A novel tin-based particle composite solder and a method for preparing a packaged solder joint

Abstract

The application discloses a novel tin-based particle composite solder and a packaging solder point preparation method. The method comprises the following steps: taking pure copper as upper and lower substrates, grinding, polishing and drying the substrates to remove oxides and oil stains; after processing, detecting the flatness of the substrates by a detecting device; adding micron Zn particles, nano Cu particles and an appropriate amount of flux 13wt.% into micron Sn particles, fully mixing and stirring to obtain Sn-9Zn-30Cu particle composite solder; uniformly coating the obtained Sn-9Zn-30Cu particle composite solder on the lower copper plate by using a mold, then placing the upper copper substrate on the lower copper plate to form a sandwich structure, and preparing a solder point by using a wafer bonder. According to the comparative example, when the set bonding parameters are temperature 280 DEG C, time 60 min and pressure 1Mpa, the shear strength of the Cu / Sn-9Zn-30Cu / Cu solder point is as high as 17.24Mpa, which meets the requirements of most application occasions. Meanwhile, the tin-based solder point organization is composed of Cu3Sn phase, (Cu, Zn)6Sn5 phase, Cu6(Sn, Zn)5 phase, Cu particles and Zn-rich phase, and can be applied for a long time under the action of a thermal field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of brazing materials, in particular to a novel tin-based particle composite filler metal and a packaging solder joint preparation method. BACKGROUND

[0002] With the development of electronic packaging technology, electronic components are developing towards miniaturization and light weight. Under this situation, 3D packaging technology which can make full use of the three-dimensional space is used for chip stacking, which can realize high integration of electronic products and improve the reliability of solder joints. 3D packaged chips often need to withstand high operating temperatures, and require the chip to operate stably in a high temperature environment. Therefore, the reliability of the solder joint under the action of heat is very important, but the traditional solder joint cannot meet the requirements of high temperature service.

[0003] Sn-Zn eutectic filler metal is expected to replace Sn-Pb filler metal because of its low melting point (198℃), which is close to that of Sn-Pb eutectic filler metal (183℃). In addition, Sn-Zn filler metal has good ductility, mechanical properties, electrical properties and minimum intermetallic compound (IMC) formation.

[0004] However, Sn-Zn filler metal has poor oxidation resistance and poor corrosion resistance, and the solder joint is composed of alpha-Sn and beta-Zn, which cannot meet the requirements of high temperature service. Researchers have found that the addition of Cu element in In-Ag, In-Sn, Sn-Ag and Sn-Bi filler metals can improve the high temperature service performance of the solder joint. At present, many studies focus on exploring new micro solder joint connection technology, among which TLP connection technology has been identified as a potential candidate. Low temperature transient liquid phase (TLP) connection technology can realize low temperature bonding and high temperature service of the solder joint through the melting, diffusion and reaction of low melting point particles in the micro-nano mixed particles with high melting point particles. Nano-Cu particles have high melting point, high strength and high temperature resistance, and can form high melting point IMC with Sn-based filler metal. However, there is no report on the influence of bonding process parameters on the reliability of Cu / Sn-9Zn-30Cu / Cu solder joint during TLP bonding process. The present application aims to add nano-Cu particles to Sn-9Zn particle composite filler metal, optimize the bonding temperature and bonding time, control the phase composition of the solder joint, and improve the reliability of the solder joint to meet the requirements of high temperature service.

[0005] Therefore, in view of the above technical problems, it is necessary to provide a novel tin-based particle composite filler metal and a packaging solder joint preparation method. SUMMARY

[0006] The present application aims to provide a novel tin-based particle composite filler metal and a packaging solder joint preparation method to solve the above problems.

[0007] To achieve the above objectives, an embodiment of the present invention provides the following technical solution:

[0008] A novel tin-based particle composite solder, the chemical composition and component ratio of which are as follows:

[0009] Micron-sized Sn particles: 63.7%;

[0010] Micron-sized Zn particles: 6.3%;

[0011] Nano-Cu particles: 30%.

[0012] A novel method for preparing solder joints for tin-based particle composite solder packaging includes the following steps:

[0013] S1: Pure copper is used as the upper and lower substrates. The substrates are ground, polished and dried to remove oxides and oil.

