditional screen printing ball planting, such as easy damage to small parts, difficult precision control, and easy contamination of devices by flux.

[0004] Nowadays, the technology used to implant solder balls onto pads is mostly laser ball implantation technology, which delivers a single solder ball with a diameter slightly larger than the nozzle to the nozzle through the rotation of the ball distribution disk, and then heats and melts the solder ball at the nozzle through a pulsed laser, and uses the back pressure inside the nozzle to spray the molten solder, so that the molten solder ball falls directly on the pad and forms a metal bond. Laser ball implantation equipment has the characteristics of high precision and non-contact, which is very suitable for high-precision packaging tasks. However, laser ball implantation equipment also has certain shortcomings, such as complex nozzle structure and high equipment cost. The ball distribution disk ball supply method it adopts leads to a low injection frequency, usually only a few balls per second.

[0005] Preparation of solder balls: In BGA packaging technology, the preparation of solder balls is the most fundamental and important part. In the past, the common ball making processes were centrifugal atomization, gas atomization, uniform droplet injection, and wire cutting and remelting. The centrifugal atomization method is to throw out the liquid metal under the action of centrifugal force to form metal droplets, and the thrown metal droplets enter the prepared cooling medium to form metal balls. This technology has high production efficiency, but poor controllability and low solder ball yield. The gas atomization method uses gas to impact liquid metal, converts the gas kinetic energy into liquid metal surface energy, and the gas is ejected from the nozzle to crush the liquid metal and solidify it to form metal particles. This method has similar characteristics to the centrifugal atomization method, that is, high production efficiency, but poor uniformity of solder balls. The droplet injection method applies pressure to the molten liquid metal and applies a disturbance of a specific frequency to make the liquid metal ejected from the nozzle to form a jet and break. This technology has high production efficiency and a high ball formation rate, but the equipment cost is high and the process is difficult to control. The wire cutting and remelting method is to make the solder alloy into tiny solder particles of equal mass, and then place these solder particles into a spheroidizing medium heated to a specific temperature, so that the particles are melted, spheroidized, cooled and solidified to form a spherical shape, and finally collected and cleaned to obtain BGA solder balls.

[0006] Although these technologies can obtain solder balls after final processing such as screening, the production process has many steps, the equipment is cumbersome to use, and the yield rate is not high. BGA packaging has very high requirements for the quality of solder balls. The more complicated the production process is, the lower the production efficiency of excellent solder balls is likely to be, and the greater the quality error of solder balls will be. The low cost, simplicity and reliability of the production process are the top priorities of solder ball making equipment.

[0007] Circuit printing: Nowadays, printed circuit technology is gaining more and more attention in the field of electronic manufacturing. With the advancement of science and technology, a variety of technologies that can generate conductive circuits have emerged, such as inkjet printing, electrofluid printing, extrusion direct writing, etc. These technologies have shown great potential in improving production efficiency, reducing costs and realizing complex circuit designs. However, these technologies usually use polymer inks based on metal nanoparticles. In order to ensure the bonding strength and conductivity of the printed circuits, many conductive circuits still need to be sintered after printing.

[0008] Sintering refers to the process of heating the particles in the conductive material to fuse together to form a continuous conductive path. This process is essential for improving the conductivity and mechanical stability of the circuit. However, the conductivity of the circuit after sintering may decrease. This is because during the treatment process, the conductive material may undergo oxidation or other chemical reactions, resulting in a decrease in conductivity. In addition, it needs to be carried out under specific temperature and time conditions, which increases the complexity of the process. Secondly, the post-processing process is relatively complicated. In order to ensure that the performance of the conductive material is optimal, the sintering process usually requires precise control of temperature, time and environmental conditions. This not only increases the difficulty of production, but may also lead to an increase in production costs. The sintering process may also have an impact on the substrate, especially for some flexible substrates, where excessively high temperatures may cause the substrate to deform or damage. This may become a bottleneck for large-scale production, limiting the scope of application of printed circuit technology.

[0009] The present invention provides a small solder ball injection device based on the water hammer principle and with a local inert gas protection function, which has the advantages of being easy to use, low cost, and high reliability. The device can directly form a high-temperature liquid solder metal wire under high frequency and low amplitude conditions, and can quickly form a solder circuit pattern on a circuit board. The conductive performance of the formed solder circuit is almost the same as that of the raw material, the conductive performance is excellent, and it is environmentally friendly and pollution-free. Summary of the invention

[0010] In view of the above problems existing in the prior art, the present invention proposes a ball grid array package solder ball injection device and an application method, which has a reasonable design, solves the shortcomings of the prior art, and has good effects.

[0011] A ball grid array package solder ball injection device comprises a power system, a heat dissipation bracket, a crucible mechanism, a heating device, a nozzle, an inert gas supply system and a signal generating unit;

[0012] The power system is used to drive the nozzle to perform up and down reciprocating motion. The power system includes a piezoelectric ceramic stack and a striker, and the striker is fixedly connected to the nozzle. The signal generating unit includes a signal generator and a power amplifier, which are used to drive the piezoelectric ceramic stack to expand and contract, and then drive the nozzle to move up and down rapidly through the striker; the crucible mechanism and the heating device are used to heat and melt the solder wire in the crucible; the heat dissipation bracket is used to reduce the heat transferred to the power system; the inert gas supply system is used to place the high-temperature liquid solder droplets sprayed from the nozzle in an inert gas environment to prevent the high-temperature liquid solder droplets from oxidizing.

