Selective photothermal ball bonding process and apparatus based on plasma surface phosphorus doping

Abstract

The application discloses a selective photothermal ball planting welding process based on plasma surface phosphorus doping, and comprises the following steps: heat insulation treatment is performed on a non-welding area of a welding surface of a substrate to be processed, and a soldering ball is laid on a welding point; copper wires on the back surface of the substrate are connected with a voltage-adjustable device, a vacuum treatment is performed on the environment of the substrate, and the substrate is placed into a photothermal furnace. Compared with the traditional process in which phosphorus is added into solder alloy in the form of an intermediate alloy, phosphorus is doped on the surface of the soldering ball in the form of phosphorus ions, the amount of surface phosphorus doping is adjusted by controlling voltage, the oxidation resistance and wettability of the surface of the soldering ball are improved, the conductive effect of the soldering ball is not affected, the selective photothermal welding of the soldering ball is performed, the warping of the substrate caused by high temperature in the ball planting process is avoided, multiple soldering balls can be simultaneously subjected to photothermal welding, and the efficiency of the welding process is improved by performing surface phosphorus doping in the process of the photothermal ball planting welding.

Description

TECHNICAL FIELD

[0001] The application relates to the chip ball mounting technology field, in particular to a selective light-thermal ball mounting welding process based on plasma surface phosphorus doping and a device thereof. BACKGROUND

[0002] The substrate, also known as an integrated chip carrier, provides electrical interconnection, protection, assembly and the like for a chip. With the rapid development of the electronic industry, the packaging technology between the substrate and the chip is also constantly updated. The BGA (ball grid array) packaging technology has become the mainstream of IC packaging to meet the miniaturization development trend and the demand of high-end chips and market applications. The BGA packaging technology meets the needs of the surface mounting technology and solves the packaging problems of high density, high performance, multi-function and high I / O number applications.

[0003] Since the substrate material contains a large amount of polymer material, the physical properties of these materials vary greatly with the difference in processing technology and heat treatment (reflow soldering, curing, etc.), and the parameters change greatly, which easily causes the substrate and components to warp and thus leads to circuit failure.

[0004] Reflow soldering is a process of using hot gas to heat the flux to complete ball mounting welding. The reason why it is called "reflow soldering" is that the gas circulates in the welding machine to generate high temperature. The heat reflow temperature in the reflow soldering ball mounting process is the main cause of the warping of the substrate and components.

[0005] Laser welding is a process of using a laser beam to directly irradiate the welding site. The welding spot absorbs light energy to convert it into heat energy, which heats the welding site to melt the solder. Compared with traditional reflow soldering, local heating has less impact on the substrate, components and surrounding components, but the laser welding efficiency is low and the cost is high.

[0006] According to literature research and experimental verification, it is found that the addition of a small amount of phosphorus in the solder can improve the oxidation resistance and wettability of the solder. The addition of phosphorus in the solder between 0.005% and 0.020% can effectively improve the oxidation resistance and wettability of the solder. When the mass fraction of phosphorus is 0.020%, the wetting force is increased by 34.79% compared with the solder without phosphorus. When the addition of phosphorus in the solder exceeds 0.020%, the oxidation resistance no longer improves, and too high phosphorus content will affect the mechanical properties of the welding spot.

[0007] The traditional method of doping phosphorus in solder is to add phosphorus in the form of an intermediate alloy to the solder alloy. However, phosphorus can reduce the electrical conductivity of the solder, which affects the performance of the substrate. The prior art fails to solve the problem that the doping of phosphorus in the solder reduces the electrical conductivity of the solder and the warping of the substrate caused by heat reflow. SUMMARY

[0008] The purpose of the present application is to provide a selective light-thermal ball mounting welding process based on plasma surface phosphorus doping and its device to solve the problems raised in the background art.

[0009] The selective light-thermal ball mounting welding process based on plasma surface phosphorus doping comprises the following steps:

[0010] S1, heat insulation treatment is performed on the non-welding area of the substrate welding surface to be processed, and solder balls are laid on the welding points;

[0011] S2, the copper wire on the back surface of the substrate is connected to a device with adjustable voltage, the environment of the substrate is vacuumized, and the substrate is placed in a light-thermal furnace;

[0012] S3, a strong light source is generated by the light-thermal furnace, the strong light source is shunted and directed to each welding point, and the temperature generated by the light on each welding point is monitored, when the temperature reaches the melting point of the solder ball, the light is irradiated on the solder ball, phosphorus ions are prepared at the same time, and a boundary magnetic field is generated on both sides of the solder ball, so that the phosphorus ions move towards the solder ball, the surface of the solder ball is doped with phosphorus during the light-thermal ball mounting welding process, and the number of phosphorus ions adsorbed on the surface of the solder ball is adjusted by adjusting the voltage during welding;

[0013] S4, after the surface phosphorus doping and light-thermal welding are completed, the substrate is removed.