[0014] S2: After processing, the flatness of the substrate is tested using a testing device;

[0015] S3: Micron-sized Zn particles and nano-sized Cu particles are added to micron-sized Sn particles, and an appropriate amount of flux (13 wt.%) is added. The mixture is thoroughly stirred to obtain Sn-9Zn-30Cu particle composite solder.

[0016] S4: The obtained Sn-9Zn-30Cu particle composite solder is uniformly coated onto the lower copper plate using a mold, and then the upper copper substrate is placed on it to form a sandwich structure.

[0017] S5: The solder joints are prepared using a wafer bonding machine.

[0018] As a further improvement of the present invention, the temperature for drying the substrate in S1 is controlled at 25°C to 50°C.

[0019] As a further improvement of the present invention, the detection device includes a detection platform, a base plate is provided on the top of the detection platform, and an L-shaped plate is fixedly connected to the top of the detection platform. A moving groove is opened on the L-shaped plate, and a servo motor is fixedly connected to one end of the L-shaped plate. A reciprocating lead screw is fixedly connected to the output end of the servo motor and located in the moving groove. A screw sleeve is provided around the reciprocating lead screw.

[0020] As a further improvement of the application, the first electric push rod is fixedly connected to the bottom end of the sleeve, the output end of the first electric push rod is fixedly connected to a detection box, a second electric push rod is installed on the inner wall of the detection box, an electromagnet is installed on the output end of the second electric push rod, a plurality of lightweight detection rods are evenly distributed in the detection box, a magnetic block is fixedly connected to the top end of each lightweight detection rod, and a laser instrument and a light beam receiving terminal are respectively installed on the two ends of the inner wall of the detection box, and the number of the laser instrument and the light beam receiving terminal matches the number of the lightweight detection rods.

[0021] As a further improvement of the application, a through hole is formed in the lightweight detection rod, a first colored glass and a second colored glass are respectively installed on the upper and lower sides of the through hole of the lightweight detection rod, and a marking nozzle is installed at the bottom end of the lightweight detection rod.

[0022] As a further improvement of the application, the particle size of the micron Sn and micron Zn particles in S3 is 1-5 mu m, and the particle size of the nano Cu particles is 40-50 nm.

[0023] As a further improvement of the application, the particle ratio of the micron Sn, micron Zn and nano Cu particles is 63.7:6.3:30.

[0024] As a further improvement of the application, the TWB-100 wafer bonding machine is used to prepare the solder joint in S4, and the bonding parameters are as follows: the temperature is 260-340 DEG C, the bonding time is 15-120 min, and the bonding pressure is 1 MPa.

[0025] As a further improvement of the application, the bonding temperature is 280 DEG C, and the bonding time is 60 min.

[0026] Compared with the prior art, the application has the following advantages:

[0027] When the bonding parameters are set as temperature 280 DEG C, time 60 min and pressure 1 Mpa, the shear strength of the Cu / Sn-9Zn-30Cu / Cu solder joint is as high as 17.24 Mpa, which meets the requirements of most application occasions, and the tin-based solder joint is composed of Cu3Sn phase, (Cu,Zn)6Sn5 phase, Cu6(Sn,Zn)5 phase, Cu particles and Zn-rich phase, which can be used for a long time under the action of heat field, the wafer bonding machine is easy to operate, and complex operation and training are not required, thereby reducing labor cost. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The flowchart of the preparation method of the novel tin-based particle composite solder joint of the application is shown in the figure.

[0029] Figure 2Front view of the detection platform of the present application;

[0030] Figure 3 Cu / Sn-9Zn-30Cu / Cu solder joint of the present application Figure 2 Structure of the present application at A;

[0031] Figure 4 Microstructure of Cu / Sn-9Zn-30Cu / Cu solder joint (a) at 260℃ bonding temperature of the present application;

[0032] Figure 5 Microstructure of Cu / Sn-9Zn-30Cu / Cu solder joint (b) at 280℃ bonding temperature of the present application;

[0033] Figure 6 Microstructure of Cu / Sn-9Zn-30Cu / Cu solder joint (c) at 300℃ bonding temperature of the present application;