[0013] Furthermore, the power system also includes a matrix-shaped shell, the top and bottom of the shell are respectively provided with an upper threaded through hole and a lower threaded through hole, and the inside of the shell is sequentially provided with a screw micrometer, an upper limit plate, a piezoelectric ceramic stack, a lower limit plate, a spring structure and a striker guide from top to bottom, and the top and bottom of the piezoelectric ceramic stack are respectively fixed with an upper top plate and a lower ball head, the upper top plate is semi-cylindrical, and the lower ball head is hemispherical; the shell, the upper limit plate and the lower limit plate are made of hard materials that are not easily deformed;

[0014] The screw micrometer is threadedly connected to the upper threaded through hole and then fixed for the second time by a nut; the top surface of the upper limit plate contacts the screw of the screw micrometer, and an arc groove matched with the upper top plate is opened in the middle of its bottom surface; the top surface of the lower limit plate is opened with a spherical blind hole matched with the lower ball head; the spring structure is arranged between the lower limit plate and the lower threaded through hole, and includes a large spring and a small spring sleeved inside the large spring, the bottom end of the large spring is fixedly bonded to the vicinity of the lower threaded through hole by epoxy resin, and is coaxial with the lower threaded through hole; the needle cap of the striker is in contact with the lower limit plate, the small spring is sleeved on the needle rod of the striker, the striker guide is threadedly connected with the lower threaded through hole, and extends into the interior of the large spring to resist the small spring, and the lower end of the needle rod of the striker extends out of the striker guide.

[0015] Furthermore, by rotating the rotating handle of the screw micrometer, the screw rod extends downward, pressing the upper limit plate to move downward, and at the same time the piezoelectric ceramic stack and the lower limit plate move downward together, and the large spring and the small spring are in a compressed state due to the pressure from the lower limit plate.

[0016] Furthermore, the heat dissipation bracket is made of a hard material that is not easily deformed, and its shape includes but is not limited to cylindrical and rectangular. In order to accelerate heat dissipation, the side of the heat dissipation bracket is set to have no wall surface, and a first through hole for the striker to pass through is opened at the top, and a threaded hole and a wire hole are opened at the bottom;

[0017] The top of the heat dissipation bracket is fixedly connected to the bottom of the housing of the power system by bolts, and pillars are respectively arranged on the four corners of the top of the heat dissipation bracket, so as to reduce the transfer of heat from the heat dissipation bracket to the housing.

[0018] Furthermore, the crucible mechanism is made of a material that does not react with high-temperature liquid solder, and includes a crucible and a crucible head. The crucible is provided with a liquid storage cavity, a second through hole and a blind hole that are connected from top to bottom, and the crucible head is provided with a third through hole. The liquid storage cavity is used to hold the high-temperature liquid solder, and the diameters of the second through hole and the third through hole are larger than the outer diameter of the nozzle by 0.1-0.2 mm, so that a small gap is formed between the second and third through holes and the nozzle.

[0019] The blind hole is filled with a high temperature resistant fiber material, the crucible head is threadedly connected to the blind hole, and the second through hole and the third through hole are coaxial; when the crucible head rotates into the blind hole, the upper surface of the crucible head compacts the high temperature resistant fiber material in the blind hole in cooperation with the nozzle;

[0020] The upper end of the crucible is threadedly connected to the threaded hole of the heat dissipation bracket;

[0021] The heating device is an annular high-temperature ceramic heating tube, which is sleeved on the outer wall of the crucible, and the positive and negative poles of the heating coil are connected to an external power supply for heating.

[0022] Furthermore, the nozzle is a slender tube column structure, the top end of the nozzle is fixedly bonded to the bottom end of the needle rod of the striker by epoxy resin, and the lower end of the nozzle passes through the liquid storage cavity, the second through hole and the third through hole of the crucible mechanism in sequence, and extends out of the third through hole by less than 2 mm;

[0023] The nozzle comprises a cylindrical tube made of a material that does not react with high-temperature liquid solder and a glass nozzle, wherein the upper end of the glass nozzle is inserted into the lower end of the cylindrical tube and fixedly bonded to the inner wall of the cylindrical tube by a high-temperature resistant glue;

[0024] The side wall of the upper half of the cylindrical tube is provided with an air vent and a liquid inlet hole connected to the atmosphere. The liquid inlet hole is immersed in the high-temperature liquid solder in the crucible liquid storage cavity, so that the high-temperature liquid solder flows into the nozzle through the liquid inlet hole, thereby making the liquid level in the nozzle level with the liquid level in the liquid storage cavity.

[0025] Furthermore, the inert gas supply system comprises a cylindrical gas shell, an inert gas bottle and a gas metal pipe, wherein a cavity is provided inside the gas shell, and an annular step structure is provided inside the cavity, wherein the vertical surface of the step structure is inclined downward and inward to form a conical gas outlet, and the cavity is communicated with the conical gas outlet;

[0026] A small hole is opened on the side wall of the gas shell, one end of the gas metal tube is inserted into the small hole, and the other end is connected to the inert gas bottle through a gas hose, and the inert gas enters the cavity from the inert gas bottle through the gas hose and the gas metal tube;

[0027] An annular gas shell bracket is provided at the upper end of the cavity, the gas shell bracket is fixed to the bottom end of the heat dissipation bracket by bolts, and the outer wall of the gas shell bracket is threadedly connected to the cavity wall; the crucible and the crucible head of the crucible mechanism are respectively located in the cavity and the conical air outlet, and the size of the gas shell is set according to actual needs, so as to adjust the distance from the nozzle of the glass nozzle to the bottom end of the gas shell;

[0028] Four layers of high temperature resistant metal mesh are placed on the lateral surface of the step structure. The high temperature resistant metal mesh is in contact with the outer wall of the crucible, and two adjacent layers of high temperature resistant metal mesh are separated by a high temperature resistant metal coil.

[0029] Furthermore, the signal generating unit is composed of a signal generator and a power amplifier. The signal generator edits a suitable waveform and transmits it to the power amplifier, which then connects the positive and negative electrodes of the piezoelectric ceramic stack through the positive and negative electrodes of the power amplifier to drive the power system.