[0014] As a further improvement of the present application, the method for preparing phosphorus ions in step 3 is to inject phosphine gas into the plasma generator.

[0015] As a further improvement of the present application, the boundary magnetic field is generated by energizing the electromagnet, the magnetic field direction is perpendicular to the motion direction of the phosphorus ions, the phosphorus ions enter the magnetic field perpendicularly to the magnetic field boundary, only subjected to the Lorentz force to do uniform circular motion in the magnetic field, and the motion deflection direction range of the phosphorus ions when shooting out of the magnetic field is 0 to 180°, so that the phosphorus ions moving vertically downward move towards the solder ball.

[0016] The present application also discloses a welding device for the selective light-thermal ball mounting welding process based on plasma surface phosphorus doping, which comprises a light-thermal furnace, a light source mechanism for generating strong light is arranged at the upper end of the light-thermal furnace, a ball mounting table is arranged inside the furnace chamber of the light-thermal furnace, a plurality of light directing mechanisms for directional light irradiation and a plasma generator are arranged inside the ball mounting table, and the light source mechanism comprises:

[0017] A halogen lamp is arranged at the upper end inside the light-thermal furnace;

[0018] A first condenser lens is arranged at the lower end of the halogen lamp inside the light-thermal furnace.

[0019] As a further improvement of the present application, the light directing mechanism comprises:

[0020] A light guide pipe is arranged at the top end of the ball mounting platform;

[0021] A second condensing lens is arranged at the top of the light guide pipe;

[0022] A shutter is arranged at the bottom of the light guide pipe, and a temperature sensor is arranged on the shutter;

[0023] A diffuser lens is arranged at the lower end of the shutter;

[0024] A liftable cover barrel is arranged at the bottom of the light guide pipe.

[0025] As a further improvement of the application, the plasma generator comprises a ventilation chamber and a high-pressure chamber arranged from top to bottom.

[0026] As a further improvement of the application, the bottom of the ball mounting platform is provided with a heat dissipation base, the upper end of the heat dissipation base is provided with a workpiece, and one side of the workpiece is connected with a voltage adjusting assembly for adjusting voltage.

[0027] As a further improvement of the application, the upper end surface of the workpiece is paved with a substrate, the upper end of the substrate is provided with a heat insulation plate and a solder ball, two electromagnets are arranged on the upper end of the heat insulation plate between the solder balls, and the magnetic poles of the two electromagnets adjacent to each other are opposite.

[0028] As a further improvement of the application, the voltage adjusting assembly comprises a capacitor, a resistor and a power switch, the capacitor is connected with the workpiece, and the capacitor is connected with the resistor and the power switch.

[0029] As a further improvement of the application, the two electromagnets are located below the plasma generator.

[0030] Compared with the prior art, the application has the following advantages:

[0031] In the process of photo-thermal ball mounting welding, phosphorus ions are generated in the application, and a magnetic field is generated by the electromagnets, so that the motion direction of the phosphorus ions moving vertically downward is deflected, and the phosphorus ions move towards the surface of the solder ball. The voltage of the workpiece is adjusted by the capacitor, so as to control the amount of phosphorus doped on the surface of the solder ball. Compared with the traditional process in which phosphorus elements are added to the solder alloy in the form of intermediate alloy, phosphorus is doped on the surface of the solder ball in the form of phosphorus ions, and the amount of surface phosphorus doping is controllable. Not only the oxidation resistance and wettability of the solder ball surface are improved, but also the conductivity of the solder ball is not affected. Moreover, the surface doping is carried out in the process of photo-thermal ball mounting welding, which improves the efficiency of the welding process.

[0032] The light guide tube realizes selective light heat welding of the soldering ball, avoids the problem that the substrate is warped due to high temperature in the ball mounting process, can simultaneously perform light heat welding on multiple soldering balls by providing a heat source through a halogen lamp, is more efficient than traditional laser welding, and realizes control on the preheating temperature of the ball mounting through the combination of the temperature sensor and the shutter. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The process flowchart of the present application is shown in the figure.

[0034] Figure 2 The schematic diagram of the overall structure of the device of the present application is shown in the figure.

[0035] Figure 3 The working flowchart of the device of the present application is shown in the figure.

[0036] Figure 4 The schematic diagram of the heat insulation plate of the present application is shown in the figure.