[0034] Figure 7 Microstructure of Cu / Sn-9Zn-30Cu / Cu solder joint (d) at 320℃ bonding temperature of the present application;

[0035] Figure 8 Microstructure of Cu / Sn-9Zn-30Cu / Cu solder joint (e) at 340℃ bonding temperature of the present application;

[0036] Figure 9 Effect of bonding temperature on shear strength of the present application;

[0037] Figure 10 Microstructure of Cu / Sn-9Zn-30Cu / Cu solder joint (a) at 15min bonding time of the present application;

[0038] Figure 11 Microstructure of Cu / Sn-9Zn-30Cu / Cu solder joint (b) at 30min bonding time of the present application;

[0039] Figure 12 Microstructure of Cu / Sn-9Zn-30Cu / Cu solder joint (c) at 60min bonding time of the present application;

[0040] Figure 13 Microstructure of Cu / Sn-9Zn-30Cu / Cu solder joint (d) at 90min bonding time of the present application;

[0041] Figure 14 Microstructure of Cu / Sn-9Zn-30Cu / Cu solder joint (e) at 120min bonding time of the present application;

[0042] Figure 15 A diagram showing the effect of bonding time on shear strength of the present application.

[0043] Explanation of reference numerals in the drawings:

[0044] 1, detection platform; 2, L-shaped plate; 11, base plate; 12, moving groove; 13, servo motor; 14, reciprocating screw rod; 15, screw sleeve; 16, first electric push rod; 17, detection box; 18, second electric push rod; 19, electromagnet; 20, light detection rod; 21, magnetic block; 22, laser instrument; 23, light beam receiving terminal; 24, first colored glass; 25, through hole; 26, second colored glass; 27, marking nozzle. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some 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 work fall within the scope of the present application.

[0046] Embodiment:

[0047] Please refer to Figure 1 A new tin-based particle composite filler, the chemical composition and composition ratio of which are as follows:

[0048] Micron Sn particles: 63.7%;

[0049] Micron Zn particles: 6.3%;

[0050] Nanometer Cu particles: 30%.

[0051] A new tin-based particle composite filler packaging solder joint preparation method, comprising the following steps:

[0052] S1: using pure copper as the upper and lower substrates, polishing and drying the substrates to remove oxides and oil stains;

[0053] S2: after processing, detecting the flatness of the substrates by a detection device;

[0054] S3: adding micron Zn particles and nanometer Cu particles to the micron Sn particles, and adding an appropriate amount of flux 13 wt.%, and fully mixing and stirring to obtain Sn-9Zn-30Cu particle composite filler;

[0055] S4: using a mold to uniformly coat the obtained Sn-9Zn-30Cu particle composite filler on the lower copper plate, and then placing the upper copper substrate on it to form a sandwich structure;

[0056] S5: Using a wafer bonder to prepare the solder joint.

[0057] The temperature of the substrate blowing dry in S1 is controlled at 25-50°C.

[0058] Please refer to Figures 2-3 The detection device comprises a detection table 1, a substrate 11 is arranged at the top end of the detection table 1, and an L-shaped plate 2 is fixedly connected to the top end of the detection table 1, a moving groove 12 is formed in the L-shaped plate 2, and a servo motor 13 is fixedly connected to one end of the L-shaped plate 2, a reciprocating screw rod 14 is fixedly connected to the output end of the servo motor 13 and located in the moving groove 12, a screw sleeve 15 is sleeved outside the reciprocating screw rod 14, a first electric push rod 16 is fixedly connected to the bottom end of the screw sleeve 15, a detection box 17 is fixedly connected to the output end of the first electric push rod 16, a second electric push rod 18 is mounted on the inner wall of the detection box 17, an electromagnet 19 is mounted on the output end of the second electric push rod 18, a plurality of light detection rods 20 are evenly arranged in the detection box 17, a magnetic block 21 is fixedly connected to the top end of each light detection rod 20, a laser instrument 22 and a light beam receiving terminal 23 are respectively mounted on the two ends of the inner wall of the detection box 17, the number of the laser instrument 22 and the light beam receiving terminal 23 matches the number of the light detection rods 20, a through hole 25 is formed in each light detection rod 20, a first colored glass 24 and a second colored glass 26 are respectively mounted on the upper and lower sides of the through hole 25 of each light detection rod 20, and a marking nozzle 27 is mounted at the bottom end of each light detection rod 20.