[0030] The invention discloses an application method of a ball grid array package solder ball injection device, which adopts the above-mentioned ball grid array package solder ball injection device for BGA ball planting, and comprises the following steps: a pad with a solder dot is arranged below the device, so that the solder dot is directly opposite to the nozzle of a glass nozzle, and a suitable air shell size is adopted to make the nozzle flush with the bottom of the air shell; an annular high-temperature ceramic heating tube is used to increase the temperature of the liquid solder to 100°C to 200°C higher than the melting point of the solder, and during the high-temperature liquid solder injection process, the liquid level in the nozzle is kept at the same height; a signal generator and a power amplifier are used to drive a power system to continuously inject solder droplets, and the device is made to perform a two-dimensional planar motion according to a set operation trajectory, and finally a neat droplet array is formed on the pad.

[0031] An application method of a ball grid array package solder ball injection device, using the above-mentioned ball grid array package solder ball injection device to prepare solder balls, the steps are: a container for holding solder balls formed by injection is arranged below the device, a suitable air shell size is adopted to make the bottom of the air shell lower than the nozzle of the glass nozzle, an annular high-temperature ceramic heating tube is used to increase the temperature to 100°C to 200°C higher than the melting point of the solder, during the preparation of the solder balls, the liquid level in the nozzle is kept at the same height; after setting the injection frequency and injection strength in the signal generator, continuous injection is performed.

[0032] The invention discloses an application method of a ball grid array package solder ball injection device, which adopts the above-mentioned ball grid array package solder ball injection device for circuit drawing, and comprises the following steps: a plate is arranged below the device, and a suitable air shell size is adopted to make the nozzle flush with the bottom of the air shell; an annular high-temperature ceramic heating tube is used to increase the temperature to 100°C to 200°C higher than the melting point of the solder, and during the high-temperature liquid solder injection process, the liquid level in the nozzle is kept at the same height; the frequency and voltage parameters of the signal generator are adjusted to make the nozzle in a high-frequency and low-amplitude motion state, so that the liquid solder is extruded uniformly and continuously from the injection hole, and at the same time, the device is allowed to perform rapid two-dimensional planar motion according to the program setting, that is, various required two-dimensional circuit patterns are drawn on the plate.

[0033] Beneficial technical effects brought by the present invention:

[0034] 1. The device is small in size and easy to load and unload. The various components in the power system are equipped together. After the preload force is adjusted, there is no need to disassemble it again. Just rotate the micrometer to adjust the preload force. The heat dissipation bracket is fixed to the lower end of the power system by bolts, the crucible is fixed to the lower end of the heat dissipation bracket by its own threads, the heating tube is wrapped around the outer wall of the crucible, and the gas shell bracket is also fixed to the lower end of the heat dissipation bracket by bolts. The gas shell is fixed to the outer thread of the gas shell bracket through its own internal thread. These parts do not need to be frequently disassembled after installation; when replacing the nozzle, just unscrew the crucible head and remove the nozzle. The overall size is only 25.5cm*3.3cm*2.8cm.

[0035] 2. It can flexibly realize on-demand spraying and flexibly adjust the size of the generated high-temperature solder ball droplets, and the cost is extremely low, the solder ball droplet spraying rate is fast, and the precision is high. The present invention uses a signal generator to apply a waveform control to the piezoelectric ceramic. For spraying high-temperature solder ball droplets of different sizes, the action of the nozzle can be controlled by adjusting the voltage amplitude and frequency in the signal generator to realize high-temperature solder ball droplet spraying and on-demand spraying. It is also possible to spray high-temperature solder ball droplets of different diameters by replacing nozzles with different nozzle diameters, which is simple to operate. And the time to generate high-temperature solder ball droplets can reach 500 microseconds.

[0036] 3. Excellent local inert gas protection. In the process of solder wire melting and solidification, oxidation is very easy to occur to form an oxide film, which makes the sprayed high-temperature solder ball droplets and the formed solder balls uneven and not round. The present invention performs local gas protection at the nozzle, which minimizes the cost and is extremely convenient to disassemble and move. It avoids placing the entire device in an inert gas environment, which leads to cumbersome procedures when replacing parts and adjusting parameters. It avoids gas waste and is extremely convenient to disassemble. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is an overall cross-sectional view of a solder ball jetting device for ball grid array packaging in the present invention;

[0038] Figure 2 is a cross-sectional view of the power system of the present invention;

[0039] Figure 3 It is a schematic diagram of the structure of the heat dissipation bracket in the present invention;

[0040] Wherein (a) is a top view of the heat dissipation bracket; (b) is a front view of the heat dissipation bracket; (c) is a side view of the heat dissipation bracket; (d) is a bottom view of the heat dissipation bracket;

[0041] Figure 4 is a cross-sectional view of the crucible mechanism of the present invention;

[0042] Figure 5is a cross-sectional view of the nozzle in the present invention;

[0043] Figure 6 is a cross-sectional view of the inert gas supply system of the present invention;

[0044] Figure 7 It is a structural schematic diagram of the signal generating unit in the present invention;

[0045] Figure 8 It is an overall schematic diagram of a solder ball injection device for ball grid array packaging in the present invention;

[0046] Fig. 9 This is a schematic diagram of high-temperature liquid solder inside a crucible in an embodiment of the present invention;

[0047] Fig.10 Schematic diagram of the nozzle being flush with the bottom end of the gas shell in Embodiment 1 and Embodiment 4 of the present invention;

[0048] Fig.11 This is a schematic diagram of the effect of BGA ball planting in Example 1 of the present invention;

[0049] Fig.12 It is a schematic diagram of the effect of drawing lines on the circuit in Embodiment 4 of the present invention;