[0037] Figure 5 The schematic diagram of the soldering point of the substrate of the present application is shown in the figure.

[0038] In the figure: 1, light heat furnace; 2, light source mechanism; 21, halogen lamp; 22, first condenser lens; 3, ball mounting table; 31, heat dissipation base; 32, workpiece; 4, light guide mechanism; 41, light guide tube; 42, second condenser lens; 43, shutter; 44, temperature sensor; 45, diffuser lens; 46, liftable cover barrel; 5, plasma generator; 51, air chamber; 52, high pressure chamber; 6, substrate; 7, heat insulation plate; 8, soldering ball; 9, two electromagnets; 10, capacitor; 11, resistor; 12, power switch. EMBODIMENT

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. EMBODIMENT

[0040] Please refer to Figure 1 The present application provides the following technical solutions: a selective light heat ball mounting welding process based on plasma surface phosphorus doping, which comprises the following steps:

[0041] S1, performing heat insulation treatment on the non-welding area of the welding surface of the substrate to be processed, and laying soldering balls on the welding points;

[0042] S2, connecting the copper wire on the back surface of the substrate to a device with adjustable voltage, performing vacuum treatment on the environment of the substrate, and placing the substrate into a light heat furnace.

[0043] S3, generating a strong light source by the light-thermal furnace, splitting and directing the strong light source to each welding point, and monitoring the temperature generated by the light on each welding point, when the temperature reaches the melting point of the solder ball, irradiating the light on the solder ball, preparing phosphorus ions at the same time, and generating a boundary magnetic field on both sides of the solder ball, so that the phosphorus ions move to the solder ball, doping phosphorus on the surface of the solder ball in the process of light-thermal ball bonding, and adjusting the voltage during welding to further adjust the number of phosphorus ions adsorbed on the surface of the solder ball;

[0044] S4, after completing the surface doping of phosphorus and the light-thermal welding, the substrate is removed.

[0045] The method for preparing phosphorus ions in step S3 is to inject phosphine gas into the plasma generator.

[0046] The boundary magnetic field in step S3 is generated by energizing the electromagnet, the magnetic field direction is perpendicular to the motion direction of the phosphorus ions, the phosphorus ions enter the magnetic field perpendicular to the magnetic field boundary, only subjected to the Lorentz force to do uniform circular motion in the magnetic field, and the motion deflection direction range of the phosphorus ions when shooting out of the magnetic field is 0 to 180°, so that the phosphorus ions moving vertically downward move to the direction of the solder ball. Embodiment

[0047] Please refer to Figures 2-5 The application also provides the following technical scheme: a welding device based on the selective light-thermal ball bonding process of plasma surface doping of phosphorus, comprising a light-thermal furnace 1, a light source mechanism 2 for generating a strong light is installed at the upper end of the light-thermal furnace 1, a ball mounting table 3 is placed in the furnace chamber of the light-thermal furnace 1, a plurality of light directing mechanisms 4 for directional light irradiation and a plasma generator 5 are installed in the ball mounting table 3, the light source mechanism 2 comprises a halogen lamp 21 and a first condenser lens 22, the halogen lamp 21 is installed at the upper end inside the light-thermal furnace 1, the first condenser lens 22 is installed at the lower end of the halogen lamp 21 inside the light-thermal furnace 1, the halogen lamp 21 and the first condenser lens 22 can be adjusted in position, and the first condenser lens 22 can vertically hit the light of the halogen lamp 21 into the cavity of the light-thermal furnace 1.

[0048] The light guiding mechanism 4 comprises light guiding tubes 41, second focusing lenses 42, shutters 43, diffusing lenses 45 and liftable cover barrels 46, the light guiding tubes 41 are fixedly installed at the top of the ball mounting table 3, the light guiding tubes 41 are equidistantly distributed, the second focusing lenses 42 are fixedly installed at the top of the light guiding tubes 41, the shutters 43 are installed at the bottom of the light guiding tubes 41, the minimum opening temperature of the shutter 43 is the melting point of the soldering balls 8, the shutter 43 is closed after reaching the program setting time, the temperature sensor 44 is installed on the shutter 43, the diffusing lenses 45 are installed at the lower end of the shutter 43, the liftable cover barrels 46 are installed at the bottom of the light guiding tubes 41, the second focusing lenses 42 can focus the light vertically entering the cavity of the light heat furnace 1 on the lower part of the light guiding tubes 41, and the light is diffused and irradiated on the surface of the soldering balls 8 through the diffusing lenses 45, the radius of the light guiding tubes 41 located at the two sides of the ball mounting table 3 is greater than that of the light guiding tubes 41 located at the middle part, so that the heat conduction of each light guiding tube 41 is uniform.