[0059] When the flatness of the substrate 11 after grinding and polishing is detected, the switch of the electromagnet 19 is started to generate a certain attractive force on the plurality of magnetic blocks 21, so as to adjust the height of the plurality of light detection rods 20, so that the laser light source emitted by the laser instrument 23 can be captured by the light beam receiving terminal 23 through the through hole 25, then the power switch of the first electric push rod 16 is started, so that the first electric push rod 16 drives the detection box 17 to move downward, so that the lower end of the plurality of light detection rods 20 abuts against the outer end of the substrate 11, so as to disconnect the power switch of the electromagnet 19, and the second electric push rod 18 drives the electromagnet 19 to move to the limit away from the plurality of light detection rods 20.

[0060] Then, the power switch of the servo motor 13 is started, so that the servo motor 13 is started to drive the reciprocating screw rod 14 to rotate and drive the screw sleeve 15 to move, and the detection box 17 and the plurality of lightweight detection rods 20 are rolled on the outer surface of the base plate 11 through the movement of the screw sleeve 15. When the lightweight detection rod 20 moves to the uneven area of the outer surface of the base plate 11, the lightweight detection rod 20 has a certain upward or downward deviation. When the uneven area is a depression, the lightweight detection rod 20 has a certain downward movement, and the laser emitted by the laser instrument 23 is received by the light beam receiving terminal 23 through the first colored glass 24, so that the marking nozzle 27 installed at the lower end of the lightweight detection rod 20 can mark the area. When the uneven area is a protrusion, the lightweight detection rod 20 has a certain upward movement, and the laser emitted by the laser instrument 23 is received by the light beam receiving terminal 23 through the first colored glass 24. Because the color of the light emitted by the laser instrument 23 is different when it is received by the light beam receiving terminal 23 through the first colored glass 24 and the second colored glass 26, it is used to distinguish whether the area is a depression or a protrusion, so that different colored marking liquid can be used for marking when marking the area subsequently, and it is convenient for subsequent remedial measures for the depression or protrusion area.

[0061] Please refer to Figures 4-15 , the particle size of the micron Sn and micron Zn particles in S3 is 1-5 μm, the particle size of the nano Cu particles is 40-50 nm, and the particle ratio of the micron Sn, micron Zn and nano Cu particles is 63.7:6.3:30. In S4, the TWB-100 wafer bonding machine is used to prepare the solder joint, and the bonding parameters are as follows: temperature 260-340℃, bonding time 15-120min, and bonding pressure 1MPa. In S4, the bonding temperature is 280℃, and the bonding time is 60min.

[0062] The required raw materials and equipment include: Sn particles and Zn particles with a particle size of 1-5 μm, Cu particles with a particle size of 40-50 nm, Flux55 flux, copper blocks, TWB-100 wafer bonding machine, German Zeiss Supra55 type scanning electron microscope, X-act INCA150 type energy spectrometer, and UTM5305 type electronic universal testing machine.

[0063] Sn and Zn particles and Cu particles were mixed in a mass percentage of 63.7:6.3:30 and mechanically stirred for 120 min to prepare Sn-9Zn-30Cu mixed particles. 13 wt.% rosin flux was mixed with the Sn-9Zn-30Cu mixed particles by mechanical stirring for 120 min to prepare Sn9-Zn-30Cu particle composite solder. The particle composite solder was uniformly coated on a lower copper substrate (12 mm x 12 mm x 4 mm), and an upper copper substrate (10 mm x 10 mm x 4 mm) was covered on the coated solder layer to perform TLP bonding. The Cu / Sn-9Zn-30Cu / Cu solder joint was prepared using a TWB-100 wafer bonder, the bonding temperature was 260, 280, 300, 320, 340°C. The bonding time was 15, 30, 60, 90, 120 min, the bonding pressure was 1 MPa, and the vacuum degree was 1-5 Pa.