[0050] Among them, 1-shell; 2-screw micrometer; 3-upper limit plate; 4-upper top plate; 5-piezoelectric ceramic stack; 6-lower ball head; 7-lower limit plate; 8-large spring; 9-small spring; 10-striker; 11-striker guide; 12-heat dissipation bracket; 13-crucible; 14-gas shell bracket; 15-gas shell; 16-heating device; 17-air flow metal pipe; 18-air flow hose; 19-inert gas bottle; 20-glass nozzle; 21-crucible head; 22-cylindrical tube; 23-signal generator; 24-power amplifier; 25-power system; 26-signal generating unit; 27-nozzle; 28-inert gas supply system; 29-crucible mechanism; 30-high temperature resistant fiber material; 31-nut; 32-high temperature resistant metal coil; 33-high temperature resistant metal mesh; DETAILED DESCRIPTION

[0051] The specific implementation of the present invention is further described below in conjunction with specific embodiments:

[0052] A solder ball jetting device for ball grid array packaging, such as Figure 1 and 8 As shown, it includes a power system 25, a heat dissipation support 12, a crucible mechanism, a heating device 16, a nozzle 27, an inert gas supply system 28 and a signal generating unit 26;

[0053] The power system 25 is used to drive the nozzle 27 to perform up and down reciprocating motion, and includes a piezoelectric ceramic stack 5 and a striker 10, and the striker 10 is fixedly connected to the nozzle 27; the signal generating unit 26 includes a signal generator 23 and a power amplifier 24, which are used to drive the piezoelectric ceramic stack 5 to expand and contract, and then drive the nozzle 27 to move up and down rapidly through the striker 10; the crucible mechanism and the heating device 16 are used to heat the solid solder wire to melt it; the heat dissipation bracket 12 is used to reduce the heat transferred to the power system 25; the inert gas supply system 28 is used to place the high-temperature liquid solder droplets sprayed from the nozzle 27 in an inert gas environment to prevent the high-temperature liquid solder droplets from oxidizing.

[0054] Specifically, Figure 2 As shown, the power system 25 also includes a matrix-shaped shell 1, the top and bottom ends of the shell 1 are respectively provided with an upper threaded through hole and a lower threaded through hole, and the inside of the shell 1 is sequentially provided with a screw micrometer 2, an upper limit plate 3, a piezoelectric ceramic stack 5, a lower limit plate 7, a spring structure and a striker guide 11 from top to bottom, and the top and bottom ends of the piezoelectric ceramic stack 5 are respectively fixed with an upper top plate 4 and a lower ball head 6, the upper top plate 4 is semi-cylindrical, and the lower ball head 6 is hemispherical; the shell 1, the upper limit plate 3 and the lower limit plate 7 are hard materials that are not easily deformed, such as stainless steel;

[0055] The screw micrometer head 2 is threadedly connected to the upper threaded through hole and then fixed for the second time by a nut 31. The nut is located inside the shell and is threadedly connected to the screw micrometer head 2 to ensure that the position of the screw micrometer head will not change due to the action of the lower end force; the top surface of the upper limit plate 3 is in contact with the screw of the screw micrometer head, and an arc groove adapted to the upper top plate 4 is provided in the middle of its bottom surface, and a spherical blind hole adapted to the lower ball head 6 is provided on the top surface of the lower limit plate 7 to ensure that the piezoelectric ceramic stack 5 is well matched with the upper and lower end structures during the rotation and downward movement of the screw micrometer head 2, so that the piezoelectric ceramic stack 5 will not deviate left and right to cause an unstable center of gravity, so that the overall structure can ensure good symmetry;

[0056] The spring structure is arranged between the lower limit plate 7 and the lower threaded through hole, and includes a large spring 8 and a small spring 9 sleeved inside the large spring 8. The bottom end of the large spring 8 is fixedly bonded to the vicinity of the lower threaded through hole by epoxy resin and is coaxial with the lower threaded through hole; the needle cap of the striker is in contact with the lower limit plate 7, the small spring 9 is sleeved on the needle rod of the striker and abuts against the needle cap of the striker, the striker guide 11 is threadedly connected with the lower threaded through hole, and extends into the large spring 8 to abut against the small spring 9. A through hole is provided in the striker guide 11, and the lower end of the needle rod of the striker extends downward through the through hole to the striker guide 11.

[0057] By rotating the rotating handle of the screw micrometer 2, the screw rod is extended downward, pressing the upper limit plate 3 to move downward, and the piezoelectric ceramic stack 5 and the lower limit plate 7 move downward together. Due to the arc grooves and spherical blind holes of the upper and lower limit plates, these components are all on a center line. The large spring 8 is always in a compressed state due to the pressure received from the lower limit plate 7, and the small spring 9 is between the striker guide 11 and the striker needle cap, and the striker needle cap is in contact with the bottom surface of the lower limit plate 7. The small spring 9 is also subjected to the pressure brought by the downward movement of the lower limit plate 7, and the small spring 9 is also in a compressed state. Since the small spring 9 is in a compressed state, the striker needle cap is always supported by the small spring 9 and in contact with the lower limit plate 7. As a result, the entire structure has a certain preload force, and the various components cooperate with each other.

[0058] Specifically, the heat dissipation bracket 12 is made of a hard material that is not easily deformed, such as stainless steel, and the heat dissipation bracket is designed to be a shape that is easy to dissipate heat, and its shape includes but is not limited to cylindrical and rectangular. In order to speed up heat dissipation, the side of the heat dissipation bracket is set to have no wall surface; Figure 3 As shown, the heat dissipation bracket is rectangular, and a pair of opposite side surfaces thereof have no wall surface, and the other pair of side surfaces are provided with slot-shaped holes, so as to ensure the rigidity of the heat dissipation bracket as a whole and dissipate the heat transferred by the heating device 16 to the maximum extent. The top of the heat dissipation bracket 12 is provided with a first through hole for the striker to pass through, and the bottom end is provided with a threaded hole and a wire hole, so as to facilitate the connection with the crucible 13 and the gas shell bracket 14 and the lead-out of the wires related to the heating device 16;

[0059] The top of the heat dissipation bracket 12 is fixedly connected to the bottom of the shell of the power system 25 by bolts, and pillars are respectively provided at the four corners of the top of the heat dissipation bracket 12, so that a gap is generated in the middle when the heat dissipation bracket and the shell 1 are bolted together, thereby reducing the heat transfer from the heat dissipation bracket 12 to the shell 1 to avoid affecting the performance of the piezoelectric ceramics.