[0049] The plasma generator 5 comprises a ventilation chamber 51 and a high-pressure chamber 52, and the ventilation chamber 51 and the high-pressure chamber 52 are distributed from top to bottom.

[0050] The bottom of the ball mounting table 3 is provided with a heat dissipation base 31, the upper end of the heat dissipation base 31 is provided with a workpiece 32, and one side of the workpiece 32 is connected with a voltage adjusting assembly for adjusting voltage.

[0051] The upper end surface of the workpiece 32 is paved with a substrate 6, the upper end of the substrate 6 is provided with a heat insulation plate 7 and soldering balls 8, two electromagnets 9 are installed on the heat insulation plate 7 between the soldering balls 8, and the magnetic poles of the two adjacent sides of the electromagnets 9 are opposite.

[0052] The voltage adjusting assembly comprises a capacitor 10, a resistor 11 and a power switch 12, the capacitor 10 is connected with the workpiece 32, the surface of the workpiece 32 is provided with a plurality of metal contacts, which can be communicated with copper wires on the back of the substrate 6 and are connected with the capacitor 10, and the capacitor 10 is connected with the resistor 11 and the power switch 12.

[0053] The two electromagnets 9 are located below the plasma generator 5.

[0054] When the device works, the workpiece 32 is placed on the heat dissipation base 31 at the bottom of the ball mounting table 3, the heat insulation plate 7 is covered on the substrate 6, the holes of the heat insulation plate 7 are corresponded with the soldering points of the substrate 6, then the soldering balls 8 are paved (such as Figure 4 、 5As shown in the figure, the substrate 6 is placed on the workpiece 32, the solder balls 8 on the substrate 6 are aligned with the light guide tube 41, the liftable cover barrel 46 is ensured to cover the solder balls 8, the phosphine gas is introduced into the air chamber 51 in the plasma generator 5, the ball mount table 3 which is being vacuumized is placed in the cavity of the photothermal furnace 1, the photothermal furnace 1 and the plasma generator 5 are turned on, the halogen lamp 21 at the top of the photothermal furnace 1 vertically emits light into the cavity of the photothermal furnace 1 through the first condenser lens 22, the light guide tube 41 further focuses the light at the lower part of the light guide tube 41 through the second condenser lens 42, the shutter 43 is in the closed state when the temperature sensor 44 detects that the temperature has not reached the melting point of the solder balls 8, the shutter 43 is opened when the temperature sensor 44 detects that the temperature has reached the melting point of the solder balls 8, the focused light is uniformly irradiated on the surface of the solder balls 8 through the diffuser lens 45, the shutter 43 is closed after reaching the program set opening time, the phosphine gas in the high-pressure chamber 52 of the plasma generator 5 obtains phosphorus ions in the plasma state through high-voltage, and moves downward under the pushing of the carrier gas, the shutter 43 is opened after the temperature of the temperature sensor 44 reaches the melting point of the solder balls 8, and the liftable cover barrel 46 at the bottom of the light guide tube 41 and the two electromagnets 9 are electrified at the same time, the two electromagnets 9 form a bounded magnetic field after being electrified, the direction of the magnetic field is perpendicular to the direction of the phosphorus ion movement, the phosphorus ion enters the magnetic field perpendicularly to the boundary of the magnetic field, and only the Lorentz force makes the phosphorus ion do uniform circular motion in the magnetic field, the phosphorus ion deviates the direction of movement by 0 to 180° when it shoots out of the magnetic field, so that the phosphorus ion moving vertically downward moves toward the solder balls 8, the solder balls 8 are heated in the ball mount table 3 and start to melt from the top, flow to the bottom and are welded with the substrate 6, the lifting of the liftable cover barrel 46 is lifted at the same time of welding, the solder balls 8 are exposed to the phosphorus ion environment from the bottom, the phosphorus ion is uniformly attached to the surface of the solder balls 8 from the bottom to the top of the solder balls 8, the voltage of the workpiece 32 is adjusted by adjusting the capacitor 10, and then the amount of phosphorus ions absorbed by the solder balls 8 is adjusted, the phosphorus is doped at the same time, the light heat of the halogen lamp 21 is gathered by the light guide tube 41 to perform light heat welding on the solder balls 8, the surface doping of phosphorus and the light heat welding are completed, and the substrate 6 is removed from the device.