[0064] The microstructure and shear fracture morphology of the particle composite solder joint were studied by scanning electron microscopy (SEM) using a Zeiss Supra55. The shear strength of the particle composite solder joint was measured using a UTMS5305 electronic universal testing machine, 4 solder joints were prepared for each bonding parameter for shear testing, and the average result was taken, the loading rate was 0.02 mm / min.

[0065] As can be seen from the comparative examples, when the bonding parameters are set to a temperature of 280°C, a time of 60 min, and a pressure of 1 MPa, the shear strength of the Cu / Sn-9Zn-30Cu / Cu solder joint is as high as 17.24 MPa, which meets most application scenarios.

[0066] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, and it is intended to encompass all variations falling within the meaning and scope of the equivalent elements of the claims. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0067] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description manner of the specification is only for the sake of clarity, those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be properly combined to form other implementation manners that those skilled in the art can understand.

Claims

1. A method for preparing a solder joint of a Sn-based particle composite solder encapsulation, characterized by: The tin-based particle composite solder chemical composition and component ratio are: Micron Sn particles: 63.7%; Micron Zn particles: 6.3%; Nanometer Cu particles: 30%; Comprising the following steps: S1: using pure copper as the upper and lower substrates, polishing, drying and removing oxides and oil stains; S2: after processing, detecting the flatness of the substrate by a detection device; S3: adding micron Zn particles and nanometer Cu particles to micron Sn particles, and adding an appropriate amount of flux 13wt.% to fully mix and stir to obtain Sn-9Zn-30Cu particle composite solder; S4: uniformly coating the obtained Sn-9Zn-30Cu particle composite solder on the lower copper plate by using a mold, and then placing the upper copper substrate on it to form a sandwich structure; S5: preparing a welding spot by using a wafer bonding machine; The temperature for drying the substrate in S1 is controlled at 25-50°C. The detection device comprises a detection table (1), a substrate (11) is arranged at the top end of the detection table (1), and an L-shaped plate (2) is fixedly connected to the top end of the detection table (1), a moving groove (12) is formed in the L-shaped plate (2), and a servo motor (13) is fixedly connected to one end of the L-shaped plate (2), a reciprocating screw rod (14) is fixedly connected to the output end of the servo motor (13) and located in the moving groove (12); A screw sleeve (15) is sleeved outside the reciprocating screw rod (14), a first electric push rod (16) is fixedly connected to the bottom end of the screw sleeve (15), a detection box (17) is fixedly connected to the output end of the first electric push rod (16), a second electric push rod (18) is mounted on the inner wall of the detection box (17), an electromagnet (19) is mounted on the output end of the second electric push rod (18), a plurality of light detection rods (20) are evenly arranged in the detection box (17), a magnetic block (21) is fixedly connected to the top end of each light detection rod (20), a laser instrument (22) and a light beam receiving terminal (23) are respectively mounted on the inner wall of the detection box (17) at both ends, and the number of the laser instrument (22) and the light beam receiving terminal (23) matches the number of the light detection rods (20); A through hole (25) is formed in the light detection rod (20), a first colored glass (24) and a second colored glass (26) are respectively mounted on the light detection rod (20) and located on the upper and lower sides of the through hole (25), and a marking nozzle (27) is mounted on the bottom end of the light detection rod (20). In S3, the particle size of the micron Sn and micron Zn particles is 1-5μm, and the particle size of the nanometer Cu particles is 40-50nm.

2. The method of claim 1, wherein the method comprises: In S4, the wafer bonding machine used for preparing the welding spot is TWB-100, and the bonding parameters are as follows: temperature 260-340℃, bonding time 15-120min, and bonding pressure 1MPa.

3. The method of claim 1, wherein the solder paste is prepared by the steps of: (a) mixing the tin-based solder powder with the flux; (b) heating the mixture to a temperature of 100- 150°C for 1-3 hours; (c) cooling the mixture to room temperature; and (d) screening the mixture on a screen printer. In S4, the bonding temperature is 280℃, and the bonding time is 60min.

4. The method of claim 1, wherein the solder paste is prepared by the steps of: (a) mixing the tin-based solder powder with the flux; (b) heating the mixture to a temperature of 60 to 100 °C; (c) cooling the mixture to room temperature; and (d) repeating steps (a) to (c) at least once. ​

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