[0060] The needle rod of the striker passes through the first through hole and extends into the upper part of the heat dissipation bracket 12 .

[0061] Specifically, the crucible mechanism 29 is made of a material that does not react with high-temperature liquid solder, such as stainless steel. Figure 4 As shown, it comprises a crucible 13 and a crucible head 21. The crucible 13 is provided with a liquid storage cavity, a second through hole and a blind hole in a sequential manner from top to bottom. The crucible head 21 is provided with a third through hole. The liquid storage cavity is used to hold high-temperature liquid solder. The diameters of the second through hole and the third through hole are larger than the outer diameter of the nozzle 27 by 0.1-0.2 mm, so that a small gap is formed between the second and third through holes and the nozzle.

[0062] The blind hole is filled with a high temperature resistant fiber material 30, the outer wall of the crucible head 21 is threadedly connected to the inner wall of the blind hole, and the second through hole and the third through hole are coaxial to ensure the smooth movement of the nozzle 27; when the crucible head 21 rotates into the blind hole, the upper end plane of the crucible head 21 compacts the high temperature resistant fiber material 30 in the blind hole and the nozzle 27, and the function of the high temperature resistant fiber material 30 is to prevent the high temperature liquid solder in the liquid storage cavity from leaking downward through the gap between the second through hole and the nozzle;

[0063] The outer side wall of the upper end of the crucible 13 is threadedly connected to the threaded hole of the heat dissipation bracket 12;

[0064] The heating device 16 is an annular high-temperature ceramic heating tube, the inner diameter of which is one millimeter larger than the outer diameter of the crucible 13, so that the heating tube is sleeved on the outer wall of the crucible 13. Although the inner diameter of the heating tube is larger than the outer diameter of the crucible 13, the heating tube is very light and the positive and negative electrodes are plastic. After the positive and negative electrodes of the heating tube are led out to the power supply and bent, they are pulled by external forces and will not fall off at will. The positive and negative electrodes of the heating coil are connected to an external power supply for heating.

[0065] Specifically, Figure 5 As shown, the nozzle is a slender tube column structure, the top of the nozzle is bonded and fixed to the bottom of the needle rod of the striker, and the lower end of the nozzle passes through the liquid storage cavity, the second through hole and the third through hole of the crucible mechanism 29 in sequence, and extends out of the third through hole by less than 2 mm;

[0066] The nozzle includes a cylindrical tube 22 that does not react with high-temperature liquid solder and a glass nozzle 20. The upper end of the glass nozzle 20 is inserted into the lower end of the cylindrical tube 22 and fixedly bonded to the inner wall of the cylindrical tube 22 by a high-temperature resistant adhesive. The glass nozzle 20 is made of high-temperature resistant glass material, which is formed by heating, stretching and grinding the glass tube. The diameter of the central nozzle hole of the nozzle ranges from tens of microns to hundreds of microns.

[0067] The upper side wall of the cylindrical tube 22 is provided with a liquid inlet and an air vent connected to the atmosphere. The liquid inlet is immersed in the high-temperature liquid solder in the crucible liquid storage chamber, so that the high-temperature liquid solder flows into the nozzle through the liquid inlet, thereby making the liquid level in the nozzle level with the liquid level in the liquid storage chamber.

[0068] like Figure 6 As shown, the inert gas supply system 28 includes a cylindrical gas shell 15, an inert gas bottle 19 and a gas flow metal tube 17. A cavity is provided inside the gas shell 15, and an annular step structure is provided in the cavity. The vertical surface of the step structure is inclined downward and inward to form a conical gas outlet, and the cavity is communicated with the conical gas outlet.

[0069] A small hole is opened on the side wall of the gas shell. One end of the gas metal tube is inserted into the small hole, and the other end is connected to the inert gas bottle 19 through a gas hose. The inert gas enters the cavity from the inert gas bottle 19 through the airflow hose 18 and the airflow metal tube 17; the purpose of the conical air outlet is to allow the inert gas to converge toward the central axis when it flows out, so that the spray hole is surrounded by inert gas.

[0070] An annular gas shell support 14 is provided at the upper end of the cavity, and the gas shell support 14 is fixed to the bottom end of the heat dissipation support by bolts, and the outer wall of the gas shell support 14 is threadedly connected to the cavity wall. This design is for the convenience of disassembly of the gas shell 15 and the internal parts wrapped by the gas shell, such as the crucible; in addition, the inner diameter of the annular gas shell support 14 is larger than the outer diameter of the heating tube, so that the heating tube is conveniently placed between the gas shell support 14 and the crucible 13; the crucible 13 and the crucible head 21 of the crucible mechanism are respectively located in the cavity and the conical air outlet, and the size of the gas shell, that is, the height of the conical air outlet, is set according to actual needs, so as to adjust the distance from the nozzle of the glass nozzle to the bottom of the gas shell;

[0071] Four layers of high temperature resistant metal mesh 33 are placed on the lateral surface of the step structure. The high temperature resistant metal mesh 33 contacts the outer wall of the crucible 13. Two adjacent layers of high temperature resistant metal mesh 33 are separated by a high temperature resistant metal coil 32 so that the inert gas can pass smoothly and orderly.

[0072] like Figure 7 As shown, the signal generating unit 26 is composed of a signal generator 23 and a power amplifier 24. The signal generator 23 edits a suitable waveform and transmits it to the power amplifier 24. The positive and negative electrodes of the power amplifier 24 are then connected to the positive and negative electrodes of the piezoelectric ceramic stack to drive the power system 25.