[0055] It should be noted that, in this document, the terms such as first and second are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between such entities or operations. Also, the terms "comprises", "comprising", or any other variations thereof are intended to cover non-exclusive inclusions, so that a process, method, article, or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or inherent to such a process, method, article, or device.

[0056] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A selective photothermal ball bonding process based on plasma surface phosphorus doping, characterized in that, The welding process comprises the following steps: S1, heat insulation treatment is performed on the non-welding area of the welding surface of the substrate to be processed, and solder balls are laid on the welding points; S2, the copper wire on the back surface of the substrate is connected to the voltage-adjustable device, the environment of the substrate is vacuumized, and the substrate is placed in the light-heat furnace; S3, a strong light source is generated by the light-heat furnace, the strong light source is shunted and directed to each welding point, and the temperature generated by the light on each welding point is monitored, when the temperature reaches the melting point of the solder ball, the light is irradiated on the solder ball, phosphorus ions are prepared at the same time, and a boundary magnetic field is generated on both sides of the solder ball, so that the phosphorus ions move to the solder ball, the surface of the solder ball is doped with phosphorus in the process of light-heat ball bonding, and the number of phosphorus ions adsorbed on the surface of the solder ball is adjusted by adjusting the voltage during welding; S4, after the surface doping and light-heat welding are completed, the substrate is removed.

2. The selective photothermal ball bonding process based on plasma surface phosphorous doping according to claim 1, characterized in that: The method for preparing phosphorus ions in step S3 is to inject phosphine gas into the plasma generator.

3. The selective photothermal ball bonding process based on plasma surface phosphorous doping according to claim 1, wherein: The boundary magnetic field is generated by energizing the electromagnet, the magnetic field direction is perpendicular to the motion direction of the phosphorus ions, the phosphorus ions enter the magnetic field perpendicularly to the magnetic field boundary, only the Lorentz force is in the magnetic field, and the phosphorus ions make uniform circular motion, the motion deflection direction range of the phosphorus ions when shooting out of the magnetic field is 0 to 180°, so that the phosphorus ions moving vertically downward move to the direction of the solder ball.

4. A selective photothermal ball planting device based on plasma surface phosphorus doping, characterized by: The selective light-heat ball bonding process based on plasma surface doping of phosphorus according to any one of claims 1-3 is realized, and the device comprises a light-heat furnace (1), characterized in that: the upper end of the light-heat furnace (1) is provided with a light source mechanism (2) for generating a strong light, the inside of the furnace chamber of the light-heat furnace (1) is provided with a ball planting table (3), the inside of the ball planting table (3) is provided with a plurality of light guiding mechanisms (4) for directional light irradiation and a plasma generator (5), and the light source mechanism (2) comprises: a halogen lamp (21) arranged at the upper end inside the light-heat furnace (1); a first condenser lens (22) arranged at the lower end of the halogen lamp (21) inside the light-heat furnace (1); the bottom of the ball planting table (3) is provided with a heat dissipation base (31), the upper end of the heat dissipation base (31) is provided with a workpiece (32), one side of the workpiece (32) is connected with a voltage adjusting assembly for adjusting the voltage, the upper end surface of the workpiece (32) is paved with a substrate (6), the upper end of the substrate (6) is provided with a heat insulation plate (7) and solder balls (8), two electromagnets (9) are arranged on the heat insulation plate (7) between the solder balls (8), and the magnetic poles of the two adjacent sides of the electromagnets (9) are opposite.

5. The selective photothermal ball planting device based on plasma surface phosphorus doping according to claim 4, characterized in that: The light guiding mechanism (4) comprises: a light guide pipe (41) arranged at the top end of the ball planting table (3); a second condenser lens (42) arranged at the top of the light guide pipe (41); a shutter (43) arranged at the bottom of the light guide pipe (41), wherein a temperature sensor (44) is arranged on the shutter (43); a diffuser lens (45) arranged at the lower end of the shutter (43); The liftable cover barrel (46) is arranged at the bottom of the light guide pipe (41).

6. The selective photothermal ball prepositioning device based on plasma surface phosphorous doping of claim 5, wherein: The plasma generator (5) comprises an air chamber (51) and a high-pressure chamber (52) arranged from top to bottom.

7. The selective photothermal ball planting device based on plasma surface phosphorus doping according to claim 6, characterized in that: The voltage adjusting assembly comprises a capacitor (10), a resistor (11) and a power switch (12), the capacitor (10) is connected with the workpiece (32), and the capacitor (10) is connected with the resistor (11) and the power switch (12).

8. The selective photothermal ball prepositioning device based on plasma surface phosphorous doping of claim 7, wherein: Two said electromagnets (9) are located below the plasma generator (5).

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