[0073] The present invention proposes a ball grid array package solder ball spraying device, in which the solder ball is produced by the water hammer pressure generated by the relative movement of the high-temperature molten metal in the nozzle 27 and the nozzle 27. The device of the present invention provides a waveform signal to the device by the signal generator 23 and the power amplifier 24 to drive the piezoelectric ceramic stack 5 to expand and contract, and the large spring 8 will then contract and expand. Since the upper end of the small spring 9 supports the striker needle cap and then fits tightly with the lower limit plate 7, the striker 10 is then linked to move up and down quickly. The nozzle 27 is connected to the striker 10, and the nozzle 27 will also produce rapid up and down reciprocating motion. The high-temperature liquid solder in the nozzle 27 will generate water hammer pressure and spray out from the spray hole. Due to the protection of the local inert gas, the sprayed high-temperature liquid solder droplets will not have oxidation problems and will present a regular spherical shape. The present invention only needs to set the waveform in the signal generator 23 to customize the action of spraying high-temperature liquid solder droplets. The operation is simple and controllable, and the reliability is very high. The formation rate of the high-temperature liquid solder droplets can be achieved by adjusting the liquid level height, or by adjusting the parameters of the signal generator 23 to change the up and down movement rate of the nozzle. The diameter of the high-temperature liquid solder droplets can be greatly adjusted by replacing the nozzle 27 with different nozzle holes; it can also be fine-tuned by adjusting the parameters of the signal generator 23 to change the water hammer force generated by the up and down movement of the nozzle.

[0074] The invention discloses an application method of a ball grid array package solder ball injection device, which adopts the above-mentioned ball grid array package solder ball injection device for BGA ball planting, and comprises the following steps: a pad with a solder dot is arranged below the device, so that the solder dot is directly opposite to the nozzle of a glass nozzle, and a suitable air shell size is adopted to make the nozzle flush with the bottom of the air shell; an annular high-temperature ceramic heating tube is used to increase the temperature of the liquid solder to 100°C to 200°C higher than the melting point of the solder, and during the high-temperature liquid solder injection process, the liquid level in the nozzle is kept at the same height; a signal generator and a power amplifier are used to drive a power system to continuously inject solder droplets, and the device is made to perform a two-dimensional planar motion according to a set operation trajectory, and finally a neat droplet array is formed on the pad.

[0075] An application method of a ball grid array package solder ball injection device, using the above-mentioned ball grid array package solder ball injection device to prepare solder balls, the steps are: a container for holding solder balls formed by injection is arranged below the device, a suitable air shell size is adopted to make the bottom of the air shell lower than the nozzle of the glass nozzle, an annular high-temperature ceramic heating tube is used to increase the temperature to 100°C to 200°C higher than the melting point of the solder, during the preparation of the solder balls, the liquid level in the nozzle is kept at the same height; after setting the injection frequency and injection strength in the signal generator, continuous injection is performed.

[0076] The invention discloses an application method of a ball grid array package solder ball injection device, which adopts the above-mentioned ball grid array package solder ball injection device for circuit drawing, and comprises the following steps: a plate is arranged below the device, and a suitable air shell size is adopted to make the nozzle flush with the bottom of the air shell; an annular high-temperature ceramic heating tube is used to raise the temperature to 100°C to 200°C higher than the melting point of the solder, and during the high-temperature liquid solder injection process, the liquid level in the nozzle is kept at the same height; the frequency and voltage parameters of the signal generator are adjusted to make the nozzle in a high-frequency and low-amplitude motion state, so that the liquid solder is uniformly and continuously extruded from the injection hole, and at the same time, the device is allowed to perform rapid two-dimensional planar motion according to the program setting, that is, various required two-dimensional circuit patterns are drawn on the plate.

[0077] Embodiment 1: The device of the present invention is used to realize the rapid spraying of high-temperature liquid solder droplets to the solder pads and solder joints for BGA ball planting.

[0078] The devices used are Figure 1 As shown in the figure, the high temperature liquid solder inside the crucible is shown in the figure Fig. 9 As shown. A pad with a solder point is placed under the device so that the solder point is facing the nozzle of the device. Use a gas shell of appropriate size so that the nozzle is flush with the bottom of the gas shell, as shown. Fig.10 As shown, the nozzle maintains a suitable small distance from the pad. Use an annular high-temperature ceramic heating tube to raise the temperature to 80 degrees Celsius, which is higher than the melting point of tin; use a nozzle with a nozzle diameter of 50μm; during the high-temperature liquid solder spraying process, the liquid level in the nozzle is always maintained at the same height. Use a signal generator 23 and a power amplifier 24 to drive the power system 25. In this embodiment, the nozzle performs up and down reciprocating motion, the voltage amplitude is 11.7V, the bias voltage is 20V, and the maximum displacement is less than 10μm. Use a custom operating platform to enable the device to perform planar two-dimensional motion, and then adjust the position of the pad, the operating trajectory of the spraying device, the spraying frequency and droplet interval of the high-temperature liquid solder droplets, and then continuously spray the solder droplets. Finally, a neat array of droplets is formed on the pad, as shown Fig.11 As shown in the figure, the jetting frequency can be adjusted from a few Hz to several hundred Hz, and the BGA ball planting rate is very fast.

[0079] Example 2: Solder balls are prepared using the device of the present invention, wherein the diameter of the nozzle hole of the nozzle is 50 μm;

[0080] The devices used are Figure 1 As shown in the figure, the high temperature liquid solder inside the crucible is shown in the figure Fig. 9As shown, a container for spraying solder balls is placed under the device, and the distance from the bottom of the container to the nozzle is 25 cm; a ring-shaped high-temperature ceramic heating tube is used to raise the temperature to 80 degrees Celsius, which is higher than the melting point of tin; a nozzle with a nozzle diameter of 50 μm is used; during the preparation of the solder balls, the liquid level in the nozzle is kept at the same height. A signal generator 23 and a power amplifier 24 are used to drive the power system 25. In this embodiment, the nozzle performs up and down reciprocating motion, the voltage amplitude is 11.7V, the bias voltage is 20V, and the maximum displacement is less than 10μm. After several hours of uninterrupted spraying, the diameter of the resulting solder ball fluctuates around 40μm, and the floating does not exceed 2μm.

[0081] Example 3: Solder balls are prepared using the device of the present invention, wherein the diameter of the nozzle hole of the nozzle is 80 μm;

[0082] The devices used are Figure 1 As shown in the figure, the high temperature liquid solder inside the crucible is shown in the figure Fig. 9 As shown, a container for spraying solder balls is placed under the device, and the distance from the bottom of the container to the nozzle is 25 cm; a ring-shaped high-temperature ceramic heating tube is used to raise the temperature to 80 degrees Celsius above the melting point of tin; a nozzle with a nozzle diameter of 80 μm is used; during the preparation of the solder balls, the liquid level is always maintained at the same height. A signal generator 23 and a power amplifier 24 are used to drive the power system 25. In this embodiment, the nozzle performs up and down reciprocating motion, the voltage amplitude is 14V, the bias voltage is 20V, and the maximum displacement is less than 10μm. After several hours of uninterrupted spraying, the diameter of the resulting solder ball fluctuates around 72μm, and the floating does not exceed 3μm.

[0083] Embodiment 4: The device of the present invention is used to quickly draw solder lines on a circuit board to generate a circuit with high electrical conductivity.

[0084] The devices used are Figure 1 As shown in the figure, the high temperature liquid solder inside the crucible is shown in the figure Fig. 9 A plate is placed under the device, and a gas shell of appropriate size is used to make the nozzle flush with the bottom of the gas shell, as shown in the figure. Fig.10 As shown, and the nozzle maintains a suitable small distance from the plate. By adjusting the frequency and voltage parameters of the signal generator, the nozzle forms a high-frequency and low-amplitude motion state. At the same time, the device is allowed to perform rapid planar two-dimensional motion. Use an annular high-temperature ceramic heating tube to raise the temperature to 80 degrees Celsius higher than the melting point of tin; use a nozzle with a nozzle hole diameter of 150μm; during the high-temperature liquid solder spraying process, the liquid level in the nozzle is always maintained at the same height. Use a signal generator 23 and a power amplifier 24 to drive the power system 25. In this embodiment, the nozzle performs up and down reciprocating motion, the voltage amplitude is extremely low, and the frequency is 4KHz. A solder line with uniform width is obtained, as shown Fig.12shown.

[0085] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A solder ball injection device for ball grid array packaging, characterized in that: It includes a power system, a heat dissipation support, a crucible mechanism, a heating device, a nozzle, an inert gas supply system and a signal generating unit; The power system is used to drive the nozzle to reciprocate up and down. The power system includes a piezoelectric ceramic stack and a striker, and the striker is fixedly connected to the nozzle. The signal generating unit includes a signal generator and a power amplifier, which are used to drive the piezoelectric ceramic stack to expand and contract, and then drive the nozzle to move up and down quickly through the striker; the crucible mechanism and the heating device are used to heat and melt the solder wire in the crucible; the heat dissipation bracket is used to reduce the heat transferred to the power system; the inert gas supply system is used to place the high-temperature liquid solder droplets sprayed from the nozzle in an inert gas environment to prevent the high-temperature liquid solder droplets from oxidizing; The power system also includes a shell, the top and bottom ends of the shell are respectively provided with an upper threaded through hole and a lower threaded through hole, and the inside of the shell is sequentially provided with a screw micrometer, an upper limit plate, a piezoelectric ceramic stack, a lower limit plate, a spring structure and a striker guide from top to bottom, and the top and bottom ends of the piezoelectric ceramic stack are respectively fixed with an upper top plate and a lower ball head, the upper top plate is semi-cylindrical, and the lower ball head is semi-spherical; the shell, the upper limit plate and the lower limit plate are made of hard materials that are not easily deformed; The screw micrometer is threadedly connected to the upper threaded through hole and then fixed for the second time by a nut; the top surface of the upper limit plate contacts the screw of the screw micrometer, and an arc groove compatible with the upper top plate is opened in the middle of its bottom surface; the top surface of the lower limit plate is opened with a spherical blind hole compatible with the lower ball head; the spring structure is arranged between the lower limit plate and the lower threaded through hole, and comprises a large spring and a small spring sleeved inside the large spring, the bottom end of the large spring is fixedly bonded to the vicinity of the lower threaded through hole by epoxy resin, and is coaxial with the lower threaded through hole; the needle cap of the striker contacts the lower limit plate, the small spring is sleeved on the needle rod of the striker, the striker guide is threadedly connected to the lower threaded through hole, and extends into the inside of the large spring to resist the small spring, and the lower end of the needle rod of the striker extends out of the striker guide; By rotating the rotating handle of the screw micrometer, the screw rod is extended downward, pressing the upper limit plate to move downward, and at the same time, the piezoelectric ceramic stack and the lower limit plate move downward together, and the large spring and the small spring are in a compressed state due to the pressure from the lower limit plate; The heat dissipation bracket is made of a hard material that is not easily deformed, and its shape includes but is not limited to cylindrical and rectangular. In order to accelerate heat dissipation, the side of the heat dissipation bracket is set to have no wall surface, and the top end is provided with a first through hole for the striker to pass through, and the bottom end is provided with a threaded hole and a wire hole; The top of the heat dissipation bracket is fixedly connected to the bottom of the housing of the power system by bolts, and pillars are respectively provided at the four corners of the top of the heat dissipation bracket, so as to reduce the transfer of heat from the heat dissipation bracket to the housing; The crucible mechanism is made of a material that does not react with high-temperature liquid solder, and includes a crucible and a crucible head. The crucible is provided with a liquid storage cavity, a second through hole and a blind hole in a sequential manner from top to bottom, and the crucible head is provided with a third through hole. The liquid storage cavity is used to hold melted high-temperature liquid solder. The diameters of the second through hole and the third through hole are larger than the outer diameter of the nozzle by 0.1-0.2 mm, so that a small gap is formed between the second and third through holes and the nozzle. The blind hole is filled with a high temperature resistant fiber material, the crucible head is threadedly connected to the blind hole, and the second through hole and the third through hole are coaxial; when the crucible head rotates into the blind hole, the upper surface of the crucible head compacts the high temperature resistant fiber material in the blind hole in cooperation with the nozzle; The upper end of the crucible is threadedly connected to the threaded hole of the heat dissipation bracket; The heating device is an annular high-temperature ceramic heating tube, which is sleeved on the outer wall of the crucible, and the positive and negative poles of the heating coil are connected to an external power supply for heating.

2. The solder ball injection device for ball grid array package according to claim 1, characterized in that: The nozzle is a slender tube column structure, the top of the nozzle is fixedly bonded to the bottom of the needle rod of the striker by epoxy resin, and the lower end of the nozzle passes through the liquid storage cavity, the second through hole and the third through hole of the crucible mechanism in sequence, and extends out of the third through hole by less than 2 mm; The nozzle comprises a cylindrical tube made of a material that does not react with high-temperature liquid solder and a glass nozzle, wherein the upper end of the glass nozzle is inserted into the lower end of the cylindrical tube and fixedly bonded to the inner wall of the cylindrical tube by a high-temperature resistant glue; The side wall of the upper half of the cylindrical tube is provided with an air vent and a liquid inlet hole connected to the atmosphere. The liquid inlet hole is immersed in the high-temperature liquid solder in the crucible liquid storage cavity, so that the high-temperature liquid solder flows into the nozzle through the liquid inlet hole, thereby making the liquid level in the nozzle level with the liquid level in the liquid storage cavity.

3. The solder ball injection device for ball grid array package according to claim 2, characterized in that: The inert gas supply system comprises a cylindrical gas shell, an inert gas bottle and a gas metal pipe, wherein a cavity is provided inside the gas shell, and an annular step structure is provided inside the cavity, wherein the vertical surface of the step structure is inclined downward and inward to form a conical gas outlet, and the cavity is communicated with the conical gas outlet; A small hole is opened on the side wall of the gas shell, one end of the gas metal tube is inserted into the small hole, and the other end is connected to the inert gas bottle through a gas hose, and the inert gas enters the cavity from the inert gas bottle through the gas hose and the gas metal tube; An annular gas shell bracket is provided at the upper end of the cavity, the gas shell bracket is fixed to the bottom end of the heat dissipation bracket by bolts, and the outer wall of the gas shell bracket is threadedly connected to the cavity wall; the crucible and the crucible head of the crucible mechanism are respectively located in the cavity and the conical air outlet, and the size of the gas shell is set according to actual needs, so as to adjust the distance from the nozzle of the glass nozzle to the bottom end of the gas shell; Four layers of high temperature resistant metal mesh are placed on the lateral surface of the step structure. The high temperature resistant metal mesh is in contact with the outer wall of the crucible, and two adjacent layers of high temperature resistant metal mesh are separated by a high temperature resistant metal coil.

4. The solder ball injection device for ball grid array package according to claim 3, characterized in that: The signal generating unit is composed of a signal generator and a power amplifier. The signal generator edits a suitable waveform and transmits it to the power amplifier. The positive and negative electrodes of the power amplifier are then connected to the positive and negative electrodes of the piezoelectric ceramic stack to drive the power system.

5. An application method of a ball grid array package solder ball injection device, characterized in that: A ball grid array package solder ball injection device as described in any one of claims 1 to 4 is used for BGA ball planting, and the steps are: a pad with a solder dot is arranged below the device, so that the solder dot is directly opposite to the nozzle of the glass nozzle, and a suitable air shell size is used to make the nozzle flush with the bottom of the air shell; an annular high-temperature ceramic heating tube is used to increase the temperature of the liquid solder to 100°C to 200°C higher than the melting point of the solder, and during the high-temperature liquid solder injection process, the liquid level in the nozzle is always maintained at the same height; a signal generator and a power amplifier are used to drive the power system to continuously inject solder droplets, and the device is made to perform a two-dimensional planar motion according to a set running trajectory, and finally a neat array of droplets is formed on the pad.

6. An application method of a ball grid array package solder ball injection device, characterized in that: A ball grid array package solder ball injection device as described in any one of claims 1 to 4 is used to prepare solder balls, and the steps are: a container for holding solder balls formed by injection is arranged below the device, a suitable gas shell size is adopted to make the bottom of the gas shell lower than the nozzle of the glass nozzle, and an annular high-temperature ceramic heating tube is used to increase the temperature to 100°C to 200°C higher than the melting point of the solder. During the preparation of the solder balls, the liquid level in the nozzle is always maintained at the same height; and continuous injection is performed after the injection frequency and injection strength are set in the signal generator.

7. An application method of a ball grid array package solder ball injection device, characterized in that: A ball grid array package solder ball injection device as described in any one of claims 1 to 4 is used for circuit drawing, and the steps are: a plate is arranged below the device, and a suitable air shell size is used to make the nozzle flush with the bottom of the air shell; an annular high-temperature ceramic heating tube is used to increase the temperature to 100°C to 200°C higher than the melting point of the solder, and during the high-temperature liquid solder injection process, the liquid level in the nozzle is always maintained at the same height; the signal generator frequency and voltage parameters are adjusted to put the nozzle in a high-frequency and low-amplitude motion state, so that the liquid solder is evenly and continuously extruded from the nozzle, and at the same time, the device is allowed to perform rapid planar two-dimensional motion according to the program setting, that is, various required two-dimensional circuit patterns are drawn on the plate.

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